1 00:00:00,000 --> 00:00:01,984 [SQUEAKING] 2 00:00:01,984 --> 00:00:04,464 [RUSTLING] 3 00:00:04,464 --> 00:00:06,448 [CLICKING] 4 00:00:16,110 --> 00:00:17,610 JEFFREY C. GROSSMAN: I want to start 5 00:00:17,610 --> 00:00:20,040 with this sort of big picture, all right. 6 00:00:20,040 --> 00:00:23,610 So we're going to kind of introduce energy storage, 7 00:00:23,610 --> 00:00:27,835 and then we'll talk about sort of why electrical storage is 8 00:00:27,835 --> 00:00:29,460 kind of a thing and important, and then 9 00:00:29,460 --> 00:00:31,128 we'll kind of go into batteries and then 10 00:00:31,128 --> 00:00:32,670 talk about the chemistry of batteries 11 00:00:32,670 --> 00:00:35,940 and throw in a couple of, why this matters. 12 00:00:35,940 --> 00:00:39,270 So if you think about this on a planetary scale, 13 00:00:39,270 --> 00:00:42,630 actually, the planet is kind of a storage device. 14 00:00:42,630 --> 00:00:46,050 It's an energy storage device for that thing over there, 15 00:00:46,050 --> 00:00:49,710 right, and so like if you think about all the energy flows that 16 00:00:49,710 --> 00:00:52,860 go on on planet Earth, well, then 17 00:00:52,860 --> 00:00:54,920 you've got-- there's a picture I like. 18 00:00:54,920 --> 00:00:58,038 It kind of shows you the different energy flows, right. 19 00:00:58,038 --> 00:01:00,330 You've got the sun, so you've got like solar radiation. 20 00:01:00,330 --> 00:01:03,240 You've got tides, there's the moon, you've got wind. 21 00:01:03,240 --> 00:01:05,190 You've got all these kinds of energy happening 22 00:01:05,190 --> 00:01:10,440 on the planet, all the way down to life happening, rock 23 00:01:10,440 --> 00:01:12,150 formation, right. 24 00:01:12,150 --> 00:01:14,100 And then sometimes those things, you know, 25 00:01:14,100 --> 00:01:19,690 rocks can form alloys over millions and millions of years. 26 00:01:19,690 --> 00:01:22,050 And the thing is, if you think about this, 27 00:01:22,050 --> 00:01:26,030 where you draw the line is somewhat arbitrary in a sense, 28 00:01:26,030 --> 00:01:26,530 right. 29 00:01:26,530 --> 00:01:28,410 It depends on our use. 30 00:01:28,410 --> 00:01:30,750 I mean, if you think about it, fossil fuels 31 00:01:30,750 --> 00:01:37,530 are actually a renewable source of energy on geological scales. 32 00:01:37,530 --> 00:01:39,640 The problem is that it's like 10, 33 00:01:39,640 --> 00:01:42,330 20, 30 million year old sunlight, right, 34 00:01:42,330 --> 00:01:45,420 and it'll happen again, but the question 35 00:01:45,420 --> 00:01:48,630 is how do we store energy on timescales that matter to us. 36 00:01:48,630 --> 00:01:50,370 And so you can draw this line and then 37 00:01:50,370 --> 00:01:54,330 think about what that means, and typically, most sort 38 00:01:54,330 --> 00:01:56,210 of energy storage needs are going 39 00:01:56,210 --> 00:01:59,260 to be around a year or less, right. 40 00:01:59,260 --> 00:02:04,710 OK, so now why electricity? 41 00:02:04,710 --> 00:02:06,390 Why electricity, right. 42 00:02:06,390 --> 00:02:11,220 So the thing is, electricity is more and more 43 00:02:11,220 --> 00:02:13,650 important in our lives, and if you 44 00:02:13,650 --> 00:02:15,930 look at just sort of like the major sectors, 45 00:02:15,930 --> 00:02:17,520 so you have the power generation, 46 00:02:17,520 --> 00:02:19,800 you have transportation, you have industry, 47 00:02:19,800 --> 00:02:22,830 you have buildings, and this is a plot of these sectors 48 00:02:22,830 --> 00:02:23,862 and the CO2 emissions. 49 00:02:23,862 --> 00:02:26,070 You can plot all sorts of things about these sectors. 50 00:02:26,070 --> 00:02:29,102 This is CO2 versus time. 51 00:02:29,102 --> 00:02:30,810 These are kind of the major contributors, 52 00:02:30,810 --> 00:02:34,650 but the thing is electricity, because of things 53 00:02:34,650 --> 00:02:37,770 that are happening as well, the opportunity-- either the use 54 00:02:37,770 --> 00:02:41,250 of electricity now like power to your home, 55 00:02:41,250 --> 00:02:43,680 or the opportunity to use it a lot more 56 00:02:43,680 --> 00:02:47,940 later, like transportation, that means that electricity has 57 00:02:47,940 --> 00:02:53,520 sort of about a 70% role, about a 70% opportunity of all 58 00:02:53,520 --> 00:02:54,510 of this. 59 00:02:54,510 --> 00:02:57,810 That's how much electricity matters here, 60 00:02:57,810 --> 00:02:59,400 but the thing is that electricity, 61 00:02:59,400 --> 00:03:01,380 as you know, in an electric car it's not 62 00:03:01,380 --> 00:03:04,140 going to be useful if you have to have it plugged 63 00:03:04,140 --> 00:03:05,160 in all the time, right. 64 00:03:05,160 --> 00:03:11,340 And so most of this 70%, most of this 70%, I want to emphasize, 65 00:03:11,340 --> 00:03:13,880 is not currently-- it's the potential 66 00:03:13,880 --> 00:03:17,560 for the electrification of our world that is happening. 67 00:03:17,560 --> 00:03:22,200 That's how much electricity will play a role, but most of it 68 00:03:22,200 --> 00:03:26,790 is useless unless you can store it, so storage of electricity 69 00:03:26,790 --> 00:03:30,400 is clearly really, really important. 70 00:03:30,400 --> 00:03:32,970 And so we get to sort of how do you think about storage 71 00:03:32,970 --> 00:03:35,820 technologies, and again, I just want to kind of gently 72 00:03:35,820 --> 00:03:39,600 introduce us to energy storage and we'll go into batteries. 73 00:03:39,600 --> 00:03:44,610 Now so the kind of plot that I'm showing you here, talking 74 00:03:44,610 --> 00:03:47,100 about Ashby plots, right, but this is actually 75 00:03:47,100 --> 00:03:47,830 a different kind. 76 00:03:47,830 --> 00:03:53,100 It's a special kind because it has to do with energy storage, 77 00:03:53,100 --> 00:04:03,060 and there's a guy who in the 1960s, David Ragone, he first-- 78 00:04:03,060 --> 00:04:04,350 And it's actually fascinating. 79 00:04:04,350 --> 00:04:07,710 He wrote a paper in 1968, a review 80 00:04:07,710 --> 00:04:13,255 of batteries for electric vehicles in 1968, right. 81 00:04:13,255 --> 00:04:14,880 And he's saying, how do I put-- there's 82 00:04:14,880 --> 00:04:16,149 all these possibilities. 83 00:04:16,149 --> 00:04:18,390 We want to electrify our transportation fleet, 84 00:04:18,390 --> 00:04:20,649 but which batteries make the most sense? 85 00:04:20,649 --> 00:04:24,360 And so he decided to plot them on these two axes, 86 00:04:24,360 --> 00:04:29,250 energy stored versus the power and that's a very common way. 87 00:04:29,250 --> 00:04:31,860 These are called Ragone plots now, 88 00:04:31,860 --> 00:04:35,940 so it's the energy versus power. 89 00:04:35,940 --> 00:04:39,493 And this is how you'll see a lot of discussions. 90 00:04:39,493 --> 00:04:41,910 If you look online and you're interested in energy storage 91 00:04:41,910 --> 00:04:44,850 as a field, you'll see a lot of plots 92 00:04:44,850 --> 00:04:50,230 like this where you got, OK, so energy is like watt hours, 93 00:04:50,230 --> 00:04:50,730 right. 94 00:04:50,730 --> 00:04:55,200 For example, this would be like watts times hours 95 00:04:55,200 --> 00:04:58,710 and this would be like the watts. 96 00:04:58,710 --> 00:05:03,323 So one of the nice things about plots like this, 97 00:05:03,323 --> 00:05:04,740 mostly, it's always on a log scale 98 00:05:04,740 --> 00:05:07,290 so you can stretch out and see all the different technologies 99 00:05:07,290 --> 00:05:09,000 on one plot, right. 100 00:05:09,000 --> 00:05:12,180 And one of the nice things about a plot is that this is energy, 101 00:05:12,180 --> 00:05:17,370 this is energy, and this is energy per time, right. 102 00:05:17,370 --> 00:05:21,150 And so that's energy per time times 103 00:05:21,150 --> 00:05:24,610 time, so we can have lots of fun with that. 104 00:05:24,610 --> 00:05:28,050 But so what that means if you think about it a little bit, 105 00:05:28,050 --> 00:05:30,900 if you plot energy storage technologies on plots 106 00:05:30,900 --> 00:05:37,710 like this, then these diagonal lines are one number of time. 107 00:05:37,710 --> 00:05:39,210 It's like if you had a given density 108 00:05:39,210 --> 00:05:41,850 and you're using it at a given rate, 109 00:05:41,850 --> 00:05:45,730 a giving power, then that's how long it would last. 110 00:05:45,730 --> 00:05:47,700 So these plots are really convenient. 111 00:05:47,700 --> 00:05:51,000 They're really convenient ways to compare energy technologies. 112 00:05:51,000 --> 00:05:55,020 OK, so those would be like, I've got energy storage technology 113 00:05:55,020 --> 00:05:57,930 and it's got this much density, this much power-- well, 114 00:05:57,930 --> 00:06:01,770 then it's going to last if I use it at that power for 41 days 115 00:06:01,770 --> 00:06:02,350 and so forth. 116 00:06:02,350 --> 00:06:05,470 Now the interesting, though, there's lots of stuff on here. 117 00:06:05,470 --> 00:06:08,490 Why don't I just want high and high? 118 00:06:08,490 --> 00:06:10,050 That sounds like a good thing, right, 119 00:06:10,050 --> 00:06:15,330 so shouldn't we be pumping water up hills all over the place? 120 00:06:15,330 --> 00:06:17,180 Well, obviously, if you think about it, 121 00:06:17,180 --> 00:06:19,393 you don't do that in your phone. 122 00:06:19,393 --> 00:06:21,060 You don't even do that in your backyard. 123 00:06:21,060 --> 00:06:22,930 You don't even do that in a town. 124 00:06:22,930 --> 00:06:23,430 Why? 125 00:06:23,430 --> 00:06:27,340 Because pumped hydro is extraordinarily limited. 126 00:06:27,340 --> 00:06:29,870 You have to do it at very large scales. 127 00:06:29,870 --> 00:06:32,490 It's very low energy density, right. 128 00:06:32,490 --> 00:06:35,310 It's geographically highly constrained. 129 00:06:35,310 --> 00:06:40,440 It is one of the oldest ways we have of storing energy, right. 130 00:06:40,440 --> 00:06:42,030 I'm just thinking of the waterwheel, 131 00:06:42,030 --> 00:06:45,930 but it's very constrained, so we can't use this in most 132 00:06:45,930 --> 00:06:48,630 applications, pumped hydro. 133 00:06:48,630 --> 00:06:51,300 But OK, oh, so this is compressed air. 134 00:06:51,300 --> 00:06:53,262 Compressed Air, CAES. 135 00:06:53,262 --> 00:06:53,970 That sounds good. 136 00:06:53,970 --> 00:06:56,280 That's got a whole lot of limitations as well. 137 00:06:56,280 --> 00:06:58,980 We've got, just to give you the abbreviations, 138 00:06:58,980 --> 00:07:03,228 Superconducting Magnetic Coils. 139 00:07:03,228 --> 00:07:05,020 Superconducters, right, just keep it going. 140 00:07:05,020 --> 00:07:06,450 And then you draw the [MUMBLES] and it just 141 00:07:06,450 --> 00:07:07,330 keeps going forever. 142 00:07:07,330 --> 00:07:10,590 It's a great battery, right, except for all the problems 143 00:07:10,590 --> 00:07:13,590 that it has and how much it costs, 144 00:07:13,590 --> 00:07:16,090 but it's a really cool concept and it's here. 145 00:07:16,090 --> 00:07:17,510 All of these things exist. 146 00:07:17,510 --> 00:07:19,020 All of these things exist. 147 00:07:19,020 --> 00:07:23,040 They all exist and they're all very interesting and important 148 00:07:23,040 --> 00:07:24,990 energy storage devices. 149 00:07:24,990 --> 00:07:28,080 They're interesting, important, electrical energy storage 150 00:07:28,080 --> 00:07:28,740 devices, right. 151 00:07:28,740 --> 00:07:31,110 So that's the main point. 152 00:07:31,110 --> 00:07:32,910 So like here, you know supercaps, 153 00:07:32,910 --> 00:07:35,340 you build up a lot of charge in a solid. 154 00:07:35,340 --> 00:07:36,750 Here you've got flywheels. 155 00:07:36,750 --> 00:07:39,010 Well, I'm just rotating something heavy really, 156 00:07:39,010 --> 00:07:40,110 really fast. 157 00:07:40,110 --> 00:07:41,730 I get worried about that. 158 00:07:41,730 --> 00:07:43,500 I don't want to be in that building, 159 00:07:43,500 --> 00:07:46,800 but they do build flywheel energy storage device where 160 00:07:46,800 --> 00:07:52,120 you slow it down and then you generate electricity from that. 161 00:07:52,120 --> 00:07:54,470 So these kinds of plots are really, really, 162 00:07:54,470 --> 00:08:00,480 really helpful for comparing one energy technology with another. 163 00:08:00,480 --> 00:08:04,810 Now, the thing is as I said, there's a whole list of these 164 00:08:04,810 --> 00:08:06,670 and it goes on and on. 165 00:08:06,670 --> 00:08:07,930 Oh, that's really hard to see. 166 00:08:07,930 --> 00:08:10,360 They've all got a lot of limitations, all right, 167 00:08:10,360 --> 00:08:14,680 and so capacitors have a low density. 168 00:08:14,680 --> 00:08:17,350 You can convert energy into some fuel 169 00:08:17,350 --> 00:08:18,790 and store it and then combust it. 170 00:08:18,790 --> 00:08:20,977 That's got low round-trip efficiency. 171 00:08:20,977 --> 00:08:23,560 This is what we're going to talk about today, electrochemical. 172 00:08:23,560 --> 00:08:25,480 There are challenges there too. 173 00:08:25,480 --> 00:08:28,090 Kinetic, pumped hydro, there's so many different ways 174 00:08:28,090 --> 00:08:31,000 of storing energy. 175 00:08:31,000 --> 00:08:33,820 The thing is there is an advantage 176 00:08:33,820 --> 00:08:38,120 that I want to mention about using electrochemistry. 177 00:08:38,120 --> 00:08:42,320 There is an advantage about using electrochemistry, 178 00:08:42,320 --> 00:08:43,299 and what is electro-- 179 00:08:43,299 --> 00:08:45,710 I just said the word electrochemistry. 180 00:08:45,710 --> 00:08:47,900 I should tell you what that is, right, 181 00:08:47,900 --> 00:09:03,990 and it's the relationship between electricity 182 00:09:03,990 --> 00:09:08,150 and chemical reactions. 183 00:09:12,370 --> 00:09:15,990 I love saving time, rxns. 184 00:09:15,990 --> 00:09:19,590 That's equal to electrochemistry. 185 00:09:19,590 --> 00:09:20,640 This isn't it. 186 00:09:20,640 --> 00:09:24,408 Now electrochemistry, OK. 187 00:09:24,408 --> 00:09:25,950 And so what you'll see is like things 188 00:09:25,950 --> 00:09:29,220 like electrochemical energy storage, 189 00:09:29,220 --> 00:09:34,090 and this isn't just one type of thing. 190 00:09:34,090 --> 00:09:37,090 It's not just one type of battery. 191 00:09:37,090 --> 00:09:38,980 It's not even just batteries. 192 00:09:38,980 --> 00:09:43,420 It's this broader definition, but we're going 193 00:09:43,420 --> 00:09:44,990 to talk about batteries today. 194 00:09:44,990 --> 00:09:48,740 Now, so there's something else that's really useful. 195 00:09:48,740 --> 00:09:51,280 So I mentioned we're getting to the point 196 00:09:51,280 --> 00:09:53,980 where we're electrifying everything. 197 00:09:53,980 --> 00:09:56,690 We need electricity almost everywhere, 198 00:09:56,690 --> 00:09:58,960 even in your combustion car. 199 00:09:58,960 --> 00:10:01,300 You need electricity a lot more than you used to, 200 00:10:01,300 --> 00:10:03,790 than 20 years ago. 201 00:10:03,790 --> 00:10:07,660 And so as we electrify our world, 202 00:10:07,660 --> 00:10:10,230 and then I said I've got to store that energy, 203 00:10:10,230 --> 00:10:13,360 you start to think about what Carnot did. 204 00:10:13,360 --> 00:10:16,360 Now I'm paraphrasing here, but this is basically 205 00:10:16,360 --> 00:10:18,730 what he said if you think about how it applies 206 00:10:18,730 --> 00:10:22,240 to this conversion, which is that the second law 207 00:10:22,240 --> 00:10:27,070 of thermodynamics makes you pay a penalty of energy 208 00:10:27,070 --> 00:10:31,150 if you convert it into heat and then back into electricity. 209 00:10:31,150 --> 00:10:34,000 Well, even if you just have heat in the first place 210 00:10:34,000 --> 00:10:36,720 and now you want to generate electricity from that, 211 00:10:36,720 --> 00:10:38,882 you're limited. 212 00:10:38,882 --> 00:10:40,340 We talked about this before, right, 213 00:10:40,340 --> 00:10:47,060 like that the energy density of gasoline, it's so high 214 00:10:47,060 --> 00:10:50,330 and it's such an amazing energy storage material because you 215 00:10:50,330 --> 00:10:53,870 can transport it safely, right. 216 00:10:53,870 --> 00:10:57,210 Yeah, but the thing is, I just gave you the example the car. 217 00:10:57,210 --> 00:10:58,450 You put it in your car. 218 00:10:58,450 --> 00:11:01,190 Does anybody know how efficient, how much of that energy 219 00:11:01,190 --> 00:11:07,200 your car actually uses to move percentage wise? 220 00:11:07,200 --> 00:11:09,190 Take a guess? 221 00:11:09,190 --> 00:11:11,310 Yeah, it's 10% to 20%, maybe, 10% to 20%. 222 00:11:11,310 --> 00:11:14,600 It depends on the car-- my car probably 5%. 223 00:11:14,600 --> 00:11:18,250 It's an old car. 224 00:11:18,250 --> 00:11:21,510 So most of that gasoline's energy is going into waste. 225 00:11:21,510 --> 00:11:22,290 Why? 226 00:11:22,290 --> 00:11:23,730 Carnot. 227 00:11:23,730 --> 00:11:25,410 Now this is not a thermodynamics class, 228 00:11:25,410 --> 00:11:27,210 but this comes into this so I wanted 229 00:11:27,210 --> 00:11:31,080 to mention Carnot and the fact that there is another way 230 00:11:31,080 --> 00:11:32,390 to do it. 231 00:11:32,390 --> 00:11:34,680 So you could do chemical reaction to heat. 232 00:11:34,680 --> 00:11:37,650 That's how we power most of our world today. 233 00:11:37,650 --> 00:11:40,780 A power plant gets up to a higher temperature 234 00:11:40,780 --> 00:11:43,320 so the penalty is less, but still most power plants, 235 00:11:43,320 --> 00:11:45,970 you lose about 50%. 236 00:11:45,970 --> 00:11:48,700 Most power plants at best are around 50% 237 00:11:48,700 --> 00:11:52,280 efficient in terms of converting the thermal energy 238 00:11:52,280 --> 00:11:53,900 into electrical energy. 239 00:11:53,900 --> 00:11:56,810 Yeah, but I can use a different way, 240 00:11:56,810 --> 00:11:58,130 and that's electrochemistry. 241 00:11:58,130 --> 00:12:00,380 And it's one of the reasons why electrochemical energy 242 00:12:00,380 --> 00:12:06,130 storage is so appealing, because you don't really pay a penalty. 243 00:12:06,130 --> 00:12:07,480 You don't really pay a penalty. 244 00:12:07,480 --> 00:12:12,360 I can go back and forth without the second law hurting me. 245 00:12:12,360 --> 00:12:17,030 So I want to mention something about Carnot, 246 00:12:17,030 --> 00:12:21,320 about the second law, and again, this is not a class on thermo, 247 00:12:21,320 --> 00:12:23,330 but the second law involves entropy 248 00:12:23,330 --> 00:12:26,990 so I had to say something, especially because it's 249 00:12:26,990 --> 00:12:29,960 in Averill, right, and that's your textbook that you're 250 00:12:29,960 --> 00:12:34,362 diligently reading every day, and there it is. 251 00:12:34,362 --> 00:12:36,320 And by the way, Averill has a beautiful chapter 252 00:12:36,320 --> 00:12:37,860 on batteries, chapter 19. 253 00:12:37,860 --> 00:12:39,350 I'm sure you know. 254 00:12:39,350 --> 00:12:40,858 It's really well written. 255 00:12:40,858 --> 00:12:42,650 This is what he says about entropy, though, 256 00:12:42,650 --> 00:12:46,010 and for now we can state that entropy 257 00:12:46,010 --> 00:12:48,320 is a thermodynamic property of all substances that 258 00:12:48,320 --> 00:12:51,750 is proportional to their degree of disorder. 259 00:12:51,750 --> 00:12:56,945 Averill, such a good book, but let me ask you guys a question. 260 00:13:01,270 --> 00:13:03,920 So people think about entropy as disorder 261 00:13:03,920 --> 00:13:08,510 and they think about entropy as sort of more disorder. 262 00:13:08,510 --> 00:13:10,820 Let me ask you, which one of these 263 00:13:10,820 --> 00:13:14,180 has a higher entropy, the one on the left 264 00:13:14,180 --> 00:13:15,180 or the one on the right? 265 00:13:19,685 --> 00:13:21,920 So how many of you think the one on the left 266 00:13:21,920 --> 00:13:23,960 has a higher entropy? 267 00:13:23,960 --> 00:13:27,930 How many of you think it's the one on the right? 268 00:13:27,930 --> 00:13:31,730 So the thing is it's the one on the left. 269 00:13:31,730 --> 00:13:33,140 Yeah, right. 270 00:13:33,140 --> 00:13:36,620 I love that you guys are blown away. 271 00:13:36,620 --> 00:13:37,340 Why? 272 00:13:37,340 --> 00:13:40,430 Because entropy is not about smoothness and it's 273 00:13:40,430 --> 00:13:41,930 not about disorder. 274 00:13:41,930 --> 00:13:44,540 That is wrong. 275 00:13:44,540 --> 00:13:48,370 Entropy is about accessibility to states. 276 00:13:48,370 --> 00:13:53,080 It's about how many states you have to be in. 277 00:13:53,080 --> 00:13:56,950 Now, that can appear to be like disorder, right, 278 00:13:56,950 --> 00:14:00,580 but a messier room does not have higher entropy, 279 00:14:00,580 --> 00:14:02,500 and in this case, it's just simply 280 00:14:02,500 --> 00:14:04,090 the rules of the algorithm. 281 00:14:04,090 --> 00:14:07,780 I have rules here about the dots being able to touch each other. 282 00:14:07,780 --> 00:14:10,300 They are randomly selected but with the constraint that they 283 00:14:10,300 --> 00:14:12,680 cannot touch each other. 284 00:14:12,680 --> 00:14:16,060 That means that those dots had fewer possibilities. 285 00:14:16,060 --> 00:14:18,490 They had fewer states that they could be in. 286 00:14:18,490 --> 00:14:21,017 This system has much higher entropy. 287 00:14:21,017 --> 00:14:22,350 It's about the number of states. 288 00:14:22,350 --> 00:14:23,730 I just want to make that-- 289 00:14:23,730 --> 00:14:25,680 again, this is not the topic of this class, 290 00:14:25,680 --> 00:14:28,920 but I've got to make my case about entropy when I can. 291 00:14:28,920 --> 00:14:31,860 And I brought up Carnot, so there you go. 292 00:14:31,860 --> 00:14:33,750 Entropy is not just disorder. 293 00:14:33,750 --> 00:14:35,370 Now OK, so we're back to batteries. 294 00:14:35,370 --> 00:14:38,010 Now so electrochemistry, there's a lot 295 00:14:38,010 --> 00:14:42,490 of reasons why electrochemical storage is-- 296 00:14:42,490 --> 00:14:43,740 here's the chart again, right. 297 00:14:43,740 --> 00:14:44,880 It's this one here. 298 00:14:44,880 --> 00:14:47,128 You see that, electrochemical batteries, all right, 299 00:14:47,128 --> 00:14:48,420 that we're going to talk about. 300 00:14:48,420 --> 00:14:51,780 There's a lot of reasons why this is so appealing. 301 00:14:51,780 --> 00:14:54,970 No penalty on the second law is one of them. 302 00:14:54,970 --> 00:14:57,930 You can have transport easily, right. 303 00:14:57,930 --> 00:14:59,000 We drive electric cars. 304 00:14:59,000 --> 00:14:59,550 We see that. 305 00:14:59,550 --> 00:15:01,650 No pollution at the point of use-- pollution 306 00:15:01,650 --> 00:15:05,993 can be focused at the point of production. 307 00:15:05,993 --> 00:15:07,410 Also, the batteries can be charged 308 00:15:07,410 --> 00:15:11,543 by renewable technologies like solar wind, 309 00:15:11,543 --> 00:15:12,960 and they're very highly efficient. 310 00:15:12,960 --> 00:15:17,070 Electric cars, for example, have a very high efficiency 311 00:15:17,070 --> 00:15:19,610 depending on the car, but upwards of 90% 312 00:15:19,610 --> 00:15:22,110 in terms of converting that electrical energy back 313 00:15:22,110 --> 00:15:23,100 and forth. 314 00:15:23,100 --> 00:15:25,850 The metrics that matter, I wrote a couple of them here, 315 00:15:25,850 --> 00:15:27,930 all right, watts, hours. 316 00:15:27,930 --> 00:15:30,750 These are the things that matter in batteries, 317 00:15:30,750 --> 00:15:32,800 but so many other things matter, and this is why 318 00:15:32,800 --> 00:15:34,050 this is a complicated problem. 319 00:15:34,050 --> 00:15:38,970 And it's also why batteries are not in any way 320 00:15:38,970 --> 00:15:40,360 a one-size-fits-all. 321 00:15:40,360 --> 00:15:44,820 I mean, you know that from like AAs and AAAs and 9-volt, 322 00:15:44,820 --> 00:15:46,980 but it's so much more than that, because it's 323 00:15:46,980 --> 00:15:51,000 about the application change not going from your computer 324 00:15:51,000 --> 00:15:58,170 to your phone but going from your car to your phone 325 00:15:58,170 --> 00:16:00,420 to a house to a grid. 326 00:16:00,420 --> 00:16:03,870 And so the needs are all going to be different, 327 00:16:03,870 --> 00:16:06,540 and then which ones of these things you care about 328 00:16:06,540 --> 00:16:09,203 is going to depend on what chemistry you think about. 329 00:16:09,203 --> 00:16:10,620 It all comes down to the chemistry 330 00:16:10,620 --> 00:16:11,670 as we're going to see. 331 00:16:11,670 --> 00:16:14,590 It's all about the chemistry. 332 00:16:14,590 --> 00:16:16,090 And just to put a few numbers down, 333 00:16:16,090 --> 00:16:18,430 the cell phone has a few watts of power. 334 00:16:18,430 --> 00:16:20,250 Light bulb is 10 to 100. 335 00:16:20,250 --> 00:16:24,800 A AAA battery has 1.5 watt hours of storage, 336 00:16:24,800 --> 00:16:28,030 all right, so that's how much energy is inside 337 00:16:28,030 --> 00:16:29,710 of a AAA battery. 338 00:16:29,710 --> 00:16:32,560 Needed to drive a car 200 miles, 100 kilowatt hours. 339 00:16:32,560 --> 00:16:34,710 It's just fun to think about these things, right. 340 00:16:34,710 --> 00:16:36,085 Powering your house, 40 kilowatts 341 00:16:36,085 --> 00:16:39,880 max, depending on how many AC units you're running. 342 00:16:39,880 --> 00:16:44,750 The world is this many watts as of a few years ago. 343 00:16:44,750 --> 00:16:47,560 So if you had, I think it's something 344 00:16:47,560 --> 00:16:50,140 like 20,000 billion AAA batteries, 345 00:16:50,140 --> 00:16:53,393 you could run the world for an hour-ish, something like that. 346 00:16:53,393 --> 00:16:55,060 These numbers are just fun to play with, 347 00:16:55,060 --> 00:16:57,020 so I wanted to put a few examples down. 348 00:16:57,020 --> 00:16:58,510 So where'd it all begin? 349 00:16:58,510 --> 00:17:02,450 It all began with an argument. 350 00:17:02,450 --> 00:17:06,260 It all began with this beautiful argument 351 00:17:06,260 --> 00:17:08,510 that I have to tell you because it's really 352 00:17:08,510 --> 00:17:10,400 a cool piece of history. 353 00:17:10,400 --> 00:17:12,589 And it took place in Italy. 354 00:17:12,589 --> 00:17:16,849 And it was Galvani who was a physiologist, 355 00:17:16,849 --> 00:17:22,140 and he really loved the topic of why animals move, right. 356 00:17:22,140 --> 00:17:24,440 So what is motion? 357 00:17:24,440 --> 00:17:27,920 How is it that animals are moving? 358 00:17:27,920 --> 00:17:29,660 You know, how am I moving my muscles? 359 00:17:29,660 --> 00:17:31,070 How is anything moving? 360 00:17:31,070 --> 00:17:33,710 Well, there had been theories about this 361 00:17:33,710 --> 00:17:35,060 going all the way back. 362 00:17:35,060 --> 00:17:39,980 You remember Socrates and Plato, the elements, right, 363 00:17:39,980 --> 00:17:41,240 and aether? 364 00:17:41,240 --> 00:17:45,720 There were similar theories for motion of the human body. 365 00:17:45,720 --> 00:17:50,000 In fact, the word pneuma was used 366 00:17:50,000 --> 00:17:53,900 to describe the essence that goes through all living things 367 00:17:53,900 --> 00:17:55,480 that allows them to move. 368 00:17:55,480 --> 00:17:57,620 Well, Galvani didn't like that and he 369 00:17:57,620 --> 00:18:00,320 wanted something more concrete, and so he was really 370 00:18:00,320 --> 00:18:02,000 trying to make a connection, especially 371 00:18:02,000 --> 00:18:05,213 between things that move and electricity. 372 00:18:08,110 --> 00:18:10,930 Now, it was difficult. There wasn't like a constant source. 373 00:18:10,930 --> 00:18:14,340 So you had electric generators in your lab at the time, 374 00:18:14,340 --> 00:18:18,180 but Galvani wanted to go big, so he hooked up his lightning rod 375 00:18:18,180 --> 00:18:19,750 to a frog. 376 00:18:19,750 --> 00:18:22,530 The frog was not alive. 377 00:18:22,530 --> 00:18:24,690 Well, the frog was not alive, seriously, 378 00:18:24,690 --> 00:18:26,790 because then you'll see why-- 379 00:18:26,790 --> 00:18:29,140 at least I don't think so. 380 00:18:29,140 --> 00:18:30,130 I really hope not. 381 00:18:30,130 --> 00:18:32,380 Now I'm thinking about it, I'm getting a little bummed 382 00:18:32,380 --> 00:18:35,570 honestly, but I don't think they were alive. 383 00:18:35,570 --> 00:18:37,080 That doesn't look alive. 384 00:18:37,080 --> 00:18:39,810 So he hooked them up to lightning rods and he watched 385 00:18:39,810 --> 00:18:42,660 and he waited as the storm's coming, and he's like, 386 00:18:42,660 --> 00:18:45,760 the lightning rod hits and he hooked him up to some metals, 387 00:18:45,760 --> 00:18:48,110 and the frog went crazy. 388 00:18:48,110 --> 00:18:51,150 It was like, ah-ha, motion, electricity. 389 00:18:51,150 --> 00:18:52,710 He'd been jolting them in his lab 390 00:18:52,710 --> 00:18:56,400 with his own electric generator, but he wanted to go big, 391 00:18:56,400 --> 00:18:58,650 and also, they didn't know. 392 00:18:58,650 --> 00:19:04,207 They didn't know at the time what electricity was, right, 393 00:19:04,207 --> 00:19:06,540 so they didn't know if the electricity that he generated 394 00:19:06,540 --> 00:19:08,850 in his own thing was the same as the electricity that 395 00:19:08,850 --> 00:19:09,600 came from the sky. 396 00:19:09,600 --> 00:19:14,870 He saw that you get the same result. The frog still moved. 397 00:19:14,870 --> 00:19:19,770 So Galvani said the motion of a frog, 398 00:19:19,770 --> 00:19:22,980 and all motion of all living creatures, 399 00:19:22,980 --> 00:19:26,070 generates electricity. 400 00:19:26,070 --> 00:19:26,940 That's what he said. 401 00:19:26,940 --> 00:19:29,680 He deduced that the motion itself 402 00:19:29,680 --> 00:19:32,330 is something that generates electricity. 403 00:19:32,330 --> 00:19:35,220 This is a really cool little article about this debate, 404 00:19:35,220 --> 00:19:38,880 because in Galvani's case, if you have two metal wires 405 00:19:38,880 --> 00:19:41,670 hooked up to a frog, like we say, if you close the loop, 406 00:19:41,670 --> 00:19:44,190 then what he said is that the charge that was already 407 00:19:44,190 --> 00:19:47,160 in there moves around the loop and back 408 00:19:47,160 --> 00:19:49,490 and makes the leg move. 409 00:19:49,490 --> 00:19:52,620 Volta got really interested in this and he said, you know, 410 00:19:52,620 --> 00:19:53,490 let me study this. 411 00:19:53,490 --> 00:19:58,350 He was a physicist at the time and he said, 412 00:19:58,350 --> 00:20:00,300 this looks fascinating, let me study it-- 413 00:20:00,300 --> 00:20:02,850 but he said, you know, why do you keep 414 00:20:02,850 --> 00:20:03,975 using two different metals? 415 00:20:07,280 --> 00:20:11,653 So I think this is about the metals, not the frog, 416 00:20:11,653 --> 00:20:13,320 and they had a big huge argument, right. 417 00:20:13,320 --> 00:20:15,840 So this is Volta's picture, is that it's 418 00:20:15,840 --> 00:20:18,060 when you connect two different metals that you 419 00:20:18,060 --> 00:20:22,090 get a charge flowing through the frog. 420 00:20:22,090 --> 00:20:24,262 Volta, I think, as many of you know, 421 00:20:24,262 --> 00:20:28,370 went on to win that argument, and we 422 00:20:28,370 --> 00:20:31,070 have the volt named after him, and he also 423 00:20:31,070 --> 00:20:36,490 created the first stable battery, the voltaic pile. 424 00:20:36,490 --> 00:20:40,730 Galvani on the other hand really opened the doors to the idea 425 00:20:40,730 --> 00:20:44,180 that we have electricity in our bodies, which is pretty cool. 426 00:20:44,180 --> 00:20:46,730 He also is the reason why the story of Frankenstein 427 00:20:46,730 --> 00:20:48,350 was written. 428 00:20:48,350 --> 00:20:54,290 It's actually true because they went around and took 429 00:20:54,290 --> 00:20:57,890 all sorts of things and electrocuted them and showed 430 00:20:57,890 --> 00:21:00,800 that they moved, and often they weren't alive, 431 00:21:00,800 --> 00:21:03,170 and so Mary Shelley, I think, saw that. 432 00:21:03,170 --> 00:21:06,110 You went around like the countryside shocking people, 433 00:21:06,110 --> 00:21:09,770 and I actually meant that as like not literally, 434 00:21:09,770 --> 00:21:14,553 but just shocking them by what he's doing. 435 00:21:14,553 --> 00:21:16,220 And I don't think they ever used humans, 436 00:21:16,220 --> 00:21:19,230 but still, people's imaginations and so forth, 437 00:21:19,230 --> 00:21:21,060 and it was quite a thing. 438 00:21:21,060 --> 00:21:23,477 OK, very interesting story. 439 00:21:23,477 --> 00:21:24,560 Now, why does this matter? 440 00:21:24,560 --> 00:21:25,810 I've got two why this matters. 441 00:21:25,810 --> 00:21:29,210 Today my first one is on a personal scale, smaller scale, 442 00:21:29,210 --> 00:21:32,570 and then my next one is on a grid scale. 443 00:21:32,570 --> 00:21:35,005 So this is called a little sun. 444 00:21:35,005 --> 00:21:36,380 There's over a billion people who 445 00:21:36,380 --> 00:21:39,050 can't read at night because there's 446 00:21:39,050 --> 00:21:42,225 no access to electricity, and of course, 447 00:21:42,225 --> 00:21:43,850 a lot of the studying that you could do 448 00:21:43,850 --> 00:21:45,110 would be at night, right. 449 00:21:45,110 --> 00:21:47,000 So this is a really cool program. 450 00:21:47,000 --> 00:21:47,900 Why does this work? 451 00:21:47,900 --> 00:21:49,483 This is a solar cell but this wouldn't 452 00:21:49,483 --> 00:21:51,890 work unless you could store the electricity, right, 453 00:21:51,890 --> 00:21:54,340 so I wanted to make you guys aware of Little Sun. 454 00:21:54,340 --> 00:21:57,290 You just press this and you can read at night, right. 455 00:21:57,290 --> 00:21:59,330 This is already making a big difference 456 00:21:59,330 --> 00:22:03,520 in millions of people's lives. 457 00:22:03,520 --> 00:22:05,050 That doesn't happen unless you've 458 00:22:05,050 --> 00:22:07,890 got electrochemical energy storage, 459 00:22:07,890 --> 00:22:12,960 right, and there's some stats up here. 460 00:22:12,960 --> 00:22:15,160 $25 billion liters of kerosene are 461 00:22:15,160 --> 00:22:19,060 used to meet the basic lighting needs in a lot of these places. 462 00:22:19,060 --> 00:22:23,950 That releases tremendous amounts of toxic fumes, 463 00:22:23,950 --> 00:22:27,740 and you can make a huge difference, 464 00:22:27,740 --> 00:22:31,240 But you know, it's sort of the same as cooking, right. 465 00:22:31,240 --> 00:22:35,080 So wood fire cooking is a huge problem. 466 00:22:35,080 --> 00:22:37,630 So the challenge is, but you don't cook. 467 00:22:37,630 --> 00:22:40,000 If you have a solar cooker, that's 468 00:22:40,000 --> 00:22:42,970 great except that most people don't cook during the day. 469 00:22:42,970 --> 00:22:45,710 They cook at night or in the morning, right. 470 00:22:45,710 --> 00:22:48,610 And so you've got to store energy 471 00:22:48,610 --> 00:22:51,490 to make these things actually useful, right, 472 00:22:51,490 --> 00:22:53,410 and I really like this program so I 473 00:22:53,410 --> 00:22:55,600 wanted to make that one of my, why this matters. 474 00:22:55,600 --> 00:22:58,060 And we'll go big on the next one, 475 00:22:58,060 --> 00:22:59,690 but let's get to the chemistry. 476 00:22:59,690 --> 00:23:02,230 So what happens in a battery? 477 00:23:02,230 --> 00:23:05,020 The best way to understand this is with a classic example 478 00:23:05,020 --> 00:23:06,070 of two different metals. 479 00:23:06,070 --> 00:23:08,310 It's Volta's two different metals. 480 00:23:08,310 --> 00:23:10,040 Volta did lots of metals. 481 00:23:10,040 --> 00:23:11,560 That's what he did. 482 00:23:11,560 --> 00:23:16,540 And he showed that the frog moved with most of them, 483 00:23:16,540 --> 00:23:17,410 so it's the metals. 484 00:23:17,410 --> 00:23:22,100 So let's take these two classic metals and show what happens. 485 00:23:22,100 --> 00:23:25,300 You've got copper and you've got zinc. 486 00:23:25,300 --> 00:23:27,400 Now, in this case, I'm just going to have a zinc. 487 00:23:27,400 --> 00:23:30,640 This is the zinc piece of metal, and this is a piece of zinc, 488 00:23:30,640 --> 00:23:35,230 and I put it in a solution of copper ions. 489 00:23:35,230 --> 00:23:38,270 And so in this case, what do we have? 490 00:23:38,270 --> 00:23:39,730 Let's write this down. 491 00:23:39,730 --> 00:23:48,490 In this case, I've got zinc solid. 492 00:23:51,040 --> 00:23:53,680 Well, before I write this down, let's write down 493 00:23:53,680 --> 00:23:55,330 what's in the solution. 494 00:23:55,330 --> 00:23:58,990 The solution is copper sulfate and this goes to everything 495 00:23:58,990 --> 00:24:00,860 that we've been talking about. 496 00:24:00,860 --> 00:24:03,850 So I've got a solution, a beaker, 497 00:24:03,850 --> 00:24:06,940 that has copper ions in it. 498 00:24:06,940 --> 00:24:07,823 How much? 499 00:24:07,823 --> 00:24:08,365 I don't know. 500 00:24:08,365 --> 00:24:10,780 Look up the K sp, right? 501 00:24:10,780 --> 00:24:12,910 Now we know how to do that. 502 00:24:12,910 --> 00:24:16,510 So 2 minus in solution. 503 00:24:16,510 --> 00:24:20,200 So you put some of this copper sulfate powder in that beaker. 504 00:24:20,200 --> 00:24:22,630 It turns blue and it gives you these ions that 505 00:24:22,630 --> 00:24:26,120 are dissolved in solution, and then you put a piece of zinc 506 00:24:26,120 --> 00:24:26,620 in there. 507 00:24:30,040 --> 00:24:37,470 So what happens is there is a transfer of electrons, right. 508 00:24:37,470 --> 00:24:39,438 Now we talked a lot about electrons. 509 00:24:39,438 --> 00:24:41,230 We're talking about transfers of electrons. 510 00:24:41,230 --> 00:24:42,688 I mean, just think about it, right. 511 00:24:42,688 --> 00:24:46,170 We went from H, right, like this. 512 00:24:46,170 --> 00:24:50,820 Look at that, right, the bonding and then we did this, OK. 513 00:24:50,820 --> 00:24:51,360 Here we go. 514 00:24:51,360 --> 00:24:55,020 It's a little bit less sharing but still. 515 00:24:55,020 --> 00:25:01,020 All right, and then we did this, where it's like, OK, 516 00:25:01,020 --> 00:25:02,530 there's almost nothing there. 517 00:25:02,530 --> 00:25:03,280 It all went there. 518 00:25:03,280 --> 00:25:06,850 These are where my electrons are, all right. 519 00:25:06,850 --> 00:25:13,220 Well, then we put this in water and we got this, OK. 520 00:25:13,220 --> 00:25:14,930 And we got them sort of separated 521 00:25:14,930 --> 00:25:18,440 and this one just broke off with its electron, 522 00:25:18,440 --> 00:25:20,290 leaving a positive charge behind. 523 00:25:20,290 --> 00:25:21,530 So we've done all this. 524 00:25:21,530 --> 00:25:24,690 We know this, all right. 525 00:25:24,690 --> 00:25:26,470 So what's happening here is special 526 00:25:26,470 --> 00:25:30,310 because what's happening here is a trading of electrons. 527 00:25:30,310 --> 00:25:32,860 You see, in all the bonding that we've done, 528 00:25:32,860 --> 00:25:35,500 we're talking about how electrons share in bonds 529 00:25:35,500 --> 00:25:38,040 and then these things break apart, 530 00:25:38,040 --> 00:25:41,160 but now I'm going to do reactions that trade them. 531 00:25:41,160 --> 00:25:42,990 That's electrochemistry. 532 00:25:42,990 --> 00:25:44,490 That's electrochemistry, and what 533 00:25:44,490 --> 00:25:47,520 happens when I put that zinc strip into that solution 534 00:25:47,520 --> 00:25:48,420 is this. 535 00:25:48,420 --> 00:25:55,690 The zinc that goes into solution is 2 plus and 2 electrons. 536 00:25:55,690 --> 00:25:59,730 And the copper in the solution plates 537 00:25:59,730 --> 00:26:03,630 onto the zinc, plus those 2 electrons 538 00:26:03,630 --> 00:26:07,110 goes to copper like that. 539 00:26:07,110 --> 00:26:10,560 And if you look at the full reaction, 540 00:26:10,560 --> 00:26:16,200 the full reaction would be then zinc solid plus copper 541 00:26:16,200 --> 00:26:25,760 2 plus in solution goes to zinc 2 plus in solution plus copper 542 00:26:25,760 --> 00:26:26,840 solid. 543 00:26:26,840 --> 00:26:27,890 That's the trading. 544 00:26:27,890 --> 00:26:31,250 Now I like writing it like this because you really 545 00:26:31,250 --> 00:26:34,730 see explicitly the gaining and losing of electrons. 546 00:26:34,730 --> 00:26:37,280 Oh, those have words associated with them, 547 00:26:37,280 --> 00:26:39,230 gaining and losing electrons. 548 00:26:39,230 --> 00:26:40,940 But this is the reaction that we're 549 00:26:40,940 --> 00:26:44,720 kind of used to, right, so this is just the same thing. 550 00:26:44,720 --> 00:26:47,000 It's what happens, right. 551 00:26:47,000 --> 00:26:47,880 It's what happens. 552 00:26:47,880 --> 00:26:50,820 It's a trade of electrons. 553 00:26:50,820 --> 00:26:54,200 Now it turns out that when something loses 554 00:26:54,200 --> 00:26:58,680 electrons like that we call it oxidation, 555 00:26:58,680 --> 00:27:01,740 and when something gains electrons 556 00:27:01,740 --> 00:27:03,225 we call this reduction. 557 00:27:05,970 --> 00:27:10,810 And so when two different materials-- 558 00:27:10,810 --> 00:27:14,040 in this case, these two metals-- trade electrons and one of them 559 00:27:14,040 --> 00:27:16,360 is oxidized and one of them is reduced, 560 00:27:16,360 --> 00:27:17,690 that's also got a name. 561 00:27:17,690 --> 00:27:19,450 It's called a redox couple. 562 00:27:19,450 --> 00:27:23,380 Those are a redox couple, redox, redox, right. 563 00:27:26,680 --> 00:27:34,380 So these are a redox couple, is what they're called when 564 00:27:34,380 --> 00:27:36,210 you trade electrons like this. 565 00:27:36,210 --> 00:27:38,620 OK, so what's happening? 566 00:27:38,620 --> 00:27:44,690 What's happening is at the surface of the zinc, 567 00:27:44,690 --> 00:27:47,630 I see these copper ions in solution. 568 00:27:47,630 --> 00:27:52,760 And it's like, well, if I gave you two electrons, 569 00:27:52,760 --> 00:27:58,610 then you'd be able to become a copper solid, right. 570 00:27:58,610 --> 00:28:02,540 So if I give you two electrons, you're a copper solid, 571 00:28:02,540 --> 00:28:05,660 but now if I lose two electrons as a zinc atom, 572 00:28:05,660 --> 00:28:07,550 I'm a zinc 2 plus. 573 00:28:07,550 --> 00:28:09,020 That's this. 574 00:28:09,020 --> 00:28:11,280 That's just this, right. 575 00:28:11,280 --> 00:28:12,880 Why does that happen? 576 00:28:12,880 --> 00:28:15,630 Well, we'll get to that, right, but that's what's happening. 577 00:28:15,630 --> 00:28:18,690 So a zinc atom at the surface, all 578 00:28:18,690 --> 00:28:21,490 right, a zinc atom at the service sees a copper 2 plus 579 00:28:21,490 --> 00:28:22,997 and it says here, have 2 electrons. 580 00:28:22,997 --> 00:28:24,580 Oh, and then it's like, wait a second. 581 00:28:24,580 --> 00:28:25,663 I gave two electrons away. 582 00:28:25,663 --> 00:28:28,570 I've got to go into solution. 583 00:28:28,570 --> 00:28:31,060 And that's exactly what you see over here, right. 584 00:28:31,060 --> 00:28:35,020 The copper is plating the zinc and the zinc 585 00:28:35,020 --> 00:28:37,270 is coming off of the strip. 586 00:28:37,270 --> 00:28:38,320 They're doing this. 587 00:28:38,320 --> 00:28:40,970 All right, why is that happening? 588 00:28:40,970 --> 00:28:43,420 Because if you put that strip in there and the thing 589 00:28:43,420 --> 00:28:46,270 just heats up, this is exothermic. 590 00:28:46,270 --> 00:28:48,250 That means that this reaction will go. 591 00:28:48,250 --> 00:28:50,260 This is spontaneous. 592 00:28:50,260 --> 00:28:52,030 This is spontaneous. 593 00:28:52,030 --> 00:28:54,410 Where can I write that? 594 00:28:54,410 --> 00:28:56,300 Nowhere. 595 00:28:56,300 --> 00:28:57,170 Spontaneous. 596 00:29:03,900 --> 00:29:07,970 It didn't have to be, as we'll see, but this one is. 597 00:29:07,970 --> 00:29:12,280 But all that's happening is you're going down in energy. 598 00:29:12,280 --> 00:29:14,570 You're giving energy away and you're 599 00:29:14,570 --> 00:29:15,720 heating up the environment. 600 00:29:15,720 --> 00:29:18,420 Now the question is, how can I not let that happen? 601 00:29:18,420 --> 00:29:20,420 How can I stop the heating from happen 602 00:29:20,420 --> 00:29:23,720 and instead take advantage of this electron trading 603 00:29:23,720 --> 00:29:24,980 to do work? 604 00:29:24,980 --> 00:29:26,390 That's what a battery is. 605 00:29:26,390 --> 00:29:27,560 That's what a battery is. 606 00:29:27,560 --> 00:29:29,750 It's taking advantage of this. 607 00:29:29,750 --> 00:29:31,910 And really what it comes down to is just 608 00:29:31,910 --> 00:29:34,250 a different construction of the device. 609 00:29:34,250 --> 00:29:35,010 It's this. 610 00:29:35,010 --> 00:29:35,510 The 611 00:29:35,510 --> 00:29:38,690 Fundamentals of a battery is this kind of thing, 612 00:29:38,690 --> 00:29:41,840 but now instead of allowing this plating to happen, 613 00:29:41,840 --> 00:29:44,190 I'm going to separate that and I'm 614 00:29:44,190 --> 00:29:46,890 going to construct it in such a way 615 00:29:46,890 --> 00:29:51,180 that those electrons get traded through some wire 616 00:29:51,180 --> 00:29:53,100 that I can do work with, OK. 617 00:29:53,100 --> 00:29:57,970 So for example-- where is it? 618 00:29:57,970 --> 00:30:00,160 OK, maybe not for example. 619 00:30:00,160 --> 00:30:06,840 Maybe for example, maybe I need to turn this on and off. 620 00:30:06,840 --> 00:30:07,660 Here we go. 621 00:30:07,660 --> 00:30:10,050 This is the picture that Averill gives for the battery. 622 00:30:10,050 --> 00:30:12,750 So what you saw wasn't a battery because I wasn't stopping 623 00:30:12,750 --> 00:30:14,603 the electron flow and doing anything, 624 00:30:14,603 --> 00:30:16,020 but if you construct it like this, 625 00:30:16,020 --> 00:30:17,792 is called a galvanic cell. 626 00:30:17,792 --> 00:30:19,500 All right, if you construct it like this, 627 00:30:19,500 --> 00:30:22,990 now I can do work with that electron trade. 628 00:30:22,990 --> 00:30:24,750 I can do work with the electron trade. 629 00:30:24,750 --> 00:30:25,720 That's the difference. 630 00:30:25,720 --> 00:30:26,890 So let's go through this. 631 00:30:26,890 --> 00:30:29,010 So on the left, so what did I do? 632 00:30:29,010 --> 00:30:32,340 Well, I got my zinc strip but now I've got a copper strip. 633 00:30:35,060 --> 00:30:36,940 Just trying to see. 634 00:30:36,940 --> 00:30:39,340 OK, I've got a copper strip over here. 635 00:30:39,340 --> 00:30:41,740 I've got a zinc strip over here. 636 00:30:41,740 --> 00:30:44,050 But I'm putting the zinc not into the copper 637 00:30:44,050 --> 00:30:47,110 directly where I just short it and the whole thing 638 00:30:47,110 --> 00:30:47,830 just heats up. 639 00:30:47,830 --> 00:30:51,310 Instead, I'm putting the zinc into a solution of zinc ions. 640 00:30:51,310 --> 00:30:52,450 Look at that. 641 00:30:52,450 --> 00:30:56,340 Zinc has zinc ions in solution, right. 642 00:30:56,340 --> 00:31:00,530 Now, copper, copper is in a solution of copper ions. 643 00:31:00,530 --> 00:31:02,200 So these are now the two beakers. 644 00:31:02,200 --> 00:31:04,570 On the left I've got zinc nitrate. 645 00:31:04,570 --> 00:31:07,300 In this case it's a nitrate, not a sulfate. 646 00:31:07,300 --> 00:31:08,690 It doesn't matter. 647 00:31:08,690 --> 00:31:10,690 The whole point of the solution is 648 00:31:10,690 --> 00:31:13,090 that I get these ions in a beaker. 649 00:31:13,090 --> 00:31:15,010 Got to get these ions in a beaker, 650 00:31:15,010 --> 00:31:19,455 so you've got the copper ions in a beaker on the right 651 00:31:19,455 --> 00:31:21,580 with the copper solid and you've got the zinc ions. 652 00:31:21,580 --> 00:31:22,955 So let's look at what's happening 653 00:31:22,955 --> 00:31:25,390 and blow up those different sides, right. 654 00:31:25,390 --> 00:31:27,820 So at the anode, it's called the anode 655 00:31:27,820 --> 00:31:30,820 because it's where the charge comes from. 656 00:31:30,820 --> 00:31:31,900 It's called the anode. 657 00:31:31,900 --> 00:31:32,650 What's happening? 658 00:31:32,650 --> 00:31:36,380 Well, what's happening is what I just showed you. 659 00:31:36,380 --> 00:31:39,920 The zinc is leaving the solid. 660 00:31:39,920 --> 00:31:44,355 The zinc is leaving the solid and it's becoming 2 plus. 661 00:31:44,355 --> 00:31:45,230 It's becoming 2 plus. 662 00:31:49,825 --> 00:31:52,200 But the thing is that now, you've got to be careful here. 663 00:31:52,200 --> 00:31:55,510 So the zinc is becoming 2 plus. 664 00:31:55,510 --> 00:31:58,810 What about those two electrons? 665 00:31:58,810 --> 00:32:00,670 Where do they go? 666 00:32:00,670 --> 00:32:02,830 A zinc atom leaves its metal strip 667 00:32:02,830 --> 00:32:07,840 and goes into that beaker of zinc ions, right. 668 00:32:07,840 --> 00:32:11,011 But now you've got two charges, two electrons on the strip 669 00:32:11,011 --> 00:32:13,690 because it left a zinc 2 plus. 670 00:32:13,690 --> 00:32:15,730 Nothing more will happen. 671 00:32:15,730 --> 00:32:19,910 Nothing more will happen unless those 2 electrons go away. 672 00:32:19,910 --> 00:32:21,040 That's the whole point. 673 00:32:21,040 --> 00:32:23,680 What's so cool about batteries is 674 00:32:23,680 --> 00:32:27,430 that it's all about neutrality. 675 00:32:27,430 --> 00:32:29,440 If you think about batteries as current flowing, 676 00:32:29,440 --> 00:32:31,390 batteries is all about neutrality. 677 00:32:31,390 --> 00:32:33,460 It's all about keeping these things neutral 678 00:32:33,460 --> 00:32:36,520 because if I just build this charge up here, 679 00:32:36,520 --> 00:32:38,800 I can't have another zinc atom go in 680 00:32:38,800 --> 00:32:40,330 so the charge has to go somewhere, 681 00:32:40,330 --> 00:32:42,490 but that's what that wire is for. 682 00:32:42,490 --> 00:32:45,130 That's what this wire is for, right. 683 00:32:45,130 --> 00:32:47,410 This wire allows the charge to go over 684 00:32:47,410 --> 00:32:50,020 to the other place, the cathode, where 685 00:32:50,020 --> 00:32:54,710 the copper is sitting there saying, you know what, 686 00:32:54,710 --> 00:32:57,750 if I had two electrons-- 687 00:32:57,750 --> 00:33:00,800 if I had two electrons on the copper strip then 688 00:33:00,800 --> 00:33:03,665 I could use those as a way to lure in a copper 2 plus 689 00:33:03,665 --> 00:33:05,737 ion, right. 690 00:33:05,737 --> 00:33:07,320 I could use those as a way to lure it. 691 00:33:07,320 --> 00:33:12,580 And if I did that, then I'm doing what this did right here. 692 00:33:12,580 --> 00:33:16,120 It's the same thing that we just did with the plating 693 00:33:16,120 --> 00:33:19,570 except now those electrons are going through this wire 694 00:33:19,570 --> 00:33:20,800 up here. 695 00:33:20,800 --> 00:33:23,290 The zinc is trading electrons with the copper. 696 00:33:23,290 --> 00:33:26,980 That's keeping this neutral, so now the electrons go away 697 00:33:26,980 --> 00:33:29,670 and now another zinc can go into solution. 698 00:33:29,670 --> 00:33:32,700 Then the copper grabs them, plates a piece of copper, 699 00:33:32,700 --> 00:33:35,400 and then more electrons can come, right. 700 00:33:35,400 --> 00:33:36,860 It's the same thing. 701 00:33:36,860 --> 00:33:38,250 It's the same thing. 702 00:33:38,250 --> 00:33:39,510 This is what it looks like. 703 00:33:39,510 --> 00:33:42,570 If you take those electrodes out of the solutions 704 00:33:42,570 --> 00:33:47,490 after running this for five, 10 minutes, look at what happened. 705 00:33:47,490 --> 00:33:49,220 The copper plated. 706 00:33:49,220 --> 00:33:50,820 You got copper ions from solution 707 00:33:50,820 --> 00:33:55,937 plating that and zinc ions from solution leaving that. 708 00:33:55,937 --> 00:33:58,020 And so those are the reactions that are happening. 709 00:33:58,020 --> 00:33:59,400 One's happening on the zinc side and one's 710 00:33:59,400 --> 00:34:01,733 happening on the other side, but there's something else. 711 00:34:01,733 --> 00:34:04,590 There's something else because there's just 712 00:34:04,590 --> 00:34:06,000 one other piece of it that you've 713 00:34:06,000 --> 00:34:08,370 got to understand to understand how a battery works, 714 00:34:08,370 --> 00:34:10,860 and it's this thing here. 715 00:34:10,860 --> 00:34:14,969 So up here, this is my conduit for electrons to go. 716 00:34:14,969 --> 00:34:17,790 Each time it goes, I can plate. 717 00:34:17,790 --> 00:34:20,760 I can lose the more it goes, right. 718 00:34:20,760 --> 00:34:25,639 But notice if I lose 2 plus-- 719 00:34:25,639 --> 00:34:28,620 so I've got these 2 plus. 720 00:34:28,620 --> 00:34:31,300 It's not charged. 721 00:34:31,300 --> 00:34:32,610 Look at this. 722 00:34:32,610 --> 00:34:34,949 Copper sulfate in that case is copper nitrate. 723 00:34:34,949 --> 00:34:37,500 Copper sulfate goes in a solution, 724 00:34:37,500 --> 00:34:39,090 it's not a charged solution. 725 00:34:39,090 --> 00:34:43,449 These things are balanced, right, 2 plus, 2 minus. 726 00:34:43,449 --> 00:34:46,020 So now I'm taking only a 2 plus out of solution. 727 00:34:46,020 --> 00:34:47,010 No way. 728 00:34:47,010 --> 00:34:49,210 It's the same thing. 729 00:34:49,210 --> 00:34:52,699 You've got make it neutral again, all right. 730 00:34:52,699 --> 00:34:53,739 It won't work otherwise. 731 00:34:53,739 --> 00:34:56,060 You can't start building up charge in the solution. 732 00:34:56,060 --> 00:34:57,910 So that's what this thing is about. 733 00:34:57,910 --> 00:34:59,560 That's what this is. 734 00:34:59,560 --> 00:35:02,680 This is called a salt bridge and that completes the circuit. 735 00:35:02,680 --> 00:35:04,660 See, this lets the electrons flow. 736 00:35:04,660 --> 00:35:07,330 This gives ions. 737 00:35:07,330 --> 00:35:10,400 It doesn't matter what it is, right. 738 00:35:10,400 --> 00:35:11,470 That's the electrolyte. 739 00:35:11,470 --> 00:35:13,110 It's just a source of ions. 740 00:35:13,110 --> 00:35:15,020 Here is an ACL. 741 00:35:15,020 --> 00:35:17,300 It's an ACL, so now for every copper 2 742 00:35:17,300 --> 00:35:24,180 plus that plates onto the copper electrode, two NA plus atoms go 743 00:35:24,180 --> 00:35:25,860 into this beaker from the bridge, 744 00:35:25,860 --> 00:35:28,320 because here I've got dissolved salt. Dissolved salt, 745 00:35:28,320 --> 00:35:30,990 sodium chloride is in water, so I got all these sodium ions. 746 00:35:30,990 --> 00:35:34,200 I got all these chlorine ions. 747 00:35:34,200 --> 00:35:38,370 And when a charge imbalance happens because something 748 00:35:38,370 --> 00:35:41,760 plates here, I can draw sodium atoms out of the salt bridge 749 00:35:41,760 --> 00:35:44,193 and I can draw chlorine atoms out of that side, right. 750 00:35:44,193 --> 00:35:45,360 That completes your circuit. 751 00:35:45,360 --> 00:35:48,090 That's an iron neutralizer, the salt bridge, 752 00:35:48,090 --> 00:35:50,310 and this is allowing the electrons 753 00:35:50,310 --> 00:35:52,110 to keep everything neutral, and that's 754 00:35:52,110 --> 00:35:53,940 how you get the current, right. 755 00:35:53,940 --> 00:35:55,740 It's pretty cool. 756 00:35:55,740 --> 00:35:57,250 It's pretty cool stuff. 757 00:35:57,250 --> 00:35:59,530 Now the thing is, you can do this yourself. 758 00:35:59,530 --> 00:36:04,200 That's why I bought these for, is that you can-- 759 00:36:04,200 --> 00:36:06,330 somebody sees the the potato battery. 760 00:36:06,330 --> 00:36:08,990 I like the human battery. 761 00:36:08,990 --> 00:36:14,310 So these are just volt meters and these are 762 00:36:14,310 --> 00:36:15,990 set to the right thing, yep. 763 00:36:15,990 --> 00:36:20,220 And what you'll find, you can see what happens, right. 764 00:36:20,220 --> 00:36:25,363 Like when you touch the two electrodes, yeah, and sometimes 765 00:36:25,363 --> 00:36:26,280 you've got to squeeze. 766 00:36:26,280 --> 00:36:29,510 Oh, look at that current. 767 00:36:29,510 --> 00:36:32,120 You have electric-- you are providing electricity. 768 00:36:32,120 --> 00:36:34,310 You are the salt bridge. 769 00:36:34,310 --> 00:36:36,200 You are the bridge, so what that means is you 770 00:36:36,200 --> 00:36:39,410 are actually plating and taking metals off of these two 771 00:36:39,410 --> 00:36:40,610 electrodes right now. 772 00:36:40,610 --> 00:36:44,290 Your hands are doing that and you're trading electrons. 773 00:36:44,290 --> 00:36:46,582 You're a conduit for that to happen, right. 774 00:36:46,582 --> 00:36:47,540 You're the salt bridge. 775 00:36:47,540 --> 00:36:51,440 It's pretty cool, and you can play with these. 776 00:36:51,440 --> 00:36:52,970 You know, you have volt meters. 777 00:36:52,970 --> 00:36:55,640 You have lots of items on the table tomorrow 778 00:36:55,640 --> 00:37:00,020 maybe at a dinner, and I'm just suggesting that you play around 779 00:37:00,020 --> 00:37:02,670 with this idea, because look. 780 00:37:02,670 --> 00:37:04,830 This is what Volta did. 781 00:37:04,830 --> 00:37:09,150 This is literally what the name of that device, the guy 782 00:37:09,150 --> 00:37:11,790 that that's named after, this is what he did. 783 00:37:11,790 --> 00:37:13,650 He hooked up two different metals. 784 00:37:13,650 --> 00:37:16,270 I just put some paper clips in there, it works. 785 00:37:16,270 --> 00:37:18,210 It can be almost-- 786 00:37:18,210 --> 00:37:21,240 not almost, but lots of different metals will work. 787 00:37:21,240 --> 00:37:22,050 Why? 788 00:37:22,050 --> 00:37:23,730 We'll get to that in a sec. 789 00:37:23,730 --> 00:37:26,640 Here I've got another paperclip and a copper wire, 790 00:37:26,640 --> 00:37:28,260 right, two different metals. 791 00:37:28,260 --> 00:37:34,680 The power isn't coming from you as Galvani thought. 792 00:37:34,680 --> 00:37:38,880 No, the power is coming from the difference 793 00:37:38,880 --> 00:37:42,300 in potentials of those metals wanting or not 794 00:37:42,300 --> 00:37:43,980 wanting electrons. 795 00:37:43,980 --> 00:37:47,040 Everybody wants electrons, let's be honest, but who wants 796 00:37:47,040 --> 00:37:48,340 its more? 797 00:37:48,340 --> 00:37:50,758 It all comes back to the same stuff we talked about. 798 00:37:50,758 --> 00:37:52,800 It's just that now we're talking about the metals 799 00:37:52,800 --> 00:37:56,610 and whether they're more interested than the other metal 800 00:37:56,610 --> 00:37:58,090 in having those two electrons. 801 00:37:58,090 --> 00:38:00,830 That's what a potential is. 802 00:38:00,830 --> 00:38:02,410 That's what a potential is. 803 00:38:02,410 --> 00:38:07,810 Oh, now so OK. 804 00:38:07,810 --> 00:38:09,710 Here we go. 805 00:38:09,710 --> 00:38:12,250 There's the volt. So what determines it, right? 806 00:38:12,250 --> 00:38:16,010 What determines the potential? 807 00:38:16,010 --> 00:38:17,390 What determines the potential? 808 00:38:17,390 --> 00:38:18,680 Well, it's what I just said. 809 00:38:18,680 --> 00:38:21,590 You know, intuitively, it's the difference 810 00:38:21,590 --> 00:38:23,190 in these things wanting and saying, 811 00:38:23,190 --> 00:38:25,160 well, OK, I got copper and zinc. 812 00:38:25,160 --> 00:38:29,000 How do I know? 813 00:38:29,000 --> 00:38:33,050 Well, if you look at zinc-- 814 00:38:33,050 --> 00:38:33,668 let me see. 815 00:38:33,668 --> 00:38:34,460 Where do I have it? 816 00:38:34,460 --> 00:38:35,120 Here we go. 817 00:38:35,120 --> 00:38:37,400 Zinc, I want to make sure I get this right. 818 00:38:37,400 --> 00:38:48,090 So zinc is argon and 3d10 and 4s2. 819 00:38:48,090 --> 00:38:51,800 All right, OK, copper, oh, we got numbers 30 and 29. 820 00:38:51,800 --> 00:38:55,040 Copper is the same thing in terms 821 00:38:55,040 --> 00:38:58,505 of its argon core, 3d10 4s1. 822 00:39:03,730 --> 00:39:08,810 Which one of those wants to give up 2 electrons 823 00:39:08,810 --> 00:39:11,880 or take 2 electrons more than the other? 824 00:39:11,880 --> 00:39:15,890 That's what determines the potential. 825 00:39:15,890 --> 00:39:18,760 And you know, when you look at this, 826 00:39:18,760 --> 00:39:21,990 you might say-- this is from Averill so he actually 827 00:39:21,990 --> 00:39:24,690 is missing the f's because this is just taken right 828 00:39:24,690 --> 00:39:31,778 from the textbook, but anyway, so that's the potential. 829 00:39:31,778 --> 00:39:32,320 Look at this. 830 00:39:32,320 --> 00:39:34,840 This is like an energy diagram but these aren't electronics. 831 00:39:34,840 --> 00:39:37,890 These are just potentials, but the potential 832 00:39:37,890 --> 00:39:42,430 is related to which one wants the 2 electrons more. 833 00:39:42,430 --> 00:39:43,720 It's 2 plus. 834 00:39:43,720 --> 00:39:48,070 The oxidation state is 2 plus, so you look at this, 835 00:39:48,070 --> 00:39:50,170 you say, well, I don't know which one 836 00:39:50,170 --> 00:39:53,710 might give up electrons more. 837 00:39:53,710 --> 00:39:57,260 It turns out it's the zinc. 838 00:39:57,260 --> 00:40:00,175 And you might say, well, but wait a second. 839 00:40:00,175 --> 00:40:01,800 If I just take an electron out of here, 840 00:40:01,800 --> 00:40:04,320 won't it be harder than one out of here, 841 00:40:04,320 --> 00:40:05,460 because this only has 4s1? 842 00:40:08,110 --> 00:40:11,110 The answer is yes, but I'm taking 2. 843 00:40:11,110 --> 00:40:11,970 I'm not taking 1. 844 00:40:11,970 --> 00:40:16,930 I'm talking about the oxidation state of 2 plus. 845 00:40:16,930 --> 00:40:18,760 That's going to be harder here. 846 00:40:18,760 --> 00:40:21,820 It's harder to take a 4s1 in a 3d 847 00:40:21,820 --> 00:40:24,970 from that beautifully filled 3d shell than it 848 00:40:24,970 --> 00:40:26,320 is to take these 2s electrons. 849 00:40:26,320 --> 00:40:27,550 That's why that's higher. 850 00:40:27,550 --> 00:40:30,220 That's why that's hire, right. 851 00:40:30,220 --> 00:40:37,540 So what you can see is that the potential difference 852 00:40:37,540 --> 00:40:39,880 is all about chemistry, right. 853 00:40:39,880 --> 00:40:49,180 The delta v is all about the chemistry. 854 00:40:49,180 --> 00:40:52,520 It's all about all of the things that we've learned. 855 00:40:52,520 --> 00:40:55,460 It's more than that because of these solutions, 856 00:40:55,460 --> 00:40:57,080 so it's more complicated than that, 857 00:40:57,080 --> 00:41:00,940 but at the core of all of this is all the topics that we've 858 00:41:00,940 --> 00:41:05,155 learned, how strongly are electrons bound to an atom, 859 00:41:05,155 --> 00:41:07,870 to a metal, right. 860 00:41:07,870 --> 00:41:15,220 And so well, if I took cobalt, what would happen? 861 00:41:15,220 --> 00:41:18,940 If I took cobalt instead of copper, 862 00:41:18,940 --> 00:41:21,130 the voltage here would be 1/2. 863 00:41:21,130 --> 00:41:24,070 And you can sort of look at the table 864 00:41:24,070 --> 00:41:25,240 and think about why that is. 865 00:41:25,240 --> 00:41:29,530 Cobalt has a 4s2 but it's got less 866 00:41:29,530 --> 00:41:33,320 d electrons, and so is it going to be easier 867 00:41:33,320 --> 00:41:34,460 or harder to pull them out? 868 00:41:34,460 --> 00:41:36,920 Well, it's going to be easier than copper 869 00:41:36,920 --> 00:41:40,670 but harder than zinc so it goes in the middle, right. 870 00:41:40,670 --> 00:41:44,210 And so the potential difference is less for cobalt and zinc 871 00:41:44,210 --> 00:41:46,490 but you still get a potential. 872 00:41:46,490 --> 00:41:48,680 And so that's what Volta did, and he did 873 00:41:48,680 --> 00:41:51,260 all sorts of different metals. 874 00:41:51,260 --> 00:41:56,150 And you can understand why zinc and copper does this but copper 875 00:41:56,150 --> 00:41:58,090 and zinc doesn't. 876 00:41:58,090 --> 00:41:59,590 That's copper in the zinc solution. 877 00:41:59,590 --> 00:42:01,180 That's zinc in the copper solution. 878 00:42:01,180 --> 00:42:03,340 Nothing happens. 879 00:42:03,340 --> 00:42:06,340 The reason is the potential. 880 00:42:06,340 --> 00:42:08,540 It's just this. 881 00:42:08,540 --> 00:42:11,660 It's just literally the potential difference 882 00:42:11,660 --> 00:42:12,410 that we just drew. 883 00:42:12,410 --> 00:42:14,450 This is going to be easier to take. 884 00:42:14,450 --> 00:42:17,113 So I'm not going to go the other way, right. 885 00:42:17,113 --> 00:42:18,530 I'm not going to go the other way, 886 00:42:18,530 --> 00:42:21,010 so nothing happens when you do that. 887 00:42:21,010 --> 00:42:23,110 And then finally, the last kind of piece of this 888 00:42:23,110 --> 00:42:26,350 is that we need a reference because you can only 889 00:42:26,350 --> 00:42:28,348 get the changes in potentials. 890 00:42:28,348 --> 00:42:29,140 It's like enthalpy. 891 00:42:29,140 --> 00:42:31,330 You can only get the changes, not the absolute, 892 00:42:31,330 --> 00:42:33,490 so you've got to have a standardization. 893 00:42:33,490 --> 00:42:35,860 And the standardization in the world of batteries 894 00:42:35,860 --> 00:42:40,800 is hydrogen. So what you do when you 895 00:42:40,800 --> 00:42:44,550 think about battery potentials is you write down 896 00:42:44,550 --> 00:42:48,765 all of these reduction-- reduction is gaining electrons, 897 00:42:48,765 --> 00:42:49,890 right-- you write down all. 898 00:42:49,890 --> 00:42:50,500 It doesn't matter. 899 00:42:50,500 --> 00:42:52,708 You could write reduction, you could write oxidation. 900 00:42:52,708 --> 00:42:55,410 They're just a flip of the sign, right. 901 00:42:55,410 --> 00:42:57,580 It's just a flipped sign of the potential, 902 00:42:57,580 --> 00:42:59,940 but what you write these down with respect 903 00:42:59,940 --> 00:43:02,310 to a common electrode, and it's the standard. 904 00:43:02,310 --> 00:43:04,630 It's called the standard hydrogen electrode. 905 00:43:04,630 --> 00:43:08,550 So sometimes you'll see it as the SHE in the battery world. 906 00:43:08,550 --> 00:43:11,790 And what it is it's just a very nice platinum electrode 907 00:43:11,790 --> 00:43:12,850 that doesn't change. 908 00:43:12,850 --> 00:43:15,900 So it doesn't plate or lose atoms. 909 00:43:15,900 --> 00:43:18,120 And it's a reaction that on that electrode 910 00:43:18,120 --> 00:43:21,550 happens with hydrogen, hydrogen gas. 911 00:43:21,550 --> 00:43:24,678 And so what you do is you hook this up on one side. 912 00:43:24,678 --> 00:43:27,220 You hook that up on one side, and then you put all the metals 913 00:43:27,220 --> 00:43:28,190 against that. 914 00:43:28,190 --> 00:43:31,450 And you measure their potential. 915 00:43:31,450 --> 00:43:35,380 What's so powerful about the SHE is that now I've 916 00:43:35,380 --> 00:43:38,140 got all of these with respect to the same reference, right? 917 00:43:38,140 --> 00:43:40,845 So now when I look at my zinc-copper battery, 918 00:43:40,845 --> 00:43:42,970 well, it's just the difference between those that's 919 00:43:42,970 --> 00:43:45,540 the potential of the battery. 920 00:43:45,540 --> 00:43:48,620 So hydrogen electrodes gives you that ability 921 00:43:48,620 --> 00:43:50,760 to standardize it and create huge tables. 922 00:43:50,760 --> 00:43:53,810 And if you look up potentials of reduction, 923 00:43:53,810 --> 00:43:56,900 they're all related to hydrogen. You get thousands of them. 924 00:43:56,900 --> 00:44:02,012 How much does somebody want to lose, how many electrons? 925 00:44:02,012 --> 00:44:03,470 That's going to be in these tables. 926 00:44:03,470 --> 00:44:07,130 And it's by a setup that is very similar to the one I showed you 927 00:44:07,130 --> 00:44:09,970 that is related to hydrogen. OK. 928 00:44:09,970 --> 00:44:11,990 Or you could go the other way. 929 00:44:11,990 --> 00:44:13,280 If I had zinc-- 930 00:44:13,280 --> 00:44:15,980 I just showed you zinc. 931 00:44:15,980 --> 00:44:19,555 Copper in zinc doesn't happen because it's the wrong sign. 932 00:44:19,555 --> 00:44:21,680 But then what if I put copper-- instead of in zinc, 933 00:44:21,680 --> 00:44:22,700 I put copper in silver. 934 00:44:22,700 --> 00:44:24,710 So there's copper in zinc, copper in silver. 935 00:44:24,710 --> 00:44:26,490 It works. 936 00:44:26,490 --> 00:44:30,747 Because now silver is down here. 937 00:44:30,747 --> 00:44:31,580 How did I know that? 938 00:44:31,580 --> 00:44:33,247 Because I hooked it up to hydrogen and I 939 00:44:33,247 --> 00:44:35,960 compared it to copper. 940 00:44:35,960 --> 00:44:38,720 And so that's how you do battery chemistry is 941 00:44:38,720 --> 00:44:39,790 you look things up. 942 00:44:39,790 --> 00:44:42,980 You look up these potentials in tables, 943 00:44:42,980 --> 00:44:45,400 and you think about which voltage you need. 944 00:44:45,400 --> 00:44:50,220 And that gets us to this Nobel Prize. 945 00:44:50,220 --> 00:44:53,240 You say, well, why are lithium-- 946 00:44:53,240 --> 00:44:56,620 why did the Nobel Prize go to the-- 947 00:44:56,620 --> 00:45:01,610 not discovery but the development of lithium ions 948 00:45:01,610 --> 00:45:04,260 as a storage technology? 949 00:45:04,260 --> 00:45:07,490 And the reason is this. 950 00:45:07,490 --> 00:45:10,120 You saw-- it was the highest one on the list, too. 951 00:45:10,120 --> 00:45:11,670 Look at that. 952 00:45:11,670 --> 00:45:14,035 So now, I don't know what the potential of a lithium 953 00:45:14,035 --> 00:45:15,410 something battery is going to be, 954 00:45:15,410 --> 00:45:19,400 but I'm starting out with a pretty negative voltage 955 00:45:19,400 --> 00:45:21,110 with respect to hydrogen. That makes 956 00:45:21,110 --> 00:45:23,515 you think you might get high voltages, and you do. 957 00:45:23,515 --> 00:45:25,640 Yeah, but you have another thing that's really cool 958 00:45:25,640 --> 00:45:27,620 about lithium is how light it is. 959 00:45:27,620 --> 00:45:30,710 And those things combined make it a beautiful battery 960 00:45:30,710 --> 00:45:31,730 technology. 961 00:45:31,730 --> 00:45:33,710 And that's why the Nobel Prize was given. 962 00:45:33,710 --> 00:45:36,158 Because if you look at it on a plot like this, 963 00:45:36,158 --> 00:45:38,450 it's all the way up here, if you look at energy density 964 00:45:38,450 --> 00:45:39,860 versus volume. 965 00:45:39,860 --> 00:45:42,395 And a lithium battery works much the same way in the sense 966 00:45:42,395 --> 00:45:43,770 that you have the separator here. 967 00:45:43,770 --> 00:45:44,930 That's the electrolyte. 968 00:45:44,930 --> 00:45:47,610 But now it's rechargeable. 969 00:45:47,610 --> 00:45:50,982 And I don't have time to go into rechargeable batteries 970 00:45:50,982 --> 00:45:52,940 versus what are called primary batteries, which 971 00:45:52,940 --> 00:45:54,980 is the one I showed you. 972 00:45:54,980 --> 00:45:56,430 But all the chemistry is the same. 973 00:45:56,430 --> 00:45:58,380 You're shuttling ions back and forth. 974 00:45:58,380 --> 00:46:00,763 You've got that external circuit. 975 00:46:00,763 --> 00:46:02,180 And what I wanted to-- and there's 976 00:46:02,180 --> 00:46:03,330 a whole bunch of chemistry. 977 00:46:03,330 --> 00:46:05,330 So what has exploded in the last-- 978 00:46:05,330 --> 00:46:07,560 well, that's a bad word for batteries 979 00:46:07,560 --> 00:46:09,560 because that is a danger with lithium batteries. 980 00:46:09,560 --> 00:46:10,170 [LAUGHTER] 981 00:46:10,170 --> 00:46:13,070 But what has really made the field take off 982 00:46:13,070 --> 00:46:15,710 is you know the word. 983 00:46:15,710 --> 00:46:16,580 We're in the class. 984 00:46:16,580 --> 00:46:18,110 It's chemistry. 985 00:46:18,110 --> 00:46:21,290 Because the flexibility of where you 986 00:46:21,290 --> 00:46:24,440 can put that other electrode and what properties 987 00:46:24,440 --> 00:46:26,450 it has gives you enormous room. 988 00:46:26,450 --> 00:46:28,985 That's why lithium-ion batteries can go in everything now, 989 00:46:28,985 --> 00:46:30,110 all the way up to the grid. 990 00:46:30,110 --> 00:46:32,930 And that was my last Why This Matters 991 00:46:32,930 --> 00:46:36,480 in the last 2 and 1/2 minutes. 992 00:46:36,480 --> 00:46:37,470 This is the grid now. 993 00:46:37,470 --> 00:46:40,920 So we went from small to very big. 994 00:46:40,920 --> 00:46:44,910 The growth in solar and wind has been incredible 995 00:46:44,910 --> 00:46:47,830 over the last 10, 20 years. 996 00:46:47,830 --> 00:46:51,220 The problem, as I think I've shown you, is the variability. 997 00:46:51,220 --> 00:46:52,160 And so this is like-- 998 00:46:52,160 --> 00:46:54,660 if you zoom in here, that's the load, the black line. 999 00:46:54,660 --> 00:46:57,030 And this is what these two resources give you. 1000 00:46:57,030 --> 00:46:58,980 And you can see that it doesn't match. 1001 00:46:58,980 --> 00:47:03,010 If you zoom in on a day, then you really can see it, right? 1002 00:47:03,010 --> 00:47:03,910 There is the load. 1003 00:47:03,910 --> 00:47:06,400 And there's what you would get from solar and wind. 1004 00:47:06,400 --> 00:47:07,550 And so here's the question. 1005 00:47:07,550 --> 00:47:10,610 I said, well, OK, how do you fix this? 1006 00:47:10,610 --> 00:47:12,130 You got to store it. 1007 00:47:12,130 --> 00:47:15,767 There's no way to use renewables at large scales 1008 00:47:15,767 --> 00:47:16,600 unless you store it. 1009 00:47:16,600 --> 00:47:20,110 In fact, we're really at essentially the tipping point. 1010 00:47:20,110 --> 00:47:23,440 Because if I look at the countries in the world and what 1011 00:47:23,440 --> 00:47:25,940 their SPV penetration is-- and this is a couple years old, 1012 00:47:25,940 --> 00:47:27,482 but it's still pretty much the same-- 1013 00:47:27,482 --> 00:47:30,640 Germany, Greece, Italy at the top. 1014 00:47:30,640 --> 00:47:34,060 Sad frowny face here for the US of A. 1015 00:47:34,060 --> 00:47:38,770 But Germany is at 7.1% as of a few years ago. 1016 00:47:38,770 --> 00:47:41,160 That's a huge penetration of PV. 1017 00:47:41,160 --> 00:47:43,540 Well, here's the problem. 1018 00:47:43,540 --> 00:47:46,010 If you look at-- 1019 00:47:46,010 --> 00:47:47,800 this is Germany, now. 1020 00:47:47,800 --> 00:47:50,710 Huge penetration-- these are these six years, 1021 00:47:50,710 --> 00:47:52,810 seven years of adding PV. 1022 00:47:52,810 --> 00:47:54,250 This is how much they had. 1023 00:47:54,250 --> 00:47:55,720 They're now at 7%. 1024 00:47:55,720 --> 00:47:57,070 2016 is 7%. 1025 00:47:57,070 --> 00:48:00,400 This is how much the price of electricity 1026 00:48:00,400 --> 00:48:01,930 was in Germany when they added. 1027 00:48:01,930 --> 00:48:03,790 So notice that here is the sunlight 1028 00:48:03,790 --> 00:48:05,380 electricity during the day. 1029 00:48:05,380 --> 00:48:07,330 They can sell it for a lot of money. 1030 00:48:07,330 --> 00:48:10,840 But as they add more and more of this renewable to the grid, 1031 00:48:10,840 --> 00:48:13,690 its price goes down when it's available. 1032 00:48:13,690 --> 00:48:17,350 In fact, it's now not economical for them 1033 00:48:17,350 --> 00:48:21,660 to add more PV unless they can add it with storage. 1034 00:48:21,660 --> 00:48:23,730 Because actually the price has gone down so much 1035 00:48:23,730 --> 00:48:25,320 and it's gone up here when they're not 1036 00:48:25,320 --> 00:48:27,910 generating any PV electricity. 1037 00:48:27,910 --> 00:48:30,690 So you can come up with-- and they did in this paper-- 1038 00:48:30,690 --> 00:48:33,330 this sort of value factor which, when it goes below 1, 1039 00:48:33,330 --> 00:48:37,860 means there's no economic outcome that's positive here. 1040 00:48:37,860 --> 00:48:40,850 You can't make money any more. 1041 00:48:40,850 --> 00:48:42,150 And look at where that happens. 1042 00:48:42,150 --> 00:48:43,525 It's right around where they are. 1043 00:48:43,525 --> 00:48:45,400 It's at 5%. 1044 00:48:45,400 --> 00:48:48,460 You can't solve renewables at the scale of the grid 1045 00:48:48,460 --> 00:48:49,150 without storage. 1046 00:48:49,150 --> 00:48:50,900 And no option exists today. 1047 00:48:50,900 --> 00:48:52,353 It might be batteries. 1048 00:48:52,353 --> 00:48:53,770 It might be batteries, but there's 1049 00:48:53,770 --> 00:48:56,500 nothing that actually does it today at the scales 1050 00:48:56,500 --> 00:48:57,050 that we need. 1051 00:48:57,050 --> 00:49:00,310 So that's a real challenge for chemistry. 1052 00:49:00,310 --> 00:49:03,610 And I hope you guys have a great Thanksgiving and maybe hook 1053 00:49:03,610 --> 00:49:06,400 up some different metals. 1054 00:49:06,400 --> 00:49:09,090 And I'll see you all next week.