Creating better batteries for electricity grids

0:07- Hello, and welcome to the Physics World weekly - podcast. - I'm Hamish Johnston. - My guest is Lynn Ma, who is in - the department of applied physical sciences - at the University of North Carolina - at Chapel Hill. - Lynn's research group tackles energy and environmental - challenges - using sustainable - materials - and electrochemical - techniques. - In this episode, we talk about the growing - importance of energy storage in electricity - grids.

0:42- Much of this is driven by the growth - of wind and solar generation, - which can both be intermittent in nature. - Lynn talks about the batteries that are currently - used in grids and explains what improvements are - needed as more renewable energy comes online. - We chat about the different battery technologies - that can be used for grid storage, and - Lynn explains why sodium - ion batteries - offer advantages - over lithium based devices - when it comes to large scale deployments.

1:18- Lynn also talks about some of the safety - issues - surrounding large battery facilities. - This podcast is presented in partnership with the - Electrochemical - Society. - The mission of the ECS - is to advance theory and practice - at the forefront of electrochemical - and solid state science and technology - and allied subjects. - Here's my conversation - with Lin Ma. - Hi, Lynn. Welcome to the podcast. - Hi, Hamish. Nice to meet you. Thanks for - the opportunity.

2:03- So, Lynn, can we start with a sort - of a background question? - What are the current roles - played by batteries - in electricity grids? - That's a great question. I think the current - main - responsibility - of batteries in grid storage is about peak - shaving. - As we know, - we have different demands every day regarding the - electricity. - Sometimes we have the peak. Right? - So - the use of batteries - actually can do the peak shaving. - And on another side, it has some financial - advantages.

2:41- So for example, we can charge the batteries - when the cost is low, and we can - discharge - the batteries - when the price is high. So that's my - understanding about current role of batteries in grid - storage. - And and when you talk about peak smoothing, - that that that's the idea. I mean, I - suppose something that happens - particularly with renewables - is that there are certain times of the - day or or times of the year when - you have lots of renewables, - lots of renewable energy being produced, but people - aren't - using it.

3:19- And then there comes a time when - people really want to use electricity, - and renewables aren't pumping out that much energy. - And so you store the energy in the - battery, - when the sun is shining, - let's say, and you release it when, - the need is high - and the sun might not actually be shining. - Is that is that how it works? - Yeah. That's perfect, - illustration. - That's correct. - You know, like you mentioned, the sun is - not not always shining.

3:52- The wind is not always blowing. That's why - we need energy storage technology to be coupled - with energy conversion technology, - to make a cycle and make sure we - have the clean energy. - And can you can you sort of give - us a little bit of an idea of, - how many - batteries or or what sort of capacity - is currently being used in - a typical - electricity grid? I mean, I would imagine that - that would vary from country to country and - region to region. But are are there currently - lots of batteries out there being used for - this, - application, or is this sort of something for - the future?

4:37- That's that's a great questions. - Like like you said, this, the the detailed - number regarding the capacity of the batteries being - used - in grid storage. - Depends on the country, depends on the state, - and I don't really have a detailed number - in my mind for all of the all - all of the regions. - But I would like to - point out that, - the the batteries, - will be like a infrastructure instead - of, like, - a traditional batteries, - to be inserted into some device like we - are using in cell phone or laptop. We - should treat it as a inf infrastructure in - the future - when it's coupled with, - grid storage.

5:24- Okay. - And and how how will this expand - as - renewables - input - increases? - I mean, I'm guessing if you're if you're - rolling out lots more - solar cells and, - and wind turbines, then the need for - grid storage, - using batteries and other techniques - is going to increase. - That is correct. - When - the renewable energy start to expand, we should - also expand - battery technology - to be coupled with increasing trend of - the energy conversion technologies.

6:03- And one of the important parameters we should - pay attention is about the duration. - So currently, the typical batteries in grid storage, - the duration is around two to four hours. - In the future, - if the renewable energy expanded, - I would expect we should increase - the duration of energy storage. - So that being said, we have - more demanding requirement - on the lifetime - of next generation battery technology - when we are using for grid energy storage.

6:40- And what what is the state of the - art in the batteries that are currently - used in grids? Are they are they basically - much larger versions of the lithium ion batteries - that we use in our - electronic equipment, personal electronic equipment, or are are - are they very different? - That's a great question. - So, - currently, there are two mainstream type of - technology routes regarding lithium ion batteries. - One is called lithium iron phosphate - as cathode - and the graphite as anode.

7:16- Another one is layer oxide - cathode, which is an m c like - and the graphite as anode. - So for the grid energy storage, - because it has really huge capacity, - So safety is one of the most important - factors. - So considering this factor, - the lithium iron phosphate, - which is graphite, is a mainstream - battery technologies is being used in this type - of direction. - And, like you mentioned, - in our - traditional applications of lithium batteries like laptop - and cell phones so it depends.

7:56- So some of the batteries are - layer oxide cathode versus graphite, and some of - them are lithium iron phosphate versus graphite. - But in the grid energy storage, - the lithium iron phosphate versus graphite, - is the best choice in the current scenario. - And one thing that surprised me, Lynn, when - I was doing a bit of research for - this, - for this article - for this interview, I should say, and it's - something that you've mentioned already, is that the - time scale - for batteries - is is much shorter - than I had expected. You you know, when - I charge my mobile phone, I can usually - get a few days - out of it.

8:38- But it seems that when batteries are used, - on a grid, - they're only used for a few hours. - What what why is that? Why is the, - is the time frame so short? Or or - is it because batteries - are the only technology that we have that - can that can work on those time frames. - Is that is that the key? - That's a great question. - So, basically, - the capacity of a battery - is is fixed is a fixed number. Right? - So that being said, the time frame is - correlated with - the say rate - we are using for the batteries. So if - we are using the high say rate applications, - like high power applications, - and we have - to deliver all the capacity within a short - time of frame.

9:29- But if we are using, like, low power - applications, - we can use a longer time - during one charge process - or one discharge - process. So that that's a difference we realize - in our, - real lifetime. - But - the charge and the discharge rate can really - affect - the real lifetime of batteries. - So that is why we have to think - about - how can we identify - the battery failure mechanism - when the charging or discharging rate is high. - And we have to think about how can - we - extend the lifetime - when - the charging of this charging rate is high.

10:16- So is that is that the main challenge - in, - in designing batteries - for grid applications - to to get the correct - charge and discharge rates? Is that what people - are spending a lot of time - doing research on at the moment? - That is - part of it, I would say. You you - are correct. And so is is there anything - else that, - any other - aspects of research? I mean, I would imagine - safety - is probably a very big issue as well - because, - you know, these these battery facilities are are - huge, aren't they? And you certainly don't want - to, - you know, to to have unsafe situation with - a fire - or, an uncontrollable - discharge.

11:03- Yeah. That's totally correct. Safety is also another - important factors, - to be considered when we are using battery - grade energy storage. - Currently, people are working on lots of components - innovation like electrode materials, - electrolyte materials, - interface, - and - the the packing tech technologies - to try to address the the safety issues. - And, also, some groups are working on, like, - sensor technologies - to be able to identify the early signal - about battery safety event - so we can take some actions before the - fire start to happen.

11:44- I see. - And and can you can you give us - an idea of of how big, - a battery - system would be - on a grid? - You you know, may may maybe in units - of mobile phone - batteries. I mean, would would a typical, - system you know, would it be in your - thousands of mobile phone battery - equivalents or millions of mobile phone battery equivalent? - Is it is it possible to, you know, - to to to give our listeners an idea - of exactly how big - these battery facilities would be? Sure. Sure. Yeah.

12:23- I can I can, - provide some examples here? - So for example, in our - cell phone, - the capacity of a typical lithium batteries is - between 500 milliampere hour - to 1.5, - ampere hour. - So that's the typical range about the cell - phone batteries. - And, - recently, I had collaborations, - with the industrial partners. - So they are doing battery safety testing - for the battery pack - being used for grid energy storage. - And they told me, - one unit - they are testing for the - grid battery energy storage is around between - three hundred and five hundred - amp per hour. That's just one u that's - just one unit. So we can imagine it's, - like, three or 500 times - than our cell phone. And in the real - grid energy storage, it's not only like a - one unit. Right? It's it can be - different numbers of the unit, - depends on the size - of the in infrastructure.

13:39- So I think this is one example to, - give the listeners one idea about - the size difference between the grid energy storage - and our cell phone battery size. - I see. - And that that sort of brings me on - to to my next question, and that's about - some research that you're doing. Much of your - research is focused - on sodium - ion - batteries. - What are the benefits of using this technology - for grid storage over, say, - a more traditional lithium ion - batteries? I I mean, I would imagine one - thing is that sodium is sodium a much - more common - and easier to work with element than lithium?

14:24- Is that one of the features? Yeah. That - that's that's a great question, and your point - is totally correct. - So lithium ion battery is so great, and, - it's wonderful. - It has relatively - long lifetime, good safety, and so on. - But, you know, the whole world need energy - storage to support clean energy for the future. - So that being said, every element - has to undertake its own responsibility. - So lithium can undertake his responsibility, - but lithium needs help. They need a support.

15:00- And sodium is a perfect supporter - because sodium has a really high earth abundance, - and its being useful can really make the - batteries working well. - On another side, - when we are using sodium batteries, - the current collectors for the negative side doesn't - need to be copper anymore. - We can still use aluminum. - That's another advantages. - And, also, for the cathode side, - we don't need to use, like, high nickel - containings, - and some earth abundant - element like iron can also be used - for sodium and batteries cathode materials.

15:42- So all in all, the use of sodium - batteries can really release - the supply chain - globally - to make sure every country, every state can - have the resource to build sodium - batteries to achieve - the clean energy goal. - And and what's your view in terms of - the, you know, the sodium battery technology? If - you I mean, if if people work really - hard on developing sodium ion batteries, - do you think that their performance will be - as high - as lithium - batteries or or or maybe even better?

16:18- Is there, - I mean, are there any compromises in terms - of performance - with sodium? Or is it at the end - of the day, do you think it it - will be just as good - a material as lithium? - From the energy density perspective, - sodium and battery doesn't have advantages compared to - lithium because sodium is heavier than than lithium. - But, we we know grid energy storage doesn't - care too much about gravimetric - energy density. - And for the sodium batteries, it has some - unique advantages.

16:54- For example, like low temperature performance, - because sometimes, - PC - solvent cannot be used - for lithium batteries because of the, - negative electrode issues gonna be caused by the - PC. But for sodium batteries, PC is a - friendly solvent, so people can use PC, which - can have a good low temperature performance - because we know the infrastructures, - has to be located in certain area, which - has a various - temperature range between a low temperature and high - temperature.

17:33- So wide temperature operation range is also important - for sodium batteries, - and the sodium batteries can do well in - in relatively, - wide temperature range operation. - In the future, I would imagine, - both lithium ion batteries and sodium batteries can - take the role - in grid energy storage. - And currently, as we know them, some companies - like CATL has launched - sodium ion battery technologies - in real commercial - applications, - like - grid, - electric vehicles.

18:08- Yes. It's a wonderful technology. - And we've talked a bit about lithium - batteries, and we've talked a bit about sodium - batteries. - What other research topics are you working on - at the moment? - As we know, currently, - machine learning, - artificial intelligence, - they are quite hot. I think they are - great tools, and - the research - has to be combined with - the new tools to be able to achieve - faster goals. Right? - So, currently, my group is trying to combine - with - machine learning, AI, - and this kind of technique - with our - unique battery failure mechanism analysis techniques - and try to get some understanding - about the detailed failure analysis - of batteries.

19:01- So these knowledges can be - used - for future - battery chemistry - design to further extend the battery lifetime. - And meanwhile, we are also trying to develop - advanced sensing technology coupled with AI or machine - learning - to be able - to detect - or predict - the state of health of batteries in the - future. - All in all, our group is focusing on - combining with, like, AI technique - for the next generation battery technology. - Oh, that's really interesting. I mean, it just - it just goes to show that, you know, - machine learning and and AI - can help, - just about everywhere. So I suppose in your - situation, you're using - AI to - help you design - better batteries and then also - monitor those batteries and make sure that they - don't fail - and make sure that they're safe.

20:04- That's correct. - Well, thanks. Thanks, Lynn. Thanks so much for - coming on the podcast and talking about batteries - in - electrical grids. And, here at Physics World, we - wish you all the best with your research. - No problem. Thank you so much for the - opportunity. - It's a wonderful talk. - That was Lynn Ma of the University of - North Carolina at Chapel Hill. - Thanks to Lynn for his insights into battery - storage in electricity grids.

20:44- The Nobel Prize for Physics will be awarded - on the October 6. - Stay tuned for two special Nobel themed podcasts. - The first will take a quirky look at - some laureates of the past, and we'll make - a few predictions - of who could be making that trip to - Stockholm - in 2026. - The second podcast - will focus - on this year's winners - of the Nobel Prize for Physics. And who - knows? There might even be a physicist - who bags a chemistry or economics - or even medicine prize.

21:23- So stay tuned for those podcasts - and all of our coverage of the 2026 - Nobel prizes. - I'm afraid that's all the time we have - for this week's podcast, - which is presented in partnership - with the Electrochemical - Society. - The mission of the ECS - is to advance theory and practice - at the forefront - of electrochemical - and solid state science and technology - and allied subjects. - I'm Hamish Johnston, and our producer is Fred - Iles.

21:58- The music in Physics World's podcasts - is called one three seven, and it was - composed and performed by the physicist - Philip Moriarty. - Thanks for listening, and we'll be back again - next week.