Dr. Ryan Bayliss Talks Energy Storage and Lithium-ion Battery Innovation
Lithium and cobalt are key components of lithium-ion batteries, and are receiving a huge amount of attention as demand for these batteries continues to grow.
Graphite is another key material required for lithium-ion batteries, but it has not gotten as much attention this year. To learn more about its role in these batteries and about the future of energy storage technology, the Investing News Network spoke with Dr. Ryan Bayliss, a senior research fellow in the Department of Materials and a fellow of the Oxford Martin School at the University of Oxford.
In the interview below, Bayliss, who is also interim chief of staff of the Faraday Institution, the UK’s new electrochemical energy storage institute, also discusses nickel’s role in lithium-ion batteries, as well as electric vehicle (EV) adoption in Europe. Bayliss spoke to the Investing News Network via phone.
INN: Tell me about graphite’s role in lithium-ion batteries.
RB: Why do we use graphite in lithium-ion batteries? It’s because at the moment we’re not able to safely and reversibly cycle lithium metal — that’s what we’d really like to do, because that would give a battery cell with significantly higher energy density. Graphite, as an alternative anode, is generally regarded as the best negative electrode commercially available today for lithium-ion batteries. People are still trying to crack the lithium metal anode in laboratories all over the world, and have been since Stan Whittingham first demonstrated reversible intercalation in LiTiS2 in the 1970s, but it’s not a challenge regarded yet as having been satisfactorily overcome.
INN: Does that mean a lithium-ion battery without graphite would be ideal?
RB: I don’t think it’s correct to say they are trying to get rid of graphite, and it’s not that graphite itself is not a good electrode material. In fact, graphite is a very good electrode material in the extent that: what are you looking for in your anode? You’re looking for a large capacity and a low voltage vs. lithium metal. If you think about what the best cathodes offer you, they offer you something like 200 milliamperes per gram. Now, milliamperes per gram just means an amount of charge per weight. Graphite, which is the other side of the “sandwich,” the other electrode, gives you 372 milliamperes per gram. Graphite is actually one of the reasons why lithium-ion batteries are as good as they are.
However, if we want to go more energy dense, which is the desire of lots of different industries, one of the routes is to go to what we call a lithium metal battery, and that means that you would no longer use graphite in its current format for intercalating lithium. What you would do is you’d have a lithium metal electrode and then some new electrolyte, a liquid or maybe a solid, in the middle for the filling of the sandwich that would enable you to efficiently and safely strip and plate lithium metal. That would result in a lithium-ion battery with a much higher energy density . The Faraday Institution is currently looking to fund a large research project in the UK on solid-state batteries, and I hope will announce who will lead that effort in early 2018. That is an exciting basic science research project that could have big implications for future energy storage technologies.
INN: Is there a long-term future for graphite in lithium-ion batteries?
RB: I’m sure it will be in the short term and probably medium term. The question regarding the long term is: can somebody create a transformational device, perhaps enabling a lithium metal anode, that gives a higher-energy-density battery and means that you don’t need to use graphite? That probably requires some sort of scientific breakthrough in the materials space. If you asked me if I think that’s possible in the short term, the answer is no. Graphite is as good of a material as we could pretty much think of based on an intercalation mechanism. I’m sure that from your perspective and from the timelines that you’re looking at, graphite has a very good life ahead of itself.
INN: Can you talk about some of the different types of battery cathodes? We’ve seen efforts to reduce the amount of cobalt and increase the amount of nickel to cut costs, for example.
RB: In the layered oxides typically used for lithium-ion battery cathodes today, examples include the NMC-type and the NCA-type families. People would generally like to produce a stable cathode predominantly based on nickel, [with that] likely being stabilized by small percentages of other metals like cobalt, manganese and aluminium. Looking forward, if we can’t go beyond the traditional cation redox-based intercalation electrodes, a high-nickel-content cathode has a good chance of being one of the best we can make. But of course, there might be some smart people out there who are about to prove this incorrect!
INN: Are you seeing a clear shift to EVs now in Europe? Do you think there is an impact on EV demand associated with charging infrastructure for EVs there? We’re not seeing as much of that infrastructure developed here in Canada yet.
RB: To the best of my knowledge, there was little EV infrastructure in the UK only five years ago, though you definitely notice its presence more now. Only last week, the electric cars in the UK received a funding boost, with the government earmarking GBP 340 million for a national charging network and subsidies for vehicle purchases. I’m not so sure on Europe [as a whole], I suspect it’s quite different country to country. I would hope we are starting to see a significant increase in charging infrastructure in all countries, including Canada, going forward.
INN: We’ve heard that different local climates can change battery performance markedly, can you comment on this?
RB: It’s hard for me to comment specifically about the environment in Canada; however, my immediate thoughts are that lithium-ion batteries typically don’t like to operate in cold weather. Below certain temperatures they don’t work because you require some ambient temperature for the processes in the batteries to happen. The ions have to hop and that requires thermal energy. In the extreme north and south where the temperatures can get very cold, batteries might not be the obvious choice, particularly in winter, unless you can create some mechanism by which the battery is able to self-warm itself.
Whether that’s efficient or not in terms of the total energetics I don’t know, but there are certainly questions around the performance of lithium-ion batteries in temperature extremes. Also, in very hot conditions battery lifetimes tend to fall dramatically as the elevated temperatures drive unwanted side reactions that reduce the battery’s performance; this might result in reduced driving range in your EV.
