The chemistry of building a better battery

Regarding the materials and chemistry that made this progression possible, Heather encouraged us to, “stay focused on the cathode because that’s where there’s the most diversity of materials.” She went on to add that, “the active material landscape for the cathode is dominated right now by mixed metals oxides.”

To understand important aspects and benefits of metal oxides as cathode materials, Heather took us back a step. In moving to reversible chemistry technology, she noted, “The very first cathodes were actually metal sulfides.” This was a huge advent in that, “you could reversibly get ions in and out,” which is different from the plating and stripping processes occurring in a lead acid battery.

When asked about how lithium-ion chemistry became so popular Heather noted advantages of lithium’s small ionic size and low mass, but she also called out, “Lithium-ion really became about finding the right material that where you could reversibly put lithium ions in and then get them back out.” Once someone figured out that lithium cobalt oxide worked well for this, she reflected that, “Metal oxides got popular pretty quickly because the voltages were higher and energy in a battery is a combination of the voltage of the battery as well as how many ions you can put in or take back out.”

“At this point in the lithium-ion space, there are two main cathode materials that are in production today,” said Platt. “One is lithium iron phosphate, you’ll hear that referred to as LFP, and then the other is either a nickel manganese cobalt or a nickel cobalt aluminum.” When asked the differences between these variations Heather noted tradeoffs such as, “LFP is a little lower energy but really cheap because it’s iron.” She went on to add, “the nickel containing compounds are higher energy, but they tend to be more expensive because you have to source cobalt in particular.”

Expanding on the importance of cathode materials, Platt called out that in addition to the materials themselves making a huge difference, battery manufacturers need to develop, “reliable manufacturing techniques that controls the micro or even nanostructures of the material,” to deliver reliable and optimized battery performance.

Getting back to her theme of how battery technology has enabled progression of other technologies, Heather noted that, “Once lithium ion actually became real and batteries were produced in large volumes, that enabled all of the devices we carry now.”

When asked of the future of the field this battery expert noted that, “I don’t think LFP is going anywhere in the next five years for sure, I and I wouldn’t be surprised if it is still a factor in the marketplace beyond that.” But her view of the future does have room for new technologies as well. Platt noted the promise of solid state battery technology and went on to add, “It will be very interesting to see how sodium-ion in particular plays a role and that is in part because sodium has better safety and it’s even cheaper than LFP.”

When asked about the challenges that need to be overcome for sodium-ion technology to play a significant role in the future, Heather shared, “At the moment, the biggest drawback with sodium is that it’s significantly lower energy.” She added, “Sodium is bigger and that means that inherently you’re looking at a heavier set of materials for the same structure; you ultimately are going to need some different structures with the sodium ion cathodes.”

Regardless of the challenges ahead for sodium-ion technology, Platt shared that she’s, “interested to see over the next 5, and definitely over the next 10 years, if sodium energy can come up or if it can be considerably cheaper than LFP and if that might enable companies producing sodium batteries to take some of the market share.”

In closing, Platt noted that like most things, batteries are not a one-size-fits-all technology and that that there will always be multiple battery chemistries in play. She summarized this nicely with, “One of the things that makes batteries so interesting to work on is that particular applications need different things and so as a result, use different batteries.”

For a deeper dive into this discussion and Heather Platt’s work, check out her interview on the Bringing Chemistry to Life podcast. There, we learn more about her background and get into much more detail on battery chemistry and where this field of research is headed.