Batteries are everywhere: in our smartphones, or assembled by the dozens in our electric vehicles. But sometimes they fail: they overheat, deform or stop working prematurely. What happens inside our batteries? And how can research in chemistry help us optimize their operation?
This is the subject of Charlotte Gervillié-Mouravieff’s research, a research scientist at the Solid Chemistry and Energy laboratory at the Collège de France.
Behind the apparent efficiency, there is unstable chemistry. Batteries seem perfectly integrated into our daily lives today, but their operation relies on a fragile balance. Charlotte Gervillié-Mouravieff explains that “inside our batteries, it’s just chemistry”: electrochemical reactions take place to “generate or store electricity.” This reversible mechanism allows for charging and discharging, “when everything goes well.” But this ideal vision hides a more complex reality: besides useful reactions, other undesirable processes develop silently.
These invisible phenomena concentrate at the interfaces between electrodes and electrolyte, but “there are interface reactions […] that we don’t want, which will generate heat, gas” and especially cause batteries to lose autonomy. While the causes are known, observing them remains difficult in these “closed systems,” and “all the chemistry inside is very sensitive” and current tools only provide a partial view of a much more complex chemistry.
Scientific challenge lies in studying these reactions in real-time without altering the battery. For this, research draws inspiration from biomedicine: “using optical fibers to see what is happening inside,” analyzing interactions between light and matter through spectroscopy. This approach allows to monitor the internal evolution of batteries, especially the impact of temperature and usage conditions on these critical interfaces, in order to “improve them better, stabilize them better.”
At the heart of the problem lies heat, produced by the Joule effect but amplified by internal degradations. “If the interfaces increase,” then, “more and more heat will be generated,” leading to an escalation, especially under sunlight exposure. This spiral explains the risks and performance loss, hence a major industrial challenge: better measurement for better cooling.
