Recharge, then recharge some more Researchers figure out how to get fresh lithium into batteries Regular doses of lithium let a battery survive nearly 12K cycles (and counting). John Timmer Feb 21, 2025 4:33 pm | 11 Credit: Kinga Krzeminska Credit: Kinga Krzeminska Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreAs the owner of a 3-year-old laptop, I feel the finite lifespan of lithium batteries acutely. It's still a great machine, but the cost of a battery replacement would take me a significant way down the path of upgrading to a newer, even greater machine. If only there were some way to just plug it in overnight and come back to a rejuvenated battery.While that sounds like science fiction, a team of Chinese researchers has identified a chemical that can deliver fresh lithium to well-used batteries, extending their life. Unfortunately, getting it to work requires that the battery has been constructed with this refresh in mind. Plus it hasn't been tested with the sort of lithium chemistry that is commonly used in consumer electronics.Finding the right chemistryThe degradation of battery performance is largely a matter of its key components gradually dropping out of use within the battery. Through repeated cyclings, bits of electrodes fragment and lose contact with the conductors that collect current, while lithium can end up in electrically isolated complexes. There's no obvious way to re-mobilize these lost materials, so the battery's capacity drops. Eventually, the only way to get more capacity is to recycle the internals into a completely new battery.There's potentially another option: inject some new material into the battery itself. While there are physical limits to how much you can cram into the physical space inside the battery, this does have the potential to extend its useful life and get more out of the cost and energy required for manufacturing.By all appearances, however, that isn't what the team behind the recent research was trying to do. Instead, most of the new paper describing the researchers' work is focused on a related problem: getting lithium into a battery during the manufacturing process. It just happens to be the case that the approach they are developing will work for both manufacturing and rejuvenation.In current manufacturing processes, the lithium is typically included in one of the electrodes, leaving the battery ready for use. There are, however, a number of electrode materials that can potentially store a lot of lithium but aren't easy to load up with it ahead of manufacturing. So, the researchers were interested in manufacturing the battery, then finding a way to get the lithium in afterward.So, they started searching for a lithium compound that fit a very long list of fairly specific properties. One is that it had to undergo reactions that liberated the lithium within the voltage range typically used by the mature batteries so that all of it would eventually react. The reaction also had to be irreversible to prevent ongoing cycles of reactions between the lithium and the remains of the chemical that brought it there. Those chemical remains had to be easy to get back out of the battery, as well. Finally, the chemical had to be soluble in battery electrolytes and stable when exposed to air and moderate heat so it could be used in existing manufacturing.Lithium deliveryThe chemical they came up with is LiSO2CF3. Under voltage, the chemical will lose both the lithium and an electron, leaving behind an unstable chemical that breaks down into SO2 and a mixture of HCF3 and C2F6. All of those products are gases at room temperature and will simply bubble out of the electrolyte if there's any space for them to do so.To test it, the researchers essentially built a lithium-free lithium battery. Then, using an electrolyte with dissolved LiSO2CF3, they filled an electrode with lithium ions by applying a voltage, drawing off the gases that formed in the process. Once fully loaded, they could seal the battery off, expecting it to cycle the lithium as normal.In their testing, they use a couple of unusual electrode materials, such as a chromium oxide (Cr8O21) and an organic polymer (a sulfurized polyacrylonitrile). Both of these have significant weight advantages over the typical materials used in today's batteries, although the resulting batteries typically lasted less than 500 cycles before dropping to 80 percent of their original capacity.But the striking experiment came when they used LiSO2CF3 to rejuvenate a battery that had been manufactured as normal but had lost capacity due to heavy use. Treating a lithium-iron phosphate battery that had lost 15 percent of its original capacity restored almost all of what was lost, allowing it to hold over 99 percent of its original charge. They also ran a battery for repeated cycles with rejuvenation every few thousand cycles. At just short of 12,000 cycles, it still could be restored to 96 percent of its original capacity.Before you get too excited, there are a couple of things worth noting about lithium-iron phosphate cells. The first is that, relative to their charge capacity, they're a bit heavy, so they tend to be used in large, stationary batteries like the ones in grid-scale storage. They're also long-lived on their own; with careful management, they can take over 8,000 cycles before they drop to 80 percent of their initial capacity. It's not clear whether similar rejuvenation is possible in the battery chemistries typically used for the sorts of devices that most of us own.The final caution is that the battery needs to be modified so that fresh electrolytes can be pumped in and the gases released by the breakdown of the LiSO2CF3 removed. It's safest if this sort of access is built into the battery from the start, rather than provided by modifying it much later, as was done here. And the piping needed would put a small dent in the battery's capacity per volume if so.All that said, the treatment demonstrated here would replenish even a well-managed battery closer to its original capacity. And it would largely restore the capacity of something that hadn't been carefully managed. And that would allow us to get far more out of the initial expense of battery manufacturing. Meaning it might make sense for batteries destined for a large storage facility, where lots of them could potentially be treated at the same time.Nature, 2025. DOI: 10.1038/s41586-024-08465-y (About DOIs).John TimmerSenior Science EditorJohn TimmerSenior Science Editor John is Ars Technica's science editor. He has a Bachelor of Arts in Biochemistry from Columbia University, and a Ph.D. in Molecular and Cell Biology from the University of California, Berkeley. When physically separated from his keyboard, he tends to seek out a bicycle, or a scenic location for communing with his hiking boots. 11 Comments