"Our findings inspired the team to seek the origin of voltage hysteresis elsewhere. However, no significant migration of iron or titanium atoms to lithium vacancies was observed, suggesting that some other process was siphoning power. To test this explanation, the researchers used a transmission electron microscope at Skoltech's Advanced Imaging Core Facility to monitor the atomic structure of a lithium-enriched battery cathode made of a material with the formula Li 1.17Ti 0.33Fe 0.5O 2 at different stages in the battery's charge-discharge cycle (see the image below). Or so the old theory of voltage hysteresis went," study co-author and Skoltech Ph.D.
"In the meantime, however, some of the transition metal atoms making up the cathode might have temporarily invaded the vacancies and then pulled back again, spending valuable energy on this jumping around. The other half of the cycle involves lithium ions going back as the energy gets expended, say to power a phone. Migrating toward the anode, they leave behind vacancies in the cathode. The recent study in Nature Chemistry provides experimental evidence refuting the previously held explanation of the phenomenon-technically known as voltage hysteresis-and offers a new theory to account for it.Īs a lithium-ion battery gets charged, lithium ions travel between its two electrodes. To unlock the potential of the batteries with lithium-enriched oxide cathodes, researchers have to understand the mechanism behind their inefficiency and exactly where the lost energy goes.
Over time, and particularly for applications consuming much energy, this lost power really adds up, making that type of batteries commercially not viable as of now. The problem with the latter technology is it has low efficiency: You have to spend significantly more power to charge up the battery than it will ultimately provide. The lithium-ion batteries used in electric vehicles and gadgets today have about half the capacity their cousins with lithium-enriched oxide cathodes could deliver.
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