Smarter charging boosts lithium–tellurium battery performance

A research collaboration between engineers at The Ohio State University and Korea University reveals how performance of a next-generation battery material could be improved.

Their study, published in Nature Communications, focuses on lithium–tellurium energy storage systems. Tellurium offers high electronic conductivity and high volumetric capacity compared to sulfur and selenium. However, scientists understand much less about how lithium–tellurium (Li-Te) batteries operate internally than more widely studied lithium–sulfur batteries.

Chemical and Biomolecular Engineering Professor Joseph Kwon explained that Li-Te batteries have not succeeded commercially because knowledge of their degradation characteristics has been elusive, until now. He and his colleagues in Korea discovered a complex chemical process that may help explain why this type of battery’s performance declines over time.

A rechargeable battery contains material that repeatedly transforms as it stores and releases energy. In most next-generation batteries, the active material dissolves into a liquid and then re-forms as a solid, which Kwon described as “a fairly simple two-step dance”. But Li-Te batteries perform a much more complicated dance: an extra solid compound, lithium polytelluride (Li2Te6), appears in the middle of the reaction.

“Using real-time X-ray imaging, we literally watched these crystals form, grow and dissolve inside a working battery,” Kwon said. “The surprise was that the crystals formed during charging are much larger than those formed during discharging, and the large ones never fully go away.” These lingering crystals lock up active material and degrade the battery.

Kwon’s quantum-mechanical calculations and kinetic simulations helped explain why the material asymmetry exists, which then pointed to a fix — a tailored charging protocol that dissolves these stubborn crystals. With it, the battery retained roughly nine times more capacity after 30 cycles.

Because it can pack more energy into less volume, tellurium is attractive to industry. Battery research often focuses on finding new electrode materials or electrolytes. Kwon and colleagues show how gaining a detailed understanding of the reactions already taking place inside a battery can reveal another path for improving its operation.

“It’s a smarter charging protocol, essentially a software-level change,” Kwon said. “That matters industrially. Charging protocols can be deployed in battery management systems at nearly zero manufacturing cost. It’s also a template for a broader idea — that mechanistic understanding plus process control can rescue chemistries that were written off as impractical.”

His collaboration with Korea University was catalysed by his visit to co-author Professor Seung-Ho Yu’s lab in Seoul. They both realised their research strengths were complementary. Yu and his team are world experts in operando X-ray visualisation of batteries, while Kwon’s group brings multiscale modelling and reaction kinetics acumen.

“His experiments revealed what happens, while our simulations explained why. Neither half of the story stands alone, and I expect this to be the first of several joint efforts,” Kwon said.

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