A new battery restoration method can bring lithium-ion batteries back to 95% of their original capacity

Researchers at Cornell University have developed a way to restore old lithium-ion batteries to up to 95% of their original power. The method, called Direct Electrode-to-Electrode Regeneration, or DEER, does so without shredding, without complicated chemical processes, and at much lower cost than conventional recycling.

As lithium-ion batteries get older, a layer called the solid electrolyte interphase, or SEI, slowly forms on the electrodes. A thin SEI layer is actually needed for the battery to work, but after many charge cycles, it thickens, increasing resistance and reducing capacity. This buildup is the main reason electric vehicle batteries and energy storage systems are replaced, even when the rest of the battery is still in good condition.

Conventional recycling addresses this by shredding strong electrodes into a black, powdery material called black mass, then using energy-intensive chemical processes to extract important minerals to make new electrodes. DEER uses a completely different method. The electrodes are removed intact, soaked in an electrochemical bath that cleanly removes the SEI layer, and then returned to a new battery. This process also leaves a thin layer of lithium fluoride that helps keep the electrode stable and slows down future wear.

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In tests, restored batteries recovered up to 95% of their original capacity. When researchers repeated the restoration process on the same batteries, they kept about 90% of their power, showing that a single battery can last much longer. Economic studies predict DEER could lower recycled-battery production costs by 56% and reduce harmful air pollution and water use compared to conventional methods.

The team is now working to expand DEER beyond SEI-related damage to cover other forms of battery wear, including lithium loss, with the long-term goal of covering all wear that causes EV batteries to be retired. Industrial and large-scale energy storage systems are also on the roadmap.