95% capacity restored: Scientists find way to revive old EV batteries

Researchers at Cornell University have developed a battery recycling technique that could give ageing lithium-ion batteries a second life without first reducing them to raw materials.

The method, known as Direct Electrode-to-Electrode Regeneration (DEER), works by restoring worn battery electrodes so they can be reused in new cells. The findings indicate that some degraded electric vehicle batteries could potentially be refurbished using less energy and at a lower cost than conventional recycling, although the technique may not be suitable for every ageing battery.

The research targets one of the problems that develops inside lithium-ion batteries over time. During repeated charging and discharging, a layer called the solid electrolyte interphase (SEI) gradually builds up on the electrodes.

A thin SEI layer is important for battery operation, but excessive buildup can interfere with the movement of electrons and reduce the amount of energy a battery can store.

How Cornell’s battery revival method works

For the DEER process, researchers dismantle used battery cells and place their electrodes in an electrochemical bath containing 1,3-dimethyl-2-imidazolidinone (DMI).

The treatment removes the thicker SEI buildup while leaving the underlying electrode intact. The regenerated electrodes can then be used to manufacture new battery cells rather than being processed into raw materials.

The researchers found that regenerated cells could recover up to 95% of their original capacity. The treated batteries also showed a slower rate of capacity loss compared with batteries that were left untreated.

According to the results, untreated degraded batteries lost capacity at 0.072% per cycle, while batteries restored using DEER lost capacity at 0.042% per cycle. This lower degradation rate remained for roughly 800 cycles before increasing.

Could old EV batteries be regenerated more than once?

The researchers also tested the process a second time. After another round of treatment, a previously regenerated battery recovered 90% of its original capacity.

The finding raises the possibility that electrodes could potentially be regenerated multiple times, although the effectiveness would depend on how severely the battery has degraded.

How is DEER different from conventional battery recycling?

Most commercial lithium-ion battery recycling processes begin by shredding or crushing spent batteries into a material commonly known as black mass.

The resulting mixture is then processed using high temperatures, chemicals or a combination of both to recover valuable materials such as lithium, cobalt, nickel, manganese, copper and aluminium.

Rather than breaking the battery down completely, Cornell’s approach attempts to preserve and restore the electrode itself. That could reduce the amount of processing required in cases where the electrode remains structurally usable.

The research therefore points to a potential middle ground between continuing to use a degraded battery and completely recycling it: regenerating the components that have lost performance and putting them back into service.