Scientists develop a way to restore aging EV batteries without breaking them down into raw materials

Researchers at Cornell University have devised a method to rejuvenate aging lithium-ion batteries without dismantling them into their constituent materials. Known as Direct Electrode-to-Electrode Regeneration, or DEER, the technique revitalizes worn battery electrodes, enabling their reuse. The findings suggest that some electric vehicle batteries could be refurbished more affordably and with less energy consumption than traditional recycling methods.

However, the process may not be applicable to all degraded cells. The study targets a common issue in aging lithium-ion batteries: the accumulation of a solid electrolyte interphase (SEI) layer on electrodes. As batteries undergo charging and discharging cycles, the SEI layer thickens, impeding electron flow and diminishing battery capacity.

In the Cornell approach, used cells are dismantled, and the electrodes are subjected to an electrochemical bath containing the chemical 1,3-dimethyl-2-imidazolidinone (DMI). This treatment eliminates the excessive SEI layer without dismantling the electrode structure. The regenerated electrodes can subsequently be utilized to manufacture new battery cells.

The researchers discovered that the restored cells could regain up to 95% of their original capacity. Furthermore, treated batteries demonstrated slower degradation rates compared to untreated batteries. Untreated degraded cells experienced a capacity loss of 0.072% per cycle, while DEER-treated batteries exhibited a loss of 0.042% per cycle.

This slower degradation persisted for around 800 cycles before gradually increasing. The method diverges from conventional recycling techniques, which typically involve breaking down spent batteries into a composite known as black mass. Subsequent processes employ high heat, chemicals, or a combination thereof to recover valuable metals like lithium, cobalt, nickel, manganese, copper, and aluminum.

These methods recover valuable materials but also destroy electrodes and other potentially usable components. DEER treats batteries as devices with repairable components rather than a source of raw materials. This distinction could prove advantageous for electric vehicle batteries. EV battery packs are often discarded once they reach approximately 70% to 80% of their original capacity.

At this stage, batteries may no longer meet automotive range and performance requirements, but many of their electrodes may still function. The Cornell method is not universally applicable to all batteries. It is most effective when performance degradation is primarily caused by SEI buildup. Batteries with lithium loss, fractured particles, structural damage, or mechanical failures would still necessitate conventional recycling methods.

There are also practical challenges associated with implementing DEER. The electrodes must be disassembled from the battery, processed, and cleaned prior to reuse. Previous attempts to inject the DMI solution directly into intact cells yielded suboptimal results. Consequently, a commercial version of the process would necessitate battery disassembly and stringent handling of electrode materials.

Cornell estimates that recycled cells through DEER could cost $15.25 per kilogram, compared to $26.31 per kilogram for recycling via pyrometallurgy or hydrometallurgy. The estimate does not encompass the recovery of the DMI solution, which accounts for approximately 63% of the process cost. If the method progresses beyond laboratory testing, reusing the DMI solution could enhance the economic viability.

This research emerges as battery recycling companies and researchers seek solutions to manage the increasing supply of aging EV batteries. While many existing methods focus on recovering metals, DEER offers an alternative approach. Instead of discarding a used battery immediately and reducing it to its chemical constituents, DEER aims to salvage the electrode before that step becomes necessary.