Market and product

Compiled by Bao Hien

Most lithium-ion battery recycling technologies today follow one of two routes: heating batteries to extremely high temperatures (pyrometallurgy) or crushing them into “black mass” and soaking the material in acid to separate the metals (hydrometallurgy). Both approaches consume large amounts of energy, generate pollution, and completely destroy the original electrode structure. A research team in the United States has recently announced a different approach: instead of destroying used electrodes, they directly “repair” them using a chemical solution, restoring up to 95% of the battery’s original capacity.

The Core Problem: A “Rust-Like” Layer Accumulating on the Electrode

As lithium-ion batteries undergo repeated charge-discharge cycles, a thin layer known as the solid electrolyte interphase (SEI) forms and gradually thickens on the electrode surface. This layer initially serves a protective function, but when it becomes excessively thick, it increases electrical resistance and impedes the flow of energy, causing battery capacity to gradually decline over time—even though much of the electrode’s internal physical structure remains intact.

This is the key point exploited by the research team: if capacity loss is primarily caused by the surface layer rather than structural damage, then in theory the battery can be restored by removing that layer alone, instead of destroying the entire electrode and recycling it from scratch.

How It Works: Removing the Electrode, Giving It a “Chemical Bath,” and Reassembling It

The process, known as Direct Electrode-to-Electrode Regeneration (DEER), operates on a relatively simple principle: the intact electrode is removed from a used battery, attached to a current collector, and then immersed in a solution whose main component is 1,3-dimethyl-2-imidazolidinone. The solution can dissolve the degraded SEI layer while leaving behind a thin layer of lithium fluoride that helps stabilize the electrode surface and limit the rapid reformation of an obstructive layer after restoration. Once the “bath” is complete, the electrode is reassembled into a new battery without undergoing crushing or powdering, as in conventional recycling processes.

The method is currently effective for batteries with a state of health of around 70–80%—a common threshold at which electric vehicles are retired and their batteries are removed from the vehicle despite still retaining significant usable value.

Results: Near-Complete Restoration, Even After Multiple Cycles

Test results show that the DEER process can restore up to 95% of the original capacity after the first treatment. More notably, a battery that had reached its “third life”—meaning it had previously been restored once and then used again until its performance declined—still retained around 90% of its capacity after a second restoration, indicating that the process can be repeated multiple times without a rapid loss of effectiveness.

From an economic perspective, the research team, working with a techno-economic analysis center at a U.S. Department of Energy national laboratory specializing in battery recycling, estimates that the cost of producing each battery cell using this method is approximately 56% lower than that of conventional recycling processes. The method also significantly reduces emissions and water consumption during processing.

No Need to Ship Batteries Overseas for Recycling

Another advantage emphasized by the research team is the possibility of recycling batteries locally. The lead researcher described the philosophy behind the approach: “We repair them in their original form, without crushing or powdering them, and then turn them back into a new battery.” This approach could eliminate the need to transport waste batteries overseas for further metal refining—a costly step that generates significant emissions in today’s battery recycling supply chain, which relies heavily on large-scale metallurgical facilities concentrated in a number of countries.

Current Limitations and Next Steps

The DEER method effectively addresses degradation caused by the accumulation of the SEI layer, but this is not the only factor responsible for the deterioration of lithium-ion batteries over time. The research team says the next step is to expand testing to larger, industrial-scale batteries while also finding ways to address other degradation mechanisms, such as the permanent loss of lithium during use, which the current process cannot yet reverse. These factors will determine whether this “chemical bath” technology can move beyond the laboratory and become a commercially viable option for the electric-vehicle battery recycling industry.