CORNELL RESEARCHERS RESTORE DISCARDED EV BATTERIES TO 95%

The lithium-ion battery industry has run on a simple logic for three decades: build, use, discard. Spent batteries get smelted at extreme temperatures or crushed into powder and bathed in harsh acids to extract usable materials, then the recovered components get rebuilt from scratch before they can go into a new cell. It is an expensive, polluting, and fundamentally linear process that treats end-of-life batteries as ore to be re-mined rather than components to be renewed.

Cornell University researchers have built a different path. A team led by Vibha Kalra, the Fred H. Rhodes Professor of Chemical Engineering, has developed a recycling technique that restores spent lithium-ion cells to 95% of their original capacity, cutting recycling costs by 56%. The method, called direct electrode-to-electrode regeneration (DEER), avoids the destructive steps entirely: spent electrodes are removed, soaked in an electrochemical solution, and returned directly to a new battery without being broken down.

THE PROBLEM DEER SOLVES

Current battery recycling is expensive and wasteful because it treats every spent cell as a raw material extraction problem rather than a component recovery problem. Smelting requires temperatures that consume significant energy and release emissions. Hydrometallurgy, the alternative, involves shredding batteries and dissolving the resulting powder in acids that require specialized waste handling. In both cases, the recovered materials must be re-synthesized and re-fabricated into new electrodes, adding cost and complexity.

The U.S. lacks domestic infrastructure for this full cycle. Nickel and cobalt for lithium-ion batteries are predominantly imported, and the extraction, refining, and synthesis of electrode materials happens largely overseas. When batteries reach the end of their useful life in EVs—typically at 70 to 80% of original capacity—they either get exported for processing or end up in landfills, where they can leak toxins into surrounding soil and groundwater.

"When these lithium-ion batteries came about, nobody was thinking about how these minerals are limited in the earth's crust, and you cannot make them forever" Kalra said. "In recent years, people are realizing you can't just keep making batteries, because you don't have enough material. And there's obviously a lot of geopolitical vulnerabilities, because the U.S. in particular does not have much of the reserves" The supply chain concentration creates both environmental and national security vulnerabilities that recycling has historically failed to address because the economics never worked at scale.

HOW DEER WORKS

The degradation in a lithium-ion battery centers on a thin layer called the solid electrolyte interphase (SEI), which forms naturally on the electrode surface during charging and discharging. Over time, this layer grows too thick, impeding the movement of lithium ions and reducing the battery's capacity. The SEI is the insulator that steals the battery's life.

DEER targets the SEI directly. Researchers remove the electrodes from a spent cell and soak them in a solution of 1,3-dimethyl-2-imidazolidinone, a solvent that selectively dissolves the degraded SEI layer without damaging the underlying electrode structure. The cleaned electrodes are then reassembled into a new cell with fresh electrolyte. The result is a battery that regains nearly all of its original capacity without any of the material reconstruction that conventional recycling requires.

"We repair them, as is, without shredding or powdering them, and then put them back into a new battery" Kalra said. "The dissolution is basically what helps the battery recover its capacity. It shows 95% recovery. So we are shortening the circularity loop immensely" The 95% figure represents not just capacity restoration but the preservation of the electrode's original structure, meaning the recycled battery performs comparably to a fresh cell.

WHY THE COST MATTERS

The 56% cost reduction comes from eliminating the most expensive steps in conventional recycling. Smelting requires specialized facilities and massive energy input. Hydrometallurgy requires acid-resistant equipment, chemical handling, and waste treatment. Both approaches then need separate synthesis facilities to convert extracted materials back into battery-grade electrodes. DEER replaces all of that with a single solution bath and a reassembly step that uses standard cell manufacturing equipment.

The analysis, conducted in partnership with Argonne National Laboratory's ReCell Center, found that DEER would cut the cost of recycled cell manufacturing by more than half. At that price point, recycled batteries become economically competitive with newly manufactured cells, removing the primary barrier to domestic recycling at scale.

The environmental benefits compound the economic case. By skipping smelting and acid processing, DEER reduces harmful air pollutants and cuts water use significantly. The process produces less waste and requires less energy per restored cell than any existing recycling pathway.

THE TARGETING STRATEGY

DEER is designed for batteries at 70 to 80% state of health, which is exactly when most EV batteries exit the vehicle fleet. "Right now, the spent batteries we are treating have a 70%–80% state of health, which is typical in electric vehicle applications" Kalra said. This is not a method for batteries that have failed entirely; it is a method for batteries that still hold most of their charge but no longer meet the range requirements that EV owners expect.

This targeting is strategic. The batteries that enter the recycling stream today are predominantly from EVs that have been retired not because the cells stopped working but because the pack's total capacity dropped below a usable threshold for transportation. Those cells still contain years of useful energy storage, and redirecting them rather than destroying them creates a secondary market for mid-life batteries that currently has no infrastructure.

WHAT HAPPENS NEXT

The findings, published in Energy & Environmental Science, are currently limited to laboratory-scale demonstration. The next phase involves scaling the process to industrial-sized batteries, which presents challenges in electrode handling, solution circulation, and quality consistency across larger surface areas. The Cornell Atkinson Center for Sustainability is supporting the scale-up work.

The team also plans to address other forms of battery degradation, particularly lithium loss, which occurs when lithium atoms become trapped in side reactions and are no longer available for cycling. The SEI dissolution in DEER recovers the electrode structure, but if lithium has been depleted from the cathode, capacity remains limited. Combining electrode regeneration with lithium replenishment could push recovered capacity beyond the current 95% ceiling.

THE BIGGER PICTURE

If DEER scales, it fundamentally alters the economics and geography of battery supply chains. Instead of relying on imported raw materials and overseas processing, U.S. recyclers could restore domestic batteries using a process that costs roughly half as much as current methods. The circular loop closes faster, cheaper, and cleaner.

The battery industry has treated end-of-life as a disposal problem for too long. DEER reframes it as a refurbishment opportunity, and at 56% less cost with 95% capacity recovery, the math shifts decisively in favor of rebuilding what already works.