US team succeeds in recovering nearly pure lithium from used batteries

A team in Massachusetts has recovered lithium carbonate at 99.79 percent purity from spent lithium metal battery anodes. The process uses a controlled reaction in commercial acetone and was demonstrated by researchers at Worcester Polytechnic Institute.

The same group also reports a solid electrolyte tweak that improves contact at the anode side of next generation batteries. The approach, iron doping in lithium indium chloride, is described in a recent report.

Recycling lithium from batteries

The work was led by Yan Wang, William B. Smith Foundation Professor at Worcester Polytechnic Institute (WPI). His research focuses on industrial scale battery recycling and safer solid state materials.

Spent lithium metal anodes are hard to handle because they form dendrites, tiny needle like deposits that increase surface area and reactivity. Those dendrites can ignite reactions that are too fast to control in a recycling tank.

Many lab treatments rely on water or alcohols, which hit fresh lithium and release heat and hydrogen gas. Those protic solvents, molecules that donate hydrogen ions in reactions, can push the system toward thermal runaway if you scale them up.

So the obstacle has never been chemistry alone. It is the safety of converting a reactive metal into a useful salt without a violent step.

This is where a careful choice of solvent and a slow first reaction stage becomes important. A measured route lowers risk while still pushing the anode toward stable products.

Acetone route tames the risk

The team used acetone with a trace of water so the first reaction forms a thin layer of lithium hydroxide on the spent anode. That step eats away at the sharp dendrites and calms the surface.

Lithium hydroxide then triggers aldol condensation, a base catalyzed reaction that links small carbonyl molecules into bigger ones, inside the acetone.

The product, diacetone alcohol, reacts with remaining lithium at a controlled rate that keeps temperatures manageable.

All lithium ends up as lithium hydroxide and a lithium alkoxide that hydrolyzes cleanly. The final product is lithium carbonate, a common battery precursor salt with strict purity requirements in industry.

Quality mattered as much as safety. The recovered salt was used to make fresh cathode material that delivered capacities on par with material made from commercial reagents.

Lithium supply from old batteries

Battery makers typically specify battery-grade, lithium carbonate at about 99.5 percent purity, with low ppm level metal and ion contaminants, which sets a clear bar for recycled inputs. Hitting that bar with material pulled from spent anodes is a meaningful shift for supply chains.

The WPI method reached the threshold and exceeded it. That makes the salt suitable for established cathode recipes without extra clean up steps that raise costs.

Scale and economics also matter to adoption. In the reported trials, the team processed grams of anode feed, recovered most of the lithium as carbonate, and estimated a favorable cost balance once acetone is recovered and reused.

Environmental accounting moved in the right direction. Lower energy use per kilogram of product and smaller greenhouse gas numbers point to a recycling step that can be squared with factory operations.

Fixing a stubborn problem

Solid state batteries replace flammable liquid with a solid electrolyte, but halide salts often react at the anode side.

Recent evidence, simulations and experiments probing halide electrolytes against lithium metal, has mapped out the interfacial products that can form and why stability is hard to achieve.

To cut through that impasse, the WPI team modified a lithium indium chloride electrolyte with iron. The iron doped material forms direct, stable contact with a lithium indium anode, so no extra protective layer is needed.

In long running tests, full cells held strong capacity over hundreds of cycles, and symmetric cells ran for hundreds of hours without degrading.

Those figures are meaningful because they speak to both interfacial chemistry and bulk ionic conductivity.

“This work establishes iron doping as an effective strategy to simplify solid state battery design while enhancing stability and performance,” said Wang.

What the chemistry means

Taken together, these results connect the first and last acts of a battery’s life. A safer route to neutralize and recover lithium can feed new cathode production without stepping outside current factory windows.

The interface advance trims a part count that has slowed solid state designs. Dropping an interlayer removes cost and reduces failure points that come from mismatched materials.

There is a practical rhythm to both steps. The recycling chemistry leverages diacetone alcohol, a low concentration intermediate formed in acetone, to keep reaction rates steady and temperatures low.

On the device side, holding contact without a sacrificial barrier signals better long term mechanical fit. It means less creeping resistance where metal meets the solid electrolyte over time.

Lithium lessons from old batteries

Electric vehicles need high energy and high safety. Lithium metal anodes promise more miles per charge, but they bring handling and recycling risks that must be addressed before they scale.

A safe path to recover battery grade lithium from those anodes cuts reliance on new mining. That helps stabilize input costs and reduces the environmental footprint of pack manufacturing.

Compatibility progress at the anode interface, even with a lithium indium alloy counter, moves solid state cells closer to real world duty cycles. It suggests pathways that may translate to direct lithium metal operation with careful engineering.

Technical hurdles remain as designs shift from test cells to large formats. The reported results mark steps that give manufacturers room to simplify builds and close material loops with less waste.

The study is published in Joule.

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