New molten salt method gives old lithium batteries a second life

(Press-News.org) As electric vehicles become more common, the number of used lithium-ion batteries is soaring. These batteries contain valuable metals such as nickel, cobalt, and lithium, but current recycling methods often destroy the complex crystal structure that makes them work efficiently. Now, researchers from Huazhong University of Science and Technology have developed a new molten salt technique that restores the structure and performance of used high-nickel cathode materials, offering a greener and more efficient route to battery recycling.

The study, published in Energy & Environment Nexus, introduces a direct regeneration strategy that uses a special molten salt mixture to repair the degraded cathodes found in end-of-life batteries. Instead of breaking the materials down into metal components as conventional methods do, this approach restores the material itself so it can be reused in new batteries.

“Traditional recycling can recover metals, but it cannot bring back the original atomic structure of the material,” said corresponding author Yang Yang. “Our method allows the degraded cathode to be reborn, regaining its crystal order and high capacity.”

The team focused on LiNi0.8Co0.1Mn0.1O2, or NCM811, a high-performance material widely used in electric vehicles for its high energy density. Over time, NCM811 loses lithium and develops structural defects that reduce its ability to hold charge. To repair these defects, the researchers designed a ternary molten salt composed of lithium hydroxide, lithium nitrate, and lithium salicylate. When heated, the molten salt becomes a liquid that allows lithium ions to move freely and penetrate the damaged material, while also helping the atoms reorganize into their original structure.

Microscopic and spectroscopic analyses showed that the regenerated material had regained a uniform single-crystal structure, with the unwanted surface “rock salt” layer completely removed. The regenerated cathode achieved an initial discharge capacity of 196 milliamp hours per gram and maintained 76 percent of that capacity after 200 charge–discharge cycles, outperforming most existing recycling methods.

“This process effectively heals the internal and surface damage of the cathode material,” said first author Fangshu He. “It not only replaces the lost lithium but also restores the ordered layered structure that is key to long battery life.”

Because the molten salt system works at relatively low temperatures and avoids the use of strong acids or toxic solvents, it is both energy efficient and environmentally friendly. The researchers believe their method could serve as a foundation for closed-loop recycling, where used batteries are directly converted back into high-quality materials for new ones.

Although the current experiments were carried out at the laboratory scale, the team plans to optimize the process for industrial applications and conduct a full life cycle assessment to evaluate its environmental impact. The approach could help reduce both the environmental burden and the cost of recycling, bringing the world closer to sustainable battery production and energy storage.

 

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Journal reference: He F, Lv Y, Wu J, Zhang Q, Hao S, et al. 2025. Molten salt regeneration of single-crystal LiNi0.8Co0.1Mn0.1O2 from end-of-life cathodes. Energy & Environment Nexus 1: e007  https://www.maxapress.com/article/doi/10.48130/een-0025-0004   

 

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About Energy & Environment Nexus:
Energy & Environment Nexus is an open-access journal publishing high-quality research on the interplay between energy systems and environmental sustainability, including renewable energy, carbon mitigation, and green technologies.

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