UC San Diego and Toyota Develop Water-Soluble Binder to Simplify Battery Manufacturing and Recycling

Engineers at the University of California San Diego and the Toyota Research Institute of North America have developed a fluorine-free, water-soluble battery binder that eliminates toxic processing solvents and simplifies recycling for lithium-ion batteries. Details of the research, led by UC San Diego nanoengineering professor Zheng Chen and Toyota researcher John Muldoon, were published Oct. 9 in Nature Communications and reported by TechXplore (https://techxplore.com/news/2026-10-binder-battery-recycling-sacrificing.html).

Binders act as the internal adhesive in lithium-ion cells, bonding powdered active materials together and sticking them to metallic current collector foils. While binders constitute only a small fraction of a battery's mass, standard commercial cells rely on fluorine-containing polymers to maintain adhesion and chemical stability across repeated cycling. That fluorinated chemistry requires hazardous organic solvents during manufacturing and leaves persistent chemical residues that demand corrosive agents or high-temperature processing during recycling.

To replace fluorinated binders, the team synthesized a water-soluble alternative using two common polymers: polyacrylic acid for slurry spreadability and flexibility, and plant-derived carboxymethyl cellulose for mechanical cohesion. The researchers dissolved both polymers in water and added citric acid as a cross-linking agent, producing a reinforced chemical network with structural durability and adhesion comparable to fluorinated counterparts.

In laboratory testing, prototype cells built with the new binder matched the initial capacity of conventional lithium-ion batteries and retained capacity longer across hundreds to thousands of charge and discharge cycles. The formulation demonstrated compatibility across multiple chemistry configurations, including lithium iron phosphate (LFP) cathodes, nickel-rich cathodes, graphite anodes, and silicon-based anodes.

The binder also streamlined direct recycling in bench tests. Soaking spent electrodes in water dissolved the binder cleanly, allowing active electrode layers to detach from collector foils without residual fluorinated contamination. Reprocessed materials were then used to build new cells that performed on par with batteries restored from conventional fluorinated assemblies. The researchers plan to scale production and partner with industrial manufacturers to commercialize the material.