Fluorine-Free Binder Paves the Way for Fully Recyclable Lithium-Ion Batteries

Lithium-ion batteries have transformed modern life, powering everything from smartphones to electric vehicles, but the way they are manufactured carries a hidden environmental price. Nearly every commercial battery electrode relies on polyvinylidene fluoride, or PVDF, a fluorinated polymer that glues active materials onto metal foils. Processing PVDF requires N-methyl-2-pyrrolidone, a toxic and expensive solvent, and when batteries reach the end of their lives, the fluorinated binder complicates recycling and leaves behind persistent chemical residues. Now, a team of researchers led by Zheng Chen at the University of California San Diego, working with colleagues at Arizona State University and the Toyota Research Institute of North America, has unveiled a fluorine-free, water-processable polymer binder that matches the performance of PVDF while opening the door to truly circular battery manufacturing. The work, published in Nature Communications, demonstrates that a carefully engineered binder chemistry can deliver high performance during use and complete material recovery at end of life.

The new binder is built from remarkably humble ingredients: polyacrylic acid and carboxymethyl cellulose, two inexpensive and widely available polymers, crosslinked by citric acid, a common food-grade molecule. What makes this combination powerful is not any single component but the architecture of the network they form together. When the binder is cured, the citric acid creates covalent crosslinks between the polymer chains, while the abundant carboxyl groups along the polyacrylic acid backbone engage in hydrogen bonding with one another and form ionic interactions with the active electrode particles and the metal current collectors. The result is a three-dimensional network that integrates hydrogen, covalent, and ionic bonding simultaneously, a design that solves a long-standing problem in sustainable electrode engineering.

Previous attempts to replace PVDF have often turned to bio-derived binders that can be processed in water, an attractive proposition because water eliminates the need for toxic solvents and dramatically reduces processing costs. However, these bio-based alternatives typically depend on hydrogen bonding alone to hold electrodes together. Hydrogen bonds are individually weak and can break down under the mechanical stresses of battery operation or the harsh electrochemical conditions inside a cell, particularly at high voltages where oxidative degradation becomes a threat. The new crosslinked network overcomes this limitation by layering multiple bonding modes on top of one another. The covalent crosslinks provide permanent structural integrity, the hydrogen bonds offer energy dissipation and flexibility, and the ionic interactions anchor the binder firmly to both active particles and current collectors, delivering strong adhesion along with good oxidative stability and thermal stability.

To test the concept, the researchers fabricated positive electrodes using lithium iron phosphate, a cathode chemistry prized for its safety and longevity in electric vehicles and stationary storage. Electrodes made with the fluorine-free binder delivered an initial capacity comparable to control electrodes made with conventional PVDF, meaning the new binder sacrifices nothing in terms of how much energy the battery can store on first use. More strikingly, the fluorine-free electrodes exhibited better cycle stability than their PVDF counterparts, retaining their capacity more effectively over repeated charge and discharge cycles. This improvement likely stems from the robust multi-bond network, which better accommodates the volume changes and mechanical fatigue that electrodes experience during cycling, keeping active material particles connected to the conductive pathways that carry electrons in and out.

The versatility of the binder chemistry proved to be another key strength. The researchers showed that the same fluorine-free formulation applies to a wide range of both positive and negative electrode materials, suggesting that it is not a niche solution tailored to a single chemistry but a general-purpose platform that could be adopted across the battery industry. This breadth matters enormously for commercialization, because battery manufacturers produce many different electrode chemistries for different applications, and a binder that only worked for one material would offer limited value. A single binder system that works across the portfolio of lithium-ion technologies could simplify manufacturing lines and accelerate adoption.

Perhaps the most consequential finding of the study concerns what happens at the end of a battery’s life. Direct recycling, in which spent electrode materials are recovered and rejuvenated rather than broken down into their elemental constituents, is widely regarded as the most energy-efficient and environmentally friendly recycling pathway. Yet PVDF has been a persistent obstacle to direct recycling because its fluorinated structure generates harmful fluorinated residues during processing and complicates the separation of active materials from the binder matrix. The new fluorine-free binder dissolves this problem. Because it is water-processable and free of fluorine, the researchers were able to demonstrate full recovery of spent positive and negative electrodes, restoring the recovered materials to the same level of performance as pristine ones without generating any fluorinated waste.

The implications of this full-recovery demonstration extend beyond the laboratory. When the team performed a life-cycle analysis comparing batteries made and recycled with the new binder against those based on PVDF, the fluorine-free system showed significant reductions in both energy cost and emissions. This analysis captures the entire journey of the materials, from initial manufacturing through use and into recycling, and it reveals that the environmental benefits compound at every stage. Manufacturing in water instead of N-methyl-2-pyrrolidone saves energy and eliminates toxic solvent handling. Recycling without fluorinated residues avoids hazardous waste streams. And because the recovered electrode materials perform identically to pristine ones, they can re-enter the production loop indefinitely, closing the circle that conventional battery manufacturing leaves stubbornly open.

The research also benefited from sophisticated analytical capabilities. The team used beamlines at the National Synchrotron Light Source II, a U.S. Department of Energy Office of Science user facility operated by Brookhaven National Laboratory, to probe the structure and behavior of their binder system at the molecular level. Such advanced characterization is essential for understanding exactly how the hydrogen, covalent, and ionic bonds distribute themselves within the electrode and how they respond to the stresses of battery operation, knowledge that guides further optimization of the formulation. The work was supported in part by the ECS Toyota Young Investigator Fellowship, reflecting the strong automotive industry interest in sustainable battery technologies, and the researchers have filed a patent application related to the technology, a signal that they see a viable path toward commercial deployment.

What makes this advance resonate beyond the technical community is the elegant simplicity of the underlying idea. Rather than inventing exotic new materials, the researchers combined three inexpensive, well-understood substances in a way that exploits the full spectrum of intermolecular interactions. Polyacrylic acid and carboxymethyl cellulose are already produced at industrial scale for applications ranging from diapers to food thickeners, and citric acid is one of the most abundant organic acids in the world. This means the supply chains and processing knowledge needed to manufacture the binder at scale largely already exist, removing one of the most common barriers that laboratory discoveries face on the road to real-world impact.

As the world electrifies transportation and grids, the volume of lithium-ion batteries reaching end of life is projected to grow into the millions of tonnes per year, making recycling infrastructure not just an environmental nicety but an economic and strategic necessity. Binders have long been treated as a minor, almost invisible component of battery design, yet this study demonstrates that they sit at the very heart of the sustainability challenge, dictating how electrodes are made, how they perform, and how easily their valuable contents can be reclaimed. By replacing a fluorinated polymer and a toxic solvent with a water-based, fully recoverable alternative that actually improves cycle life, the researchers have shown that circularity and performance need not be trade-offs. If the technology scales as hoped, the batteries of the future may be born in water, live longer, and return intact to the factory floor, again and again.

Subject of Research: Fluorine-free polymer binders for sustainable manufacturing and direct recycling of lithium-ion battery electrodes

Article Title: Fluorine-free polymer binder enables circular manufacturing and recycling of lithium-ion batteries

Article References: Lin, J., Mu, A., Tang, W., Li, F., Zhu, Y., Li, M., Yeerella, R. H., Potts, C., Cai, S., Mu, L., Muldoon, J., & Chen, Z. (2026). Fluorine-free polymer binder enables circular manufacturing and recycling of lithium-ion batteries. Nature Communications. https://doi.org/10.1038/s41467-026-78215-3

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78215-3

Keywords: lithium-ion batteries, polymer binder, PVDF, recycling, circular economy, water processing, polyacrylic acid, carboxymethyl cellulose, citric acid crosslinking, life-cycle analysis, lithium iron phosphate, sustainability