Researchers from the University of Birmingham have warned that fluorine-containing materials used in lithium-ion batteries present significant obstacles to the recovery of valuable metals and the development of sustainable recycling processes.
In an article published by the Institute of Materials, Minerals and Mining (IOM3), Dr Lizzie Driscoll MIMMM and PhD student Thomas Petry examined the impact of fluorinated compounds on end-of-life battery treatment.
Fluorine compounds are found throughout lithium-ion batteries, notably in polyvinylidene fluoride (PVDF) binders and lithium hexafluorophosphate (LiPF₆) electrolyte salts. While these materials are essential to battery performance, the researchers said they create problems during recycling.
Pyrometallurgy and hydrometallurgy present fluorine challenges
According to the authors, the two dominant industrial recycling routes – pyrometallurgy and hydrometallurgy – both face challenges arising from fluorinated materials. During high-temperature pyrometallurgical processing, PVDF and LiPF6 decompose to produce fluorocarbons and hydrogen fluoride (HF), a highly toxic and corrosive gas that requires additional off-gas treatment systems.
The researchers noted that LiPF6 can also hydrolyse in the presence of moisture during disassembly and pretreatment, generating HF and phosphoric acid species. Fluoride ions in solution can interfere with precipitation processes and contaminate recovered products, making separation more difficult.
They added that PVDF is insoluble in most aqueous and mild organic solvents, complicating its removal from electrode materials and reducing the purity of recovered cathode active materials.
Driscoll and Petry said these issues have implications for the recovery of critical materials such as lithium, cobalt and nickel.
The article also discussed direct recycling, an emerging approach intended to preserve cathode materials in a higher-value state by restoring lithium inventory rather than breaking the materials down into their constituent elements.
The authors argued that understanding and managing fluorine chemistry will become increasingly important as battery recycling volumes grow and as the industry seeks to establish more efficient and environmentally sustainable closed-loop supply chains.
The work comes as Europe and other regions seek to expand battery recycling capacity to reduce dependence on primary raw materials and meet increasingly stringent recycling targets.
Photo: Dr Lizzie Driscoll MIMMM and PhD student Thomas Petry from the University of Birmingham, UK © Dr Lizzie Driscoll MIMMM and Thomas Petry
