Recovery and Reuse of Composite Cathode Binder in Lithium Ion Batteries

Lithium-ion battery recycling: a source of per- and polyfluoroalkyl substances (PFAS) to the environment?

Recycling of lithium-ion batteries (LIBs) is a rapidly growing industry, which is vital to address the increasing demand for metals, and to achieve a sustainable circular economy. Relatively little information is known about the environmental risks posed by LIB recycling, in particular with regards to the emission of persistent (in)organic fluorinated chemicals. Here we present an overview on the use of fluorinated substances - in particular per- and polyfluoroalkyl substances (PFAS) - in state-of-the-art LIBs, along with recycling conditions which may lead to their formation and/or release to the environment. Both organic and inorganic fluorinated substances are widely reported in LIB components, including the electrodes and binder, electrolyte (and additives), and separator. Among the most common substances are LiPF6 (an electrolyte salt), and the polymeric PFAS polyvinylidene fluoride (used as an electrode binder and a separator). Currently the most common LIB recycling process involves pyrometallurgy, which operates at high temperatures (up to 1600 °C), sufficient for PFAS mineralization. However, hydrometallurgy, an increasingly popular alternative recycling approach, operates under milder temperatures (<600 °C), which could favor incomplete degradation and/or formation and release of persistent fluorinated substances. This is supported by the wide range of fluorinated substances detected in bench-scale LIB recycling experiments. Overall, this review highlights the need to further investigate emissions of fluorinated substances during LIB recycling and suggests that substitution of PFAS-based materials (i.e. during manufacturing), or alternatively post-treatments and/or changes in process conditions may be required to avoid formation and emission of persistent fluorinated substances.

Novel strategy towards in-situ recycling of valuable metals from spent lithium-ion batteries through endogenous advanced oxidation process

Efficient and sustainable recycling of metal resources from spent lithium-ion batteries (LIBs) is critical for the metal resources security and environment protection. However, the intact exfoliation of cathode materials (CMs) from current collectors (Al foils) and selective extraction of Li towards the in-situ and sustainable recycling of cathodes from spent LIBs are still pending issues. A self-activated and ultrasonic-induced endogenous advanced oxidation process (EAOP) was proposed in this study for selective removal of PVDF and in-situ extraction of Li from CMs of waste LiFePO₄ (LFP) to address the above issues. Over 99 wt% CMs can be detached from Al foils after EAOP treatment under the optimized operation conditions. High purity of Al foil can be directly recycled as metallic forms and nearly 100 % of Li can be in-situ extracted from the detached CMs and then recovered as Li₂CO₃ (>99.9 % in purity). With induction and reinforcement of ultrasonic, S₂O₈^2- was self-activated by LFP to generate an increased amount of SO₄^•- radicals that will attack the PVDF binders to ensure their degradation. The degradation pathway of PVDF and density functional theory (DFT) calculation can also support the analytical and experimental results. Then, the complete and in-situ ionization of Li can be achieved by the further oxidization of SO₄^•- radicals from LFP powders. This work provides a novel strategy towards efficient and in-situ recycling of valuable metals from spent LIBs with minimized environmental footprint.

A sustainable approach to cathode delamination using a green solvent

Designing an environment-friendly delamination process for an end-of-life (EoL) composite cathode is a crucial step in direct cathode recycling. In this study, the green solvent dimethyl isosorbide (DMI) is explored to extract cathode active materials (AMs) from the Al current collector via dissolving the polyvinylidene fluoride (PVDF) binder. Mechanistic insight suggests that binder removal from the Al substrate proceeds via reducing polymer interchain interaction through DMI penetrating into the PVDF crystalline region. Polymer–solvent interaction may increase via establishing hydrogen bond between PVDF and DMI, which facilitates binder removal. Analytical characterizations including ¹H NMR, FTIR, XRD and SEM-EDS reveal that the molecular, micro, and crystal structures of the recovered cathode AMs, PVDF and Al foil are preserved. This finding is expected to provide a replacement for the toxic organic solvent N-methylpyrrolidone (NMP) and offers an effective, ecofriendly, and sustainable direct cathode recycling approach for spent Li-ion batteries.

A green solvent-based methodology was developed for delaminating cathode active materials from aluminium current collectors in end-of-life Li-ion batteries.