Separation of cathode particles and aluminum current foil in lithium-ion battery by high-voltage pulsed discharge Part II: Prospective life cycle assessment based on experimental data

Chemical speciation changes of an all-solid-state lithium-ion battery caused by roasting determined by sequential acid leaching

All-solid-state lithium-ion batteries (ASS-LIBs) are expected to replace current liquid-based LIBs in the near future owing to their high energy density and improved safety. It would be preferable if ASS-LIBs could be recycled by the current recycling processes used for liquid-based LIBs, but this possibility remains to be determined. Here, we subjected an ASS-LIB test cell containing an argyrodite-type solid electrolyte (Li6PS5Cl) and nickel-manganese-cobalt-type active material (Li(Ni0.5Mn0.3Co0.2)O2) to roasting, a treatment process commonly used for recycling of the valuable metals from liquid-based LIBs, and investigated the changes in chemical speciation. Roasting was performed at various temperatures (350-900 °C), for various times (60-360 min), and under various oxygen fugacity (air or O2) conditions. The chemical speciation of each metal element after roasting was determined by sequential elemental leaching tests and X-ray diffraction analysis. Li formed sulfates or phosphates over a wide temperature range. Ni and Co followed very complicated reaction paths owing to coexistence of S, P, and C, and they formed sulfides, phosphates, and complex oxides. The optimum conditions for minimizing formation of insoluble compounds, such as complex oxides, were a roasting temperature of 450-500 °C and a roasting time of 120 min. The results indicated that although ASS-LIBs can be treated by the same roasting processes as those used for current liquid-based LIBs, the optimal roasting conditions have narrow ranges. Thus, careful process control will be needed to achieve high extraction percentages of the valuable metals from ASS-LIBs.

Challenges in Recycling Spent Lithium-Ion Batteries: Spotlight on Polyvinylidene Fluoride Removal

In the recycling of retired lithium-ion batteries (LIBs), the cathode materials containing valuable metals should be first separated from the current collector aluminum foil to decrease the difficulty and complexity in the subsequent metal extraction. However, strong the binding force of organic binder polyvinylidene fluoride (PVDF) prevents effective separation of cathode materials and Al foil, thus affecting metal recycling. This paper reviews the composition, property, function, and binding mechanism of PVDF, and elaborates on the separation technologies of cathode material and Al foil (e.g., physical separation, solid-phase thermochemistry, solution chemistry, and solvent chemistry) as well as the corresponding reaction behavior and transformation mechanisms of PVDF. Due to the characteristic variation of the reaction systems, the dissolution, swelling, melting, and degradation processes and mechanisms of PVDF exhibit considerable differences, posing new challenges to efficient recycling of spent LIBs worldwide. It is critical to separate cathode materials and Al foil and recycle PVDF to reduce environmental risks from the recovery of retired LIBs resources. Developing fluorine-free alternative materials and solid-state electrolytes is a potential way to mitigate PVDF pollution in the recycling of spent LIBs in the EV era.