One-pot compositional and structural regeneration of degraded LiCoO2 for directly reusing it as a high-performance lithium-ion battery cathode

Abstract

Recycling spent cathodes from Li-ion batteries (LIBs) is an appealing route to address environmental issues and resource shortage, but is plagued by effective and simple recycling techniques. Current recycling technologies generally involve multi-steps such as acid leaching, precipitation, smelting, or solid-state sintering, and obtained products possess inferior electrochemical properties. The current work explores a new regeneration method for failed LiCoO₂ cathode material. The electrochemical performance of LiCoO₂ is fully recovered through a single thermal-chemical treatment of spent LiCoO₂ in molten LiOH–KOH–Li₂CO₃ under air atmosphere. The molten salt mixture presents suitable dissolving capacity, homogeneous thermal circumstance, abundant Li⁺, and high ion diffusion rate to decompose impurities, compensate for Li⁺ deficiency, and repair damaged structure through a “dissolution-recrystallization” mechanism. Under the optimized reaction temperature of 500 °C, the regenerated LiCoO₂ possessed similar stoichiometric composition and crystalline structure of commercial LiCoO₂. Importantly, the discharge capacity of spent LiCoO₂ was recovered from 68.3 mA h g⁻¹ to 144.5 mA h g⁻¹, reaching the original level of commercial LiCoO₂. Besides, the regenerated LiCoO₂ also delivered superior cycling of 92.5% capacity retention after 200 cycles and excellent rate performance. This work presents an effective and extendable approach to regenerate spent cathode materials to retrieve their electrochemical performance.