Flash upcycling of spent LiCoO2 into oxygen-suppressed lithium-replenishing agent for high-performance batteries

Battery recycling is essential to mitigate resource depletion and improve environmental sustainability. However, conventional metallurgical and direct regeneration methods involve trade-offs among energy input, environmental impact, and feedstock adaptability. Here we report a universal upcycling method that converts spent LiCoO2 into Li6CoO4 within 10 seconds via flash Joule heating, achieving complete lithium and cobalt recovery regardless of degradation state. The resulting Li6CoO4 serves as a high-capacity sacrificial additive to offset active lithium loss. To overcome its inherent air sensitivity and oxygen release during delithiation, a conformal sulfur coating was applied to stabilize surface chemistry and redirect oxygen evolution into sulfate formation. This sulfur-mediated mechanism effectively suppresses gas generation and parasitic side reactions, enabling non-destructive lithium replenishment. When integrated into graphite | |LiFePO4 pouch cells, the stabilized Li6CoO4 achieves 91.4% capacity retention over 1400 cycles at a current density of 80 mA g−1. Comparative life-cycle and techno-economic analyses reveal clear reductions in energy consumption and CO2 emissions, along with improved economic returns. This work provides a scalable route that bridges positive electrode waste recovery with high-performance lithium supply, advancing closed-loop battery systems for sustainable energy storage. Spent LiCoO2 batteries pose challenges for sustainable recycling. Here, the authors develop a flash Joule heating method to upcycle spent LiCoO2 into a sulfur-stabilized Li6CoO4 lithium donor, enabling efficient lithium replenishment and improving full-cell durability.