Microwave carbothermal activation enables closed-loop recycling of spent Ni-rich NCM cathode materials via leachate-to-cathode resynthesis

With the widespread use of Ni-rich layered oxides in traction lithium-ion batteries, the efficient recycling and high-value regeneration of spent Ni-rich cathode materials have become a key issue in lithium-ion battery recycling. To bridge valuable-metal extraction and functional-material remanufacturing, this study developed a closed-loop recycling process that combines microwave carbothermal activation, ultrasound-assisted citric acid leaching, and sol-gel resynthesis to regenerate spent Ni-rich NCM cathode materials into layered LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). After 10 min of microwave carbothermal activation, the spent cathode oxide was converted into highly reactive Li-containing and transition-metal phases; in the subsequent ultrasound-assisted citric acid leaching, the leaching efficiencies of Li, Ni, Co, and Mn reached 98.81-99.84%. After composition adjustment, the resulting mixed-metal leachate was used directly for NCM811 resynthesis without individual separation of Ni, Co, and Mn. The cathode resynthesized from the leachate (RS-NCM) delivered an initial discharge capacity of 191.7 mAh g^-1 at 0.1 C, with capacity retentions of 83.4% after 100 cycles at 0.2 C and 70.7% after 200 cycles at 1 C. Compared with a reference material synthesized directly from reagent salts, RS-NCM maintained higher discharge capacities during cycling at 0.2 C and exhibited better rate capability. These results demonstrate that coupling microwave activation with the direct remanufacturing of mixed-metal leachate enables closed-loop regeneration of spent Ni-rich NCM cathode materials without individual separation of Ni, Co, and Mn, providing an experimental basis for simplifying the recycling and remanufacturing of Ni-rich cathode materials.