A Rapid Chemical Relithiation Method Using Solvated Electrons for the Direct Recycling of Lithium-ion Battery Cathodes

Due to the increasing adoption of electric vehicles, there is an imminent surge in waste lithium-ion batteries which will intensify resource depletion, environmental concerns, and supply chain vulnerability. Direct recycling is an energy-efficient, environmentally friendly solution that nondestructively regenerates spent cathode active material, bypassing downstream cathode resynthesis from raw materials and securing critical minerals within the supply chain to meet growing battery demand while mitigating battery waste. Here we present a rapid solution-phase relithiation mechanism, inspired by Birch reduction chemistry, for the direct regeneration of spent LiNi0.5Mn0.3Co0.2O2 active material. Our method addresses limitations of direct recycling related to process intensity and scalability. A highly stable solvated electron solution, composed of pure Li metal and condensed liquid ammonia, efficiently delivers electrons to oxidized transition metals and supplies Li ions to vacancies within the crystal lattice, replenishing stoichiometric Li content. After a short annealing, the regenerated cathode material exhibits a restored bulk and near-surface crystal structure. The regenerated material demonstrates enhanced electrochemical performance relative to the pristine material when cycled to 4.3 V (159.49 mAh/g and 94.10% capacity retention after 100 cycles), highlighting its strong long-term cycling stability. Our system demonstrates the successful application of solvated electrons for efficient, sustainable battery recycling.