Interfacial Catalytic Activation of Li₂C₂O₄ for Efficient Cathode Prelithiation in Lithium-Ion Batteries

Lithium oxalate (Li₂C₂O₄) attracts increasing attention as a cathode sacrificial prelithiation agent due to its high theoretical capacity, excellent air stability, residue-free decomposition, and good compatibility with present battery chemistry. However, the sluggish decomposition kinetics of crystalline Li₂C₂O₄ results in a high decomposition potential. Herein, the interfacial decomposition behavior of crystalline Li₂C₂O₄ is systematically investigated. Theoretical calculations reveal that the NiCo₂O₄Li₂C₂O₄ interface substantially lowers the relative energies of key defect-containing intermediates and reduces the energetic penalty for the rate-determining Li⁺ extraction step. Guided by this mechanism, a composite NiCo₂O₄@Li₂C₂O₄ prelithiation agent (NCO@LCO) is prepared by a facile freeze-drying strategy. Benefiting from abundant catalytic interfaces, NCO@LCO exhibits accelerated decomposition kinetics, with the decomposition potential reduced from 4.45 to 4.24 V. When applied to a LiFePO₄ cathode through a secondary coating process and paired with a Si/C-Gr anode, NCO@LCO provides additional active lithium during the first charge, increases the first-cycle reversible capacity, and markedly improves long-term cycling stability. This work provides a crystal-interface perspective for Li₂C₂O₄ decomposition and demonstrates an efficient cathode-side prelithiation strategy for improving the lithium inventory and cycling durability of silicon-based lithium-ion batteries.