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.