Interfacial Catalytic Activation of Li 2 C 2 O 4 for Efficient Cathode Prelithiation in Lithium‐Ion Batteries

Lithium oxalate (Li 2 C 2 O 4 ) 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 Li 2 C 2 O 4 results in a high decomposition potential. Herein, the interfacial decomposition behavior of crystalline Li 2 C 2 O 4 is systematically investigated. Theoretical calculations reveal that the NiCo 2 O 4 Li 2 C 2 O 4 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 NiCo 2 O 4 @Li 2 C 2 O 4 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 LiFePO 4 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 Li 2 C 2 O 4 decomposition and demonstrates an efficient cathode‐side prelithiation strategy for improving the lithium inventory and cycling durability of silicon‐based lithium‐ion batteries.