Electronic‐State Engineering of Transition Metals Regulates Decomposition Kinetics of Li 2 C 2 O 4 for Cathode Prelithiation

Lithium oxalate (Li 2 C 2 O 4 ) is a promising cathode prelithiation reagent but suffers from a high activation voltage (>4.6 V). Herein, we establish a component–electronic structure–activity correlation by constructing a series of transition metal‐loaded N,S co‐doped carbon catalysts (M/NSC, M = Fe, Co, Ni, Ru, Rh, Ir). Distinct catalytic behaviors originate from metal‐dependent electronic structures and their interactions with N/S co‐doped carbon. Interestingly, the Fe‐group metals exhibit stronger electronic coupling and higher redox flexibility than 4d/5d noble metals, resulting in more effective activation of Li 2 C 2 O 4 . The Co/NSC achieves the lowest decomposition voltage (4.17 V), attributed to uniform Co dispersion, optimized Co–N/S coordination, and defect‐induced charge‐transfer enhancement. The Co/NSC–Li 2 C 2 O 4 composite ensures nearly complete decomposition and delivers superior prelithiation performance. When applied to commercial LFP and NCM9055 cathodes, the Gr|| LiFePO 4 system shows a 22% capacity increase, meanwhile the Gr/SiC||NCM9055 cell achieves an initial coulombic efficiency (ICE) enhancement from 77% to 85.6%. This work highlights electronic–structure engineering as an effective strategy for enabling practical lithium compensation in high‐energy lithium‐ion batteries.