Electronic-State Engineering of Transition Metals Regulates Decomposition Kinetics of Li2C2O4 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. Graphical Unlocking the structure–activity relationship of Li 2 C 2 O 4 prelithiation: uniformly dispersed Co nanoparticles on N,S co-doped carbon creates abundant active sites, Co–N/Co–S coordination modulates electronic structure, and defect-rich carbon ensures fast charge transfer. These structural advantages reduce decomposition voltage to 4.17 V and exhibit a capacity enhancement of 22%.