Synergistic regulation strategy: NiO/g-C3N4 promoting efficient prelithiation of Li2C2O4

Particle-size engineering, conductive-network construction and catalysis were integrated. • Recrystallization and ball milling reduced Li 2 C 2 O 4 D50 from 142.8 to 0.55 μm. • A NiO/g-C 3 N 4 composite catalyst promoted Li 2 C 2 O 4 activation. • The decomposition potential decreased from 4.805 to 4.254 V. • The bilayer electrode delivered 267.49 mAh·g −1 additional capacity. Lithium oxalate is regarded as a promising cathode prelithiation additive for compensating irreversible active lithium loss during the initial cycle of lithium-ion batteries, owing to its high theoretical specific capacity, good air stability, and low cost. However, its intrinsically low electrochemical activity and high decomposition potential severely limit its practical application. Herein, a synergistic regulation strategy combining particle-size refinement, conductive-network construction, and NiO/g-C 3 N 4 catalyst modification was developed to promote the electrochemical activation of Li 2 C 2 O 4 . The reduced particle size shortens Li  +  transport pathways, while Ketjen black constructs an efficient conductive network and the NiO/g-C 3 N 4 composite catalyst promotes the electrochemical activation of Li 2 C 2 O 4 . As a result, the decomposition potential of Li 2 C 2 O 4 was reduced from 4.805 to 4.254 V, while a high discharge capacity of 510.2 mAh·g −1 was maintained. When applied in LiFePO 4 half-cells using a bilayer electrode configuration, the optimized prelithiation layer delivered an additional specific capacity of 267.49 mAh·g −1 without compromising cycling stability. This work provides a feasible strategy for improving the electrochemical utilization of Li 2 C 2 O 4 and demonstrates its potential as an efficient cathode prelithiation additive for lithium-ion batteries.