Synchronous pre-lithiation at 3.5 V from lithium oxalate via micro-galvanic cells in LiFePO4 batteries

The limited cycle life of LiFePO 4 (LFP) batteries, caused by irreversible lithium loss, necessitates innovative pre-lithiation strategies. Commercial lithium oxalate (Li 2 C 2 O 4 , CLCO) offers high lithium compensation capacity (3000 mAh/g) but faces a practical decomposition potential mismatch, exceeding LFP's operational limit (4.2 V). Here, the persistent challenge of high-voltage decomposition of cathode pre-lithiation additives (>4.8 V vs. Li/Li + ) is addressed through a micro-galvanic coupling strategy between CLCO and FePO 4 in the delithiated LFP cathodes. By engineering particle size matching and enhancing interfacial charge transport via cathode calendaring, we amplify the inherent but underutilized CLCO│FePO 4 micro-galvanic effect. This system achieves voltage-synchronized pre-lithiation at 3.5 V during initial charging, where FePO 4 oxidizes Li 2 C 2 O 4 to release 28.11 mAh·g −1 lithium ions while regenerating LiFePO 4 through electron transfer—effectively circumventing high-voltage electrolyte decomposition. Meanwhile, CO 2 byproducts stabilize the solid electrolyte interphase, while decomposition-induced nanopores enhance electrolyte infiltration, boosting rate capability by 40 % at 2C. Impressively, the CLCO pre-lithiated LFP-graphite full cell delivers 154.73 mAh·g −1 initial capacity (22.2 % enhancement vs. control group) with 70.01 % retention after 800 cycles, outperforming conventional configuration (40.26 % after 400 cycles). This voltage-compatible, catalyst-free strategy establishes a scalable pathway for lithium compensation in practical batteries.