Unleash the Capacity Potential of LiFePO4 through Rocking‐Chair Coordination Chemistry

Abstract

AbstractThere is still a considerable gap between the actual and theoretical capacities of the commercial cathode material LiFePO4 (LFP) for lithium‐ion batteries (LIBs). Here, a new strategy to release the full capacity of LFP through the rocking‐chair coordination chemistry is reported. Specifically, the zinc acetate‐diethanolamine complex (Zn(OAc)2·DEA) is used as a functional binder for the LFP cathode, where the N atom of DEA can coordinate with Zn2+, Fe2+, or Fe3+. The bond strength sequence is Fe3+–N > Zn2+–N > Fe2+–N, which makes the N atom swing between Fe3+ on the surface of FePO4 in the charged state and Zn2+ of Zn(OAc)2 in the discharged state. Density functional theory simulations reveal that the adsorption of DEA reduces the surface bandgap and the energy barriers of Li+ diffusion along the [010] direction of LFP, which promotes electronic conduction and Li+ diffusion, respectively. The Zn(OAc)2·DEA‐based LFP electrode achieves a high capacity of 169 mAh g−1 at 0.2C, which approaches the theoretical value of 170 mAh g−1. The electrode also has excellent cycling performance, showing a low capacity decay rate of 0.03% per cycle over 1500 cycles at 5C.