High-Efficiency Strategy for Reducing Decomposition Potential of Lithium Formate as Cathode Prelithiation Additive...

Lithium-ion batteries (LIBs) have attracted extensive attention as a distinguished electrochemical energy storage system due to their high energy density and long cycle life. However, the initial irreversible lithium loss during the first cycle caused by the formation of the solid electrolyte interphase (SEI) leads to the prominent reduction in the energy density of LIBs. Notably, lithium formate (HCOOLi, LFM) is regarded as a promising cathode prelithiation reagent for effective lithium supplementation due to its high theoretical capacity of 515 mAh·g^-1. Nevertheless, the stable Li-O bond of LFM brings out the high reaction barrier accompanied by the high decomposition potential, which impedes its practical applications. To address this issue, a feasible strategy for reducing the reaction barrier has been proposed, in which the decomposition potential of LFM from 4.84 V to 4.23 V resulted from the synergetic effects of improving the electron/ion transport kinetics and catalysis of transition metal oxides. The addition of LFM to full cells consisting of graphite anodes and LiNi_0.834Co_0.11Mn_0.056O₂ cathodes significantly enhanced the electrochemical performance, increasing the reversible discharge capacity from 156 to 169 mAh·g^-1 at 0.1 C (2.65-4.25 V). Remarkably, the capacity retention after 100 cycles improved from 72.8% to 94.7%. Our strategy effectively enables LFM to serve as an efficient prelithiation additive for commercial cathode materials.