Temperature-Potential Coupled Regulation of LiPF₆ Decomposition to Construct LiF Grain Boundary-Rich Interphase on...

Regulating the electrolyte decomposition to evolve a LiF-rich solid-electrolyte interphase (SEI) can reduce the energy barrier of the interfacial Li-ion transport toward fast-charging lithium-ion batteries. Due to the sluggish decomposition kinetics, LiPF₆, as a widely used Li salt in commercial cells, is unable to build a LiF-rich SEI. Therefore, expensive fluorinated electrolyte additives are needed. Herein, to eliminate the use of extra fluorinated species, based on the subtle electrochemical decomposition of LiPF₆ occurring ∼2.28 V vs. Li⁺/Li at 80°C, we developed a temperature-potential coupled formation (TPCF) protocol, which incorporates a constant-voltage step (2.28 V) at 80°C to stimulate LiPF₆ decomposition deeply, thereby generating a high-quality SEI uniformly covering the graphite particle surfaces. This TPCF-derived SEI is thin and dense, full of LiF grain boundaries, which could reduce the energy barriers of Li⁺ desolvation and interfacial Li⁺ diffusion. Simultaneously, this SEI exhibits a higher work function, effectively suppressing electron leakage to reduce the degeneration of the electrolyte and interphase. Consequently, after a simple TPCF process, the assembled graphite||LiFePO₄ full cell achieves stable cycling at a 6C rate, retaining 80% of its capacity after 3304 cycles and 70.5% after 8940 cycles, outperforming the counterparts.