Temperature‐Potential Coupled Regulation of LiPF ₆ Decomposition to Construct LiF Grain Boundary‐Rich Interphase on Graphite Anode for Fast‐Charging Li‐Ion Batteries

Abstract

ABSTRACT 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, LiPF 6 , 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 LiPF 6 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 LiPF 6 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||LiFePO 4 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.