LiNO3-driven anion-rich solvation and interphase chemistry for high-performance low-temperature LiFePO4||Graphite batteries

Achieving fast ion transport and stable interfacial chemistry at low temperatures through electrolyte design remains a major challenge for commercial LiFePO 4 ||Graphite (hereafter referred to as LFP||Gr) lithium-ion batteries (LIBs). Herein, a weakly solvating ester-based electrolyte is formulated using ethyl acetate (EA), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and dimethoxyethane (DME) with bis(trifluoromethanesulfonyl)imide (LiTFSI) and a LiNO 3 additive. Compared to systems employing large amounts of fluorinated solvents or high-concentration electrolytes, the solvent cost is reduced by using low-cost ester-based primary solvents. The tailored solvent environment promotes an anion-rich primary solvation sheath, which is conducive to promoting the formation of an inorganic-rich interfacial film on graphite anode surface, dominated by LiF and nitrogen-containing species, and lower the Li + desolvation energy barrier, resulting in accelerated interfacial Li + transport kinetics and enhanced graphite/electrolyte interfacial stability at low temperatures. As a result, the designed electrolyte shows excellent compatibility with both LiFePO 4 and graphite from ambient to low temperatures and provides enhanced rate capability relative to conventional carbonate electrolytes. High-mass-loading LFP||Gr full cells employing the designed electrolyte deliver 131.8 mAh g −1 at 2 C at ambient temperature and maintain 128 mAh g −1 at −30 °C, significantly surpassing the performance of cells with conventional carbonate-based electrolytes (12.7 and 108 mAh g⁻¹, respectively). This work provides a practical way to achieve commercial high-rate low-temperature graphite-based LIBs by regulating electrolyte solvation structure and the electrode/electrolyte interfacial structure. Download: Download high-res image (245KB) Download: Download full-size image