Ethylene Carbonate Free Sulfone‐Based Electrolyte for Enabling Superior Performance of High Ni‐containing Li‐Transition Metal Oxide Cathodes at High Voltage and High Temperature

Abstract The present study introduces an ethylene carbonate (EC) free electrolyte, composed of 1 M LiPF₆ in ethyl methyl sulfone (EMS) and dimethyl carbonate (DMC) (3 : 7 by volume), for Li‐ion batteries, which is better suited for usage with higher upper cut‐off potentials, with high Ni‐containing ‘layered’ Li‐ transition metal oxide cathodes (like Li−NMC811), and at elevated temperature. The as‐designed and developed sulfone‐based electrolyte exhibits superior anodic stability and lower electrolyte resistance, while suppressing the decomposition of LiPF₆ and facilitating the formation of a S‐containing, more passivating, thinner and uniform CEI layer on Li−NMC811, despite the usage of a high upper cut‐off potential of 4.5 V (vs. Li/Li⁺). Compared with conventional EC‐based electrolyte, the sulfone‐based electrolyte results in notably suppressed rise in impedance and improved cyclic‐stability, with capacity retentions of ~87 % (vs. ~78 % for EC‐based electrolyte) after 50 cycles @ C/10 at room temperature (going up to 4.5 V). Even at 45 °C, the sulfone‐based electrolyte results in significantly higher initial Coulombic efficiency (viz., >80 % vs. ~40 %), higher reversible capacity (~230 mAh/g vs. ~178 mAh/g) and superior cyclic stability (~74 % vs. ~46 % retention after 50 cycles @ C/10); thus, revealing its superiority for usage at elevated temperature.