Stabilization of high-voltage lithium metal batteries using a sulfone-based electrolyte with bi-electrode affinity and LiSO2F-rich interphases

Abstract

High-voltage cathodes paired with lithium metal anode have aroused extensive interests owing to their application potentials for high-density energy storage. Nevertheless, conventional electrolytes fail to maintain the stability of high-voltage cathodes and Li anode, due to their rigid interfacial chemistry with low adsorption of transition metal and strong bonding with Li+ ions. These inadequate interactions exacerbate issues such as transition metal dissolution and non-uniform Li+ transference, ultimately resulting in low cyclability of high-voltage lithium metal batteries (HVLMBs). By incorporating fluoroethylene carbonate (FEC) into lithium bis(trifluoromethane sulfonyl) imide (LiTFSI)/tetramethylene sulfone (TMS) solution, we design a sulfone-based electrolyte to improve the cyclability of HVLMBs with bi-electrode affinity characteristic—the TMS solvent with outstanding anti-oxidation stability preferentially tends to the aggressive cathodes while the FEC solvent with excellent film-forming ability approaches to the Li anode, attributed to the different adsorption energy between various solvents and electrodes. In addition, the sulfone electrolyte forms ultra-thin fluorine and sulfur-rich interphases, containing LiSO2F with S=O bonds of low electron density, associated with Li+ and e− species attacking the S-C and S-N bonds of LiTFSI and the S-C bonds of TMS. As confirmed by in-situ Raman, Ab initio molecular dynamics, and phase field simulations, the LiSO2F uniformizes in-plane Li+ transfer and mitigates transition metal dissolution, owing to the smallest Li+-LiSO2F bonding value (-1.95 eV) and the largest transition metal absorption value with LiSO2F (-3.86 eV) ever reported in the interfacial components. With Coulombic efficiency of 99.3%, the electrolyte enables an 86.1% retention after 500 cycles for Li/NMC811 (4.40 V) batteries.