Solvent reconstruction and interfacial fluorination strategy for high-performance polyether lithium metal batteries

Abstract

Lithium metal batteries based on in situ semi-solid-state polyether electrolytes have emerged as a focal point of contemporary research due to their straightforward fabrication process, high energy density, and reliable safety. The DOL monomers exhibit characteristics of low viscosity and polymerization initiated by lithium salts at room temperature, presenting a significant commercial potential for the preparation of PDOL semi-solid-state electrolytes via in situ ring-opening polymerization for high-performance lithium metal batteries. However, the intrinsic performance deficiencies and poor antioxidant properties of polyether electrolytes have severely impeded their practical application. The utilization of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) as a diluent and fluoroethylene carbonate (FEC) as an additive for solvent reconstruction and interfacial fluorination of the semi-solid-state polyether electrolytes has effectively mitigated these issues. Density functional theory and molecular dynamics simulations demonstrate that the TTE diluent can optimize the solvent structure and enhance anionic coordination, thereby improving the electrochemical performance of PDOL-based electrolytes, which enables stable cycling of Li/Li symmetric batteries for over 2000 h at 0.1 mA cm ^− 2. Furthermore, the introduction of the fluorinated additive FEC has achieved exceptional performance in Li/NCM811 high-voltage lithium metal batteries, with an initial discharge specific capacity of 206.3 mAh g⁻¹ at 0.1C and stable charge-discharge cycling at 0.3C.