Local charge redistribution enables single ionic conductor for fast charge solid Li battery

Abstract

Solid polymer electrolytes (SPEs) have been regarded as hopeful candidate electrolyte for solid-state lithium battery. However, the low Li⁺ transference number and poor interface stability pose great challenges for the high rate capability of SPE. Herein, inspired from the density functional theory (DFT) calculations that local positive charge distribution can be regulated by introducing strong electron-withdrawing groups, which can selectively anchor TFSI⁻, largely enhance the Li⁺ transference number. As predicted, the obtained CPE-NO₂ deliver a remarkable Li⁺ transference number of 0.91, equal to a single-ion conductor for Li⁺, largely high than that of the SPE (0.31), according well with the molecular dynamics (MD) simulations and pyridine complexation experiments. Furthermore, the PEO||Li interfacial stability, flame retardant ability, and mass transfer of Li⁺ in interface can also be largely enhanced by interfacial by-product, which are fast Li⁺ conductors according to TOF-SIMS results. Impressively, the Li|CPE-NO₂|Li cell exhibit superior cyclability for 2200 h at 0.1 mA cm⁻², and the solid LFP|CPE-NO₂|Li battery delivers prominent capacity of 127.4 mAh g⁻¹ at a high rate 5 C (12 mins). This work breaks the fast charge limitation of solid lithium battery, and provides a feasible approach for the construction of advanced solid electrolyte.