Solid polymer electrolyte with in-situ generated fast Li+ conducting network enable high voltage and dendrite-free lithium metal battery

Abstract

Solid polymer electrolytes (SPEs) with profound compatibility for high-voltage cathodes and reliable operation over a board temperature range are in urgent demand for the practical application of solid lithium metal batteries (SLMBs). In this study, a SPE containing interconnected fast Li+ conducting network was constructed via an in-situ hydrolysis of tetraethoxysilane (TEOS) within polyacrylonitrile (PAN) matrix to intensify the thermal stability of SLMBs. The in-situ formed interconnected inorganic network not only acts as a robust backbone for the whole SPE, but also furnishes sufficient continuous surfaces with Lewis-acidic sites, which will promote the dissociation of Li salt. As a consequence, the fabricated SPE exhibits an promising ionic conductivity of ∼0.35 mS cm−1, an attractive Young’ modulus of 8.627 Gpa and a satisfactory lithium-ion transference number of 0.52. Solid-state nuclear magnetic resonance (S-NMR) and X-ray photoelectron spectroscopy (XPS) techniques were used to unravel the interactions among Li+ ions, PAN and as-formed SiO2. Based on the in-situ formed SPE, a Li/LiFePO4 SLMB presents an excellent cycle stability from 20 to 80 °C and a Li/LiNi0.6Mn0.2Co0.2O2 SLMB shows a steady discharge capacity of 173.1 mAh g−1 with 93.8 % retention after 200 cycles at 4.3 V. Additionally, the Li/LiFePO4 pouch cell also delivers a stable cyclability and superior safety for practical applications. The design strategy of our work provides a rigid−flexible coupling dynamic strategy to fabricate SPEs for wide-temperature applicability and high energy density SLMBs.