Flexible hybrid solid electrolyte incorporating ligament-shaped Li6.25Al0.25La3Zr2O12 filler for all-solid-state lithium-metal batteries

Abstract

In this study we used a solution-casting method to fabricate a hybrid solid electrolyte (HSE) membrane based on a poly(vinylidene fluoride–co–hexafluoropropylene)/polyacrylonitrile (PVDF-HFP/PAN) polymer blend loaded with an interconnected ligament–shaped Li6.25Al0.25La3Zr2O12 (Al-doped LLZO) filler and applied it in all-solid-state lithium-metal batteries (ASSLMBs). The as-prepared HSE containing the optimized quantity of Al-doped LLZO@PVDF-HFP/PAN/LiClO4/succinonitrile filler displayed high ionic conductivity (1.12 × 10–4 S m–1 at 25 °C), a wide electrochemical stability window [up to 4.2 V (Li/Li+)], and a high transference number (0.42). A full cell based on the composite cathode NCM811 (LNi0.8Co0.1Mn0.1O2, c-NCM811)/HSE/Li had a highest discharge specific capacity of 160.92 mA h g–1 at 0.1 C and a capacity retention of 92.52% after 100 cycles; at 0.2 C, these values were 144.70 mA h g–1 and 85.72% (after 100 cycles), respectively. The Li+ diffusion coefficient of the c-NCM811/HSE/Li cell was one order of magnitude higher than that of the corresponding cell having a bare cathode (b-NCM811/HSE/Li) as well as c-NCM811/SPE+10%SN/Li. We used a multiple-mode calorimetry device to investigate the in situ heat flow profiles of c-NCM811/HSE/Li, c-NCM811/SPE/Li, and b-NCM811/HSE/Li cells; the c-NCM811/HSE/Li cell exhibited the lowest heat profile. Thus, ASSLMBs featuring the NCM811 composite cathode and this as-prepared HSE have great potential for use in applications requiring batteries of high energy density.