Searching novel polyethylene oxide (PEO) based composite electrolyte that can be compatible with high voltage cathodes (> 4 V) at room temperature is a long-standing challenge, but essential to achieve high-energy-density for solid-state lithium (Li) metal batteries. Herein, we develop an advanced dual-salts reinforced PEO/garnet solid-state composite electrolyte (SCE) with high ionic conductivity of 9 × 10⁻⁴ S cm⁻¹ and an electrochemical stability window up to ~ 4.7 V, where the lithium bis(oxalate)borate (LiBOB) is used as additive with LiClO₄. The dual-salts reinforced SCE can achieve excellent room temperature cycling performance of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)/Li metal batteries. The multiplied polymer-ion interactions and formation of Li‒B‒O/C‒O species originated from the (oxalato)borate group of LiBOB effectively promotes the electrochemical stability of the PEO based composite electrolyte and its wetting properties with electrodes. Unwanted non-conductive decomposition products, such as Li₂O and Li₂CO₃, and NCM particles cracking during cycling are successfully suppressed. The NCM811 solid-state cells using the optimized dual-salts composite electrolyte delivers high specific capacity of 190 mA h g⁻¹ and exhibit stable cycling performance for more than 200 cycles at 25 °C.

在室温下寻找可与高压阴极（> 4 V）兼容的新型聚环氧乙烷（PEO）基复合电解质是一项长期的挑战，但对于实现固态锂（Li）的高能量密度至关重要金属电池。本文中，我们开发了一种先进的双盐增强PEO /石榴石固态复合电解质（SCE），具有9×10 ^-4 S cm ^-1的高离子电导率和高达4.7 V的电化学稳定性窗口，其中锂双（草酸酯）硼酸酯（LiBOB）用作与LiClO _4的添加剂。双盐增强SCE可以实现LiNi _0.8 Co _0.1 Mn _0.1 O _2的优异室温循环性能（NCM811）/锂金属电池。源自LiBOB的（草酸酯）硼酸酯基的Li polymerB‒O / C‒O种类繁多的聚合物离子相互作用和形成，有效地促进了PEO基复合电解质的电化学稳定性及其与电极的润湿性能。成功抑制了有害的非导电分解产物（如Li ₂ O和Li ₂ CO ₃）以及循环过程中的NCM颗粒破裂。使用优化的双盐复合电解质的NCM811固态电池可提供190 mA h g ^-1的高比容量，并在25°C下具有200多个循环的稳定循环性能。