Hydrogen‐Deficient Chain‐Like Molecular Structure Confined Hydride Electrolyte for High‐Voltage All‐Solid‐State Lithium Metal Batteries

Abstract

Abstract The practical application of LiBH 4 in all‐solid‐state Li metal batteries (ASSLMBs) is hindered by low Li‐ion conductivity at room temperature, poor oxidative stability, and severe dendrite growth. Herein, porous [LiNBH] n with a hydrogen‐deficient chain‐like molecular structure are designed for in situ space‐confining LiBH 4 , which enables strong attraction of negatively charged H δ− atoms of [BH 4 ] − anions by Li + of [LiNBH] n chains that weakens Coulombic interaction between Li + and [BH 4 ] − anions and hence promotes Li ion diffusion. Additionally, the electron‐withdrawing effect of [LiNBH] n chains induces the local electron localization of LiBH 4 that enhances oxidative stability of LiBH 4 . Therefore, the Li ion conductivity of LiBH 4 reaches 2.2 × 10 −4 S cm −1 at 30 °C, nearly 4 orders of magnitude higher than that of LiBH 4 , with a voltage window of 5 V. Moreover, the interaction between Li metal and [LiNBH] n chains results in in situ formation of ultrathin layer composed of Li 3 N and LiB alloys that hinders Li dendrites growth, leading to a critical current density value of 7.5 mA cm −2 and a cycling life of 100 h at 4 mA cm −2 with an overpotential of 125 mV. Hence, LiCoO 2 |LiBH 4 ‐70LiNBH|Li cell at 0.5 C deliver a high capacity of 89.5 mA h g −1 after 400 cycles.