Interface Modification and Halide Substitution To Achieve High Ionic Conductivity in LiBH4-Based Electrolytes for all-Solid-State Batteries

An Ultra-Stable Electrode-Solid Electrolyte Composite for High-Performance All-Solid-State Li-Ion Batteries

The low ionic and electronic conductivity between current solid electrolytes and high-capacity anodes limits the long-term cycling performance of all-solid-state lithium-ion batteries (ASSLIBs). Herein, this work reports the fabrication of an ultra-stable electrode-solid electrolyte composite for high-performance ASSLIBs enabled by the homogeneous coverage of ultrathin Mg(BH₄ )₂ layers on the surface of each MgH₂ nanoparticle that are uniformly distributed on graphene. The initial discharge process of Mg(BH₄ )₂ layers results in uniform coverage of MgH₂ nanoparticle with both LiBH₄ as the solid electrolyte and Li₂ B₆ with even higher Li ion conductivity than LiBH₄ . Consequently, the Li ion conductivity of graphene-supported MgH₂ nanoparticles covered with ultrathin Mg(BH₄ )₂ layers is two orders of magnitude higher than that without Mg(BH₄ )₂ layers. Moreover, the thus-formed inactive Li₂ B₆ with strong adsorption capability toward LiBH₄ , acts as a stabilizing framework, which, coupled with the structural support role of graphene, alleviates the volume change of MgH₂ nanoparticles and facilitates the intimate contact between LiBH₄ and individual MgH₂ nanoparticles, leading to the formation of uniform stable interfaces with high ionic and electronic conductivity on each MgH₂ nanoparticles. Hence, an ultrahigh specific capacity of 800 mAh g^-1 is achieved for MgH₂ at 2 A g^-1 after 350 cycles.