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 Li₂B₆ 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 Li₂B₆ 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. © 2023 Wiley-VCH GmbH.