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(BH 4 ) 2 layers on the surface of each MgH 2 nanoparticle that are uniformly distributed on graphene. The initial discharge process of Mg(BH 4 ) 2 layers results in uniform coverage of MgH 2 nanoparticle with both LiBH 4 as the solid electrolyte and Li 2 B 6 with even higher Li ion conductivity than LiBH 4 . Consequently, the Li ion conductivity of graphene-supported MgH 2 nanoparticles covered with ultrathin Mg(BH 4 ) 2 layers is two orders of magnitude higher than that without Mg(BH 4 ) 2 layers. Moreover, the thus-formed inactive Li 2 B 6 with strong adsorption capability toward LiBH 4 , acts as a stabilizing framework, which, coupled with the structural support role of graphene, alleviates the volume change of MgH 2 nanoparticles and facilitates the intimate contact between LiBH 4 and individual MgH 2 nanoparticles, leading to the formation of uniform stable interfaces with high ionic and electronic conductivity on each MgH 2 nanoparticles. Hence, an ultrahigh specific capacity of 800 mAh g -1 is achieved for MgH 2 at 2 A g -1 after 350 cycles.