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

ABSTRACT

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.