Improving the Cycle Life of Solid-State Batteries by Addition of Oxide Nanoparticles to a Complex Hydride Solid Electrolyte

We report that the addition of silica nanoparticles to the iodide-substituted LiBH4 (h-Li(BH4)0.8(I)0.2) improves the ion conductivity and, remarkably, the cycle life of the all-solid state batteries. The h-Li(BH4)0.8(I)0.2-SiO2 was synthesized by mecha-nochemical treatment and possesses a Li+ conductivity of 9.3 x 10-5 S cm-1 at RT. It has an electrochemical stability window of about 2.5 V vs Li+/Li and an improved stability against Li-metal, compared to h-Li(BH4)0.8(I)0.2, owing to the addition of oxide nanoparticles, which we ascribed to a greater mechanical stability of the solid-state electrolyte. The all-solid state battery Li|h-Li(BH4)0.8(I)0.2-SiO2|TiS2 demonstrated a good long-term cyclability, i.e., over 200 cycles at C/ 20 and even including a C-rate of C/5, demonstrating that the addition of oxide nanoparticles improves the cycling stability of the electrolyte.