Lithium Conductivity and Ions Dynamics in LiBH₄/SiO₂ Solid-Electrolytes studied by Solid-State NMR and Quasi Elastic Neutron Scattering and applied in Lithium-Sulfur Batteries

Composite solid-state electrolytes based on ball-milled LiBH4/SiO2 aerogel exhibit high lithium conductivities and we have found an optimal weight ratio, 30/70 wt% LiBH4/SiO2, with a conductivity of 0.1 mS/cm-1 at room temperature. We have studied the Li+ and BH4- dynamics using Quasi- Elastic Neutron Scattering and solid-state Nuclear Magnetic Resonance and found that only a small fraction (~10%) of the ions have high mobilities while most of the LiBH4 shows behavior similar to macrocrystalline material. The modified LiBH4 is formed from interaction with the SiO2 surface and most probably from reaction with the surface silanol groups. We successfully applied these composite electrolytes in lithium-sulfur solid-state batteries. The batteries show reasonable capacity retention (794 mAhg-1 sulfur after 10 discharge-charge cycles, coulombic efficiency of 88.8% ± 2.7% and average capacity loss of 7.2% during the first 10 cycles)