Abnormal Ionic Conductivities in Halide NaBi 3 O 4 Cl 2 Induced by Absorbing Water and a Derived Oxhydryl Group

In hunting for safe and cost-effective materials for post-Li-ion energy storage, the design and synthesis of high-performance solid electrolytes (SEs) for all-solid-state batteries are bottlenecks. Many issues associated with chemical stability during processing and storage and use of the SEs in ambient conditions need to be addressed. Now, the effect of water as well as oxyhdryl group ( OH) on NaBi O Cl are investigated by evaluating ionic conductivity. The presence of water and OH results in an increase in ionic conductivity of NaBi O Cl owing to diffusion of H O into NaBi O Cl , partially forming binding OH through oxygen vacancy repairing. Ab initio calculations reveal that the electrons significantly accumulate around OH and induce a more negative charge center, which can promote Na hopping. This finding is fundamental for understanding the essential role of H O in halide-based SEs and provides possible roles in designing water-insensitive SEs through control of defects.