Point Defect Engineering Enabled the High Ionic Conductivity of BaSnF4 for Solid-State Fluoride-Ion Batteries at Room Temperature

All-solid-state fluoride-ion batteries (FIBs) have emerged as a candidate for the next generation of electrochemical energy storage devices due to their ultra-high volume, energy density, and safety. However, the insufficient ionic conductivity of solid-state electrolytes in FIBs still impedes their practical application. Herein, point defects are introduced in the BaSnF4-based solid-state electrolyte by Ce3+ doping through a coprecipitation method to meet the requirement of high ionic conductivity for FIBs at room temperature (RT). It is found that the introduced point defects in BaSnF4 crystals are distinctly beneficial for enhancing the ionic conductivity of the solid-state electrolyte. The as-prepared solid-state electrolyte Ba0.09Ce0.05SnF4.05 exhibits a high ionic conductivity of 5.2 x 10(-4) S cm(-1) at RT, which is 3.5 times higher than that of BaSnF4. Meanwhile, the as-prepared Ba(0.09)Ce(0.05)SnF(4.05 )electrolyte shows a lower activation energy (0.15 eV) compared with BaSnF4 (0.25 eV), which will be conducive to facilitating the shuttle of ions in the solid-state electrolyte. Consequently, the initial specific capacity of the as-prepared all-solid-state FIBs (SnlBa(0.95)Ce(0.05)SnF(4.05)IBiF(3)) can reach 170.9 mA h g(-1) and work stably for more than 30 cycles. Apparently, the construction of point defects in the fluoride solid-state electrolytes offers a new pathway for enhancing the RT ionic conductivity of the solid-state electrolytes.

Automated summary

Introducing point defects in the solid-state electrolyte can significantly enhance the ionic conductivity of all-solid-state fluoride-ion batteries, leading to improved battery performance.