Preparation and Performance of Eu3+-Doped BaSnF4-Based Solid-State Electrolytes for Room-Temperature Fluoride-Ion Batteries

Abstract

Fluoride-ion batteries are promising “next-generation” electrochemical energy storage devices, and thus, the room-temperature rechargeable fluoride-ion batteries (FIBs) have attracted tremendous attention due to their high theoretical volume energy density and high safety. However, a series of problems including high interface impedance and poor ionic conductivity at room temperature prevent further development and commercial application of FIBs. Herein, rare-earth element Eu3+-doped BaSnF4 solid solutions [Ba1–xEuxSnF4+x (0 ≤ x ≤ 0.06)] are designed and prepared to improve the performance of BaSnF4 solid electrolytes for room-temperature FIBs. It has been found that the as-prepared Ba0.98Eu0.02SnF4.02 solid-state electrolyte can achieve a better ionic conductivity of 3.8 × 10–4 S cm–1 at room temperature after a calcination process at 300 °C for 2 h, which is the improvement of an order of magnitude in comparison with the original samples. In addition, the FIBs based on Ba1–xEuxSnF4+x (0 ≤ x ≤ 0.04) solid-state electrolytes (Sn/Ba0.98Eu0.02SnF4.02/BiF3) show a discharge capacity of 106 mAh g–1 at 1st cycle and 72 mAh g–1 at 20th cycle. Moreover, the Sn/Ba1–xEuxSnF4+x/BiF3 (0 ≤ x ≤ 0.04) batteries also exhibit good cycling stability and rate performance. Therefore, the addition of Eu3+ can better improve the ionic conductivity of the original solid electrolyte material, which provides a new strategy for the preparation and modification of fluoride-ion electrolytes in FIBs chracterization chracterization.