Design and Synthesis of Cubic K<sub>3−2</sub><i><sub>x</sub></i>Ba<i><sub>x</sub></i>SbSe<sub>4</sub> Solid Electrolytes for K–O<sub>2</sub> Batteries
Jieren Shao, Huiling Ao, Lei Qin, Jocelyn Elgin, Curtis E. Moore, Yehia Khalifa, Songwei Zhang, Yiying Wu
Abstract
Abstract Developing K‐ion conducting solid‐state electrolytes (SSEs) plays a critical role in the safe implementation of potassium batteries. In this work, a chalcogenide‐based potassium ion SSE is reported, K 3 SbSe 4 , which adopts a trigonal structure at room temperature. Single‐crystal structural analysis reveals a trigonal‐to‐cubic phase transition at the low temperature of 50 °C, which is the lowest among similar compounds and thus provides easy access to the cubic phase. The substitution of barium for potassium in K 3 SbSe 4 leads to the creation of potassium vacancies, expansion of lattice parameters, and a transformation from a trigonal phase to a cubic phase. As a result, the maximum conductivity of K 3−2 x Ba x SbSe 4 reaches around 0.1 mS cm −1 at 40 °C for K 2.2 Ba 0.4 SbSe 4 , which is over two orders of magnitude higher than that of undoped K 3 SbSe 4 . This novel SSE is successfully employed in a K–O 2 battery operating at room temperature where a polymer‐laminated K 2.2 Ba 0.4 SbSe 4 pellet serves as a separator between the oxygen cathode and the potassium metal anode. Effective protection of the K metal anode against corrosion caused by O 2 is demonstrated.