A Potassium-Tellurium Battery

Abstract Developing high-energy-density batteries is essential for storing and utilizing electricity generated from renewable energy sources. Herein, we, for the first time, report a rechargeable potassium-tellurium (K–Te) battery. This new battery system is capable of providing flat voltage plateaus at a high average potential of 1.6 ​V, high volumetric/specific capacities (2552 mAh cmTe−3 or 409 mAh gTe−1) and energy densities (4081 ​Wh LTe−1 or 654 ​Wh kgTe−1). Moreover, the intrinsic electron conduction ability of Te cathode enables fast reaction kinetics and good rate capability to K–Te batteries. Combined X-ray powder diffraction and X-ray photoelectron spectroscopy analyses reveal the underlying reaction mechanism, which involves reversible stepwise phase transformations from Te to K2Te3 and ultimately to K5Te3. This work paves the way for the development of high-energy-density K–Te batteries.