High‐Performance Potassium‐Tellurium Batteries Stabilized by Interface Engineering

Abstract The emerging potassium‐tellurium (K‐Te) battery system is expected to realize fast reaction kinetics and excellent rate performance due to the exceptional electrical conductivity of Te. However, there has been a lack of fundamental knowledge about this new K‐Te system, including the reaction mechanism and cathode structure design. Herein, a two‐step reaction pathway from Te to K₂Te₃ and ultimately to K₅Te₃ is investigated in carbonate electrolyte‐based K‐Te batteries by X‐ray diffraction, high‐resolution transmission electron microscopy, and selected area electron diffraction characterizations. Additionally, the atomic layer deposition technique is adopted to deposit an ultrathin aluminum oxide (Al₂O₃) film on the electrode surface, which induces the generation of a stable solid electrolyte interphase layer and reduces the loss of active materials effectively. Consequently, the rationally fabricated Te/porous carbon cathode with functional Al₂O₃ coating delivers remarkable long‐term cycling stability over 500 cycles at 1 C with an ultralow capacity decay of only 0.01% per cycle. This interface engineering strategy is validated to stabilize the electrode surface, enhance the structural integrity and ensure reliable electron transfer and K‐ion conduction over repeated potassiation/depotassiation cycles. These findings are expected to promote the development of high‐energy‐density K‐S/Se/Te batteries.