High-Performance Potassium-Tellurium Batteries Stabilized by Interface Engineering.

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 K 2 Te 3 and ultimately to K 5 Te 3 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 (Al 2 O 3 ) 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 Al 2 O 3 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.