Tellurium: A High‐Volumetric‐Capacity Potassium‐Ion Battery Electrode Material

Abstract Currently, exploring high‐volumetric‐capacity electrode materials that allow for reversible (de‐)insertion of large‐size K⁺ ions remains challenging. Tellurium (Te) is a promising alternative electrode for storage of K⁺ ions due to its high volumetric capacity, confirmed in lithium‐/sodium‐ion batteries, and the intrinsic good electronic conductivity. However, the charge storage capability and mechanism of Te in potassium‐ion batteries (KIBs) have not been unveiled until now. Here, a novel K–Te battery is constructed, and the K⁺‐ion storage mechanism of Te is revealed to be a two‐electron conversion‐type reaction of 2K + Te ↔ K₂Te, resulting in a high theoretical volumetric capacity of 2619 mAh cm⁻³. Consequently, the rationally fabricated tellurium/porous carbon electrodes deliver an ultrahigh reversible volumetric capacity of 2493.13 mAh cm⁻³ at 0.5 C (based on Te), a high‐rate capacity of 783.13 mAh cm⁻³ at 15 C, and superior long‐term cycling stability for 1000 cycles at 5 C. This excellent electrochemical performance proves the feasibility of utilizing Te as a high‐volumetric‐capacity active material for storage of K⁺ ions and will advance the practical application of KIBs.