A Novel Cathode Based on Selenium Confined in Biomass Carbon and Graphene Oxide for Potassium‐Selenium Battery

Abstract Selenium exhibits smaller volume expansion and much higher electrical conductivity compared with sulfur, which makes it considered as a potential cathode material. In order to improve electrochemical performance of potassium‐selenium (K−Se) batteries, we prepared porous carbon/Se (PC/Se) composite via carbonization, KOH activation and melt diffusion and synthesized a novel porous carbon/Se/graphene oxide (PC/Se/GO) composite with the Se content of ∼40 % via controlling the ionic strength of the solution as cathode material in the work. The combination of porous carbon structure and graphene can effectively relieve the volume expansion of selenium during the charge and discharge process, and provide excellent conductivity. The one‐step conversion without polyselenides between the PC/Se/GO composite and metal potassium further improves the capacity and cycling stability. Therefore, the PC/Se/GO delivers high discharge capacities of 426.3 and 316.8 mAh g −1 in the 2nd and 150th cycles at 0.5 C. This work plays an important reference role for the exploration of advanced potassium‐selenium batteries.