A graphitized hierarchical porous carbon as an advanced cathode host for alkali metal-selenium batteries

Abstract

• One-step activation-free synthesis of hierarchical porous carbon is achieved by CO 2 erosion. • HPC possesses high electronic conductivity with controllable graphitization degree. • The excellent specific surface area and voids of HPC can buffer deposition and drastic volume breath. • HPC/Se shows high excellent electrochemical performance as cathode for alkali metal-selenium batteries. Selenium cathode, of high volumetric energy density and compatibility with safe/cheap carbonate electrolyte, are plagued by low active material utilization, limited rate capability and fast capacity fading. Therefore, a carbon host, capable of speeding electron transfer, facilitating Li + diffusion and buffering drastic volume breath, is greatly demanded. Herein, a graphitized hierarchical porous carbon is prepared by metallothermic reduction reaction of CO 2 , and employed as cathode host for alkali metal-Se batteries. With high electronic conductivity, ultrahigh specific area (1740 m 2 g −1 ) and abundant porosity (1.76 cm 3 g −1 ), this carbon host after Se infiltrating exhibits an initial capacity of 994 mAh g −1 and a reversible capacity of 538 mAh g −1 at 0.5C in the initial cycle for lithium-selenium batteries. In addition, a reversible capacity of 451 mAh g −1 can still be achieved at a current density of 2C, with a low capacity decay rate of about 0.037% per cycle in subsequent 800 cycles. In further tests, HPC/Se cathode also shows superior rate capabilities and stable cyclability for sodium-selenium batteries and potassium-selenium batteries.