A graphitized hierarchical porous carbon as an advanced cathode host 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 CO2, and employed as cathode host for alkali metal-Se batteries. With high electronic conductivity, ultrahigh specific area (1740 m2 g−1) and abundant porosity (1.76 cm3 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.