N/O-doped porous carbon matrix for improved potassium-selenium battery cathode in different electrolyte systems

Combining the high abundance of potassium (K) in the Earth’s crust and the high theoretical energy density of selenium (Se), a potassium-selenium (K-Se) battery is attractive as an alternative energy storage system. However, some urgent issues still need to be solved to obtain efficient selenium-based cathodes, such as the shuttle effect of high-order selenides in electrolytes and volume expansion during the redox process. Herein, we report Se/heteroatoms (N and O) dual-doped hierarchical porous carbon (Se/HHPC) composite as cathode material for the K-Se battery. The hierarchical porous carbon frameworks not only provide storage and expansion buffer space for Se-based cathode material, but also facilitate the penetration of the electrolyte, which effectively improves the cell's electrical conductivity. In addition, the dual-doped heteroatoms enhance the interaction between potassium selenide and carbon host. When tested for K-ion batteries with carbonate electrolytes, Se/HHPC cathode exhibits a relatively high electrochemical performance (228 mAh g−1, 200 cycles, 0.2 C) under the synergy of space bondage and chemisorption. The electrode could deliver a rate capability of 295 mAh g−1 at 4 C. Furthermore, the hybrid cathode also exhibits excellent properties in ether electrolytes and has a reversible capacity of 236 mA h g−1 at 0.2 C after 300 cycles and a rate capability of 234 mAh g−1 at 4 C. [Display omitted] •Heteroatoms dual-doped hierarchical porous carbon (HHPC) is prepared.•The synergistic effects of pores and heteroatoms in HHPC is crucial to cathode.•Se/HHPC shows excellent properties for K-Se batteries in different electrolytes.