Carbon microspheres with well-developed micro- and mesopores as excellent selenium host materials for lithium-selenium batteries with superior performances

As host materials for efficient selenium storage and utilization, porous carbon materials with optimized and suitable pore structures are important in the development of high-performance Li-Se batteries. Herein, the synergetic effect of micro- and mesopores of carbon materials on the conversion reaction of loaded chain-structured Se_n is studied for superior Li-Se batteries. Carbon microspheres with well-developed micro- and mesopores are synthesized by spray pyrolysis. Carbon-vanadium oxide composite microspheres synthesized by spray pyrolysis transform into microporous carbon microspheres (P-carbon) by etching of vanadium oxide. An additional post-treatment of the spray-pyrolysis product at 400 °C yields carbon microspheres (A4-carbon) with well-developed micro- and mesopores by etching of vanadium oxide. The presence of both micro- and mesopores in carbon is desirable to achieve a fast conversion reaction of Se_n in the Se-loaded carbon microspheres. The Se-loaded carbon microspheres with well-developed micro- and mesopores (A4-carbon/Se) exhibit higher capacities and stable long-term cycling performances compared with similar microspheres with only micropores (P-carbon/Se). The discharge capacities of P-carbon/Se and A4-carbon/Se at the 500^th cycle at a current density of 0.5 A g⁻¹ are 403 and 582 mA h g⁻¹, respectively. Moreover, A4-carbon/Se microspheres exhibit a stable reversible capacity of 343 mA h g⁻¹ after 2000 cycles even at a high current density of 2.0 A g⁻¹; their capacity retention calculated from the 3^rd cycle is 87%.