Selenium in nitrogen-doped microporous carbon spheres for high-performance lithium-selenium batteries

Selenium, which is in the same group of elements as sulphur and has a higher electrical conductivity and a comparable theoretical volumetric capacity density compared to sulphur, is a prospective candidate for use in cathode materials. Herein, we propose and realise a novel strategy: using selenium in nitrogen-doped microporous carbon spheres for Li-Se batteries. As a new cathode material, the integrated composite can ensure the complete electrochemical reaction of selenium. The abundant micropores uniformly distributed in the carbon matrix and the strong adsorptive power can effectively hold the selenium, while the synergetic effect of the nitrogen heteroatoms, graphitisation, the unoccupied mesopores, and the relatively high conductivity of selenium facilitate the quick transmission of Li ions and electrons. Li-Se batteries based on this concept show excellent electrochemical performance with a high reversible capacity of 570 mA h g(-1) over 350 cycles at 0.5C, outstanding cycling stability at a rate of 2 C over 1600 cycles without capacity loss, and remarkable rate capability.