Rationally designed hollow carbon nanospheres decorated with S,P co-doped NiSe2 nanoparticles for high-performance potassium-ion and lithium-ion batteries

Hollow nanostructures with external shells and inner voids have been proved to greatly shorten the transport distance of ions/electrons and buffer volume change, especially for the large-sized potassium-ions in secondary batteries. In this work, hollow carbon (HC) nanospheres embedded with S,P co-doped NiSe2 nanoparticles are fabricated by “drop and dry” and “dissolving and precipitation” processes to form Ni(OH)2 nanocrystals followed by annealing with S and P dopants to form nanoparticles. The resultant S,P-NiSe2/HC composite exhibits excellent cyclic performance with 131.6 mA h g−1 at 1000 mA g−1 after 3000 cycles for K+ storage and a capacity of 417.1 mA h g−1 at 1000 mA g−1 after 1000 cycles for Li+ storage. K-ion full cells are assembled and deliver superior cycling stability with a capacity of 72.5 mA h g−1 at 200 mA g−1 after 500 cycles. The hollow carbon shell with excellent electrical conductivity effectively promotes the transportation and tolerates large volume variation for both K+ and Li+. Density functional theory calculations confirm that the S and P co-doping NiSe2 enables stronger adsorption of K+ ions and higher electrical conductivity that contributes to the improved electrochemical performance.