Template directed hydrothermal synthesis of flowerlike NiSex/C composites as lithium/sodium ion battery anodes

Transition metal selenides nanoparticles/carbon composites have been one of the promising lithium/sodium ion battery anodes. In the present study, NiSex nanoparticles encapsulated into microporous flowerlike carbon have been prepared by a hydrothermal route directed by the flowerlike Ni/C composite template. In a low hydrothermal temperature (i.e., 120 °C), the metallic Ni nanoparticles are transformed into Ni0.85Se, which has an average particle size of ~ 13.02 nm. The selenization degree and particle size can be obviously improved at a higher hydrothermal temperature (i.e., 160 or 180 °C), accompanying with the decrease in carbon content, and partial Ni0.85Se nanoparticles have been transformed into NiSe2. As anode of lithium ion batteries, the NiSex obtained at 180 °C (i.e., 180 °C-NiSe) can deliver a higher discharge capacity (e.g., 851.0 mA h g−1 after 100 cycles at 0.2 A g−1) and better cycling stability compared with the low temperature obtained sample. However, the rate capability and sodium ion storage performance of 120 °C-Ni0.85Se are better than the 180 °C-NiSex, and a discharge capacity of 326.5 mA h g−1 can be reached at a high rate of 5 A g−1 for 120 °C-Ni0.85Se. Also, a high capacity retention ratio of 64.3% after 100 cycles can be reached for 120 °C-Ni0.85Se as sodium ion battery anode. The different electrochemical performance can be attributed to the decreased particle size.