The method of preparing nanometer NiO was studied and nanometer NiO/C-composite materials were synthesized by the two-stage hydrothermal method. Products with different carbon content were obtained. The electrochemical properties, such as cyclic stability and the characteristics of the baking powder of nanodispersed NiO materials were studied. At the current density of 140 mA/g, the first discharge capacity of NiO/C composites with 6.1 % carbon content reached 2398.4 mA•h/g, and the first charge efficiency reached 66 %. After 30 cycles of constant current charging and discharging, the reversible capacity reaches 920 mA•h/g, and the capacity retention rate (compared with the second cycle) is 48 %. At the same time, the charge transfer impedance is minimal. At high current density, higher reversible capacity and better discharge performance are achieved. On the one hand, the amorphous carbon layer can buffer the huge volume change, reduce the degree of material pulverization and prevent agglomeration; on the other hand, carbon can improve the conductivity of the material. However, high carbon content resulted in serious agglomeration of products, and the discharge capacity and electrochemical performance were decreased. © 2020 — STC “Institute for Single Crystals”