Nickel single-atom catalysts on porous carbon nanosheets for high-performance lithium-selenium batteries

Lithium-selenium (Li–Se) batteries have attracted intensive attention due to the high theoretical volumetric capacity (3253 mA h cm−3) and high electrical conductivity (1 × 10−3 S m−1) of selenium. However, the shuttle effect, rapid capacity fading and sluggish electrochemical process of the lithium selenides limit its further application. Herein, a catalyst of nickel single atoms (SA)/nitrogen-doped porous carbon nanosheets (Ni-NC) has been constructed and applied as an ideal host for selenium cathode. Such a material allows the adsorption of lithium selenides while the Ni SA serves as efficient catalytic site for the conversion of these selenides during charge/discharge process, as the theoretical calculation results suggest that the Ni SA could enhance the binding energy of the carbon host towards the intermediates and improve the electron transfer. As expected, the Ni-NC/Se cathode exhibits a capacity of 495 mAh g−1 at 0.2 C and 311 mAh g−1 at 4 C and good cycling stability of 225 mAh g−1 after 1000 cycles at 4 C with a Coulombic efficiency of ∼100 %, significantly better than the pure carbon host without Ni SA sites.