Insight on the effect of Ni and Ni-N co-doping on SnO₂ anode materials for lithium-ion batteries

With the increased demand for high-rate performance Li-ion batteries, it is necessary to find available methods to improve the rate properties of SnO₂ electrodes. It is noteworthy that doping was considered to be a feasible means. The electronic structures and diffusion energy barriers of Ni-doped and Ni-N co-doped SnO₂ were calculated based on density functional theory. The results estimated that the energy gaps of Ni-doped and Ni-N co-doped SnO₂ are 1.07 eV and 0.94 eV, which both are smaller than the value of 2.08 eV of SnO₂. These exhibit that the conduction properties of SnO₂ can be enhanced by doping with the Ni or Ni-N atoms. Moreover, the diffusion properties of Li can also be improved by doping with Ni-N atoms due to the diffusion energy barrier of Li from the B to C point for Ni-N co-doped SnO₂ being 0.12 eV smaller than the value of 0.24 eV for the pristine SnO₂. Meanwhile, the diffusion energy barriers of Li along other pathways for Ni-N co-doped SnO₂ are almost the same as 0.24 eV for SnO₂. These results show that both the electronic and ionic conductivity of SnO₂ can be enhanced by Ni-N co-doping, which provides a theoretical explanation to promote the rate properties of SnO₂ by Ni-N co-doping as anode materials for Li-ion batteries.