Application of rich-defect expanded graphite with improved ion transport and kinetics for sodium storage at low temperature

Abstract

Due to the shortage of fossil energy and environmental pollution, electric vehicles have become irreplaceable in the world, and their development has become an irreversible trend. However, in high latitude and altitude low temperature areas, they are still limited due to the obvious performance degradation of power batteries. Therefore, to promote the popularity of electric vehicles, we report a N-doped graphite anode for sodium ion batteries with an excellent capacity and stability based on fast kinetics during the sodiation process at low temperature. The N-doped graphite anode was obtained by a thermal treatment method, resulting in many defects on the interlayer and an increased interlayer spacing of 3.68 Å. It presented high retention values of 93.4% and 94.8% with capacities of 182 mA h g⁻¹ and 211 mA h g⁻¹ at C-rate values of 1.0C and 0.5C at 0 °C, respectively. More defects as ionic channels offered faster kinetics, and Na⁺ diffusion coefficients at 0 °C reached 1.1 × 10⁻¹² cm⁻² s⁻¹ and 2.5 × 10⁻¹² cm⁻² s⁻¹, similar to results at room temperature. In addition, the morphologies explained that defects enhanced Na⁺ migration and that the structure of the interlayer was quite stable. Therefore, N-doped graphite is worthwhile to be considered for further commercial sodium storage as anodes of power batteries in high latitude and altitude areas.