Li3V2(PO4)3 particles embedded in a N and S co-doped porous carbon cathode for high performance lithium storage: an experimental and DFT study†

Abstract

Li₃V₂(PO₄)₃ (LVP) coated with N and S co-doped carbon (NSC) was investigated by DFT calculation, suggesting that NSC significantly enhances electronic conductivity and lowers the energy barrier to Li⁺ migration in comparison to LVP-embedded in pristine carbon. To experimentally confirm the theoretical prediction, three types of LVP particle embedded in N and S co-doped porous carbon (LVP@NSC) materials with various nitrogen and sulfur molar ratios (N : S = 1 : 1, 1 : 2 and 2 : 1) were prepared by a facile freeze-drying-assisted wet chemical route associated with a post-annealing process. When used as a cathode for a lithium-ion battery (LIB), the designed LVP@NSC with N : S = 1 : 2 exhibits outstanding high rate capacities of 124.4 and 107.85 mA h g⁻¹, respectively, at 2 and 20 C in a voltage window of 3.0–4.3 V, and an ultralong cycling stability of 500 times at 20 C while retaining a reversible capacity of 100.22 mA h g⁻¹, possibly due to its smallest charge transfer resistance and highest Li⁺ migration coefficient, which is in good agreement with the theoretical prediction. This work not only reveals the critical role of an interaction mechanism between NSC and LVP, but also offers great potential for high-energy density LIB applications.