A three-dimensional nitrogen-doped graphene framework decorated with an atomic layer deposited ultrathin V2O5 layer for lithium sulfur batteries with high sulfur loading

Abstract

Lithium–sulfur batteries with ultra-high theoretical capacity have gradually become candidates to replace existing energy systems. However, the severe polysulfide shuttle effect hinders their commercialization process. Although using polar materials to modify the electrode for the adsorption of lithium polysulfides (LiPSs) can improve the cycle stability to a certain extent, it also causes the decline of the overall energy density due to the extra mass. Herein, we decorate three-dimensional nitrogen-doped graphene (3DNG) with ultra-thin V₂O₅ coatings (ALDVO@3DNG) on interior surfaces via controllable atomic layer deposition (ALD). The large number of chemisorption sites can firmly anchor LIPSs and inhibit the shuttle effect, while its ultrathin thickness allows the smooth transfer of electrons and promotes the conversion of polysulfides. As a consequence, by controlling the cycles of the ALD process, the optimized ALDVO@3DNG composite delivers an exceptionally great first-cycle discharge capacity of 1555 mA h g⁻¹ at 0.2C, despite the poor conductivity of V₂O₅. And it exhibits a good cycling stability with an average decay rate of 0.052% at 2C. Even with a high sulfur loading up to 11.5 mg cm⁻², the ALDVO@3DNG composite still reaches a great capacity of 1296 mA h g⁻¹ (corresponding to an areal capacity of 14.9 mA h cm⁻²). This work provides an idea and experimental exploration of applying ALD for the ultrathin modification layer to enhance the electrochemical properties with a low extra weight burden, which may extend to other materials that may be applied in Li–S batteries.