S-doped VO2 induced oxygen vacancies for achieving high performance aqueous zinc ion batteries

At present, vanadium-based materials are still the research hotspot of cathode materials for aqueous zinc ion batteries, and metal ion doping is a common mean of modification for vanadium-based materials. However, doping with metal ion has inevitable drawbacks because the cations reduce the oxidation state of vanadium ions, leading to a decrease in theoretical energy density. Hence, in this study, to avoid the reduction of the capacity performance of the cathode material due to metal ion doping, we construct S-doped VO 2 with oxygen vacancies through hydrothermal synthesis combined with high-temperature calcinations. Impressively, the S-VO 2 -300 cathode can achieve a high specific capacity of 520 mAh g −1 at a low current density of 0.1 A g −1 , also exhibited excellent rate performance while it can reach a specific capacity of 267.6 mAh g −1 at 5.0 A g −1 , and demonstrate outstanding cycling stability (85.4 % capacity retention after 2000 cycles at 3.0 A g −1 ). • S-doped VO 2 nanospheres are successfully synthesized by employing high-temperature reduction process. • The synergistic benefits of S-doping and oxygen vacancies can improve the capacity characteristics of the material. • DFT calculations verified that S doping enhances the adsorption energy of cathode to Zn 2+ .