Synergistic effect of sulfur on electrochemical performances of carbon‐coated vanadium pentoxide cathode materials with polyvinyl alcohol as carbon source for lithium‐ion batteries

Vanadium pentoxide (V2O5) is a common cathode material for lithium-ion battery, but its low electronic and ionic conductivity seriously affect its electrochemical performances. In this paper, a type of carbon-coated V2O5 and S composite cathode material with PVA as the carbon source is utilized to lithium-ion batteries. X-ray diffraction and Raman test results illustrate that sulfur can make the V2O5 lose part of oxygen atoms and become nonstoichiometric vanadium oxide (V2O5-x). Electrochemical test results show that sulfur can provide a considerable proportion of the specific capacity of the whole cathode. This illustrates that the synergistic effect of sulfur can optimize the structure of vanadium pentoxide in order to increase more electron transfer channels, and at the same time, it also can provide additional specific capacity for the whole cathode. When the ratio of V2O5 and sulfur is 1:3, the discharge specific capacity can reach 923.02, 688.37, and 592.70 mAh g−1 at 80, 160, and 320-mA g−1 current density, respectively, and after 100 times charge and discharge cycles at 320-mA g−1 current density, the capacity retention rate can achieve to more than 60%.