Lithium-sulfur batteries are regarded as the most promising energy storage system due to their high theoretical capacity (1675 mAh/g) and natural abundance of elemental sulfur. Nevertheless, the sluggish reaction of the rate-limiting step Li ₂S ₂ to Li ₂S conversion severely hampers the practical application of lithium-sulfur batteries. The resolution of this issue is contingent upon a thorough comprehension of the conversion mechanism of the rate-limiting step. To this end, we have developed the two-dimensional VO _(1-x)S _(1+x) alloy catalysts by ATAT and have constructed a theoretical model that can accurately predict the thermodynamic energy barrier of the rate-limiting step in lithium-sulfur batteries. Our model relates the energy barrier of the rate-limiting step to the p-band center of the nonmetallic and the d-band center of the metallic for the VO _(1-x)S _(1+x) alloy. This model facilitates the identification of the VO _(1-x)S _(1+x) alloy as a potential cathode catalyst for lithium-sulfur batteries.