The electrochemical performance of the cathode material directly determines the energy density of the battery. The high cathode potential of the cathode increases the output voltage of the battery. The adsorption energy and the upper limit of Li⁺ adsorption by the cathode have significant effects on Li⁺ storage capacity. Li⁺ diffusion barrier in the cathode affects the charging and discharging efficiency. Cycle stability is determined by the reversibility of the cathode structure. Working potential window is related to the change of HOMO/LUMO during discharge. Appling the first-principles calculations, we explore the electrical properties, Li⁺ adsorption energy, Li⁺ diffusion barrier, working potential window, and theoretical capacity of layered 2D-FeS₂ cathode during discharge. Layered 2D-FeS₂ with excellent electronic conductivity accelerates conversion efficiency of electrons and holes with each other. 2D-FeS₂ after discharge is 2D-Li₂FeS₂. Both of them have the same lattice structure P-3M1. The diffusion rate of Li⁺ is faster during the initial 2D-FeS₂ discharge. Working potential window of layered 2D-FeS₂ is 2.27 ∼ 1.81 V, the theoretical capacity is 893.56 mAh/g. The working potential of layered 2D-FeS₂ increases with its LUMO/HOMO redox capacity. This work theoretically confirmed the reversibility of the structure of layered 2D-FeS₂ after discharge and investigated its electrochemical properties.