First-principles study on O-doped two-dimensional MoB/graphene heterojunction as a cathode material for lithium‑sulfur batteries

Lithium‑sulfur batteries have attracted significant attention because of their high energy density and cost-effectiveness. However, their cathode materials continue to face some challenges, including poor electrical conductivity, pronounced shuttle effects, and the structural instability of two-dimensional materials. As a cathode material in lithium‑sulfur batteries, two-dimensional MoB exhibits excessive adsorption energy for long-chain polysulfides, which negatively impacts the charge-discharge cycle. Graphene provides a high-conductivity scaffold to reinforce structural integrity. MoB/graphene heterostructure is proposed with doping oxygen atoms onto its surface, where the oxygen concentration is controlled to adjust both conductivity and polysulfide adsorption energy. The first-principles calculations and molecular dynamics were used to systematically assess the structural stability, conductivity, and polysulfide adsorption of the oxygen-doped MoB/graphene heterostructure. As oxygen concentration increases, conductivity decreases and adsorption energy increases. However, excessive oxygen doping harms the charge-discharge cycle. Consequently, we select an optimal oxygen concentration to balance Li₂S adsorption, avoiding both shuttle effects and excessive adsorption energy that reduce cycling efficiency. This work establishes a dual-strategy framework-heterostructure engineering combined with controlled oxygen doping-for 2D transition metal borides (MBene) cathodes, enabling tailored conductivity-adsorption balance and enhanced electrochemical performance.