Defect engineering activating (Boosting) zinc storage capacity of MoS2

Rechargeable aqueous zinc ion batteries are particularly attractive for large-scale application due to their low cost, environmental friendliness and safety. However, the development of zinc ion batteries is seriously impeded by the limited choice of suitable cathode materials owing to their low reversibility and slow diffusion of divalent zinc cations in cathodes. Herein, we report defect engineered MoS2-x nanosheets as cathode for Zn ion cells. These MoS2-x nanosheets show a preferential insertion of Zn ions into sulfur vacancies, allowing a much greater capacity to be obtained compared to pure MoS2. Combined STEM analysis, electrochemical study, and theoretical modeling reveal that numerous edge sites and sulfur vacancies act as preferential intercalation sites for the zinc ions, leading to a much greater capacity than that of defect-free MoS2. After 1,000 cycles at a specific current of 1,000 mA/g, the defect engineered MoS2-x electrode can still deliver a reversible capacity of 88.6 mAh/g, accounting for 87.8% of the initial capacity. The MoS2-x electrode displays excellent electrochemical performance, making it a highly promising cathode material for future zinc ion batteries. It is believed that our strategy to use the chemistry of defects to unlock the electrochemical activity of known materials can be applied to other materials for practical divalent/multivalent batteries.