Phase engineering and heteroatom incorporation enable defect-rich MoS2 for long life aqueous iron-ion batteries

Aqueous iron-ion batteries are regarded as one of the most promising candidates for grid applications owing to their low cost, high theoretical capacity, and excellent stability of iron in aqueous electrolytes. However, the slow Fe (de)insertion caused by the high polarity of Fe 2+ makes it difficult to match suitable cathode materials. Herein, defect-rich MoS 2 with abundant 1T phase is synthesized and successfully applied in aqueous iron-ion batteries. Benefit from abundant active sites generated by the heteroatom incorporation and S vacancy, as well as the highly conductive 1T phase, it can deliver a specific capacity of 123 mAh/g at a current density of 100 mA/g, and demonstrates an impressive capacity retention of 88% after 600 cycles at 200 mA/g. This work presents a novel pathway for the advancement of cathode materials for aqueous iron-ion batteries. The defect-rich MoS 2 with abundant 1T phase serves as a robust cathode material for aqueous iron-ion batteries. When coupled with 3 mol/kg Fe(CF 3 SO 3 ) 2 electrolyte, the MoS 2 -based battery exhibits a high specific capacity of 123 mAh/g at 100 mA/g and an impressive capacity retention of 88% after 600 cycles at 200 mA/g, which is remarkable among state-of-the-art novel aqueous ion batteries.