FeSO4 has the characteristics of low cost and theoretical high energy density (799 W.h.kg-1 with a two-electron reaction),which can meet the demand for next-generation lithium-ion batteries.Herein,FeSO4 as a novel high-performance conversion-reaction type cathode is investigated.We use dopamine as a carbon coating source to increase its electronic conductivity.FeSO4@C demonstrates a high reversible specific capacity (512 mA.h.g-1)and a superior cycling performance (482 mA.h.g-1 after 250 cycles).In addition,we further study its reaction mechanism.The FeSO4 is converted to Fe and Li2SO4 during lithium ion insertion and the Fe—Li2SO4 grain boundaries further store additional lithium ions.Our findings are valuable in exploring other new conversion-type lithium ion battery cathodes.