Electrochemical lithium storage mechanism exploration of a 4.1 V cathode material with high energy/power density and low cost

•Na2.4Fe1.8(SO4)3 is firstly used as lithium-storage cathode material.•The thermodynamics and kinetics of ion insertion mechanism is thoroughly studied.•Optimized cathode exhibits excellent high energy/power density in LIB.•A low cost and high performance cathode is proposed for LIB. In this work, cost effective and high energy/power density Na2.4Fe1.8(SO4)3 (NFS) is adopted as cathode material in Lithium ion Batteries (LIBs) for the first time. The carbon coated NFS is synthesized via a simple solid state method under 400 °C. The highly effective multidimensional electron transport path and stable polyanion structure enables extremely high electrochemical lithium storage performance of NFS. The optimized NFS composite displays high specific capacity and discharge voltage (101.2 mAh/g, 3.82 V at 1C), superb rate performance (88.1 mAh/g at 20C with average discharge voltage plateau of 3.46 V vs. Li+/Li) and excellent cycle stability (92.6% of the initial capacity after 1000 cycles at 10C). Electrochemical and non-electrochemical behaviors of NFS cathode in lithium ions contained electrolyte have been thoroughly studied to better understanding the Lithium storage mechanism. This work proves that the low cost Fe-based sulfate NFS is a very competitive candidate as cathode material for LIBs.