A sodium-ion battery based on olivine iron phosphate cathode and nanostructured tin carbon anode

Lithium-ion battery is presently the most diffused energy storage system in the electronic portable devices market, this in view of its high energy density and intrinsic safety due the replacement of the reactive lithium-metal by the lithium-insertion, graphite anode. [1,2] The increased demand of lithium and its concentration in few countries contributed to a rapid rise of the price. As consequence, rechargeable electrochemical cells based on sodium, designed for the energy storage, are now attracting large interest due to its abundance and low cost. [3,4] We report here the behavior of a sodium-ion battery based on a NaFePO4 cathode, obtained by electrochemical Li-Na conversion of LiFePO4 olivine, and a nanocomposite tin-carbon (Sn-C) alloying anode. [5,6] We show that, by adopting a refined, unique electrochemical process, the LiFePO4 can be successfully and efficiently converted in NaFePO4 and demonstrate that this material can be used as cathode in a sodium-ion battery characterized by the reversible electrochemical process NaFePO4 + SnC = Na(1-x)FePO4 + SnxC with good reversibility and rate capability.