Research Of Polyanion-type Cathode Materials For Sodium Ion Battery

As the renewable energy such as wind energy,solar energy,tidal energy and so on are intermittent and random,they often can't meet the demand of energy supply,which must be in time,effective and stable.Therefore,the development of efficient and convenient energy storage technology has become a research focus in every country.At present,lithium-ion batteries have occupied the main market of portable mobile electronic devices,and have important applications in electric vehicles as well as energy storage systems.With the large-scale application of lithium-ion batteries,the demand of lithium will be more and more,but the limited lithium resources in crust cannot meet our growing demand.Sodium and lithium are located in the same main group with similar physical and chemical properties,and sodium element in the crust is abundant,easy to refine?the ocean contains a lot of sodium?.Therefore,sodium ion batteries have a great advantage in application of chemical power supply in the future.In this article,we chose Na₃V₂?PO₄?₃ and Na_2.4Fe_1.8?SO₄?₃ as the research object.The Na₃V₂?PO₄?₃/C was prepared by ball milling and coated with chitosan as carbon source,and the electrochemical properties had been characterized.The results showed that the carbon from chitosan formed conductive network in the Na₃V₂?PO₄?₃/C materials,which greatly increased the electrical conductivity of Na₃V₂?PO₄?₃.The sample with 30 wt%carbon theoretically showed relatively superior electrochemical performance.At the current of 1 C,the specific discharge capacity was 115.01 mAh g^-1,and after 200 cycles,the specific capacity was 107.21 mAh g^-11 with a cycle retention of 93.2%.The discharge capacity was 92.74 mAh g^-1 at 2 C current density and 79.02 mAh g^-1 after cycled 200times with a cycle retention of 85.2%.The Na₃V₂?PO₄?₃/C showed stable cycling performance.The Na_2.4Fe_1.8?SO₄?₃ was prepared by ball milling,and the Na_2.4Fe_1.8?SO₄?₃/PEDOT composite was synthesized by conductive polymer PEDOT and Na_2.4Fe_1.8?SO₄?₃.The effect of the addition amount of the conductive polymer?PEDOT?on the performance of Na_2.4Fe_1.8?SO₄?₃/PEDOTwasinvestigated.Theresultsshowedthatthe Na_2.4Fe_1.8?SO₄?₃/PEDOT cathode material with 40%conductive polymer had the highest discharge specific capacity which was 118.1 mAh g^-1 at the current of 0.05 C.