The Preparation And Properties Of Sodium Iron-Manganese Doping Cathode Materials And Graphene-Coating Sodium Titanium Phosphate Anode Material For Sodium Ion Batteries

Rechargeable lithium-ion batteries（LIBs） have governed portable electronic devices because of their high energy density, long-life and safety. Recently, sodium ion batteries（NIBs） have been popular in global energy due to material-abundant and low price, and have prospects in large energy storage devices such as smart grids and electric vehicles. As the critical technology in NIBs, a great number of studies have been reported for electrode materials. The cathode materials can be classified into layered transition metal oxides and polyanion and the categorys of anode materials are carbon, alloys and titanates. P2-Na_0.67[Fe_0.5Mn_0.5]O₂ is a kind of potential cathode material with low-cost and high capacity but is poor in cycling stability and experience fast decay during cycling; due to the low electronic conductivity, the polyanion NaTi₂（PO₄）₃ has bad electrochemical performance in despite of its three-dimensional space structure and good transport channel. In order to improve the cycle stability of P2-Na_0.67[Fe_0.5Mn_0.5]O₂ and the electronic conductivity of NaTi₂（PO₄）₃, the followed research works have been carried out in this paper:（1） The P2-Na_0.67[Fe_0.4Mn_0.55Zn_0.05]O₂ was prepared by solid state method through the substitutes for transition metal ions Fe by a small amount of Zn in P2-Na_0.67[Fe_0.5Mn_0.5]O₂; The P2-Na_0.67[Fe_0.2Mn_0.65Ni_0.1Zn_0.05]O₂, P2-Na_0.67[Fe_0.1Mn_0.7Ni_0.15Zn_0.05]O₂ and P2-Na_0.67[Fe_0.1Mn_0.7Ni_0.1Zn_0.1]O₂ were prepared by solid state method through the substitutes for Fe or Mn by a small amount of Zn in P2-Na_0.67[Fe_0.2Mn_0.65Ni_0.15]O₂. The materials were characterized by SEM and XRD methods, and the electrochemical performances were performed by batteries assembled. The doping was not work in P2-Na_0.67[Fe_0.5Mn_0.5]O₂ but the cyclability of P2-Na_0.67[Fe_0.2Mn_0.65Ni_0.15]O₂ have improved after substitution by Zn.（2） A graphene encapsulated NaTi₂（PO₄）₃ composite（NaTi₂（PO₄）₃-rGO） has been synthesized by self-assembly method by the reaction of the peptide bond synthesis. The materials were characterized by SEM and XRD methods, and the electrochemical performances were performed by batteries assembled. The NaTi₂（PO₄）₃ had low initial capacity and decayed rapidly without carbon-coating; the NaTi₂（PO₄）₃-rGO had a good cycle stability at 1C rate.