Interfacial characteristics of Na2FePO4F and its carbon coated material for lithium/sodium hybrid ion battery

The interfacial characterization of the cathode material Na 2 FePO 4 F with carbon capping material Na 2 FePO 4 F@C taking bagasse as the carbon source is reported. Both the higher-capacity Na 2 FePO 4 F@C material (93 mAh/g) and lower-capacity Na 2 FePO 4 F material (10 mAh/g) showed different degrees of capacity decay during cycling. The rupture and spontaneous repair process of the solid electrolyte interface (SEI) film resulting in increased impedance and blocked charge transfer, as well as irreversible changes in the surface microstructure of the electrode material after cycling, which are responsible for the decrease in capacity. The XRD and FTIR results before and after cycling shown that the characteristic peaks of the carbon coated material Na 2 FePO 4 F@C and raw material Na 2 FePO 4 F were consistent, indicated that their functional groups and crystalline structures are not the main causes of capacity decay at low cycling times (within 50 cycles).