Enhanced electrochemical performance of graphitic carbon-wrapped spherical FeOF nanoparticles using maleopimaric acid as a cathode material for sodium-ion batteries

Sodium-ion batteries(SIBs)are considered one of the most promising energy storage systems for replacing lithium-ion batteries because of the high abundance and low cost of sodium.Iron oxyfluoride(FeOF)is a promising conversion-based cathode material for SIBs because of its high theoretical capacity of about855 mA h g^(-1),low-cost chemical compositions,and its lower sensitivity to the size of charged carrier ions.However,the poor electrical conductivity and ionic diffusion of FeOF result in a low rate capability and cyclability.In this work,FeOF nanoparticles wrapped by graphitic carbon layers were synthesized using abietic or maleopimaric acid as both the carbon source and organic ligand.In addition,the morphology of the FeOF particles was gradually controlled from rod to spherical shapes,simply depending on the rosin acids.The FeOF nanoparticles prepared with maleopimaric acid showed a large reversible discharge capacity of 356.7 mA h g^(-1)with a fading rate of 0.21%per cycle after 100 cycles at a current density of 100 mA g^(-1)and an excellent rate capability.