Application Of Sodium Terephthalate As Anode Electrode For Sodium-ion Batteries

Sodium ion batteries?SIBs?,characterized with similar working principle with lithium ion batteries?LIBs?but lower cost,have attracted the attention of scientists worldwide.As key component of SIBs,the anode materials range from carbon-based materials,titanium-based materials,transition metal oxides,alloy materials to organic materials.Among those materials,organic anode materials have been paid increasing attention owing to their high theoretical specific capacity,low cost,as well as suitable charge-discharge potential.However,the low conductivity of the organic anode materials seriously impede the cycling and rating performance as anode for SIBs.Correspondingly,this work focuses on improving the electrochemical performance of sodium terephthalate?Na₂TP?as anode for SIBs through tailoring the particle size and carbon coating.The main work and results in this thesis include:Firstly,Na₂TP was prepared by acid-base neutralization method and was applied as the anode electrode material for SIBs.The results show that Na₂TP can be anode candidate for SIBs considering its reasonable charge-discharge platform?0.25/0.5 V?,high specific capacity and good cycling performance.It is also found that 0.5 M NaCF₃SO₃?diglyme?solution can be selected as the electrolyte for Na₂TP anode for SIBs.Secondly,Na₂TP with different sizes were synthesized by anti-solvent method.The effect of particle size on its electrochemical performance was subsequently studied.The electrochemical performance of Na₂TP improves with decreasing particle size,with 8?m particles rendering the best electrochemical performance in terms of first cycle reversible specific capacity of 220.1 mAh/g and 167.3 mAh/g after 50 cycles.Smaller particle size increases the contact area of the material with the conductive additive as well as the electrolyte,and shortens the diffusion route of Na⁺,leading to enhanced electrochemical performance.Lastly,Na₂TP@r-GO composite was synthesized with graphene oxide?GO?dispersion as carbon source by spray drying method.The cycling and rating performance of Na₂TP@r-GO composite as anode for SIBs was studied.The specific capacity remains at 200 mAh/g at a charge-discharge rate of 5C after 100 cycles.Furthermore,Na₂TP@r-GO electrode shows high specific capacity of 280,260,240,225,and 245 mAh/g at 1C,2C,5C,10C,and 1C,respectively,which displays better rate capability than Na₂TP.The three dimensional r-GO conductive network,the uniform distribution of nano Na₂TP particles in the r-GO substrate are contributing to the remarkably improved cycling and rating performance of Na₂TP@r-GO composite anode.