Preparation And Modification Of Sodium Ferrous Silicate For Cathode Materials

This article mainly synthesizes sodium ferrous silicate and performs carbon coating,copper ion doping and titanium ion doping modification to improve its electrochemical performance.The synthesis mechanism,composition,structure and electrochemical properties of composite materials were systematically studied.A carbon-coated nitrogen-hydrogen doped sodium ferrous silicate composite cathode material was prepared through the sol-gel method,using ferrous gluconate as a template and carbon source.The effects of carbon amount,calcination temperature and calcination time on the composition,structure and electrochemical performance of sodium ferrous silicate materials were explored.Studies have shown that the prepared sodium ferrous silicate material containing H-N doped hard carbon nanospheres provide high electron conductivity and more Na ion storage sites.The pore structure makes Na ions and electrolyte easy to penetrate.H-N doping can adjust the surface functional groups of carbon,enhance conductivity,and facilitate charge transfer and electrode-electrolyte interaction.The sodium ferrous silicate composite material with a carbon amount of 7.98 wt%shows high energy/power density,good rate,cycle performance and mixed energy storage mechanism.In the range of 1.2-4.6 V,the initial discharge capacity is 218.4 m Ah g^-1 at 0.1 C.In the 1.5-4.6 V voltage range,the capacity retention rate was 73.8%after 3300cycles at 1 C.The maximum energy density and power density are 331.99 W h kg^-1 and 2431.87W kg^-1,respectively.The copper ion doped sodium iron silicate composite cathode material was prepared by solid phase method assisted sol-gel method using citric acid as the carbon source.The modification mechanism of copper ion-doped sodium ferrous silicate material was explored,and the composition,structure and electrochemical performance of copper ion-doped composite material were studied.Studies have shown that when copper ions are doped with 5%molar amount and calcined at 600°C,the sodium ferrous silicate composite material is composed of irregularly shaped particles with a size of 800 nm-1?m.It has good electrochemical performance,its initial discharge specific capacity reaches 139 m Ah g^-1 at a current density of 10 m A g^-1,which can be mainly attributed to the reduction of charge transfer resistance and the diffusion of sodium ions after copper ion doping coefficient improvement.The titanium ion doped sodium iron silicate composite cathode material was prepared by hydrothermal method assisted sol-gel method using citric acid as carbon source.The modification mechanism of titanium ion-doped sodium ferrous silicate materials was explored,and the composition,structure and electrochemical properties of titanium ion-doped composite materials were studied.The results show that the particle size of the 8%titanium ion-modified sodium ferrous silicate composite prepared at 650?is 800-900 nm,and the surface of the particle is in the shape of a fold coral.As the calcination temperature increases,the crystallinity of the doped sodium ferrous silicate composite also increases,and its structure is more stable,which is conducive to improving its electrochemical performance.At a current density of 10 m A g^-1,the discharge specific capacity of the composite material reaches 128.78 m Ah g^-1.