| Since the 1990s,the lithium-ion batteries have been widely used in the fields of electronic devices and electric vehicles due to their advantages of their high safety,stability,and storage capacity.However,with the increase of lithium-ion batteries usage,problems such as limited lithium resources and rising prices have gradually emerged.Therefore,it is necessary to develop a new generation of energy storage technology that can replace lithium-ion batteries.In recent years,sodium-ion batteries,which have similar electrochemical behavior to lithium-ion batteries,have attracted extensive attention from researchers due to the advantages of abundant sodium metal resources and relatively cheap prices,and are expected to play an important role in future large-scale energy storage systems.However,unlike lithium-ion batteries,sodium ions have a larger ionic radius and higher reduction potential,resulting in some commonly used electrode materials for lithium-ion batteries not being suitable for sodium-ion batteries systems.Especially graphite-based anode electrode materials,which are limited by their interlayer spacing,have proved unsuitable for direct use in sodium-ion batteries.Therefore,the development of anode materials with excellent performance is very important to promote the practicality of sodium-ion batteries.So far,the anode materials of sodium ion batteries that have been developed mainly include hard carbon materials,alloys,metal sulfides and transition metal oxides,but these materials have some problems that need to be solved.For example,the capacity of hard carbon materials is relatively low,and the rate performance and cycle stability of metal sulfides are poor.Based on the advantages of large packing density and high volume specific capacity of spherical materials,this paper prepared hard carbon spheres and sulfide phosphating of cobalt hollow spheres as anode materials for sodium-ion batteries.By improving the conductivity of the materials and the Faraday reaction,etc.The specific capacity and cycle stability of negative electrode materials provide new ideas for the development of high-performance sodium ion battery negative electrode materials.The specific research results are as follows:（1）The carbon nanotubes were assembled on the synthesized 3-aminophenol formaldehyde resin microspheres,followed by high temperature annealing.The composite materials（HCSs-CNTs）connecting hard carbon spheres（HCSs）and carbon nanotubes（CNTs）were successfully prepared.The composite materials has a unique grape cluster-like structure,in which hard carbon spheres have excellent sodium storage performance,carbon nanotubes can provide an interconnected conductive network,thereby ensuring efficient electron transport and electrolyte penetration during batteries charging and discharging,which is beneficial to the specific capacity and rate of anode electrode materials performance improvement.The electrode materials delivers a capacity as high as 151.7 m Ah g-1 after 160 cycles at 0.1 A g-1,the capacity retentions of electrodes after 160 cycles is 76%.It also exhibited outstanding long-life cycling performance with a reversible capacity of95.1 m Ah g-1 after 500 cycles at 1 A g-1,the per cycle capacity decay of electrode after 500 cycles is 0.08%show an excellent long cycle stability.This combination of hard carbon and carbon nanotubes provides a viable way to improve the performance of anode materials for sodium-ion batteries.（2）A two-step hydrothermal method was used to prepare a metal-cobalt sulfide with a core-shell structure,which was then phosphatized and annealed.When the hollow spheres of the core-shell structure is used as a anode electrode of the sodium-ion batteries,it can provide sufficient sodium ion transmission space,and can relieve volume expansion during charge and discharge.The introduction of phosphorus increases the active site and increases the Faraday capacity.The specific capacity of this ternary compound can still reach 633 m Ah g-1 after 100 cycles at a current density of 0.1 A g-1,the capacity retention rate is as high as 85%.With a current density of 2 A g-1,there is still a high reversible specific capacity of up to 456 m Ah g-1 after 400 cycles,the per cycle capacity decay of electrode after 400 cycles is 0.074%,which indicates that the material still has good cycling stability at a large current density.It shows that the material still has good cycle stability under a large current density.This new Co SxPy hollow ball has good development prospects as a negative electrode material for sodium ion batteries. |
