Electrochemical Performances Of Bi-based Nanocomposites For Sodium Storage

Since 2010,sodium-ion batteries have received extensive attention from academia and industry at home and abroad.As an alloy-based negative electrode material,bismuth has a volume specific capacity(3800 mAh cm-3)and a unique layered structure.However,its violent volume expansion during charging and discharging will cause the structure to collapse and the capacity to decrease.In this paper,the chemical synthesis and sodium storage properties of Bi-C nanocomposites and Bi-Sn@C nanocomposites are studied and discussed.The main contents are as follows:(1)Using solvothermal method and chemical vapor deposition prepares reduced graphene oxide loaded bismuth@carbon composites(CPVP-C2H2/Bi/rGO).The thin carbon layer coated on the surface of the nanoparticles can suppress the huge volume change of Bi.Reduced graphene oxide as a functionalized substrate is conducive to achieving a high degree of dispersion of Bi nanoparticles,while also inhibiting particles aggregation during charging and discharging.The synergy between the amorphous carbon layer,reduced graphene oxide and Bi nanoparticles makes the composite material exhibit excellent electrochemical performance.As a negative electrode material for sodium-ion batteries,CPVP-c2H2/Bi/rGO has excellent sodium storage performances,far better than CPVP/Bi/rGO.After 1200 cycles at a current density of 5 A g-1,a specific capacity of up to 327.6 mAh g-1 can be maintained.The full battery assembled with CPVP/Bi/rGO as the negative electrode and Na3V2(PO4)3/rGO as the positive electrode also shows good electro-chemical performances.(2)The Bi-Sn@C nanocomposite is synthesized for the first time using hydrothermal reaction and chemical vapor deposition,which effectively overcomes the shortcomings of Bi and Sn that are easy to melt and aggregate.As a negative electrode material for sodium-ion batteries,the reversible capacity is 355.8 mAh g-1 after 600 cycles at a current density of 2 A g-1,with a capacity retention of 58.4%.In the rate performance test,at a current density of 10 A g-1,the reversible capacity is 310 mAh g-1.