Preparation And Sodium Storage Properties Of Bismuth Sulfide Nanocomposites

Sodium ion batteries can meet the demand of large-scale energy storage system due to their huge abundant of raw materials and low cost,and have attracted great attention.It is crucial to develop robust anode materials with high specific capacity and long cycling life toward practical applications of sodium ion batteries.Used as anode of sodium ion batteries,Bi₂S₃ has many advantages.For example,it deliveries a high specific capacity of 626 m Ah g^-1;the low volume expansion reaches 250%during the sodiation process;the product Na₂S of conversion reaction can play a role as buffer layer to accommodate the volume change during the charge and discharge.It is important to enhance electronic conductivity and eliminate the effect of the volume change of Bi₂S₃.In this article,Bi₂S₃ composites are successfully constructed with different methods,which have better electronic conductivity and ability to restrain the volume change to improve the cycle performance.The work mainly includes as follows:?1?The Bi₂S₃ nanotubes were prepared through a solvothermal method firstly.At the same time,the effect of the additive agent including glycine and carbamide during the reaction process was investigated.Then the Bi₂S₃ nanotubes was coated with carbon?Bi₂S₃@C?and titanium dioxide?Bi₂S₃@TiO₂?,respectively.The Bi₂S₃@C material exhibited specific capacities of 91.97 m Ah g^-1and 73.98 m Ah g^-1after 100 cycles at the current density of 0.1 A g^-1and 1.0 A g^-1,respectively.The Bi₂S₃@TiO₂ material exhibited specific capacities of 139.33 m Ah g^-1and 116.09 m Ah g^-1after 100 cycles at the current density of 0.1 A g^-1and 1.0 A g^-1,respectively.Both of the composites have a better cycle performance and rate performance compared to the single Bi₂S₃ nanotubes.?2?Bi₂S₃ nanorods are anchored on reduced graphene oxied through a facile one-step hydrothermal method.The Bi₂S₃ exhibits a nanorod-like morphology with a length of 500 nm⁶00 nm and a diameter of about 50 nm in the composite.The size of the product obtained through the hydrothermal reaction without graphene,is larger than the nanorods in composite,which demonstrates the addition of the graphene effectively ruduces the size of the Bi₂S₃ nanorods.And the addition of graphene also further enhances the electronic conductivity of the composites,which also make the nanorods have a better dispersion to prevent further agglomenration.Bi₂S₃/rGO nanocomposite exhibit better cycle performance than the single Bi₂S₃ nanorods.A discharge capacity of 306.57 m Ah g^-1still could be remained after 50 cycles at 0.1 A g^-1.And the composites deliveries a high reversible specific capacity of 284.76 m Ah g^-1after 100 cycles.A discharge capacity of 291.80 m Ah g^-1could be delivered at 2.0A g^-1from the excellent rate performance of Bi₂S₃/rGO.