Design And Synthesis Of Bi Based Composites For Sodium-ion Battery

Sodium ion batteries(SIBs)have been considered as the next generation of energy storage alternatives for extensive applications because of their ample natural resources,low price,and similar electrochemical behavior to lithium.Nevertheless,the development of SIBs still faces many challenges owing to the large ionic radius of sodium ions.Therefore,it is a central task to design and synthesis of anode materials with superior cycling stability and high reversible capacity for advance the commercialization of SIBs.Bismuth-based materials,mainly represented by Bi and Bi2S3,are highly favored by scientists due to their amazing theoretical capacity,and they also have very great advantages in terms of storage capacity and safety.However,the bismuth-based electrode materials suffer from low electrical conductivity,serious volume expansion during the sodiation/de-sodiation,and slow charge transfer kinetics inevitably results in unsatisfactory performance,thereby limiting their application in SIBs.Thus,focusing on the above challenges,this paper is devoted to the design and synthesis of bismuth-based electrode materials and solve the key problems in practical applications of sodium storage performance,thereby effectively improving the performance of bismuth-based materials in sodium ion batteries.The specific research contents are as follows:1.Firstly,we designed an abundant heterointerface of Bi/Bi2S3 in engineering structure of Bi nanoparticles embedded on Bi2S3 nanorods(Bi-Bi2S3 NRs),which selected bismuth nitrate as the bismuth source and 1,3,5-mercaptoazolium as the sulfur source.Benefiting from the constructed built-in electric field and strong coupling between Bi and Bi2S3,which largely accelerate the charge transfer ability and restrict the volume variation,thereby presenting excellent electrochemical performance.Specifically,it can deliver long cycling life with an ultra-high capacity of 500 mAh g-1 after 500 cycles at 1 A g-1 and an excellent rate capability with a capacity of 456 mAh g-1 even at 15 A g-1.The full-cell battery assembled by Na3V2(PO4)3/C(NVP/C)cathode and Bi-Bi2S3 NRs anode can provide a high energy density of 180 Wh kg-1.2.Secondly,we design extremely simple material synthesis strategy with homophthalic tricarboxylic acid,bismuth nitrate pentahydrate and tin tetrachloride pentahydrate as carbon source,bismuth source and tin source.And we successfully constructed the unique composites with core-shell structure of biphasic alloy Bi@Sn nanospheres loaded on carbon layer(Bi@Sn/C).Benefiting from their specific structural and compositional advantages,which effectively increases the electron conductivity,shortens the sodium ion transport path,and mitigates the volume expansion effect.Both the button half-cells and full cells assembled by Bi@Sn/C exhibits superior sodium ion storage performance.Specifically,it delivers a high reversible capacity of 428 mAh g-1 at 0.1 A g-1 and ultra-stable cycling capability with a capacity retention of 90%at 1 A g-1 over 1000 cycles for Na+ storage.Moreover,the Na3V2(PO4)3//Bi@Sn/C full-cell(the commercial Na3V2(PO4)3 as cathode)can provide an outstanding energy density of 178 Wh kg-1.