In Situ Construction And Lithium/Sothium Storage Properties Of Three-dimensional Porous Carbon And Tin-based Alloy Nanostructure

With the great development of electronic vehicle(EC),smart power grids and large-scale energy storage technology,the demands on energy density and power density of lithium ion batteries(LIBs)are increasing.At the same time,the problems of rare reserve and high price of lithium are also focused.Therefore,on the one hand,it's necessary to improve the electrochemical performance of lithium ion battery;on the other hand,it's also quite important to implore new energy storage technology.Sodium ion batteries(SIBs)own the similar physical and chemical property with LIBs,and they show abundant reserves and low price,which made them the most important candidate for the secondary battery.In order to prepare LIBs and SIBs with perfect electrochemical performance,the most important thing is to explore excellent electrodematerials with high capacity,good rate performance,long lifetime and low price.As the most widely used anode material,carbon owns many advantages such as abundant reserves,high conductivity and high stability.But the theoretical capacity of carbon is not quite high.In contrast,alloy electrode material especial Sn expresses super high capacity.However,because of its terrible volume expansion,a poor structure stability and fast capacity attenuation alwaysappear,which hampered its practical application.Focus on the problems mentioned above,three dimension(3D)porous carbon with N/B doping,Ni-Sn/C and SnSb/C composites have been synthesized by template-assisted in situ pyrolysis method.The electrochemical performance and storage mechanism of LIBs and SIBs with the obtained anode were discussed.The specific research contents are list as follows:(1)N-doped 3D porous carbon is synthesized by template-assisted in situ pyrolysis method,using citric acid/glucose as carbon resource,urea as nitrogen resource,and sodium chloride(NaCl)as template.The results show that N has uniformly doped into 3D porous carbon with a high content of 12%.N-doped 3D porous carbon with high specific surface area of 265?425 m2.g-1 exhibits higher capacity,excellent cycle performance and perfect rate capacity compared with 3D porous carbon without N doped(at 0.1 A·g-1 after 100 cycles:416 mAh·g-1;at 5 A·g-1:213.8 mAh·g-1).(2)B-doped 3D porous carbon is synthesized by template-assisted in situ pyrolysis method,using citric acid as carbon resource,boric acid as boric resource and template,and sodium chloride(NaCI)as another template.B-dope 3D porous carbon exhibits high capacity,excellent cycle performance and perfect rate performance in both LIBs(at 0.1 A-g-1 after 100 cycles 460 mAh·g-1;at 5 A·g-1:220 mAh·g-1)and SIBs(at 0.1 A·g-1 after 100 cycles:200 mAh·g-1;at 5A·g-1:127 mAh·g-1).(3)In order to take full advantage of the high capacity of Sn and high conductivity and stability of 3D porous carbon,Ni-Sn/C composite is synthesized by template-assisted in situ pyrolysis method,using NaCl as template.The results show that nano Ni-Sn(Ni3Sn2 and Ni3Sn4)particles(10?30 nm)are uniformly dispersed on 3D porous carbon.The strong bonding force between Ni-Sn and C is ascribed to the in situ pyrolysis method.The 3D porous structures provide enough space for the volume expansion of Sn.Meanwhile,the carbon shell outside Ni-Sn nano alloy restricted the growth and agglomeration of NiSn nano particles.The Ni-Sn/C composites exits excellent cycle performance and rate performance in LIBs(at 0.5 A·g-1 after 200 cycles:732 mAh-g-1;at 5 A·g-1:377 mAh-g-1).Because of the existence of non-electrochemical activity of Ni,Ni3Sn4/C exhibits more perfect electrochemical performance than Ni3Sn2/C.(4)In order to further improve the electrochemical performance of Sn-based materials,SnSb@SnOx/SbOX@C is synthesized.The results show that SbSn are uniformly dispersed on the carbon,and yolk-shell structures are formed.The XPS results show that SnSb nano particles were coated with tin oxide/antimony oxide and carbon.The unique yolk-shell structure can restrain the aggregation and grow of SnSb particle,and then reduce the volume expansion,improve the cycle and rate performance.This design not only take full advantage of the high capacity of Sn base materials,but also provide enough space to tolerate the volume expansion,increase the wettability of electrolyte,shorten the diffusion path of ion,and improve the conductivity of the materials.As a result,the as-prepared sample exhibits excellent electrochemical performance in LIBs(1A·g-1 after 200 cycles:600 mAh·g-1)and in SIBs(0.1 A·g-1 after 200 cycles:359.2 mAh·g-1,1 A·g-1 after 500 cycles:194.9 mAh·g-1).