| With the rapid development of the current social economy,mankind's demand for energy is increasing day by day.However,fossils and other non-renewable energy sources not only have limited reserves,but also cause serious environmental pollution problems.As an energy storage power source,the development of lithium/sodium ion batteries has received more and more attention.Anode materials play an important role in lithium/sodium ion batteries,so they have become a hot spot in the field of energy storage in recent years.Among them,the high theoretical capacity of the transition metal oxide tin-based oxide and the high environmental protection,low cost and high carbon content of lignin have aroused the interest of the majority of scientific researchers.In this thesis,tin dichloride dihydrate is used as a precursor,and a self-built gas-electric blending device is used to obtain nanofiber cloth,which is then calcined in air and hydrothermally treated to prepare a nitrogen-doped tin dioxide battery anode material.And explore the effect of different nitrogen doping on the structure and electrochemical performance of tin-based materials.It is found that the fiber structure prepared by the gas-electric blending effectively inhibits the volume expansion/shrinkage of SnO2during cycling,and a certain amount of nitrogen doping and the presence of graphene make the SnO2/NG composite material have good electrochemical performance.The results show that when the ratio of tin dioxide to nitrogen doping is 1:100(ie SnO2/NG-100),the electrochemical performance of the material is optimal.Used in lithium-ion batteries,at a current density of 234 m A/g,its first reversible specific capacity is 728.9 m Ah/g,coulombic efficiency is 49.92%,and it can still be maintained at 677.7 m Ah/g after 100cycles;when used in sodium-ion batteries At a current density of 100 m A/g,the first reversible specific capacity of the composite material is 157.3 m Ah/g,and the specific capacity remains at 169.7 m Ah/g after 100 cycles,all of which have good electrochemical performance.This paper also selects lignin as the carbon precursor,PVP as the spinning agent,Mg(NO3)2·6H2O as the pore former,and the gas-electric blending with 0.1 g graphene and16 g DMF.The blended nanofibers are pre-oxidized,carbonized-activated,pickled and dried to obtain graphene-doped porous lignin carbon nanofibers.Explore the ratio of Mg(NO3)2·6H2O doped with the best electrochemical performance.It was found that the porous lignin carbon nanofibers have excellent flexibility and self-supporting structure,without any conductive agent and binder,and can be directly used as the negative electrode of lithium/sodium ion batteries.The results show that when the ratio of lignin to Mg(NO3)2·6H2O is 1:2(ie LCNF/G-2),the electrochemical performance of the material is optimal.Used in lithium-ion batteries,at a current density of 200 m A/g,the first reversible specific capacity is 1783.8 m Ah/g,and the coulombic efficiency is 54.09%;after 50 cycles,the specific capacity is 1429.7 m Ah/g,and the coulombic efficiency is 96.32%,which is reversible.The capacity retention rate is 80.1%.At a high current density of 2 A/g,the first cycle showed an excellent reversible specific capacity of 1135.4 m Ah/g,and it remained at1064.7 m Ah/g after 100 cycles;when used in a sodium-ion battery,at a current density of100 m A/g,Its first reversible specific capacity is 511 m Ah/g,coulombic efficiency is24.35%;after 100 cycles,the specific capacity is 375 m Ah/g,coulombic efficiency is97.2%,reversible capacity retention rate is 73.4%,both have excellent cycle stability and good rate performance.This is related to the high specific surface area(628.09 m2/g)and pore volume(0.4302 cm3/g)of LCNF/G-2. |
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