Tin Phosphide And Tin Selenide/Multi-walled Carbon Nanotube Composite Materials As Anode For Batteries

As the energy storage batteries, the importance of lithium-ion batteries and sodium-ion batteries in promoting technology sectors and speeding up economic development becomes more and more obvious. And the requirements for their performance also increase continuously. Because of its high theoretical capacity, tin-based composite materials have become the new milestone in the study field of lithium-ion batteries and sodium-ion batteries. The Sn and P in Sn₄P₃ have electrochemical activity for both lithium and sodium.The high conductivity of Sn can improve the electrical insulating property of P, and the presence of P can disperse the Sn particles. This synergy of Sn and P can alleviate the volume expansion and prevent electrochemical reunion.The layer structure and unique properties of Sn Se make it behave outstanding in the filed of lithium-ion batteries and sodium-ion batteries.In this paper, Sn₄P₃ and Sn Se were prepared by microwave solvothermal method. In order to improve their electrochemical properties, carbon nanotubes are incorporated into them to prepare the composite materials with the same method.The specific research contents are as follows:（1） The Sn₄P₃, Sn Se,Sn₄P₃/MWCNTs composite and Sn Se/MWCNTs composite are prepared by microwave solvothermal method, respectively. The phases and morphologies of the products were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.（2） The Sn₄P₃ and Sn₄P₃/MWCNTs are set as the anodes for lithium-ion batteries and sodium-ion batteries to study the mechanism of lithium and sodium storage by using cyclic voltammetry. Besides to research their cycle performance, variable current charge-discharge test, the constant current charge-discharge test and AC impedance test are used. The study found that the cycle performance of Sn₄P₃/MWCNTs is better than Sn₄P₃. In the lithium-ion battery testing process, When Sn₄P₃/MWCNTs =3/1, the cycle stability is the best. The Sn₄P₃/MWCNTs =3/1 anode can deliver a initial discharge capacity of 1506 m Ah/g and a coulombic efficiency of 62% at the current density 500 m A/g. After 100 cycles, the capacity is 440 m Ah/g. In the sodium-ion battery testing process, the cycle performance of Sn₄P₃/MWCNTs is also better than Sn₄P₃. When Sn₄P₃/MWCNTs =1/1, the cycle stability is the best. The Sn₄P₃/MWCNTs =1/1 anode can deliver a initial discharge capacity of 1092 m Ah/g and a coulombic efficiency of 53% at the current density 200 m A/g. After 100 cycles, the capacity is 234 m Ah/g.（3） The Sn Se and Sn Se/MWCNTs are set as the anodes for lithium-ion batteries and sodium-ion batteries to study the mechanism of lithium and sodium storage, by using cyclic voltammetry. Besides to research their cycle performance, variable current charge-discharge test, the constant current charge-discharge test and AC impedance test are used. The study found that the cycle performance of Sn Se/MWCNTs is better than Sn Se. In the lithium-ion battery testing process, the Sn Se/MWCNTs =1/2 anode can deliver a initial discharge capacity of 2244 m Ah/g and a coulombic efficiency of 68% at the current density 100 m A/g. After 100 cycles, the capacity is 908 m Ah/g. In the sodium-ion battery testing process, the Sn Se/MWCNTs =1/2 anode can deliver a initial discharge capacity of 1721 m Ah/g and a coulombic efficiency of 50% at the current density 100 m A/g. After 100 cycles, the capacity is 366 m Ah/g.