Morphology Design And Property Research Of Anode Materials For Tin Phosphide Lithium Ion Battery

Energy storage still plays an important role in clean energy recycling of human society.Rechargeable lithium ion batteries have been expected to power a variety of electronic equipments,hybrid electric cars and space vehicle due to good rate performance,long lifespan and reliable safety.However,the theoretical capacity of traditional commercial carbon materials is only 372 mA h g^-1,which is hard to meet the demand for the high energy density and power electrical equipments.Hence,new anode materials with higher theoretical capacity are explored and study to improve the performance of lithium ion batteries.As a kind of transition metal phosphating,Sn₄P₃exhibits super high theoretical capacity(1225 mA h g^-1),good lithium alloying and decomposition reaction,relatively lower charge-discharge voltage,metallic character and good thermal stability.Hence,it is chosen to be a new anode material.But,huge volume expansion results in peeling of the active material from the collector and the Sn nanoparticles agglomeration lead to the fast capacity fade during the prolong cycles process.The challenges severely limit the application of Sn₄P₃ as anode material for lithium ion batteries.In order to address the problem of volume expansion and Sn agglomeration,Sn₄P₃and carbon composite were synthesized.Firstly,the carbon shell can not only accommodate the volume change of Sn₄P₃,but also increase the electrical conductivity of active material.Secondly,Li₃P with the structure of host matrix formed during the first discharge prevents Sn agglomeration.Based on this,the battery performance of Sn₄P₃ is significantly improved.In this paper,MnO_x nanowires severe as template,the monodisperse Sn₄P₃ nanoparticles embedded in mesoporous carbon with the hollow tubular structure?Sn₄P₃@mC?synthesized by template-hydrothermal-phosphidation.When tested as anode materials for lithium ion batteries,Sn₄P₃@mC demonstrates significantly enhanced electrochemical performance in terms of good rate capability,long cycling life,and high reversible capacity with 878 mAh g^-1 after 400 cycles at current density of 0.2 A g^-1.In addition,a reversible discharge capacity of 745 mAh g^-1can be obtained after 250 cycles at 1 A g^-1.An electrochemical kinetic analysis reveals that the lithium ion charge storage depends on the capacitance-controlled behavior,with a high capacitive contribution of 74.3%for the total capacity at 1 mV s^-1.In additional,we also design a hollow hexahedral carbonaceous material coated with Sn₄P₃ active material to improve the electrochemical properties.Firstly,solid ZnSnO₃ is coated with a thin layer of glucose by hydrothermal method,and then carbonization under Ar atmosphere.Sn₄P₃@C with hollow hexahedral structural is formed by Na₂EDTA treatment and phosphation.The battery performance was tested,Sn₄P₃@C can achieve reversible 531 mA h g^-1 after 200 cycles at the current density of 0.2 A g^-1.The average capacity attenuation rate per cycle is only 0.1839%,which achieve a better battery cycle performance.