Study Of Modified Silicon / Graphite Anode Materials Of Lithium Ion Battery

This paper we use ball milling method to treat silicon.and then, using silane coupling agent to modify the surface of silicon, in order to improve the electrochemical performance of silicon to a certain extent.Another research content of this article is to use silane coupling agent modified raw silicon and graphite composite, to get good stability, high capacity anode materials of battery. Then the different proportions of modified the Si O/graphite composite materials was studied.In this article, we choose the industrial grade silicon powder(200 mesh),because of its low cost,easy preparation.First,we use ball milling method to made materials,then use silane coupling agent KH 570 to modify silicon powder.Graphite is the most used cathode material in lithium ion battery,it has many characteristics such as small volume change, low electronic conductivity that can satisfy the requirement of lithium ion battery anode materials.However,its lower theory embedded specific capacity has limited its application.Another research of this article is to use the silicon modified with silane coupling agent KH570 mixing with graphite, and then the modified silicon/graphite cathode materials prepared.In this kind of composite materials, silicon can satisfy the demand for high capacity,graphite can not only make up for the shortcomings of low electrical conductivity of silicon, but also can buffer the huge volume change of silicon material, as a result raising the battery performance of the anode materials.We use ball-milling method to prepare the sample sized in 0.5~2um.The first charge and discharge specific capacity were 2019.71 m Ah/g and 3637.34 m Ah/g, the initial coulombic efficiency is 55.53%; after 50 cycles, the reversible capacity is 463.50 m Ah/g.After modified by silane coupling agent KH570 the first charge and discharge specific capacity of silicon powder were 2768.90 m Ah/g and 3647.49 m Ah/g, the initial coulombic efficiency is 75.91%, after 50 cycles, the reversible capacity still have 1450.05 m Ah/g, compared with the silicon powder before modification, the modified silicon is better to improve the cell electrochemical performance.The modified silicon is respectively mixed with two kinds of graphite( graphite GHMG and graphite SMG- JCS- 1S),the mass fraction of modified silicon is 5%, 10%, 15%, 10%, 25%, 30%, 25% and 40%,then to study the electrochemical properties of the composite material.For the modified silicon/SMG- JCS- 1S, when the mass fraction of the modified silicon is 25%, the composite material has better performance, and has relatively high capacity; The first reversible capacity is 969.77 m Ah/g, the initial coulombic efficiency is 88.22%; After 50 cycles, the reversible capacity is 448.73 m Ah/g.For the modified silicon/GHMG, the better mass fraction of the modified silicon i s 15%, the first reversible capacity is 740.65 m Ah/g, the initial coulombic efficiency is 82.03%; After 50 cycles, the reversible capacity is 466.72 m Ah/g.