Preparation And Electrochemical Properties Of Silicon Based Composites As Anode Materials For Lithium Ion Battery

With the increasing depletion of non renewable energy and the rapid development of the society,it is very important to find cleaner energy storage equipments.Graphite as the commercial negative material,its lower theoretical capacity is unable to meet the future demand for large capacity,faster charging battery materials.Silicon based anode materials have a great opportunity to become the next generation alternative to graphite,owing to its unique chemical and physical properties.In view of the high charge and discharge capacities of silicon based anode materials in the application,the problem of rapid capacity fading encountered during cycling is studied in order to improve its performance stability.Double coating of silicon based anode material is prepared by two step ball milling with micron silicon,potassium ferrate and graphite as raw materials.First,potassium ferrate and graphite are used for ball milling,and graphite was successfully stripped through the strong oxidation of potassium ferrate to obtain few-layered graphene.Then,the micron silicon with dual-coating structure?few-layered graphene and amorphous iron oxide coated?is successfully obtained by mixed milling of micron silicon,few-layered graphene and potassium ferrate.At room temperature,the composite material exhibits a reversible capacity of 637 mAh g^-1 at the current density of 2 A g^-1 after 1600 cycles,low capacity fading of0.012%per cycle from tenth circle and a reversible capacity of 572 mAh g^-11 under the current density of 8 A g^-1,showing excellent rate performances.Some reasons for the long-term cycling of silicon based anode materials and the changes of energy storage are found through the study.There is a indepth understanding of the energy storage process of silicon based anode materials.Considering that composites fabricated by the different ratios of silicon/carbon,the factors of silicon content on the electrical properties of composites are investugated.By comparing the rate performances,cycling performances and EIS,it is found that the composites made from 12g silicon powder,4g few-layered graphene and 4g potassium ferrate as raw material has the best electrochemical performance.