High Performance Anode Materials Fabricated By Mechanical Stripping Method For Rechargeable Lithium-ion Batteries

Recently, graphite used as an anode materials in commercial Li-ions battery has large irreversible capacity loss and serious safety issues. Compared with graphite, transition metal oxides as a series of new materials with excellent safety performance and high theoretical specific capacity have attracted the widespread attention. However, facing with the preparation cost and electrochemical performance issues especially the cost and the high-rate performance is difficult to coordinate, have greatly restricted the scope of application of thest material. In this thesis, the cheap high performance material were prepared by a novel method of mechanical exfoliation to provide a technical reference for expanding the application of these anode materials.The focus of this paper is modification and study on lithium storage mechanism of layered structures of transition metal compounds in tin disulfide (SnS2) and molybdenum disulfide (MoS2) and research the mechanism of lithium storage. Morever, the porous carbon material is also simply studied.(1) The layered structure of SnS2 is changed into SnS2 nanoparticles through mechanical stripping method including ball milling, ultrasonic and centrifugal. Then, SnS2 nanoparticles and graphite oxide (GO, through the preparation of Hummers method) are made into a compound, the hydrothermal method finally SnO2/GAs nano composite. Finally, the SnO2/GAs nano composite material is obtained by hydrothermal method. The electrode materials have excellent electrochemical performance, when the content of SnO2 nanoparticles is 57.34%. At a current density of 100 mA/g, the electrode materials have good discharge specific capacity as high as 1086.7 mAh/g after 100 cycles and cycle stability; when the current density up to 800 mA/g, the discharge specific capacity is still as high as 447.9 mAh/g, and when current density returns to 100 mA/g, the discharge specific capacity is once again restored for 784.4 mAh/g.(2) The layered structure MoS2 is successfully stripped by mechanical stripping method, and then stripped MoS2 is heat-treated for 3h under the condition of air in order to get the pure a-MoO3 phase. If the time extended, there will be a reunion phenomenon of material. The MoO3 nanoparticles are got through a heat-treated process of MoS2 (after centrifugation,5000 rpm). Then, MoO3 nanoparticles and graphite oxide are made into a compound. Finally,the MoO3/GAs nano composite materials is obtained. The nano composite materials has excellent electrochemical performance, when the content of MoO3 is 33.95%. The electrode materials have good discharge specific capacity as high as 1194.2 mAh/g after 100 cycles and cycle stability; when the current density up to 800 mA/g, the discharge specific capacity is still as high as 867.8 mAh/g, and when current density returns to 100 mA/g, the discharge specific capacity is once again restored for 1134.4 mAh/g.(3) The mesoporous porous carbon materials is successfully synthesized, the colloidal silica (SiO2) as a template, o-phenylenediamine (OPD) as carbon precursor. Used as anode materials for lithium ion batteries, this material showes excellent cycle performance. The electrode materials have good discharge specific capacity as high as 546.5 mAh/g after 100 cycles and cycle stability. At a current density of 800 mA/g, the discharge specific capacity is still as high as 300 mAh/g, and when current density returns to 100 mA/g, the discharge specific capacity is once again restored for 540 mAh/g.