Investigation Of Nickel-based And Silicon-based Nanoscale Anode Materials

The rapid development of new energy vehicles urgently needs the research of high capacity, long life, good safety for lithium ion battery electrode materials. This paper prepares three kinds of anode materials:MnO₂ and Ni（OH）₂ composite which grew on the Nickel Foams （Ni（OH）₂/MnO₂）, silicon/graphene composite （Si/Graphene） and nano silicon/polyaniline hydrogel composites （Si/PANi）. The structure and morphology of the materials are characterized by XRD, SEM and TEM. The electrochemical properties of the materials are also studied by constant current charge discharge, cyclic voltammetry and AC impedance.Ni（OH）₂/MnO₂ composites are prepared by hydrothermal method, and the material is prepared by using nickel foam as substrate, without the use of binder and conductive agent. The effects of different reaction time on the morphology and electrochemical properties of the composites are explored. The results show that when the reaction time is 6 hours, MnO₂ coated Ni（OH）₂ core/shell composite which grew on the Nickel Foams （CS Ni（OH）₂@MnO₂ NFs） composite is a 3D core/shell structure with unique caterpillar morphology, and it has the best electrochemical performance. At the current density of 200 mA g-1, the first discharge capacity of CS Ni（OH）₂@MnO₂ NFs is 2223 mAh g-1, and the discharge capacity of composites still has 1210 mAh g-1 after 80 cycles. When the current density is 1000 mA g-1, the first discharge capacity of CS Ni（OH）₂@MnO₂ NFs is 1541 mAh g-1, and the discharge capacity still has 650 mAh g-1 after 100 cycles.Graphene oxide is prepared by the improved Hummers method and the Si/Graphene composite is prepared by high temperature reduction. When the reduction time is 2 hours, with the surface active agent PVP added in, the composite has the best electrochemical performance. At the current density of 100 mA g-1, the first discharge and charge capacity of Si/Graphene composite are 1359 mAh g-1 and 880 mAh g-1, respectively. After 40 cycles, it still has 442 mAh g-1.The Si/PANi hydrogel composite is prepared by in-situ polymerization method, which directly coated on the copper foil without using adhesive and conductive agents to made electrode. The Si/PANi composites show a high specific capacity and good cycle stability as well as the rate performance. At the current density of 200 mA g-1, the initial discharge capacity of Si/PANi composite is 1379 mAh g-1, and the discharge capacity of composite still has 609 mAh g-1 after 70 cycles. When the current reverted to 200 mA g-1 after 200 mA g-1,400 mA g-1,800 mA g-1,1000 mA g-1 for each 10 cycles, the capacity returned to 835 mAh g-1, showing a good rate capability.