Preparation And Characterization Of Carbon - Supported Tin - Cobalt Alloy Lithium Anode Materials

Compared to traditional second batteries, Lithium ion batteries (LIB) have higher energy density, higher voltage, better cycle performance, no memory effect, longer cycle life, so that have attracted special attention of scholars at home and abroad in this field. Influence factors of lithium ion battery are composed of the positive electrode, the negative electrode and electrolyte etc. Among them, anode materials is the main factor which determines the comprehensive performance of the LIB. As for the anode materials, carbon material is the first to research and apply to the lithium ion battery production. But carbon anode materials have following disadvantages:low actual specific capacitance, low first coulomb’s efficiency, poor rate performance and bad discharge performance etc, and it cannot meet the actual demand. Therefore, the study of lithium-ion batteries with high-performance should become the research focus. The anode material prepared by carbon loading a metal ally is very promising and has good cycle performance, as the metal alloy has a high specific capacity and good conductivity, while the volume expansion of the metal alloy during the charging and discharging can be buffered by the carbon-based material. In this paper, we have analyzed and summarized the newest development about anode materials of lithium ion batteries and prepared graphene/CoSn2and grid shell/CoSn carbon microspheres two electrode materials, we prepared and assembled lithium-ion button battery and analyzed a series of its performance. The microstructure and morphologies of these materials are observed by SEM, TEM, XRD and BET. The electrochemical performances are evaluated by galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectra in detail. The main results are as follows.1. The sandwich structure GNS/CoSn2composite material was prepared by the low-temperature liquid phase reduction method. The composite material was obtained by using graphene obtained by improving Hummers method and load CoSn2alloy, and then reduce on high-temperrature under6%hydrogen nitrogen atmosphere. We investigated the influence of different proportions of tin and cobalt and different carbonization temperature on GNS/CoSn2composite material properties.In the preparation of composite materials experiments, the molar ratio of SnCl2·2H2O and CoCl2·6H2O are1:1,2:1,3:1,4:1. The best electrochemical properties of these sample is the sample obtained when the optimal is3:1. Investigating the reduction temperature of the composite materials at20℃,300℃,400℃,500℃,600℃,the electrochemical performance of it shows that the best electrochemical properties samples can get at400℃.The XRD analysis showed that the composite is composed of CoSn2and Co3Sn2two alloy crystal phases, and the nanoparticles of CoSn2and Co3Sn2are uniformly dispersed on graphene that could be observed from the TEM. The initial reversible capacity of CoSn2/GNS electrode is837.2mAhg-1and it still remains796.6mAhg-1after100cycles, which is95.2%of the first charge capacity.2. CoSn/CS, CoSn/GSCS, CoSn/HCS three different morphologies materials are obtained by using F108as surfactant,2,4-dihydroxybenzoic acid, formaldehyde and CoSn as reactants, L-lysine as catalyst. The SEM and TEM analysis found that the diameter of the microspheres is about600nm, the wall thickness is50nm, and the particle of CoSn is13nm. And the CoSn particles dispersed into the microspheres is becoming denser with increasing CoSn. The electrochemical performance of CoSn/GSCS composite electrode is much better than CoSn/CS and CoSn/HCS. When the current density is100mAg-1, the CoSn/GSCS anode material has the optimal electrochemical performance and the initial reversible capacity is870.6mAhg-1, the reversible capacity is734.2mAhg-1in200cycles, and it still maintains734.2mAhg-1which is84.4%of the initial reversible capacity after100cycles. When the current density is1000mAg-1, the CoSn/GSCS anode material has the optimal electrochemical performance and the initial reversible capacity is419.7mAhg-1, the reversible capacity is353.6mAhg-1in the800cycles, and it still maintains340mAhg-1which is81%of the initial reversible capacity after800cycles.