Preparation And Performance Of Graphene Based Anode Materials For Lithium-ion Battery

Lithium-ion batteries, which is what we usually refer to the storage battery,because of its advantages: high output voltage, high energy density,highsafety,good cycle performance, low self-discharge rate, fast charge and discharge,high charge-discharge efficiency etc, these make lithium-ion batteries become thenew leader in the next generation new energy,also make many electronic productsmore and more portable and miniaturizational. Therefore, the development oflithium-ion battery which has low cost, high security, high physical and chemicalproperties is imminent. Lithium-ion battery is normally assembled by the twodifferent electrode materials,electrolyte,separator,and cell shell etc,while anodematerial is one of the important components, which has a crucial impact on theelectrochemical performance of lithium-ion battery, so the exaltation of anodematerial’s lithium storage could be the important standerd to evaluate the performance of of lithium-ion batteries.Graphene is a rising star of carbon anode materials,which has a two-dimensional network structure of a single carbon atom.It has a high intrinsiccarrier mobility (200000cm2V-1s-1),excellent thermal conductivity (5000W m-1K-1), high optical transmittance (~97.7%),high theoretical specific surface area2630m2g-1), and superior mechanical strength. These unique physical and chemicalproperties of graphene makes it a possible alternative to the traditional graphiteanode material, but the energy density of the pure graphene still can not meet itsoriginal expectations, which makes application of graphene greatly restricted.In a variety of negative materials, silicon, which has high theoretical specificcapacity of4200mAh/g, lower operating voltage, rich natural reserves, lowercosts, has become the most promising anode material. However, nanosiliconparticles could pulverize during the process of lithiation/delithiation because ofthe dramatic volume expansion and contraction, resulting in the destroy of thecell’s structure,finally resulting in the poorcell cycle performance and the shortercell life.This paper primarily studyed graphene oxide,reduced graphene oxideaerogel, reduced graphene oxide/nano-silicon particles aerogel and reducedgraphene oxide/modified nano-silicon particles aerogel through redox and bathself-assembly methods, then characterize them and test the electrochemicalperformance,the specific study as follows:1、Thin layer even monolayer of high purity graphene oxide(GO) aqueous dispersion has been successful synthesized by a modified Hummers method,andreduce GO to reduced graphene oxide aergel which hasa three-dimensionalporous structure using reductant L-Ascorbic acid by bath self-assembly.Then themorphology and structure of GO and rGO areogel was characterized through SEM、TEM、AFM、Raman、XPS、FTIR etc, and the batteries was assembled to testthe electrochemical performance. The results showed that the three-dimensionalporous reduced graphene oxide has a good electrochemical performance.2. Mixing nano-silicon particles and modified nano-silicon particlesrespectively with graphene oxide prepared through mechanically ultrasonicing,then reduced them to reduced graphene oxide/nano-silicon particles aerogel andreduced graphene oxide/modified nano-silicon particles aerogel using reductantL-Ascorbic acid by bath self-assembly. Then the structure and morphology of thecomposite materials was characterized and the electrochemical performance wastested.The results show that the modified nano-silicon particles/rGO aerogelcomposite has a superior cycle, while the dispersibility of modidiede siliconnanoparticles was improved and lowered the restack of reduced graphene oxideaerogel sheets.