锂离子电池电极材料表面石墨烯包覆网络的原位可控生长及对电化学性能影响规律的研究

项目名称： 锂离子电池电极材料表面石墨烯包覆网络的原位可控生长及对电化学性能影响规律的研究

项目编号： No.21473119

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 分析化学

项目作者： 张力

作者单位： 苏州大学

项目金额： 82万元

中文摘要： 碳包覆技术是锂离子电池电极材料电化学性能发挥的关键支撑技术之一。电极材料要求碳包覆层需同时具备完整连续、高度石墨化及超薄的特点，因此石墨烯薄层被认为是最理想的包覆方式。然而在电极材料表面原位生长石墨烯包覆薄层具有极大的难度，只有通过发展有效的低温催化石墨化途径来实现。本项目借鉴目前石墨烯主流制备技术的生长机制并加以合理微缩化，提出溶解-析出法以及二元合金催化剂法两种生长策略。通过严格控制固态碳源和催化剂前驱体的种类、含量和比例，借助原位形成的金属催化剂纳米岛薄层在电极材料表面催化生长由紧密石墨烯包覆薄层以及向空间延伸的石墨烯片构成的特殊网络结构，同时实现对石墨烯层数、结晶度和掺杂度的精确调控。借助电化学测试和光谱、显微手段，我们将详细探讨电极材料电化学性能与石墨烯包覆网络结构及组成间的关联规律，优化石墨烯的最佳层数、结晶度和掺杂度，并对石墨烯包覆网络的生长机理进行深入研究。

中文关键词： 石墨烯包覆网络；原位生长；结构调控；电化学性能；锂离子电池

英文摘要： Carbon coating is one of the key techniques to improve the electrochemical performance and material utilization of the lithium-ion battery materials. Typically,an uniform, ultra-thin and highly-graphitic carbon coating layer throughout the electrode surface is ideal for low conductive materials to achieve better performance. Graphenen thin-layer coating is therefore regarded as the most promising coating manner. However,in-situ growth of graphene coating layer on the electrode surface is very challenging given the optimum synthesizing temperatures of most electrode materials are not high enough for carbon to graphitize effectively. Therefore, it is necessary to develop an effective low-temperature catalytic graphitizaiton approach to in-situ grow graphene decorations. Inspired by the growth mechanism of typical techniques reported for graphene mass-production, we propose two novel bottom-up synthesis strategies based on dissolution-precipitation mechanism and binary metal alloy catalysts, respectively. By precisely controlling the content and ratio of solid carbon sources and catalyst precursors, a thin layer of nano-islands composed of metal catalysts can be in-situ formed. Under the catalysis of such catalyst thin-film, a special graphene network can be in-situ grown on the electrode surface through the realignment of the carbon atoms arousing from the pyrolysis of carbon sources. The graphene sheets not only form a compact and uniform coating layer along the electrode surface,but also stretch out and cross-link into a conducting network around the electrodes.Meanwhile,the thickness, graphitization degree and doping degree of the graphene coatings can also be precisely tuned by the optimization of carbon sources and catalyst precursors. In addition, the effects of graphene coating quality on the electrochemical properties of electrodes will be further investigated and discussed detailedly through electrochemical measurements to optimize the parameters of the graphene coatings.What's more, the growth mechanism of the graphene coatings will also be detailedly studied using the spectrographic techniques and microscopic methods.

英文关键词： graphene coatings;in-situ growth;architecture control;electrochemical performance;lithium-ion batteries