### 石墨烯-Li2MnSiO4复合正极材料的合成与电化学性能研究

1. a 北京理工大学化工与环境学院 环境科学工程北京市重点实验室 北京 100081;
b 中国电力科学研究院 北京 100192;
c 国家高技术绿色材料发展中心 北京 100081
• 投稿日期:2013-12-31 发布日期:2014-04-16
• 通讯作者: 苏岳锋 E-mail:suyuefeng@bit.edu.cn
• 基金资助:

项目受国家重点基础研究发展规划项目（973）（No. 2009CB220100）、国家自然科学基金青年科学基金项目（No. 51102018，21103011）、国家高技术研究发展计划（863）项目（No. 2011AA11A235，SQ2010AA1123116001）和国家电网公司科技项目（DG71-13-007）资助.

### Synthesis and Electrochemical Performance of Graphene-Li2MnSiO4 Composite

Dai Liqina, Wu Fenga,c, Guan Yibiaob, Fu Kaib, Jin Yib, Gao Weia, Wang Zhaoa, Su Yuefenga,c

1. a School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing Key Laboratory of Environmental Science and Engineering, Beijing 100081;
b China Electric Power Research Institute, Beijing 100192;
c National Development Center of High Technology Green Materials, Beijing 100081
• Received:2013-12-31 Published:2014-04-16
• Supported by:

Project supported by the National Key Basic Research Program of China (973) (2009CB220100), National Natural Science Foundation of China (51102018, 21103011), National High-Tech Research and Development Program of China (863) (2011AA11A235, SQ2010AA1123116001) and Science Program of the State Grid Corporation of China (DG71-13-007).

Graphene-Li2MnSiO4 composite cathodes for lithium ion batteries were successfully synthesized by hydrothermal assisted sol-gel method. XRD (X-ray diffraction), SEM (scanning electron microscope) and EIS (electrochemical impedance spectroscopy) were used to characterize the component, structure and morphology of the obtained composite materials. Electrochemical performance of the as-prepared materials was tested when composited with different amount of graphene oxide (2%, 4%, 6%, 8%, 10% and without graphene oxide). The experiment results indicated that composite materials belong to the orthorhombic Pmn21 space group and the addition of graphene oxide did not change the structure of the materials. Graphene and Li2MnSiO4 material were homogeneously composited with each other and it could be clearly observed the relatively transparent and thin layer graphene in the edges of the materials. The micro-scale particle of all the samples was agglomeration of nano-crystallites. When composited with appropriate amount of the graphene oxide, the particles became loose and some micropore structure was formed. The conductive network graphene could greatly promote the liquid electrolyte to pass through particles, facilitate the electron transport and restrain particles agglomeration. The sample with 6% graphene oxide yielded the best electrochemical performance in all the samples (the carbon content is 8.25%). Without calculating the carbon mass, this material delivered an initial discharging capacity of 166 mAh/g, and retained 101 mAh/g after 20 cycles at 1.5～4.8 V with a current density of 10 mA/g. Besides, compared with the pristine, the graphene-Li2MnSiO4 composite materials delivered an excellent rate performance. The improvement of specific capacity and rate performance was due to that the interconnected network structure of graphene oxide acted a key role in stabilizing the structure of composite materials and inhibiting structural damage in the charge-discharge process. Moreover, the surface charge transfer resistance of the Li2MnSiO4 was significantly decreased when composited with graphene oxide. It means that the enhancement of electronic conduction ability is one of the main reasons that contribute to improvement of the electrochemical performance of composite materials. Thus, the graphene is considered to be of significance in improving material electronic conductivity and enhancing the reversible lithium intercalation/deintercalation capacity of Li2MnSiO4 cathode materials.