【作者】 李玲玲；

【导师】 徐刚；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2016， 硕士

【摘要】 橄榄石结构LiMPO4是最有希望实现大功率应用的锂离子电池正极材料,本论文在综述LiMPO4正极材料研究现状的基础上,在溶剂热系统中引入P123和氧化石墨烯GO,辅助溶剂热制备了充分覆碳,电化学性能优良的LiFePO4、 LiMnPO4锂离子电池正极材料,取得了以下主要成果：(1)利用P123辅助水／乙二醇溶剂热法,成功地制备出了纳米晶无间隙聚集而成的LiFePO4纳米颗粒。吸附的P123使得所合成的LiFePO4纳米颗粒表面及聚集的纳米晶界充分覆碳,表现出优异的充放电性能和倍率性能,0.1 C的首次充、放电比容量分别为162.95 mAh/g,153.12 mAh/g,高倍率10C的放电容量达到127.60 mAh/g,是0.1C充放电容量的78%。(2)利用GO辅助乙二醇溶剂热法,成功地制备出了纳米片自组装的花状LiMnPO4/GO复合纳米结构。由于GO在纳米片表面的吸附,自组装单元呈翘曲状,彼此之间保持有较大的间隙。吸附于自组装基元纳米片表面的GO碳化后,获得了纳米片表面充分碳包覆的花状LiMnPO4/C复合正极材料,表现出优异的电化学性能,0.05C的首次放电容量达到101.8mAh/g,远优于没有引入GO合成的LiMnPO4花状纳米结构的首次充放电容量69.16 mAh/g。(3)在乙二醇溶剂热系统中引入KOH矿化剂,有效促进了LiMnPO4的形核,使得所合成的LiMnPO4晶粒减小。在较高的KOH浓度下,所合成的纳米晶自组装形成LiMnPO4椭球状类单晶纳米颗粒,由于缩短了Li离子脱嵌的路径,表现出了较好的电化学性能,0.1C下首次充、放电比容量分别为58.53mAh/g, 55.09 mAh/g。更多还原

【Abstract】 Olivine structure LiMPO4 is the most promising cathode materials for Li-ion battery to achieve high power application. In this paper, after reviewing the current research status of LiMP04 cathode materials, LiFePO4 and LiMnP04 cathode materials are synthesized via P123-assisted and graphene oxide-assisted solvothermal route, respectively. Due to the improvement for fully covering carbon coatings, the obtained LiFePO4 and LiMnP04 cathode materials express excellent electrochemical performances. The main researching results and conclusions are listed as follow:(1) The LiFePO4 nanoparticles which is gathered together gaplessly with nanocrystallites have been successfully prepared by solvothermal method assisted with triblocks copolymer P123. Adsorption of P123 makes the surface of the synthesized LiFePO4 nanoparticles and the boundaries of aggregated nanograins are fully covered with carbon film, showing excellent charge-discharge performance and rate performance. The first charge and discharge specific capacity at 0.1 C are 162.95 mAh/g,153.12 mAh/g, respectively. The discharge capacity at high rate of 10C achieves 127.60 mAh/g, which is 78% of the discharge capacity of 0.1 C.(2) Flower-like LiMnPO4/GO composite nanostructures self-assembled by nanosheets have been successfully prepared by solvothermal method assisted with GO. Due to the adsorption of GO, the primary block nanosheets become much bow and twist, making there exist some gap among the nanosheets. After carbonization of the GO adsorpted on the surface of primary block nanosheets, flower-like LiMnPO4/C composite nanostructures, in which the primary block nanosheets are fully covered with carbon coating, are obtained and deliver excellent electrochemical performance. The first discharge capacity at 0.05 C reached 101.8mAh/g, which was much better than the first discharge capacity of the flower-like LiMnPO4 nanostructures, which are solvothermally synthesized without any GO, about 69.16 mAh/g.(3) The introduction of KOH mineralizer into the ethylene glycol solvothermal system can effectively promote the nucleation of LiMnPO4, making the formed LiMnPO4 grains decreased. Therefore, under the effect of the high concentrations of KOH, the formed nanograins self assemble to single-crystal-like LiMnPO4 ellipsoidal nanoparticles, which show better electrochemical performance due to the shortening of Li-ion diffustion path, the first charge and discharge capacities at 0.1C achieve 58.53mAh/g,55.09 mAh/g, respectively.更多还原