具有核壳结构的镍锰钴基三元复合正极材料的研究

Li[NixMnxCo1-2x]O2 material has become one of the promising cathode material systems for their high capacity, good thermal stability, environmental-friendly in the lithium ion batteries. However, the electrochemical performance of the Li[NixMnxCo1-2x]O2 material as a cathode for electric vehicle technology need to be improved, especially charged to higher voltage or discharged at higher rates. In this project, the material is double-modified using metal fluorides and nano-carbon to improve the Li[NixMnxCo1-2x]O2 electrochemical performance and thermal stability. The metal fluorides coating can prevent the direct contact of electrode from electrolyte, and thus suppress the undesirable interaction between them and the dissolution of transition metal ions attacked by HF acid, and accordingly the higher rate performances are enhanced further. Nano-carbon coating can enhance electron conductivity to improve the high rate capability and cycling stability of Lithium ion batteries. Nano-carbon also can reduce cell polarization. The study shows the law and mechanism how the metal fluorides and nano-carbon layers influence the lithium ion transport and electronic conductivity, how the undesirable interactions are restrained. These all can provide new ideas and theoretical guidance for the development and application of the cathode materials for lithium ion batteries.

三元正极材料Li[NixMnxCo1-2x]O2因具有高容量、热稳定性好和对环境友好等优势成为锂离子电池研究的热点之一。但Li[NixMnxCo1-2x]O2 作为电动汽车用锂离子动力电池正极材料，其电化学性能尚待改善，尤其是高截止电压和高倍率下的充放电性能有待进一步提高。本项目采用金属氟化物和纳米碳对其进行双重修饰改性，以提高电化学性能和热稳定性能。采用金属氟化物表面修饰提高Li[NixMnxCo1-2x]O2材料在充放电过程中的结构稳定性，阻止电极材料与电解液的直接接触，抑制循环过程中HF对电极材料的腐蚀，减少电解液与电极材料的副反应，从而提高材料的循环性能；利用纳米碳包覆能提高材料的电子导电性进而提高其倍率性能，而且纳米碳包覆还能减少电池极化。通过本项目的研究，揭示金属氟化物和纳米碳双重修饰对锂离子传输特性以及电导率的影响规律，从而为锂离子动力电池正极材料的研发提供新思路和科学依据。

三元正极材料LiNixMnyCo1-x-yO2因具有高容量，热稳定性好，对环境友好等优势成为锂离子电池研究的热点之一。但是LiNixMnyCo1-x-yO2作为电动汽车用锂离子动力电池正极材料，还需要改善其循环性能，尤其是高充电截止电压和高倍率下的充放电性能有待进一步提高。本项目采用金属氟化物和碳对其进行修饰改性提高电化学性能和热稳定性能。采用金属氟化物表面修饰提高LiNixMnyCo1-x-yO2材料在充放电过程中的结构稳定性，阻止电极材料与电解液的直接接触，抑制循环过程中HF 对电极材料的腐蚀，减少了电解液与电极材料的副反应，从而进一步提高材料的循环性能；利用碳包覆提高材料的电子导电性进而提高其倍率性能。通过本项目的研究，揭示金属氟化物和碳修饰对锂离子传输特性以及电导率的影响规律，从而为锂离子动力电池正极材料的研发提供新思路和科学依据。