高性能Al-LiCoO2复合薄膜正极的可控制备及其原位包覆改性研究

It has been paid considerable attention to develop a high-performance of thin film cathode in the field of all-solid-state thin film lithium batteries. There are some problems of the current poor transport ability of lithium ion and electron in the thin film cathode, high interface impedance between the cathode and the electrolyte. This project intends to prepare the Al-LiCoO2 composite thin film cathode adopting co-sputtering strategy, build the transport channel of lithium-ion and electron to improve its transport ability, and optimize the electrode-electrolyte interface using reaction sputtering in-situ coating Al2O3 on its surface, which could enlarge the actual capacity and improve the cycle life and rate performance of the thin film lithium batteries. Firstly, the influence of the sputtering parameters on the structure, composition, growth rate and performance of single-phase LiCoO2 thin films and Al thin films and their interaction relationship will be studied to reach controllable preparation of Al-LiCoO2 composite thin film and in-situ coating by Al2O3. Secondly, the component and structure of composite film electrodes and its internal relation with the electrochemical properties will be explored. Then the percolation and interface effect on the composite films will be investigated. Besides, the transport mechanism of electronics and lithium-ion, co-sputtering modification mechanism of the composite cathode are going to be studied and the controllable preparation of high-performance Al-LiCoO2 thin films will be achieved. This project will provide a guidance for the preparation of thick film electrode as well as for electrode coating.

开发性能优良的薄膜正极是全固态薄膜锂电池领域的研究热点。针对目前薄膜正极中锂离子及电子输运能力差、电极与电解质界面阻抗大等问题，本项目提出采用多靶共溅射技术制备Al-LiCoO2复合薄膜，构筑锂离子及电子输运通道实现电极中锂离子及电子输运能力的同时提升，并利用反应溅射在其表面原位沉积Al2O3包覆层，实现电极表界面优化处理，从而提高薄膜锂电池的实际容量、循环性能及倍率性能。首先，研究溅射参数对单相LiCoO2薄膜及Al薄膜结构、成分、生长速率及性能的影响，掌握其相互作用规律，进而实现Al-LiCoO2复合薄膜的可控制备及其Al2O3原位包覆。其次，探索复合薄膜电极的成分及组织结构与其电化学性能的内在联系，考察复合薄膜中的渗流效应及界面效应，阐明薄膜中电子及锂离子的输运机制，揭示共溅射复合薄膜的改性机理，实现高性能Al-LiCoO2薄膜的可控制备，并为厚膜电极的制备及电极包覆改性提供借鉴。

项目背景：薄膜电极是影响全固态薄膜锂离子电池性能的关键因素。在众多已开发的正极材料中，LiCoO2具有易于制备成膜、开路电压较高、充放电过程体积变化小等优点被认为是较理想的薄膜正极之一。本项目针对LiCoO2薄膜正极中电子及锂离子输运能力差、电极与电解质界面不稳定等问题，采用多靶共溅射技术制备了Al-LiCoO2复合薄膜，并利用反应溅射在其表面原位沉积Al2O3包覆层，实现电极表界面优化处理。主要研究内容：首先，研究了溅射参数如溅射功率、工作气压、基片温度、靶基距等对LiCoO2薄膜和Al薄膜的影响，得到相关作用规律。其次，采用共溅射技术制备了Al-LiCoO2复合薄膜，考察了复合薄膜电极中的渗流效应，研究了Al含量对薄膜电子及锂离子导电性的影响规律。进一步在Al-LiCoO2复合薄膜表面原位溅射沉积了Al2O3包覆层，研究了包覆层对电极表界面的影响。分别组装了液态电池及固态电池，结合电化学性能测试及结构、成分等表征，讨论了其复合、包覆的改性机理。重要结果及关键数据：磁控溅射参数对LiCoO2薄膜性能影响明显，共溅射制备Al-LiCoO2复合薄膜能有效提高薄膜的锂离子及电子导电性，改善其循环性能及倍率性能，结合Al2O3包覆能进一步提高LiCoO2薄膜的循环稳定性。科学意义：提出并验证了共溅射制备Al-LiCoO2复合薄膜及原位包覆对LiCoO2薄膜性能的改善作用，为薄膜电极的制备及改性研究提供借鉴。