离子导体修饰的核壳结构LiRxNi0.5-xMn1.5O4-yFy高电位动力电池正极材料的研究

As the most promising cathode material for power lithium ion batteries,the main issues of LiNi0.5Mn1.5O4 are the formation of a Ni1-xLixO impurity phase and chemical instability in contact with the electrolyte at the high operating voltage. The project aims to providing a new technology to prepare 5V class cathode materials for power lithium ion batteries with high energy density, good rate capability and excellent cyclability. A controlled precipitation-controlled heat-treatment method has been firstly proposed to prepare pure spherical LiNi0.5Mn1.5O4 powders with high tap density.Then the LiNi0.5Mn1.5O4 powders are co-doped with substitution of rare earth R(Ce or Y) for Ni and F for O to form LiRxNi0.5-x Mn1.5O4-yFy.The basic reasons of the stability of the crystal structure and the improvement of electrical conductivity will be investigated by theoretical calculation,defect chemistry theory combination with ESR and PAT to study the differerence of electronic structure and defect structure between the doped material and the undoped one. At last, the LiRxNi0.5-x Mn1.5O4-yFy powders are coated with a uniform layer of ionic conductor to obtain a core-shell composite material. The related mechanism of the thickness of the shell and the ionic conductivity with the chemical stability and rate capability of the composites will be investigated in detail. The achievement of the goal will offer a new way for the application of LiNi0.5Mn1.5O4 in power lithium ion batteries.

作为最有前途的高电压动力电池正极材料，LiNi0.5Mn1.5O4的应用瓶颈在于合成纯相困难和容易与电解质溶液反应。在前期研究基础上，我们提出采用控制沉淀-控制热处理法制备单相高密度球形LiNi0.5Mn1.5O4粉末。采用稀土R（Ce或Y）和F对其实施复合掺杂；采用理论计算、运用缺陷化学理论、配合电子自旋共振和正电子湮没技术研究材料的电子结构、缺陷结构的变化，以弄清掺杂对晶体结构稳定和电子电导率提高的根本原因。在LiRxNi0.5-x Mn1.5O4-yFy表面包覆一层均匀的锂离子导体形成核-壳结构的复合材料，以提供锂离子在电极颗粒之间的扩散通道，并有效阻止电极颗粒与电解质溶液间的反应；研究壳层厚度、离子导电率对材料化学稳定性和倍率性能的影响机制。最终获得能量密度高、倍率性能好、循环稳性优秀的高电压LiNi0.5Mn1.5O4材料制备新技术，为其在动力电池中的应用提供新思路。

作为最有前途的高电压动力电池正极材料，LiNi0.5Mn1.5O4的应用瓶颈在于合成纯相困难和容易与电解质溶液反应。在前期研究基础上，我们提出采用控制沉淀-控制热处理法制备了单相高密度球形LiNi0.5Mn1.5O4粉末。采用稀土R（Ce或Y）和F对其实施复合掺杂；采用理论计算、运用缺陷化学理论、配合电子自旋共振和正电子湮没技术研究了材料的电子结构、缺陷结构的变化，初步探讨了掺杂对晶体结构稳定和电子电导率提高的根本原因。在LiRxNi0.5-x Mn1.5O4-yFy表面了包覆一层均匀的锂离子导体形成核-壳结构的复合材料，以提供锂离子在电极颗粒之间的扩散通道，并有效地阻止电极颗粒与电解质溶液间的反应；研究了壳层厚度、离子导电率对材料化学稳定性和倍率性能的影响机制。最终获得了能量密度高、倍率性能好、循环稳性优秀的高电压LiNi0.5Mn1.5O4材料制备新技术，可为其在动力电池中的应用提供新的思路。在本项目的资助下，项目组取得了如下的研究成果：（1）在 《Journal of Power Sources》、《Advanced Powder Technology》、《Ceramics International》、《Ionics》、《Applied Surface Science》、《Polymers & Polymer Composites》、《Polymer-Plastics Technology and Engineering》、《Journal of Macromolecular Science, Part B: Physics》、《Journal of Macromolecular Science, Part A: Pure and Applied Chemistry》、《Vacuum》、《中国有色金属学报》、《环境工程学报》、《精细化工》等刊物上发表了33篇，其中会议论文14篇，被SCI收录15篇、EI收录17篇。（2）申请国家发明专利5项；（3）培养硕士研究生6名。