Design of an all solid state thin film lithium ion batteryand their electrochemical-thermodynamic modeling and evaluation

目前，LiCoO2被用作“小型”应用（笔记本电脑、娱乐行业）的正极材料。然而，在电动汽车电池中使用钴被认为过于昂贵。用Ni和Mn部分替代Co可以降低成本，提高电池性能和安全性。在这个项目中，我们将专注于层（插层）类型的正极材料，基于LiMO2体系（其中M是Co， Mn和Ni的任意组合）。我们将使用计算热力学（calphhad），使用复合能量形式中的复杂固溶体模型来模拟相图，相稳定范围和热力学性质作为电荷状态和氧分压的函数。将采用从头计算来关联准二元溶液的电子结构和相稳定性，并为热力学建模（0 K焓）以及与实验（（脱）插层时的体积变化，弹性，开路电压）进行比较提供数据。基于薄膜合成组合方法的薄膜沉积方法将被应用于有效地设计和制造各种化学成分、所需晶体结构和微观结构的薄膜。这些材料将被详细地描述，得到的结果将有助于为热力学模型生成一个实验数据库。这些材料还将用于制造用于电化学测量的完整电池单元。这些检查的结果将是关于细胞的功能、可重复性和稳定性的实用信息，这也将为改进迭代步骤中的理论描述提供输入。加速量热法将用于研究单个正极材料和组装电池的分解机制，以提高长期性能和安全性。该项目将大大提高对层状阴极材料的能量学和稳定性的认识，这将使未来阴极材料的设计成为可能。在第二个资助期，我们计划将重点转向微/纳米结构和动力学方面。

Currently LiCoO2 is used as cathode material for “small” applications (laptops, entertainment industry). However, use of Co is considered too expensive for batteries in electric vehicles. Partial substitution of Co by Ni and Mn can lower costs and improve battery performance and safety. In this project we will concentrate on cathode materials of the layer (intercalation) type, based on the system LiMO2 (where M is any combination of Co, Mn and Ni). We will use computational thermodynamics (Calphad) using complex solid solution models within the Compound Energy Formalism to model the phase diagrams, phase stability ranges and thermodynamic properties as function of charge state and oxygen partial pressure. Ab initio calculations will be employed to correlate the electronic structure and the phase stability of quasibinary solutions and to provide data for thermodynamic modelling (0 K enthalpies) as well as comparison with experiments (volume changes upon (de)intercalation, elasticity, open-circuit voltage). Thin film deposition methods based on combinatorial approaches to thin film synthesis will be applied to efficiently design and create thin films of a wide variety of chemical compositions, desired crystal structure and microstructure. These materials will be characterised in detail, and the results obtained will contribute to generate an experimental database for the thermodynamic modelling. These materials will also be used to build complete battery cells for electrochemical measurements. The outcome of these examinations will be practical information on functionality, reproducibility and stability of cells, which will also provide input to improve the theoretical description in iterative steps. Accelerated rate calorimetry will be used to study decomposition mechanisms of individual cathode materials and assembled cells to improve long term performance and safety. This project will lead to a much improved knowledge of energetics and stability of layered cathode materials which will enable the design of future cathode materials. In a second funding period we plan to shift the focus towards micro/nano-structural and kinetic aspects.