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

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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.