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Electrochemical characterization of lithium containing thin films

: Dorai Swamy Reddy, Keerthi
: Zybell, Sabine; Neumann, Volker; Bartha, Johann Wolfgang; Albert, Matthias

Dresden, 2017, 102 S. + 2 S. Anhang
Dresden, TU, Master Thesis, 2017
Master Thesis
Fraunhofer IPMS ()

Rechargeable Li-ion batteries have gained applications in most of the electronic appliances due to its higher volumetric and gravimetric energy densities compared to other rechargeable batteries. Since integrated electronics follow the trend of miniaturisation, Li-ion batteries too follow the same trend to provide on-chip power supply. Miniaturization in Li-ion batteries has boosted due to employment of solid electrolyte. For integration of batteries into the Si-chip, compatible deposition techniques need to be used to deposit electrodes and electrolyte. Atomic layer deposition (ALD) has been proven the best method to deposit thin layers even in high aspect ratio structures with high step coverage. Thus, electrode and solid electrolyte materials can be deposited by ALD to achieve the aimed energy density. Each layer deposited needs to be tested for its electrochemical properties which is essential for the functioning of battery. Electrochemical methods such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are broadly used as characterization methods to test the material properties of Li-ion battery electrodes and electrolytes. In this study, Atomic layer deposition of Li2O is studied briefly as an initial step to know the technicalities of depositing lithium containing thin films. The main part of the report deals with characterization techniques for complete LIB cells. Firstly, commercial LIB of different capacity and composition were tested after set-up of the new measuring equipment. Finally, a 150 nm TiO2-ALD layer, implemented in a home-made LIB, was characterized in detail. Both techniques proved to be useful, and worked as complementary methods to gain a conclusive picture of decisive layer properties.