Electrochemical impedance spectroscopy is known to be one of the most accurate analytical techniques for the study of lithium-ion batteries. However, correct analysis of impedance data presents a rather difficult task due to the common overlap of several impedance features. Improved deconvolution can be achieved by variating certain battery parameters, such as electrolyte concentration. In the following thesis, the effects of varying LiPF6 salt concentration on the impedance response of the state-of-the-art lithium ion cathode material NMC 811 are examined.
The increase in size of certain impedance features with decreasing salt concentrations enabled full decoupling of the impedance response, which provided access to all relevant battery parameters. These parameters then enabled the evaluation of a proposed TLM, which for the studied cells accurately described all relevant impedance features.
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