Modelling and simulation of the electro-thermal behavior of a Lithium-ions battery with concurrent electrical and mechanical load

One of the most important long-term objectives of the modern society is the achievement of a competitive low carbon economy. This mission is mainly based on enabling environmentally sustainable investments, particularly in terms of decreasing energy consumption in buildings, transition to electric vehicles, and developing smart electricity networks, while promoting renewable energy use in order to reduce greenhouse gas emissions by at least 80% by 2050 compared to 1990 levels [8]. Since, transport is one of the main sector responsible for CO2 emissions, diffusion of Electric Vehicles (EVs) could allow immense reduction. Considering the European Union territory, road vehicle transport constitutes 30% of total emissions [9]. These impressive data arouse the necessity of a turnaround in the approach to the concept of mobility. The current strong dependence on fossil fuels is one of the most important issues when talking about future mobility. Electricity as an energy vector for vehicle propulsion offers the possibility to substitute oil with a wide diversity of primary energy sources [10]. This could ensure security of energy supply and a broad use of renewable and carbon-free energy sources. The shifting to a complete electric mobility opened a wide research on energy storage systems. Lithium-ion batteries actually represent the most employed storage devices in EVs. These are able to provide one of the best energy-to-weight ratios, exhibit no memory effect, and experience low self-discharge when not in use. These beneficial properties, as well as decreasing costs, definitely define Li-ion batteries as the leading candidate for the next generation of automotive vehicles. [11]. Scientific research on Li-ion batteries focused on two main aspects in the last years: performance optimization and safety. Both areas of study require tools for the evaluation and analysis of the design parameters of a cell. For this reason, experimental investigations and tests are conducted on a wide range of regular working and abuse conditions, in order to better understand the aspects to be optimized and the risks associated to a certain load conditions. A trial-and-error determination of battery design parameters and operating conditions is inefficient, which has motivated the use of battery models to numerically optimize battery designs. [11] This work of thesis takes part to the “SafeBattery” research project, funded by VSI and seven industrial partners (Audi, AVL, Bosch, Daimler, Kreisler, Porsche, SFL), with the main objective of understanding which are the hazards of Li-ion batteries under various mechanical load conditions. In particular, the treated case of study regarded the evaluation of the electro-thermal effects of a non-disruptive deformation on a pouch cell, in other words the battery is subjected to a mechanical indentation through the application of an impactor, then different electrical loads are applied to evaluate the differences between the behavior of the pristine battery and the deformed one. This experimental investigation represents the basis of this work of thesis, in which a modelling strategy was defined in order to reproduce and simulate the testing condition with the target of the identification of local variation of internal parameters of the cell.