Development and validation of an electrochemical-thermal model for HIGH ENERGY CELLS and experimental validation.

We are in a historical period for humanity in which the energy transition plays a fundamental role in future perspective. The aim is to decrease climate change and air pollution by reducing our dependence on fossil fuels. As well known, the main solution is the integration of renewable sources in the countries energy mix but is also known the weak point of RES that is the intermittence in energy supplying due to natural conditions. For these reasons, the storage of energy comes to help with playing a very big role in power systems. In order to integrate more RES in the countries’ energy mix maintaining stability and reliability of energy supply, the EES (electrical energy storage) is crucial indeed. Many kinds of storage technologies, going from mechanical to electrical, chemical, electrochemical and thermal are established but among these, lithium-ion batteries nowadays are the most promising in terms of high efficiency, power densities, and other favorable characteristics making them most useful for power system applications. In particular, their present and future applications regard grid distribution and above all the automotive field in which, coupled with electric or hybrid engines, play an important role in the propulsion of the vehicle. Being the engine technology very developed and advanced today, the improvement of lithium-ion batteries represents the key in the development of the vehicle itself, especially with price-performance ratio, safety and lifetime, the main cell characteristic which must be optimized and enhanced in order to reach a level able to satisfy the demand of power and energy. This work forms the first task of FCA project in which Politecnico di Torino is involved: it is called Thermodel and its first part focuses its attention on the development of an electrochemical-thermal model; this model accurately predicts the behavior of the battery for both charging and discharging conditions for a wide range of current rates and therefore aims to project and build a battery pack voted to hybrid or full-electric drive. The battery model is based on a pseudo-2D (P2D) physics of a nickel-manganese-cobalt (NMC-cathode) lithium-ion battery able to estimate charging and discharging conditions for a wide range of current rates and so leading to predict electrochemical and not least thermal behavior. The latter in fact, affect lifetime and aging characteristics of the battery, being one of the most important actors in the role of degradation; so the work also looks into the heat generation in the cell to understand the reversible heat, highlighting also the important role of the graphite anode electrode. Given that, the purpose of the project is the integration in a hybrid/electric vehicle, but lithium-ion batteries are also very flexible for a huge number of applications considering their cost depends on the local electric market condition.