## 1 Introduction  
Recently, interest in electric vehicles has been increasing because of their advantages, such as reduced pollution and noise, compared to vehicles having an internal combustion engine. According to the International Energy Agency [1], 6.6 million electric cars were sold in 2021, which corresponds to 9% of the global car market. Batteries, electric motors and regenerative braking systems can be stated as the main components of all-electric vehicles [2]. Batteries can be considered one of the most important since they are directly related to their cost and range. Among the different battery options, Lithium-ion (Li-ion) ones are used in electric vehicles since they have specifications such as higher energy density, lighter weight, higher cycle life and lower self-discharge rates [3]. The high-power density demand of Li-ion batteries results in higher heat generation due to reaction heat, electrode over-potential heat and Joule heat of internal electrical resistance during both charging and discharging processes [4]. Since the generated heat adversely affects battery performance, it is necessary to remove it from the battery surface. In the literature, the optimum working temperature of Li-ion batteries is suggested in the range of 20 \({}^{\circ}\)C to 40 \({}^{\circ}\)C, where the temperature difference on the battery surface should be a maximum of 5 \({}^{\circ}\)C [5, 6]. If the operating temperature of a battery exceeds these ranges, it is possible to encounter some problems related to safety, thermal runaway and capacity losses [7, 8, 9, 10]. The heat generation of Li-ion batteries is generally measured by means of the calorimeter or determined with electrothermal models. In some studies on this subject [11, 12, 13, 14, 15, 16, 17],reversible/irreversible heat sources, internal resistance and entropy coefficient of battery are evaluated, and new calorimeters have been designed to determine heat generation rate for various operating conditions. In order to remove generated heat from the battery, battery thermal management methods are used, and they are classified as air cooling, liquid cooling, phase change material cooling and a combination of them [18]. Among them, air and liquid (water and ethylene glycol) are generally used for cooling batteries. Air cooling systems have advantages such as low cost, easy maintenance, low weight, simple design and no leakage problem, but they have disadvantages such as low thermal performance, higher fan power consumption and noise [19]. The cooling systems working with liquids have advantages such as high thermal performance, high specific heat capacity of the fluid and homogenous temperature distribution. The liquid cooling system can be designed as direct or indirect according to whether or not there is direct contact between the battery and the cooling fluid. In direct cooling, a dielectric liquid having higher thermal conductivity and lower viscosity contacts the battery and higher heat transfer is obtained compared to indirect cooling. Although indirect liquid cooling is preferred to avoid an electrical short circuit and chemical erosion in application [20], one of the direct contact cooling methods, called immersion cooling, can be used for the battery thermal management of electric vehicles. In this method, batteries are immersed in dielectric and non-flammable fluids such as mineral oils, hydrofluorethers, esters and water/glycol mixtures, and the heat transfer mechanism can be one- or two-phase flow depending on the fluid's physical properties. The use of this method significantly enhances heat transfer between fluid and battery and leads to a lower surface temperature and a lower temperature difference compared to indirect liquid and air cooling techniques. Moreover, the risk of thermal runaway can be reduced with the application of immersion cooling [21]. Although immersion cooling was discovered a long time ago [22], it has recently been used in data servers [23; 24; 25; 26] and electronic equipment [27; 28; 29; 30].