Thermal Performance Enhancement of Lithium-Ion Batteries Using Phase Change Material and Fin Geometry Modification

Concerns about the environment and the need for zero-emission transportation have pushed for the development of electric vehicles (EVs) [1]. In comparison to other popular rechargeable batteries, such as nickel–cadmium, ni–metal hydride, and lead-acid batteries, lithium-ion batteries have high energy and power densities and long service lives and they are environmentally friendly. Thus, they have been widely used in consumer electronics [2]. Because of their durability, extended cycle lives [3], low self-discharge rates, and large capacities [4], lithium-ion batteries are primarily used as power sources for electric vehicles. The primary difficulties for batteries are heat and severe temperatures, which can occur at high discharge rates during scenarios such as rapid acceleration [5]. To maintain an equal temperature distribution among the cells, an effective BTMS is necessary [6]. To address all of these requirements, research studies have been conducted on BTMSs using several media for heat transfer, such as air, liquid, and PCM-based cooling [7,8,9,10,11]. Lin et al. [12] investigated a temperature range of −10 $°$C to 50 $°$C, which has been identified as the optimum temperature range for a lithium-ion battery. However, their observations showed that lithium-ion batteries perform optimally between 20–40 $°$C [13]. Motloch et al. [14] investigated operating temperatures within the 30–40 $°$C range and found that every 1 $°$C rise in temperature reduces the lifetime of a battery by approximately 2 months. Optimal li-ion battery operation can be achieved by maintaining battery temperatures that are within safe limits. There are several ways to control these temperatures, including liquid cooling [15], air cooling [16], and passive cooling using phase change materials. Al-Hallaj et al. [17] were the first to propose a BTMS based on phase change materials. Sabbah et al. [15] investigated cooling li-ion cells by air, as well as PCM-based cooling. Their results showed that high ambient temperatures combined with high discharge rates fail to maintain battery temperatures within safe limits. Chen et al. [18] numerically analyzed battery TMSs using air cooling and PCM-based cooling methods. Their simulations were conducted at various ambient temperatures, intake velocities for air cooling, and PCM phase change temperatures by applying the actual current profiles to the battery models. Their results showed that the air-cooling method is cheaper than PCM cooling, but over a longer life cycle, the air-cooling method shows nonuniformity. Wang et al. [19] experimentally investigated the effects of fins on battery TMS performance by using low-melting temperature (44 $°$C) paraffin wax and found that battery temperatures reduce by 8 $°$C, on average. Sun et al. [20] introduced a BMTS incorporating a CPCM and fins, featuring longitudinal cylindrical and longitudinal fins. Initial experiments were conducted to assess the performance of various BTMS configurations. It was deduced that the fin–PCM composite system has the best performance compared to the other cases at high heat generation rates of 20 W. Zhao et al. [21] enhanced a battery thermal management system (BTMS) using phase change material (PCM) and copper foam to address low thermal conductivity. They identified that active cooling using a cooling fluid through distributed tubes in the composite PCM (CPCM) results in 14 °C lower cell temperatures, indicating improved thermal management in the BTMS. Weng et al. [22] investigated the effects of surrounding temperatures on BTMSs. By conducting experimentations, it was found that steady-state current operations result in higher temperatures, resulting in the failure of the PCM-cooled BTMS and batteries. After 1500 s the at a surrounding temperature of 45 $°$C, the battery temperatures were 54.0 $°$C. This led to the development of a secondary cooling system using heat pipes. Safdari et al. [23] analyzed a BTMS using a coupled system with active cooling channels and PCM-based passive cooling for 18650 li-ion batteries. Their results showed that at low discharge rates, PCM-based cooling is effective in controlling temperatures; however, at high discharge rates, for the effective cooling of battery packs, the active air channels around the containers play a major role when passive cooling fails. Shojaeefard et al. [24] conducted a study to investigate BTMSs using six different fin types combined with PCM cooling. Their results indicated that horizontal fins have optimal cell temperature control compared to the other fin arrangements and types. Their results also indicated that BTMS temperatures are affected by changing fin alignment. Youssef et al. [25] conducted a unique design optimization to study the thermal performance of large li-ion batteries under high discharge rates and cyclic loading. Their results showed that out of all cooling methods, PCM combined with jute produced the lowest temperature of 35.09 $°$C; However, at very high discharge rates, the PCM combined with jute cooling system produced the highest temperature of 36.29 $°$C. This study did not account for the life cycle assessment of PCM–jute degradation. Huang et al. [26] numerically and experimentally studied BTMSs using PCM for 18650 li-ion batteries connected in parallel. The BTMS was analyzed based on a heating rate model developed from the internal resistance of the cells. Their results showed that battery temperatures reduce when the thermal conductivity of the PCM changes. However, at very high thermal conductivities of between 5–15 W/m-K, the temperature change is not significant. The lowest cell temperature achieved in this study was 44.5 $°$C. El Idi et al. [27] studied a battery thermal management system (BTMS) using li-ion cells and metal foam. They conducted numerical and experimental analyses to understand the heat absorption capabilities of PCM and CPCM. Their study found that adding aluminum foam to cells improves thermal control and that the thickness of PCM significantly impacts BTMSs, although adding more volume has little effect on cell surface temperature. Their study also examined a PCM-based BTMS using capric acid as the PCM and the impact of ambient temperatures. Their study found that a PCM thickness of 3mm provides the optimum and lowest cell temperature of 32 $°$C. Hemery et al. [28] studied the effects of increased internal resistance with age and thermal runaway when cells short circuit in lithium-ion batteries. In this study, for safety considerations, a combination of electrical heaters enclosed in casing was used instead of actual cells, along with forced air convection as a cooling medium. Cell surface temperature under failure was maintained at 60 $°$C in the PCM-enhanced BTMS. In the case of forced air convection, cell temperatures exceeded 60 $°$C. Also, the volume percentage of the PCM-enhanced BTMS was reduced from 79.7% [29] to 25% in comparison to those in previous studies.