Yuliang Wen

Thermal safety issues of sodium-ion batteries have become a major challenge, particularly under abusive conditions where the risk of thermal runaway is heightened. This study investigates the effects of overcharging on the thermal safety of sodium-ion batteries. Discharge capacity and time, internal resistance, and electrochemical impedance spectroscopy (EIS) at different states of charge (SOCs) are analyzed. Additionally, heat generation behaviors are evaluated at both normal/elevated temperatures. It is found that the overcharged batteries (OBs) demonstrate a significant increase in internal resistance from 46.72 Ω to 65.99 Ω. The discharge time of OBs at 1 C current (the ratio of the rate at which a battery discharges per unit time to its rated capacity) is reduced by 4.26% compared to normal batteries (NBs). The peak temperature and temperature difference increase by 5.6% and 36.1%, respectively. When discharged at 1 C at 40 °C, OBs have a 5.47% reduction in discharge time compared to NBs. Furthermore, the OBs exhibit an increase in the peak discharge temperature and temperature difference of 0.99 °C and 0.4 °C, respectively. Microscopic analysis of the electrode materials makes clear the irreversible damage to the internal structures of the sodium-ion battery caused by overcharging. This study potentially provides fundamental data support and theoretical insights for sodium-ion battery module thermal safety.

The proton exchange membrane electrolysis cell (PEMEC) has attracted considerable attention for large-scale and efficient hydrogen production because of its high current density, high hydrogen purity and fast dynamic response. Flow field distributions and water and thermal management characteristics of a PEMEC are vital for electrolytic cell structure and the determination of operating condition. A three-dimensional, non-isothermal, electrochemical model of a PEMEC was established in this manuscript. The flow field distribution and water and thermal management of the PEMEC are discussed. The corresponding results showed that the pressure of the flow channel decreased diagonally from the inlet to the outlet, and the pressure and velocity distribution exhibited a downward opening shape of a parabola. At the same inlet flow rate, when the voltage was 1.6 V, the oxygen generation rate was 15.74 mol/(cm²·s), and when the voltage was 2.2 V, the oxygen generation rate was 332.05 mol/(cm²·s); due to the change in the oxygen production rate, the pressure difference at 2.2 V was 2.5 times than that at 1.6 V. When the stoichiometric number was less than two, the average temperature of the catalyst layer (CL) decreased rapidly with the increase in the water flow rate. When the voltage decreased to 2.1 V, the current density came to the highest value when the stoichiometric number was 0.7, then the current density decreased with an increase in the stoichiometric number. When stoichiometric numbers were higher than five, the surface temperature and current density remained basically stable with the increase in the water flow rate, and the water and thermal management and electrolysis characteristics performed better. The research results could optimize the water supply of electrolysis cells. According to the velocity distribution law of the flow field, the water and thermal management performance of the PEMEC could be estimated, further promoting safety and reliability.

Electric vehicles (EVs) are experiencing explosive developments due to their advantages in energy conservation and environmental protection. As a pivotal component of EVs, the safety performance of lithium-ion batteries directly affects driving miles and even safety; hence, a battery thermal management system (BTMS) is especially important. To improve the thermal safety performance of power battery modules, first, a new leak-proof phase change material (PCM)-coupled liquid-cooled composite BTMS for large-scale battery modules is proposed in this research. Second, the numerical simulation analysis method was utilized to analyze the influences of the fluid flow channel shape, working fluid inlet temperature, inlet velocity, and reverse flow conditions on the BTMS. Eventually, the abovementioned performances were compared with the traditional PCM-coupled liquid-cooling strategy. The relative data indicated that the T_max was reduced by 17.5% and the ΔT_max was decreased by 19.5% compared to the liquid-cooling approach. Further, compared with conventionally designed PCM composite liquid cooling, the ΔT_max was reduced by 34.9%. The corresponding data showed that, when using the e-type flow channel, reverse flow II, the inlet flow velocity was 0.001–0.005 m/s, and the inlet temperature was the ambient temperature of the working condition. The thermal performance of the anti-leakage system with a thermal conduction slot PCM-coupled liquid-cooling composite BTMS reached optimal thermal performance. The outcome proved the superiority of the proposed BTMS regarding temperature control and temperature equalization capabilities. It also further reduced the demand for liquid-cooling components, avoided the problem of the easy leakage of the PCM, and decreased energy consumption.

Electric vehicles (EVs) are experiencing explosive development due to their advantages in energy conservation and environmental protection. As an important component of EVs, safety performance of lithium-ion batteries will directly affect the driving miles and even safety. Hence, battery thermal management system (BTMS) is particularly important. To improve the thermal safety performance of power battery modules, firstly, a new leak-proof phase change material (PCM) coupled liquid-cooled composite BTMS for large-scale battery modules was proposed in this paper. Secondly, the numerical simulation analysis method was utilized to analyze the influence of fluid flow channel shape, working fluid inlet temperature, inlet velocity, counterflow conditions on the BTMS. Eventually, the above performance is compared with the traditional PCM coupled liquid cooling strategy. Relative data indicated the maximum temperature was reduced by 17.5% and the maximum temperature difference was decreased by 19.5% compared to liquid cooling approach. Moreover, compared with conventionally designed PCM composite liquid cooling, the maximum temperature difference was reduced by 34.9%. The corresponding data showed that when using the e-type flow channel, counterflow II, the inlet flow velocity is 0.001-0.005 m/s, and the inlet temperature is the ambient temperature of the working condition, the thermal performance of the anti-leakage PCM coupled liquid cooling composite BTMS reached optimal thermal performance. The outcome proved the superiority of the proposed anti-leakage PCM coupled liquid cooling composite BTMS in temperature control and temperature equalization capabilities. Meanwhile, it also further reduced the demand for liquid cooling components, avoided the problem of easy leakage of PCM, and also decreased energy consumption.

The thermal safety of decommissioned lithium-ion batteries is considered to be a common and crux technical issue. A novel composite phase change materials (CPCM) based on paraffin (PA)/cubic boron nitride (CBN)/silicon dioxide (SiO2) was proposed in this paper. Firstly, SiO2 and BN were selected as functional additives to prepare CPCM with different SiO2 ratios employing physical mixing melting method. Secondly, the effects of different ratios of SiO2 on thermal properties, thermal conductivity, thermal stability, mechanical strength, electrical insulation properties and flow properties of CPCM were studied. Furthermore, the microscopic characterization methods were used to reveal the root cause of the aforementioned performance changes. The macroscopic and microscopic results show that the CPCM possessing 5% SiO2 possess the optimum comprehensive performance. Eventually, the best-performing CPCM was used in the thermal management evaluation of the decommissioned 18650 ternary battery module. The test data show that even under the severe conditions of high temperature (40℃) and 1.5 C higher discharge rate uninterrupted charge-discharge cycle, the maximum temperature and maximum temperature difference of the CPCM battery module are reduced by 8.45℃ and 5.40℃ comparing with forced air cooling (FAC), respectively, which exhibits significant temperature control and temperature equalization capabilities.

In order to ensure the HVDC convertor valve works properly, the heat produced from the valve must be dissipated into the atmosphere to keep the device within the normal temperature range. However, efficiency of the valve cooling system is affected by environment temperature. In water deficient areas, the traditional circulating water cooling tower is not normally adopted. And the heat dissipation capacity of the conventional water-air exchanger system is insufficient in summer as the ambient temperature is higher than 40 ^o C. Therefore, a cold storage system combined with air cooling system was presented. This study and test show that the proposed cold storage system can maintain the temperature entering into the HVDC thyristor valve within the designed range.