The explosion of electric vehicles (EVs) has triggered massive growth in power lithium-ion batteries (LIBs). The primary issue that follows is how to dispose of such large-scale retired LIBs. The echelon utilization of retired LIBs is gradually occupying a research hotspot. Solving the issue of echelon utilization of large-scale retired power LIBs brings not only huge economic but also produces rich environmental benefits. This study systematically examines the current challenges of the cascade utilization of retired power LIBs and prospectively points out broad prospects. Firstly, the treatments of retired power LIBs are introduced, and the performance evaluation methods and sorting and regrouping methods of retired power LIBs are comprehensively reviewed for echelon utilization. Then, the problems faced by the scenario planning and economic research of the echelon utilization of retired power LIBs are analyzed, and value propositions are put forward. Secondly, this study summarizes the technical challenges faced by echelon utilization in terms of security, performance evaluation methods, supply and demand chain construction, regulations, and certifications. Finally, the future research prospects of echelon utilization are discussed. In the foreseeable future, technologies such as standardization, cloud technology, and blockchain are urgently needed to maximize the industrialization of the echelon utilization of retired power LIBs.

The heat dissipation capability of the battery thermal management system (BTMS) is a prerequisite for the safe and normal work of the battery. Currently, many researchers have designed and studied the structure of BTMS to better control the battery temperature in a specific range and to obtain better temperature uniformity. This allows the battery to work safely and efficiently while extending its life. As a result, BTMS has been a hot topic of research. This work investigates the impact of pin-fins on the heat dissipation capability of the BTMS using the computational fluid dynamics (CFD) approach, designs several BTMS schemes with different pin-fin structures, simulates all schemes for fluid-structure interaction, and examines the impact of different distribution, number, and shape of pin-fins on heat dissipation capability and pressure drop. Analyzing the effect of cooling plates with different pin-fins on the thermal capability of the BTMS can provide a basis for the structural design of this BTMS with pin-fin cooling plates. The findings demonstrate that the distribution and quantity of pin-fin shapes might affect heat dissipation. The square-section pin-fins offer better heat dissipation than other pin-fin shapes. As the pin-fins number increases, the maximum battery temperature decreases, but the pressure drop increases. It has been observed that uniform pin-fin distribution has a superior heat dissipation effect than other pin-fin distribution schemes. In summary, the cooling plate with a uniform distribution of 3 × 6 square section pin-fins has better heat dissipation capability and less power consumption, with a maximum battery temperature of 306.19 K, an average temperature of 304.20 K, a temperature difference of 5.18 K, and a pressure drop of 99.29 Pa.

Battery Thermal Management System (BTMS) is crucial to maintain peak temperature and temperature difference of lithium-ion battery pack in appropriate range, thus ensuring best performance, extended cycle life and safety. Liquid cooling BTMS is extensively researched for prismatic cells, but only a few studies are present on application of liquid cooling BTMS for cylindrical cells. Further, existing studies on liquid cooling for cylindrical cells majorly focus on effect of flowrate, flow direction, and number of channels. In this study, a novel mini-channel cooling plate-based liquid cooling BTMS is proposed for a battery pack of 20 cells. Computational fluid dynamics (CFD)-based numerical analysis was performed on three-dimensional model of battery pack to investigate effects of parameters associated with cooling plate and mini-channel design, flow characteristics, and battery arrangement on temperature uniformity, heat removal rate, parasitic power consumption and weight of the battery pack. The study concluded that installation of aluminum cylindrical enclosure on cells could drastically enhance heat removal and temperature uniformity. Altering flow directions in mini-channel could enhance thermal performance. The research demonstrated that for case 2d (inlet and outlet are staggered in each cooling plate), the temperature difference can be reduced by 16.5% when compared to unidirectional flow. Mini-channel with square cross section offers better heat removal and fewer flow resistance compared to circular and elliptical. Although converging mini-channels offer better thermal performance, it drastically increases the pumping power. The battery pack was successful in limiting peak temperature and temperature difference to 303.26 K and 1.98 K, respectively, for 4 C discharge rate.