Mechanical-thermal coupling design on battery pack embedded with concave quadrilateral cellular structure

•The mechanical-thermal relations of CQCS are established.•Thermal runaway of battery pack is inhibited by negative thermal expansion design of CQCS.•CQCS are treated as medium to conduct mechanical-thermal coupling design of battery pack.•Variable density design of cold plate can enhance temperature uniformity of battery pack. To comprehensively investigate mechanical-thermal coupling properties and function-oriented design of battery pack, a novel battery pack with triangular micro-channel cold plate and the optimal embedded concave quadrilateral cellular structure (CQCS) is proposed. Firstly, mechanical properties of CQCS are derived based on beam theory and homogenization theory. Then, thermal conductivity expressions of the CQCS are derived in accordance with Maxwell-Eucken model and negative thermal expansion design of the CQCS is ingeniously conducted to inhibit thermal runaway of battery pack. Moreover, the relations between mechanical properties and thermal properties of CQCS are innovatively investigated through the medium of structural parameters of CQCS. Secondly, modal analyses, collision analyses on conventional battery pack are conducted. Meanwhile, thermal characteristics of battery modules are derived and temperature field distributions are acquired through simulation analysis to provide reference for the design of thermal management system. Subsequently, the embedded CQCS is taken as the medium to conduct mechanical-thermal coupling design of battery pack. Multi-objective optimization models of the CQCS between battery cells and the CQCS between modules are established to obtain the optimal CQCS with the needs of high heat dissipation efficiency, superior temperature uniformity, outstanding collision performances, and more lightweight space of battery pack. Moreover, a convection triangular micro-channel cold plate is chosen as heat dissipation structure and variable density design of micro-channel cold plate is executed to ensure heat dissipation efficiency and temperature uniformity of battery pack. Eventually, the mechanical performances and thermal performances are compared to verify the superiority of the proposed novel battery pack. Compared with conventional battery pack, lower stress levels and more uniform stress distributions can also be achieved, and the resonance between battery pack and autobody can also be avoided effectively. Moreover, compared with conventional battery pack, the maximum temperature differences of battery p