Design of a field synergy-based variable cross-section cold plate for enhanced thermal management of lithium-ion batteries at high discharge rates

• The limitations of single serpentine-channel cold plate (SSCP) used in BTMS were highlighted. • A novel variable cross-section double-channel SCP (VCDSCP) was proposed based on field synergy principle. • The VCDSCP reduces maximum temperature by 1.7 % and maximum temperature difference by 10.1 %, outperforming the SSCP. • The VCDSCP lowers pressure drop by 80.8% and increase PEC by 25.5%. A field synergy-guided design approach is proposed for the development of a variable cross-section serpentine-channel cold plate (SCP) to improve the thermal management performance of lithium-ion battery systems operating under high discharge rates. A validated numerical model is developed to evaluate the heat transfer behavior and coolant flow characteristics within the system. The thermal limitations of a conventional single SCP (SSCP) are systematically investigated across a range of inlet temperatures and coolant mass flow rates. To overcome these drawbacks, a novel variable cross-section double-channel SCP (VCDSCP) is introduced based on the field synergy principle. Guided by this principle, the VCDSCP is designed by redistributing the coolant flow and locally adjusting the channel cross-sections to reduce the velocity–temperature gradient synergy angle, particularly in high-temperature regions of the battery. Comparative results demonstrate that the VCDSCP achieves a significantly lower and more uniformly distributed synergy angle than the SSCP, leading to improved temperature control. Under high load conditions, the VCDSCP reduces the maximum battery temperature and temperature difference by 0.54 K (1.7 %) and 0.62 K (10.1 %), respectively. Furthermore, at a coolant mass flow rate of 0.2 g∙s −1 , the design achieves up to 80.8 % reduction in pressure drop and a 25.5 % improvement in performance evaluation criteria. These results suggest that the proposed VCDSCP offers substantial advantages for next-generation battery thermal management systems with high operational demands.