Performance analysis of a hybrid thermal management system for lithium-ion batteries based on topology-optimized cooling plate and phase change material

Efficient thermal management is essential for maintaining lithium-ion batteries within a safe operating temperature range and ensuring reliable operation in electric vehicles. However, passive phase change material cooling may suffer from latent heat saturation during continuous high-rate discharge, while liquid cooling plates with predefined channels are limited by constrained flow-path design and hydraulic resistance. This work hypothesizes that coupling a topology-optimized liquid cooling plate with phase change material can improve the balance among maximum temperature control, temperature uniformity, and pressure drop in cylindrical lithium-ion battery packs. A hybrid active–passive thermal management system was developed for an eight-cell cylindrical 18650 lithium-ion battery pack, and multi-objective topology optimization was used to design liquid cooling channels under different inlet and outlet configurations. Numerical simulations show that the topology-optimized cooling plate with the central inlet and outlet configuration provides the best overall performance, achieving a maximum battery temperature of 308.08 K, a maximum temperature difference of 3.44 K, and a pressure drop of 3.17 Pa under a 4C discharge rate. Orthogonal experimental design combined with the entropy weight method further identifies the optimal operating condition as an inlet velocity of 0.04 m/s, an inlet temperature of 292.15 K, and RT31 as the phase change material. These results demonstrate that the proposed hybrid system can simultaneously improve thermal regulation and reduce hydraulic resistance, providing a practical reference for the design and operating-parameter selection of high-efficiency battery thermal management systems.