To solve the problems of low thermal conductivity and uneven temperature dis¬tribution of PCM in thermal management of electric vehicle power batteries, this paper proposes a triple innovative solution: constructing efficient thermal con¬duction paths with 3-D graphene networks, designing regional phase change units with honeycomb structures, and optimizing simulation accuracy with non-steady-state coupling models. The experimental and simulation results show that the ther¬mal conductivity of the composite PCM is increased to above 1.8 W/mK, and the temperature uniformity error is controlled at ±1℃. At an ambient temperature of –10-45℃ and a charge and discharge rate of 1-3C, the maximum temperature of the bionic structure + composite PCM system (experimental group B) is 8.6℃ lower than that of the control group, the equilibrium time is shortened by 29% during 3C discharge, the phase change latent heat retention rate reaches 91% after 2000 cycles, and the simulation accuracy exceeds 95%. This solution offers practical technical support for the thermal management of high safety, long-life power batteries.