Thermal conductivity enhancement for multi-functional phase change materials: From random fillers to oriented networks in viscous systems

Enhancing thermal conductivity in viscous multifunctional phase change materials (MPCMs) remains a critical challenge. Conventional filler dispersion or pre-built conductive networks often fail due to poor impregnation, resulting in discontinuous pathways. Here, we present a sequential assembly strategy to reconfigure the microstructure of a high-viscosity olefin block copolymer (OBC) system, constructing a hierarchical (PA@CA)/OBC composite. This design overcomes interfacial issues, enabling complete, oriented thermal-conductive networks. The optimized composite achieves an in-plane thermal conductivity of >10 W m^-1 K^-1 and enhanced vertical conduction. As an anisotropic phase change thermal manager for lithium-ion batteries, it reduces the peak temperature by 16.3°C during 3C-rate discharge, while the radial conductivity increases from 5.36 to 12.64 W m^-1 K^-1. This work resolves the long-standing challenge of viscosity-limited thermal enhancement and provides a generalizable strategy for constructing oriented networks in high-viscosity energy materials, advancing targeted thermal management or energy storage applications.