Flexible and Thermally Conductive Phase-Change Films with a Two-Level Network for Dual-Mode Thermal Management of Batteries

Phase-change materials (PCMs) are extensively employed for battery thermal management, owing to their significant thermal storage capacity and appropriate temperature range. Nevertheless, their limitations in terms of flexibility, thermal conductivity, and susceptibility to leakage restrict their effective temperature control. Here, a kind of flexible and thermally conductive phase-change film (TCPCF) with a two-level heat conduction network is prepared, which is composed of phase-change microparticles and graphene nanosheets in the network of polyurethane. The resulting TCPCF demonstrates remarkable flexibility, sufficient latent heat of 97 J/g, high thermal conductivity of 1.77 W/m·K, and exceptional resistance to leakage (<1%) at 65 °C. Furthermore, TCPCF facilitates effective thermal management of Li-ion batteries (LIBs) in diverse environmental conditions. Specifically, in cold environments, the outstanding photothermal conversion capability of TCPCF expedites the warming of LIBs, resulting in a 15.8% increase in battery capacity. In hot environments, TCPCF can reduce LIBs operating temperatures by 15 °C. Consequently, this research presents a promising strategy for enhancing the thermal management of systems with analogous preheating and heat dissipation needs.