Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators.

Thermal management has become a crucial problem for high-power-density equipment and devices. Phase change materials (PCMs) have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition. However, low intrinsic thermal conductivity, ease of leakage, and lack of flexibility severely limit their applications. Solving one of these problems often comes at the expense of other performance of the PCMs. In this work, we report core-sheath structured phase change nanocomposites (PCNs) with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning, electrostatic spraying, and hot-pressing. The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m K at a low BNNS loading (i.e., 32 wt%), which thereby endows the PCNs with high enthalpy (> 101 J g), outstanding ductility (> 40%) and improved fire retardancy. Therefore, our core-sheath strategies successfully balance the trade-off between thermal conductivity, flexibility, and phase change enthalpy of PCMs. Further, the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators, displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.