Core–Shell\nEngineered Fillers Overcome the\nElectrical-Thermal Conductance Trade-Off

The rapid development of modern electronic\ndevices increasingly\nrequires thermal management materials with controllable electrical\nproperties, ranging from conductive and dielectric to insulating,\nto meet the needs of diverse applications. However, highly thermally\nconductive materials usually have a high electrical conductivity.\nIntrinsically highly thermally conductive, but electrically insulating\nmaterials are still limited to a few kinds of materials. To overcome\nthe electrical-thermal conductance trade-off, here, we report a facile\nPechini-based method to prepare multiple core (metal)/shell (metal\noxide) engineered fillers, such as aluminum-oxide-coated and beryllium-oxide-coated\nAg microspheres. In contrast to the previous <i>in situ</i> growth method which mainly focused on small-sized spheres with specific\ncoating materials, our method combined with ultrafast joule heating\ntreatment is more versatile and robust for varied-sized, especially\nlarge-sized core–shell fillers. Through size compounding, the\nas-synthesized core–shell-filled epoxy composites exhibit high\nisotropic thermal conductivity (∼3.8 W m<sup>–1</sup> K<sup>–1</sup>) while maintaining high electrical resistivity\n(∼10<sup>12</sup> Ω cm) and good flowability, showing\nbetter heat dissipation properties than commercial thermally conductive\npackaging materials. The successful preparation of these core–shell\nfillers endows thermally conductive composites with controlled electrical\nproperties for emerging electronic package applications, as demonstrated\nin circuit board and battery thermal management.