Preparation of Boron Nitride Nanosheet/Nanofibrillated Cellulose Nanocomposites with Ultrahigh Thermal Conductivity via Engineering Interfacial Thermal Resistance

With the rapid development of modern electronics toward miniaturization, high‐degree integration, and multifunctionalization, increased heat is generated during the operation of devices, which seriously limits the performance, lifetime, and reliability of electronic devices. Polymer‐based composites with high thermal conductivity have attracted much attention in solving the heat dissipation issue. However, conventional polymer‐based composites can hardly achieve a thermal conductivity of over 10 W m −1 K −1 , due to high interfacial thermal resistance. Herein, engineering interfacial thermal resistance in boron nitride nanosheet/nanofibrillated cellulose nanocomposites by constructing nanoscale silver “bridges” between fillers is reported, aiming at achieving a high thermal conductivity. The highest in‐plane thermal conductivity is up to 65.7 ± 3.0 W m −1 K −1 , which is one order magnitude higher than those of conventional polymer‐based composites. By fitting the experimental data with theoretical models, it is quantitatively demonstrated that silver nanoparticles can help to sharply decrease the interfacial thermal resistance between adjacent boron nitride nanosheets. In addition, the small amount of silver hardly affects the electrical insulation of boron nitride nanosheet/nanofibrillated cellulose nanocomposites. This strategy can potentially pave the way for the design and preparation of highly thermally conductive materials in the future.