Nanocellulose as a Sustainable Building Block to Construct Eco-Friendly Thermally Conductive Composites

Nanocellulose, as a promising building block for preparing eco-friendly composites, has gained substantial attention due to its distinctive features such as biodegradability, renewability, and outstanding mechanical properties. Especially, the one-dimensional architecture of nanocellulose makes it difficult to fully encapsulate thermally conductive fillers, which is very beneficial to reduce the insulating contacts between adjacent fillers and enhance the thermal conductivity of the resulting composites. Consequently, recent years have witnessed a growing interest in nanocellulose-based thermally conductive composites. Herein, recent progress in this field is reviewed to deliver the readers a comprehensive understanding of the thermal conduction properties of various nanocellulose-based composites, and thus provide valuable inspiration for designing and constructing green thermal management materials. We begin with an introduction of the structure and properties of nanocellulose, and reveal the thermal conduction mechanisms of nanocellulose and nanocellulose-based composites. Subsequently, we highlight recent advances in nanocellulose-based highly thermally conductive composites distinguished by the nanostructure of thermally conductive fillers (e.g., 0D, 1D, 2D nanofillers and nanohybrids), which involve their manufacturing techniques, design concepts, structure-properties relationships, and underlying principles. Finally, remaining challenges and future perspectives for nanocellulose-based highly thermally conductive composites are discussed.