Nanocellulose-based functional materials for advanced energy and sensor applications

Advanced energy and sensor devices with novel applications (e.g., mobile equipment, electric vehicles, and medical-healthcare systems) are one of the important foundations of modern intelligent life. However, there are still some scientific issues that seriously hinder the further development of devices, including unsustainability, high material cost, complex fabrication process, safety issues, and unsatisfactory performance. Nanocellulose has aroused tremendous attention in recent decades, because of its abundant resources, renewability, degradability, low-cost, and unique physical/chemical properties. These merits make nanocellulose as matrix materials to fabricate advanced functional composites for use in energy-related fields extremely competitive. Here, we comprehensively discuss the recent progress of nanocellulose for emerging energy storage/harvesting and sensor applications. The preparation methodologies of nanocellulose combined with conductive materials are firstly highlighted, including carbon materials, conductive polymers, metal/metal oxide nanoparticles, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). We then focus on the nanocellulose-based advanced materials for the application in the areas of supercapacitors, lithium-ion batteries, solar cells, triboelectric nanogenerators, moisture-enabled electric generators, and sensors. Lastly, the future research directions of nanocellulose-based functional materials in energy-related devices are presented.