Cellulose nanocrystals-based nanocomposites for sustainable energy storage technologies: From aligned microstructures to tailored performances

The fast-moving development of emerging portable electronics and the rise of electric transportation with smart grids promote the ever-growing demand for sustainable, environmentally friendly, safe and large-scale electrochemical energy storage technologies. Notwithstanding lithium-ion batteries (LIBs) have dominated the current market as commonly used energy storage devices, the limited resources of lithium and the soaring costs have greatly restricted their long-lasting applications in the future. Therefore, sodium-ion, potassium-ion, and sodium-metal batteries have emerged as promising next-generation energy storage systems due to their abundance and cost-effectiveness. This review explores the transformative potential of cellulose nanocrystals (CNCs), derived from renewable biomass, as sustainable and high-performance materials for these emerging battery technologies. CNCs exhibit exceptional mechanical properties, biodegradability, and scalability, positioning them as ideal candidates for reinforcing electrodes and separators in nanocomposites. Herein, particular emphasis is placed on designing and fabricating aligned microstructures using appealing strategies such as unidirectional ice-templating and highly aligned electrospinning, which can tailor enhanced electrochemical performance and stability. By integrating CNC-based nanocomposites with the tailored aligned microstructures into battery designs, this unique review highlights principles, research progress and advancements that pave the way toward sustainable, safe, low-cost, efficient, and scalable energy storage solutions for a net-zero-emission future and circular economy. This unique, novel and comprehensive review summarises the principles, basics, and progress in cellulose nanocomposites' sustainable and next-generation energy storage technologies. Remarkably, this novel review also proposes and emphasizes the appealing design of aligned microstructures via emerging manufacturing approaches ( e.g., unidirectional ice-templating, highly aligned electrospinning) to tailor the electrochemical properties of critical components ( e.g., electrodes, and separators) of high-performance and highly-safe sodium/potassium ion-based batteries.Schematic illustration of the cellulose building blocks (CMF, NCF, CNC) and cellulose-derived materials and their applications on sustainable energy storage. Adapted from ref [1]. • The structural, mechanical and electrochemical advantages of CNC nanocomposites for post-lithium-ion battery technologies. • The novel design of aligned microstructures in battery components to enhance/tailor ion transport and cycling stability. • The scalability and industrial relevance of CNC-based technology innovations to achieve net-zero emission energy systems.