Recent progress in solution assembly of 2D materials for wearable energy storage applications

Wearable energy storage devices are desirable to boost the rapid development of flexible and stretchable electronics. Two-dimensional(2 D) materials, e.g., graphene, transition metal dichalcogenides and oxides,and MXenes, have attracted intensive attention for flexible energy storage applications because of their ultrathin 2 D structures, high surface-to-volume ratio, and unique physical/chemical properties. To achieve commercialization of 2 D material-based wearable energy storage devices(2 DM-WESDs), scalable and cost-efficient manufacturing is a critical challenge. Among existing manufacturing technologies,solution-based assembly strategies show strong potential to achieve low-cost and scalable production.A timely review of the recent progress in solution-based assembly strategies and the resultant 2 DMWESDs will be meaningful to guide the future development of 2 DM-WESDs. In this review, first, a brief introduction of exfoliation and solution preparation of 2 D material species from bulk materials is discussed. Then, the solution-based assembly strategies are summarized, and the advantages and disadvantages of each method are compared. After that, two major categories of 2 DM-WESDs, supercapacitor and battery, are discussed, emphasizing their state-of-the-art energy storage performances and flexibilities.Finally, insights and perspectives on current challenges and future opportunities regarding the solution assembly of 2 DM-WESDs are discussed.