All-in-one Biomass-Based Flexible Supercapacitors with High Rate Performance and High Energy Density

Taking advantage of the unique structure and properties of gramineous straw that are available across the world in a yearly scale of several hundred million tons, a strategy to design and fabricate flexible high-performance supercapacitors (SCs) is developed, of which the key components including electrode, separator, and electrolyte are all made from the eulaliopsis binata (EB), a ubiquitous gramineous straw. This kind of all-in-one biomass-based flexible supercapacitors (BFSs) is first proposed, with the cuticle-derived fibers (EBMs) as a separator, the pith-derived carbon sponges (EBCs) as an electrode, and the sodium salts of the extracted carboxymethyl cellulose as gel electrolyte. The EBM with uniform diameter size, developed porosity, and abundant -OH/-COOH groups have good flexibility, wettability, and ionic conductivity, far exceeding those of commercial glass-fiber separators. The EBC has a high level of N/O/S co-doping and hierarchical porous structure, resulting in enhanced ion accessibility and supercapacitance. With these advantages, the as-fabricated BFS has shown ultra-high-rate performance, high energy density, and excellent flexibility, surpassing the biomass-derived flexible supercapacitors reported thus far. This novel approach will shed light on the value-added utilization of biomass from the viewpoint of molecular chemical engineering and product engineering and pave the way for fabricating flexible high-performance SCs and beyond. A new all-in-one biomass-based flexible supercapacitor (BFS) is first proposed and fabricated via all-round utilization of gramineous straw, with the pith-derived carbon sponges (EBC) as the electrode, the cuticle-derived uniform-sized fibers (EBM) as the separator, and the sodium salts of the extracted carboxymethyl cellulose as the gel electrolyte. The BFS has shown an ultra-high-rate performance, high energy density, and excellent flexibility, surpassing the biomass-derived flexible supercapacitors (SCs) reported in the literature thus far.image