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[Display omitted] • The DW-PU composite was prepared by vacuum immersion of delignified wood with PU. • The DW-PU 1.00 -GPEs exhibited outstanding ion conductivity of 2.90 × 10−2 S cm−1. • DW offered ion transport channels which enhanced the performance of assembled SCs. • The SCs showed excellent cycling stability and energy density of 11.49 W h kg−1. In recent years, more and more people have realized the importance of green and sustainable development. Wood as the most abundant natural biodegradable material on the earth, the preparation of high strength transparent wood (TW) by filling the delignified wood (DW) with resin is a hot research topic at present. Taking this as inspiration, here gel polymer electrolytes (GPEs) with high ionic conductivity were prepared by using DW as substrate, polyurethane (PU) with different ratios of polyethylene glycol (PEG) to 2,2-bis(hydroxymethyl)propionic acid (DMPA) as filling polymer matrix and lithium perchlorate (LiClO 4) as electrolyte through vacuum perfusion method, and applied in solid-state supercapacitors (SCs) with activated carbon as working electrodes. The cell cavity retained in DW provided a controllable ion transport channel, which further improved the efficiency of ion transport and storage. The synthesized DW-PU 1.00 -GPE possessed a splendid ionic conductivity of 2.90 × 10−2 S cm−1 at room temperature (RT). The solid-state SCs assembled with the DW-PU 1.00 -GPE also displayed the highest specific capacitance of 157.7 F g−1 at 0.3 A g−1, the outstanding E cell of 11.49 W h kg−1 and a long cycling life of 4000 cycles with 95 % capacitance retention and nearly 100 % coulomb efficiency. The DW-PU-GPEs achieve efficient Li+ transport with the help of rich internal cavities, especially showing excellent ion conductivity which possess a great development prospect in the application of SCs and broaden the application of wood in the field of electrochemistry. [ABSTRACT FROM AUTHOR]

Soybean protein isolate (SPI) has good reactivity, hydrophilicity and film-forming properties, but its electrochemical performance is poor when used as a polymer electrolyte matrix. The graft-modification of the SPI using polyacrylic acid (PAA) allows the introduction of strong hydrophilic carboxyl groups into the SPI molecular chains. This enables the SPI to effectively absorb electrolytes in the subsequent electrolyte adsorption process, resulting in a modified polymer electrolyte. The resulting constructed supercapacitor can operate stably in a voltage window of 0–2 V and exhibit excellent electrochemical behavior with a high single electrode specific capacitance up to 293.08 F g−1 and an energy density of 38.76 W h kg−1 at a power density of 734.38 W kg−1, which is much better than SPI-based supercapacitor. This simple, low-cost and environmentally friendly approach has a great potential for the development of high-performance supercapacitor with high voltage window, high specific capacitance and high energy density. [Display omitted] • GPE was prepared based on soybean protein isolate grafted by polyacrylic acid. • GPE-SPI-g-PAA exhibited excellent electrolyte/electrode interface performance. • SC-SPI-g-PAA could be operated stably in a potential window of 0–2 V. • SC-SPI-g-PAA could provide a high energy density up to 38.76 W h kg−1. [ABSTRACT FROM AUTHOR]