Hierarchically porous wood aerogel/polypyrrole(PPy) composite thick electrode for supercapacitor

Recently, nanocellulose-based electrode materials have garnered considerable attention in the field of energy storage owing to their high specific surface area, biodegradability and superior mechanical strength, etc. However, these nanocelluloses require complex manufacturing processes that are energy intensive and costly, in addition, they couldn’t meet the requirement of thick electrode for storage devices of high-energy density. In this study, a novel two-step strategy has been developed to convert the natural wood into aerogel by keeping the hierarchical pore structure. The bulk wood was delignified and followed by TEMPO treatment to construct puffy nanocelluloses network architecture in the resulted wood aerogel. Then, polypyrrole (PPy) in-situ grew onto the interior of wood aerogel to form a successively conductive three-dimensional network. The wood aerogel/PPy composite based electrode exhibits excellent areal and specific capacitance of 7.68 F·cm−2 and 206 F·g−1 at a current density of 1.0 mA·cm−2, respectively, and realizes an appropriate capacitance retention of 82.6% over 10,000 cycles at 10 mA·cm−2. Moreover, an excellent energy density of 0.75 mWh·cm−2 (20 Wh·kg−1) at a power density of 6061.9 mW·cm−2 (161.6 W·kg−1) could be achieved using the symmetrical supercapacitor device based on wood-aerogel-based electrode. More interestingly, the power density was seldom affected by the wood-aerogel electrode thickness (1 ∼ 4 mm) due to the hierarchical pore structure. Therefore, the strategy in this study would promote further development of wood-based electrodes in the relevant domains of energy storage.