Superior ionic thermoelectric performance enabled by lignocellulose channel reconstruction in all-wood gels

Abstract

Efficient ionic thermoelectric (i-TE) conversion relies on maximizing the thermal diffusion asymmetry between cations and anions. However, sustainable strategies for directing cation-selective thermodiffusion through structural engineering remain largely underexplored. Here, we report an all-wood ionic gel (RW i-TE) that achieves superior thermopower enabled by a lignocellulose channel reconstruction strategy within the wood cell wall. Partial dissolution and regeneration of delignified wood, followed by reintroduction of sodium lignosulfonate (Na:lignin) under hydrogen bond-disrupting conditions (NaOH and urea), enables molecular-level integration between dissociated cellulose and Na:lignin, while simultaneously inhibiting microfibril reassembly. The resulting reconstructed lignocellulose ion channels, enriched with surface negative charges and spatially confined fixed anions, promote rapid and selective cation migration driven by a temperature gradient. As a result, the optimized RW i-TE achieves a high thermopower (S_i) of +39.1 mV K⁻¹ and an ionic figure of merit (zT_i) of 1.68 at 50 % relative humidity, delivering an energy density of 68.75 J m⁻² over 2 h of discharging under a 5 K temperature gradient in generator mode. Moreover, this strategy is compatible with various woody and gramineous biomass sources, offering a renewable alternative to polymer-ionic liquid gels by enabling structure-induced ion confinement within regenerated lignocellulose matrices.