Lignocellulose-based free-standing hybrid electrode with natural vessels-retained, hierarchically pores-constructed and active materials-loaded for high-performance hybrid oxide supercapacitor.

Abstract Lignocellulose including cellulose, lignin, and hemicellulose could be extracted from wood, and has been used to prepare carbon electrode. However, complicated extraction greatly increases preparation cost. To achieve maximum utilization of lignocellulose and avoid complicated extraction, wood with porous structure and good mechanical strength is used as carbon precursor. Additionally, chemical activation is commonly used to create micropores to provide high capacitance, but it brings in natural structure destruction, and generation of wastewater during pickling. Moreover, to achieve desirable energy density, multi-step strategy with long duration is required for loading active materials on carbonized lignocellulose (CL). Herein, a one-step method is developed to prepare a free-standing hybrid CL electrode (CLE) by using Lewis acid in three aspects: (1) as structure protection agent, (2) as activating agent, (3) as active materials donor, which bypasses pickling and further avoids the generation of wastewater. Additionally, natural vessels in wood can not only provide large space for active materials loading, but also act as rapid ions diffusion way, simultaneously confining active materials detachment. Benefiting from the synergistic effect of porous structure and Lewis acid, this work not only makes full utilization of lignocellulose, but also makes CLE exhibit excellent performance in hybrid oxide supercapacitor.