具有纳米结构的木材气凝胶基电极的制备及其电化学性能

Preparation of nano-structured wood aerogel-based composite electrode and its electrochemical performance

超级电容器作为清洁可持续的储能设备,其电化学性能主要由电极材料决定,因此电极材料逐渐成为当前储能领域的研究热点。木材因其天然的多尺度微/纳米孔隙结构以及可再生、可生物降解等特点,逐渐被用于电极材料的研究。以巴沙木为基材,首先采用脱木素联合TEMPO氧化法将木材细胞壁分离具有纳米网络结构的木材气凝胶(TDW),然后将纳米纤维素分散的碳纳米管(CNT)悬浮液通过满细胞法浸渍到木材气凝胶中,冷冻干燥后在导管孔和细胞间隙中形成了连续的碳纳米管导电网络结构,最后进行聚吡咯(PPy)原位聚合,在细胞壁和导管孔中构建成具有纳米导电网络结构的TDW/CNT/PPy复合电极。电化学性能测试显示,由于在TDW的宏观孔隙中导电网络的构建,TDW/CNT/PPy的电化学性能明显优于TDW/PPy电极,而且随着碳纳米管比例的增加而增强,其中,TDW/CNT-2/PPy在1.0 mA/cm^(2)扫描速率下的比电容达到389 F/g、面电容为10.5 F/cm^(2),而且在10 mA/cm^(2)扫描速率下经过10000次循环后的电容保持率为95.1%。本研究通过在木材中构建连续的导电纳米网络结构,显示出优异的电化学性能,为木质基材在电极材料中的应用提供了一种新的思路。

Supercapacitors are clean and sustainable energy storage devices and their electrochemical performances are mainly determined by the electrode material,so the electrode material has gradually become a current research hotspot in the field of energy storage.Due to its natural multi-scale micro/nano pore structure and renewable and biodegradable characteristics,wood has gradually been used to be electrode raw materials.As a renewable resource,wood s na-tural multi-scale micro/nano pore structure facilitates rapid electrolyte penetration,electron transfer and charge storage,making it an ideal substrate material for electrodes.Currently,electrode materials based on natural wood are mainly prepared by delignification or carbonization.High-temperature carbonization can improve the porous structure and electrical conductivity of wood,and the introduction of heteroatoms and metal ions for sintering during the carbonization process can improve its electrical conductivity and energy density.However,wood as a carbonaceous material can only provide limited double-layer capacitance,which limits its energy density,while carbonization can make the substrate brittle and the wood tissue collapse,which is not conducive to practical applications.Although the delignification treatment improved the nano-pore structure of wood to some extent,the microfilaments in the cell walls are still closely arranged and difficult for conductive materials to enter the cell walls,resulting in no continuous conductive network structure in the cell walls.In this study,using the balsa wood as the substrate,the cell wall of the wood was firstly separated from the wood aerogel(TDW)with a nano-network structure by delignification combined with TEMPO oxidation,then a suspension of nano-cellulose dispersed carbon nanotubes(CNT)was impregnated into the wood aerogel by the full cell method.After freeze-drying,a continuous carbon nanotube conductive network structure was formed in the duct pores and cell interstices,and finally polypyrrole(PPy)was polymerized in situ to construct a TDW/CNT/PPy composite electrode with a nano-conductive network structure in the cell walls and duct pores.Electrochemical performance tests showed that the electrochemical performance of the TDW/CNT/PPy electrode was significantly better than that of the TDW/PPy electrode due to the construction of a conductive network in the macroscopic pores of the TDW,and enhanced with increasing proportions of carbon nanotubes.TDW/CNT-2/PPy achieved a specific capacitance of 389 F/g at 1.0 mA/cm^(2),a surface capacitance of 10.5 F/cm^(2) and a capacitance retention rate of 95.1%after 10000 cycles at a scan rate of 10 mA/cm^(2).The research showed excellent electrochemical properties by constructing continuous conductive nano-network structures in wood,providing a new idea for the application of wood substrates in electrode materials.