Lignin carbon aerogel/nickel binary network for cubic supercapacitor electrodes with ultra-high areal capacitance

It is crucial for energy storage devices to manufacture the thick electrode with high energy and power density. The electrochemical performance of the commercial porous carbon supercapacitor electrode fabricated by traditional methods is highly dependent on the electrode thickness. Therefore, a cost-effective method is required to fabricate thick electrode with high mass loading, high specific capacitance and superior rate performance. Herein an ultra-thick cubic electrode is fabricated based on lignin carbon aerogel/nickel (LCAN) bulk with binary network structure using polymerization under ZnCl 2 hypersaline condition. This is an efficient and low-cost route to prepare carbon aerogels without drying under rigorous condition and ZnCl 2 is an ideal porogen, activating agent and hard template for LCAN. The precise adjustment of ZnCl 2 /lignin ratio and the combination of LCAN binary network results in the cubic electrode (thickness up to 4.2 mm), with an ultra-high areal capacitance of 26.6 F cm −2 (63% retained from 1 to 200 mA cm −2 ), an excellent cycle stability even with high mass loading (∼147 mg cm −2 ) and myriad shapes. These features represent the highest areal capacitance values reported carbonaceous thick electrodes. With these unique features, this study represents a promising 3D thick electrodes for energy-related devices. • A cost-effective preparation required only 15 h to synthesize the desired electrodes from technical lignin. • High areal capacitance performance was realized by optimizing ZnCl 2 /lignin ratio to alter porous structure and mass load. • Thickness/shape independent capacitance performance was realized by combining lignin carbon aerogel and Ni binary network. • 26.6 F cm −2 , 181 F g −1 were achieved at 1 mA cm −2 with electrode thickness up to 4.2 mm.