Compressible monolithic porous carbon derived from agar/melamine sponge composite hydrogel for advanced supercapacitors

A monolithic porous carbon is prepared from agar/melamine sponge composite hydrogel. • The prepared porous carbon is compressible. • The prepared monolithic carbon exhibits outstanding capacitive performance. • The proposed synthetic strategy offers an effective route to monolithic porous carbons. High-performance electrode materials are crucial for advancing supercapacitor technology. Herein, a monolithic porous carbon material is synthesized using an agar/melamine sponge (AG/MS) composite hydrogel as the precursor. The composite hydrogel is fabricated by exploiting the unique gelation behavior of agar. Through subsequent freeze-drying and high-temperature carbonization, a self-standing porous carbon monolith is obtained. The pore structure of the agar/melamine sponge derived carbon is modulated via KOH activation. The resulting monolithic porous carbon (denoted as KAMC) features a hierarchically porous structure and a substantial specific surface area of 1570.3 m 2  g −1 . Electrochemical evaluation in a 3 M KOH electrolyte reveals that the KAMC electrode delivers a high specific capacitance of 364.2 F g −1 at 1 A g −1 . Moreover, it exhibits exceptional rate performance, retaining 92.3% of its capacitance when the current density is increased to 10 A g −1 . A symmetric quasi-solid-state supercapacitor assembled with two KAMC electrodes achieves an energy density of 9.80 Wh kg −1 , demonstrating the material's potential for high-performance energy storage applications. This work provides a straightforward and effective approach for preparing monolithic carbon-based electrode suitable for advanced supercapacitors. Download: Download high-res image (143KB) Download: Download full-size image