Novel scalable freezing-pore-forming strategy for constructing hierarchically porous carbon materials for supercapacitors

Abstract

Large specific surface area and hierarchically porous texture play a critical role in achieving high-performance carbon electrode materials. Scalable effective pore-forming strategies are expected for constructing porous carbon materials to date. Herein, we designed an easily scalable freezing-and-extraction-and-thermally-drying approach, using low-cost sodium carboxymethyl cellulose (CMC) as the raw material, to prepare CMC-derived hierarchical porous carbons (CHPC) for supercapacitors. Due to the developed pore structure formed by ice microcrystals, CHPC exhibits high specific surface area and outstanding electrochemical energy storage performance. At a current density of 1 A g−1, the specific capacitance of CHPC-1, which was prepared only employing freezing-and-extraction-and-thermally-drying method, reached 162.7 F g−1. For the CHPC samples prepared when combined with Cu(CH3COO)2 etching or KOH activation, the specific capacitance is up to 196.4 F g−1 (CHPC-2) and 263.8 F g−1 (CHPC-3) at 1 A g−1, respectively. All samples have excellent rate performance with a capacitance retention of about 80% at 40 A g−1. The CHPC-3//CHPC-3 all-solid-state symmetrical supercapacitor exhibits an energy density of 5.9 Wh·kg−1 at a power density of 249.9 W kg−1. This demonstrates that our innovative freezing-and-extraction-and-thermally-drying strategy is an effective avenue for preparing high-performance porous carbon electrode materials.