Structure control of powdery carbon aerogels and their use in high-voltage aqueous supercapacitors

Powdery carbon aerogels (PCAs) for use as electrode materials in high-voltage aqueous supercapacitors were prepared from nanospheres of 1,2-divinylbenzene-styrene copolymer after carbonyl crosslinking. The effect of the size and carbonyl crosslinking conditions of the nanospheres on the microstructure and electrochemical properties of the PCAs were investigated. Results indicated that the size of the nanospheres, the crosslinking temperature and time played important roles in tailoring the nanostructures and electrochemical performance of the PCAs. All the PCAs had a well-defined 3D network and a hierarchical pore structure with a high porosity. The network units were between 25 and 100 nm in size, and the Brunauer-Emmett-Teller (BET) specific surface areas were from 392 to 767 m²g^-1. The PCA with a BET surface area of 657 m²g^-1 had a high electrochemical active surface area, a large capacitance and high capacitance retention rates at high current densities when used as electrodes in a 1.8 V aqueous supercapacitor using a Na₂SO₄ aqueous electrolyte. The use of a high-voltage aqueous electrolyte significantly increased the energy density of the supercapacitors.