Narrow Results

Micro-porous activated carbons (ACs) with a narrow pore size distribution of 0.4–0.6nm and high specific surface areas (1160–1315m²$\cdot$ g${}^{-1})$ are prepared from environment-friendly, low-grade potassium humate (HA-K, carbon resource) and mild activating agent potassium acetate (CH₃COOK). Microstructure characterizations indicate that the introduction of activating agent CH₃COOK is a key step to achieve high specific surface area and carbonization degree. These ACs contain small amount of oxygen and nitrogen, and show obvious pseudo-capacitance besides double layer capacitance. As a result, the optimized ACs achieve high specific capacitances of 311F$\cdot$g${}^{-1}$ and 317F$\cdot$g${}^{-1}$ at 0.1A$\cdot$g${}^{-1}$ in 2M KOH and 1M H₂SO₄ aqueous electrolytes, respectively. This sample also shows a good charge-discharge cycling stability within 10 000 cycles.

We here report a superconcentrated potassium acetate (KAC) solution (75wt.%, K : H₂O $=$ 1 : 1.8, called as “water-in-salt”) as an aqueous electrolyte to improve the working voltage and increasing capacitance in enhancing the energy density of the active carbon-based aqueous supercapacitor. The stability potential window of the superconcentrated electrolyte realizes an AC//AC symmetric supercapacitor with operating voltage of 2.0 V and excellent cyclic performance. Meanwhile, the energy density of such supercapacitor achieves about twice as high as that of the supercapacitor using normal concentration of electrolyte.