Bipyrrolidinium Tetrafluoroborate Research Articles

Activated carbon from phenolic resin with controlled mesoporosity for an electric double-layer capacitor (EDLC)

Activated carbon materials are prepared from phenolic resin precursors by physical activation to fabricate electrodes for electric double-layer capacitors (EDLCs). Pore size and surface area of the carbon materials are controlled during the synthesizing process and after the carbonization through activation in a CO2 atmosphere to different levels of burn-off. The resultant carbon materials were evaluated as EDLC electrodes, using electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD) measurements with the organic electrolyte of spiro-(1,1′)-bipyrrolidinium tetrafluoroborate in propylene carbonate, SBPBF4/PC. The results of the study showed that the capacitance of carbon materials, as well as energy density of the EDLC cells, increased by increasing the level of burn-off (activation). The 46% activated carbon gave a capacitance of ∼160 F g−1 and an energy density of ∼35 W h kg−1, at a current density of 1 mA cm−2. The long term cycling tests showed high cycling stability of these carbon materials.

Performance of Electrolyte Composed of Spiro-type Quaternary Ammonium Salt and Electric Double-layer Capacitor Using It

An electrolyte composed of a tetra-alkyl ammonium cation having a spiro structure (spiro-(1,1′)-bipyrrolidinium: SBP) showed excellent performance in terms of electric conductivity, viscosity, and solubility in various solvents, especially propylenecarbonate (PC). The electric double-layer capacitor (EDLC) using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate in PC (SBP-BF4/PC) has a performance better than that using tetraethylammonium tetrafluoroborate in PC (TEA-BF4/PC) and triethylmetylammonium tetrafluoroborate in PC (TEMA-BF4/PC), especially at low temperatures and high discharging rates.