Monolithic electrode for electric double-layer capacitors based on macro/meso/microporous S-Containing activated carbon with high surface area

Abstract

Macro/meso/microporous carbon monoliths doped with sulfur have been prepared from sulfonated poly(divinylbenzene) networks followed by the activation with CO 2 resulted in the activated carbon monoliths with high surface area of 2400 m 2 g 1 . The monolithic electrode of the activated carbon shows remarkably high specific capacitance (175 F g 1 at 5 mV s 1 and 206 F g 1 at 0.5 A g 1 ).Increasing demands for the electrochemical devices, such as batteries, 1 fuel cells, 2 and electric double-layer 5 capacitors (EDLCs), 3-6 has triggered the development of porous carbon materials. The physical properties of carbon materials, including surface area, pore volume and pore size, must be controlled to be suitable for each application, because they are closely related to the electrochemical performance. A practical polarized electrode material for EDLCs is activated carbon with a high specific surface area 7-9 because EDLCs are based on electrostatic interactions, i.e. the electric charge is accumulated on an electric double-layer of the polarized electrode, and the electrodes with 10 the higher specific surface area can store higher energy. However, the conventional electrodes consisting of microporous carbon particles or powders are not effective enough because the narrow and disordered pores inbetween particles or powders are not suitable for the effective transport of ions to the micropore surfaces. In other words, a certain portion of micropores are inaccessible for ions and remain unused. For the better capacitive characteristics, therefore, it is indispensable for porous carbons to have the well-defined larger pores (mesopores and 15 macropores) in addition to the micropores. The mesopores and macropores facilitate the diffusion of the electrolyte ions in the materials while the micropores can provide abundant adsorbing sites for ions. 7,10,11 Thus, great efforts are focused on the preparation of macro/microporous, meso/microporous, and macro/meso/microporous hierarchically porous carbons for EDLCs. [12][13][14][15][16][17][18][19][20][21] Monolithic porous carbons are more advantageous for EDLCs rather than the traditional composite pellet electrodes, since the pellet electrodes are fabricated using a mixture of activated carbon 20 powders and binders, such as polytetrafluoroethylene (PTFE), which lower the electric conductivity, and the electrodes are possibly broken into fragments during the charge-discharge cycles. In addition, there is a possibility

The contribution of sulfate ions and protons to the specific capacitance of microporous carbon monoliths

“…Like other carbons, the carbon monoliths can be doped with heteroatoms (oxygen, nitrogen, phosphorus, sulfur,…), the doping giving rise to an increase of the specific capacitance or to a broadening of the working voltage window [33][34][35][36][37][38]. The high electrical conductivity makes carbon monoliths suitable substrates for depositing other active electrode materials such as polymers [39] or oxides [40,41].…”

Aromatic sulfide, sulfoxide, and sulfone mediated mesoporous carbon monolith for use in supercapacitor

“…Sulfur shares the chalcogen group with oxygen, and the functionalization with sulfur containing groups is expected to be an important way to tune carbon chemistry. Sulfur containing functional groups allow to mediate carbon chemistry in different ways depending on their oxidation states [5], and show potential applications in biomass conversion [3], heavy metal recovery [6], and supercapacitor [7]. Usually, when the carbon materials or their precursors react with H 2 SO 4 , sulfonate will be grafted on the surface [3].…”

Nitrogen- and phosphorus-co-doped carbons with tunable enhanced surface areas promoted by the doping additives

“…Although other heteroatoms are of thriving interest, synthetic pathways towards boron-, [23][24][25][26] sulphur- [27][28][29][30][31][32][33][34][35] and phosphorus-doped [36][37][38] carbons are still rare. As especially bigger atoms like S or P have most preferable effects on the polarisability of the carbon materials and thus on their performance in electrochemical applications, [31][32][33][34][35][36] new synthesis routes are inevitable. IL based syntheses of carbon materials have been established in manifold ways in recent years of research.…”