For their use in supercapacitors, aqueous electrolytes of acidic (H 2 SO 4 ), neutral (Na 2 SO 4 , K 2 SO 4 ) and basic (NaOH, KOH) nature are studied, using two microporous binder-free and self-standing carbon cloths as electrodes. The carbon cloths show similar porosities and specific surface areas, but different contents in surface oxygen groups. The working potential window and the specific capacitance associated with the cations and anions are measured. From these parameters, the charges stored by the cations and anions at the electric electrolyte/electrode interface are deduced. The charge stored by the cations is higher than that stored by the anions for the three types of electrolytes. The differences between cations and anions are higher for the acidic and basic electrolyte than for the neutral electrolytes, and also higher for the carbon cloth with the highest content in surface oxygen groups. The charge stored by the cations follows the sequence H 3 O + > Na + or K + from the basic electrolytes > Na + or K + from the neutral electrolytes. The charge stored by the anions follows the sequence SO 4 2-The results here reported provide a better understanding on the electric double layer of carbon-based supercapacitors. Those results are also of interest for asymmetric and hybrid supercapacitors.

This paper provides a procedure for evaluating the capacity or charge of composites consisting of battery-type electrode and supercapacitor-type one. The composites, which are binder-free flexible materials, consist of cobalt oxide (CoO x) electrodeposited on the fibers of a carbon cloth (CC). The deposited CoO x shows battery-type response. The CC substrate shows supercapacitor-type one. The procedure here reported is based on galvanostatic charge/discharge measurements. It is easier, less laborious and faster than the procedure based on the kinetic study by cyclic voltammetry. The two procedures are compared. The dependences of the specific capacities as functions of the current density and voltage scan rate show similar patterns. The contribution of the two types of materials to the specific capacity of the complete electrode is discussed. The electrodedeposited CoO x contributes increasing the specific capacity of the composites at low current densities. The CC substrate dominates the specific capacity of the composites at high current densities.

Mn oxide and/or Co oxide are deposited on flexible carbon cloth by a cathodic potentiodynamic procedure from their respective sulfates. In KOH electrolyte, the charge stored from reversible redox reactions of the two oxides (battery response) overlaps with the charge stored from the double layer of the carbon cloth (supercapacitor response). These charges or capacities are compared. For the electrodes having one oxide only, either Mn or Co oxide, the highest capacity is obtained for 8 wt% oxide load. To overcome this limitation, both Mn and Co oxide are simultaneously or sequentially electrodeposited on carbon cloth over a broad compositional range. The electrode capacity can reach 71 mA · h · g −1 or 0.9 mA · h · cm −2 , which are higher than the values found for the bare carbon cloth. The electrode capacity depends on the relative content of the carbon cloth and the two deposited oxides according to the rule of mixtures. The decrease of the specific surface area of the carbon cloth is discussed in relation to the deposited oxide. The high capacity retention vs current is due to the contribution of the carbon cloth substrate. The electrode cycle life is discussed on the basis of the supercapacitor response and battery one.