An electric double layer capacitor electrode, including: an activated carbon having: a pore volume utilization efficiency (PVUE) of from about 200 to 290 F/cm.sup.3, wherein PVUE is the ratio of the activated carbon gravimetric capacitance (F/g) to the pore volume (cm.sup.3/g) of the activated carbon; a low non-linearity value of from 0.1 to 5%; and a total pore volume of from 0.32 to 0.56 cm.sup.3/g. Also disclosed is a method of making an electric double layer capacitor electrode, and a method of characterizing the performance of activated carbon, and the electrode, in an electric double layer capacitor (EDLC) device, as defined, herein.

An ultracapacitor that is in contact with a hot atmosphere having a temperature of about 80° C. or more is provided. The ultracapacitor contains a first electrode, second electrode, separator, nonaqueous electrolyte, and housing is provided. The first electrode comprises a first current collector electrically coupled to a first carbonaceous coating and the second electrode comprises a second current collector electrically coupled to a second carbonaceous coating. The capacitor exhibits a capacitance value within the hot atmosphere of about 6 Farads per cubic centimeter or more as determined at a frequency of 120 Hz and without an applied voltage.

An ultracapacitor that is in contact with a hot atmosphere having a temperature of about 80° C. or more is provided. The ultracapacitor contains a first electrode, second electrode, separator, nonaqueous electrolyte, and housing is provided. The first electrode comprises a first current collector electrically coupled to a first carbonaceous coating and the second electrode comprises a second current collector electrically coupled to a second carbonaceous coating. The capacitor exhibits a capacitance value within the hot atmosphere of about 6 Farads per cubic centimeter or more as determined at a frequency of 120 Hz and without an applied voltage.

Systems and methods of charging and discharging an ultracapacitor are disclosed. In one embodiment, a circuit for charging a capacitor can include a power source configured to provide a source voltage. The circuit can further include an ultracapacitor, a temperature sensing device, a power converter, and one or more control devices configured to receive signals indicative of a temperature from the temperature sensing device, and to control operation of the power converter based at least in part on the one or more signals indicative of the temperature.

Systems and methods of charging and discharging an ultracapacitor are disclosed. In one embodiment, a circuit for charging a capacitor can include a power source configured to provide a source voltage. The circuit can further include an ultracapacitor, a temperature sensing device, a power converter, and one or more control devices configured to receive signals indicative of a temperature from the temperature sensing device, and to control operation of the power converter based at least in part on the one or more signals indicative of the temperature.

An ultracapacitor that comprises a first and second electrochemical cell that are connected in parallel is provided. The cells are define by a first electrode that contains a current collector having opposing sides coated with a carbonaceous material, a second electrode that contains a current collector having opposing sides coated with a carbonaceous material, and a separator positioned between the first electrode and the second electrode. The second cell is by the second electrode, a third electrode that contains a current collector having opposing sides coated with a carbonaceous material, and a separator positioned between the second electrode and the third electrode. The ultracapacitor also contains a nonaqueous electrolyte that is in ionic contact with the electrodes and contains a nonaqueous solvent and an ionic liquid. A package encloses the first cell, the second cell, and the nonaqueous electrolyte.

An ultracapacitor that comprises a first and second electrochemical cell that are connected in parallel is provided. The cells are define by a first electrode that contains a current collector having opposing sides coated with a carbonaceous material, a second electrode that contains a current collector having opposing sides coated with a carbonaceous material, and a separator positioned between the first electrode and the second electrode. The second cell is by the second electrode, a third electrode that contains a current collector having opposing sides coated with a carbonaceous material, and a separator positioned between the second electrode and the third electrode. The ultracapacitor also contains a nonaqueous electrolyte that is in ionic contact with the electrodes and contains a nonaqueous solvent and an ionic liquid. A package encloses the first cell, the second cell, and the nonaqueous electrolyte.

An ultracapacitor that contains a first electrode, second electrode, separator, nonaqueous electrolyte, and housing is provided. The first electrode comprises a first current collector electrically coupled to a first carbonaceous coating and the second electrode comprises a second current collector electrically coupled to a second carbonaceous coating. The nonaqueous electrolyte is in ionic contact with the first electrode and the second electrode, wherein the nonaqueous electrolyte contains an ionic liquid that is dissolved in a nonaqueous solvent at a concentration of about 1.0 mole per liter or more. The nonaqueous solvent has a boiling temperature of about 150° C. or more.

An ultracapacitor that contains a first electrode, second electrode, separator, nonaqueous electrolyte, and housing is provided. The first electrode comprises a first current collector electrically coupled to a first carbonaceous coating and the second electrode comprises a second current collector electrically coupled to a second carbonaceous coating. The nonaqueous electrolyte is in ionic contact with the first electrode and the second electrode, wherein the nonaqueous electrolyte contains an ionic liquid that is dissolved in a nonaqueous solvent at a concentration of about 1.0 mole per liter or more. The nonaqueous solvent has a boiling temperature of about 150° C. or more.

Capacitors having electrodes made of interconnected corrugated carbon-based networks (ICCNs) are disclosed. The ICCN electrodes have properties that include high surface area and high electrical conductivity. Moreover, the electrodes are fabricated into an interdigital planar geometry with dimensions that range down to a sub-micron scale. As such, micro-supercapacitors employing ICCN electrodes are fabricated on flexible substrates for realizing flexible electronics and on-chip applications that can be integrated with micro-electromechanical systems (MEMS) technology and complementary metal oxide semiconductor technology in a single chip. In addition, capacitors fabricated of ICCN electrodes that sandwich an ion porous separator realize relatively thin and flexible supercapacitors that provide compact and lightweight yet high density energy storage for scalable applications.