Electrical double layer capacitor with enhanced working voltage
The present invention relates to the method of increasing the working voltage of electrical double layer capacitor with enhanced working voltage, which has electrodes fabricated from porous carbon powder in which the pore sizes and the specific surface are created by extracting the non-carbon atoms from the carbon-rich organic or mineral compounds. The method is performed by step-by-step treatment of supercapacitor with the conditioning voltage (Uc), which is increased gradually up to the working voltage (Uw) by the voltage step (DUc) which is less or equal to 0.2V.
1. A method of conditioning a supercapacitor to its working voltage, wherein the supercapacitor comprising at least one pair of positively and negatively charged electrodes, including at least one polarisable micro/mesoporous carbon electrode, interleaved with porous ion-conductive separator and immersed in an electrolyte, wherein a destructive effect of heat of adsorption is suppressed by a multistep conditioning process, wherein before the conditioning of the supercapacitor, a supercapacitor cell is stored after filling with the electrolyte for penetration of micropores by electrolyte followed by step-by-step treatment of the supercapacitor with a conditioning voltage (Uc), which is increased gradually up to the working voltage (Uw) by voltage step (ΔUc) which is less than 0.3V, wherein during the conditioning step is performed the voltage cycling wherein the supercapacitor is charged to the conditioning voltage (Uc) and thereafter discharged to the voltage Uc-ΔU wherein the ΔU is between 0 and Uc.
2. The method according to the claim 1 wherein a number of the conditioning steps is predetermined by voltage step (ΔUc) so that the supercapacitor working voltage is reached.
3. The method according to claim 1 wherein the supercapacitor before treatment by conditioning voltage (Uc) is electrochemically stabilised by galvanostatic cycling at Uc of less than 3.0V until stable performance according to ESR and capacitance is obtained.
4. The method according to claim 1 wherein a micro/mesoporous carbon of the micro/mesoporous carbon electrode is carbide-derived carbon.
5. The method according to claim 1 wherein a micro/mesoporous carbon of the micro/mesoporous carbon electrode is coconut shell derived activated carbon.
6. The method according to claim 1 wherein a micro/mesoporous carbon of the micro/mesoporous carbon electrode is phenolic resin derived activated carbon.
7. The method according to the claim 1 wherein the electrolyte used for immersion of the micro/mesoporous carbon electrode is an electrolyte salt and a solvent selected from the group consisting of acetonitrile, acrylonitrile, propionitrile, dimethyl sulfoxide, diethyl sulfoxide, ethyl methyl sulfoxide, benzylmethyl sulfoxide, dimethyl formamide, N-methylpyrrolidone, cyclic ester, chain carbonate, cyclic carbonate, chain ether, cyclic ether solvent, and mixtures thereof.
8. The method according to the claim 1 wherein before conditioning the supercapacitor, the supecapacitor cell is stored after filling with the electrolyte at the temperature which is higher than a room temperature for penetration of micropores by electrolyte.
9. The method according to the claim 7 , wherein the electrolyte salt is selected from the group consisting of tetrafluoroborates of tetraalkylammonium, hexafluorophosphates of tetraalkylammonium, trifluoromethanesulfonate of tetraalkylammonium, tetrakis(dialkylamino) phosphonium, N,N-dialkyl-1,4-diazabicyclo[2.2.2]octanediium, and mixtures thereof.
10. The method according to the claim 1 , wherein the electrolyte used for immersion of the micro/mesoporous carbon electrode comprises at least one ionic liquid selected from the group consisting of butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-methyl-3-propylimidazolium iodide, 1-ethyl-3-methylimidazolium thiocyanate, 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide, 1-butyl-2-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-butyl-4-methylpyridinium bi s(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, diethylmethylsulfonium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide.