ENHANCED BREAKDOWN VOLTAGE ELECTRODE
Particles of active electrode material are made by blending and fibrillizing (i.e., fibrillating) a mixture of activated carbon, conductive carbon, and fibrillizable binder. In selected embodiments, chloride level in the activated carbon is relatively low, a small amount of conductive carbon with low impurity levels and high conductivity is used, and the binder is inert. For example, chloride content of the activated carbon is below 50 ppm, and total impurities in the conductive carbon are below 120 ppm. The mixture may include about 10% of PTFE and 0.5% or less of conductive carbon. Blending and fibrillization may be performed without solvents. The fibrillized particles are dried, blended again to reduce clumping, and used to make active electrode material film. The film is attached to a current collector to obtain an electrode for use in various electrical devices, including double layer capacitors. The electrode increases breakdown voltage of the capacitor electrolyte.
1 . A method of making particles of active electrode material, the method comprising:
providing activated carbon with chloride content not exceeding about 50 parts per million;
providing binder;
mixing the activated carbon and the binder to obtain a mixture; and
fibrillizing the binder in the mixture.
2 . A method in accordance with claim 1 , further comprising providing conductive particles.
3 . A method in accordance with claim 2 , wherein proportion of the conductive carbon particles in the mixture does not exceed about 0.5 percent by weight.
4 . A method in accordance with claim 1 , wherein the binder comprises PTFE; and wherein the proportion of the binder in the mixture is about 10 percent by weight.
5 . A method in accordance with claim 2 , wherein the proportion of the conductive carbon particles in the mixture is between 0.1 percent and 1 percent by weight; and wherein the proportion of binder in the mixture is between 9 and 11 percent by weight.
6 . A method in accordance with claim 2 , wherein the step of mixing comprises dry blending the activated carbon, conductive carbon, and the binder.
7 . A method in accordance with claim 1 , wherein the step of fibrillizing is performed without processing additives.
8 . A method of making particles of active electrode material, the method comprising:
providing activated carbon with chloride content not exceeding about 50 parts per million;
providing low contamination level conductive particles;
providing fibril-forming binder;
mixing the activated carbon, the conductive carbon, and the binder to obtain a mixture; and
fibrillizing the mixture.
9 . A method in accordance with claim 8 , wherein proportion of the conductive carbon particles in the mixture does not exceed about 0.5 percent by weight.
10 . A method in accordance with claim 9 , wherein proportion of the binder in the mixture is about 10 percent by weight.
11 . A method in accordance with claim 9 , wherein proportion of binder in the mixture is between 9 and 11 percent by weight.
12 . A method in accordance with claim 8 wherein the step of providing activated carbon comprises providing activated carbon with chloride content less than about 30 parts per million.