Ultracapacitor with improved aging performance
An electric double layer capacitor contains first and second electrodes, each having respective first and second carbon materials with distinct pore size distributions. A pore volume ratio of the first carbon material is greater than a pore volume ratio of the second carbon material. The pore volume ratio R is defined as R=V 1 /V, where V 1 is a total volume of pores having a pore size of less than 1 nm, and V is a total volume of pores having a pore size greater than 1 nm.
1. An electric double layer capacitor comprising:
a first electrode comprising a first carbon material and a second electrode comprising a second carbon material, wherein
a pore volume ratio of the first carbon material is greater than a pore volume ratio of the second carbon material, such that the pore volume ratio of the first carbon material is between 2 and 3 and the pore volume ratio of the second carbon material is between 0.75 and 1, the pore volume ratio R being defined as R=V 1 /V, where V 1 is a total volume of pores having a pore size of less than 1 nm, and V is a total volume of pores having a pore size greater than 1 nm.
2. An electric double layer capacitor according to claim 1 , wherein the first electrode is a positive electrode and the second electrode is a negative electrode.
3. An electric double layer capacitor according to claim 1 , wherein the first electrode is a positive electrode, the second electrode is a negative electrode and a thickness of the negative electrode is greater than a thickness of the positive electrode.
4. An electric double layer capacitor according to claim 1 , wherein the first electrode is a positive electrode, the second electrode is a negative electrode and a thickness of the negative electrode is from 1 to 2 times a thickness of the positive electrode.
5. An electric double layer capacitor according to claim 1 , wherein V is a total volume of pores having a pore size between 1 nm and 10 nm.
6. An electric double layer capacitor according to claim 1 , wherein V is a total volume of pores having a pore size between 1 nm and 5 nm.
7. An electric double layer capacitor according to claim 1 , wherein V is a total volume of pores having a pore size between 1 nm and 2 nm.
8. An electric double layer capacitor according to claim 1 , wherein the first electrode comprises a mixture of the first carbon material, conductive carbon and binder, and the second electrode comprises a mixture of the second carbon material, conductive carbon and binder.
9. An electric double layer capacitor according to claim 1 , wherein the electric double layer capacitor further comprises an electrolyte solution comprising a salt dissolved in a solvent, where the salt is selected from the group consisting of organic acids, inorganic acids and ammonium salts.
10. An electric double layer capacitor according to claim 1 , wherein the electric double layer capacitor further comprises an electrolyte solution comprising tetraethyl ammonium tetrafluoroborate and acetonitrile.
11. A method of making an electric double layer capacitor comprising:
forming a first carbon-based electrode having a first carbon material;
forming a second carbon-based electrode having a second carbon material; and
incorporating the first and second carbon-based electrodes into an electric double layer capacitor, wherein
a pore volume ratio of the first carbon material is greater than a pore volume ratio of the second carbon material, such that the pore volume ratio of the first carbon material is between 2 and 3 and the pore volume ratio of the second carbon material is between 0.75 and 1, the pore volume ratio R being defined as R=V 1 /V, where V 1 is a total volume of pores having a pore size of less than 1 nm, and V is a total volume of pores having a pore size greater than 1 nm.