Secondary electrochemical cell and charging method
A secondary electrochemical cell includes a negative electrode including as an output conductor, a metallic or metal-coated open-pore form or a metallic or metal-coated nonwoven, as a carbon-based storage material that enables storage of electrical charge in the electrode through formation of an electrical double layer (Helmholtz double layer), activated carbon having a BET surface area of at least 800 m 2 /g, a non-carbon-based H2 storage material that can chemisorb hydrogen and/or store it as a metal hydride, a positive electrode including as an output conductor, a metallic or metal-coated open-pore form or a metallic or metal-coated nonwoven, and nickel hydroxide and/or nickel oxyhydroxide, a porous separator that separates the negative electrode and the positive electrode from one another, an aqueous alkaline electrolyte with which the electrodes and the separator are soaked, and a housing that encases the electrodes, the separator and the electrolyte.
1. A secondary electrochemical cell comprising:
a negative electrode comprising
an output conductor,
at least 5% by weight of a carbon-based storage material that enables storage of electrical charge in the electrode through formation of an electrical double layer (Helmholtz double layer), wherein the carbon-based storage material is activated carbon having a BET surface area of at least 800 m 2 /g, and
at least one non-carbon-based H2 storage material selected from the group consisting of AB 2 , AB 5 , A 2 B 7 and AB 3 alloys and can chemisorb hydrogen and/or store it as a metal hydride,
wherein the carbon-based storage material and the H2 storage material are homogenously distributed in the negative electrode,
a positive electrode containing
an output conductor, and
nickel hydroxide and/or nickel oxyhydroxide,
a porous separator that separates the negative electrode and the positive electrode from one another,
an aqueous alkaline electrolyte with which the electrodes and the separator are soaked, and
a housing that encases the electrodes, the separator and the electrolyte.
2. The secondary electrochemical cell as claimed in claim 1 , further comprising an auxiliary electrode electrically connected to the negative electrode to dissipate any oxygen pressure arising in the housing.
3. The secondary electrochemical cell as claimed in claim 1 , wherein the positive electrode has a lower capacity than the negative electrode.
4. The secondary electrochemical cell as claimed in claim 1 , wherein the housing has a gas- and liquid-tight configuration.
5. The secondary electrochemical cell as claimed in claim 1 , wherein the proportion of the H2 storage material in the negative electrode is 50% by weight to 95% by weight.
6. The secondary electrochemical cell as claimed in claim 1 , wherein the positive electrode contains the nickel hydroxide and/or nickel oxyhydroxide in a proportion of 10% by weight to 100% by weight.
7. The secondary electrochemical cell as claimed in claim 1 , wherein the carbon-based storage material and/or the H2 storage material are homogeneously distributed in the negative electrode.
8. The secondary electrochemical cell as claimed in claim 1 , wherein the negative electrode has a first subregion in which the carbon-based storage material is enriched, and a second subregion in which the H2 storage material is enriched.
9. The secondary electrochemical cell as claimed in claim 8 , wherein the carbon-based storage material has been applied to an exterior of the output conductor of the negative electrode.
10. The secondary electrochemical cell as claimed in claim 1 , wherein the positive electrode and/or negative electrode are layers having a thickness of 50 μm to 500 μm.
11. The secondary electrochemical cell as claimed in claim 1 , wherein the aqueous electrolyte contains a dissolved hydroxide compound in a proportion of 0.1 M to 10 M and optionally includes a sulfate compound in a concentration of 0.001% to 0.1% by weight.
12. A method of charging the electrochemical cell as claimed in claim 1 , wherein, during a charging operation, the ambient temperature and/or the temperature of the electrochemical element is measured and, upon exceeding a selected temperature threshold, the loading voltage is lowered by a value of 0.6 mV/° C. to 1.8 mV/° C.
13. The secondary electrochemical cell as claimed in claim 1 , wherein the output conductor of the negative electrode comprises a metallic or metal-coated open-pore foam, a metallic or metal-coated nonwoven, or a metal foil.
14. The secondary electrochemical cell as claimed in claim 1 , wherein the output conductor of the positive electrode comprises a metallic or metal-coated open-pore foam, a metallic or metal-coated nonwoven, or a metal foil.
15. A secondary electrochemical cell comprising:
a negative electrode comprising
an output conductor,
at least 5% by weight to 15% by weight of a carbon-based storage material that enables storage of electrical charge in the electrode through formation of an electrical double layer (Helmholtz double layer), wherein the carbon-based storage material is activated carbon having a BET surface area of at least 800 m 2 /g, and
at least one non-carbon-based H2 storage material selected from the group consisting of AB 2 AB 5 , A 2 B 7 and AB 3 alloys and can chemisorb hydrogen and/or store it as a metal hydride,
wherein the carbon-based storage material and the H2 storage material are homogenously distributed in the negative electrode,
a positive electrode containing
an output conductor, and
nickel hydroxide and/or nickel oxyhydroxide,
a porous separator that separates the negative electrode and the positive electrode from one another,
an aqueous alkaline electrolyte with which the electrodes and the separator are soaked, and
a housing that encases the electrodes, the separator and the electrolyte.
16. A secondary electrochemical cell comprising:
a negative electrode comprising
an output conductor,
at least 5% by weight of a carbon-based storage material that enables storage of electrical charge in the electrode through formation of an electrical double layer (Helmholtz double layer), wherein the carbon-based storage material is activated carbon having a BET surface area of at least 800 m 2 /g, and
a non-carbon-based H2 storage material that is an A 2 B 7 alloy and can chemisorb hydrogen and/or store it as a metal hydride,
a positive electrode containing
an output conductor, and
nickel hydroxide and/or nickel oxyhydroxide,
a porous separator that separates the negative electrode and the positive electrode from one another,
an aqueous alkaline electrolyte with which the electrodes and the separator are soaked, and
a housing that encases the electrodes, the separator and the electrolyte.