Manufacturing method for lithium-ion capacitors

Abstract

To provide a manufacturing method of a lithium ion capacitor for solving a problem that a manufacturing cost of the lithium ion capacitor is high.SOLUTION: A manufacturing method of a lithium ion capacitor, contains: a positive electrode manufacturing step of manufacturing a positive electrode sheet by mixing a high-lithium material, an active carbon, a conductive assistant, and an aqueous adhesive agent to obtain a slurry by adding water as a solvent, and thereafter manufacturing a positive electrode sheet by coating them to a carbon coating aluminum foil; a negative electrode manufacturing step of mixing a negative electrode material, the conductive assistant, and the aqueous adhesive agent to form the slurry by adding water as a solvent, and thereafter, manufacturing a negative electrode sheet by coating them to a copper foil; and an assembling step of assembling the positive electrode sheet, the negative electrode sheet, an electrolyte, and a separator to which lithiation is not made to the capacitor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a lithium ion capacitor, and particularly to a method for manufacturing a lithium ion capacitor that uses water as a solvent. [Background Art]

[0002] A lithium ion capacitor is a capacitor with high energy density and high safety. The positive electrode of the lithium ion capacitor adopts an electrode formulation based on activated carbon, which is the same as that of supercapacitors, while the negative electrode adopts negative electrode materials commonly used in general batteries such as graphite, soft carbon and hard carbon. Accordingly, the lithium ion capacitor simultaneously has the rapid charge-discharge characteristics of supercapacitors and the high energy density characteristics of lithium batteries.

[0003] When manufacturing a lithium ion capacitor using the negative electrode of a conventional general battery, it is necessary to perform a pre-lithiation process using lithium metal. The pre-lithiation process requires expensive equipment and a strictly controlled environment, and an organic solvent must be used in the process to produce the electrode, so the manufacturing cost of lithium ion capacitors remains high.

[0004] Therefore, in order to reduce the manufacturing cost of lithium ion capacitors, there is a need in the industry for a lithium ion capacitor that can reduce material costs and production environment requirements. [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Therefore, an object of the present invention is to provide a method for manufacturing a lithium ion capacitor to solve the problem of high manufacturing cost of conventional lithium ion capacitors. [Means for Solving the Problem]

[0006] To solve the problems of the prior art, the present invention provides a method for manufacturing a lithium-ion capacitor, characterized by including a positive electrode manufacturing step of mixing a high-lithium material, activated carbon, a conductive additive, and an aqueous adhesive, adding water as a solvent to make a slurry, and then applying it to carbon-coated aluminum foil to manufacture a positive electrode sheet; a negative electrode manufacturing step of mixing a negative electrode material, a conductive additive, and an aqueous adhesive, adding water as a solvent to make a slurry, and then applying it to copper foil to manufacture a negative electrode sheet; and an assembly step of assembling the pre-lithified positive electrode sheet, the negative electrode sheet, an electrolyte, and a separator into a capacitor.

[0007] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized in that the high-lithium material is lithium manganese oxide or lithium oxalate.

[0008] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized in that the activated carbon is activated carbon for supercapacitors, porous carbon, or high surface area carbon black.

[0009] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized in that the conductive additive is conductive carbon black or general carbon black.

[0010] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized in that the negative electrode material is graphite, soft carbon, or hard carbon.

[0011] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized in that an electrolyte for lithium batteries is used as the electrolyte.

[0012] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, characterized by using a plastic diaphragm, a cellulose diaphragm, or a glass fiber diaphragm as a separator.

[0013] One embodiment of the present invention provides a method for manufacturing a lithium-ion capacitor, further comprising an activation step of activating the capacitor with a charging speed of 0.1 to 0.5 mV / second and a voltage of 2.2 to 3.8 V. [Effects of the Invention]

[0014] According to the technical means of the present invention, by mixing a high-lithium material such as lithium manganese oxide (LMO) as a lithium source with the positive electrode material and manufacturing a coating slurry using water as a solvent, and also manufacturing a coating slurry using water as a solvent in the manufacturing of the negative electrode, it is possible to reduce the processing costs that would otherwise be incurred by the conventional pre-lithification process in which the negative electrode sheet of a lithium-ion capacitor reacts with lithium metal before assembling it with the positive electrode sheet and lithium-ion capacitor. Furthermore, since it can be applied to current battery manufacturing technology, there is no need to develop new equipment, and the manufacturing cost of lithium-ion capacitors can be further reduced. [Modes for carrying out the invention]

[0015] The following describes embodiments of the present invention. This description is merely an example of one embodiment of the present invention and does not limit the embodiments of the present invention.

[0016] According to the present invention's method for manufacturing a lithium-ion capacitor, an electrode sheet is manufactured using water as a solvent, and 1000m 2 A high-surface-area carbon material of 1 / g or more is mixed with a small amount of LMO material as a lithium source, and then mixed with a conductive additive, an aqueous adhesive, and water to make a slurry. This slurry is then applied to carbon-coated aluminum foil to manufacture a positive electrode sheet.

[0017] In addition, a negative electrode material such as artificial graphite, soft carbon, or hard carbon is mixed with a conductive additive, and similarly, water is used as a solvent and mixed with an aqueous adhesive to create a slurry, which is then applied to copper foil to manufacture a negative electrode sheet.

[0018] The manufactured positive electrode sheet, negative electrode sheet, separator, and electrolyte are assembled into a lithium-ion capacitor, and then tested after an activation process.

[0019] (Example 1) According to one embodiment of the present invention, a method for manufacturing a lithium-ion capacitor involves pre-mixing activated carbon, conductive carbon black, and high-lithium LMO in a ratio of 5:1:1 to obtain an active material. Then, an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is added as a solvent. The ratio of activated carbon:conductive carbon black:LMO:adhesive:water is 5:1:1:7:14. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, applied to a 16 μm thick carbon-coated aluminum foil with a 200 μm scraper, and moisture is removed using an oven at 110°C to obtain a positive electrode sheet.

[0020] Next, soft carbon and conductive carbon black are pre-mixed in a 10:1 ratio to obtain the active material. Then, an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is added as a solvent. The ratio of soft carbon:conductive carbon black:adhesive:water is 10:1:11:32. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, applied to an 8 μm thick copper foil with a 50 μm scraper, and the moisture is removed using an oven at 110°C to obtain the negative electrode sheet.

[0021] Next, use 1M of LiPF6 / (EC / DEC) as the electrolyte, a plastic diaphragm as the separator, and assemble the button capacitor in the following order: top cover, positive electrode sheet, separator, negative electrode sheet, spring plate, and bottom cover.

[0022] (Example 2) According to the method for manufacturing a lithium ion capacitor in one embodiment of the present invention, after activated carbon, conductive carbon black and LMO, which is a high-lithium material, are premixed at a ratio of 5:1:1 to obtain an active material, an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of activated carbon:conductive carbon black:LMO:adhesive:water is 5:1:1:7:14. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a carbon-coated aluminum foil with a thickness of 16 µm using a 200 µm scraper, and moisture is removed at 110°C using an oven to obtain a positive electrode sheet.

[0023] Next, after soft carbon and conductive carbon black are premixed at a ratio of 10:1 to obtain an active material, an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of soft carbon:conductive carbon black:adhesive:water is 10:1:11:32. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a copper foil with a thickness of 8 µm using a 50 µm scraper, and moisture is removed at 110°C using an oven to obtain a negative electrode sheet.

[0024] Next, with 1 M LiPF₆ / (EC / DEC) used as the electrolyte and a cellulose diaphragm used as the separator, a button capacitor is assembled in the order of an upper cover, the positive electrode sheet, the separator, the negative electrode sheet, a spring plate and a lower cover.

[0025] (Example 3) According to the method for manufacturing a lithium ion capacitor in one embodiment of the present invention, after activated carbon, conductive carbon black and LMO, which is a high-lithium material, are premixed at a ratio of 5:1:1 to obtain an active material, an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of activated carbon:conductive carbon black:LMO:adhesive:water is 5:1:1:7:14. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a carbon-coated aluminum foil with a thickness of 16 µm using a 200 µm scraper, and moisture is removed at 110°C using an oven to obtain a positive electrode sheet.

[0026] Next, soft carbon and conductive carbon black are pre-mixed at a ratio of 10:1 to obtain an active material, then an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of soft carbon: conductive carbon black: adhesive: water is 10:1:11:32. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a copper foil with a thickness of 8 µm using a 50 µm scraper, and moisture is removed at 110°C using an oven to obtain a negative electrode sheet.

[0027] Next, 1 M LiPF₆ / (EC / DEC) is used as the electrolyte, a glass fiber diaphragm is used as the separator, and a button capacitor is assembled in the order of an upper cover, a positive electrode sheet, the separator, a negative electrode sheet, a spring plate, and a lower cover.

[0028] (Comparative Example 1) Activated carbon and conductive carbon black are pre-mixed at a ratio of 5:1 to obtain an active material, then an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of activated carbon: conductive carbon black: adhesive: water is 5:1:1:20. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a carbon-coated aluminum foil with a thickness of 16 µm using a 200 µm scraper, and moisture is removed at 110°C using an oven to obtain a positive electrode sheet.

[0029] Next, soft carbon and conductive carbon black are pre-mixed at a ratio of 10:1 to obtain an active material, then an aqueous adhesive with a solid content of 5 wt% equal to the weight of the active material is added, and water is further added as a solvent. The ratio of soft carbon: conductive carbon black: adhesive: water is 10:1:11:32. Subsequently, the slurry is continuously ground using a ball mill at 300 rpm for 3 hours, coated onto a copper foil with a thickness of 8 µm using a 50 µm scraper, and moisture is removed at 110°C using an oven to obtain a negative electrode sheet.

[0030] Next, use 1M of LiPF6 / (EC / DEC) as the electrolyte, a plastic diaphragm as the separator, and assemble the button capacitor in the following order: top cover, positive electrode sheet, separator, negative electrode sheet, spring plate, and bottom cover.

[0031] The button capacitors of Examples 1-3 and Comparative Example 1 were activated for 5 cycles at a current density of 0.01 A / g and 2.2-3.8 V. Then, the specific capacitance by weight, the energy density of the capacitors, and the energy density after 50,000 charge-discharge cycles at a current density of 0.5 were measured within the operating voltage range of 2.2-3.8 V. These results are shown in Table 1. Furthermore, because the energy density loss after charge-discharge was too large for Comparative Example 1, only the energy density value after 1,000 charge-discharge cycles is shown.

[0032] [Table 1]

[0033] As can be seen from Table 1, the capacitor of Comparative Example 1, which does not contain high-lithium material, has a capacitance-to-weight ratio of 135.27 F / g and an overall energy density of 46.55 Wh / kg in the operating voltage range of 2.2 to 3.8 V. After 1000 charge-discharge cycles at a current density of 0.5 A / g, it can only maintain a capacity of 3.23 Wh / kg.

[0034] In contrast, the capacitor of Example 1 achieved a capacitance-to-weight ratio of 166.84 F / g in the operating voltage range of 2.2 to 3.8 V, and a total energy density of 58.40 Wh / kg. Furthermore, it maintained an energy density of 39.16 Wh / kg after 50,000 charge-discharge cycles at a current density of 0.5 A / g.

[0035] The capacitor in Example 2 achieved a capacitance-to-weight ratio of 170.06 F / g in the operating voltage range of 2.2 to 3.8 V, and a total energy density of 59.74 Wh / kg. It maintained an energy density of 44.69 Wh / kg after 50,000 charge-discharge cycles at a current density of 0.5 A / g.

[0036] The capacitor in Example 3 achieved a capacitance-to-weight ratio of 175.35 F / g in the operating voltage range of 2.2 to 3.8 V, and a total energy density of 62.18 Wh / kg. It maintained an energy density of 31.74 Wh / kg after 50,000 charge-discharge cycles at a current density of 0.5 A / g.

[0037] As can be seen from the results, the capacitors of Examples 1 to 3 have high capacitance and a low rate of energy density loss after multiple discharge cycles, i.e., they have a long lifespan.

[0038] According to the technical means of the present invention, by mixing a high-lithium material such as lithium manganese oxide (LMO) as a lithium source with the positive electrode material and producing a coating slurry using water as a solvent, and also producing a coating slurry with water as a solvent for the negative electrode material, the processing cost that is required by conventional lithium-ion capacitors, which involves a pre-lithification treatment in which the negative electrode sheet reacts with lithium metal before assembling it with the positive electrode sheet and lithium-ion capacitor, can be reduced. This can be applied to current battery manufacturing technology, does not require the development of new equipment, and can reduce the manufacturing cost of lithium-ion capacitors.

[0039] While preferred embodiments of the present invention have been disclosed above, these do not limit the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the claims of the present invention should be interpreted broadly to include such changes and modifications.

Claims

1. A cathode manufacturing step involves mixing high-lithium material, activated carbon, a conductive additive, and an aqueous adhesive, adding water as a solvent to create a slurry, and then applying it to carbon-coated aluminum foil to manufacture a cathode sheet. The negative electrode manufacturing step involves mixing negative electrode material, a conductive additive, and an aqueous adhesive, adding water as a solvent to create a slurry, and then applying it to copper foil to manufacture a negative electrode sheet. A method for manufacturing a lithium-ion capacitor, characterized by including an assembly step of assembling the positive electrode sheet, the negative electrode sheet, the electrolyte, and the separator, which have not been pre-lithified, into a capacitor.

2. A method for manufacturing a lithium-ion capacitor according to claim 1, characterized in that the high-lithium material is lithium manganate or lithium oxalate.

3. A method for manufacturing a lithium-ion capacitor according to claim 1, characterized in that the negative electrode material is graphite, soft carbon, or hard carbon.

4. A method for manufacturing a lithium-ion capacitor according to claim 1, characterized in that an electrolyte for lithium batteries is used as the electrolyte.

5. A method for manufacturing a lithium-ion capacitor according to claim 1, characterized in that a plastic diaphragm, a cellulose diaphragm, or a glass fiber diaphragm is used as a separator.

6. A method for manufacturing a lithium-ion capacitor according to claim 1, further comprising an activation step of activating the capacitor with a charging speed of 0.1 to 0.5 mV / second and a voltage of 2.2 to 3.8 V.

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