Low-internal-resistance lithium capacitor electrolyte and electrolyte additive

Abstract

The invention relates to a key technology of a lithium ion capacitor electrolyte and an electrolyte additive. The electrochemical performance of the lithium ion capacitor electrolyte can be effectively improved. The invention mainly relates to an electrolyte additive prepared from lithium halide, diatomite, graphite powder, urethane acrylate and an acrylic monomer, and a mixed electrolyte prepared from the additive and a common electrolyte containing lithium hexafluorophosphate, ethylene carbonate and dimethyl carbonate. The lithium capacitor electrolyte additive can effectively reduce the internal resistance of the electrolyte, and the cycle capacity and retention rate of the lithium capacitor can be effectively improved by adopting the electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitors, and in particular relates to a lithium capacitor electrolyte additive and an electrolyte. Background Art

[0002] Lithium capacitor electrolytes are the carriers of ion transport within the capacitor. They are typically composed of lithium salts and organic solvents. The electrolyte conducts ions between the positive and negative electrodes of lithium-ion capacitors, ensuring their high voltage and high specific energy. Electrolytes are typically formulated under specific conditions and in specific proportions using a combination of high-purity organic solvents (such as ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate), electrolyte lithium salts (such as lithium hexafluorophosphate, lithium perchlorate, and lithium tetrafluoroborate), and necessary additives (such as film-forming additives, conductive additives, flame retardants, overcharge protection additives, additives to control the water and HF content of the electrolyte, additives to improve low-temperature performance, and multifunctional additives). Summary of the Invention

[0003] The present invention provides a lithium capacitor electrolyte additive, which can effectively reduce the internal resistance of the electrolyte and improve the cycle capacity and retention rate of the lithium capacitor.

[0004] A second object of the present invention is to provide a lithium capacitor electrolyte.

[0005] The lithium capacitor electrolyte additive of the present invention adopts the following technical solution: a lithium capacitor electrolyte additive, the additive is prepared according to the following method: (1) Mix polyurethane acrylate and acrylic monomer evenly; (2) adding paraffin wax and diatomaceous earth to the mixture obtained by the treatment in step (1) and mixing them uniformly; (3) adding 2,2-dimethoxy-2-phenylacetophenone and graphite powder to the mixture obtained by the treatment in step (2), mixing them evenly and then granulating them; (4) adding the lithium halide-diatomaceous earth-graphite mixture to the product obtained after treatment in step (3) and mixing them uniformly; (5) Curing under ultraviolet light to obtain the lithium capacitor electrolyte additive.

[0006] As a further preferred technical solution, the lithium halide-diatomaceous earth-graphite mixture in step (4) is prepared by uniformly mixing lithium halide, diatomaceous earth and graphite powder and then grinding them.

[0007] As a further preferred technical solution, the lithium halide is lithium bromide.

[0008] The lithium capacitor electrolyte of the present invention adopts the following technical solution: a lithium capacitor electrolyte, comprising the lithium capacitor electrolyte additive as described in any one of the above.

[0009] As a further preferred technical solution, lithium hexafluorophosphate, ethylene carbonate and dimethyl carbonate are also included.

[0010] As a further preferred technical solution, the final concentration of the lithium capacitor electrolyte additive is 0.2-2wt%.

[0011] The lithium halide-diatomaceous earth-graphite mixture in the lithium capacitor electrolyte additive of the present invention is prepared by uniformly mixing lithium halide, diatomaceous earth and graphite powder and then grinding them. The lithium halide, diatomaceous earth and graphite powder are homogenized during the grinding process. Compared with the lithium halide-diatomaceous earth-graphite mixture prepared by grinding them separately and then mixing them, the effect of improving the capacitor cycle capacity is better.

[0012] The lithium halide in the lithium halide-diatomaceous earth-graphite mixture in the lithium capacitor electrolyte additive of the present invention is preferably lithium bromide, which has a better effect on improving the capacitor cycle capacity. DETAILED DESCRIPTION

[0013] 1. Preparation of the Lithium Capacitor Electrolyte Additive of the Present Invention Example

[0014] Preparation of lithium capacitor electrolyte additive: (1) polyurethane acrylate and acrylic acid monomer are mixed in a mass ratio of 1:1; (2) 5% paraffin and 2% diatomaceous earth are added to the mixture of step (1) and mixed evenly; (3) 2,2-dimethoxy-2-phenylacetophenone (3% of the total mass of polyurethane acrylate and acrylic acid monomer) and 0.1% graphite powder are added to the mixture obtained by step (2), mixed evenly and granulated; (4) 1% lithium halide-diatomaceous earth-graphite mixture is added to the product obtained by step (3) and mixed evenly (so that the lithium halide-diatomaceous earth-graphite mixture adheres to the surface of the particles); (5) solidified under ultraviolet light to obtain lithium capacitor electrolyte additive.

[0015] Wherein: (1) The amount of each of the above raw materials is calculated based on the total mass of polyurethane acrylate and acrylic monomer; (2) The above steps (1)-(4) are all carried out under light-proof conditions, and steps (3)-(4) should be completed in the shortest possible time; (3) A lithium halide-diatomaceous earth-graphite mixture was prepared by uniformly mixing lithium bromide, diatomaceous earth, and graphite powder to obtain a mixture of the three, and then grinding the mixture to a particle size of 10 μm to obtain a lithium halide-diatomaceous earth-graphite mixture. The mass ratio of lithium bromide, diatomaceous earth, and graphite powder was 1:4:3. Example

[0016] Preparation of lithium capacitor electrolyte additive: (1) polyurethane acrylate and acrylic acid monomer are mixed uniformly in a mass ratio of 1:1; (2) 3% paraffin wax and 0.5% diatomaceous earth are added to the mixture of step (1) and mixed uniformly; (3) 2,2-dimethoxy-2-phenylacetophenone (4% of the total mass of polyurethane acrylate and acrylic acid monomer) and 0.5% graphite powder are added to the mixture obtained by step (2), mixed uniformly and granulated; (4) 0.5% lithium halide-diatomaceous earth-graphite mixture is added to the product obtained by step (3) and mixed uniformly (so that the lithium halide-diatomaceous earth-graphite mixture adheres to the surface of the particles); (5) solidified under ultraviolet light to obtain lithium capacitor electrolyte additive.

[0017] Wherein: (1) The amount of each of the above raw materials is calculated based on the total mass of polyurethane acrylate and acrylic monomer; (2) The above steps (1)-(4) are all carried out under light-proof conditions, and steps (3)-(4) should be completed in the shortest possible time; (3) A lithium halide-diatomaceous earth-graphite mixture was prepared by uniformly mixing lithium bromide, diatomaceous earth, and graphite powder to obtain a mixture of the three, and then grinding the mixture to a particle size of 50 μm to obtain a lithium halide-diatomaceous earth-graphite mixture. The mass ratio of lithium bromide, diatomaceous earth, and graphite powder was 1:3:2.

[0018] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that, when preparing the lithium halide-diatomaceous earth-graphite mixture, lithium bromide, diatomaceous earth and graphite powder are ground to a particle size of 10 μm and then mixed uniformly. The rest is consistent with Example 1.

[0019] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the 2,2-dimethoxy-2-phenylacetophenone and graphite powder added in step (3) are replaced by 2,2-dimethoxy-2-phenylacetophenone, and the lithium halide-diatomaceous earth-graphite mixture added in step (4) is replaced by a lithium halide-diatomaceous earth mixture; the rest are consistent with Example 1.

[0020] 2. Preparation of lithium capacitor electrolyte.

[0021] (1) Lithium capacitor electrolyte: Ethylene carbonate and dimethyl carbonate are mixed evenly in a volume ratio of 1:1; lithium hexafluorophosphate is added to make the concentration of lithium hexafluorophosphate 1 mol / L to obtain a lithium capacitor basic electrolyte.

[0022] (2) Take 4 portions (equal amounts) of the lithium capacitor base electrolyte prepared in step (1), and add the lithium capacitor electrolyte additives prepared in Examples 1-4 respectively, so that the final concentration of the lithium capacitor electrolyte additive is 1 wt%, to obtain lithium capacitor electrolytes 1-4 respectively.

[0023] (3) Take 5 parts of the lithium capacitor basic electrolyte prepared in step (1) (equal amounts), and add the lithium capacitor electrolyte additives prepared in Comparative Example 1, Example 5, Example 6, Example 7, and Comparative Example 2, respectively, so that the final concentration of the lithium capacitor electrolyte additive is 1 wt%, to obtain lithium capacitor electrolytes 5-9, respectively.

[0024] (4) Take 4 portions (equal amounts) of the lithium capacitor base electrolyte prepared in step (1), add the lithium capacitor electrolyte additive prepared in Example 1, respectively, so that the final concentrations of the lithium capacitor electrolyte additive are 0.2 wt%, 0.8 wt%, 1.5 wt%, and 2 wt%, respectively, to obtain lithium capacitor electrolytes 10-13, respectively.

[0025] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A low internal resistance lithium capacitor electrolyte and electrolyte additive, characterized in that: The additive in the electrolyte is prepared according to the following method: (1) Mix polyurethane acrylate and acrylic monomer evenly; (2) adding paraffin wax and diatomaceous earth to the mixture obtained by the treatment in step (1) and mixing them uniformly; (3) adding 2,2-dimethoxy-2-phenylacetophenone and graphite powder to the mixture obtained by the treatment in step (2), mixing them evenly and then granulating them; (4) adding the lithium halide-diatomaceous earth-graphite mixture to the product obtained after treatment in step (3) and mixing them uniformly; (5) Curing under ultraviolet light to obtain the lithium capacitor electrolyte additive.

2. The lithium capacitor electrolyte additive according to claim 1, characterized in that The lithium halide-diatomaceous earth-graphite mixture in step (4) is prepared by uniformly mixing lithium halide, diatomaceous earth and graphite powder and then grinding them.

3. The lithium capacitor electrolyte additive according to claim 2, characterized in that The amount of the lithium halide-diatomaceous earth-graphite mixture in step (4) is 0.5-1.5% of the total mass of the polyurethane acrylate and acrylic acid monomer; the mass ratio of the lithium halide, diatomaceous earth and graphite powder is 1:(3-5):(2-4), and the particle size of the lithium halide-diatomaceous earth-graphite mixture is 10-50 μm.

4. The lithium capacitor electrolyte additive according to claim 1, characterized in that The mass ratio of the polyurethane acrylate to the acrylic acid monomer is 1:1, and the amount of the 2,2-dimethoxy-2-phenylacetophenone is 3%-5% of the total mass of the polyurethane acrylate and the acrylic acid monomer.

5. The lithium capacitor electrolyte additive according to claim 1, characterized in that The amount of paraffin wax used in step (2) is 3-8% of the total mass of the polyurethane acrylate and acrylic acid monomer; the amount of diatomaceous earth used in step (2) is 0.5-2% of the total mass of the polyurethane acrylate and acrylic acid monomer; and the amount of graphite powder used in step (3) is 0.03-0.5% of the total mass of the polyurethane acrylate and acrylic acid monomer.

6. The lithium capacitor electrolyte additive according to any one of claims 1 to 5, characterized in that: The lithium halide is lithium bromide.

7. A lithium capacitor electrolyte, characterized in that: The invention comprises the lithium capacitor electrolyte additive according to any one of claims 1 to 6.

8. The lithium capacitor electrolyte according to claim 7, characterized in that Also included are lithium hexafluorophosphate, ethylene carbonate, and dimethyl carbonate.

9. The lithium capacitor electrolyte according to claim 7 or 8, characterized in that: The final concentration of the lithium capacitor electrolyte additive is 0.2-2 wt %.