High-heat-resistance antioxidant liquid for lithium battery copper foil

Abstract

The invention provides a high-heat-resistance antioxidant liquid for a lithium battery copper foil, which comprises hexavalent chromium and an organic matter containing heteroatoms, and the heteroatoms comprise N, O, S or P.

Description

Technical Field

[0001] The present invention relates to an antioxidant liquid for lithium battery copper foil, and more particularly to a high-heat-resistant antioxidant liquid for lithium battery copper foil. Background Art

[0002] Traditional lithium battery copper foil anti-oxidation treatment involves electroplating the copper foil in a hexavalent chromium solution, creating a passivation layer on the surface to prevent oxidation. Its heat-resistant temperature is approximately 150°C. To achieve temperatures above 210°C, nickel, zinc, or other metal elements are typically added to the chromium to form a heat-resistant composite metal layer.

[0003] With the booming development of applications such as electric vehicles, users are increasingly demanding higher performance from lithium batteries. To improve the safety of lithium batteries and prevent overcharging, which increases reactivity between the electrodes and the electrolyte, rapidly releasing heat, and leads to high-temperature oxidation of the copper foil, causing plate shedding, further lithium dendrite formation, separator rupture, and ultimately battery explosion, it is necessary to increase the heat resistance of copper foil.

[0004] However, conventional technology forms a composite metal anti-oxidation layer by adding multiple metal elements to the hexavalent chromium electroplating solution. Although this can increase the heat resistance temperature, the addition of excessive heavy metals not only increases costs and makes wastewater treatment more difficult, but also affects the battery performance of the copper foil.

[0005] Based on the above, a high heat-resistant antioxidant liquid for lithium battery copper foil has been developed, which can effectively increase the heat resistance temperature while solving the problems of increased costs and sewage treatment. This is a goal that technicians in this field are eager to develop. Summary of the Invention

[0006] The present invention provides a high-heat-resistant antioxidant liquid for lithium battery copper foil, which can effectively increase the heat-resistant temperature and solve the problems of cost increase and sewage treatment.

[0007] The antioxidant solution for lithium battery copper foil of the present invention comprises hexavalent chromium and organic matter containing heteroatoms, wherein the heteroatoms comprise N, O, S or P.

[0008] In one embodiment of the present invention, based on the total weight of the antioxidant solution for lithium battery copper foil, the content of hexavalent chromium is 50 ppm to 500 ppm, and the content of organic matter containing heteroatoms is 3000 ppm to 60000 ppm.

[0009] In one embodiment of the present invention, the source of hexavalent chromium includes chromium trioxide, chromate, and dichromate.

[0010] In one embodiment of the present invention, the organic compound containing heteroatoms includes benzotriazole, 2-thiolbenzoxazole, nitrogen-containing azoles, hydroxyethylene diphosphoric acid, aminotri(methylenephosphonic acid), sodium ethylenediaminetetramethylenephosphate, ethylenediaminetetraacetic acid, sodium gluconate, sodium potassium tartrate, or water-soluble siloxane.

[0011] In one embodiment of the present invention, the nitrogen-containing azole includes aminotriazole or aminotetrazolyl.

[0012] Based on the above, the present invention provides a high-heat-resistant antioxidant liquid for lithium battery copper foil. By adding organic matter containing heteroatoms, it forms coordination bonds with the vacant orbitals of copper, forming a dense antioxidant layer on the surface of the copper foil. This can prevent the copper foil from oxidative discoloration at high temperatures of 210°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Equivalent circuit diagram used for fitting. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are merely illustrative and the present invention is not limited thereto.

[0015] In this document, the term "range from one value to another value" is used as a summary to avoid listing all values ​​within the range. Therefore, a description of a specific numerical range encompasses any value within that range and any smaller numerical range defined by that value, just as if the value and smaller numerical range were listed in the specification.

[0016] The present invention provides a high-heat-resistant antioxidant solution for lithium battery copper foil, comprising hexavalent chromium and an organic compound containing heteroatoms, wherein the heteroatoms include nitrogen, oxygen, sulfur, or phosphorus. Based on the total weight of the antioxidant solution for lithium battery copper foil, the hexavalent chromium content is, for example, 50 ppm to 1500 ppm, and the content of the organic compound containing heteroatoms is, for example, 3000 ppm to 60,000 ppm.

[0017] In this embodiment, the source of hexavalent chromium may include chromium trioxide, chromate, and dichromate. The heteroatom-containing organic compound may include benzotriazole or its derivatives, 2-mercaptobenzoazole, nitrogen-containing azoles, hydroxyethylene diphosphoric acid, aminotri(methylenephosphonic acid), sodium ethylenediaminetetramethylenephosphate, ethylenediaminetetraacetic acid or its derivatives, sodium gluconate, sodium potassium tartrate, or water-soluble siloxane. The nitrogen-containing azoles may include aminotriazole or aminotetrazole.

[0018] The present invention also provides a high-heat-resistant, anti-oxidation treatment method for lithium battery copper foil, using the aforementioned high-heat-resistant, anti-oxidation solution for lithium battery copper foil, comprising the following steps. First, the raw electrolytic copper foil is washed and air-dried, then impregnated or electroplated with the high-heat-resistant, anti-oxidation solution of the present invention. The impregnation time is, for example, 1 to 20 seconds, and the electroplating conditions are, for example, 0.1 to 4 ASD. The foil is then squeezed out and air-dried before being wound up. In this embodiment, the thickness of the organic anti-oxidation layer formed on the surface of the copper foil is, for example, 10 to 300 nm. The organic anti-oxidation layer can be formed on two opposing surfaces of the copper foil.

[0019] After the copper foil has completed the antioxidant treatment, it is subjected to a heat resistance test. The copper foil is placed in a circulating oven at different temperatures and baked for 10 minutes. The highest temperature at which the color difference (ΔE) after baking does not exceed 8 is taken as its heat resistance temperature.

[0020] Color difference (ΔEab) is measured by using a spectrophotometer to measure the L, a, and b values ​​of the copper foil before and after baking, and is calculated using the following formula.

[0021]

[0022] The lithium battery copper foil treated with the formula of the present invention can be subjected to high temperatures of 180° C. to 250° C. without oxidative discoloration.

[0023] The following experimental examples are used to describe the high heat-resistant antioxidant solution for lithium battery copper foil of the present invention in detail. However, the following experimental examples are not intended to limit the present invention.

[0024] Experimental example

[0025] In order to prove that the copper foil treated with the high heat-resistant antioxidant solution of the present invention has better performance than the traditional hexavalent chromium formula lithium battery, this experimental example is specifically described below.

[0026] Example 1

[0027] After the plating solution on the raw foil was cleaned with pure water and air-dried, it was immersed in an antioxidant solution containing 390 ppm hexavalent chromium and 7000 ppm of heteroatomic organic matter for 8 seconds. The hexavalent chromium was derived from potassium dichromate, and the heteroatomic organic matter included 5-aminotetrazole and disodium ethylenediaminetetraacetic acid. The solution was tested using a 0.17 ampere / square decimeter (A / dm 2 ) for 0.5 seconds to form a heat-resistant and anti-oxidation layer on the surface of the copper foil. After testing, it was found that its heat resistance was 190°C for 10 minutes.

[0028] Example 2

[0029] After the plating solution on the raw foil was cleaned with pure water and air-dried, it was immersed in an antioxidant solution containing 390 ppm hexavalent chromium and 16,000 ppm of heteroatomic organic matter for 8 seconds. The hexavalent chromium was derived from potassium dichromate, and the heteroatomic organic matter included 5-aminotetrazole, disodium ethylenediaminetetraacetic acid, and ethylenediaminetetramethylenephosphoric acid. The solution was tested using a 0.17 ampere / square decimeter (A / dm 2 ) for 0.5 seconds to form a heat-resistant and anti-oxidation layer on the surface of the copper foil. After testing, it was found that its heat resistance was 210℃ for 10 minutes.

[0030] Example 3

[0031] After the plating solution on the raw foil was cleaned with pure water and air-dried, it was immersed in an antioxidant solution containing 390 ppm hexavalent chromium and 56,000 ppm of heteroatomic organic matter for 8 seconds. The hexavalent chromium was derived from potassium dichromate, and the heteroatomic organic matter included 5-aminotetrazole and potassium sodium tartrate. The solution was tested at 0.17 amperes per square decimeter (A / dm 2 ) for 0.5 seconds to form a heat-resistant and anti-oxidation layer on the surface of the copper foil. After testing, it was found that its heat resistance is 250°C for 10 minutes.

[0032] Comparative Example 1

[0033] After the plating solution on the raw foil was cleaned with pure water and air-dried, it was immersed in an antioxidant solution containing 988ppm hexavalent chromium for 8 seconds. The hexavalent chromium was derived from potassium dichromate. The solution was charged with 0.17 amperes per square decimeter (A / dm 2 ) for 0.5 seconds to form a heat-resistant and anti-oxidation layer on the surface of the copper foil. After testing, it was found that its heat resistance is 150°C for 10 minutes.

[0034] Based on the above heat resistance test, it can be seen that compared with Comparative Example 1 using a traditional hexavalent chromium formula, Examples 1 to 3 treated with the antioxidant solution of the present invention have higher heat resistance temperatures, and therefore have better heat resistance.

[0035] Lithium-ion copper foil battery performance comparison

[0036] The lithium battery copper foils of Example 1 and Comparative Example 1 were combined with commercially available negative electrode materials to form negative electrodes. The negative electrodes were then assembled into CR2032 button batteries, and their electrical properties, such as AC impedance and cycle life, were analyzed.

[0037] The button battery production process is as follows:

[0038] First, prepare the negative electrode slurry, whose solid phase composition includes 92wt% graphite (medium carbon FMGP-A), 5% polyvinylidene fluoride (PVDF 5130) and 3% conductive carbon black (Super P), and use NMP as solvent to prepare a uniform slurry with a solid content of 45%. Then, coat the negative electrode slurry on the lithium battery copper foil with a wet film thickness of 200μm and a coating speed of 2mm / s. After coating, first dry it in a 60℃ oven and then dry it in a 120℃ oven under vacuum. The dried negative electrode is rolled to a compaction density of 1.3 (g / cm 3) , and cut into circular electrodes with a diameter of 13mm. Next, the CR2032 button cell is assembled. From bottom to top, the lower cover, lithium metal sheet, PE separator, negative electrode, gasket, and spring are placed in order. After injecting the electrolyte of 1M LiPF6 in EC:DEC (1:1), the upper cover is installed and sealed with a sealing machine. This completes the battery assembly.

[0039] After the battery is assembled, it needs to be activated and charged and discharged three times at a current of 0.1C. The discharge mode is constant current-constant voltage (CC-CV), the charge mode is constant current, and the operating voltage range is 10mV to 2V.

[0040] The batteries of Comparative Example 1 and Example 1 were subjected to AC impedance analysis and the equivalent circuit diagram ( Figure 1 ) was fitted, and the results in Table 1 below show that the charge transfer impedance (R3) of Example 1 is better than that of Comparative Example 1.

[0041] Table 1 AC impedance fitting data of button battery

[0042] <![CDATA[R1]]> <![CDATA[R2]]> <![CDATA[R3]]> <![CDATA[R total ]]> Comparative Example 1 1.656 9.459 9.887 21.002 Example 1 1.679 4.306 9.187 15.172

[0043] The batteries from Comparative Example 1 and Example 1 were subjected to cycle life tests, performing charge-discharge cycles at a current of 1C, using a constant current-constant voltage (CC-CV) discharge mode and a constant current charge mode over an operating voltage range of 10mV to 2V. The cycle life was defined as the number of cycles required until the lithium battery's capacity dropped to 80% of its initial capacity. The test results are shown in Table 2 below.

[0044] Table 2 Cycle life test

[0045]

[0046]

[0047] In summary, the present invention provides a high-heat-resistant antioxidant liquid for lithium battery copper foil. By adding organic matter containing heteroatoms, it forms a coordination bond with the empty orbital of copper, forming a dense antioxidant layer on the surface of the copper foil. This can prevent the copper foil from oxidizing and discoloring at a high temperature of 210°C, effectively improving the heat resistance temperature. In this way, the copper foil treated with the antioxidant liquid of the present invention has better lithium battery performance than the traditional hexavalent chromium formula. In addition, the high-heat-resistant antioxidant liquid of the present invention adds organic matter containing heteroatoms to replace the heavy metals in the conventional technology. Therefore, it can not only effectively improve the heat resistance temperature, but also solve the problems of increased costs and sewage treatment.

Claims

1. An antioxidant solution for lithium battery copper foil, characterized in that: include: Hexavalent chromium; as well as Organic compounds containing heteroatoms, wherein the heteroatoms include N, O, S or P.

2. The antioxidant solution for lithium battery copper foil according to claim 1, characterized in that: Based on the total weight of the antioxidant solution for the lithium battery copper foil, the content of hexavalent chromium is 50 ppm to 1500 ppm, and the content of the organic matter containing heteroatoms is 3000 ppm to 60000 ppm.

3. The antioxidant solution for lithium battery copper foil according to claim 1, characterized in that: The sources of hexavalent chromium include chromium trioxide, chromate and dichromate.

4. The antioxidant solution for lithium battery copper foil according to claim 1, characterized in that: The organic compound containing heteroatoms includes benzotriazole, 2-thiolbenzoxazole, nitrogen-containing azoles, hydroxyethylene diphosphoric acid, aminotrimethylphosphonic acid, sodium ethylenediaminetetramethylene phosphate, ethylenediaminetetraacetic acid, sodium gluconate, sodium potassium tartrate or water-soluble silicone.

5. The antioxidant solution for lithium battery copper foil according to claim 4, characterized in that: The nitrogen-containing azoles include aminotriazole or aminotetrazolyl.

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