Antioxidant liquid, copper foil, pole piece and lithium ion battery

Abstract

The invention provides an antioxidant solution, a copper foil, a pole piece and a lithium ion battery. The antioxidant solution comprises the following components in percentage by mass: 0.05-0.5% of a first compound, 0.1-0.3% of borax, 0.05-0.2% of tannic acid, 0.1-1% of a second compound, 85-88% of ethanol and 11-14.7% of water, the first compound is prepared from 1-hydroxybenzotriazole and / or 5-chloro-2-methylbenzotriazole, and the second compound is prepared from 1-hydroxybenzotriazole and / or 5-chloro-2-methylbenzotriazole; the second compound comprises ascorbic acid and / or titanyl sulfate. The anti-oxidation liquid provided by the invention does not contain a chromium element, is simple in component and strong in anti-oxidation capability, and has excellent cycle performance and safety performance when being applied to a lithium ion battery by applying a pole piece prepared from the copper foil containing the anti-oxidation liquid to the lithium ion battery.

Description

Technical Field

[0001] This invention relates to an antioxidant liquid, and more particularly to an antioxidant liquid, copper foil, electrode sheet and battery thereof, belonging to the field of metal processing. Background Technology

[0002] Electrolytic copper foil is commonly used as the negative electrode current collector in lithium batteries, and its quality directly affects the cycle life of the lithium battery. The main production processes of electrolytic copper foil include: foil preparation, surface treatment, and slitting. Among these, the surface treatment of copper foil is a very important step. If the copper foil oxidizes and discolors, it will not only affect the appearance of the copper foil, but more importantly, it will lead to a decrease in the adhesion of the copper foil, and quality defects such as exposed foil spots in the coating, which will in turn affect the battery performance.

[0003] The surface treatment process for copper foil mainly involves passivation, which creates a passivation film on the copper foil surface to isolate easily oxidized copper from the air, thus preventing oxidation during long-term storage. Most passivation processes involve coating the copper foil surface with an antioxidant solution. However, commonly used antioxidant solutions have complex compositions and contain chromium, which can be harmful to human health and has poor environmental performance.

[0004] Given the above shortcomings, it is essential to develop an antioxidant liquid that is free of chromium, has a simple composition, and possesses strong antioxidant capabilities. Summary of the Invention

[0005] This invention provides an antioxidant liquid that is free of chromium, has a simple composition, and exhibits strong antioxidant capabilities.

[0006] This invention provides a copper foil obtained by treating it with an antioxidant solution. The copper foil has excellent antioxidant properties, which is beneficial for long-term storage and transportation.

[0007] The present invention also provides an electrode sheet comprising the aforementioned copper foil, which enables the battery to exhibit excellent cycle performance and safety performance.

[0008] The present invention also provides a lithium-ion battery with excellent cycle performance and safety performance.

[0009] This invention provides an antioxidant liquid, wherein the antioxidant liquid comprises, by mass percentage: 0.05-0.5% of a first compound, 0.1-0.3% of borax, 0.05-0.2% of tannic acid, 0.1-1% of a second compound, 85-88% of ethanol, and 11-14.7% of water;

[0010] The first compound includes 1-hydroxybenzotriazole and / or 5-chloro-2-methylbenzotriazole;

[0011] The second compound includes ascorbic acid and / or titanium oxysulfate.

[0012] The antioxidant liquid described above further includes 0.05-0.9% of an adjuvant selected from at least one of sodium molybdate, phytic acid, and sodium citrate.

[0013] The antioxidant liquid as described above, wherein the first compound comprises 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole, wherein the mass ratio of 1-hydroxybenzotriazole to 5-chloro-2-methylbenzotriazole is 2:1 to 5:1;

[0014] And / or, the second compound comprises ascorbic acid and titanium oxysulfate, wherein the mass ratio of ascorbic acid to titanium oxysulfate is 1:6 to 1:3.

[0015] The antioxidant liquid described above, wherein the adjuvants include sodium molybdate, phytic acid and sodium citrate, wherein the mass ratio of sodium molybdate, phytic acid and sodium citrate is (6-9):(1-3):(0.5-3).

[0016] The antioxidant liquid described above is prepared by a method comprising the following steps:

[0017] 1) Dissolve the first compound, borax, ascorbic acid, sodium molybdate, phytic acid, and sodium citrate in water to obtain a first mixture;

[0018] 2) Dissolve the titanium sulfate and tannic acid in ethanol to obtain a second mixture;

[0019] 3) Mix the first mixture and the second mixture evenly to obtain the antioxidant solution.

[0020] The present invention also provides a copper foil, wherein the copper foil is obtained by the following processing method:

[0021] 1) The copper foil is pretreated with the antioxidant liquid as described above to form an antioxidant liquid layer covering the surface of the copper foil;

[0022] 2) The antioxidant liquid layer is dried to obtain antioxidant copper foil.

[0023] The copper foil as described above, wherein the volume of the antioxidant solution required to cover a unit square meter of the copper foil surface is 30-40 mL.

[0024] The copper foil as described above, wherein the drying process sequentially includes heat treatment and cold treatment;

[0025] The heat treatment is performed at a temperature of 80-100℃ for 10-20 seconds; the cold treatment is performed at a temperature of 10-20℃ for 85-105 seconds.

[0026] The copper foil as described above, wherein the surface of the copper foil is the end face in the thickness direction of the copper foil.

[0027] The present invention also provides an electrode sheet, wherein the electrode sheet comprises copper foil as described above.

[0028] The present invention also provides a lithium-ion battery, wherein the lithium-ion battery includes the electrodes as described above.

[0029] This invention controls the components and mass percentage of the antioxidant solution, enabling the antioxidant solution to rapidly form a complete, uniform, and dense polymer composite film on the surface of copper foil, thereby giving the antioxidant solution excellent antioxidant properties.

[0030] The copper foil provided by this invention is obtained by a simple pretreatment-drying method. A dense and stable polymer composite film can be formed on the surface of the copper foil, which makes the treated copper foil resistant to oxidation. This prevents the copper foil from oxidizing and discoloring during transportation and storage, laying the foundation for its production and application.

[0031] The electrode provided by the present invention is made based on the above-mentioned copper foil. The active material of the electrode can be uniformly and firmly covered on the copper foil, thereby improving the cycle performance and safety performance of the battery.

[0032] The battery provided by this invention is made based on the above-mentioned electrode sheet, and the battery has excellent cycle performance and safety performance. Attached Figure Description

[0033] Figure 1 Photographs of the copper foil from Example 1, placed in an environment with normal temperature and humidity below 28% for 90 days;

[0034] Figure 2 A photograph of untreated copper foil placed in an environment with normal temperature and humidity below 28% for 90 days;

[0035] Figure 3 A photograph of the copper foil of Example 16 after being placed in an environment with normal temperature and humidity greater than 50% for 70 days;

[0036] Figure 4 A photograph of untreated copper foil placed in an environment with normal temperature and humidity greater than 50% for 70 days. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] This invention provides an antioxidant liquid, which comprises, by mass percentage: 0.05-0.5% of a first compound, 0.1-0.3% of borax, 0.05-0.2% of tannic acid, 0.1-1% of a second compound, 85-88% of ethanol, and 11-14.7% of water;

[0039] The first compound includes 1-hydroxybenzotriazole and / or 5-chloro-2-methylbenzotriazole;

[0040] The second compound includes ascorbic acid and / or titanium oxysulfate.

[0041] 1-Hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole contain nitrogen atoms as coordinating groups, enabling them to form a stable Cu(I)-BTA polymer composite film with copper foil. This prevents oxygen from reacting with the copper foil, thus avoiding oxidation. However, due to the slow film-forming rate of the polymer composite film, localized loss of the polymer composite film may occur. Therefore, the antioxidant properties of 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole for copper are insufficient to meet practical requirements.

[0042] Tannic acid is a phenolic compound that dissolves in water to form 3,4,5-trimonocarboxybenzoic acid, making its aqueous solution acidic and resulting in a higher concentration of carboxyl and hydroxyl groups. The active groups generated by hydrolysis can react with metals to form a dense passivation film on the metal surface, thereby improving its antioxidant capacity. However, when used alone, the adsorption of carboxyl groups on the foil surface weakens or even desorbs at higher temperatures, leading to poor antioxidant performance.

[0043] The addition of borax can promote the formation of passivation film on metal surfaces, improve the durability and adhesion of antioxidant solutions, and thus enhance the antioxidant capacity of antioxidant solutions.

[0044] Ascorbic acid is readily soluble in water, which facilitates solution preparation during production and reduces the impact of impurities caused by solubility issues on the foil surface. It also possesses strong reducing properties, preventing metal oxidation. However, when used alone, it cannot form a dense passivation film on the metal surface, resulting in poor oxidation resistance.

[0045] Titanium oxysulfate is a reducing agent that can slow down metal oxidation. However, when used alone, it cannot form a dense passivation film on the metal surface, resulting in poor oxidation resistance.

[0046] This invention, by selecting the aforementioned components and controlling the mass percentage of each component, enables the preparation of an antioxidant liquid with simple composition and high antioxidant properties. The inventors analyzed the principle behind this and believe the reason may lie in the fact that when the contents of the aforementioned components are matched, the components mutually promote interfacial interactions, allowing the antioxidant liquid to rapidly form a complete, uniform, and dense polymer composite film on the copper foil surface. This prevents the copper foil from reacting with oxygen. Simultaneously, the antioxidant liquid has a weakly acidic pH, which facilitates the hydrolysis of the components in the antioxidant liquid to generate active groups, forming a stable polymer composite film, thereby giving the antioxidant liquid excellent antioxidant properties.

[0047] In one specific embodiment, the antioxidant solution further includes 0.05-0.9% of an additive selected from at least one of sodium molybdate, phytic acid, and sodium citrate. When sodium molybdate, phytic acid, or sodium citrate is selected as an additive, and the above-mentioned mass percentage of the additive is added to the antioxidant solution, the polymer composite film formed by the antioxidant solution on the copper foil surface has higher density, which further prevents the reaction between the copper foil and oxygen, thereby increasing the antioxidant activity of the antioxidant solution.

[0048] In one specific embodiment, the first compound comprises 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole, with a mass ratio of 1-hydroxybenzotriazole to 5-chloro-2-methylbenzotriazole of 2:1 to 5:1. When 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole are selected as the first compound and their mass ratio is controlled within the above range, the 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole are well-matched, further enhancing the interfacial interaction, resulting in a more compact polymer composite film and superior antioxidant performance of the antioxidant solution.

[0049] The combination of 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole can enhance the adsorption of metals through synergistic effects.

[0050] In one specific embodiment, the second compound comprises ascorbic acid and titanium oxysulfate, with a mass ratio of ascorbic acid to titanium oxysulfate of 1:6 to 1:3. When ascorbic acid and titanium oxysulfate are selected as the second compound and their mass ratio is controlled within the range of 1:6 to 1:3, the combined effect of ascorbic acid and titanium oxysulfate can more quickly and efficiently reduce oxidized copper oxide to elemental copper, reduce the oxidation rate of copper foil, and further enhance the antioxidant performance of the antioxidant solution.

[0051] In one specific embodiment, the additives include sodium molybdate, phytic acid, and sodium citrate, with a mass ratio of (6-9):(1-3):(0.5-3). When these compounds are selected as additives and their mass ratios are within the above range, the density of the polymer composite film is further improved, thereby resulting in higher antioxidant properties of the antioxidant liquid.

[0052] In one specific embodiment, the antioxidant liquid is prepared by a method comprising the following process:

[0053] 1) Dissolve the first compound, borax, ascorbic acid, sodium molybdate, phytic acid, and sodium citrate in water to obtain the first mixture;

[0054] 2) Dissolve titanium sulfate and tannic acid in ethanol to obtain a second mixture;

[0055] 3) Mix the first mixture and the second mixture evenly to obtain an antioxidant solution.

[0056] Specifically, in step 1), at room temperature and pressure, the first compound, borax, ascorbic acid, sodium molybdate, phytic acid, sodium citrate and water are mixed until all compounds are dissolved to obtain a homogeneous first mixture.

[0057] This invention does not limit the mixing method, as long as the compounds can be dissolved in water.

[0058] In step 2), at room temperature and pressure, titanium oxysulfate, tannic acid and ethanol are mixed until titanium oxysulfate and tannic acid dissolve in ethanol to obtain a second mixture.

[0059] This invention does not limit the mixing method, as long as it can dissolve titanium sulfate and tannic acid in ethanol.

[0060] In step 3), the first mixture and the second mixture are mixed until homogeneous to obtain an antioxidant solution.

[0061] The present invention does not limit the mixing method. For example, the first mixture can be added drop by drop to the second mixture, and the mixture can be added drop by drop until the mixture is uniform.

[0062] The antioxidant liquid prepared by the above method according to this invention allows all components to dissolve completely, resulting in stable physicochemical properties and long-term storage and use. Furthermore, the uniform mixing of components ensures a synergistic effect, leading to a denser and more stable polymer composite film, thus enhancing the antioxidant capacity of the antioxidant liquid. Simultaneously, this method is simple and easy to operate, facilitating the large-scale production of the antioxidant liquid.

[0063] The present invention also provides a copper foil, which is obtained by the following processing method:

[0064] 1) The copper foil is pretreated with an antioxidant solution to form an antioxidant solution layer covering the surface of the copper foil;

[0065] 2) The anti-oxidation liquid layer is dried to obtain anti-oxidation copper foil.

[0066] Specifically, in step 1), an antioxidant solution is used to pretreat the copper foil surface, so that an antioxidant solution layer is formed on the copper foil surface.

[0067] The present invention does not specifically limit the surface of the copper foil; it can be the surface in the length and width direction of the copper foil or the end face in the thickness direction of the copper foil.

[0068] The present invention does not impose any special limitations on the pretreatment. For example, a sponge strip soaked in antioxidant liquid can be used to perform a rolling brush treatment on the surface of the copper foil so that the surface of the copper foil is covered with an antioxidant liquid layer.

[0069] In step 2), the antioxidant liquid layer is dried to obtain antioxidant copper foil.

[0070] The present invention does not impose any special limitations on the drying process, as long as the antioxidant liquid layer can be dried evenly. For example, the antioxidant liquid layer can be dried by baking.

[0071] This invention utilizes a simple pretreatment-drying method to uniformly coat an antioxidant solution onto the surface of copper foil, followed by drying to form an antioxidant layer. This results in a dense and stable polymer composite film on the copper foil surface, leading to copper foil with excellent antioxidant properties and extended shelf life. Furthermore, this method offers advantages such as simple process, ease of operation, and readily available raw materials, enabling large-scale production of antioxidant copper foil.

[0072] In one specific embodiment, the volume of antioxidant solution required to cover a unit square meter of copper foil surface is 30-40 mL. When the volume of antioxidant solution used is within the above range, the polymer composite film formed by the antioxidant solution on the copper foil surface can completely and uniformly cover the copper foil, avoiding copper foil oxidation caused by incomplete distribution of the polymer composite film, and also avoiding waste of raw materials and increased costs due to excessive use of antioxidant solution, thereby obtaining antioxidant copper foil with high antioxidant properties.

[0073] In one specific embodiment, the drying process sequentially includes heat treatment and cold treatment; wherein the heat treatment temperature is 80-100℃ and the time is 10-20s; the cold treatment temperature is 10-20℃ and the time is 85-105s. When heat treatment and cold treatment are sequentially used to dry the antioxidant solution, the drying efficiency can be effectively improved, and the antioxidant solution can be evenly covered and not easily diffused, forming a uniform and complete polymer composite film on the copper foil surface. This avoids the rupture, accumulation, and incompleteness of the polymer composite film, thereby further improving the oxidation resistance of the antioxidant copper foil.

[0074] In one specific embodiment, the surface of the copper foil is the end face in the thickness direction of the copper foil. After the end face in the thickness direction of the copper foil is treated with an antioxidant solution, the end face of the copper foil will not oxidize or discolor during transportation, storage, and processing. Therefore, the copper foil can be cut into wide widths as required, and no oxidation will occur subsequently, which greatly facilitates the actual production and application of copper foil.

[0075] The present invention also provides an electrode sheet comprising the aforementioned copper foil. The electrode sheet provided by the present invention includes a current collector and an active material layer disposed on the surface of the current collector, wherein the current collector is a copper foil. When the aforementioned copper foil is used as the current collector, the active material layer can uniformly and firmly cover the copper foil, thereby improving the cycle performance and safety performance of the battery.

[0076] This invention does not limit the specific selection of the active material layer, and the selection can be made according to actual needs. Generally, copper foil is used as the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a binder, a conductive agent, and other additives.

[0077] In one specific embodiment, the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate. The binder may include styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS), etc.; the conductive agent may include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, single-walled carbon nanotubes, graphene, and carbon nanofibers, etc.; the additives include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), etc.

[0078] The present invention also provides a lithium-ion battery, which is prepared based on the above-mentioned electrode and has excellent cycle performance and safety performance.

[0079] In one specific embodiment, the lithium-ion battery further includes a positive electrode sheet, an electrolyte, and a separator. The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector; the positive current collector may include aluminum foil. The positive active material layer includes a positive active material, a conductive agent, and a binder. The positive active material may include LiNi. 0.7 Co 0.1 Mn 0.2 O2(NCM712), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.8 Co 0.15 Al0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, etc. Conductive agents may include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, etc. Binders may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins, etc.

[0080] The present invention does not limit the specific selection of electrolyte and diaphragm, and can select them according to actual needs. They can be electrolytes and diaphragms commonly used in the art.

[0081] The present invention will be further described in detail below through specific embodiments.

[0082] Example 1

[0083] The copper foil in this example is obtained by processing it as follows:

[0084] Preparation of antioxidant solution: 0.2% 1-hydroxybenzotriazole, 0.1% 5-chloro-2-methylbenzotriazole, 0.2% borax, 0.2% ascorbic acid, 0.7% sodium molybdate, 0.1% phytic acid, and 0.1% sodium citrate were dissolved in 11.7% water to obtain a first mixture; 0.6% titanium oxysulfate and 0.1% tannic acid were dissolved in 86% ethanol to obtain a second mixture.

[0085] 2. Treat copper foil with antioxidant solution: Coat the copper foil with antioxidant solution on the end face in the thickness direction, and then perform heat treatment at 80℃ for 15s, followed by cold treatment at 10℃ for 90s to obtain antioxidant copper foil.

[0086] The volume of antioxidant solution required to cover a unit square meter of copper foil surface is 30 mL.

[0087] Example 2

[0088] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution comprises, by mass percentage: 0.25% 1-hydroxybenzotriazole, 0.05% 5-chloro-2-methylbenzotriazole, 0.1% borax, 0.1% ascorbic acid, 0.6% sodium molybdate, 0.1% phytic acid, 0.05% sodium citrate, 0.6% titanium oxysulfate, 0.1% tannic acid, 11.05% water, and 87% ethanol.

[0089] Example 3

[0090] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution comprises, by mass percentage: 0.1% 1-hydroxybenzotriazole, 0.1% 5-chloro-2-methylbenzotriazole, 0.2% borax, 0.4% ascorbic acid, 0.7% sodium molybdate, 0.1% phytic acid, 0.1% sodium citrate, 0.4% titanium oxysulfate, 0.1% tannic acid, 11.8% water, and 86% ethanol.

[0091] Example 4

[0092] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution comprises, by mass percentage: 0.2% 1-hydroxybenzotriazole, 0.1% 5-chloro-2-methylbenzotriazole, 0.2% borax, 0.2% ascorbic acid, 0.01% sodium molybdate, 0.01% phytic acid, 0.01% sodium citrate, 0.6% titanium oxysulfate, 0.1% tannic acid, 12.57% water, and 86% ethanol.

[0093] Example 5

[0094] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution comprises, by mass percentage: 0.1% 1-hydroxybenzotriazole, 0.1% 5-chloro-2-methylbenzotriazole, 0.2% borax, 0.2% ascorbic acid, 0.01% sodium molybdate, 0.01% phytic acid, 0.01% sodium citrate, 0.4% titanium oxysulfate, 0.1% tannic acid, 12.87% water, and 86% ethanol.

[0095] Example 6

[0096] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.5% 1-hydroxybenzotriazole, 0.3% borax, 0.3% ascorbic acid, 0.1% tannic acid, 12.8% water, and 86% ethanol.

[0097] Example 7

[0098] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.1% 5-chloro-2-methylbenzotriazole, 0.3% borax, 1% titanium oxysulfate, 0.1% tannic acid, 12.5% ​​water, and 86% ethanol.

[0099] Example 8

[0100] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.1% 5-chloro-2-methylbenzotriazole, 0.3% borax, 1% titanium oxysulfate, 0.1% tannic acid, 0.6% sodium molybdate, 11.9% water, and 86% ethanol.

[0101] Example 9

[0102] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.1% 5-chloro-2-methylbenzotriazole, 0.3% borax, 1% titanium oxysulfate, 0.1% tannic acid, 0.1% phytic acid, 12.4% water, and 86% ethanol.

[0103] Example 10

[0104] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.1% 5-chloro-2-methylbenzotriazole, 0.3% borax, 1% titanium oxysulfate, 0.1% tannic acid, 0.05% sodium citrate, 12.45% water, and 86% ethanol.

[0105] Example 11

[0106] The copper foil processing method in this embodiment is basically the same as that in Embodiment 1, except that the volume of antioxidant solution required to cover a unit square meter of copper foil surface is 35 mL.

[0107] Example 12

[0108] The copper foil processing method in this embodiment is basically the same as that in Embodiment 1, except that the volume of antioxidant solution required to cover a unit square meter of copper foil surface is 45 mL.

[0109] Example 13

[0110] The copper foil processing method in this embodiment is basically the same as that in Embodiment 1, except that the heat treatment temperature is 90°C and the time is 15s, and the cold treatment temperature is 20°C and the time is 90s.

[0111] Example 14

[0112] The copper foil processing method in this embodiment is basically the same as that in Embodiment 1, except that the heat treatment temperature is 70°C and the time is 15s, and the cold treatment temperature is 30°C and the time is 90s.

[0113] Example 15

[0114] The copper foil processing method in this embodiment is basically the same as that in Embodiment 1, except that the cold treatment is 10 seconds and the time is 180 seconds.

[0115] Example 16

[0116] The copper foil processing method in this embodiment is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.1% 5-chloro-2-methylbenzotriazole, 0.3% borax, 1% titanium oxysulfate, 0.2% tannic acid, 0.8% sodium molybdate, 0.3% sodium citrate, 11.3% water, and 86% ethanol.

[0117] Comparative Example 1

[0118] The copper foil treatment method in this comparative example is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.2% borax, 0.6% titanium oxysulfate, 0.1% tannic acid, 13.1% water, and 86% ethanol.

[0119] Comparative Example 2

[0120] The copper foil treatment method in this comparative example is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.2% 1-hydroxybenzotriazole, 0.6% titanium oxysulfate, 0.1% tannic acid, 13.1% water, and 86% ethanol.

[0121] Comparative Example 3

[0122] The copper foil treatment method in this comparative example is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.2% 1-hydroxybenzotriazole, 0.2% borax, 0.6% titanium oxysulfate, 13% water, and 86% ethanol.

[0123] Comparative Example 4

[0124] The copper foil treatment method in this comparative example is basically the same as that in Example 1, except that the antioxidant solution includes the following components by mass percentage: 0.2% 1-hydroxybenzotriazole, 0.2% borax, 0.1% tannic acid, 13.5% water, and 86% ethanol.

[0125] Test case

[0126] The copper foils of Examples 1-15 and Comparative Examples 1-4 were placed in an environment with room temperature and 28% humidity. The discoloration of the copper foils was observed. The experiment ended when the end face of the copper foil showed signs of discoloration. The number of days without oxidation was recorded, as shown in Table 1.

[0127] The copper foil of Example 16 was placed in an environment with room temperature and 50% humidity, and the discoloration of the copper foil was observed. The experiment ended when the end face of the copper foil showed signs of discoloration. The number of days without oxidation was recorded, as shown in Table 1.

[0128] See the photograph of the copper foil in Example 1. Figure 1 See the photo of the untreated copper foil. Figure 2 ,like Figure 1 and 2 As shown, the treated copper foil did not show any discoloration after being placed in an environment with normal temperature and humidity below 28% for 90 days.

[0129] See the photograph of the copper foil in Example 16. Figure 3 See the photo of the untreated copper foil. Figure 4 ,like Figure 3 and 4 As shown, the treated copper foil did not show any discoloration after being placed in an environment with room temperature and humidity greater than 50% for 70 days.

[0130] Table 1. Test results of copper foils in Examples 1-16 and Comparative Examples 1-4

[0131]

[0132]

[0133] As shown in Table 1, through the comparison of Examples 1-16 and Comparative Examples 1-4, the antioxidant liquid provided by the present invention has excellent antioxidant properties, enabling copper foil to remain unoxidized for 90 days in an environment with humidity below 28%. Furthermore, the antioxidant liquid does not contain chromium and has a simple composition, which is beneficial for its widespread application in copper foil processing.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An antioxidant liquid, characterized in that, The antioxidant solution comprises, by mass percentage: 0.05-0.5% of the first compound, 0.1-0.3% of borax, 0.05-0.2% of tannic acid, 0.1-1% of the second compound, 85-88% of ethanol, and 11-14.7% of water; The first compound includes 1-hydroxybenzotriazole and / or 5-chloro-2-methylbenzotriazole; The second compound includes ascorbic acid and / or titanium oxysulfate.

2. The antioxidant liquid according to claim 1, characterized in that, The antioxidant solution also includes 0.05-0.9% of an auxiliary agent, which is selected from at least one of sodium molybdate, phytic acid, and sodium citrate.

3. The antioxidant liquid according to claim 1 or 2, characterized in that, The first compound comprises 1-hydroxybenzotriazole and 5-chloro-2-methylbenzotriazole, wherein the mass ratio of 1-hydroxybenzotriazole to 5-chloro-2-methylbenzotriazole is 2:1 to 5:1; And / or, the second compound comprises ascorbic acid and titanium oxysulfate, wherein the mass ratio of ascorbic acid to titanium oxysulfate is 1:6 to 1:

3.

4. The antioxidant liquid according to claim 2, characterized in that, The additives include sodium molybdate, phytic acid and sodium citrate, wherein the mass ratio of sodium molybdate, phytic acid and sodium citrate is (6-9):(1-3):(0.5-3).

5. The antioxidant liquid according to claim 4, characterized in that, The antioxidant liquid is prepared by a method comprising the following steps: 1) Dissolve the first compound, borax, ascorbic acid, sodium molybdate, phytic acid, and sodium citrate in water to obtain a first mixture; 2) Dissolve the titanium sulfate and tannic acid in ethanol to obtain a second mixture; 3) Mix the first mixture and the second mixture evenly to obtain the antioxidant solution.

6. A copper foil, characterized in that, The copper foil is obtained by the following processing method: 1) The copper foil is pretreated with the antioxidant liquid according to any one of claims 1-5 to form an antioxidant liquid layer covering the surface of the copper foil; 2) The antioxidant liquid layer is dried to obtain antioxidant copper foil.

7. The copper foil according to claim 6, characterized in that, The volume of the antioxidant solution required to cover one square meter of the copper foil surface is 30-40 mL.

8. The copper foil according to claim 6 or 7, characterized in that, The drying process includes heat treatment and cold treatment in sequence; The heat treatment is performed at a temperature of 80-100℃ for 10-20 seconds; the cold treatment is performed at a temperature of 10-20℃ for 85-105 seconds.

9. The copper foil according to claim 8, characterized in that, The surface of the copper foil is the end face in the thickness direction of the copper foil.

10. An electrode sheet, characterized in that, The electrode comprises the copper foil as described in any one of claims 6-9.

11. A lithium-ion battery, characterized in that, The lithium-ion battery includes the electrode as described in claim 10.

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