Current collector and preparation method and application thereof

Abstract

The invention discloses a current collector and a preparation method and application thereof. The current collector comprises a current collector base material, the current collector base material is provided with a first surface and a second surface which are oppositely arranged, at least one side edge of the first surface and / or the second surface is provided with an insulating layer, and the insulating layer comprises boehmite, sodium polyacrylate and a phosphate ester polymer. According to the current collector, the insulating layer is arranged at the edge, and the dispersity of boehmite can be improved by utilizing the synergistic effect of the boehmite, sodium polyacrylate and phosphate ester polymer in the insulating layer, so that the coating is uniform and complete, the insulating property of the insulating layer is effectively improved, and the safety performance of the battery can be further improved.

Description

A current collector, its preparation method and application Technical Field

[0001] This invention belongs to the field of battery technology and relates to a current collector, its preparation method, and its uses. Background Technology

[0002] Lithium-ion batteries (LIBs) have been widely adopted in various fields such as consumer electronics, transportation, power tools, and energy storage. In lithium-ion batteries, the current collector is a key component, responsible for collecting and conducting current as well as loading the active material. Composite current collectors based on aluminum foil are generally formed by combining aluminum foil with other materials (such as paper, plastic film, coatings, etc.). Compared to aluminum foil itself, these composite current collectors can impart new properties and functions to aluminum foil, meeting the needs of different industries.

[0003] To improve lithium battery performance, the lithium battery industry employs a carbon-coated current collector strategy to increase rate capability and overall performance. However, to enhance the safety of the current collector, a ceramic edge-coating technique is used, specifically applying ceramic slurry to the edges of the carbon-coated current collector. This technique is crucial for lithium battery manufacturing: 1. Safety: Directly reduces the risk of short circuits and thermal runaway, meeting the high safety standards of power batteries (such as those used in electric vehicles). 2. Lifespan Improvement: Reduces edge side reactions (such as lithium plating and corrosion), extending cycle life. 3. High Energy Density Design: Edge protection allows for more aggressive optimization of electrode thickness or material systems. Therefore, the core purpose of carbon-coated current collector edge treatment is to "eliminate edge risks and improve battery reliability and performance," representing a key step in detail optimization during battery manufacturing, especially important in high-end applications (such as power batteries and high-nickel systems).

[0004] CN118610379A discloses a positive electrode sheet, its preparation method, and a lithium-ion battery. The preparation method includes the following steps: (1) coating a ceramic slurry onto at least one edge of the current collector surface and drying it to obtain a current collector containing a ceramic edge coating; (2) coating a positive electrode slurry onto the uncoated area of ​​the current collector surface and drying it to obtain the positive electrode sheet. The preparation method of the ceramic slurry includes the following steps: first mixing a binder with a portion of inorganic filler, then adding the remaining inorganic filler and performing a second mixing to obtain a mixture; and third mixing the mixture with a solvent to obtain a ceramic slurry. The inorganic filler includes any one or a combination of at least two of boehmite, barium titanate, aluminum oxide, titanium dioxide, magnesium oxide, or silicon carbide; the binder in the ceramic slurry includes any one or a combination of at least two of polyimide, styrene-butadiene rubber, carboxymethyl cellulose, or polyarylene. This method, by coating the edge area of ​​the current collector surface with a ceramic slurry, can solve the problem of short circuit between the positive and negative electrodes and improve safety performance.

[0005] However, due to the generally small particle size and large specific surface area of ​​ceramic materials, the dispersibility of ceramic slurries is poor, failing to effectively utilize the inherent advantages of ceramic materials and resulting in reduced insulation performance. Therefore, providing a current collector with excellent insulation properties at its edge is a pressing technical problem that needs to be solved. Summary of the Invention

[0006] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a current collector, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a current collector comprising a current collector substrate having a first surface and a second surface disposed opposite to each other, wherein an insulating layer is disposed on at least one edge of the first surface and / or the second surface, the insulating layer comprising boehmite, sodium polyacrylate and phosphate polymer.

[0009] The current collector of the present invention has an insulating layer at its edge. Since the insulating layer includes boehmite, its surface is rich in Al. 3+ With Al-OH active sites, boehmite possesses high resistivity and strong insulation properties. Simultaneously, phosphate polymers effectively improve the dispersibility of boehmite. The main mechanisms of action include: First, as polymers, phosphate polymers have long molecular chains, allowing them to form a thicker and more stable polymer adsorption layer around the boehmite. When particles approach each other, this polymer adsorption layer generates a strong physical repulsion force, effectively preventing particle aggregation. Second, the -PO4³⁻ in the phosphate polymer forms a stable Al-OP structure with the Al³⁺ on the boehmite surface through coordination bonds. The chemical bond energy is >200 kJ / mol, stronger than carboxylate adsorption. Even under alkaline conditions, when the boehmite surface is negatively charged, the phosphate polymer can overcome electrostatic repulsion through multidentate chelation, resulting in strong adsorption. Therefore, the introduction of phosphate polymers effectively improves the dispersibility of boehmite. Furthermore, sodium polyacrylate (PAA-Na) synergistically improves the dispersibility of boehmite through a dual mechanism of electrostatic repulsion and anchoring adsorption. Anchoring adsorption refers to the -COO group of sodium polyacrylate... - Ligand exchange occurs with the Al-OH on the boehmite surface, forming stable Al-OOC- bonds, which provides dispersibility. The combined effect of these factors ensures the uniformity and complete coverage of the coating, allowing the advantages of boehmite itself to be effectively utilized, thus significantly improving the safety performance of the battery.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0011] Preferably, the thickness of the insulating layer on one side is 1μm to 3μm.

[0012] Preferably, the width of the insulating layer is 200mm to 500mm.

[0013] Preferably, the boehmite has a particle size of <150 nm.

[0014] Preferably, the boehmite mass fraction is 50% to 80% based on the total mass of the insulating layer.

[0015] Preferably, the mass ratio of sodium polyacrylate to boehmite is 1:1 to 1:6.

[0016] Preferably, the phosphate polymer accounts for 2% to 8% of the mass of the boehmite.

[0017] Preferably, the current collector substrate comprises metal foil or carbon-coated metal foil.

[0018] Preferably, the metal foil material includes at least one of aluminum, aluminum alloy, copper, and copper alloy.

[0019] In a second aspect, the present invention provides a method for preparing a current collector as described in the first aspect, the method comprising the following steps:

[0020] Preparation of an insulating grout comprising boehmite, sodium polyacrylate, and phosphate polymer;

[0021] The insulating slurry is applied to at least one edge of at least one side surface of the current collector substrate and dried to obtain the current collector.

[0022] Preferably, the method for preparing the slurry includes:

[0023] (1) Mix sodium polyacrylate with water to obtain a glue solution;

[0024] (2) Add phosphate polymer to the adhesive solution and stir to obtain the first slurry;

[0025] (3) Boehmite is added to the first slurry in multiple batches, and the mixture is stirred after each addition of boehmite to obtain the second slurry;

[0026] (4) Adjust the concentration and pH of the second slurry to obtain the insulating slurry.

[0027] In the method of the present invention, boehmite is added in multiple batches, and stirring is performed after each addition of boehmite, which helps to improve the dispersibility of the slurry.

[0028] Preferably, the sodium polyacrylate in step (1) is pre-adjusted to pH 7-9 before use.

[0029] In one embodiment, the pH of sodium polyacrylate is adjusted to 7-9 using a 0.1M NaOH solution.

[0030] Preferably, the solid content of the adhesive solution in step (1) is 15% to 25%.

[0031] Preferably, the viscosity of the adhesive solution in step (1) is 800 mPa·s to 3000 mPa·s.

[0032] The present invention does not specifically limit the mixing method described in step (1). For example, it can be mixed in a stirrer at a speed of 2000 r / min for 60 min.

[0033] Preferably, in step (2), after adding the phosphate polymer, the stirring speed is 200 r / min to 600 r / min; the stirring time is 15 min to 25 min.

[0034] Preferably, in step (3), after each addition of boehmite, the stirring speed is independently 2000 r / min to 2600 r / min; the stirring time is 10 min to 90 min.

[0035] Preferably, in step (4), the concentration of the slurry is adjusted so that the solid content is 3% to 8%.

[0036] Preferably, in step (4), the pH is adjusted to 6-8.

[0037] Preferably, the preparation method further includes step (5), which includes: after adjusting the concentration and pH of the second slurry, adding a wetting agent to the slurry and stirring to obtain a third slurry. In this step, the reagent used to adjust the pH can be, for example, a NaOH solution.

[0038] The present invention does not specifically limit the type of wetting agent, such as polyether siloxane, modified polyether siloxane or alcohol reagent.

[0039] In this invention, modified polyether siloxane refers to polyether siloxane derivatives obtained by chemically modifying polyether siloxane. Chemical modification may include, for example, introducing functional groups such as epoxy, amino, or ester groups, or adjusting the chain segment ratio.

[0040] Preferably, the wetting agent accounts for 8% to 12% of the total mass of the second slurry.

[0041] Preferably, the preparation method further includes homogenizing the second slurry or the third slurry.

[0042] Preferably, the pressure of the homogenization process is 500 bar to 800 bar.

[0043] This invention does not specifically limit the preparation method of phosphate ester polymers. Exemplarily, a method for preparing phosphate ester polymers is provided. The preparation principle is: phosphate ester-terminated polymers are generated by esterification of polyethylene glycol with phosphorus pentoxide. The specific preparation method includes the following steps:

[0044] ① Dehydration of polyethylene glycol: Dehydrate polyethylene glycol under vacuum (pressure -0.1MPa) conditions at 100℃ for 2 hours, and set aside for later use;

[0045] ② Esterification reaction: Under nitrogen protection, polyethylene glycol is added to a three-necked flask, the temperature is raised to 60°C, and phosphorus pentoxide is slowly added. The molar ratio of polyethylene glycol to phosphorus pentoxide is 1:(1~1.5). The reaction temperature is controlled at less than or equal to 80°C, and the reaction time is 6 hours. During this period, an equal volume of deionized water is added dropwise every 1 hour to promote hydrolysis.

[0046] ③ Neutralization and purification: After the reaction product is cooled to room temperature, the pH is adjusted to 9-10 with 0.1mM NaOH, and then the small molecule phosphate is removed by washing with a large amount of anhydrous ethanol. The product is then freeze-dried at -10℃ to obtain the phosphate ester polymer.

[0047] This invention does not specifically limit the preparation method of sodium polyacrylate (PAA-Na). Exemplarily, the preparation method of sodium polyacrylate includes the following steps:

[0048] (A) Polymerization reaction:

[0049] ① Preparation of premixed solution: Mix acrylic acid and deionized water in a beaker and stir at 600 r / min for 20 min on a magnetic stirrer to obtain glue with a solid content of 20%~25%; after stirring, add isopropanol accounting for 10% of the total mass of the premixed solution to adjust the tension of the solution and obtain the premixed solution.

[0050] ②Initiator preparation: Dissolve ammonium persulfate in deionized water and stir on a magnetic stirrer at 1500 r / min for 30 min until completely dissolved to obtain a 1M ammonium persulfate solution;

[0051] ③ Under nitrogen protection, add the premixed solution to a three-necked flask, heat to 70°C, and slowly add 0.5% of the total mass of the premixed solution of ammonium persulfate solution (to be added over 30 minutes). Keep the temperature to carry out the polymerization reaction. Use a viscometer to test the viscosity of the reaction system. When the viscosity reaches 500 mPa·s, stop the polymerization reaction.

[0052] (B) Neutralization reaction:

[0053] ① Cooling and dilution: Cool the polymerized binder to 40°C and dilute it with water until the viscosity is reduced to less than or equal to 100 mPa·s;

[0054] ② Partial neutralization: Add 0.1 mM NaOH solution dropwise, keeping the temperature below 50℃, until pH = 8.0. Note: Monitor the pH in real time with a pH meter to avoid localized over-alkalinity leading to hydrolysis. By adjusting PAA-Na to alkalinity, PAA-Na can ionize into negatively charged polyacrylic acid chains (-COO). - (This) inhibits the agglomeration of boehmite particles through electrostatic repulsion.

[0055] (3) Purification and post-processing to remove residual monomers:

[0056] Add 0.1 mM sodium bisulfite, then concentrate the solution under reduced pressure at 60°C, spray dry and then vacuum dry to obtain PAA-Na powder.

[0057] Thirdly, the present invention provides an electrode sheet comprising the current collector described in the first aspect and an active material layer disposed on at least one side surface of the current collector.

[0058] Fourthly, the present invention provides an electrochemical device comprising the current collector described in the first aspect, or the electrode described in the third aspect.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Compared with existing technologies, the present invention has the following beneficial effects:

[0061] (1) The current collector of the present invention has an insulating layer at the edge. Since the insulating layer includes boehmite, its surface is rich in Al. 3+With Al-OH active sites, boehmite possesses high resistivity and strong insulation properties. Simultaneously, phosphate polymers effectively improve the dispersibility of boehmite. The main mechanisms of action include: First, as polymers, phosphate polymers have long molecular chains, allowing them to form a thicker and more stable polymer adsorption layer around the boehmite. When particles approach each other, this polymer adsorption layer generates a strong physical repulsion force, effectively preventing particle aggregation. Second, the -PO4³⁻ in the phosphate polymer forms a stable Al-OP structure with the Al³⁺ on the boehmite surface through coordination bonds. The chemical bond energy is >200 kJ / mol, stronger than carboxylate adsorption. Even under alkaline conditions, when the boehmite surface is negatively charged, the phosphate polymer can overcome electrostatic repulsion through multidentate chelation, achieving strong adsorption. Therefore, the introduction of phosphate polymers effectively improves the dispersibility of boehmite. Furthermore, sodium polyacrylate (PAA-Na) synergistically improves the dispersibility of boehmite through a dual mechanism of electrostatic repulsion and anchoring adsorption. Anchoring adsorption refers to the -COO group of sodium polyacrylate... - Ligand exchange occurs with the Al-OH on the boehmite surface, forming stable Al-OOC- bonds, which provides dispersibility. The combined effect of these factors ensures the uniformity and complete coverage of the coating, allowing the advantages of boehmite itself to be effectively utilized, thus significantly improving the safety performance of the battery.

[0062] (2) The surface sheet resistance of the current collector of the present invention is 10KΩ or more, preferably 5MΩ or more; the penetration resistance of the current collector of the present invention is 200Ω or more, preferably 4.5KΩ or more. Detailed Implementation

[0063] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0064] The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0065] In this embodiment of the invention, the sources of various raw materials used are as follows:

[0066] Boehmite: Purchased from Zhejiang Manli Nanotechnology Co., Ltd., model number ML-ALOOH-YN100, particle size <150nm.

[0067] Polyethylene glycol: purchased from Merck Chemicals, model number P2139, with a number average molecular weight of 8,000.

[0068] Sodium hydroxide: purchased from Merck Chemicals, model number 221465, ACS reagent purity ≥97.0%.

[0069] Phosphorus pentoxide: purchased from Merck Chemicals, model number 1.00570.

[0070] Anhydrous ethanol: purchased from Sinopharm Group, model AR (Shanghai Trial), purity ≥99.7%, Sinopharm code 10009218.

[0071] Acrylic acid: purchased from Merck Chemicals, model number 147230, anhydrous grade, containing 200 ppm MEHQ as a polymerization inhibitor, with a purity of 99%.

[0072] Isopropanol: Purchased from Merck Chemicals, model number W292907, purity ≥99.7%.

[0073] Ammonium persulfate: purchased from Merck Chemicals, model A7460, purity ≥98.0%.

[0074] Sodium hydroxide: purchased from Merck Chemicals, model number 221465, purity ≥97.0%.

[0075] Sodium bisulfite: purchased from Merck Chemicals, model number 243973.

[0076] In one embodiment of the present invention, a current collector is provided, comprising a current collector substrate having a first surface and a second surface disposed opposite to each other, wherein an insulating layer is disposed on at least one edge of the first surface and / or the second surface, the insulating layer comprising boehmite, sodium polyacrylate and phosphate polymer.

[0077] In one embodiment, the thickness of the insulating layer on one side is 1 μm to 3 μm, for example, it can be 1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.7 μm, 2 μm, 2.2 μm, 2.5 μm, 2.6 μm, 2.8 μm, or 3 μm. Within this range, it is beneficial to ensure good insulation effect and enable the battery to have good electrochemical performance.

[0078] In one embodiment, the width of the insulating layer is 200mm to 500mm, for example, it can be 200mm, 220mm, 240mm, 260mm, 280mm, 300mm, 325mm, 350mm, 370mm, 400mm, 425mm, 450mm, 480mm or 500mm, etc.

[0079] In one embodiment, the boehmite has a particle size <150nm, for example, it can be 145nm, 140nm, 130nm, 120nm, 110nm, 100nm, 90nm, 80nm, 70nm, 60nm, or 50nm. Within this range, the small particle size of the boehmite used as the main insulating material results in good particle size feedback in the slurry after dispersion, and allows it to be densely and uniformly spread on the substrate after coating, thereby achieving high insulation performance.

[0080] In one embodiment, the boehmite mass fraction is 50% to 80% based on the total mass of the insulating layer, for example, it can be 50%, 52%, 55%, 58%, 60%, 63%, 66%, 68%, 70%, 72%, 75%, 77%, or 80%, etc.

[0081] In one embodiment, the mass ratio of sodium polyacrylate to boehmite is 1:1 to 1:6, for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6. If the content of sodium polyacrylate is too low, it will lead to a loose coating structure and dispersion failure. Its role as a binder and auxiliary dispersant cannot be effectively exerted, causing the boehmite particles in the slurry to agglomerate and settle. The final coating has poor adhesion, is not dense, has reduced insulation performance, and reduces the protective effect of the edge coating. If the content of sodium polyacrylate is too high, it will cause over-coating and electrochemical risks. Excessive PAA-Na will compete for the active sites on the surface of boehmite particles, hindering the function of the core dispersant (phosphate ester polymer), and may even lead to agglomeration. At the same time, it will also introduce extremely strong hydrophilicity and a large number of sodium ions, making the coating prone to moisture absorption and triggering internal side reactions in the battery, which will endanger battery safety and life.

[0082] In one embodiment, the phosphate polymer accounts for 2% to 8% of the mass of the boehmite, for example, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%. If the content of the phosphate polymer is too low, it will not provide effective steric stabilization, and the boehmite nanoparticles in the slurry will agglomerate due to van der Waals forces, forming large secondary particles. This results in poor slurry dispersibility, easy sedimentation, and a rough, non-dense coating with defects and porosity after coating. The insulation performance (especially the critical penetration resistance) will be reduced, and it will not effectively prevent burr penetration. If the content of the phosphate polymer is too high, it will not only waste costs but also disrupt the chemical balance of the slurry system. Excessive phosphate polymer molecules may not be completely adsorbed and remain free in the slurry, increasing the viscosity and foaming properties of the slurry and affecting the coating process. More importantly, excessive phosphate polymers may form an overly thick adsorption layer on the boehmite surface, which increases the spatial resistance between particles or competes with the PAA-Na binder for adsorption, weakening the bonding strength and causing the coating adhesion to decrease, or even peel off from the current collector when drying or under stress.

[0083] In one embodiment, the current collector substrate includes a metal foil or a carbon-coated metal foil.

[0084] In one embodiment, the metal foil material includes at least one of aluminum, aluminum alloy, copper, and copper alloy.

[0085] In another embodiment of the present invention, a method for preparing the current collector as described above is provided, the method comprising the following steps:

[0086] Preparation of an insulating grout comprising boehmite, sodium polyacrylate, and phosphate polymer;

[0087] The insulating slurry is applied to at least one edge of at least one side surface of the current collector substrate and dried to obtain the current collector.

[0088] The preparation method of this invention is simple, has low preparation cost, and is conducive to widespread use.

[0089] In one embodiment, the method for preparing the slurry includes:

[0090] (1) Mix sodium polyacrylate with water to obtain a glue solution;

[0091] (2) Add phosphate polymer to the adhesive solution and stir to obtain the first slurry;

[0092] (3) Boehmite is added to the first slurry in multiple batches, and the mixture is stirred after each addition of boehmite to obtain the second slurry;

[0093] (4) Adjust the concentration and pH of the second slurry to obtain the insulating slurry.

[0094] In one embodiment, the sodium polyacrylate in step (1) is pre-adjusted to a pH of 7-9 before use, for example, 7, 7.2, 7.5, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8, or 9. By adjusting PAA-Na to alkaline, PAA-Na can be ionized into negatively charged polyacrylic acid chains (-COO). - (This) inhibits the agglomeration of boehmite particles through electrostatic repulsion.

[0095] In one embodiment, the pH of sodium polyacrylate is adjusted to 7-9 using a 0.1M NaOH solution.

[0096] In one embodiment, the solid content of the adhesive in step (1) is 15% to 25%, for example, it can be 15%, 16%, 18%, 20%, 22%, 23% or 25%, etc.

[0097] In one embodiment, the viscosity of the adhesive solution in step (1) is 800 mPa·s to 3000 mPa·s, for example, it can be 800 mPa·s, 1000 mPa·s, 1200 mPa·s, 1500 mPa·s, 1700 mPa·s, 1800 mPa·s, 2000 mPa·s, 2200 mPa·s, 2300 mPa·s, 2500 mPa·s, 2700 mPa·s or 3000 mPa·s, etc.

[0098] In one embodiment, in step (2), after adding the phosphate polymer, the stirring speed is 200 r / min to 600 r / min, for example, it can be 200 r / min, 220 r / min, 240 r / min, 260 r / min, 280 r / min, 300 r / min, 325 r / min, 350 r / min, 370 r / min, 380 r / min, 400 r / min, 425 r / min, 450 r / min, 500 r / min, 525 r / min, 550 r / min, 570 r / min or 600 r / min, etc.; the stirring time is 15 min to 25 min, for example, it can be 15 min, 17 min, 18 min, 20 min, 22 min, 23 min or 25 min, etc.

[0099] In one embodiment, in step (3), after each addition of boehmite, the stirring speed is independently 2000 r / min to 2600 r / min, for example, it can be 2000 r / min, 2050 r / min, 2100 r / min, 2150 r / min, 2200 r / min, 2250 r / min, 2300 r / min, 2350 r / min, 2400 r / min, 2450 r / min, 2500 r / min, 2550 r / min or 2600 r / min, etc.; the stirring time is 10 min to 90 min, for example, it can be 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min, etc.

[0100] In one embodiment, in step (4), the concentration of the slurry is adjusted so that the solid content is 3% to 8%, for example, it can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%, etc.

[0101] In one implementation, in step (4), the pH is adjusted to 6-8, for example, it can be 6, 6.2, 6.4, 6.5, 6.6, 6.7, 6.8, 7, 7.2, 7.3, 7.5, 7.7 or 8, etc.

[0102] In one embodiment, the preparation method further includes step (5), which includes: after adjusting the concentration and pH of the second slurry, adding a wetting agent to the slurry and stirring to obtain a third slurry.

[0103] In one embodiment, the wetting agent accounts for 8% to 12% of the total mass of the second slurry, for example, it can be 8%, 9%, 10%, 11% or 12%, etc.

[0104] In one embodiment, the preparation method further includes homogenizing the second slurry or the third slurry.

[0105] In one embodiment, the pressure of the homogenization process is 500 bar to 800 bar, for example, it can be 500 bar, 550 bar, 600 bar, 650 bar, 700 bar, 750 bar or 800 bar.

[0106] In another embodiment of the present invention, an electrode is provided, the electrode comprising the above-described current collector and an active material layer disposed on at least one side surface of the current collector.

[0107] In another embodiment of the present invention, an electrochemical device is provided, the electrochemical device comprising the above-described current collector or the above-described electrode.

[0108] The following are typical but non-limiting implementation methods:

[0109] Preparation Example 1

[0110] A method for preparing a phosphate ester polymer is provided, comprising the following steps:

[0111] ① Dehydration of polyethylene glycol: Dehydrate polyethylene glycol under vacuum (pressure -0.1MPa) conditions at 100℃ for 2 hours, and set aside for later use;

[0112] ② Esterification reaction: Under nitrogen protection, polyethylene glycol is added to a three-necked flask, the temperature is raised to 60°C, and phosphorus pentoxide is slowly added. The molar ratio of polyethylene glycol to phosphorus pentoxide is 1:(1~1.5). The reaction temperature is controlled at less than or equal to 80°C, and the reaction time is 6 hours. During this period, an equal volume of deionized water is added dropwise every 1 hour to promote hydrolysis.

[0113] ③ Neutralization and purification: After the reaction product is cooled to room temperature, the pH is adjusted to 9-10 with 0.1mM NaOH, and then the small molecule phosphate is removed by washing with a large amount of anhydrous ethanol. The product is then freeze-dried at -10℃ to obtain the phosphate ester polymer.

[0114] Preparation Example 2

[0115] A method for preparing sodium polyacrylate (PAA-Na) includes the following steps:

[0116] (A) Polymerization reaction:

[0117] ① Preparation of premixed solution: Mix acrylic acid and deionized water in a beaker and stir at 600 r / min for 20 min on a magnetic stirrer to obtain glue with a solid content of 22%; after stirring, add a small amount of isopropanol to adjust the tension of the solution to obtain a premixed solution.

[0118] ②Initiator preparation: Dissolve ammonium persulfate in deionized water and stir on a magnetic stirrer at 1500 r / min for 30 min until completely dissolved to obtain a 1M ammonium persulfate solution;

[0119] ③ Under nitrogen protection, add the premixed solution to a three-necked flask, heat to 70℃, and slowly add ammonium persulfate solution (completely over 30 minutes). Maintain the temperature for 3 hours for polymerization. ④ Endpoint determination: The viscosity of the reaction solution increases significantly, reaching 500 mPa·s or higher when measured on a viscometer.

[0120] (B) Neutralization reaction:

[0121] ① Cooling and dilution: Cool the polymerized binder to 40°C and dilute it with water until the viscosity is reduced to less than or equal to 100 mPa·s;

[0122] ② Partial neutralization: Add 0.1mM NaOH solution dropwise, keeping the temperature below 50℃, until pH=8.0. Note: Monitor in real time with a pH meter to avoid localized over-alkalinity leading to hydrolysis.

[0123] Example 1

[0124] This embodiment provides a current collector, including a current collector substrate (copper foil), the current collector substrate having a first surface and a second surface disposed opposite to each other, and an insulating layer (with a single-sided thickness of 2 μm and a coating width of 300 mm) is disposed at the edges of the first surface and the second surface. The insulating layer includes boehmite, sodium polyacrylate and phosphate polymer. Based on the total mass of the insulating layer, the mass fraction of boehmite is 80%, the mass of phosphate polymer accounts for 8% of the mass of boehmite, and the mass ratio of sodium polyacrylate to boehmite is 1:5.8.

[0125] This embodiment also provides a method for preparing the above-mentioned current collector, including the following steps:

[0126] S1. Deionized water was mixed with PAA-Na adhesive (Preparation Example 2) to obtain an adhesive solution with a solid content of 20% and a viscosity of 1000 mPa·s;

[0127] S2 Add the adhesive solution to a 200L double planetary mixing tank, then add the phosphate polymer (Preparation Example 1), and disperse at a low speed of 400r / min for 20min to obtain the first slurry;

[0128] S3. Add one-third of the total boehmite mass to the first slurry and disperse at a high speed of 2300 r / min for 10 min; then add another one-third of the total boehmite mass and disperse at a high speed of 2300 r / min for 20 min; then add the remaining boehmite and disperse at a high speed of 2300 r / min for 90 min. Add an appropriate amount of deionized water to reduce the slurry concentration to a solid content of 5% and disperse at a high speed of 2500 r / min for 30 min. Then add a pH adjuster (0.5 mM sodium hydroxide solution) to adjust the pH to 7 to obtain the second slurry.

[0129] S4 Add wetting agent (isopropanol solution, the amount added is 8% of the total mass of the second slurry), stir at low speed of 10 r / min for 40 min, and then homogenize the obtained slurry twice in a homogenizer at a pressure of 600 bar to obtain insulating slurry.

[0130] S5 uses a gravure coating method to evenly coat the insulating paste on the edges of both sides of the current collector, and after drying, a current collector with high insulation can be obtained.

[0131] Example 2

[0132] This embodiment provides a current collector, including a current collector substrate (copper foil), the current collector substrate having a first surface and a second surface disposed opposite to each other, and an insulating layer (with a single-sided thickness of 1 μm and a coating width of 400 mm) is disposed at the edges of the first surface and the second surface. The insulating layer includes boehmite, sodium polyacrylate and phosphate polymer. Based on the total mass of the insulating layer, the mass fraction of boehmite is 55%, the mass of phosphate polymer accounts for 5% of the mass of boehmite, and the mass ratio of sodium polyacrylate to boehmite is 1:1.3.

[0133] This embodiment also provides a method for preparing the above-mentioned current collector, including the following steps:

[0134] The preparation of the insulating coating current collector slurry includes the following steps:

[0135] S1. Deionized water was mixed with PAA-Na adhesive (Preparation Example 2) to obtain an adhesive solution with a solid content of 15% and a viscosity of 800 mPa·s.

[0136] S2 Add the adhesive solution to a 200L double planetary mixing tank, then add the phosphate polymer (Preparation Example 1), and disperse at a low speed of 200r / min for 25min to obtain the first slurry;

[0137] S3. Add one-third of the total boehmite mass to the first slurry and disperse at a high speed of 2000 r / min for 40 min; then add another one-third of the total boehmite mass and disperse at a high speed of 2500 r / min for 20 min; then add the remaining boehmite and disperse at a high speed of 2300 r / min for 60 min. Add an appropriate amount of deionized water to reduce the slurry concentration to a solid content of 5% and disperse at a high speed of 2200 r / min for 30 min. Then add a pH adjuster (0.5 mM sodium hydroxide solution) to adjust the pH to 7 to obtain the second slurry.

[0138] S4 Add wetting agent (isopropanol solution, the amount added is 12% of the total mass of the second slurry), stir at low speed of 15 r / min for 40 min, and then homogenize the obtained slurry twice in a homogenizer at a pressure of 500 bar to obtain insulating slurry.

[0139] S5 uses a gravure coating method to evenly coat the insulating paste on the edges of both sides of the current collector, and after drying, a current collector with high insulation can be obtained.

[0140] Example 3

[0141] This embodiment provides a current collector, including a current collector substrate (copper foil), the current collector substrate having a first surface and a second surface disposed opposite to each other, and an insulating layer (with a single-sided thickness of 3 μm and a coating width of 200 mm) is disposed at the edges of the first surface and the second surface. The insulating layer includes boehmite, sodium polyacrylate and phosphate polymer. Based on the total mass of the insulating layer, the mass fraction of boehmite is 70%, the mass of phosphate polymer accounts for 3% of the mass of boehmite, and the mass ratio of sodium polyacrylate to boehmite is 1:2.5.

[0142] This embodiment also provides a method for preparing the above-mentioned current collector, including the following steps:

[0143] S1. Deionized water was mixed with PAA-Na adhesive (Preparation Example 2) to obtain an adhesive solution with a solid content of 25% and a viscosity of 3000 mPa·s.

[0144] S2 Add the adhesive solution to a 200L double planetary mixing tank, then add the phosphate polymer (Preparation Example 1), and disperse at a low speed of 600r / min for 15min to obtain the first slurry;

[0145] S3. Add one-third of the total boehmite mass to the first slurry and disperse at a high speed of 2600 r / min for 10 min; then add another one-third of the total boehmite mass and disperse at a high speed of 2250 r / min for 40 min; then add the remaining boehmite and disperse at a high speed of 2000 r / min for 20 min. Add an appropriate amount of deionized water to reduce the slurry concentration to a solid content of 5% and disperse at a high speed of 2300 r / min for 30 min. Then add a pH adjuster (0.5 mM sodium hydroxide solution) to adjust the pH to 7 to obtain the second slurry.

[0146] S4 Add wetting agent (isopropanol solution, the amount added is 10% of the total mass of the second slurry), stir at low speed of 20 r / min for 30 min, and then homogenize the obtained slurry twice in a homogenizer at a pressure of 800 bar to obtain insulating slurry.

[0147] S5 uses a gravure coating method to evenly coat the insulating paste on the edges of both sides of the current collector, and after drying, a current collector with high insulation can be obtained.

[0148] Example 4

[0149] The difference from Example 1 is that the phosphate polymer accounts for 5% of the mass of the boehmite.

[0150] Example 5

[0151] The difference from Example 1 is that the phosphate ester polymer accounts for 3% of the mass of the boehmite.

[0152] Example 6

[0153] The difference from Example 1 is that the phosphate ester polymer accounts for 1% of the mass of the boehmite.

[0154] Example 7

[0155] The difference from Example 1 is that the mass ratio of sodium polyacrylate to boehmite is 2:1.

[0156] Example 8

[0157] The difference from Example 1 is that the mass ratio of sodium polyacrylate to boehmite is 1:7.

[0158] Example 9

[0159] The difference from Example 1 is that the thickness of the insulating layer on one side is 0.5 μm.

[0160] Comparative Example 1

[0161] The difference from Example 1 is that the PAA-Na adhesive is replaced with polyacrylic acid (PAA).

[0162] Comparative Example 2

[0163] The difference from Example 1 is that the insulating layer does not contain phosphate polymers.

[0164] Performance testing of the current collector:

[0165] The current collectors of Examples 1-9 and Comparative Examples 1-2 were cut into strips 20cm long and 5cm wide. The surface sheet resistance of the strips was tested using a four-probe sheet resistance meter. The new strips were then cut into 5cm×5cm samples, and the transmission resistance was tested using a diaphragm resistance meter. The data were recorded in Table 1.

[0166]

[0167] As shown in Table 1, the current collector of the present invention has an insulating layer at the edge. By utilizing the synergistic effect of boehmite, sodium polyacrylate and phosphate polymer in the insulating layer, the dispersion of boehmite can be improved, making the coating uniform and complete, thereby effectively improving the insulation performance of the insulating layer and thus improving the safety performance of the battery.

[0168] A comparison of Examples 1 and 4-6 shows that when the mass of the phosphate ester polymer accounts for 2% to 8% of the boehmite mass, the insulation performance of the insulating layer is improved more effectively. In Example 6, the amount of phosphate ester polymer was too small, resulting in poor dispersion of boehmite in the insulating layer, thus reducing its insulation performance. Comparative Example 2, which did not contain phosphate ester polymer, showed even worse insulation performance.

[0169] A comparison of Example 1 with Examples 7-8 and Comparative Example 1 shows that the introduction of sodium polyacrylate is necessary, and the insulation performance of the insulating layer is better when the mass ratio of sodium polyacrylate to boehmite is 1:1 to 1:6.

[0170] A comparison between Example 1 and Example 9 shows that the thickness of one side of the insulating layer should not be too thin, otherwise the insulating performance of the insulating layer will be reduced.

[0171] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A current collector, characterized in that, The current collector includes a current collector substrate having a first surface and a second surface disposed opposite to each other, and an insulating layer is disposed on at least one edge of the first surface and / or the second surface, the insulating layer comprising boehmite, sodium polyacrylate and phosphate polymer.

2. The current collector according to claim 1, characterized in that, The thickness of the insulating layer on one side is 1 μm to 3 μm; preferably, the width of the insulating layer is 200 mm to 500 mm; preferably, the particle size of the boehmite is <150 nm; preferably, based on the total mass of the insulating layer, the mass fraction of the boehmite is 50% to 80%; preferably, the mass ratio of the sodium polyacrylate to the boehmite is 1:1 to 1:6; preferably, the mass of the phosphate polymer accounts for 2% to 8% of the mass of the boehmite.

3. The current collector according to claim 1 or 2, characterized in that, The current collector substrate includes metal foil or carbon-coated metal foil; preferably, the metal foil is made of at least one of aluminum, aluminum alloy, copper and copper alloy.

4. A method for preparing a current collector as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: preparing an insulating slurry comprising boehmite, sodium polyacrylate and phosphate polymer; applying the insulating slurry to at least one edge of at least one side surface of the current collector substrate, and drying it to obtain a current collector.

5. The method for preparing a current collector according to claim 4, characterized in that, The preparation method of the slurry includes: (1) mixing sodium polyacrylate with water to obtain a slurry; (2) adding a phosphate polymer to the slurry and stirring to obtain a first slurry; (3) adding boehmite to the first slurry in multiple batches, stirring after each addition of boehmite to obtain a second slurry; (4) adjusting the concentration and pH of the second slurry to obtain the insulating slurry.

6. The method for preparing a current collector according to claim 4 or 5, characterized in that, The sodium polyacrylate in step (1) is pre-adjusted to pH 7-9 before use; preferably, the solid content of the adhesive in step (1) is 15%-25%; preferably, the viscosity of the adhesive in step (1) is 800 mPa·s-3000 mPa·s; preferably, in step (2), after adding the phosphate polymer, the stirring speed is 200 r / min-600 r / min, and the stirring time is 15 min-25 min; preferably, in step (3), after each addition of boehmite, the stirring speed is independently 2000 r / min-2600 r / min, and the stirring time is 10 min-90 min; preferably, in step (4), the concentration of the slurry is adjusted so that the solid content is 3%-8%; preferably, in step (4), the pH is adjusted to 6-8.

7. The method for preparing a current collector according to any one of claims 4-6, characterized in that, The preparation method further includes step (5), which includes: after adjusting the concentration and pH of the second slurry, adding a wetting agent to the slurry and stirring to obtain a third slurry; preferably, the wetting agent accounts for 8% to 12% of the total mass of the second slurry.

8. The method for preparing a current collector according to any one of claims 4-7, characterized in that, The preparation method further includes homogenizing the second slurry or the third slurry; preferably, the pressure of the homogenization process is 500 bar to 800 bar.

9. An electrode sheet, characterized in that, The electrode includes a current collector as described in any one of claims 1-3 and an active material layer disposed on at least one side surface of the current collector.

10. An electrochemical device, characterized in that, The electrochemical device includes the current collector as described in any one of claims 1-3, or the electrode as described in claim 9.

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