Binder as well as preparation method and application thereof

Abstract

The invention relates to a binder as well as a preparation method and application thereof. The binder comprises a polyacrylic acid matrix, a conductive polymer, functional nanoparticles and a cross-linking agent, the mass fraction of the polyacrylic acid matrix in the binder is 69.5%-79.5%; the mass fraction of the conductive polymer in the binder is 10%-15%; the mass fraction of the functional nanoparticles in the binder is 5%-15%; the mass fraction of the cross-linking agent in the binder is 0.3%-1%; wherein the functional nanoparticles are nanoparticles of which the surfaces are modified by amino groups. According to the scheme provided by the invention, the binder has excellent conductivity, high-voltage oxidation resistance and compatibility with residual lithium on the surface of a high-nickel positive electrode, the interface bonding force with a high-nickel positive electrode active material can be improved, and the contact resistance of a positive electrode interface can be reduced, so that the battery can present excellent cycle performance and rate capability.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to binders, their preparation methods, and applications. Background Technology

[0002] Lithium-ion batteries are widely used in 3C digital products, power tools, aerospace, energy storage, and electric vehicles due to their advantages such as high specific energy, no memory effect, and long cycle life. The rapid development of electronic information technology and consumer products has placed higher demands on the electrochemical performance of lithium-ion batteries.

[0003] The positive electrode sheet is made by coating a positive electrode slurry containing a binder onto a positive electrode current collector, where the binder is crucial for maintaining the stability of the coating. Traditional fluorinated binders (such as PVDF) not only face severe environmental and energy consumption challenges due to their reliance on toxic N-methylpyrrolidone (NMP) solvents and high-temperature drying processes, but also have inherent defects such as weak interfacial bonding with high-nickel positive electrodes (such as NCM811), poor resistance to high-voltage oxidation, and a surge in cycle resistance. These defects easily lead to the stripping of electrode active materials and the aggravation of side reactions. In addition, they are prone to reacting with residual lithium on the high-nickel surface to undergo defluorination and hydrogen fluoride reaction, causing premature gelation of the positive electrode slurry, which in turn destroys the coating uniformity and integrity. The synergistic effect of these multiple failure mechanisms significantly degrades the long-cycle and high-rate performance of the battery, and has become a key bottleneck restricting the breakthrough of next-generation high-energy lithium battery technology.

[0004] Therefore, there is an urgent need to develop a new type of binder to synergistically improve the cycle performance and rate performance of high-nickel batteries. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this application provides a binder, its preparation method, and its application. This binder has excellent conductivity, high-pressure oxidation resistance, and compatibility with residual lithium on the surface of high-nickel cathodes. It can enhance the interfacial bonding force with high-nickel cathode active materials and reduce the cathode interfacial contact resistance, thereby enabling the battery to exhibit excellent cycle performance and rate performance.

[0006] The first aspect of this application provides an adhesive, wherein the adhesive comprises a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent; The polyacrylic acid matrix comprises 69.5% to 79.5% by mass in the adhesive; the conductive polymer comprises 10% to 15% by mass in the adhesive; the functional nanoparticles comprise 5% to 15% by mass in the adhesive; and the crosslinking agent comprises 0.3% to 1% by mass in the adhesive. The functional nanoparticles are nanoparticles with amino-modified surfaces.

[0007] The adhesive as described in the first aspect, wherein the polyacrylic acid matrix has the structural formula shown in Formula 1: Formula 1 Where, n:m = (8.5:1.5) ~ (9.5:0.5); And / or, the molecular weight of the polyacrylic acid matrix is ​​5 × 10⁻⁶. 4 g / mol ~ 8 × 10 4 g / mol; And / or, the hydroxyl content in the polyacrylic acid matrix is ​​1.2 mmol / g to 1.5 mmol / g.

[0008] The adhesive as described in the first aspect, wherein the conductive polymer comprises at least one of poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), polyethylene glycol modified poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), and carboxyl-functionalized poly(3,4-ethylenedioxythiophene). And / or, the conductivity of the conductive polymer aqueous solution with a mass fraction of 1.0wt%~1.5wt% is not less than 100S / m.

[0009] The adhesive as described in the first aspect, wherein the functional nanoparticles include at least one of cerium dioxide with an amino-modified surface, aluminum oxide with an amino-modified surface, titanium dioxide with an amino-modified surface, zirconium oxide with an amino-modified surface, and iron oxide with an amino-modified surface. And / or, the particle size of the functional nanoparticles is 20 nm to 50 nm; And / or, the amino content in the functional nanoparticles is 0.8 mmol / g to 1.2 mmol / g; And / or, the electrochemical stability window of the functional nanoparticles is not less than 4.8V; And / or, the crosslinking agent includes at least one of adipate dihydrazide, polyethylene glycol dihydrazide, and succinate dihydrazide.

[0010] A second aspect of this application provides a method for preparing an adhesive as described in the first aspect, comprising the following steps: The polyacrylic acid matrix, the conductive polymer, the functional nanoparticles, and the crosslinking agent are mixed in an aqueous solvent according to the corresponding mass fractions to obtain the adhesive. The mixing temperature of the mixing process is 50℃~70℃, and the mixing time is 1h~3h.

[0011] The method for preparing the adhesive as described in the second aspect, wherein the polyacrylic acid matrix is ​​obtained by the following steps: An initiator is added to an aqueous solution containing acrylic acid and 2-hydroxyethyl acrylate, and polymerization is carried out to obtain the polyacrylic acid matrix; Preferably, the initiator includes at least one of ammonium persulfate, sodium persulfate, and potassium persulfate; Preferably, the initiator has a mass fraction of 0.1% to 0.8% in the aqueous solution system comprising the acrylic acid and the 2-hydroxyethyl acrylate; Preferably, the polymerization reaction is carried out at a temperature of 60°C to 70°C and for a reaction time of 1 to 5 hours.

[0012] A third aspect of this application provides a positive electrode sheet, wherein the positive electrode sheet includes a positive current collector and a positive electrode coating loaded on at least one side of the positive current collector, the positive electrode coating including an adhesive as described in the first aspect or an adhesive prepared by a method for preparing an adhesive as described in the second aspect.

[0013] As described in the third aspect, the positive electrode sheet, wherein the positive electrode coating comprises a positive electrode active material, a conductive agent, and the binder; the mass ratio of the positive electrode active material, the conductive agent, and the binder is (90~94):(3~5):(2~4). Preferably, the chemical formula of the positive electrode active material is LiNi. x Co y Mn 1-x-y O2, x≥0.8.

[0014] As described in the third aspect, the positive electrode sheet wherein the peel strength between the positive electrode coating and the positive electrode current collector is not less than 2 N / m; And / or, the interfacial contact resistance between the positive electrode coating and the positive electrode current collector is not higher than 30 mΩ. cm 2 ; And / or, the positive electrode slurry used to prepare the positive electrode coating has a viscosity change rate of less than 5% after standing storage for 72 hours.

[0015] A fourth aspect of this application provides a battery, wherein the battery includes a positive electrode as described in the third aspect.

[0016] The technical solution provided in this application can include the following beneficial effects: the polyacrylic acid matrix, conductive polymer, functional nanoparticles, and crosslinking agent in the binder work synergistically. By controlling the mass percentage of these four components, an integrated synergistic system of chemical anchoring, electronic conduction, mechanical interlocking, and network stabilization is constructed: the polyacrylic acid matrix utilizes dense hydroxyl groups to form strong coordination bonds with active metal ions, achieving strong anchoring at the chemical level; the conductive polymer is molecularly dispersed inside the electrode to construct a three-dimensional interconnected "cross-component network," filling the gaps in electron transport and reducing the interfacial impedance of the battery; the functional nanoparticles achieve physical interlocking by filling pores and buffering stress, and also capture active oxygen with amino functional groups to inhibit high-pressure oxidative decomposition; the crosslinking agent induces the matrix to self-crosslink to form a dense three-dimensional skeleton, physically locking the above functional components and overcoming the inherent defects of linear binders. The synergistic effect of these four components creates a stable electrode interface, which not only effectively inhibits electrode delamination and microcrack propagation, achieving a balance between low interfacial impedance and high structural stability, but also provides excellent chemical compatibility and aqueous dispersion characteristics. This avoids the problem of slurry gelation caused by the defluorination reaction between traditional binders and residual lithium on the surface of high-nickel cathodes. In addition to eliminating the pollution of toxic solvents, it significantly improves the stability of the battery during long cycles and its high-rate charge and discharge performance.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0018] To facilitate understanding of this application, it will be described in detail below. However, before describing this application in detail, it should be understood that this application is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be restrictive.

[0019] Where a numerical range is provided, it should be understood that every intermediate value between the upper and lower limits of the range and any other specified or intermediate value within the specified range is covered within this application. The upper and lower limits of these smaller ranges may be independently included in the smaller range and are also covered within this application, subject to any explicitly excluded limits within the specified range. Where the specified range includes one or two limits, the range excluding any or both of those included limits is also included within this application.

[0020] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While the methods and materials described herein, or any equivalent methods and materials, may also be used in the implementation or testing of this application, preferred methods and materials are now described.

[0021] The positive electrode sheet is made by coating a positive electrode slurry containing a binder onto a positive electrode current collector, where the binder is crucial for maintaining the stability of the coating. Traditional fluorinated binders (such as PVDF) not only face severe environmental and energy consumption challenges due to their reliance on toxic N-methylpyrrolidone (NMP) solvents and high-temperature drying processes, but also have inherent defects such as weak interfacial bonding with high-nickel positive electrodes (such as NCM811), poor resistance to high-voltage oxidation, and a surge in cycle resistance. These defects easily lead to the stripping of electrode active materials and the aggravation of side reactions. In addition, they are prone to reacting with residual lithium on the high-nickel surface to undergo defluorination and hydrogen fluoride reaction, causing premature gelation of the positive electrode slurry, which in turn destroys the coating uniformity and integrity. The synergistic effect of these multiple failure mechanisms significantly degrades the long-cycle and high-rate performance of the battery, and has become a key bottleneck restricting the breakthrough of next-generation high-energy lithium battery technology.

[0022] To address the aforementioned issues, this application provides an adhesive comprising a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent; the polyacrylic acid matrix comprises 69.5% to 79.5% by mass; the conductive polymer comprises 10% to 15% by mass; the functional nanoparticles comprise 5% to 15% by mass; and the crosslinking agent comprises 0.3% to 1% by mass; wherein the functional nanoparticles are nanoparticles with amino-modified surfaces.

[0023] The polyacrylic acid matrix of this application refers to a polymer material with polyacrylic acid segments as the basic structural unit. The densely distributed active hydroxyl groups in the polyacrylic acid matrix can act as powerful electron donors, specifically interacting with metal ions (such as Ni, Co, Mn, etc.) exposed on the surface of high-nickel cathode active materials to form a stable and dense coordination bond network. This chemical anchoring effect significantly enhances the interfacial bonding force between the binder and the cathode active particles, effectively suppressing particle delamination and microcrack propagation during cycling.

[0024] The conductive polymer of this application refers to a class of polymers with conductive properties. It has high conductivity and can be dispersed at the molecular level inside the electrode to construct a three-dimensional interconnected "cross-component network". This network can not only accurately fill the electron transport gap between the active material and the conductive agent like "molecular wires" and eliminate the transport dead zone in the traditional point contact mode, but also effectively penetrate to the microscopic defects on the surface of the active material, significantly reducing the contact resistance between particles and the interfacial charge transfer impedance, thereby greatly improving the rate performance of the battery.

[0025] The functional nanoparticles of this application are amino-modified nanoparticles. These nanoparticles can not only precisely fill the nanopores between the positive electrode active materials, achieving a tight physical interlock by increasing the interfacial contact area and frictional resistance, but also effectively disperse the mechanical stress caused by volume expansion and contraction during long-term battery cycling, preventing the electrode structure from pulverizing and peeling off. At the same time, this mechanical anchoring effect based on physical locking and the chemical coordination bonds provided by the polyacrylic acid matrix form a complementary "dual protection" system, namely a synergistic network of physical interlocking and chemical bonding, which greatly improves the structural integrity and bonding strength of the electrode interface, thereby significantly improving the cycle stability of the high-nickel positive electrode under harsh conditions. In addition, the amino functional groups on the surface of the functional nanoparticles have excellent free radical scavenging ability, which can efficiently quench reactive oxygen species generated at high potentials, thereby inhibiting the oxidative decomposition reaction at the interface of the binder and electrolyte from the source, ensuring the stability of the binder at high potentials.

[0026] The crosslinking agent of this application can induce intramolecular and intermolecular self-crosslinking reactions in the polyacrylic acid matrix to construct a dense and stable three-dimensional covalent network framework. This allows the conductive polymer and functional nanoparticles to be firmly locked in the three-dimensional network through physical blocking, encapsulation, or mechanical interlocking. This overcomes the inherent defects of traditional linear binders in terms of electrolyte swelling resistance, mechanical modulus, and interfacial bonding, and synergistically improves the high conductivity of the conductive polymer and the strong mechanical anchoring effect provided by the functional nanoparticles, ultimately improving the cycle life of the battery.

[0027] The adhesive of this application contains a polyacrylic acid matrix with a mass fraction of 69.5% to 79.5%, for example, the mass fraction of the polyacrylic acid matrix can be 69.5%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 79.5%, etc.

[0028] The conductive polymer in the adhesive of this application has a mass fraction of 10% to 15%, for example, the mass fraction of the conductive polymer can be 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0029] The mass fraction of functional nanoparticles in the binder of this application is 5% to 15%, for example, the mass fraction of functional nanoparticles can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0030] The crosslinking agent in the adhesive of this application has a mass fraction of 0.3% to 1%, for example, the mass fraction of the crosslinking agent can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0031] In this application, the binder comprises a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent, which work synergistically. By controlling the mass percentage of these four components, an integrated synergistic system of chemical anchoring, electronic conduction, mechanical interlocking, and network stabilization is constructed: the polyacrylic acid matrix utilizes dense hydroxyl groups to form strong coordination bonds with active metal ions, achieving strong chemical anchoring; the conductive polymer is molecularly dispersed within the electrode to construct a three-dimensional interconnected "cross-component network," filling electron transport gaps and reducing the interfacial impedance of the battery; the functional nanoparticles achieve physical interlocking by filling pores and buffering stress, and also capture reactive oxygen species through amino functional groups to inhibit high-pressure oxidative decomposition; the crosslinking agent induces the matrix to self-crosslink, forming a dense three-dimensional framework that physically locks the above functional components, overcoming the inherent defects of linear binders. The synergistic effect of these four components creates a stable electrode interface, which not only effectively inhibits electrode delamination and microcrack propagation, achieving a balance between low interfacial impedance and high structural stability, but also provides excellent chemical compatibility and aqueous dispersion characteristics. This avoids the problem of slurry gelation caused by the defluorination reaction between traditional binders and residual lithium on the surface of high-nickel cathodes. In addition to eliminating the pollution of toxic solvents, it significantly improves the stability of the battery during long cycles and its high-rate charge and discharge performance.

[0032] In one specific embodiment, the polyacrylic acid matrix has the structural formula shown in Formula 1: Formula 1 Where, n:m = (8.5:1.5) ~ (9.5:0.5).

[0033] n:m can be 8.5:1.5, 8.6:1.4, 8.7:1.3, 8.8:1.2, 8.9:1.1, 9:1, 9.1:0.9, 9.2:0.8, 9.3:0.7, 9.4:0.6, 9.5:0.5, etc.

[0034] The polyurethane matrix of this application has densely distributed carboxyl and hydroxyl functional groups in its molecular structure, which act as powerful electron donors. These groups can undergo specific coordination reactions with metal ions exposed on the surface of high-nickel cathode active materials to form a stable and dense chemical anchoring network. This significantly enhances interfacial bonding and inhibits particle stripping during cycling. In addition, the abundant carboxyl and hydroxyl functional groups serve as active sites, providing sufficient reaction fulcrum for intramolecular / intermolecular self-crosslinking reactions induced by crosslinking agents. This allows for the construction of a three-dimensional covalent framework resistant to electrolyte swelling, ultimately improving the structural integrity, cycling performance, and rate performance of the electrode.

[0035] Specifically, the structural formula of the polyacrylic acid matrix of this application can be obtained by nuclear magnetic resonance spectroscopy (NMR).

[0036] In one specific embodiment, the molecular weight of the polyacrylic acid matrix is ​​5 × 10⁻⁶. 4 g / mol ~ 8 × 10 4 g / mol, for example, the molecular weight of the polyacrylic acid matrix can be 5 × 10 4 g / mol, 5.5×10 4 g / mol, 6×10 4 g / mol, 6.5×10 4 g / mol, 7×10 4 g / mol, 7.5×10 4 g / mol, 8×10 4 g / mol, etc. The polyacrylic acid matrix of this application has a moderate molecular weight, ensuring that sufficiently long molecular chains form a dense physical entanglement network between the positive electrode active material particles, thereby endowing the electrode with excellent mechanical strength and flexibility; at the same time, while ensuring good solution flowability and coating processability, it optimizes the effective coverage and coordination efficiency of carboxyl and hydroxyl functional groups on the positive electrode surface, promoting the formation of a strong chemical anchor between the binder and the positive electrode active material, thereby establishing a low-impedance, high-stability interfacial environment, ultimately enabling the battery to exhibit excellent cycle life and rate performance.

[0037] Specifically, the molecular weight of the polyacrylic acid matrix in this application can be obtained by gel permeation chromatography (GPC).

[0038] In one specific embodiment, the hydroxyl content in the polyacrylic acid matrix is ​​1.2 mmol / g to 1.5 mmol / g, for example, the hydroxyl content in the polyacrylic acid matrix can be 1.2 mmol / g, 1.25 mmol / g, 1.3 mmol / g, 1.35 mmol / g, 1.4 mmol / g, 1.45 mmol / g, 1.5 mmol / g, etc. The sufficient amount of hydroxyl groups in the polyacrylic acid matrix of this application can form a strong coordination effect with the transition metal oxides on the surface of the positive electrode active material, significantly improving the interfacial adhesion and mechanical interlocking strength between the binder and the positive electrode active material particles, ultimately significantly improving the structural integrity, cycle stability, and rate performance of the high-nickel positive electrode.

[0039] Specifically, the method for testing the hydroxyl content in the polyacrylic acid matrix of this application is a titration method, including the following steps: 1) Accurately weigh 0.2g~0.3g of dried polyacrylic acid matrix, place it in a 250mL Erlenmeyer flask, add 50mL of anhydrous ethanol, and sonicate for 30min until the system is clear; 2) Add 2~3 drops of phenolphthalein indicator, and titrate with 0.1mol / L sodium hydroxide standard solution until the solution turns light pink and does not fade for 30s, and record the volume V1 of sodium hydroxide standard solution consumed; 3) Take another portion of the same mass of polyacrylic acid matrix, place it in another Erlenmeyer flask, add 50mL of anhydrous ethanol to dissolve it, and then... Add 10 mL of acetylation reagent (acetic anhydride-pyridine volume ratio of 1:5), seal and place in a 60℃ water bath for 2 h, then cool to room temperature; 4) Add 20 mL of deionized water to the reaction solution in step 3), shake well and let stand for 10 min, add 2-3 drops of phenolphthalein indicator, titrate with 0.1 mol / L sodium hydroxide standard solution until a light pink color remains for 30 s, and record the volume consumed V2; 5) Calculate the hydroxyl content according to the formula: hydroxyl content (mmol / g) = (V2-V1)×C×1000 / m, where C is the concentration of sodium hydroxide standard solution (mol / L) and m is the sample mass (g).

[0040] In one specific embodiment, the conductive polymer includes at least one of poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate) (PEDOT:PSS), polyethylene glycol-modified poly(3,4-ethylenedioxythiophene) (PEDOT:PEG), poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate) (PEDOT:PSSNa), and carboxyl-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT-COOH). All of the above conductive polymers possess excellent water solubility, which eliminates the reliance on toxic organic solvents such as N-methylpyrrolidone in traditional binder preparation, enabling a green and safe binder manufacturing process. Simultaneously, these conductive polymers can utilize their high electronic conductivity to construct continuous electron transport channels between the positive electrode active material particles, reducing the battery's interfacial impedance and thus ensuring the battery's rate performance.

[0041] In one specific embodiment, the conductivity of the conductive polymer aqueous solution with a mass fraction of 1.0 wt% to 1.5 wt% is not less than 100 S / m. The conductive polymer is dispersed in water to form a conductive polymer aqueous solution with a mass fraction of 1.0 wt% to 1.5 wt%. The conductivity of the conductive polymer aqueous solution is tested using a conductivity meter. The conductivity of the conductive polymer aqueous solution ensures the high conductivity of the conductive polymer, enabling it to construct a three-dimensional interconnected "cross-component network" through molecular-level dispersion within the electrode. This significantly reduces the contact resistance and interfacial charge transfer impedance between positive electrode active material particles, ultimately improving the electrochemical performance of the battery.

[0042] In one specific embodiment, the functional nanoparticles include at least one of the following: cerium dioxide (CeO2-NH2) with amino-modified surface, aluminum oxide (Al2O3-NH2) with amino-modified surface, titanium dioxide (TiO2-NH2) with amino-modified surface, zirconium oxide (ZrO2-NH2) with amino-modified surface, and iron oxide (Fe3O4-NH2) with amino-modified surface. These functional nanoparticles possess high chemical stability and high mechanical strength. Furthermore, the amino groups on their surface can react with the carboxyl groups in the polyacrylic acid matrix, resulting in better bonding between the functional nanoparticles and the polyacrylic acid matrix. In addition, the amino-modified functional nanoparticles can adsorb active oxygen in the battery through electrostatic attraction, ensuring high potential stability of the binder, thereby enabling the battery to exhibit excellent cycle performance and rate performance.

[0043] In one specific embodiment, the particle size of the functional nanoparticles is 20 nm to 50 nm, for example, the particle size of the functional nanoparticles can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc. When the particle size of the functional nanoparticles is within the above range, the density of amino functional groups modified on the surface of the functional nanoparticles is greatly increased, thereby enhancing the interfacial reaction sites and bonding strength between the functional nanoparticles and the polyacrylic acid matrix; at the same time, it ensures that the functional nanoparticles can uniformly fill the micro-nano pores between the positive electrode active material particles, achieving a physically locked mechanical anchoring effect, preventing the electrode structure from pulverizing and peeling off, thereby improving the electrochemical performance of the battery.

[0044] Specifically, the particle size of the functional nanoparticles in this application can be obtained by laser particle size analysis.

[0045] In one specific embodiment, the amino content in the functional nanoparticles is 0.8 mmol / g to 1.2 mmol / g, for example, the amino content in the functional nanoparticles can be 0.8 mmol / g, 0.85 mmol / g, 0.9 mmol / g, 0.95 mmol / g, 1 mmol / g, 1.05 mmol / g, 1.1 mmol / g, 1.15 mmol / g, 1.2 mmol / g, etc. When the amino content in the functional nanoparticles is within the above range, the functional nanoparticles can better adsorb active oxygen in the battery, allowing the binder to maintain high stability at high potentials, thereby improving the cycle performance and rate performance of the battery.

[0046] Specifically, the method for testing the amino content in the functional nanoparticles of this application is a titration method, including the following steps: 1) Accurately weigh 0.25g of dried functional nanoparticles, place them in a 250mL Erlenmeyer flask, add 50mL of anhydrous ethanol, and ultrasonically disperse for 30min until the system is uniform and free of precipitate; 2) Add 2-3 drops of bromophenol blue indicator, and titrate with 0.1mol / L hydrochloric acid standard solution until the solution changes from blue to pale yellow and does not fade for 30s, and record the volume V of hydrochloric acid standard solution consumed; 3) Calculate the amino content according to the formula: Amino content (mmol / g) = (V×C×1000) / m, where C is the concentration of hydrochloric acid standard solution (mol / L), and m is the mass of nanoparticle sample (g).

[0047] In one specific embodiment, the electrochemical stability window of the functional nanoparticles is not lower than 4.8V, for example, the electrochemical stability window of the functional nanoparticles can be 4.8V, 4.9V, 5.0V, 5.1V, 5.2V, 5.3V, 5.4V, 5.5V, etc. The electrochemical stability window in this application refers to the potential range that the functional nanoparticles can withstand without oxidative or reductive decomposition. The inorganic oxide core in the functional nanoparticles itself has a wide bandgap and extremely high oxidation potential, maintaining electrochemical inertness without decomposition under strong oxidizing environments. Simultaneously, the surface amino modification can preferentially capture and quench reactive oxygen free radicals generated by electrolyte oxidation through its electron-rich characteristics, effectively blocking the chain oxidation reaction at high potentials. This ensures that the nanoparticles do not undergo electrochemical decomposition under harsh high-voltage conditions, thereby significantly widening and stabilizing the electrochemical stability window of the electrode interface, thus ensuring the stability of the electrode under high voltage and improving the cycle performance of the battery.

[0048] Specifically, the electrochemical stability window of the functional nanoparticles in this application is tested by cyclic voltammetry (CV), which includes the following steps: 1) A three-electrode system is used for testing. The working electrode is a glassy carbon electrode coated with functional nanoparticles (the functional nanoparticles are dispersed in anhydrous ethanol, sonicated for 15 min, and 5 μL is dropped onto the surface of the glassy carbon electrode and allowed to air dry). The reference electrode is a saturated calomel electrode, and the counter electrode is a platinum sheet electrode; 2) A 1.0 mol / L H2SO4 aqueous solution is used as the test electrolyte. Before the test, nitrogen gas is introduced into the electrolyte to remove oxygen for 30 min to avoid oxygen interference with the test results; 3) The test voltage range is set to 0~6.0V (vs calomel electrode), the scan rate is 50 mV / s, and the cyclic scan is performed for 3 cycles; 4) The CV curve is observed. When a significant oxidation peak appears on the curve and the peak current increases sharply, the corresponding voltage is the oxidation decomposition potential of the functional nanoparticles, and this oxidation decomposition potential is the electrochemical stability window of the functional nanoparticles.

[0049] In one specific embodiment, the crosslinking agent includes at least one of adipate dihydrazide, polyethylene glycol dihydrazide, and succinate dihydrazide. When the crosslinking agent is one of the above compounds, the compound induces intramolecular and intermolecular self-crosslinking reactions in the polyacrylic acid matrix, transforming the linear polyacrylic acid matrix into a crosslinked network with excellent mechanical properties and self-healing capabilities. This ensures the structural integrity of the electrode during long-term cycling, thereby significantly improving the cycle stability of the high-nickel battery.

[0050] The second aspect of this application provides a method for preparing an adhesive, comprising the following steps: mixing a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent in an aqueous solvent according to their respective mass fractions to obtain the adhesive.

[0051] Specifically, a polyacrylic acid matrix, a conductive polymer, and functional nanoparticles are dispersed in water to form an aqueous solution of the polyacrylic acid matrix, an aqueous solution of the conductive polymer, and an aqueous solution of the functional nanoparticles, respectively. After the aqueous solutions of the polyacrylic acid matrix, the conductive polymer, and the functional nanoparticles are mixed evenly according to the mass ratio, a crosslinking agent is added and the mixture is subjected to a mixing treatment to obtain an adhesive.

[0052] The mixing temperature of the mixing process in this application is 50℃~70℃, and the mixing time is 1h~3h. For example, the mixing temperature can be 50℃, 55℃, 60℃, 65℃, 70℃, etc., and the mixing time can be 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0053] This application does not limit the specific choice of conductive polymer; it can be selected according to actual needs.

[0054] This application does not limit the specific selection of functional nanoparticles; they can be selected according to actual needs.

[0055] This application does not limit the specific choice of crosslinking agent; it can be selected according to actual needs.

[0056] The adhesive prepared in this application has a solid content of 10% to 15% and a pH of 6.5 to 7.

[0057] The adhesive prepared by the method of this application includes a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, a crosslinking agent, and a solvent. The components of the adhesive, excluding the water solvent, are proportioned as follows: 69.5% to 79.5% polyacrylic acid matrix, 10% to 15% conductive polymer, 5% to 15% functional nanoparticles, and 0.3% to 1% crosslinking agent.

[0058] The binder preparation method provided in this application involves sequentially and uniformly dispersing a polyacrylic acid matrix, a conductive polymer, and functional nanoparticles. Subsequently, a crosslinking agent is used to crosslink the polyacrylic acid matrix into a three-dimensional network structure, while simultaneously fixing the conductive polymer and functional nanoparticles within this network structure, resulting in a binder with excellent stability. This binder achieves uniform distribution within the positive electrode coating, thereby comprehensively activating its core functions: on one hand, it significantly enhances the interfacial bonding force with the high-nickel positive electrode active material, effectively suppressing positive electrode coating peeling caused by volume expansion during long-cycle operation; on the other hand, its excellent electronic conductivity significantly reduces the contact resistance at the positive electrode interface, improving charge transport efficiency; furthermore, this binder possesses excellent high-voltage oxidation resistance, perfectly adapting to high-nickel positive electrode systems under 4.3-4.5V high-voltage conditions, ensuring the structural integrity and electrochemical stability of the battery under harsh environments. Moreover, this preparation method is simple, requires low-level equipment, and utilizes widely available raw materials, demonstrating promising prospects for industrial application.

[0059] In one specific embodiment, the polyacrylic acid matrix is ​​prepared by the following steps: an initiator is added to an aqueous solution containing acrylic acid and 2-hydroxyethyl acrylate, and polymerization is carried out to obtain the polyacrylic acid matrix. Specifically, acrylic acid and 2-hydroxyethyl acrylate are mixed in a certain proportion, and water is added to adjust the solid content to 30%; then, an initiator is added under a nitrogen protective atmosphere to initiate the polymerization reaction of the monomers, ultimately obtaining the polyacrylic acid matrix. Through the above steps, acrylic acid and 2-hydroxyethyl acrylate can be cross-linked, and a monomer chain reaction can be initiated under the action of the initiator to obtain a structurally regular polyacrylic acid matrix.

[0060] In one specific embodiment, the initiator includes at least one of ammonium persulfate, sodium persulfate, and potassium persulfate. Upon cleavage of the peroxy bond in ammonium persulfate (APS), sodium persulfate, and potassium persulfate, sulfate radicals are generated. These radicals possess extremely strong oxidizing properties and can rapidly attack the carbon-carbon double bonds in acrylic acid and 2-hydroxyethyl acrylate monomers, initiating a chain polymerization reaction in the aqueous phase, thereby preparing a polyacrylic acid matrix.

[0061] In one specific embodiment, the initiator has a mass fraction of 0.1% to 0.8% in the aqueous solution system comprising acrylic acid and 2-hydroxyethyl acrylate. For example, the mass fraction of the initiator in the aqueous solution system can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc. When the mass fraction of the initiator is within the above range, an appropriate amount of initiator can provide sufficient primary free radicals to initiate and maintain chain growth, ensuring complete reaction conversion; it can also effectively avoid the risk of explosive polymerization and polymer degradation caused by excessively rapid exothermic reaction by controlling the free radical generation rate, thereby improving the success rate of polyacrylic acid matrix synthesis.

[0062] In one specific embodiment, the polymerization reaction temperature is 60℃~70℃, and the reaction time is 1~5h. For example, the reaction temperature can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, etc., and the reaction time can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc. Controlling the polymerization reaction temperature and reaction time within the above range avoids both the reaction stagnation caused by low initiation efficiency at low temperatures and the risk of explosive polymerization and chain transfer side reactions caused by excessively rapid decomposition at high temperatures, thereby ensuring the successful preparation of the polyacrylic acid matrix.

[0063] A third aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive electrode coating loaded on at least one side of the positive current collector, wherein the positive electrode coating comprises the aforementioned binder or a binder prepared by the aforementioned binder preparation method. The structure of the negative electrode sheet of this positive electrode sheet is stable, which can improve the cycle performance and rate performance of the battery.

[0064] In one specific embodiment, the positive electrode coating includes a positive electrode active material, a conductive agent, and a binder; the mass ratio of the positive electrode active material, conductive agent, and binder is (90~94):(3~5):(2~4), for example, the mass ratio of the positive electrode active material, conductive agent, and binder can be 93:5:2, 92:5:3, 91:5:4, 93:4:3, 92:4:4, 94:4:2, 93:3:4, 94:3:3, etc. When the mass ratio of the positive electrode active material, conductive agent, and binder is within the above range, the positive electrode sheet can balance the energy density, rate performance, and structural integrity of the battery.

[0065] In one specific embodiment, the positive electrode active material has the chemical formula LiNi. x Co y Mn 1-x-y O2, x≥0.8. Using the above-mentioned positive electrode active material can effectively improve the battery's energy density, cycle performance, and rate performance.

[0066] In one specific embodiment, the peel strength between the positive electrode coating and the positive electrode current collector is not less than 2 N / m, for example, the peel strength can be 2 N / m, 2.1 N / m, 2.2 N / m, 2.3 N / m, 2.4 N / m, 2.5 N / m, etc. The peel strength between the positive electrode coating and the positive electrode current collector in this application is tested according to GB / T 2792-2014. When the peel strength between the positive electrode coating and the positive electrode current collector is within the above range, the positive electrode coating and the positive electrode current collector have excellent interfacial adhesion, avoiding the problem of positive electrode coating peeling that may occur during battery charge-discharge cycles, and improving the cycle stability of the battery.

[0067] In one specific embodiment, the interfacial contact resistance between the positive electrode coating and the positive electrode current collector is no higher than 30 mΩ. cm 2 For example, the interfacial contact resistance between the positive electrode coating and the positive electrode current collector can be 20mΩ. cm 2 22mΩ cm 2 24mΩ cm 2 26mΩ cm 2 28mΩ cm 2 30mΩ cm 2 The use of the above-mentioned binders can significantly reduce the interfacial contact resistance between the positive electrode coating and the positive electrode current collector, thereby reducing the battery impedance and resulting in better cycle performance and rate performance.

[0068] In one specific embodiment, the positive electrode slurry used to prepare the positive electrode coating exhibits a viscosity change rate of less than 5% after standing storage for 72 hours. The binder of this application does not undergo a dehydrofluorination reaction with residual lithium on the high-nickel positive electrode surface, thereby preventing gelation of the positive electrode slurry, ensuring coating uniformity, improving the stability of the positive electrode sheet, and enhancing the electrochemical performance of the battery.

[0069] In one specific embodiment, the preparation process of the positive electrode sheet includes: mixing positive electrode active material, conductive agent, binder and deionized water to prepare a positive electrode slurry with a solid content of 60% to 65%, coating it on at least one side of the positive electrode current collector, drying it at 50°C to 60°C for 2 hours, and rolling it to obtain the positive electrode sheet.

[0070] In one specific embodiment, the compaction density of the positive electrode coating is 3.8 g / cm³. 3 ~4.0g / cm 3 The thickness of the positive electrode coating is 80μm~100μm, for example, the compaction density of the positive electrode coating can be 3.8g / cm³. 3 3.85g / cm 3 3.9g / cm 3 3.95g / cm 3 4g / cm 3 The thickness of the positive electrode coating can be 80μm, 85μm, 90μm, 95μm, 100μm, etc. This compaction density and thickness ensure that the positive electrode coating is filled with a sufficient amount of positive electrode active material and retains sufficient pore connectivity to allow electrolyte wetting, ultimately enabling the battery to achieve excellent energy density, cycle performance, and rate performance.

[0071] In this application embodiment, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. Preferably, the positive electrode current collector is a metallic material.

[0072] In one specific embodiment, the conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and vapor-grown carbon fiber (VGCF).

[0073] A fourth aspect of this application provides a battery comprising the aforementioned positive electrode. This battery exhibits excellent cycle performance and rate performance.

[0074] In one embodiment, the battery further includes a negative electrode sheet, which includes a negative current collector and a negative electrode coating loaded on at least one side of the negative current collector.

[0075] In this embodiment, the negative electrode coating includes a negative electrode active material, a conductive agent, and a binder. This application does not limit the selection of the negative electrode active material; it can be selected according to actual needs. For example, natural graphite, artificial graphite, hard carbon, soft carbon, silicon-carbon composite materials, elemental silicon, and silicon-oxygen composite materials can be used as the negative electrode active material. The conductive agent and binder in the negative electrode coating of this application can be selected from conventional materials in the art.

[0076] In one specific embodiment, the battery of this application further includes an electrolyte, which includes a lithium salt and an organic solvent. The lithium salt and organic solvent are lithium salts and organic solvents known in the art that can be used in electrolytes to improve the electrochemical performance of the battery, and can be specifically set as needed.

[0077] In one specific embodiment, the lithium-ion battery further includes a separator. The embodiments of this application do not have any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effect of this application. It may include porous sheet-like or non-woven fabric-like materials with excellent liquid retention. The materials of the resin or glass fiber separator include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc., and can be set according to needs.

[0078] In one embodiment, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte.

[0079] In one specific embodiment, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0080] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.

[0081] This application does not impose any particular restrictions on the application fields of lithium-ion batteries, and they can be used in fields such as consumer batteries, power batteries for new energy vehicles, and energy storage batteries.

[0082] The present application will be further described in detail below through specific embodiments.

[0083] Example 1 1. Preparation of adhesive Preparation of polyacrylic acid matrix: Acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were mixed at a mass ratio of 9:1, dissolved in deionized water, and the solid content was controlled at 30%. Then, 0.5 wt% ammonium persulfate was added, and the polymerization reaction was carried out at 65°C for 4 h to obtain polyacrylic acid matrix.

[0084] After mixing the polyacrylic acid matrix aqueous solution, PEDOT:PSS aqueous solution, and CeO2-NH2 aqueous dispersion evenly, adipic acid dihydrazide (ADH) was added, and the mixture was stirred at 50°C for 1 hour to prepare an adhesive with a solid content of 12%.

[0085] The molecular weight of the polyacrylic acid matrix is ​​6×10. 4 The hydroxyl content is 1.3 mmol / g. The conductivity of a 1.3 wt% PEDOT:PSS aqueous solution is 110 S / m. The functional nanoparticles have a particle size of 30 nm, an amino modification amount of 1.0 mmol / g, and an electrochemical stability window of 5.2 V.

[0086] The adhesive contains, excluding water solvent, 75% polyacrylic acid matrix, 12% conductive polymer, 12.5% ​​functional nanoparticles, and 0.5% crosslinking agent.

[0087] 2. Preparation of the positive electrode sheet The positive electrode active material (NCM811), conductive carbon black (SP), and binder were mixed evenly at a mass ratio of 92:5:3, and then thoroughly stirred in water to obtain a positive electrode slurry with a solid content of 62% and a viscosity of 6500 mPa. The positive electrode slurry was uniformly coated onto one surface of a 12 μm thick modified aluminum foil (Ra = 1.0 μm), dried at 55 °C for 2 h, and then rolled to a compaction density of 3.9 g / cm³. 3 The positive electrode sheet is then obtained. The above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a positive electrode coating on both sides. The positive electrode sheet is then cut into 50mm×50mm sizes and electrode tabs are welded on for later use.

[0088] 3. Preparation of negative electrode sheet The active material (graphite), conductive agent (Super P), dispersant (CMC), and binder (SBR) were mixed in a ratio of 92:5:1:2 and a negative electrode slurry was obtained under vacuum stirring. The negative electrode slurry was uniformly coated onto the surface of a modified current collector, dried at 90°C, and rolled to obtain a negative electrode sheet with a coating thickness of 85 μm. The above steps were repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided negative electrode coating. The negative electrode sheet was cut into 50 mm × 50 mm pieces and tabs were welded on for later use.

[0089] 4. Preparation of electrolyte In an environment with a water content of less than 10 ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:3:4. Based on the total mass of the electrolyte, lithium hexafluorophosphate (LiPF6) was added to the solvent, dissolved, and mixed evenly. Then, electrolyte additives were added to obtain the electrolyte. The molar concentration of LiPF6 in the electrolyte was 1.2 mol / L, and the electrolyte additives included lithium difluorophosphate (LiPO2F2), with a mass fraction of 2% in the electrolyte.

[0090] 5. Manufacturing of lithium-ion batteries The positive and negative electrode sheets are stacked in sequence, and the stacked electrode sheets are wound with the separator to obtain the electrode assembly. The electrode assembly is placed in the pre-formed aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected, and the battery is obtained through vacuum sealing, settling, formation, and shaping processes.

[0091] The main difference between Examples 2-31, Comparative Examples 1-9 and Example 1 is the different parameters of the adhesive, as shown in Tables 1-3.

[0092] Table 1

[0093] Table 2

[0094] Table 3

[0095] Test case The following performance tests were performed on the batteries prepared in the examples and comparative examples: 1. Cyclic performance test In a constant temperature chamber at (25±2)℃, the lithium-ion battery was charged to 4.2V at a constant current and constant voltage of 0.5C, then charged to 0.05C at a constant voltage. After resting for 5 minutes, it was discharged to 3V at 0.5C. The capacity obtained in this step was taken as the initial capacity. Cyclic tests were performed using 1C charge / 1C discharge, and the capacity retention rate of the battery after 300 cycles was calculated.

[0096] Cycle capacity retention (%) = Discharge capacity at 300th cycle (mAh) / Discharge capacity at first cycle (mAh) × 100% The average cycle life of each group of 5 batteries is recorded in Table 4.

[0097] 2. Ratio Performance Test Rate performance test: The lithium-ion batteries were charged to 4.2V at 2C constant current and constant voltage in a constant temperature chamber at 25±2℃, with a cutoff current of 0.05C, and then discharged to 3.0V at 1C. The charge and discharge cycles were performed under the above conditions, and the cycle discharge capacity of the batteries was recorded. There were 5 batteries in each group.

[0098] High-rate charging capacity retention rate (%) = 0.5C discharge capacity (mAh) / 1.0C rate cycle discharge capacity (mAh) × 100% Five batteries were used in each group. The average capacity retention rate at 0.5C was taken and the results were recorded in section 4.

[0099] Table 4

[0100] As shown in Table 4, based on the comparison of Examples 1-7 and Comparative Examples 1-8, when the binder includes a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent; and the mass fraction of the polyacrylic acid matrix is ​​69.5%-79.5%, the mass fraction of the conductive polymer is 10%-15%, the mass fraction of the functional nanoparticles is 5%-15%, and the mass fraction of the crosslinking agent in the binder is 0.3%-1%, the binder can exhibit excellent conductivity, high-pressure oxidation resistance, and compatibility, thereby improving the interfacial bonding force with the high-nickel cathode active material, reducing the cathode interfacial contact resistance, and enabling the battery to exhibit better cycle performance and rate performance.

[0101] Based on the comparison of Examples 1, 8, 9 and Comparative Example 9, it can be seen that when the mixing temperature of the mixing treatment is 50℃~70℃ and the mixing time is 1h~3h, the performance of the binder can be improved, thereby further improving the electrochemical performance of the battery.

[0102] According to the comparison of Examples 1, 10-12, when the mass ratio of acrylic acid to 2-hydroxyethyl acrylate is in the range of (8.5:1.5) to (9.5:0.5), the polyacrylic acid matrix can be successfully prepared, thereby making the battery cycle performance and rate performance better.

[0103] As can be seen from the comparison of Examples 1 and 13, when ammonium persulfate and sodium persulfate are selected as initiators, polyacrylic acid matrix can be successfully prepared, laying the foundation for the subsequent preparation of binder and ensuring the high cycle stability and rate performance of the battery.

[0104] As can be seen from the comparison of Examples 1, 14-16, when the mass fraction of the initiator is 0.1% to 0.8%, the initiator can fully exert its function, enabling acrylic acid and 2-hydroxyethyl acrylate to undergo polymerization reaction, thus ensuring the preparation of polyacrylic acid matrix.

[0105] According to the comparison of Examples 1 and 17-19, when the polymerization reaction temperature is 60℃~70℃ and the reaction time is 1~5h, the polyacrylic acid matrix has better performance and can improve the cycle stability and rate performance of the battery to a greater extent.

[0106] Based on the comparison of Examples 1, 20, and 21, it can be seen that when the conductive polymers selected are poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), polyethylene glycol-modified poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), and carboxyl-functionalized poly(3,4-ethylenedioxythiophene), the conductivity of the binder is better, which is beneficial to improving the cycle performance and rate performance of the battery.

[0107] According to the comparison of Examples 1 and 22-24, when the functional nanoparticles are selected from cerium dioxide with amino-modified surface, aluminum oxide with amino-modified surface, titanium dioxide with amino-modified surface, zirconium oxide with amino-modified surface, and iron oxide with amino-modified surface, the functional nanoparticles have better chemical stability and mechanical strength, which can make the high potential stability of the binder higher, thereby making the battery exhibit better cycle performance and rate performance.

[0108] Based on the comparison of Examples 1 and 25-27, it can be seen that when the particle size of the functional nanoparticles is 20nm-50nm, the interfacial reaction sites and binding strength between the functional nanoparticles and the polyacrylic acid matrix are better, which helps to further improve the electrochemical performance of the battery.

[0109] According to the comparison of Examples 1, 28-30, when the amino content in the functional nanoparticles is 0.8 mmol / g to 1.2 mmol / g, the binder has higher stability at high potential.

[0110] As can be seen from the comparison of Examples 1 and 31, when the crosslinking agent is selected as adipate dihydrazide, polyethylene glycol dihydrazide, or succinate dihydrazide, the crosslinking agent can induce intramolecular and intermolecular self-crosslinking reactions in the polyacrylic acid matrix, which better ensures the structural integrity of the electrode in long cycles, thereby greatly improving the cycle stability of high-nickel batteries.

[0111] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An adhesive, characterized in that, The adhesive comprises a polyacrylic acid matrix, a conductive polymer, functional nanoparticles, and a crosslinking agent; The polyacrylic acid matrix comprises 69.5% to 79.5% by mass in the adhesive; the conductive polymer comprises 10% to 15% by mass in the adhesive; the functional nanoparticles comprise 5% to 15% by mass in the adhesive; and the crosslinking agent comprises 0.3% to 1% by mass in the adhesive. The functional nanoparticles are nanoparticles with amino-modified surfaces.

2. The adhesive according to claim 1, characterized in that, The polyacrylic acid matrix has the structural formula shown in Formula 1: Formula 1 Where, n:m = (8.5:1.5) ~ (9.5:0.5); And / or, the molecular weight of the polyacrylic acid matrix is ​​5 × 10⁻⁶. 4 g / mol ~ 8 × 10 4 g / mol; And / or, the hydroxyl content in the polyacrylic acid matrix is ​​1.2 mmol / g to 1.5 mmol / g.

3. The adhesive according to claim 1, characterized in that, The conductive polymer includes at least one of poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), polyethylene glycol modified poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)-poly(sodium styrene sulfonate), and carboxyl-functionalized poly(3,4-ethylenedioxythiophene). And / or, the conductivity of the conductive polymer aqueous solution with a mass fraction of 1.0wt%~1.5wt% is not less than 100S / m.

4. The adhesive according to claim 1, characterized in that, The functional nanoparticles include at least one of the following: cerium dioxide with amino-modified surface, aluminum oxide with amino-modified surface, titanium dioxide with amino-modified surface, zirconium oxide with amino-modified surface, and iron oxide with amino-modified surface. And / or, the particle size of the functional nanoparticles is 20 nm to 50 nm; And / or, the amino content in the functional nanoparticles is 0.8 mmol / g to 1.2 mmol / g; And / or, the electrochemical stability window of the functional nanoparticles is not less than 4.8V; And / or, the crosslinking agent includes at least one of adipate dihydrazide, polyethylene glycol dihydrazide, and succinate dihydrazide.

5. A method for preparing the adhesive according to any one of claims 1 to 4, characterized in that, Includes the following steps: The polyacrylic acid matrix, the conductive polymer, the functional nanoparticles, and the crosslinking agent are mixed in an aqueous solvent according to the corresponding mass fractions to obtain the adhesive. The mixing temperature of the mixing process is 50℃~70℃, and the mixing time is 1h~3h.

6. The method for preparing the adhesive according to claim 5, characterized in that, The polyacrylic acid matrix is ​​prepared by the following steps: An initiator is added to an aqueous solution containing acrylic acid and 2-hydroxyethyl acrylate, and polymerization is carried out to obtain the polyacrylic acid matrix; Preferably, the initiator includes at least one of ammonium persulfate, sodium persulfate, and potassium persulfate; Preferably, the initiator has a mass fraction of 0.1% to 0.8% in the aqueous solution comprising the acrylic acid and the 2-hydroxyethyl acrylate; Preferably, the polymerization reaction is carried out at a temperature of 60°C to 70°C and for a reaction time of 1 to 5 hours.

7. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode coating loaded on at least one side of the positive current collector, wherein the positive electrode coating includes an adhesive prepared by the method of preparing the adhesive according to any one of claims 1 to 4 or the adhesive according to any one of claims 5 to 6.

8. The positive electrode sheet according to claim 7, characterized in that, The positive electrode coating comprises a positive electrode active material, a conductive agent, and a binder; the mass ratio of the positive electrode active material, the conductive agent, and the binder is (90~94):(3~5):(2~4). Preferably, the chemical formula of the positive electrode active material is LiNi. x Co y Mn 1-x-y O2, x≥0.

8.

9. The positive electrode sheet according to claim 7, characterized in that, The peel strength between the positive electrode coating and the positive electrode current collector is not less than 2 N / m; And / or, the interfacial contact resistance between the positive electrode coating and the positive electrode current collector is not higher than 30 mΩ. cm 2 ; And / or, the positive electrode slurry used to prepare the positive electrode coating has a viscosity change rate of less than 5% after standing storage for 72 hours.

10. A battery, characterized in that, The battery includes the positive electrode sheet as described in any one of claims 7 to 9.

Images