A battery positive electrode sheet, a battery

Abstract

The application provides a battery positive plate and a battery, the battery positive plate comprising a positive active material and a binder, the binder being a product obtained by cross-linking a polyacrylic compound modified by a phenylboronic acid compound and a hydroxylated carbon nanotube.The battery positive plate of the application adopts a three-dimensional conductive network binder based on cross-linking of a polyacrylic compound modified by a phenylboronic acid compound and a hydroxylated carbon nanotube, the binder forming a special three-dimensional conductive network structure by a multiple cross-linking mechanism between the phenylboronic acid group, the hydroxylated carbon nanotube (OHCNT) and the positive active particles, and self-cross-linking between the phenylboronic acids to form a boroxin structure, improving the mechanical strength, the electrical conductivity of the binder, the cycle performance and the stability of the battery; the discharge performance and the ability of fast charging and discharging of the battery can be improved, and the consumption of electrolyte can be reduced, thereby prolonging the cycle life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to a battery, in particular to a battery positive electrode sheet and a battery. BACKGROUND

[0002] With the steady growth of electric vehicle sales in the past few years, lithium-ion batteries play a crucial role in moving towards a more efficient "energy future" due to their high energy and high power density. Although lithium-ion batteries have the above advantages, they must also overcome problems such as unstable electrode structure, electrode surface degradation, unsatisfactory battery electrochemical performance, and low battery safety in commercial batteries. Generally speaking, the binder in the electrode has a very low mass ratio, which has a profound impact on the safety and electrochemical performance of lithium-ion batteries, and is a simple and effective method to improve the above problems.

[0003] The binder is an important component of the battery electrode sheet, which can enhance the contact between the active material, the conductive agent and the current collector, and can maintain good stability. The existing traditional binder usually uses a polymer matrix, such as polyvinylidene fluoride (PVDF) and the like. Although these traditional binders can achieve effective adhesion of the positive electrode material and the electrode current collector to a certain extent, they have some limitations: 1. Limited adhesion effect and mechanical properties: the mechanical strength and flexibility of traditional binders are poor, and especially under high energy density and high current density conditions, they are prone to fracture or peeling, which limits the cycle life and safety of the battery, in addition, the traditional binder is bonded by van der Waals force, and the weak van der Waals force leads to poor adhesion of the electrode sheet. 2. Insufficient electrical conductivity: the electrical conductivity of traditional binders is low, which will increase the internal resistance of the battery and limit the discharge performance and rapid charge-discharge capability of the battery. 3. Poor interface stability: the interface stability between the traditional binder and the positive active material is poor, and the interface reaction or electrolyte penetration is easy to occur, which leads to the decrease of battery performance and the increase of electrolyte consumption. SUMMARY

[0004] The present application is aimed at the above problems, and makes up for the deficiencies of the prior art, and provides a battery positive electrode sheet and a battery.

[0005] In a first aspect, the present application provides a battery positive electrode sheet, comprising a positive active material and a binder, wherein the binder is a product obtained by cross-linking a polyacrylic compound modified by a phenylboronic acid compound and a hydroxylated carbon nanotube.

[0006] The battery positive plate of the present application adopts a three-dimensional conductive network binder based on phenylboronic acid compound modified polyacrylic compound and cross-linked hydroxylated carbon nanotube, the binder utilizes the multiple cross-linking mechanism between the phenylboronic acid group and the hydroxylated carbon nanotube (OHCNT) and the positive active particles, and the self-cross-linking between the phenylboronic acid to form a boroxin structure, to form a special three-dimensional conductive network structure, improve the mechanical strength, electrical conductivity, cycle performance and stability of the battery, further improve the discharge performance and the ability of fast charge and discharge of the battery, and also can reduce the consumption of electrolyte, so as to form a more stable electrolyte interface (CEI) film containing B, thereby prolonging the cycle life of the battery.

[0007] Specifically, in some embodiments of the present application, the mass ratio of the phenylboronic acid compound to the polyacrylic compound is 0.19-1.33; more specifically, the mass ratio of the phenylboronic acid compound to the polyacrylic compound is 0.19, 0.38, 0.57, 0.76, 0.95, 1.14, 1.33; preferably, the mass ratio of the phenylboronic acid compound to the polyacrylic compound is 0.57-0.95.

[0008] Specifically, in some embodiments of the present application, the mass ratio of the phenylboronic acid compound modified polyacrylic compound to the hydroxylated carbon nanotube is 1.0-6.0, more specifically, the mass ratio of the phenylboronic acid compound modified polyacrylic compound to the hydroxylated carbon nanotube is 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0; preferably, the mass ratio of the phenylboronic acid compound modified polyacrylic compound to the hydroxylated carbon nanotube is 2.0-3.0.

[0009] The mass ratio of the phenylboronic acid compound modified polyacrylic compound to the hydroxylated carbon nanotube in the present application is too large or too small, which will cause the cross-linking density to be too large, the polymer network to be complex, the slurry viscosity to be too large, and the polymer to be unable to adapt to the expansion of the silicon negative electrode, resulting in poor cycle performance of the battery.

[0010] Specifically, in some embodiments of the present application, the raw material of the binder further includes an activator, and the mass ratio of the activator to the polyacrylic compound is 0.53-1.60, more specifically, the mass ratio of the activator to the polyacrylic compound is 0.53, 0.79, 1.06, 1.32, 1.60; preferably, the mass ratio of the activator to the polyacrylic compound is 0.79-1.32.

[0011] In the present application, the cross-linking degree of the phenyl boronic acid compound modified polyacrylic compound is regulated by controlling the mass ratio of the activator and the polyacrylic compound. When the content of the activator is too high, the cross-linking degree of the phenyl boronic acid compound modified polyacrylic compound is also too high, which can cause the positive electrode particles, the conductive agent and the binder to be not dispersed in the slurry process, so that the uniformity of the electrode sheet cannot be maintained, thereby affecting the improvement of the performance of the binder and the battery. When the content of the activator is too low, the cross-linking degree of the phenyl boronic acid compound modified polyacrylic compound is too low, which can cause the positive electrode slurry to have very low viscosity, so that the slurry cannot be uniformly coated in the coating process, thereby affecting the improvement of the performance of the binder and the battery.

[0012] Specifically, in some embodiments of the present application, the activator is at least one of 1-ethyl-(3-dimethylaminopropyl) carbodiimide, dicyclohexyl carbodiimide, N,N'-diisopropyl carbodiimide.

[0013] Specifically, in some embodiments of the present application, the mass ratio of the positive electrode active material and the binder is 92:8-98:2; specifically, the mass ratio of the positive electrode active material and the binder is 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2; preferably, the mass ratio of the positive electrode active material and the binder is 94:6-97:3.

[0014] Specifically, in some embodiments of the present application, the phenyl boronic acid compound is at least one of 3-aminophenyl boronic acid, 2-aminophenyl boronic acid, 4-aminophenyl boronic acid, [3-(2-aminoethyl) phenyl] boronic acid, 3-aminomethylphenyl boronic acid.

[0015] Specifically, in some embodiments of the present application, the polyacrylic compound includes at least one of polyacrylic acid, polymethacrylic acid, sodium polyacrylate, lithium polyacrylate, sodium polymethacrylate, lithium polymethacrylate.

[0016] Specifically, in some embodiments of the present application, the polyacrylic compound modified by the phenyl boronic acid compound is cross-linked with the hydroxylated carbon nanotube, which includes:

[0017] S1: the polyacrylic compound and the alkali are dissolved in water, and then the phenyl boronic acid compound aqueous solution is added to obtain a mixed solution; the mixed solution is cooled to 2-7℃, and then the activator is added to react for 10-14 hours to obtain the phenyl boronic acid compound modified polyacrylic compound;

[0018] S2: the hydroxylated carbon nanotube and the dispersant are added to water and ultrasonically treated for 1-3 hours to obtain a dispersion liquid, which is mixed with the phenyl boronic acid compound modified polyacrylic compound.

[0019] Compared with the traditional binder preparation process, the three-in-one formula design of the binder, the conductive agent and the solvent is adopted, the synthesis process is simplified, the preparation efficiency is improved, and the technical scheme has significant potential for direct industrial application.

[0020] Specifically, in some embodiments of the present application, the positive active material includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0021] Preferably, in some embodiments of the present application, the lithium cobalt oxide is LiCoO2; the lithium nickel oxide is LiNiO2; the lithium manganese oxide is Li2Mn2O4; the lithium nickel manganese oxide is LiNi 0.5 Mn 1.5 O4; the lithium nickel cobalt manganese oxide is LiNi 0.33 Co 0.33 Mn 0.33 O2.

[0022] Specifically, in some embodiments of the present application, the base is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide.

[0023] In a second aspect, the present application also provides a battery positive plate preparation method, including the following steps: using a blender to mix the positive active material and the binder uniformly to obtain a positive slurry, using a coating machine to coat the positive slurry on the surface of the current collector, and after drying and cutting, obtaining the battery positive plate, and the active material load is about 10-15 mg·cm -2 .

[0024] The present application also provides a battery including the above-mentioned battery positive plate, and the battery is a lithium ion battery, a semi-solid battery or a solid-state battery.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (1) The present application provides a battery positive plate, which adopts a three-dimensional conductive network binder based on phenylboronic acid modified polyacrylic acid compound and hydroxylated carbon nanotube crosslinking. The binder utilizes the multiple crosslinking mechanism between the phenylboronic acid group, the hydroxylated carbon nanotube (OHCNT) and the positive active particles, and the self-crosslinking between the phenylboronic acid to form B-O-B structure, forming a special three-dimensional conductive network structure, improving the mechanical strength, electrical conductivity, cycle performance and stability of the battery; further improving the discharge performance and rapid charge-discharge capacity of the battery, and also reducing the consumption of electrolyte, forming a more stable electrolyte interface (CEI) film, thereby prolonging the cycle life of the battery.

[0027] (2) In the present application, the cross-linking degree of the phenylboronic acid compound modified polyacrylic compound is regulated by controlling the mass ratio of the activator and the polyacrylic compound, and the peeling force, the interfacial peeling strength, the viscosity, the conductivity of the binder and the cycle performance of the battery are improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Synthesis principle of the 3-aminophenylboronic acid modified modified polyacrylic compound in Example 1;

[0029] Figure 2 Synthesis principle of the binder in Example 1;

[0030] Figure 3 Infrared detection spectrum of the phenylboronic acid compound modified polyacrylic compound;

[0031] Figure 4 Infrared detection spectrum of the binder. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0033] Example 1

[0034] The present embodiment provides a battery positive plate, which comprises LiCoO2 active material and a binder, and the binder is a product of cross-linking of a phenylboronic acid compound modified polyacrylic compound and hydroxylated carbon nanotubes.

[0035] Preparation of the binder:

[0036] S1: 1g of polyacrylic acid (PAA) and 0.05g of LiOH were dissolved in 20g of water, 0.76g of 3-aminophenylboronic acid (APBA) was added to obtain a mixed solution, the mixed solution was cooled to 4℃, 1.06g of 1-ethyl-(3-dimethylaminopropyl) carbonyldiimidazole was added and kept at 4℃ for 12 hours, and 3-aminophenylboronic acid modified polyacrylic acid was obtained by purification through dialysis, and the synthesis principle is as shown in Figure 1 .

[0037] S2: 0.3g of hydroxylated carbon nanotubes (OHCNT) and 0.33g of dispersant were added to 15.75g of water and ultrasonically treated for 2 hours to obtain a hydroxylated carbon nanotube dispersion liquid. 0.75g of 3-aminophenylboronic acid modified polyacrylic acid was mixed with the hydroxylated carbon nanotube dispersion liquid to obtain a binder (PBO), and the synthesis principle is as shown inFigure 2 As shown.

[0038] Preparation of the positive electrode: The positive electrode active LiCoO2 and binder were mixed and stirred evenly at a mass ratio of 95:5 using a mixer to obtain a positive electrode slurry of suitable viscosity. The slurry was then coated onto a copper current collector using a coating machine. After vacuum drying at 120℃ for 12 hours, the positive electrode was cut into circular pieces with a diameter of 12mm. The positive loading of the active material was approximately 13.0 mg / cm³. -2 .

[0039] Half-cell fabrication: Electrochemical performance was evaluated using half-cells assembled by sandwiching a diaphragm (approximately 25 μm) between a working electrode based on the aforementioned binder and a lithium foil counter electrode.

[0040] In this embodiment, the infrared detection results of 3-aminophenylboronic acid-modified polyacrylic acid are as follows: Figure 3 As shown, at 2877cm -1 The absorption peak at 1465 cm⁻¹ represents the stretching vibration of the CH bond in the benzene ring. -1 The absorption peak at 1350 cm⁻¹ is due to the in-plane deformation vibration of the NH bond. -1 The absorption peak represents the stretching vibration of the BO bond, proving that 3-aminophenylboronic acid successfully modified polyacrylic acid.

[0041] Infrared detection results of the adhesive are as follows Figure 4 As shown, the adhesive is at 1231cm -1 The absorption peak at 735 cm⁻¹ represents the stretching vibration of BOC. -1 The absorption peak represents the stretching vibration of BOB, proving the successful combination of 3-aminophenylboronic acid modified polyacrylic acid and OH-CNT.

[0042] Example 2-35

[0043] This embodiment is used to compare and illustrate the lithium-ion battery disclosed in this invention, including most of the operating steps in the above embodiment 1. The difference is that the synthesis conditions of the negative electrode active material, the phenylboronic acid-modified polyacrylic acid compound and the binder, the synthesis components of the phenylboronic acid-modified polyacrylic acid compound and the binder and their mass and mass ratio are shown in Table 1.

[0044] Comparative Example 1

[0045] Compared with Example 1, the adhesive used in this comparative example is a direct mixture of polyvinylidene fluoride and a conductive agent, and the rest is the same as in Example 1.

[0046] Table 1

[0047]

[0048]

[0049]

[0050]

[0051] The performance detection method of the lithium ion battery in Examples 1-35 and Comparative Example 1 is as follows: Experiment I,

[0052] Peeling test of the positive electrode sheet: the peeling force and interface peeling strength of the positive electrode sheet in Examples 1-35 and Comparative Example 1 were tested according to the national standard GB / T 2792-2014 "Test method for adhesive tape peeling strength" by using an electronic tensile testing machine, and the test results are shown in Table 2.

[0053] Experiment II,

[0054] Viscosity test of the positive electrode slurry: the viscosity of the positive electrode slurry in Examples 1-35 and Comparative Example 1 was tested by using a digital viscometer, and the test results are shown in Table 2.

[0055] Experiment III,

[0056] Conductivity test (determined by four-probe method): the binder in Examples 1-35 and Comparative Example 1 was coated on a PE film by using a 100 μm doctor blade, and a conductive film was obtained after drying, and the conductivity test was performed.

[0057] Experiment IV,

[0058] Cycle performance test: at 25°C, constant current charging to 4.35V at 0.2C rate, then constant voltage charging to 0.05C at 4.35V, then discharging to 3.0V at 0.2C rate, which is one charge-discharge cycle process, repeating 100 times of such charge-discharge cycle process. The capacity retention rate after 100 cycles = the discharge capacity after the 100th cycle / the discharge capacity after the first cycle x 100%, and the test results are shown in Table 2.

[0059] Table 2

[0060]

[0061]

[0062] As can be seen from the data in Table 2: from the battery performance test of Examples 1-35 and Comparative Example 1, it can be seen that the peeling force, interfacial peeling strength, viscosity (Pa·s), and conductivity of the three-dimensional conductive network binder based on the phenylboronic acid compound modified polyacrylic compound and the crosslinked hydroxylated carbon nanotube of the present application are superior to the polyvinylidene fluoride binder of Comparative Example 1, and the cycle performance and stability of the battery prepared are also superior to the battery prepared in Comparative Example 1, indicating that the binder of the present application utilizes the multiple crosslinking mechanism between the phenylboronic acid group and the hydroxylated carbon nanotube (OHCNT) and the positive active particles, and the self-crosslinking between the phenylboronic acid to form a boroxin structure, forming a special three-dimensional conductive network structure, improving the mechanical strength, conductivity of the binder, cycle performance and stability of the battery; from the battery performance test results of Examples 1-5 and Examples 6-7, it can be seen that when the mass ratio of the phenylboronic acid compound / polyacrylic compound is in the range of 0.19-1.33, the peeling force, interfacial peeling strength, viscosity (Pa·s), conductivity of the binder and the cycle stability of the battery are more superior; from the battery performance test results of Examples 1, Examples 8-10 and Examples 11-12, it can be seen that when the mass of the phenylboronic acid compound modified polyacrylic compound and the hydroxylated carbon nanotube is in the range of 1.0-6.0, the peeling force, interfacial peeling strength, viscosity (Pa·s), conductivity of the binder and the cycle stability of the battery are more superior; from the battery performance test results of Examples 1, Examples 13-15 and Examples 16-17, it can be seen that when the mass ratio of the activator and the polyacrylic compound is in the range of 0.53-1.60, the peeling force, interfacial peeling strength, viscosity (Pa·s), conductivity of the binder and the cycle stability of the battery are more superior.

[0063] The above has further described the present application by means of specific examples, but it should be understood that the specific description herein should not be understood as limiting the essence and scope of the present application, and various modifications made by those of ordinary skill in the art after reading the present specification to the above examples all belong to the scope protected by the present application.

Claims

1. A battery positive electrode sheet, characterized by, The positive electrode active material, a binder, the binder being a product obtained by cross-linking a polyacrylic compound modified with a phenylboronic acid compound and a hydroxylated carbon nanotube.

2. The battery cathode sheet according to claim 1, wherein The mass ratio of the phenylboronic acid compound to the polyacrylic compound is 0.19-1.

33.

3. The battery cathode sheet according to claim 1, wherein The mass ratio of the polyacrylic compound modified with the phenylboronic acid compound to the hydroxylated carbon nanotube is 1.0-6.

0.

4. The battery cathode sheet according to claim 1, wherein The raw material of the binder further comprises an activator, and the mass ratio of the activator to the polyacrylic compound is 0.53-1.

60.

5. The battery cathode sheet according to claim 4, wherein The activator is at least one of 1-ethyl-(3-dimethylaminopropyl) carbodiimide, dicyclohexyl carbodiimide, and N,N'-diisopropyl carbodiimide.

6. The battery cathode sheet according to claim 1, wherein The phenylboronic acid compound is at least one of 3-aminophenylboronic acid, 2-aminophenylboronic acid, 4-aminophenylboronic acid, [3-(2-aminoethyl) phenyl] boronic acid, and 3-aminomethylphenylboronic acid.

7. The battery cathode sheet according to claim 1, wherein The polyacrylic compound comprises at least one of polyacrylic acid, polymethacrylic acid, sodium polyacrylate, lithium polyacrylate, sodium polymethacrylate, and lithium polymethacrylate.

8. The battery cathode sheet according to any one of claims 1-7, wherein, The polyacrylic compound is modified with the phenylboronic acid compound and cross-linked with the hydroxylated carbon nanotube, comprising: S1: dissolving a polyacrylic compound and a base in water, adding an aqueous solution of a phenylboronic acid compound to obtain a mixed solution, cooling the mixed solution to 2-7°C, adding an activator, and reacting for 10-14 hours to obtain a polyacrylic compound modified with a phenylboronic acid compound; S2: adding a hydroxylated carbon nanotube and a dispersant to water and ultrasonically treating for 1-3 hours to obtain a dispersion, and mixing the dispersion with the polyacrylic compound modified with the phenylboronic acid compound.

9. The battery cathode sheet according to claim 1, wherein The positive electrode active material comprises at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide.

10. A battery, characterized by The battery is a lithium ion battery, a semi-solid battery, or a solid-state battery.

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