A lithium battery positive electrode slurry, positive electrode sheet, preparation method and application

Abstract

This invention relates to a lithium-ion battery positive electrode slurry, a positive electrode sheet, its preparation method, and its application, belonging to the field of battery electrode processing technology. The positive electrode slurry comprises: a positive electrode active material, a conductive agent, a binder, and a solvent; the solvent includes an amide solvent and dichloromethane, and the mass ratio of the positive electrode active material, conductive agent, and binder is (70-80):(10-15):(10-15); the mass percentage of dichloromethane in the solvent is 0.01%-0.5%. The positive electrode sheet comprises a positive electrode current collector and a positive electrode coating layer, wherein the positive electrode coating layer is obtained by coating the positive electrode slurry onto the surface of the positive electrode current collector. The positive electrode sheet is used in lithium-ion batteries. The positive electrode slurry prepared by this invention has good uniformity, the positive electrode sheet has good coating uniformity, the electrode peel strength is significantly enhanced, and the performance is superior in electrochemical performance testing.

Description

Technical Field

[0001] This invention relates to a lithium battery positive electrode slurry, positive electrode sheet, preparation method, and application, belonging to the field of battery electrode processing technology. Background Technology

[0002] The development of new energy is inseparable from the development of batteries. With the vigorous development of new energy vehicles, the usage of batteries will greatly increase. Currently, lithium battery positive electrode sheets are mainly prepared using oil-based slurries. For example, PVDF is dissolved and dispersed in NMP to form a gel, which is then mixed with other components to obtain the positive electrode slurry. To meet coating requirements, the viscosity of the slurry is controlled by adjusting the amount of NMP added. For instance, the methods disclosed in patent applications with publication numbers CN119684931A, CN117174897A, CN117334905A, and CN114628662A all use NMP to prepare electrode slurries.

[0003] Using NMP as a solvent has the following drawbacks: First, NMP has limited dispersibility for positive electrode active materials and conductive agents, leading to uneven dispersion of the prepared slurry and consequently uneven coating, affecting the performance of the positive electrode sheet. Second, the use of NMP can cause reproductive toxicity in humans, thus affecting human health. Therefore, choosing a solvent with strong dissolving and dispersing abilities, low toxicity, and low cost to replace NMP in the preparation of lithium battery positive electrode slurry and applying it to the coating of positive electrode sheets has broad application prospects. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a lithium battery positive electrode slurry, a positive electrode sheet, a preparation method, and an application. The positive electrode slurry exhibits higher uniformity, and when applied to the positive electrode sheet, the surface of the positive electrode sheet becomes smoother, which is more conducive to improving battery performance.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a lithium battery positive electrode slurry, the positive electrode slurry comprising: a positive electrode active material, a conductive agent, a binder, and a solvent; the solvent comprising an amide solvent and dichloromethane; the amide solvent being selected from at least one of the following structural formulas:

[0006] ;R 1 R 2 R 3 Each is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl.

[0007] Furthermore, the amide solvent is selected from at least one of 3-methoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-propoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

[0008] Furthermore, the mass ratio of the positive electrode active material, conductive agent, and binder is (70-80):(10-15):(10-15); the solid content of the positive electrode slurry is 30-50%; and the mass percentage of dichloromethane in the solvent is 0.01%-0.5%.

[0009] Furthermore, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese, lithium vanadium oxide, lithium titanium oxide, and lithium vanadium oxide phosphate.

[0010] Furthermore, the conductive agent is selected from at least one of conductive graphite, conductive carbon black, acetylene black, conductive carbon fiber, and conductive carbon nanotubes.

[0011] Furthermore, the adhesive is selected from at least one of polyvinylidene fluoride, polyacrylic acid, polyimide, polyethyleneimine, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and polymethyl methacrylate.

[0012] The present invention also discloses a positive electrode sheet, which includes a positive current collector and a positive electrode coating layer. The positive electrode coating layer is obtained by coating a positive electrode slurry onto the surface of the positive current collector, and the positive electrode slurry is selected from the positive electrode slurry of the present invention.

[0013] Furthermore, the positive current collector is aluminum foil.

[0014] The present invention also discloses a method for preparing a positive electrode sheet, wherein the preparation method comprises: uniformly coating the positive electrode slurry onto the positive electrode current collector, drying, and compacting to obtain the positive electrode sheet.

[0015] The present invention also discloses an application of a positive electrode sheet, which is used in a lithium-ion battery.

[0016] The beneficial effects of this invention are:

[0017] This invention uses a novel amide solvent as the solvent for fabricating the positive electrode material, through the interaction of solvent molecules with the active material Li. + The formed six-membered ring transition state structure enhances the solubility and dispersibility of the active material in the slurry. In addition, by adding a trace amount of dichloromethane, the solubility of PVDF in amide solvents can be effectively enhanced (solving the problem of poor solubility of binder PVDF in amide solvents), thereby making the prepared slurry more uniform and the electrode surface smoother.

[0018] More specifically, according to the valence bond theory, the outermost electron configuration of lithium is 1s². 2 2s 1 The outermost electron configuration of lithium ions is 1s 2 2s 0 This means that the outermost shell of lithium ions is not fully occupied by valence electrons, thus requiring electron-rich systems or heteroatoms for coordination. Compared to the traditional use of N-methylpyrrolidone (NMP) as a solvent, the ether bond in the amide solvent molecule and the oxygen atom in the carbonyl group of the present invention can coordinate with lithium ions to form a thermodynamically stable six-membered ring transition state, enhancing the solvation of lithium ions in the cathode material and improving the dispersion ability of the cathode material. The specific principle is as follows:

[0019] ;

[0020] However, the amide solvents described in this invention have low solubility for PVDF. By adding trace amounts of dichloromethane, the solubility of PVDF in MMPA can be significantly improved. Therefore, the synergistic effect of the amide solvents and dichloromethane in the positive electrode slurry of this invention makes the positive electrode slurry more uniform and stable. This enhances both the solid content of the positive electrode material and the peel strength of the positive electrode sheet. The positive electrode slurry prepared by this invention is uniformly dispersed, and the positive electrode sheet obtained from it exhibits no powder shedding or positive electrode material detachment. When applied in lithium-ion batteries, these positive electrode sheets contribute to the excellent electrical performance of lithium-ion batteries. Furthermore, the preparation method is simple and the production cost is low.

[0021] In summary, the positive electrode slurry of the present invention has good uniformity, the positive electrode sheet coating has good uniformity, the electrode peel strength is significantly enhanced, and the performance is excellent in electrochemical performance testing. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] A lithium battery positive electrode slurry, the positive electrode slurry comprising: a positive electrode active material, a conductive agent, a binder, and a solvent; the solvent comprising an amide solvent and dichloromethane; the amide solvent being selected from at least one of the following structural formulas:

[0025] ;R 1 R 2 R 3 Each is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl.

[0026] Specifically, the amide solvent is selected from at least one of 3-methoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-propoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

[0027] More specifically, when R 1 R 2 R 3 When both are methyl groups, it is named 3-methoxy-N,N-dimethylpropionamide, abbreviated as MMPA. When R... 1 R 2 All are methyl, R 3 When the ethyl group is ethyl, it is named 3-ethoxy-N,N-dimethylpropionamide, abbreviated as MEPA. When R... 1 R 2 All are methyl, R 3 When it is n-propyl, it is named 3-propoxy-N,N-dimethylpropionamide, abbreviated as MIPA. When R... 1 R 2 All are methyl, R 3 It is n-butyl, named 3-butoxy-N,N-dimethylpropionamide, abbreviated as MBPA.

[0028] Specifically, the mass ratio of the positive electrode active material, conductive agent, and binder is (70-80):(10-15):(10-15); the solid content of the positive electrode slurry is 30-50%; and the mass percentage of dichloromethane in the solvent is 0.01%-0.5%. The solid content refers to the mass percentage of the total mass of the positive electrode active material, conductive agent, and binder in the positive electrode slurry.

[0029] Specifically, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese, lithium vanadium oxide, lithium titanium oxide, and lithium vanadium oxide phosphate.

[0030] Specifically, the conductive agent is selected from at least one of conductive graphite, conductive carbon black, acetylene black, conductive carbon fiber, and conductive carbon nanotubes.

[0031] Specifically, the adhesive is selected from at least one of PVDF (polyvinylidene fluoride), PAA (polyacrylic acid), PI (polyimide), PEI (polyethyleneimide), CMC-Na (sodium carboxymethyl cellulose), CMC-Li (lithium carboxymethyl cellulose), and PMMA (polymethyl methacrylate).

[0032] A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode coating layer, the positive electrode coating layer being obtained by coating a positive electrode slurry onto the surface of the positive current collector, the positive electrode slurry being selected from the positive electrode slurry of the present invention.

[0033] Specifically, the positive current collector is aluminum foil.

[0034] More specifically, the aluminum foil thickness is 12μm-20μm; the positive electrode coating thickness is 10μm-100μm. However, this does not constitute a limitation on the present invention, and a suitable thickness can be selected as needed in practical applications.

[0035] A method for preparing a positive electrode sheet, the method comprising: uniformly coating the positive electrode slurry onto the positive electrode current collector, drying it at 100-120℃ (drying time is 16-24 h), and compacting it to obtain the positive electrode sheet.

[0036] More specifically, the positive current collector has two opposing surfaces; the positive coating layer is formed by coating a uniformly dispersed slurry onto at least one surface of the positive current collector.

[0037] More specifically, the preparation method of the positive electrode sheet is as follows: first, the binder is dissolved in the solvent, the positive active material and the conductive agent are dispersed in the above solution and stirred evenly; the mixture is allowed to stand under vacuum to remove bubbles, and then evenly coated on the current collector aluminum foil with a scraper. It is first placed in the air, then dried in an oven to remove the remaining solvent, and finally cut into suitable positive electrode sheets.

[0038] An application of a positive electrode sheet, wherein the positive electrode sheet is used in a lithium-ion battery.

[0039] Example 1

[0040] Preparation of a positive electrode sheet:

[0041] The positive electrode active material in the positive electrode slurry is a ternary nickel-cobalt-manganese alloy, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MMPA) and dichloromethane (0.1% by mass of dichloromethane).

[0042] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0043] Example 2

[0044] Preparation of a positive electrode sheet:

[0045] The positive electrode active material in the positive electrode slurry is lithium iron phosphate, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 30%. The solvent is a mixture of amide solvent (MMPA) and dichloromethane (0.1% by mass of dichloromethane).

[0046] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0047] Example 3

[0048] Preparation of a positive electrode sheet:

[0049] The positive electrode active material in the positive electrode slurry is lithium iron phosphate; the conductive agent is conductive graphite; and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MMPA) and dichloromethane (0.1% by mass of dichloromethane).

[0050] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0051] Example 4

[0052] Preparation of a positive electrode sheet:

[0053] The positive electrode active material in the positive electrode slurry is lithium iron phosphate, the conductive agent is conductive graphite, and the binder is CMC-Na (sodium carboxymethyl cellulose). The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 50%; the solvent is a mixture of amide solvent (MMPA) and dichloromethane (dichloromethane mass fraction 0.1%).

[0054] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0055] Example 5

[0056] Preparation of a positive electrode sheet:

[0057] The positive electrode active material in the positive electrode slurry is lithium iron phosphate, the conductive agent is acetylene black, and the binder is CMC-Na (sodium carboxymethyl cellulose). The mass ratio of the positive electrode active material, conductive agent, and binder is 70:15:15. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MMPA) and dichloromethane (0.1% by mass of dichloromethane).

[0058] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15 μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 120 ℃ for 16 h. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12 μm.

[0059] Example 6

[0060] Preparation of a positive electrode sheet:

[0061] The positive electrode active material in the positive electrode slurry is ternary nickel-cobalt-manganese, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MEPA) and dichloromethane (0.1% by mass of dichloromethane).

[0062] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0063] Example 7

[0064] Preparation of a positive electrode sheet:

[0065] The positive electrode active material in the positive electrode slurry is ternary nickel-cobalt-manganese, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MIPA) and dichloromethane (0.1% by mass of dichloromethane).

[0066] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0067] Example 8

[0068] Preparation of a positive electrode sheet:

[0069] The positive electrode active material in the positive electrode slurry is ternary nickel-cobalt-manganese alloy, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is a mixture of amide solvent (MBPA) and dichloromethane (0.01% dichloromethane by mass).

[0070] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0071] Comparative Example 1

[0072] The positive electrode sheet was prepared using the same method as in Example 1, except that the solvent in Comparative Example 1 was a pure amide solvent (MMPA).

[0073] Comparative Example 2

[0074] The positive electrode sheet was prepared using the same method as in Example 1, except that the solvent in Comparative Example 1 was a pure amide solvent (MMPA), and the PVDF was dissolved by heating. The specific process is as follows:

[0075] The positive electrode active material in the positive electrode slurry is a ternary nickel-cobalt-manganese alloy, the conductive agent is conductive carbon black, and the binder is PVDF. The mass ratio of the positive electrode active material, conductive agent, and binder is 80:10:10. The solid content of the positive electrode slurry is 40%. The solvent is an amide solvent (MMPA).

[0076] First, PVDF is dissolved in an amide solvent at 60°C until completely dissolved. Then, the solution is cooled to room temperature, and conductive carbon black and ternary nickel-cobalt-manganese alloy are added.

[0077] The well-stirred positive electrode slurry was degassed under vacuum and coated onto one side of the positive electrode current collector (15μm aluminum foil). After coating, the positive electrode slurry was vacuum dried at 100℃ for 16 hours. The positive electrode sheet was then rolled to obtain the coating layer, which had a thickness of 12μm.

[0078] Comparative Example 3

[0079] The positive electrode sheet was prepared using the same method as in Example 1, except that the proportion of PVDF binder was reduced in Comparative Example 3, and the proportion of binder in the total mass of positive electrode active material, conductive agent and binder was 5% in Comparative Example 2.

[0080] Comparative Example 4

[0081] The positive electrode was prepared using the same method as in Example 1, except that the proportion of dichloromethane in the solvent was increased in Comparative Example 4, while the mass fraction of dichloromethane in the solvent was 1% in Comparative Example 3.

[0082] Comparative Example 5

[0083] The positive electrode sheet was prepared using the same method as in Example 1, except that the solvent in Comparative Example 1 was NMP.

[0084] The positive electrode sheets prepared in the above embodiments and comparative examples were used to fabricate coin cells for electrical performance verification. The coin cell fabrication method is as follows: the negative electrode shell is placed flat on a glass plate with the opening facing upwards. A spring plate is clamped and placed on the negative electrode shell, and a current collector is clamped and placed on the spring plate, ensuring strict alignment. A lithium sheet is clamped and placed in the current collector. Electrolyte (a 0.1 mol / L LiPF6 solution using ethylene carbonate and diethyl carbonate as a mixed solvent) is drawn up using a dropper and used to wet the surface of the lithium sheet. A separator (commercially available polypropylene separator) is clamped and placed over the lithium sheet. Electrolyte is drawn up again using a dropper to wet the surface of the separator. The positive electrode sheet is placed on the separator, with the positive electrode sheet positioned in the exact center of the positive electrode shell. This step should be practiced repeatedly to ensure that the clamping force of the tweezers is appropriate and will not damage the positive electrode sheet. Bending or twisting the positive electrode sheet is strictly prohibited. The positive electrode shell is then placed flat and clamped down with the tweezers to cover the positive electrode.

[0085] The uniformity and flatness of the electrode surface were observed. The initial charge-discharge efficiency was tested at 0.1C, and the capacity retention and rate performance of the battery were tested after 100 cycles at 0.5C. The test results are shown in Table 1 below.

[0086] Table 1 Performance Test Results

[0087]

[0088] As can be seen from the data in Table 1 above, the positive electrode sheets prepared by the preparation method described in this invention in Examples 1-8 have very good electrochemical performance when applied to button cells, and the electrode surface is smooth and free of particles.

[0089] As can be seen from Example 1 and Comparative Example 3, in order to eliminate the problem of poor solubility of PVDF in MMPA, NMP and MMPA can be mixed to form a mixed solvent, which can be applied to the preparation of positive electrode slurry. This is because NMP has a higher polarity than MMPA, and therefore has a higher solubility for PVDF than MMPA, which enhances the solubility of PVDF in MMPA, thereby eliminating the agglomeration of slurry, improving surface smoothness, and enhancing electrochemical performance.

[0090] The comparison between the results of Example 1 and Comparative Example 1 shows that when MMPA is used alone in slurry preparation, the surface smoothness of the electrode is poor and the particle texture is obvious. This is because MMPA has poor solubility for PVDF. However, adding a trace amount of dichloromethane to the solvent can significantly improve the solubility of PVDF, improve the uniformity of the slurry, thereby improving the smoothness of the electrode, eliminating the particle texture, and improving the electrochemical performance of the electrode.

[0091] The comparison of the results of Example 1 and Comparative Example 2 shows that when MMPA is used alone in slurry preparation, even if heating is carried out during the dissolution process, it will still affect the smoothness of the electrode surface.

[0092] The comparison between the results of Example 1 and Comparative Example 3 shows that the content of PVDF as a binder has a significant impact on the quality of the electrode. If the content is too low, it will not only cause the agglomeration of the positive electrode active material and the conductive agent, resulting in obvious particle texture on the surface of the electrode, but also cause the active material to fall off during the use of the electrode, affecting the electrochemical performance.

[0093] A comparison of the results of Example 1 and Comparative Example 4 shows that increasing the concentration of dichloromethane is detrimental to the preparation of the positive electrode slurry and the electrochemical performance of the electrode. This is because dichloromethane will destroy the structure and composition of the active material, thereby reducing the quality of the electrode and affecting its electrochemical performance.

[0094] A comparison of the results of Example 1 and Comparative Example 5 shows that the positive electrode sheet prepared using the solvent specified in this invention is significantly better than that prepared using conventional NMP solvent.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A lithium battery positive electrode slurry, characterized in that, The positive electrode slurry comprises: a positive electrode active material, a conductive agent, a binder, and a solvent; the solvent comprises an amide solvent and dichloromethane; the amide solvent is selected from at least one of the following structural formulas: ;R 1 R 2 R 3 Each is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl; The mass ratio of the positive electrode active material, conductive agent, and binder is (70-80):(10-15):(10-15); the solid content of the positive electrode slurry is 30-50%; and the mass percentage of dichloromethane in the solvent is 0.01%-0.5%. The adhesive is polyvinylidene fluoride.

2. The lithium battery positive electrode slurry according to claim 1, characterized in that, The amide solvent is selected from at least one of 3-methoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-propoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

3. The lithium battery positive electrode slurry according to claim 1, characterized in that, The positive electrode active material is selected from at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese, lithium vanadium oxide, lithium titanium oxide, and lithium vanadium oxide phosphate.

4. The lithium battery positive electrode slurry according to claim 1, characterized in that, The conductive agent is selected from at least one of conductive graphite, conductive carbon black, acetylene black, conductive carbon fiber, and conductive carbon nanotubes.

5. A positive electrode sheet, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode coating layer. The positive electrode coating layer is obtained by coating a positive electrode slurry onto the surface of the positive current collector. The positive electrode slurry is selected from the positive electrode slurry of any one of claims 1-4.

6. The positive electrode sheet according to claim 5, characterized in that, The positive current collector is aluminum foil.

7. A method for preparing a positive electrode sheet according to any one of claims 5-6, characterized in that, The preparation method is as follows: the positive electrode slurry is uniformly coated on the positive electrode current collector, dried, and compacted to obtain the positive electrode sheet.

8. An application of a positive electrode sheet according to any one of claims 5-6, characterized in that, The positive electrode is used in lithium-ion batteries.

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