Positive electrode slurry, preparation method thereof, positive electrode sheet, secondary battery, battery module, battery pack, and electric device

Abstract

The application provides a positive electrode slurry, comprising solid content and water; the solid content comprises a positive electrode active material capable of embedding and discharging lithium ions and a lithium-containing graphene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, and in particular to a positive electrode slurry, a preparation method thereof, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and a power utilization device. BACKGROUND

[0002] Secondary batteries such as lithium ion batteries have a high energy density, good cycle performance, and a high average output voltage, and are widely used in consumer electronics, electric vehicles, and other fields. Because positive electrode active materials such as lithium iron phosphate are easily deteriorated when in contact with water, in the preparation process of traditional lithium ion batteries, the positive electrode sheet is usually prepared from an oily positive electrode slurry of an N-methyl pyrrolidone (NMP)-polyvinylidene fluoride (PVDF) system. However, the NMP solvent has problems such as difficulty in recycling, high cost, and environmental pollution. SUMMARY

[0003] To solve the above problems, the present application provides a positive electrode slurry, a preparation method thereof, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and a power utilization device, which can effectively prevent the deterioration of the positive electrode active material, and have good processability and low cost.

[0004] In one aspect of the present application, a positive electrode slurry is provided, which includes solid content and water.

[0005] The solid content includes a positive electrode active material capable of intercalating and deintercalating lithium ions and lithium-containing graphene.

[0006] In the positive electrode slurry of the present application, the lithium-containing graphene can coat the positive electrode active material due to the π-π stacking effect of the lithium-containing graphene, thereby preventing the performance deterioration of the positive electrode active material caused by the combination of water. At the same time, the solid content has good dispersibility in the solvent water, good processability, low cost, and environmental friendliness.

[0007] In some embodiments, the lithium-containing graphene at least partially coats the surface of the positive electrode active material. The lithium-containing graphene at least partially coating the surface of the positive electrode active material can form a hydrophilic layer on the surface of the positive electrode active material, improve the dispersibility of the positive electrode active material, and prevent the positive electrode active material from contacting water. In addition, the lithium ions in the lithium-containing graphene can also improve the lithium ion transport on the positive electrode sheet, and the kinetic performance of the secondary battery is better.

[0008] In some embodiments, the lithium-containing graphene includes lithium-containing sulfonic acid group graphene. The sulfonic acid group in the lithium-containing sulfonic acid group graphene can further improve the dispersibility of the positive electrode active material in the positive electrode slurry through electrostatic repulsion, and the processability of the positive electrode slurry is better.

[0009] In some embodiments, the molar ratio of Li to S in the lithium sulfonate-based graphene is 1:(1-10); optionally, the molar ratio of Li to S in the lithium sulfonate-based graphene is 1:(1-5). When the molar ratio of Li to S in the lithium sulfonate-based graphene is within the above range, the positive electrode slurry used to prepare the secondary battery exhibits better kinetic performance.

[0010] In some embodiments, the molar ratio of C to S in the lithium sulfonate-based graphene is (3-12):1.

[0011] In some embodiments, the lithium-containing graphene content in the solid is 0.01% to 2% by mass; optionally, the lithium-containing graphene content in the solid is 0.2% to 1.5% by mass. A lithium-containing graphene content within the above range can effectively improve the dispersibility of the positive electrode active material in aqueous positive electrode slurry and prevent the positive electrode active material from deteriorating due to water absorption.

[0012] In some embodiments, the positive electrode active material includes LiFe. m Mn 1-m PO4, Li(Ni) x Co y Mn z Al a Cu b Zn c Ti d At least one of O2, 0≤m≤1, x+y+z+a+b+c+d=1, 0.5≤x<1, 0.05≤y<1, 0≤z<0.5, 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.1, 0≤d≤0.1;

[0013] Optionally, the positive electrode active material is LiFePO4.

[0014] In some embodiments, the solid content further includes a dispersant; optionally, the dispersant includes at least one of a cationic dispersant and an amphoteric dispersant; optionally, the dispersant includes at least one of polyethyleneimine and polyethylene glycol octylphenyl ether. The above dispersants, in synergy with lithium-containing graphene, can further improve the dispersibility of the cathode slurry.

[0015] In some embodiments, the mass percentage of the dispersant in the solids is 0.01% to 2%; optionally, the mass percentage of the dispersant in the solids is 0.1% to 0.5%. When the mass content of the dispersant is within the above range, the positive electrode slurry has good dispersibility and good processing performance.

[0016] In some embodiments, the solid content further comprises a water-based binder; optionally, the water-based binder comprises at least one of methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyacrylamide and acrylonitrile-acrylic acid copolymer and its derivatives. The water-based binder can be dissolved in solvent water, and the positive electrode slurry has a suitable viscosity and cohesiveness.

[0017] In some embodiments, the water-based binder is acrylonitrile-acrylic acid copolymer; optionally, the number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300,000-2,000,000.

[0018] In some embodiments, the mass percentage of the water-based binder in the solid content is 0.1%-5%; optionally, the mass percentage of the water-based binder in the solid content is 2%-4%. When the mass content of the water-based binder is within the above range, the positive electrode slurry has a suitable viscosity, which is conducive to the preparation of the positive electrode sheet.

[0019] In some embodiments, the solid content further comprises a conductive agent; optionally, the conductive agent comprises at least one of conductive carbon black, super-conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene and carbon nanotube.

[0020] In some embodiments, the mass percentage of the conductive agent in the solid content is 0.1%-5%; optionally, the mass percentage of the conductive agent in the solid content is 0.5%-3%.

[0021] In some embodiments, the mass percentage of the solid content in the positive electrode slurry is 40%-90%; optionally, the mass percentage of the solid content in the positive electrode slurry is 50%-70%. The dispersion of the solid content in the above positive electrode slurry is good, and the mass content of the solid content can reach 90%, thereby further reducing the amount of solvent water.

[0022] In some embodiments, the viscosity of the positive electrode slurry is 100-10,000 cp; optionally, the viscosity of the positive electrode slurry is 3,000-7,000 cp. When the viscosity of the positive electrode slurry is within the above range, it is conducive to the subsequent processing and preparation of the positive electrode sheet.

[0023] In a second aspect, the present application further provides a preparation method of the above positive electrode slurry, comprising the following steps:

[0024] Mixing the solid content and the water.

[0025] In some embodiments, the step of mixing the solid content and the water comprises:

[0026] The positive electrode active material, the lithium-containing graphene, a dispersant and a conductive agent are mixed to prepare a lump material;

[0027] The lump material, an aqueous binder and water are mixed.

[0028] The positive electrode active material, the lithium-containing graphene and the dispersant are first mixed to prepare a lump material, which can further improve the dispersion of the positive electrode active material in the positive electrode slurry and avoid agglomeration or gelation.

[0029] In a third aspect, the present application further provides a positive electrode tab, comprising:

[0030] a positive electrode current collector; and

[0031] a positive electrode active material layer, which is arranged on at least one surface of the positive electrode current collector; the positive electrode active material layer is prepared according to the positive electrode slurry described above.

[0032] In some embodiments, the positive electrode active material layer comprises lithium-containing sulfonic acid group graphene; optionally, in the positive electrode active material layer, the molar ratio of Li and S is (10-5000): 1.

[0033] In a fourth aspect, the present application further provides a preparation method of a positive electrode tab, comprising the following steps:

[0034] a positive electrode active material layer is prepared on at least one surface of the positive electrode current collector using a positive electrode slurry; the positive electrode slurry is the positive electrode slurry described above.

[0035] In a fifth aspect, the present application further provides a secondary battery, comprising the positive electrode tab described above or prepared according to the preparation method of the positive electrode tab described above.

[0036] In a sixth aspect, the present application further provides a battery module, comprising the secondary battery described above.

[0037] In a seventh aspect, the present application further provides a battery pack, comprising the battery module described above.

[0038] In an eighth aspect, the present application further provides an electric device, comprising at least one selected from the secondary battery described above, the battery module described above and the battery pack described above.

[0039] The details of one or more embodiments of the present application are presented in the following drawings and description, and other features, objects and advantages of the present application will become apparent from the description, drawings and claims. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 a schematic diagram of a secondary battery according to an embodiment of the present application;

[0041] Figure 2 FIG. 1 is a perspective view of a secondary battery according to an embodiment of the present application; Figure 1

[0042] Figure 3 FIG. 2 is a perspective view of a battery module according to an embodiment of the present application;

[0043] Figure 4 FIG. 3 is a perspective view of a battery pack according to an embodiment of the present application;

[0044] Figure 5 FIG. 4 is a perspective view of a battery pack according to an embodiment of the present application; Figure 4

[0045] Figure 6 FIG. 5 is a perspective view of an electric device using a secondary battery according to an embodiment of the present application as a power source;

[0046] BRIEF DESCRIPTION OF DRAWINGS

[0047] 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: secondary battery; 51: case; 52: electrode assembly; 53: cover plate; 6: electric device.

[0048] For a better understanding of those embodiments and / or examples of the application herein disclosed, reference can be made to the accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, presently described embodiments and / or examples, and the best mode presently contemplated of these applications. DETAILED DESCRIPTION

[0049] In order to facilitate the understanding of the present application, a more complete description of the present application will be made with reference to the accompanying drawings. The preferred embodiments of the present application are illustrated in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present application can be more thoroughly and completely understood.

[0050] 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 the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing the specific embodiments of the present application and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0051] ​​The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0053] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0054] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0055] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0056] If not specifically stated, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0057] The present application provides a positive electrode slurry, a preparation method thereof, a positive electrode sheet prepared using the positive electrode slurry, a secondary battery, a battery module, a battery pack, and an electric device. The secondary battery is suitable for various electric devices using batteries, such as mobile phones, portable devices, notebook computers, electric vehicles, electric toys, electric tools, electric vehicles, ships, and spacecraft, such as aircraft, rockets, space shuttles, and spacecraft.

[0058] An embodiment of the present application provides a positive electrode slurry, comprising solid content and water. The solid content comprises a positive electrode active material capable of embedding and discharging lithium ions and lithium-containing graphene.

[0059] The positive electrode slurry of the present application can coat the positive electrode active material with the lithium-containing graphene due to the π-π stacking effect of the lithium-containing graphene, thereby avoiding performance deterioration of the positive electrode active material caused by water. At the same time, the solid content has good dispersibility in the solvent water, good processability, low cost, and environmental friendliness.

[0060] In some embodiments, the lithium-containing graphene at least partially coats the surface of the positive electrode active material. The lithium-containing graphene at least partially coating the surface of the positive electrode active material can form a hydrophilic layer on the surface of the positive electrode active material, improve the dispersibility of the positive electrode active material, and avoid contact between the positive electrode active material and water. In addition, the lithium ions in the lithium-containing graphene can also improve the lithium ion transport on the positive electrode sheet, and the kinetic performance of the secondary battery is better.

[0061] In some embodiments, the lithium-containing graphene comprises lithium-containing sulfonic acid group graphene. The sulfonic acid group in the lithium-containing sulfonic acid group graphene can further improve the dispersibility of the positive electrode active material in the positive electrode slurry through electrostatic repulsion, and the processability of the positive electrode slurry is better.

[0062] In some embodiments, the molar ratio of Li element to S element in the lithium-containing sulfonated graphene is 1:(1-10). Alternatively, the molar ratio of Li element to S element in the lithium-containing sulfonated graphene is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. Further, the molar ratio of Li element to S element in the lithium-containing sulfonated graphene is 1:(1-5). When the molar ratio of Li element to S element in the lithium-containing sulfonated graphene is within the above range, the positive electrode slurry prepared therefrom has better kinetic performance.

[0063] In some embodiments, the molar ratio of C element to S element in the lithium-containing sulfonated graphene is (3-12):1. Alternatively, the molar ratio of C element to S element in the lithium-containing sulfonated graphene is 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or 12:1. When the molar ratio of C element to S element in the lithium-containing sulfonated graphene is within the above range, the dispersion of the solid content in the positive electrode slurry is better.

[0064] The element molar ratio of the lithium-containing sulfonated graphene described above can be tested by methods known in the art. As an example, the element molar ratio of the lithium-containing sulfonated graphene in the present application is tested by a Horiba 7021-H X-ray spectrometer.

[0065] In some embodiments, the mass percentage of the lithium-containing graphene in the solid content is 0.01%-2%. Alternatively, the mass percentage of the lithium-containing graphene in the solid content can be within a range consisting of any of the following values: 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%. Further, the mass percentage of the lithium-containing graphene in the solid content is 0.2%-1.5%. When the mass percentage of the lithium-containing graphene is within the above range, the dispersion of the positive electrode active material in the aqueous positive electrode slurry can be effectively improved, and the deterioration of the positive electrode active material due to water absorption can be avoided.

[0066] In some embodiments, the positive electrode active material comprises LiFe m Mn 1-m PO4, Li(Ni x Co y Mn z Al a Cu b Zn c Ti dat least one of O2, 0≤m≤1, x+y+z+a+b+c+d=1, 0.5≤x<1, 0.05≤y<1, 0≤z<0.5, 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.1, 0≤d≤0.1. Optionally, the positive electrode active material is LiFePO4.

[0067] In some embodiments, the solid content further comprises a dispersant. Optionally, the dispersant comprises at least one of a cationic dispersant and an amphoteric dispersant. Optionally, the dispersant comprises at least one of polyethyleneimine and polyethylene glycol octylphenyl ether. The dispersant synergizes with the lithium-containing graphene to further improve the dispersibility of the positive electrode slurry. In particular, the dispersant interacts with the sulfonic groups on the lithium-containing sulfonic graphene to further improve the dispersibility.

[0068] In some embodiments, the mass percentage of the dispersant in the solid content is 0.01% to 2%. Optionally, the mass percentage of the dispersant in the solid content can be in a range consisting of any of the following values: 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.6%, or 2%. Further, the mass percentage of the dispersant in the solid content is 0.1% to 0.5%. When the mass content of the dispersant is within the above range, the positive electrode slurry has good dispersibility and good processability.

[0069] In some embodiments, the solid content further comprises an aqueous binder. Optionally, the aqueous binder comprises at least one of methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyacrylamide, and acrylonitrile-acrylic acid copolymer and its derivatives. The aqueous binder can be dissolved in solvent water, and the positive electrode slurry has a suitable viscosity and adhesion.

[0070] In some embodiments, the aqueous binder is acrylonitrile-acrylic acid copolymer. Further, the number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300,000 to 2,000,000.

[0071] In some embodiments, the mass percentage of the aqueous binder in the solid content is 0.1% to 5%. Optionally, the mass percentage of the aqueous binder in the solid content can be in a range consisting of any of the following values: 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, or 5%. Further, the mass percentage of the aqueous binder in the solid content is 2% to 4%. When the mass content of the aqueous binder is within the above range, the positive electrode slurry has a suitable viscosity, which is conducive to the preparation of the positive electrode sheet.

[0072] In some embodiments, the solid content further comprises a conductive agent. Optionally, the conductive agent comprises at least one of conductive carbon black, super conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene, and carbon nanotube.

[0073] In some embodiments, the mass percentage of the conductive agent in the solid content is 0.1% to 5%. Optionally, the mass percentage of the conductive agent in the solid content can be in a range consisting of any of 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, or 5%. Further, the mass percentage of the conductive agent in the solid content is 0.5% to 3%.

[0074] In some embodiments, the mass percentage of the solid content in the positive electrode slurry is 40% to 90%. Optionally, the mass percentage of the solid content in the positive electrode slurry is 50% to 70%. The dispersion of the solid content in the positive electrode slurry described above is good, and the mass content of the solid content can reach 90%, further reducing the amount of solvent water.

[0075] In some embodiments, the viscosity of the positive electrode slurry is 100 cp to 10000 cp. Optionally, the viscosity of the positive electrode slurry is 3000 cp to 7000 cp. The viscosity of the positive electrode slurry in the above range is beneficial to subsequent processing to prepare the positive electrode sheet.

[0076] Another embodiment of the present application also provides a preparation method of the positive electrode slurry described above, comprising the following steps:

[0077] Mixing the solid content and water.

[0078] The preparation method of the positive electrode slurry described above prepares the positive electrode slurry by mixing the solid content comprising the positive electrode active material and the lithium-containing graphene with water, and the prepared positive electrode slurry has good dispersion and processability, and the positive electrode active material is not easily deteriorated by water absorption.

[0079] In some embodiments, the step of mixing the solid content and water comprises:

[0080] (1) mixing the positive electrode active material, the lithium-containing graphene, the dispersant, and the conductive agent to prepare a mass material.

[0081] (2) mixing the mass material, the aqueous binder, and the water.

[0082] First, the positive electrode active material, the lithium-containing graphene, the dispersant, and the conductive agent are mixed to prepare a mass material, which can further improve the dispersion of the positive electrode active material in the positive electrode slurry and avoid agglomeration or gelation.

[0083] In addition, the secondary battery, the battery module, the battery pack, and the power utilization device of the present application are described below with appropriate reference to the accompanying drawings.

[0084] In one embodiment of the present application, a secondary battery is provided.

[0085] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions are intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and functions to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0086] Positive electrode sheet

[0087] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material. The positive electrode active material layer of the positive electrode sheet according to the present application is prepared using the positive electrode slurry according to the first aspect described above.

[0088] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode active material layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0089] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material such as aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy on a polymer material base material. The polymer material base material includes a base material such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0090] In some embodiments, the positive electrode active material can be a positive electrode active material for a battery known in the art. Alternatively, the positive electrode active material includes LiFe m Mn 1-m PO4, Li(Ni x Co y Mn z Al a Cu b Zn c Ti dat least one of O2, 0≤m≤1, x+y+z+a+b+c+d=1, 0.5≤x<1, 0.05≤y<1, 0≤z<0.5, 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.1, 0≤d≤0.1. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate having an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or two or more can be used in combination. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also can be referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof. Examples of the lithium-containing phosphate having an olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon.

[0091] In some embodiments, the lithium-containing graphene is further included in the positive electrode active material layer. In some embodiments, the lithium-containing graphene at least partially coats the surface of the positive electrode active material. The lithium ions in the lithium-containing graphene can improve the lithium ion transport of the positive electrode active material layer, thereby improving the kinetic performance of the secondary battery.

[0092] Further, the lithium-containing graphene includes lithium-containing sulfonic acid group graphene. In some embodiments, the lithium-containing sulfonic acid group graphene has a molar ratio of Li element to S element of 1:(1-10). Alternatively, the lithium-containing sulfonic acid group graphene has a molar ratio of Li element to S element of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. Further, the lithium-containing sulfonic acid group graphene has a molar ratio of Li element to S element of 1:(1-5). The lithium-containing sulfonic acid group graphene has a molar ratio of Li element to S element within the above range, and the kinetic performance of the secondary battery is better. In some embodiments, the lithium-containing sulfonic acid group graphene has a molar ratio of C element to S element of (3-12):1. Alternatively, the lithium-containing sulfonic acid group graphene has a molar ratio of C element to S element of 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or 12:1. In some embodiments, the positive electrode active material layer has a molar ratio of Li element to S element of (10-5000):1.

[0093] Specifically, the molar ratio of Li element to S element or the molar ratio of C element to S element in the lithium-containing sulfonic acid group graphene or the positive electrode active material layer can be tested by methods known in the art. As an example, the SEM-EDS test analysis can be performed by a ZEISS sigma300 scanning electron microscope and a Horiba 7021-H X-ray spectrometer.

[0094] In some embodiments, the positive electrode active material layer has a mass percentage of the lithium-containing graphene of 0.01%-2%. Alternatively, the positive electrode active material layer has a mass percentage of the lithium-containing graphene in a range consisting of any of the following values: 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%. Further, the positive electrode active material layer has a mass percentage of the lithium-containing graphene of 0.2%-1.5%.

[0095] In some embodiments, the positive electrode active material layer further optionally includes a dispersant. Alternatively, the dispersant includes at least one of a cationic dispersant and an amphoteric dispersant. As an example, the dispersant includes at least one of polyethyleneimine and polyethylene glycol octylphenyl ether.

[0096] In some embodiments, the mass percentage of the dispersant in the positive electrode active material layer is 0.01% to 2%. Alternatively, the mass percentage of the dispersant in the positive electrode active material layer can be in a range consisting of any of the following values: 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.6%, or 2%. Further, the mass percentage of the dispersant in the positive electrode active material layer is 0.1% to 0.5%.

[0097] In some embodiments, the positive electrode active material layer further optionally includes a water-based binder. As an example, the water-based binder can include at least one of methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyacrylamide, and acrylonitrile-acrylic acid copolymer and its derivatives. In some embodiments, the water-based binder is acrylonitrile-acrylic acid copolymer. Further, the number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300,000 to 2,000,000.

[0098] In some embodiments, the mass percentage of the water-based binder in the positive electrode active material layer is 0.1% to 5%. Alternatively, the mass percentage of the water-based binder in the positive electrode active material layer can be in a range consisting of any of the following values: 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, or 5%. Further, the mass percentage of the water-based binder in the positive electrode active material layer is 2% to 4%.

[0099] In some embodiments, the positive electrode active material layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of conductive carbon black, super conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene, and carbon nanotube. In some embodiments, the mass percentage of the conductive agent in the positive electrode active material layer is 0.1% to 5%. Alternatively, the mass percentage of the conductive agent in the positive electrode active material layer can be in a range consisting of any of the following values: 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, or 5%. Further, the mass percentage of the conductive agent in the positive electrode active material layer is 0.5% to 3%.

[0100] In some embodiments, the positive electrode sheet can be prepared by coating the positive electrode slurry described above on a positive electrode current collector, and then performing processes such as drying and cold pressing to obtain the positive electrode sheet.

[0101] Negative electrode sheet

[0102] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.

[0103] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode active material layer is provided on either one or both of the two surfaces of the negative electrode current collector.

[0104] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on a polymer material base layer. The polymer material base layer includes a base layer such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0105] In some embodiments, the negative electrode active material can employ a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0106] In some embodiments, the negative electrode active material layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0107] In some embodiments, the negative electrode active material layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0108] In some embodiments, the negative electrode active material layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0109] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector; and drying, cold-pressing, or the like to obtain the negative electrode sheet.

[0110] Electrolyte

[0111] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as desired. For example, the electrolyte can be liquid, gel, or solid.

[0112] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0113] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0114] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0115] In some embodiments, the electrolyte solution can optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive that improves certain properties of the battery, such as an additive that improves overcharge performance of the battery, an additive that improves high-temperature or low-temperature performance of the battery, and the like.

[0116] Separator

[0117] In some embodiments, the secondary battery further includes a separator. The type of separator is not particularly limited in the present application and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0118] In some embodiments, the separator film can be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0119] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly through a winding process or a stacking process.

[0120] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte.

[0121] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0122] The shape of the secondary battery is not particularly limited, and can be cylindrical, square, or any other shape. For example, Figure 1 is a square structure as an example of a secondary battery 5.

[0123] In some embodiments, referring to Figure 2 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0124] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0125] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0126] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of secondary batteries 5 can be accommodated in the accommodation space.

[0127] In some embodiments, the above-described battery module can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0128] Figure 4 and Figure 5 is a battery pack 1 as an example. Referring to Figure 4 and Figure 5 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0129] In addition, the application also provides a power utilization device, which includes at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0130] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0131] Figure 6 is a power utilization device 6 as an example. The power utilization device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the power utilization device, a battery pack or a battery module can be used.

[0132] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thin and light, and a secondary battery can be used as a power supply.

[0133] Embodiments

[0134] Hereinafter, the examples of the present application will be described. The examples described below are exemplary and are for the purpose of explanation of the present application and cannot be construed as a limitation of the present application. In the examples, the specific techniques or conditions not mentioned are performed in accordance with the techniques or conditions described in the literature in the field or in accordance with the product manual. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained commercially.

[0135] Example 1:

[0136] Preparation of positive electrode sheet: the positive electrode active material lithium iron phosphate (LFP), lithium-containing sulfonic acid group graphene, conductive agent, dispersant were kneaded uniformly at a weight ratio of 96.5:0.2:1:0.3, then the mixed kneaded mass of the positive electrode active material lithium iron phosphate, lithium-containing sulfonic acid group graphene, conductive agent, dispersant, and the aqueous binder were mixed at a weight ratio of 98:2, wherein the molar ratio of Li / S of the lithium-containing sulfonic acid group graphene was 1:1, the molar ratio of C / S was 6:1, the dispersant was polyethyleneimine, and the aqueous binder was LA-133 type aqueous binder; the rest was stirred and mixed uniformly with deionized water as a solvent to obtain a positive electrode slurry with a solid content of 50%; then the positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and cut to obtain the positive electrode sheet.

[0137] Preparation of negative electrode sheet: the active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickening agent sodium hydroxymethyl cellulose (CMC) were dispersed in a solvent deionized water at a mass ratio of 96.2:0.8:0.8:1.2, and then mixed uniformly to prepare a negative electrode slurry; the negative electrode slurry was uniformly coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and cut to obtain the negative electrode sheet.

[0138] Preparation of electrolyte: in an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3 / 7, 12.5% LiPF6 lithium salt was dissolved in the organic solvent, and then stirred uniformly to obtain the electrolyte.

[0139] Separator: a polypropylene film was used as the separator.

[0140] Preparation of secondary battery: the positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, with the separator between the positive and negative electrode sheets to play a role of isolation, then wound to obtain a bare cell, the bare cell was welded with tabs, and then put into an aluminum shell, and baked at 80°C to remove water, then injected with electrolyte and sealed to obtain a non-charged battery. The non-charged battery was sequentially subjected to processes of standing, hot and cold pressing, formation, shaping, capacity testing, and the like to obtain the secondary battery product.

[0141] Examples 2-6:

[0142] Examples 2-6 differ from Example 1 in that the amount of lithium-containing sulfonic group graphene in the positive electrode slurry is different.

[0143] Examples 7-8:

[0144] Examples 7-8 differ from Example 1 in that the C / S molar ratio of lithium-containing sulfonic group graphene in the positive electrode slurry is different.

[0145] Examples 9-11:

[0146] Examples 9-11 differ from Example 1 in that the Li / S molar ratio of lithium-containing sulfonic group graphene in the positive electrode slurry is different.

[0147] Examples 12-16:

[0148] Examples 12-16 differ from Example 1 in that the amount of dispersant in the positive electrode slurry is different.

[0149] Examples 17-19:

[0150] Examples 17-19 differ from Example 1 in that the amount of aqueous binder in the positive electrode slurry is different.

[0151] Example 20:

[0152] Example 20 differs from Example 1 in that the dispersant in the positive electrode slurry is polyethylene glycol octylphenyl ether.

[0153] Example 21:

[0154] Example 21 differs from Example 1 in that the aqueous binder in the positive electrode slurry is sodium alginate.

[0155] Example 22:

[0156] Example 22 differs from Example 1 in that the positive electrode active material in the positive electrode slurry is LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811).

[0157] Comparative Example 1:

[0158] Comparative Example 1 differs from Example 1 in that the positive electrode slurry does not contain lithium-containing graphene and a dispersant.

[0159] Comparative Example 2:

[0160] Comparative Example 2 differs from Example 1 in that the positive electrode slurry does not contain lithium-containing graphene.

[0161] The lithium-containing sulfonated graphene used in the above examples can be obtained by market approach, or prepared by suitable methods known to those skilled in the art. As an example, the preparation method of lithium-containing sulfonated graphene is as follows: sulfonated graphene is uniformly dispersed in DMF, then lithium hydroxide is added and stirred for 1-4 h, dried at 100-120°C to obtain lithium-containing sulfonated graphene. The type of sulfonated graphene and the amount of sulfonated graphene and lithium hydroxide are adjusted according to the element molar ratio in Table 1. The element composition of the lithium-containing sulfonated graphene prepared above can also be tested by Horiba 7021-H X-ray spectrometer, so as to obtain the C / S molar ratio and Li / S molar ratio of the lithium-containing sulfonated graphene.

[0162] The positive electrode slurry compositions of Examples 1-22 and Comparative Examples 1-2 are recorded in Table 1.

[0163] Test section:

[0164] Positive electrode slurry particle size test:

[0165] The prepared positive electrode slurry was placed for 10 minutes, and an appropriate amount of positive electrode slurry was added to 20 ml of deionized water (concentration ensured 8%-12% opacity), and ultrasonic treatment was performed for 5 min (53 KHz / 120 W) to completely disperse, as the sample to be tested; the Dv50 particle size of the sample to be tested was determined by using a Malvern 2000 (MasterSizer 2000) laser particle size instrument according to the standard procedure GB / T19077-2016 / ISO 13320:2009.

[0166] Secondary battery initial gram capacity test:

[0167] Taking Example 1 as an example, at 25°C, the secondary battery was charged at 1 / 3C constant current to 3.65V (NCM811 was 4.25V), then charged at 3.65V (NCM811 was 4.25V) constant voltage to the current was 0.05C, and then rested for 5 min, and then discharged at 1 / 3C to 2.5V (NCM811 was 2.8V). The obtained capacity was divided by the mass of the positive electrode active material in the positive electrode, and was recorded as the initial gram capacity Cw.

[0168] Direct current impedance test:

[0169] Take Example 1 as an example, the secondary battery is charged at a current of 1.5C to 3.65V (4.25V for NCM811), and then charged at a constant voltage of 0.05C. Rest for 30 min; discharge at a current of 0.1C for 10s (take a point every 0.1s, and record the corresponding voltage value U1), and discharge at a current of 1C for 360s (take a point every 0.1s, and record the corresponding voltage value U2). Repeat the charging and discharging steps 5 times. "1C" is the current value that completely discharges the battery capacity within 1 hour. The DCR is calculated according to the following formula: R = (U2-U1) / (1C-0.1C). The DCR described in this application is the value at 50% SOC (state of charge).

[0170] High-rate current cycle performance test:

[0171] Take Example 1 as an example, the secondary battery is charged at a current of 1.5C to 3.65V (4.25V for NCM811), and then charged at a constant voltage of 0.05C. Rest for 30 min; discharge at a current of 0.1C for 10s (take a point every 0.1s, and record the corresponding voltage value U1), and discharge at a current of 1C for 360s (take a point every 0.1s, and record the corresponding voltage value U2). Repeat the charging and discharging steps 5 times. "1C" is the current value that completely discharges the battery capacity within 1 hour. The DCR is calculated according to the following formula: R = (U2-U1) / (1C-0.1C). The DCR described in this application is the value at 50% SOC (state of charge).

[0172] The electrochemical performance test data of the secondary batteries of Examples 1-22 and Comparative Examples 1-2 are recorded in Table 2.

[0173] Table 1 Composition of the positive electrode slurry of Examples 1-22 and Comparative Examples 1-2

[0174]

[0175]

[0176] Note: The mass content in Table 1 represents the mass content of the substance in the solid content of the positive electrode slurry.

[0177] Table 2 Electrochemical performance of secondary batteries of Examples 1-22 and Comparative Examples 1-2

[0178]

[0179]

[0180] As can be seen from the data in Table 1 and Table 2, the positive electrode slurries of Comparative Examples 1-2 do not contain lithium-containing graphene, and the Dv50 particle size of the positive electrode slurries is 1.37 μm-1.51 μm. The initial gram capacity of the secondary batteries of Comparative Examples 1-2 is 156 mAh / g, the DCR is 1.58 Ω-1.75 Ω, and the DCR growth rate after 100 cycles at 25 C is 27%-29%.

[0181] Compared with Comparative Examples 1-2, lithium-containing graphene is added to the positive electrode slurries of Examples 1-21, and the Dv50 particle size of the positive electrode slurries is 1.07 μm-1.33 μm, and the dispersion of the positive electrode slurries is good. The initial gram capacity of the secondary batteries of Examples 1-21 is 158 mAh / g-160 mAh / g, which is higher than that of the secondary batteries of Comparative Examples 1-2, indicating that the secondary batteries of Examples 1-22 are less likely to deteriorate due to water absorption of lithium iron phosphate during preparation, resulting in capacity reduction. In addition, the DCR of the secondary batteries of Examples 1-21 is 1.38 Ω-1.67 Ω, and the DCR growth rate after 100 cycles at 25 C is 11%-23%. Lithium ions in lithium-containing graphene can improve the lithium ion transport of the secondary batteries, thereby reducing the DCR. Lithium-containing graphene is at least partially coated on the surface of the positive electrode active material, so that the secondary batteries have good cycle performance and are less likely to deteriorate during high-rate charging and discharging. Among them, the content of the binder in Example 21 is lower, and the adhesion of the positive electrode sheet is slightly lower than that of the positive electrode sheets of Examples 1-20, so that the DCR is higher and the DCR growth during high-rate charging and discharging is more.

[0182] In the secondary battery of Example 22, the positive electrode active material is NCM811, the Dv50 particle size of the positive electrode slurry is 4.70 μm, and the dispersion of the positive electrode slurry is good. The initial gram capacity of the secondary battery is 174 mAh / g, the DCR is 1.37 Ω, and the DCR growth rate after 100 cycles at 25 C is 11%, and the secondary battery has good kinetic performance and cycle performance.

[0183] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the description.

[0184] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A positive electrode slurry for a lithium ion battery, characterized by, The solid content and water; The solid content includes a positive electrode active material capable of intercalating and deintercalating lithium ions and a lithium-containing graphene.

2. The positive slurry for a lithium ion battery according to claim 1, wherein The lithium-containing graphene is at least partially coated on the surface of the positive electrode active material.

3. The positive slurry for a lithium ion battery according to claim 1, wherein The lithium-containing graphene includes lithium-containing sulfonated graphene.

4. The positive slurry for a lithium ion battery according to claim 3, wherein The lithium-containing sulfonated graphene has a molar ratio of Li to S of 1: (1-10).

5. The positive slurry for a lithium ion battery according to claim 4, wherein The lithium-containing sulfonated graphene has a molar ratio of Li to S of 1: (1-5).

6. The positive slurry for a lithium ion battery according to claim 3, wherein The lithium-containing sulfonated graphene has a molar ratio of C to S of (3-12):

1.

7. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, characterized by, In the solid content, the mass percentage of the lithium-containing graphene is 0.01%-2%.

8. The positive slurry for a lithium-ion battery according to claim 7, wherein In the solid content, the mass percentage of the lithium-containing graphene is 0.2%-1.5%.

9. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, characterized by, The positive electrode active material includes LiFe m Mn 1-m PO4, Li(Ni x Co y Mn z Al a Cu b Zn c Ti d )O2, 0≤m≤1, x+y+z+a+b+c+d=1, 0.5≤x<1, 0.05≤y<1, 0≤z<0.5, 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.1, 0≤d≤0.

1.

10. The positive slurry for a lithium ion battery according to claim 9, wherein The positive electrode active material is LiFePO4.

11. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, characterized by, The solid content further includes a dispersant, and the dispersant includes at least one of a cationic dispersant and an amphoteric dispersant.

12. The positive slurry for a lithium-ion battery according to claim 11, wherein The dispersant includes at least one of polyethyleneimine and polyethylene glycol octylphenyl ether.

13. The positive slurry for a lithium ion battery according to claim 11, wherein In the solid content, the mass percentage of the dispersant is 0.01%-2%.

14. The positive slurry for a lithium-ion battery according to claim 13, wherein In the solid content, the mass percentage of the dispersant is 0.1%-0.5%.

15. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, wherein The solid content further includes an aqueous binder.

16. The positive slurry for a lithium-ion battery according to claim 15, wherein The aqueous binder includes at least one of methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyacrylamide, and acrylonitrile-acrylic acid copolymer and its derivatives.

17. The cathode slurry for a lithium ion battery according to claim 16, wherein The aqueous binder is acrylonitrile-acrylic acid copolymer.

18. The cathode slurry for a lithium ion battery according to claim 17, wherein The acrylonitrile-acrylic acid copolymer has a number average molecular weight of 300,000-2,000,000.

19. The positive slurry for a lithium-ion battery according to claim 15, wherein In the solid content, the mass percentage of the aqueous binder is 0.1%-5%.

20. The positive slurry for a lithium-ion battery according to claim 19, wherein In the solid content, the mass percentage of the aqueous binder is 2%-4%.

21. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, wherein The solid content further includes a conductive agent.

22. The cathode slurry for a lithium ion battery according to claim 21, wherein The conductive agent includes at least one of conductive carbon black, super conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene, and carbon nanotube.

23. The cathode slurry for a lithium ion battery according to claim 21, wherein In the solid content, the mass percentage of the conductive agent is 0.1%-5%.

24. The cathode slurry for a lithium ion battery according to claim 23, wherein In the solid content, the mass percentage of the conductive agent is 0.5%-3%.

25. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, wherein In the positive electrode slurry, the mass percentage of the solid content is 40%-90%.

26. The cathode slurry for a lithium ion battery according to claim 25, wherein In the positive electrode slurry, the mass percentage of the solid content is 50%-70%.

27. The positive slurry for a lithium ion battery according to any one of claims 1 to 6, wherein The positive electrode slurry has a viscosity of 100 cp-10,000 cp.

28. The cathode slurry for a lithium ion battery according to claim 27, wherein The positive electrode slurry has a viscosity of 3,000 cp-7,000 cp.

29. The process for the preparation of a cathode slurry for lithium-ion batteries according to any one of claims 1 to 28, characterized in that, The method includes the following steps: The solid content and the water are mixed.

30. The method of preparing a cathode slurry for a lithium-ion battery of claim 29, wherein, The step of mixing the solid content and the water includes: The positive electrode active material, the lithium-containing graphene, the dispersant, and the conductive agent are mixed to prepare a mass material; The mass material, the aqueous binder, and the water are mixed.

31. A positive electrode sheet characterized by comprising: The method includes: A positive electrode current collector; And A positive electrode active material layer is arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer is prepared from the positive electrode slurry for lithium ion batteries according to any one of claims 1-28.

32. The cathode sheet of claim 31, wherein, The positive electrode active material layer includes lithium-containing sulfonated graphene.

33. The cathode sheet of claim 32, wherein, In the positive electrode active material layer, the molar ratio of Li element to S element is (10-5000):

1.

34. A method of making a positive electrode sheet, the method comprising: comprising the steps of: producing a positive electrode active material layer on at least one surface of a positive electrode current collector using a positive electrode slurry; the positive electrode slurry being the positive electrode slurry according to any one of claims 1-28.

35. A secondary battery, characterized by comprising: a positive electrode tab produced by the method according to any one of claims 31-33.

36. A battery module, comprising: a secondary battery comprising the secondary battery according to claim 35.

37. A battery pack, characterized by a battery module comprising the battery module according to claim 36.

38. An electrical device, comprising: at least one selected from the group consisting of the secondary battery according to claim 35, the battery module according to claim 36, and the battery pack according to claim 37.

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