Positive pole piece and preparation method thereof, battery and power utilization device

Abstract

The invention discloses a positive pole piece and a preparation method thereof, a battery and a power utilization device, and belongs to the technical field of new energy storage. The positive pole piece comprises a current collector, and a conductive layer and a positive active layer which are sequentially arranged on at least one side of the current collector; the conductive layer is arranged between the current collector and the positive active layer; the conductive layer comprises a first carbon nanotube, a first conductive agent and a first adhesive; the positive electrode active layer comprises a carbon nanotube coated and modified manganese oxide, a second conductive agent and a second adhesive; the carbon nanotube coated and modified manganese oxide comprises a second carbon nanotube and a manganese oxide; and the second carbon nanotubes at least partially coat the surface of the manganese oxide. The positive pole piece provided by the invention has improved loading capacity and conductivity of the positive active material, and can improve the cycle performance of the battery when being used for the battery.

Description

Technical Field

[0001] This application relates to the field of new energy storage technology, and in particular to positive electrode sheets and their preparation methods, batteries and power devices. Background Technology

[0002] Zinc-manganese batteries have attracted much attention in the energy storage field due to their advantages such as high safety, low cost, environmental friendliness, and relatively high theoretical energy density. Traditional zinc-manganese batteries mostly use wet processes to prepare the positive electrode sheets.

[0003] However, in wet processing, active materials are typically mixed with binders, conductive agents, etc., to form a slurry, which is then coated onto the current collector. If the loading of active materials is high, the viscosity and yield stress of the slurry will increase significantly, leading to uneven distribution during coating. This can result in problems such as active material detachment and cracking in the prepared electrode, severely affecting the structural stability and performance of the battery. Therefore, wet processing limits the loading of active materials. Simultaneously, manganese ions in manganese-containing active materials easily dissolve into the electrolyte, further reducing the effective amount of active material. This results in fewer active materials participating in the reaction during charge and discharge, leading to low electron and ion transport efficiency and significantly limiting the cycle performance of zinc-manganese batteries. Summary of the Invention

[0004] Therefore, the main objective of this application is to provide a positive electrode sheet to improve the loading of active material and the conductivity of the positive electrode sheet, thereby improving the cycle performance of the battery.

[0005] In a first aspect, a positive electrode is provided, the positive electrode comprising a current collector and a conductive layer and a positive active layer sequentially disposed on at least one side of the current collector; the conductive layer is disposed between the current collector and the positive active layer;

[0006] The conductive layer comprises a first carbon nanotube, a first conductive agent, and a first adhesive;

[0007] The positive electrode active layer comprises carbon nanotube-coated modified manganese oxide, a second conductive agent, and a second binder.

[0008] The carbon nanotube-coated modified manganese oxide comprises a second carbon nanotube and a manganese oxide; the second carbon nanotube is at least partially coated on the surface of the manganese oxide.

[0009] In some embodiments, one or more of the following features are satisfied:

[0010] (1) The first conductive agent includes at least one of Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite and graphene;

[0011] (2) The first adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, CMC, PVA and cellulose adhesives;

[0012] (3) The mass ratio of the first carbon nanotube to the first conductive agent is (0.5-15):3;

[0013] (4) The mass ratio of the first carbon nanotube to the first adhesive is (2-8):(1-5).

[0014] In some embodiments, one or more of the following features are satisfied:

[0015] (1) The manganese oxide includes at least one of manganese dioxide, manganese trioxide and manganese tetroxide;

[0016] (2) The mass ratio of the manganese oxide to the second carbon nanotube is 10:(0.02-1.5).

[0017] In some embodiments, one or more of the following features are satisfied:

[0018] (1) The second conductive agent includes at least one of Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite and graphene;

[0019] (2) The second adhesive includes polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, CMC, PVA and cellulose adhesives;

[0020] (3) The mass ratio of the carbon nanotube-coated modified manganese oxide to the second conductive agent is (6-9):(0.5-4);

[0021] (4) The mass ratio of the carbon nanotube-coated modified manganese oxide to the second adhesive is (6-9):(0.5-3).

[0022] In some embodiments, the thickness of the conductive layer is 2 μm to 8 μm;

[0023] And / or the thickness of the positive electrode active layer is 40μm~200μm.

[0024] A second aspect of this application provides a method for preparing a positive electrode sheet, comprising the following steps:

[0025] A conductive layer slurry containing a first carbon nanotube, a first conductive agent, a first binder, and a first solvent is coated onto at least one side surface of the current collector to form a current collector containing a conductive layer.

[0026] The carbon nanotube-coated manganese oxide was prepared by mixing and reacting the second carbon nanotube and manganese oxide in the presence of water and then drying.

[0027] The positive electrode sheet is prepared by coating a positive electrode slurry containing carbon nanotube-coated modified manganese oxide, a second conductive agent, a second binder, and a second solvent onto a conductive layer of a current collector containing a conductive layer.

[0028] In some embodiments, one or more of the following features are satisfied:

[0029] (1) The solid content of the conductive layer slurry is 4wt%~10wt%;

[0030] (2) The solid content of the positive electrode slurry is 20wt%~45wt%;

[0031] (3) Based on a content of 100 wt% for the second carbon nanotube, manganese oxide, and the third solvent, the content of the third solvent is 20 wt% to 80 wt%;

[0032] (4) The first solvent includes at least one of N-methylpyrrolidone, water, and ethanol;

[0033] (5) The second solvent includes at least one of N-methylpyrrolidone, water, and ethanol;

[0034] (6) The third solvent includes at least one of N-methylpyrrolidone, water, and ethanol;

[0035] (7) The conditions for the mixed reaction include: reaction temperature 40℃~60℃; reaction time 12h~36h; stirring speed 200rpm~500rpm;

[0036] (8) Drying conditions include: drying temperature of 90℃~110℃.

[0037] A third aspect of this application provides a positive electrode sheet prepared by the preparation method described in the second aspect.

[0038] A fourth aspect of this application provides a battery comprising the positive electrode sheet described in the first or third aspect.

[0039] A fifth aspect of this application provides an electrical device comprising the battery described in the fourth aspect.

[0040] The beneficial effects of this application are:

[0041] This application incorporates a conductive layer containing first carbon nanotubes on the current collector. This conductive layer exhibits excellent contact with the positive electrode active material, effectively increasing the contact sites. The carbon nanotube-coated manganese oxide possesses a higher surface area and more active sites. Furthermore, the carbon nanotube-coated manganese oxide exhibits good compatibility with the first carbon nanotubes in the conductive layer, facilitating bonding and increasing the loading of the positive electrode active material. This also reduces the solubility of manganese ions in the electrolyte, thereby increasing the effective amount of active material. Additionally, it improves conductivity, enhancing electron and ion transport efficiency and reducing internal resistance. Consequently, the cycle performance of the battery can be improved. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer and to provide a more thorough and comprehensive understanding of the disclosure of this application, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. The described embodiments are only a part of the embodiments of this application, and not all of them.

[0043] The implementation of this application is described in detail below. This embodiment is implemented based on the technical solution of this application, and provides detailed implementation methods and specific operation processes, but the protection scope of this application is not limited to the following embodiment.

[0044] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0045] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0046] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "at least one" or "at least one" means one or more than two.

[0047] In this application, terms such as "further" and "especially" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0048] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0049] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include numerical interval types such as percentage intervals, ratio intervals, and proportion intervals.

[0050] In this application, unless otherwise specified, the temperature parameters are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control. Fluctuations are permitted within ranges such as ±5℃, ±4℃, ±3℃, ±2℃, and ±1℃.

[0051] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0052] In this application, unless otherwise specified, the temperature parameter can be either constant temperature treatment or treatment within a certain temperature range. The constant temperature treatment allows temperature fluctuations within the precision range controlled by the instrument. The room temperature mentioned in this application refers to 0-40℃, preferably 10℃-35℃, and more preferably 20℃-30℃.

[0053] Traditional zinc-manganese batteries typically use a wet process to prepare the positive electrode. However, in the wet process, the active material is usually mixed with binders, conductive agents, etc., to form a slurry, which is then coated onto the current collector. If the loading of the active material is high, the viscosity and yield stress of the slurry will increase significantly, and uneven distribution is likely to occur during the coating process. This can lead to problems such as active material shedding and cracking in the prepared electrode, severely affecting the structural stability and performance of the battery. Therefore, the wet process limits the loading of active material. At the same time, manganese ions in manganese-containing active materials easily dissolve into the electrolyte, further reducing the effective amount of active material. This results in less active material participating in the reaction during charge and discharge, low electron and ion transport efficiency, and greatly limiting the cycle performance of zinc-manganese batteries.

[0054] In view of this, a first aspect of this application provides a positive electrode sheet, the positive electrode sheet comprising a current collector and a conductive layer and a positive active layer sequentially disposed on at least one side of the current collector; the conductive layer is disposed between the current collector and the positive active layer;

[0055] The conductive layer comprises a first carbon nanotube, a first conductive agent, and a first adhesive;

[0056] The positive electrode active layer comprises carbon nanotube-coated modified manganese oxide, a second conductive agent, and a second binder.

[0057] The carbon nanotube-coated modified manganese oxide comprises a second carbon nanotube and a manganese oxide; the second carbon nanotube is at least partially coated on the surface of the manganese oxide.

[0058] This application incorporates a conductive layer containing first carbon nanotubes on the current collector. This conductive layer exhibits excellent contact with the positive electrode active material, effectively increasing the contact sites. The carbon nanotube-coated manganese oxide possesses a higher surface area and more active sites. Furthermore, the carbon nanotube-coated manganese oxide exhibits good compatibility with the first carbon nanotubes in the conductive layer, facilitating bonding and increasing the loading of the positive electrode active material. This also reduces the solubility of manganese ions in the electrolyte, thereby increasing the effective amount of active material. Additionally, it improves conductivity, enhancing electron and ion transport efficiency and reducing internal resistance. Consequently, the cycle performance of the battery can be improved.

[0059] In some embodiments, the first conductive agent includes at least one selected from Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite, and graphene.

[0060] In some embodiments, the first adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and cellulose adhesives.

[0061] In some embodiments, the mass ratio of the first carbon nanotube to the first conductive agent is (0.5-15):3, such as 0.5:3, 1:3, 3:3, 5:3, 10:3, 12:3, 14:3, 15:3, etc.

[0062] In some embodiments, the mass ratio of the first carbon nanotube to the first adhesive is (2-8):(1-5), for example (2, 4, 6 or 8):(1, 3 or 5).

[0063] In some embodiments, the manganese oxide includes at least one of manganese dioxide, manganese trioxide, and manganese tetroxide.

[0064] In some embodiments, the mass ratio of the manganese oxide to the second carbon nanotube is 10:(0.02-1.5), such as 10:0.02, 10:0.1, 10:0.5, 10:1, 10:1.5, etc.

[0065] In some embodiments, the second conductive agent includes at least one selected from Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite, and graphene.

[0066] In some embodiments, the second adhesive comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and cellulose adhesives.

[0067] In some embodiments, the mass ratio of the carbon nanotube-coated modified manganese oxide to the second conductive agent is (6-9):(0.5-4), for example (6, 7, 8 or 9):(0.5, 1, 2, 3 or 4).

[0068] In some embodiments, the mass ratio of the carbon nanotube-coated modified manganese oxide to the second binder is (6-9):(0.5-3), (6, 7, 8 or 9):(0.5, 1, 2 or 3).

[0069] In some embodiments, the thickness of the conductive layer is 2μm to 8μm, such as 2μm, 4μm, 6μm, 8μm, etc.

[0070] In some embodiments, the thickness of the positive electrode active layer is 40μm to 200μm, such as 40μm, 80μm, 100μm, 120μm, 160μm, 200μm, etc.

[0071] A second aspect of this application provides a method for preparing a positive electrode sheet, comprising the following steps:

[0072] A conductive layer slurry containing a first carbon nanotube, a first conductive agent, a first binder, and a first solvent is coated onto at least one side surface of the current collector to form a current collector containing a conductive layer.

[0073] The carbon nanotube-coated manganese oxide was prepared by mixing and reacting the second carbon nanotube and manganese oxide in the presence of water and then drying.

[0074] The positive electrode sheet is prepared by coating a positive electrode slurry containing carbon nanotube-coated modified manganese oxide, a second conductive agent, a second binder, and a second solvent onto a conductive layer of a current collector containing a conductive layer.

[0075] In some embodiments, the solid content of the conductive layer slurry is 4wt% to 10wt%, for example, 4wt%, 6wt%, 8wt%, 10wt%, etc.

[0076] In some embodiments, the solid content of the positive electrode slurry is 20wt% to 45wt%, such as 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, etc.

[0077] In some embodiments, based on the content of the second carbon nanotube, manganese oxide and the third solvent being 100 wt%, the content of the third solvent is 20 wt% to 80 wt%, for example 20 wt%, 40 wt%, 60 wt%, 80 wt%, etc.

[0078] In some embodiments, the first solvent includes at least one of N-methylpyrrolidone, water, and ethanol.

[0079] In some embodiments, the second solvent includes at least one of N-methylpyrrolidone, water, and ethanol.

[0080] In some embodiments, the third solvent includes at least one of N-methylpyrrolidone, water, and ethanol.

[0081] In some embodiments, the conditions for the mixing reaction include: a reaction temperature of 40°C to 60°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, etc.; a reaction time of 12h to 36h, such as 12h, 18h, 24h, 30h, 36h, etc.; and a stirring speed of 200rpm to 500rpm, such as 200rpm, 300rpm, 400rpm, 500rpm, etc.

[0082] In some embodiments, the drying conditions include a drying temperature of 90°C to 110°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, etc.

[0083] A third aspect of this application provides a positive electrode sheet prepared by the preparation method described in the second aspect.

[0084] A fourth aspect of this application provides a battery comprising the positive electrode sheet described in the first or third aspect.

[0085] A fifth aspect of this application provides an electrical device comprising the battery described in the fourth aspect.

[0086] In one specific example, the cellulose-based adhesive includes at least one of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, microcrystalline cellulose, and hydroxyethyl cellulose.

[0087] In a specific example, the current collector includes at least one of carbon cloth, carbon paper, stainless steel mesh, stainless steel foil, titanium mesh, titanium foil, and nickel foam.

[0088] In one specific example, the battery includes a zinc-manganese battery, and further includes an aqueous zinc-manganese battery.

[0089] In a specific example, the battery includes positive and negative electrodes, a separator membrane spaced between the positive and negative electrodes, and an electrolyte.

[0090] The positive electrode can be the positive electrode as described above.

[0091] The active material of the negative electrode includes zinc or manganese metal.

[0092] In this application, there are no particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0093] In a specific example, the material of the separator may include one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film; there are no particular limitations. When the separator is a multi-layer composite film, the materials of each layer may be the same or different; there are no particular limitations.

[0094] Electrolytes function to conduct ions between positive and negative electrodes. This application does not impose any particular restrictions on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0095] In a specific example, the electrolyte is an electrolyte solution. The electrolyte solution consists of an electrolyte salt and a solvent.

[0096] In a specific example, when the battery is a lithium-ion battery, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0097] In a specific example, when the battery is a lithium-ion battery, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), fluoroethylene carbonate (FEC), 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.

[0098] In a specific example, when the battery is a zinc-manganese battery, the electrolyte can be one or more of ammonium chloride, zinc chloride, potassium hydroxide, sodium hydroxide, zinc sulfate, and manganese sulfate, and the solvent can be water.

[0099] In a specific example, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0100] In one specific example, the battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0101] In a specific example, the battery's outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic; further, non-limiting examples of plastics can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0102] In a specific example, the electrical device can be a mobile phone, laptop, smartwatch, electric vehicle, medical device, portable charging station, aerospace equipment, smart home, or energy storage power station. The energy storage power station can be a photovoltaic energy storage power station, a wind power energy storage power station, a hydropower energy storage power station, a thermal power energy storage power station, etc.

[0103] Unless otherwise specified, the raw materials used in the following experiments can be purchased from the market.

[0104] Polyvinylidene fluoride (PVDF): purchased from Arkema, France;

[0105] Aqueous carbon nanotube dispersion: Model CNT-W-5, solid content 5wt%, purchased from Zhejiang Rifang Nanobiotechnology Co., Ltd.

[0106] Oily carbon nanotube dispersion: Model CNT-W-5, solvent is NMP, solid content is 5wt%, purchased from Zhejiang Rifang Nanobiotechnology Co., Ltd.

[0107] Super P Li and activated carbon were purchased from Toray Industries, Inc., Japan.

[0108] Carbon black: purchased from Shenzhen Suiheng Technology Co., Ltd.;

[0109] Graphite: Purchased from Lion Corporation (International) Ltd., Japan;

[0110] Current collector: Stainless steel foil, purchased from Hebei Chaoqun Waterproof Materials Co., Ltd.

[0111] The following are specific examples.

[0112] Example 1

[0113] Preparation method of positive electrode sheet:

[0114] 1) Preparation of current collectors containing conductive layers:

[0115] A binder solution was prepared by dissolving the first binder PVDF (with a mass ratio of first carbon nanotubes to binder of 2.5:1 based on solid content) in N-methylpyrrolidone.

[0116] The first carbon nanotube (oil-based carbon nanotube dispersion) and the first conductive agent (activated carbon, carbon black and graphite in a mass ratio of 1:1:1, and the mass ratio of the first carbon nanotube to the first conductive agent in terms of solid content is 4:3) were mixed and added to the binder solution. The mixture was stirred at 450 rpm for 3 hours to ensure complete and uniform mixing, thus preparing a conductive layer slurry (solid content of 6 wt%).

[0117] Spread out the current collector (stainless steel foil), and evenly coat the conductive layer slurry on both sides of the current collector. After drying in a 100°C oven, place it in a roller press and roll it at room temperature to obtain a current collector containing a conductive layer; the thickness of the conductive layer is 5μm.

[0118] 2) Preparation of carbon nanotube-coated modified manganese oxides:

[0119] Manganese dioxide powder, second carbon nanotubes (aqueous carbon nanotube dispersion), and water were mixed (the solid content in the mixed solution was 30 wt%; the mass ratio of manganese dioxide to second carbon nanotubes was 10:1 based on solid content). The mixture was stirred at 350 rpm for 24 h at 45 °C. The mixture was then filtered, and during the filtration process, it was repeatedly washed with ethanol and water until the pH of the filtrate was neutral. The solid component obtained by filtration was placed in an oven at 100 °C and dried to obtain carbon nanotube-coated modified manganese oxide.

[0120] 3) Carbon nanotube-coated modified manganese oxide, a second conductive agent (super P Li and activated carbon in a mass ratio of 7:2), a second binder (PVDF) and N-methylpyrrolidone are mixed, wherein the mass ratio of carbon nanotube-coated modified manganese oxide, the second conductive agent and the second binder is 7:2:1, to prepare a positive electrode slurry (solid content of 30wt%).

[0121] A positive electrode sheet is prepared by coating a positive electrode slurry onto a conductive layer containing a current collector to form a positive electrode active layer (150 mm thick, double-sided coating).

[0122] Example 2

[0123] Except for the solid content, the mass ratio of the first carbon nanotube to the first conductive agent is 1:3, and the thickness of the conductive layer is 8 μm, the rest is the same as in Example 1.

[0124] Example 3

[0125] Except for the solid content, the mass ratio of the first carbon nanotube to the first conductive agent is 8:3, and the thickness of the conductive layer is 2 μm, the rest is the same as in Example 1.

[0126] Example 4

[0127] Except that the mass ratio of manganese dioxide to the second carbon nanotube is 10:0.02 (the solid content in the mixed solution is 50wt%), and the mass ratio of carbon nanotube-coated modified manganese oxide to the second conductive agent is 6:3, the rest is the same as in Example 1.

[0128] Example 5

[0129] Except that the mass ratio of manganese dioxide to the second carbon nanotube is 10:1.5 (the solid content in the mixed solution is 20wt%), and the mass ratio of carbon nanotube-coated modified manganese oxide to the second conductive agent is 9:1, the rest is the same as in Example 1.

[0130] Example 6

[0131] Except that the first conductive agent is super P Li and the second conductive agent is activated carbon, the rest is the same as in Example 1.

[0132] Example 7

[0133] Except for step 2), which uses an oily carbon nanotube dispersion and solvent (NMP) to prepare carbon nanotube-coated modified manganese oxide, the rest is the same as in Example 1, and the specific process is as follows:

[0134] Manganese dioxide powder, second carbon nanotubes (oil-based nanotube dispersion), and solvent (NMP) were mixed (the solid content in the mixed solution was 6 wt%; the mass ratio of manganese dioxide to second carbon nanotubes was 10:1 based on the solid content). The mixture was stirred at 350 rpm for 24 h at 45 °C. The mixture was then filtered, and the solid components obtained by filtration were placed in an oven at 100 °C to dry, thus obtaining carbon nanotube-coated modified manganese oxide.

[0135] Comparative Example 1

[0136] Except for replacing the carbon nanotube-coated manganese oxide with manganese dioxide, the rest is the same as in Example 1.

[0137] Comparative Example 2

[0138] Except for omitting the conductive layer (i.e., step 1), and replacing the current collector containing the conductive layer with a stainless steel foil current collector, the rest is the same as in Example 1.

[0139] Comparative Example 3

[0140] Except for replacing the carbon nanotube-coated modified manganese oxide with manganese dioxide, and not setting a conductive layer, using a stainless steel foil current collector instead of a current collector containing a conductive layer, the rest is the same as in Example 1.

[0141] Comparative Example 4

[0142] Except for replacing the carbon nanotubes in the conductive layer with an equal mass of the first conductive agent (based on solid content), the rest is the same as in Example 1.

[0143] Test case

[0144] The positive electrode sheets of the examples and comparative examples were used to make batteries. The preparation steps were as follows: the positive electrode sheets of the above examples and comparative examples were used as positive electrodes, zinc foil was used as negative electrodes, sulfonated hydrophilic PP non-woven fabric was used as separators, and an aqueous solution of 2.5M ZnSO4, 0.2M NmSO4, 0.1M zinc dihydrogen phosphate and 1% PEG-2000 was used as electrolytes. The batteries were assembled into aqueous zinc-manganese batteries.

[0145] The assembled batteries were tested for the following performance characteristics, and the results are shown in Table 1:

[0146] Cyclic performance: Cyclic testing was conducted using the Xinwei Battery Testing System. The battery was charged to 1.8V at a constant current of 0.1C and then discharged to 1.0V. The discharge specific capacity Q1 of the battery in the first cycle was recorded. This was then repeated 100 times, and the discharge specific capacity Q2 after 100 cycles was recorded. The capacity retention rate after 100 cycles was calculated by Q2 / Q1×100%, and the discharge specific capacity retention rate was calculated.

[0147] Table 1 Summary of Performance of Examples and Comparative Examples

[0148]

[0149] As can be seen from Table 1, the battery made from the positive electrode sheet of this application has a higher first-cycle discharge specific capacity and better cycle performance.

[0150] Meanwhile, comparing Example 1 and Comparative Examples 1-3, it can be seen that the conductive layer and the carbon nanotube-coated modified manganese oxide have a synergistic effect, and the combination of the two is beneficial to improving the cycle performance of the battery.

[0151] Comparing Example 1 and Comparative Example 4, it can be seen that the use of carbon nanotubes in the conductive layer is extremely important for improving the loading of carbon nanotube-coated manganese oxide, thereby improving the cycle performance of the battery. It is evident that the carbon nanotube-coated manganese oxide has good compatibility with the first carbon nanotube in the conductive layer.

[0152] 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.

[0153] The embodiments described above are merely illustrative of several implementation methods of this application, 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 this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A positive electrode sheet, characterized in that, The positive electrode includes a current collector and a conductive layer and a positive active layer sequentially disposed on at least one side of the current collector; the conductive layer is disposed between the current collector and the positive active layer; The conductive layer comprises a first carbon nanotube, a first conductive agent, and a first adhesive; The positive electrode active layer comprises carbon nanotube-coated modified manganese oxide, a second conductive agent, and a second binder. The carbon nanotube-coated modified manganese oxide comprises a second carbon nanotube and a manganese oxide; the second carbon nanotube is at least partially coated on the surface of the manganese oxide.

2. The positive electrode sheet as described in claim 1, characterized in that, It meets one or more of the following characteristics: (1) The first conductive agent includes at least one of Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite and graphene; (2) The first adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, CMC, PVA and cellulose adhesives; (3) The mass ratio of the first carbon nanotube to the first conductive agent is (0.5-15):3; (4) The mass ratio of the first carbon nanotube to the first adhesive is (2-8):(1-5).

3. The positive electrode sheet as described in claim 1 or 2, characterized in that, It meets one or more of the following characteristics: (1) The manganese oxide includes at least one of manganese dioxide, manganese trioxide and manganese tetroxide; (2) The mass ratio of the manganese oxide to the second carbon nanotube is 10:(0.02-1.5).

4. The positive electrode sheet as described in claim 1 or 2, characterized in that, It meets one or more of the following characteristics: (1) The second conductive agent includes at least one of Super-Li, activated carbon, acetylene black, Ketjen black, graphite, artificial graphite and graphene; (2) The second adhesive comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, CMC, PVA and cellulose adhesives; (3) The mass ratio of the carbon nanotube-coated modified manganese oxide to the second conductive agent is (6-9):(0.5-4); (4) The mass ratio of the carbon nanotube-coated modified manganese oxide to the second adhesive is (6-9):(0.5-3).

5. The positive electrode sheet as described in claim 1 or 2, characterized in that, The thickness of the conductive layer is 2μm~8μm; And / or the thickness of the positive electrode active layer is 40μm~200μm.

6. A method for preparing a positive electrode sheet, characterized in that, Includes the following steps: A conductive layer slurry containing a first carbon nanotube, a first conductive agent, a first binder, and a first solvent is coated onto at least one side surface of the current collector to form a current collector containing a conductive layer. The carbon nanotube-coated manganese oxide was prepared by mixing and reacting the second carbon nanotube and manganese oxide in the presence of a third solvent and then drying. The positive electrode sheet is prepared by coating a positive electrode slurry containing carbon nanotube-coated modified manganese oxide, a second conductive agent, a second binder, and a second solvent onto a conductive layer of a current collector containing a conductive layer.

7. The preparation method according to claim 6, characterized in that, It meets one or more of the following characteristics: (1) The solid content of the conductive layer slurry is 4wt%~10wt%; (2) The solid content of the positive electrode slurry is 20wt%~45wt%; (3) Based on a content of 100 wt% for the second carbon nanotube, manganese oxide, and the third solvent, the content of the third solvent is 20 wt% to 80 wt%; (4) The first solvent includes at least one of N-methylpyrrolidone, water, and ethanol; (5) The second solvent includes at least one of N-methylpyrrolidone, water, and ethanol; (6) The third solvent includes at least one of N-methylpyrrolidone, water, and ethanol; (7) The conditions for the mixed reaction include: temperature 40℃~60℃; reaction time 12h~36h; stirring speed 200rpm~500rpm; (8) Drying conditions include: drying temperature of 90℃~110℃.

8. The positive electrode sheet prepared by the preparation method according to claim 6 or 7.

9. A battery, characterized in that, The positive electrode sheet includes any one of claims 1-5 and 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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