Preparation method of pole piece, pole piece, battery and electric device

Abstract

The invention discloses a preparation method of a pole piece, the pole piece, a battery and an electric device. The preparation method of the pole piece provided by the invention comprises the following steps: carrying out fibration treatment on a binder and microcrystalline cellulose to form a fibration product; mixing the fibrosis product with a conductive agent and an active substance to obtain a mixture; wherein the conductive agent comprises Super P-Li and activated carbon in a mass ratio of (2-6): (1-5); carrying out rolling film forming treatment on the mixture to form an active material film; and compounding the active material film onto the current collector to form the pole piece. According to the preparation method of the pole piece, the pole piece with high capacity and good cycle performance is prepared by adopting a dry process, and the method does not need to use a solvent and is more environment-friendly and economical.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular to a method for preparing a pole piece, a pole piece, a battery, and an electrical device. Background Art

[0002] The battery pole piece is the core component of the battery, including a positive pole piece and a negative pole piece. The positive and negative pole pieces play a key role in the battery. They provide a place for the electrochemical reaction to occur and are loaded with a large amount of active substances. The content of the active substances directly determines the capacity of the battery. In addition, the stability of the pole piece during the charge and discharge process is crucial for the service life of the battery.

[0003] In the traditional method for preparing a pole piece, mainly raw materials such as positive active substances, conductive agents, and binders are mixed with a solvent to form a slurry, and then the slurry is coated on a current collector, followed by steps such as coating, drying, rolling, and slitting. However, in the above wet preparation process, during the drying and subsequent processing, due to the weak binding force between the binder and the active substances, the active substance particles on the surface of the pole piece may fall off, resulting in powder loss. The powder loss will cause the loss of active substances in the pole piece, reducing the capacity of the battery. Also, due to the different migration rates of each component during the evaporation of the solvent, the active substances, conductive agents, and binders may show a delamination phenomenon inside the pole piece, reducing the structural stability and conductivity of the pole piece and affecting the cycle life of the battery. Summary of the Invention

[0004] Based on this, the present application provides a method for preparing a pole piece, a pole piece, a battery, and an electrical device. The method for preparing the pole piece provided by the present application uses a dry process to prepare the pole piece, and the formed pole piece has the advantages of high active substance loading, high structural stability, and good cycle performance.

[0005] In the first aspect, the present application provides a method for preparing a pole piece, which includes the following steps:

[0006] Perform fibrillation treatment on a binder and microcrystalline cellulose to form a fibrillation product;

[0007] Mix the fibrillation product with a conductive agent and an active substance to obtain a mixture; wherein, the conductive agent includes Super P-Li and activated carbon with a mass ratio of (2~6):(1~5).

[0008] Perform roll forming treatment on the mixture to form an active material film;

[0009] Compound the active material film onto a current collector to form a pole piece.

[0010] In some embodiments of the present application, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and sodium carboxymethyl cellulose. Optionally, the binder includes polytetrafluoroethylene;

[0011] And / or, the active material includes one or more of manganese dioxide, manganese sesquioxide, and manganese tetroxide;

[0012] And / or, the conductive agent further includes one or more of carbon nanotubes, acetylene black, Ketjen black, and graphite.

[0013] In some embodiments of the present application, the mass ratio of the binder to the microcrystalline cellulose is (18~50):1;

[0014] And / or, the mass ratio of the active material to the conductive agent is (5~9):(5~1);

[0015] And / or, the mass ratio of the active material to the binder is (5~9):(0.5~2).

[0016] In some embodiments of the present application, the fibrillation treatment includes: after mixing the binder and the microcrystalline cellulose, stirring at 4000~10000 rpm for 1~2 min.

[0017] In some embodiments of the present application, the pressure of the roll-to-film treatment is 1T~4T, and the temperature is 80°C~120°C;

[0018] And / or, the pressure of the lamination is 1T~4T, and the temperature is 80°C~120°C.

[0019] In some embodiments of the present application, the thickness of the active material film is 100μm~1000μm.

[0020] In some embodiments of the present application, the current collector includes one or more of carbon cloth, carbon paper, stainless steel mesh, stainless steel foil, titanium mesh, titanium foil, nickel foam, aluminum foil, and copper foil.

[0021] In a second aspect, the present application provides an electrode sheet prepared by using the preparation method described in the first aspect of the present application.

[0022] In a third aspect, the present application provides a battery including the electrode sheet described in the second aspect of the present application.

[0023] In a fourth aspect, the present application provides an electrical device including the battery described in the third aspect of the present application.

[0024] The electrode preparation method provided by this application uses a dry process to prepare the electrode. Among them, the fibrillation treatment of the binder and microcrystalline cellulose in this method is beneficial to the bonding and forming of each component. At the same time, using a mixture of SuperP-Li and activated carbon with a suitable mass ratio as the conductive agent can not only form a good conductive network between the active material particles, but also help each component to form a film. After the film is formed, the active material particles can be firmly bonded together to form an electrode structure with a certain strength and shape, preventing the particle shedding or pulverization caused by factors such as the volume change and mechanical stress of the active material during the charge and discharge process of the battery, avoiding the loss of the active material of the electrode, and enabling the battery to maintain a high capacity and cycle stability. In addition, the addition of microcrystalline cellulose can endow the electrode with good liquid absorption and retention capabilities, making the electrode have high cycle performance. The electrode preparation method of this application can prepare an electrode with a high active material loading and high cycle structure stability without the addition of a solvent. The battery including this electrode has the advantages of high capacity and good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of this application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 It is a schematic flowchart of the electrode preparation method provided by the embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to the relevant drawings. The preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of this application more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0029] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, 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 particular parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when stating that a certain parameter is an integer selected from "2 - 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0030] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0031] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0032] If there is no special instruction, the "including", "containing", and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For the open-ended case, for example, the "including", "containing", and "comprising" can mean that other members, elements, or method steps not listed can also be included or contained, or can also only include or contain the listed members, elements, or method steps.

[0033] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". Further, any of the following conditions satisfies 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).

[0034] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0035] In this application, when it comes to "multiple", "multiple types", etc., unless otherwise specifically defined, it means greater than 2 or equal to 2 in quantity. For example, "one or more types" means one type or two or more types.

[0036] In this application, in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumerative description and should be understood not to constitute a closed limitation on quantity.

[0037] In this application, for the unit of the data range, if there is only a unit after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same.

[0038] There are problems in the preparation of positive and negative electrode sheets by the wet process, such as low loading of active substances, limited effective amount of active substances dissolved in the electrolyte during the charge and discharge test, and serious attenuation of cycle performance and rate performance.

[0039] Based on this, in the first aspect, this application provides a method for preparing an electrode sheet by a dry process. This method does not require the addition of a solvent. By selecting Super P-Li and activated carbon with a specific mass ratio as conductive agents, the mixing and film formation of each component in the dry process are promoted, and the binder and microcrystalline cellulose are fibrillated to enhance the adhesion and mixing uniformity between each component, so that the formed active layer has good flexibility, is not prone to cracking or brittle cracking, and has good adhesion to the current collector, thereby enabling the electrode sheet to maintain a high loading of active substances and the stability of the cycle structure. Moreover, the addition of microcrystalline cellulose can make the electrode sheet have good liquid absorption and liquid retention characteristics, thus having good charge and discharge efficiency.

[0040] Specifically, please refer to Figure 1 , the method for preparing the electrode sheet provided in the embodiment of this application includes the following steps:

[0041] S101: Fibrize the binder and microcrystalline cellulose to form a fibrillated product;

[0042] S102: Mix the fibrillated product with a conductive agent and an active material to obtain a mixture; wherein, the conductive agent includes Super P-Li and activated carbon with a mass ratio of (2-6):(1-5);

[0043] S103: Perform roll compaction and film formation on the mixture to form an active material film;

[0044] S104: Composite the active material film onto a current collector to form an electrode sheet.

[0045] This application does not particularly limit the type of the electrode sheet, which can be a positive electrode sheet or a negative electrode sheet, and can be an electrode sheet for a lithium-ion battery, or an electrode sheet for a sodium-ion battery, a potassium-ion battery, or an aqueous zinc-manganese battery.

[0046] In step S101, "fibrization treatment" means making the binder and microcrystalline cellulose form a fibrous structure to achieve the bonding and molding of each component. This application does not particularly limit the process of fibrization treatment, which can adopt the conventional fibrization treatment process in the art. For example, put each component into a high-speed mixing device, and use the powerful shear force generated by the high-speed rotating equipment components to fibrize each component, or drive the powder material by high-speed airflow to fibrize each component under the action of the high shear force of the airflow.

[0047] The fibrization treatment process of microcrystalline cellulose and the binder can be carried out separately or together, and mixing is conducive to simplifying the process.

[0048] In some embodiments of this application, the fibrization treatment includes: after mixing the binder and microcrystalline cellulose, stir at 4000-10000 rpm for 1-2 min. Exemplarily, the stirring speed can be 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm or the range composed of any two of the foregoing values.

[0049] In some embodiments of this application, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and sodium carboxymethyl cellulose. After the above binder undergoes fibrization treatment, it can form a firm bond with other components, and itself has good elasticity and flexibility, can adapt to the shape change during the fibrization process, and can avoid the adverse effects on the bonding effect caused by material deformation and embrittlement.

[0050] Preferably, the binder includes polytetrafluoroethylene. Compared with other binders, polytetrafluoroethylene not only has good binding properties, but also its low friction coefficient and self-lubricating properties reduce the frictional resistance between components during the dry film-forming process, facilitating the mixing, coating, and forming operations of each component, and is conducive to improving the film-forming quality.

[0051] Microcrystalline cellulose has certain water absorption and water retention properties. In the electrode, it can absorb and retain a part of the electrolyte, helping to improve the full contact in the electrolyte electrode, providing a good medium for ion transport, and thus improving the charge-discharge efficiency and cycle performance of the battery.

[0052] In some embodiments of the present application, the mass ratio of the binder to microcrystalline cellulose is (18~50):1. Exemplarily, the mass ratio of the binder to microcrystalline cellulose can be 18:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1 or the range composed of any two of the foregoing ratios. The binding effect of the binder is strong, and its relatively high proportion can make the combination between active material particles closer, making the electrode have better flexibility and not easily break under external force. An appropriate amount of microcrystalline cellulose is beneficial to the liquid retention and liquid absorption of the electrode, improving the ion transport efficiency. However, it has certain rigidity and strength itself. If its proportion is too high, the flexibility of the electrode will decrease, and cracks and fractures are likely to occur in the electrode during the charge-discharge process of the battery, affecting the stability of the electrode. Within the above mass ratio range, it is beneficial for the electrode to have both excellent stability and liquid absorption and retention properties.

[0053] In step S102, the mixing process of the fibrated product with the conductive agent and the active material can be carried out simultaneously with the fibrillation treatment process of microcrystalline cellulose and the binder in step S101, that is, microcrystalline cellulose, the binder, the conductive agent, and the active material are simultaneously mixed at a high speed, and the fibrillation of the binder and microcrystalline cellulose is achieved while mixing; it can also be carried out separately, that is, after obtaining the fibrated product of the binder and microcrystalline cellulose, the fibrated product is then mixed with the conductive agent and the active material.

[0054] Among them, the binder and microcrystalline cellulose are usually polymers, and the active material and the conductive agent are usually inorganic substances. The different dispersion properties of polymers and inorganic substances will affect the fibrillation effect of the binder and microcrystalline cellulose during the simultaneous mixing process, and further affect the adhesion of the electrode. Therefore, it is preferably to complete the mixing process of these components by first fibrating the binder and microcrystalline cellulose and then mixing the fibrated product with the conductive agent and the active material.

[0055] In some embodiments of the present application, the mixing of the fibrous product with the conductive agent and the active material can be completed by stirring at 1000 - 5000 rpm for 1 - 2 minutes. Exemplarily, the stirring speed can be 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, or a range composed of any two of the foregoing values.

[0056] The present application does not particularly limit the type of the active material, and the corresponding active material can be selected according to different types of batteries required. For example, when preparing the positive electrode sheet for a lithium-ion battery, the active material can be selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, nickel cobalt manganese ternary material, and lithium nickel cobalt aluminate; when preparing the negative electrode sheet for a lithium-ion battery, the active material can be selected from one or more of graphite, hard carbon, silicon-based material, and tin-based material; when preparing the positive electrode sheet for a sodium-ion battery, the active material can be selected from sodium layered oxides (such as NaCoO 2 , NaMnO 2 ), polyanion-type compounds (such as Na 3 V 2 (PO 4 ) 3 , NaFeSO 4 F), Prussian blue and its analogs; when preparing the negative electrode sheet for a sodium-ion battery, the active material can be selected from carbon-based materials (such as graphite, soft carbon, hard carbon, graphene), titanium-based materials (such as TiO 2 , Na 2 Ti 3 O 7 ), organic polymers (such as polyimide), and organic small molecules (such as hydroquinone); when preparing the positive electrode sheet for a zinc-manganese battery, the active material can be one or more of manganese dioxide, manganese sesquioxide, and manganese tetroxide.

[0057] It has been experimentally verified that the preparation method provided by the present application is more suitable for the preparation of the positive electrode sheet of a zinc-manganese battery. The specific conductive agent system required by this method plays the role of conducting electricity and promoting dry film formation, and the application of this conductive agent system to the positive electrode sheet of a zinc-manganese battery can enable the zinc-manganese battery to have better electrochemical performance.

[0058] The conductive agent of the present application comprises Super-Li and activated carbon with a mass ratio of (2 to 6):(1 to 5). Super-Li and activated carbon themselves can be dispersed between the particles of the active material as conductive agents to form a good conductive network, reduce the resistance of the electrode sheet, enable electrons to be transmitted quickly and efficiently between the active material particles, and improve the charge and discharge efficiency of the battery. And through experimental verification, it is found that after the two are mixed in the above specific mass ratio range, the components of the active material, binder and microcrystalline cellulose can form a good film without solvent mixing. After film formation, the active material particles can be firmly bonded together to form an electrode structure with a certain strength and shape, preventing the particles from falling off or pulverizing due to factors such as volume change and mechanical stress of the active material during the charge and discharge process of the battery, avoiding the loss of the active material of the electrode sheet, and enabling the battery to maintain a high capacity and cycle stability.

[0059] In addition to the Super-Li and activated carbon with the above specific mass ratio, the conductive agent of the present application may also include some conductive agents commonly used in the battery field. As a non-limiting example, the conductive agent may also include one or more of carbon nanotubes, acetylene black, Ketjen black, and graphite.

[0060] In some embodiments of the present application, the mass ratio of the active material to the conductive agent is (5 to 9):(5 to 1). Controlling the mass ratio of the active material and the conductive agent within the above range is beneficial to enabling the electrode sheet to have both a high capacity, conductive performance, and film-forming characteristics.

[0061] In some embodiments of the present application, the mass ratio of the active material to the binder is (5 to 9):(0.5 to 2). Controlling the mass ratio of the active material and the binder within the above range is beneficial to enabling it to have both a high capacity, bonding strength, and structural stability.

[0062] In step S103, by roll-pressing to form a film, the active material particles can be squeezed more tightly, improving the compaction density of the electrode sheet, and optimizing and adjusting the pores inside the electrode sheet to make the pore size and distribution more uniform and reasonable, providing a good channel for the penetration of the electrolyte and ion transport.

[0063] In some embodiments of the present application, the pressure for roll forming the film is 1T to 4T, and the temperature is 80°C to 120°C. Exemplarily, the pressure can be 1T, 2T, 3T, 4T, or a range composed of any two of the above values, and the temperature can be 80°C, 90°C, 100°C, 110°C, 120°C, or a range composed of any two of the foregoing values. Within the above pressure range, the internal structure of the material is more uniform, enabling the film to have good flexibility while having a certain strength. Increasing the temperature during roll pressing can intensify the molecular thermal motion of polymers such as binders and microcrystalline cellulose, reduce their viscosity, make them more likely to flow and deform between the rollers, and is conducive to forming an active material film with a smooth surface and uniform distribution of each component.

[0064] In some embodiments of the present application, the thickness of the active material film is 100 to 1000 μm. Exemplarily, the thickness of the active material film can be 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, or a range composed of any two of the foregoing values. Controlling the thickness of the formed active material film within the above range can not only enable the electrode sheet to have a high energy density, but also reduce the resistance inside the electrode sheet while ensuring a sufficient electrochemical reaction area, enabling ions to be transmitted more efficiently and making the battery have a high charge-discharge efficiency.

[0065] In step S104, the active material film can be laminated to the current collector by hot pressing.

[0066] In some embodiments of the present application, the current collector includes one or more of carbon cloth, carbon paper, stainless steel mesh, stainless steel foil, titanium mesh, titanium foil, nickel foam, aluminum foil, and copper foil. The above current collectors can all form good lamination with the active material film and are not easily peeled off or delaminated.

[0067] In some embodiments of the present application, the pressure for laminating the active material film to the current collector is 1T to 4T, and the temperature is 80°C to 120°C. Exemplarily, the lamination pressure of the active material film and the current collector is 1T, 2T, 3T, 4T, or a range composed of any two of the foregoing, and the lamination temperature is 80°C, 90°C, 100°C, 110°C, 120°C, or a range composed of any two of the foregoing values. If the lamination temperature and pressure are too low, the active material film and the current collector cannot be closely attached, resulting in a reduced bonding force between the two and poor lamination effect. Excessively high lamination temperature may cause thermal degradation and accelerated aging of the active material film, leading to a decrease in the mechanical properties and chemical stability of the electrode sheet, while excessively high pressure may cause mechanical damage to the active material film, thereby affecting the performance of the electrode sheet.

[0068] After the composite of the active material film and the current collector is completed, in order to avoid side reactions inside the electrode due to moisture after the electrode is exposed to moisture, the composite electrode can be dried. In a specific embodiment, the composite electrode can be placed in a forced-air oven and dried at 100 °C to 150 °C for 2 to 8 hours to complete the drying process.

[0069] In a second aspect, the present application provides an electrode prepared by the preparation method described above. The electrode has advantages such as a high active material loading and good cyclic structural stability.

[0070] In a third aspect, the present application provides a battery, which includes the electrode described above. The battery has the advantages of a high battery capacity and good cyclic performance.

[0071] The present application does not particularly limit the type of the battery, and it can be one or more of a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, or a zinc-manganese battery, preferably a zinc-manganese battery.

[0072] In some of these embodiments, the battery includes positive and negative electrodes, a separator membrane spaced between the positive and negative electrodes, and an electrolyte.

[0073] Among them, the positive and negative electrodes can be the electrodes described above.

[0074] The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0075] In some of these embodiments, the material of the separator membrane can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0076] The electrolyte functions to conduct ions between the positive and negative electrodes. The present application does not particularly limit the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0077] In some of these embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0078] In some of these embodiments, when the battery is a lithium-ion battery, the electrolyte salt can include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0079] In some embodiments, when the battery is a lithium-ion battery, the solvent may include one or more of 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.

[0080] In some embodiments, when the battery is a zinc-manganese battery, the electrolyte may be one or more of ammonium chloride, zinc chloride, potassium hydroxide, sodium hydroxide, and zinc sulfate, and the solvent may be water.

[0081] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly by a winding process or a stacking process.

[0082] In some embodiments, the battery may include an outer package. The outer package may be used to encapsulate the above electrode assembly and electrolyte.

[0083] In some embodiments, the outer package of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic. Further, non-limiting examples of the plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0084] Fourthly, the present application also provides an electrical device. The electrical device includes the battery provided by the present application. The battery may be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, 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.

[0085] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0086] Hereinafter, embodiments of the present application will be described. The following described embodiments are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specified techniques or conditions in the embodiments, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For the reagents or instruments without specified manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0087] Example 1

[0088] This example provides a positive electrode sheet, and its preparation method includes the following steps:

[0089] 1) Weigh polytetrafluoroethylene and microcrystalline cellulose with a mass ratio of 49:1, and mix and stir the two at 7500 rpm for 2 min to obtain a fibrillated product;

[0090] 2) Mix the fibrillated product, manganese dioxide, and conductive agent in a mass ratio of 1:7:2, and mix and stir at 3000 rpm for 2 min to obtain a mixture; among them, the conductive agent includes Super P-Li and activated carbon with a mass ratio of 3:2;

[0091] 3) Put the mixture into a roll press, and roll it at a pressure of 2T and a temperature of 100 °C to obtain an active material film with a thickness of 400 μm;

[0092] 4) Thermocompression bond the active material film with a current collector stainless steel mesh at a pressure of 2T and a temperature of 100 °C. After the bonding is completed, put it into a blast drying oven and dry it at 120 °C for 6 h to obtain the positive electrode sheet.

[0093] Example 2

[0094] This example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: in step 2), the conductive agent includes Super P-Li and activated carbon with a mass ratio of 1:1.

[0095] Example 3

[0096] This example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: in step 2), the conductive agent includes Super P-Li and activated carbon with a mass ratio of 7:3.

[0097] Example 4

[0098] This example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: polytetrafluoroethylene is replaced by polyvinylidene fluoride.

[0099] Example 5

[0100] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: polytetrafluoroethylene is replaced by sodium carboxymethylcellulose.

[0101] Embodiment 6

[0102] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: the mass ratio of polytetrafluoroethylene to microcrystalline cellulose is replaced by 52:1.

[0103] Embodiment 7

[0104] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: the mass of polytetrafluoroethylene and microcrystalline cellulose is replaced by 25:1.

[0105] Embodiment 8

[0106] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: the mass ratio of polytetrafluoroethylene to microcrystalline cellulose is replaced by 16:1.

[0107] Embodiment 9

[0108] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: the mass ratio of manganese dioxide, conductive agent and fibrous product is replaced by 17:2:1.

[0109] Embodiment 10

[0110] This embodiment provides a positive electrode sheet, and its preparation method is basically the same as that of Embodiment 1, except that: the mass ratio of manganese dioxide, conductive agent and fibrous product is replaced by 20:1:1.

[0111] Embodiment 11

[0112] This embodiment provides a positive electrode sheet, and its preparation method includes the following steps:

[0113] 1) Weigh manganese dioxide, conductive agent, polytetrafluoroethylene and microcrystalline cellulose with a mass ratio of 350:100:49:1, and mix and stir at 7500 rpm for 2 min to obtain a mixed product;

[0114] 2) Put the mixed product into a roll press, roll press at 2T pressure and 100 °C to obtain an active material film with a thickness of 400 μm;

[0115] 3) Thermocompression bond the active material film with the current collector stainless steel mesh at 2T pressure and 100 °C. After the thermocompression bonding is completed, put it into a blast drying oven and dry it overnight at 120 °C to obtain the positive electrode sheet.

[0116] Comparative Example 1

[0117] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: the conductive agent is replaced with a single Super P-Li.

[0118] Comparative Example 2

[0119] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: the conductive agent is replaced with a single activated carbon.

[0120] Comparative Example 3

[0121] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: the conductive agent is replaced with Super P-Li and activated carbon with a mass ratio of 1:1.

[0122] Comparative Example 4

[0123] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: the conductive agent is replaced with Super P-Li and activated carbon with a mass ratio of 7:1.

[0124] Comparative Example 5

[0125] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: the microcrystalline cellulose is replaced with carboxymethyl cellulose.

[0126] Comparative Example 6

[0127] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that: Super P-Li is replaced with Super P-C.

[0128] Comparative Example 7

[0129] This comparative example provides a positive electrode sheet, and its preparation method is basically the same as that of Example 1, except that the activated carbon is replaced with carbon nanotubes.

[0130] Test Example

[0131] The electrode sheets of the above examples and comparative examples were made into batteries, and the preparation steps were as follows: using the positive electrode sheets of the above examples and comparative examples as the positive electrode, zinc foil as the negative electrode, and a glass fiber separator as the separator, 2M ZnSO 4 and 0.1M MnSO 4 and an aqueous solution of 0.1M [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide as the electrolyte to assemble an aqueous zinc-manganese battery.

[0132] The batteries made from the electrodes of the above examples and comparative examples were tested for the following performances:

[0133] At 25 °C, the fully charged battery was charged at a constant current of 0.1 A / g to 1.8 V and then discharged to 1.0 V, and the initial discharge specific capacity Q1 of the battery was recorded; then, taking this as one cycle, the cycle was 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%.

[0134] Table 1

[0135]

[0136] The following conclusions can be analyzed from Table 1:

[0137] 1) By comparing Examples 1-3 with Comparative Examples 1-4, 6-7, it can be seen that when the conductive agent is a mixture of Super P-Li and activated carbon with a mass ratio of (2-6):(1-5), the battery can obtain excellent initial discharge specific capacity and cycling performance. However, when using Super P-Li or activated carbon alone as the conductive agent, or replacing Super P-Li with Super P-C, or replacing activated carbon with other carbon materials such as carbon nanotubes, or when the mass ratio of Super P-Li and activated carbon is not within the above range, it is difficult to promote the dry film formation of the components in the active material layer, thereby reducing the active substance loading amount and cycling reliability in the electrode, and further significantly reducing the initial discharge specific capacity and 100-cycle capacity retention rate of the battery.

[0138] 2) By comparing Examples 1, 4, and 5, it can be known that the dry film formation effect of using polytetrafluoroethylene as the binder is the most excellent, and all aspects of the battery performance are more excellent.

[0139] 3) By comparing Examples 1, 9, and 10, it can be known that when the mass ratio of manganese dioxide, conductive agent, and fibrous product in the active material layer is 7:2:1, the initial discharge specific capacity of the battery and the capacity retention rate after 100 cycles are more excellent. However, as the proportion of manganese dioxide in the active material layer increases, the initial discharge specific capacity of the battery and the 100-cycle capacity retention rate decrease. The reason may be that as the proportion of fibrous product and binder conductive agent decreases, the active material film formed by dry method is difficult to load more active materials, and the stability of the formed active material film will also decrease, resulting in a decrease in discharge capacity and cycling performance.

[0140] 4) By comparing Examples 1, 6, 7, and 8, it can be seen that the mass ratio of polytetrafluoroethylene to microcrystalline cellulose also affects the discharge capacity and cycling performance of the battery. Among them, when the mass ratio of polytetrafluoroethylene to microcrystalline cellulose is in the range of (18~50):1, the performance of the battery is more excellent.

[0141] 5) By comparing Example 1 and Example 11, it can be seen that when components such as manganese dioxide, conductive agent, polytetrafluoroethylene, and microcrystalline cellulose are mixed for fibrillation, the effect is worse than that of fibrillating polytetrafluoroethylene and microcrystalline cellulose alone, and both the discharge capacity and cycling performance of the battery will decline.

[0142] 6) By comparing Example 1 and Comparative Example 5, it can be seen that after replacing microcrystalline cellulose with carboxymethyl cellulose, both the discharge specific capacity and the retention rate of the cycling capacity of the battery decrease. The reason is that compared with carboxymethyl cellulose, microcrystalline cellulose has better liquid retention performance, which can make the cycling performance and discharge performance of the battery more excellent.

[0143] The descriptions of the above embodiments tend to emphasize the differences between the embodiments. Their similarities or similarities can be referred to each other. For the sake of brevity, they will not be elaborated herein.

[0144] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same function and effect as the technical idea within the technical scope of this application are included in the technical scope of this application. In addition, within the scope of not departing from the main idea of this application, various modifications that those skilled in the art can think of to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A method for preparing a pole piece, characterized in that: The following steps are involved: fibrillating the binder and the microcrystalline cellulose to form a fibrillated product; The fiberized product is mixed with a conductive agent and an active material to obtain a mixture; wherein the conductive agent comprises Super P-Li and activated carbon in a mass ratio of (2-6): (1-5); Performing a roll-pressing film-forming process on the mixture to form an active material film; The active material film is compounded onto a current collector to form a pole piece.

2. The preparation method according to claim 1, characterized in that: The binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and sodium carboxymethyl cellulose. Optionally, the binder includes polytetrafluoroethylene; And / or, the active substance includes one or more of manganese dioxide, manganese trioxide, and manganese tetraoxide; And / or, the conductive agent further includes one or more of carbon nanotubes, acetylene black, Ketjen black, and graphite.

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of the binder to the microcrystalline cellulose is (18-50):1; And / or, the mass ratio of the active material to the conductive agent is (5-9): (5-1); And / or, the mass ratio of the active substance to the binder is (5-9):(0.5-2).

4. The preparation method according to claim 1 or 2, characterized in that: The fiberization treatment comprises: mixing the binder and the microcrystalline cellulose, and stirring at 4000-10000 rpm for 1-2 minutes.

5. The preparation method according to claim 1 or 2, characterized in that: The roller-pressing film forming process has a pressure of 1T to 4T and a temperature of 80°C to 120°C; And / or, the compounding pressure is 1T~4T, and the temperature is 80°C~120°C.

6. The preparation method according to claim 1 or 2, characterized in that: The thickness of the active material film is 100 μm to 1000 μm.

7. The preparation method according to claim 1 or 2, characterized in that: The current collector includes one or more of carbon cloth, carbon paper, stainless steel mesh, stainless steel foil, titanium mesh, titanium foil, nickel foam, aluminum foil, and copper foil.

8. A pole piece, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. A battery, characterized in that: Including the pole piece as claimed in claim 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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