Pole piece and preparation method thereof, battery and power utilization device

Abstract

The invention discloses a 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 pole piece comprises a current collector and an active layer arranged on the surface of the current collector; the active layer comprises an active substance and a composite binder; the composite binder comprises a first polyhydroxyalkanoate, a second polyhydroxyalkanoate and a non-biodegradable binder; the average molecular weight of the first polyhydroxyalkanoate is 100,000-600,000; the average molecular weight of the second polyhydroxyalkanoate is 1.5 million to 3 million. The active layer of the pole piece adopts the combination of polyhydroxyalkanoate with different molecular weights and the non-biodegradable binder as the binder, can be suitable for dry process film formation, improves the film-forming property of the active layer, improves the loading capacity of the active substance of the pole piece, and has significantly improved cycle life when being used in a battery.

Description

Technical Field

[0001] The present application relates to the field of new energy storage technology, and in particular to pole pieces and their preparation methods, batteries, and electrical devices. Background Art

[0002] The bond strength between the current collector and the active material is crucial to the battery's cycle life. If the bond strength is insufficient, the active material can easily fall off the current collector during charge and discharge, resulting in a decrease in battery capacity. Good bonding ensures stable electron transfer and reduces battery performance degradation caused by poor contact.

[0003] The positive and negative electrodes of traditional zinc-manganese batteries are mostly produced using a wet process. The active material, conductive agent, binder, and solvent are first mixed to form a slurry, which is then coated onto the current collector to form the active layer. Due to uneven solvent evaporation, membrane structural stability, and the performance of the wet binder, the active material loading is typically low. During the charge and discharge process, the effective amount of active material on the positive and negative current collectors that dissociates into the electrolyte is quite limited, and the effective amount of manganese or zinc ions that migrate into the active material on the current collector is also insufficient, resulting in a significant degradation of the battery's cycling performance. Summary of the Invention

[0004] Based on this, the main purpose of this application is to provide a pole piece, the active layer of which adopts a composite of polyhydroxyalkanoates of different molecular weights and a non-biodegradable binder as a binder, which can be suitable for dry process film formation, improve the film forming properties of the active layer, and increase the loading amount of active materials of the pole piece, so that the battery has a significantly improved cycle life.

[0005] In a first aspect of the present application, a pole piece is provided, comprising a current collector and an active layer disposed on a surface of the current collector;

[0006] The active layer includes active material and composite binder;

[0007] The composite binder includes a first polyhydroxyalkanoate, a second polyhydroxyalkanoate and a non-biodegradable binder;

[0008] The average molecular weight of the first polyhydroxyalkanoate is 100,000-600,000; the average molecular weight of the second polyhydroxyalkanoate is 1.5 million-3 million.

[0009] In some embodiments, in the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate, and the non-biodegradable binder is 1-4:1-4:1.

[0010] In some embodiments, the composite binder further comprises a third polyhydroxyalkanoate; the third polyhydroxyalkanoate has an average molecular weight of 800,000 to 1.2 million.

[0011] In some embodiments, in the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate, the third polyhydroxyalkanoate, and the non-biodegradable binder is 0.5-2:0.5-2:1-4:1.

[0012] In some embodiments, one or more of the following conditions are met:

[0013] (1) The electrode is a positive electrode or a negative electrode;

[0014] (2) The non-biodegradable binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide and cellulose binder;

[0015] (3) The active layer further includes a conductive agent;

[0016] (4) The mass ratio of the active material to the conductive agent is (4-10): (1-6);

[0017] (5) The mass ratio of the active substance to the composite binder is (3-15):1;

[0018] (6) In the active layer, the mass proportion of the active material is 50%-90%;

[0019] (7) The thickness of the active layer is 100 μm-1000 μm.

[0020] In some embodiments, one or more of the following conditions are met:

[0021] (1) The active material of the positive electrode plate includes at least one of manganese dioxide, manganese trioxide and manganese tetraoxide;

[0022] (2) The active material of the negative electrode plate includes zinc metal or manganese metal;

[0023] (3) The cellulose binder includes at least one of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, microcrystalline cellulose and hydroxyethyl cellulose;

[0024] (4) The conductive agent includes at least one of Super-Li, activated carbon, carbon nanotubes, acetylene black, Ketjen black and graphite.

[0025] The second aspect of the present application provides a method for preparing a pole piece, comprising the following steps:

[0026] mixing the active material and the conductive agent to form a first mixture;

[0027] The first mixture and a composite binder are mixed and subjected to a fiberization treatment to form a second mixture; the composite binder comprises a first polyhydroxyalkanoate, a second polyhydroxyalkanoate, and a non-biodegradable binder; the first polyhydroxyalkanoate has an average molecular weight of 100,000 to 600,000; the second polyhydroxyalkanoate has an average molecular weight of 1.5 million to 3 million;

[0028] forming the second mixture into a film to form an active layer;

[0029] The active layer is compounded with the current collector to form the pole piece.

[0030] In some embodiments, film forming includes at least one of roll film forming, extrusion film forming, dry spray film forming and hot pressing film forming; optionally, the conditions of roll film forming include: pressure 1T-4T; temperature 80℃-120℃.

[0031] The third aspect of the present application provides a battery, comprising the electrode sheet described in the first aspect or the electrode sheet prepared by the preparation method described in the second aspect.

[0032] The fourth aspect of the present application provides an electrical device, comprising the electrode described in the first aspect or the electrode prepared by the preparation method described in the second aspect, or the battery described in the third aspect.

[0033] Beneficial effects of this application:

[0034] 1. The active layer of the electrode of the present application adopts a composite of polyhydroxyalkanoates of different molecular weights and a non-biodegradable binder as a binder, which can be applied to dry process film formation, improve the film forming properties of the active layer, and increase the loading amount of active materials of the electrode, and have a significantly improved cycle life when used in batteries.

[0035] 2. This application adopts a dry process, which does not require the use of solvents or solvent recovery. Compared with the wet process, it is more environmentally friendly, clean and economical. DETAILED DESCRIPTION

[0036] To make the purpose, 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 described clearly and completely below in conjunction with specific embodiments of this application. The described embodiments are only a portion of the embodiments of this application, not all of them.

[0037] The following is a detailed description of the implementation of this application. This embodiment is implemented based on the technical solution of this application, and provides a detailed implementation method and specific operation process, but the protection scope of this application is not limited to the following embodiment.

[0038] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0039] the term

[0040] Unless otherwise specified or incompatible therewith, terms and phrases used in this application shall have the following meanings:

[0041] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "at least one" or "at least one" means one or more than or equal to two.

[0042] In this application, "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0043] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0044] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is deemed to be continuous and includes the two numerical endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the 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 a feature or characteristic, these numerical ranges can be combined. 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. "Numerical interval" is broadly allowed to include numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0045] In this application, unless otherwise specified, temperature parameters may be either constant temperature or fluctuating within a certain temperature range. It should be understood that constant temperature processing allows for temperature fluctuations within the precision range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0046] Unless otherwise specified, the percentage contents mentioned in this application refer to mass percentage for solid-liquid mixture and solid-solid mixture, and refer to volume percentage for liquid-liquid mixture.

[0047] In this application, temperature parameters, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range of instrument control. The room temperature referred to in this application refers to 0-40°C, preferably 10-35°C, and more preferably 20-30°C.

[0048] The bond strength between the current collector and the active material is crucial to the battery's cycle life. If the bond strength is insufficient, the active material can easily fall off the current collector during charge and discharge, resulting in a decrease in battery capacity. Good bonding ensures stable electron transfer and reduces battery performance degradation caused by poor contact.

[0049] The positive and negative electrodes of traditional zinc-manganese batteries are mostly produced using a wet process. The active material, conductive agent, binder, and solvent are first mixed to form a slurry, which is then coated onto the current collector to form the active layer. Due to uneven solvent evaporation, membrane structure stability, and the performance of the wet binder, the active material loading is typically low. During the charge and discharge process, the effective amount of active material from the positive and negative current collectors that dissolves into the electrolyte is quite limited, and the effective amount of manganese or zinc ions that migrate to the current collector is also insufficient, resulting in a significant degradation of the battery's cycling performance.

[0050] Based on this, the first aspect of the present application provides a pole piece, comprising a current collector and an active layer disposed on a surface of the current collector;

[0051] The active layer includes active material and composite binder;

[0052] The composite binder includes a first polyhydroxyalkanoate, a second polyhydroxyalkanoate and a non-biodegradable binder;

[0053] The average molecular weight of the first polyhydroxyalkanoate is 100,000-600,000; the average molecular weight of the second polyhydroxyalkanoate is 1.5 million-3 million.

[0054] The active layer of the electrode of the present application adopts a composite of polyhydroxyalkanoates of different molecular weights and a non-biodegradable binder as a binder, which can be applied to dry process film formation, improve the film-forming properties of the active layer, and increase the loading amount of active substances in the electrode, so that the battery has a significantly improved cycle life and does not require the use of solvents or solvent recovery. Compared with the wet process, it is more environmentally friendly, clean and economical.

[0055] Polyhydroxyalkanoates (PHA), as biodegradable polyesters, are rich in hydroxyl groups and exhibit excellent adhesion to current collectors and active materials. However, PHA have a narrow processing window and still crystallize after processing, resulting in post-crystallization. Therefore, when used alone in dry film formation, they exhibit poor film-forming properties and cannot guarantee film quality. The inventors have discovered that by combining PHA with different molecular weights and adding a non-biodegradable binder such as polytetrafluoroethylene, the regularity of the PHA can be disrupted, post-crystallization can be avoided, and film uniformity and stability can be improved. Consequently, the corresponding batteries have significantly improved cycle life.

[0056] In a specific example, the average molecular weight of the first polyhydroxyalkanoate can be 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, etc.

[0057] In a specific example, the average molecular weight of the second polyhydroxyalkanoate can be 1.5 million, 1.6 million, 1.7 million, 1.8 million, 1.9 million, 2 million, 2.1 million, 2.2 million, 2.3 million, 2.4 million, 2.5 million, 2.6 million, 2.7 million, 2.8 million, 2.9 million, 3 million, etc.

[0058] In a specific example, in the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate and the non-biodegradable binder is 1-4:1-4:1, for example, 1:1:1, 1:2:1, 1:3:1, 1:4:1, 2:1:1, 3:1:1, 4:1:1, 2:2:1, 2:3:1, 3:2:1, 4:4:1, etc.

[0059] In a specific example, the composite binder further includes a third polyhydroxyalkanoate; the third polyhydroxyalkanoate has an average molecular weight of 800,000-1.2 million, such as 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, etc.

[0060] In a specific example, in the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate, the third polyhydroxyalkanoate and the non-biodegradable binder is 0.5-2:0.5-2:1-4:1, for example, 0.5:0.5:2:1, 0.5:1:2:1, 1:0.5:2:1, 1:1:2:1, 2:1:2:1, 1:2:2:1, 2:2:2:1, 1:1:3:1, 1:1:4:1, etc.

[0061] In a specific example, the electrode is a positive electrode or a negative electrode.

[0062] In the present application, the type of active material is not particularly limited, and the corresponding active material can be selected according to the required type of battery and type of electrode. For example, when preparing a positive electrode sheet for a lithium-ion battery, the active material can be selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, nickel cobalt manganese ternary material, and lithium nickel cobalt aluminum oxide; when preparing a negative electrode sheet for a lithium-ion battery, the active material can be selected from at least one of graphite, hard carbon, silicon-based materials, and tin-based materials; when preparing a positive electrode sheet for a sodium-ion battery, the active material can be selected from at least one of sodium ion layered oxides (such as NaCoO2, NaMnO2), polyanionic compounds (such as Na3V2(PO4)3, NaFeSO4F), Prussian blue and its analogues; when preparing a negative electrode sheet for a sodium-ion battery, the active material can be selected from at least one of carbon-based materials (such as graphite, soft carbon, hard carbon, graphene), titanium-based materials (such as TiO2, Na2Ti3O7), organic polymers (such as polyimide), and organic small molecules (such as hydroquinone); when preparing a positive electrode sheet for a zinc-manganese battery, the active material can be at least one of manganese dioxide, manganese trioxide, and manganese tetraoxide.

[0063] In a specific example, the active material of the positive electrode plate includes at least one of manganese dioxide, manganese trioxide and manganese tetraoxide.

[0064] In a specific example, the active material of the negative electrode plate includes zinc metal or manganese metal.

[0065] In one specific example, the non-biodegradable binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, and a cellulose binder; polytetrafluoroethylene and cellulose binders are optional. Using polytetrafluoroethylene and cellulose binders as the non-biodegradable binder further improves the film-forming properties of the active layer, thereby improving the cycle life of the battery. Specifically, the mass ratio of polytetrafluoroethylene to cellulose binder is 5-20:1, for example, 5:1, 8:1, 10:1, 15:1, 18:1, 20:1, etc.

[0066] In a specific example, the cellulose-based binder includes at least one of sodium carboxymethylcellulose, hydroxypropyl methylcellulose, microcrystalline cellulose and hydroxyethyl cellulose.

[0067] In one specific example, the conductive agent includes at least one of Super P-Li, activated carbon, carbon nanotubes, acetylene black, Ketjen black, and graphite; Super P-Li and activated carbon are optional. Specifically, the mass ratio of Super P-Li to activated carbon can be 1-5:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, etc.

[0068] In a specific example, the mass ratio of the active material to the conductive agent is (4-10): (1-6), for example, 4:1, 6:1, 8:1, 10:1, 4:2, 6:2, 8:2, 10:2, 4:3, 6:3, 8:3, 10:3, 4:4, 6:4, 8:4, 10:4, 4:5, 6:5, 8:5, 10:5, 4:6, 6:6, 8:6, 10:6, etc.

[0069] In a specific example, the mass ratio of the active substance to the composite binder is (3-15):1, for example, 3:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, etc.

[0070] In a specific example, in the active layer, the mass proportion of the active material is 50%-90%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%.

[0071] In a specific example, the thickness of the active layer is 100 μm-1000 μm, for example, 100 μm, 200 μm, 400 μm, 600 μm, 800 μm, 1000 μm, etc.

[0072] The second aspect of the present application provides a method for preparing a pole piece, comprising the following steps:

[0073] mixing the active material and the conductive agent to form a first mixture;

[0074] The first mixture and a composite binder are mixed and subjected to a fiberization treatment to form a second mixture; the composite binder comprises a first polyhydroxyalkanoate, a second polyhydroxyalkanoate, and a non-biodegradable binder; the first polyhydroxyalkanoate has an average molecular weight of 100,000 to 600,000; the second polyhydroxyalkanoate has an average molecular weight of 1.5 million to 3 million;

[0075] forming the second mixture into a film to form an active layer;

[0076] The active layer is compounded with the current collector to form the pole piece.

[0077] In a specific example, the film forming includes at least one of roll film forming, extrusion film forming, dry spray film forming, and hot press film forming.

[0078] In a specific example, the conditions for roller pressing and film formation include: pressure 1T-4T; temperature 80℃-120℃; specifically, the pressure can be 1T, 1.5T, 2T, 2.5T, 3T, 3.5T, 4T, etc.; the temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, etc.

[0079] In the present application, "fiberization treatment" refers to forming a fibrous structure of the binder and microcrystalline cellulose to achieve bonding and molding of the components. The present application does not particularly limit the process of the fiberization treatment, and it can adopt the conventional fiberization treatment process in the art, for example, placing the components in a high-speed mixing device, using high-speed rotating equipment parts to generate a strong shear force to fiberize the components, or driving the powder by a high-speed airflow to fiberize the components under the high shear force of the airflow. The first mixture and the composite binder are mixed and fiberized, which can be mixed in steps and distributed for fiberization, or mixed in one step and then fiberized in one step, or mixed in steps and then fiberized in one step.

[0080] In a specific example, the conditions of the fiberization treatment include: stirring at 4000-10000 rpm for 1-20 min. For example, the stirring speed can be 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, etc., and the stirring time can be 1 min, 5 min, 10 min, 15 min, 20 min, etc.

[0081] In a specific example, the current collector includes at least one of carbon cloth, carbon paper, stainless steel mesh, stainless steel foil, titanium mesh, nickel mesh, titanium foil, and nickel foam.

[0082] The third aspect of the present application provides a battery, comprising the electrode sheet described in the first aspect or the electrode sheet prepared by the preparation method described in the second aspect.

[0083] In a specific example, the battery includes at least one of a sodium ion battery, a potassium ion battery and a zinc-manganese battery; a zinc-manganese battery can be selected, and an aqueous zinc-manganese battery can be further selected.

[0084] In a specific example, a battery includes positive and negative electrode sheets, a separator and an electrolyte spaced between the positive and negative electrode sheets.

[0085] Among them, the positive and negative electrode sheets can be the electrode sheets described above.

[0086] In the present application, there is no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0087] In a specific example, the material of the isolation membrane can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0088] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0089] In a specific example, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0090] 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 bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0091] In a specific example, 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, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0092] In a specific example, when the battery is a zinc-manganese battery, the electrolyte may be one or more of ammonium chloride, zinc chloride, potassium hydroxide, sodium hydroxide, zinc sulfate, and manganese sulfate, and the solvent may be water.

[0093] In a specific example, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a lamination process.

[0094] In a specific example, the battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0095] In a specific example, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery can also be a soft shell, such as a bag-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0096] The fourth aspect of the present application provides an electrical device, comprising the electrode described in the first aspect or the electrode prepared by the preparation method described in the second aspect, or the battery described in the third aspect.

[0097] In a specific example, the power-consuming device may be a mobile phone, a laptop computer, a smartwatch, an electric car, a medical device, a portable charging station, aerospace equipment, a smart home, or an energy storage power station. The energy storage power station may be a photovoltaic energy storage station, a wind power energy storage station, a hydropower energy storage station, a thermal power energy storage station, or the like.

[0098] Unless otherwise specified, the raw materials used in the following experiments can be purchased from the market.

[0099] Polyhydroxyalkanoates (PHA): average molecular weight of 100,000, 200,000, 400,000, 500,000, 800,000, 1.2 million, 1.5 million, 2 million, 2.4 million, 2.7 million, 2.8 million, or 3 million, provided by Guangdong Hefeng Biotechnology Co., Ltd.

[0100] PTFE: purchased from Daikin Corporation, Japan;

[0101] Polyvinylidene fluoride (PVDF): purchased from Arkema, France;

[0102] Polyethylene oxide: purchased from Sumitomo Corporation of Japan;

[0103] Super P Li: purchased from Lion (International) Co., Ltd., Japan;

[0104] Activated carbon: purchased from Toray Industries, Ltd., Japan;

[0105] Current collector: nickel mesh, purchased from Hebei Chaoqun Waterproof Materials Co., Ltd.

[0106] The following are specific examples.

[0107] Example 1

[0108] Preparation method of positive electrode sheet:

[0109] 1) Preparing a first mixture: mixing the active material manganese dioxide, the conductive agent super P Li, and the conductive agent activated carbon in a mass ratio of 35:6:4 (i.e., the mass ratio of the active material to the conductive agent is 7:2, and the mass ratio of super P Li to the activated carbon is 1.5:1) to obtain a first mixture.

[0110] 2) Preparing a second mixture: adding PHA with an average molecular weight of 500,000 and PHA with an average molecular weight of 2,000,000 to the first mixture, stirring at 4,000 rpm for 2 minutes to uniformly mix; then adding a non-biodegradable binder (PTFE) and stirring at 4,000 rpm for 2 minutes, 6,000 rpm for 2 minutes, and 7,500 rpm for 5 minutes to uniformly mix and completely fiberize, to obtain a second mixture; wherein the PHA with an average molecular weight of 500,000, the PHA with an average molecular weight of 2,000,000, and the PTFE together constitute a composite binder, and in the composite binder, the mass ratio of the three is 1.95:2.05:1; and the mass ratio of the active substance to the composite binder is 7:1;

[0111] 3) Preparation of active layer: The second mixture was placed in a roller press, the temperature of the roller press was controlled to 100°C, the thickness of the roller press was adjusted to 500 μm, and the active layer was obtained by roller pressing (pressure 2T; temperature 100°C).

[0112] 4) Preparation of positive electrode sheet: The formed active layer is composited onto the current collector (nickel mesh) by roller pressing, placed in a forced air oven, and dried at 120°C overnight to prepare the positive electrode sheet.

[0113] Example 2

[0114] The same procedures as in Example 1 were employed except that the mass ratio of the active substance to the composite binder was 3:1 and the composite binder contained PHA with an average molecular weight of 100,000 and PHA and PVDF with an average molecular weight of 2.7 million at a mass ratio of 1:4:1.

[0115] Example 3

[0116] The same procedures as in Example 1 were employed except that the mass ratio of the active substance to the composite binder was 12:1 and the composite binder contained PHA with an average molecular weight of 200,000 and PHA and PTFE with an average molecular weight of 2.8 million at a mass ratio of 4:1:1.

[0117] Example 4

[0118] The same procedures as in Example 1 were employed except that the composite binder contained PHA with an average molecular weight of 400,000 and PHA and PTFE with an average molecular weight of 3,000,000 at a mass ratio of 2:2:1.

[0119] Example 5

[0120] The same procedures as in Example 4 were employed except that the composite binder used PHA with an average molecular weight of 400,000, PHA with an average molecular weight of 800,000, and PHA with an average molecular weight of 3,000,000 and PTFE at a mass ratio of 1:1:2:1.

[0121] Example 6

[0122] The same procedures as in Example 3 were employed except that the composite binder contained PHA with an average molecular weight of 200,000, PHA with an average molecular weight of 1.2 million, and PHA with an average molecular weight of 2.8 million, and PTFE in a mass ratio of 2:2:1:1.

[0123] Example 7

[0124] Preparation of negative electrode sheet:

[0125] Except for using zinc powder as the active material to prepare the negative electrode sheet, the rest is the same as Example 1.

[0126] Comparative Example 1

[0127] The same procedures as in Example 1 were followed except that the composite binder was replaced with PHA having an average molecular weight of 500,000.

[0128] Comparative Example 2

[0129] The same procedures as in Example 1 were followed except that the composite binder was replaced with PHA having an average molecular weight of 2,000,000.

[0130] Comparative Example 3

[0131] Except that the composite binder is replaced by PTFE, the rest is the same as Example 1.

[0132] Comparative Example 4

[0133] The same procedures as in Example 1 were employed except that the composite binder used PHA and PTFE with an average molecular weight of 500,000 in a mass ratio of 4:1.

[0134] Comparative Example 5

[0135] The same procedures as in Example 1 were employed except that the composite binder used PHA and PTFE with an average molecular weight of 2 million at a mass ratio of 4:1.

[0136] Test Case

[0137] The positive electrode sheets of the embodiments and comparative examples were made into batteries, and the preparation steps were as follows: the positive electrode sheets of the above embodiments 1-6 and comparative examples 1-5 were used as the positive electrode, the negative electrode sheet of embodiment 7 was used as the negative electrode, a glass fiber separator was used as the diaphragm, and an aqueous solution of 2.5MZnSO4, 0.5M MnSO4, and 1% PEG-2000 was used as the electrolyte, and the batteries were assembled into aqueous zinc-manganese batteries.

[0138] The assembled batteries were tested for the following performances, and the results are shown in Table 1:

[0139] The cycle test uses the Xinwei battery test system, discharging to 1.0V at a constant current of 0.1C, and then charging to 1.8V, recording the battery's first-cycle discharge capacity Q1; then this is regarded as a cycle, and the cycle is repeated 100 times, recording the discharge capacity Q2 after 100 cycles; the capacity retention rate after 100 cycles is calculated by Q2 / Q1×100%, and the discharge capacity retention rate is calculated.

[0140] Table 1 Summary of performance of examples and comparative examples

[0141]

[0142] As can be seen from Table 1, the examples use PHAs of different molecular weights and non-biodegradable binders in combination. Compared with Comparative Examples 1-3 which use only PHA or non-biodegradable binders, Comparative Example 4 uses a single molecular weight PHA and non-biodegradable binder, which is beneficial to improving the first-cycle discharge specific capacitance and post-cycle capacity retention of the battery.

[0143] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0144] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A pole piece, characterized in that: It includes a current collector and an active layer arranged on the surface of the current collector; The active layer includes active material and composite binder; The composite binder includes a first polyhydroxyalkanoate, a second polyhydroxyalkanoate and a non-biodegradable binder; The average molecular weight of the first polyhydroxyalkanoate is 100,000-600,000; the average molecular weight of the second polyhydroxyalkanoate is 1.5 million-3 million.

2. The pole piece according to claim 1, characterized in that In the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate and the non-biodegradable binder is 1-4:1-4:

1.

3. The pole piece according to claim 1 or 2, characterized in that: The composite binder further includes a third polyhydroxyalkanoate; the average molecular weight of the third polyhydroxyalkanoate is 800,000-1.2 million.

4. The pole piece according to claim 3, characterized in that: In the composite binder, the mass ratio of the first polyhydroxyalkanoate, the second polyhydroxyalkanoate, the third polyhydroxyalkanoate and the non-biodegradable binder is 0.5-2:0.5-2:1-4:

1.

5. The pole piece according to claim 1 or 2, characterized in that: One or more of the following conditions are met: (1) The electrode is a positive electrode or a negative electrode; (2) The non-biodegradable binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide and cellulose binder; (3) The active layer further includes a conductive agent; (4) The mass ratio of the active material to the conductive agent is (4-10): (1-6); (5) The mass ratio of the active substance to the composite binder is (3-15):1; (6) In the active layer, the mass proportion of the active material is 50%-90%; (7) The thickness of the active layer is 100 μm-1000 μm.

6. The pole piece according to claim 5, characterized in that: One or more of the following conditions are met: (1) The active material of the positive electrode plate includes at least one of manganese dioxide, manganese trioxide and manganese tetraoxide; (2) The active material of the negative electrode plate includes zinc metal or manganese metal; (3) The cellulose binder includes at least one of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, microcrystalline cellulose and hydroxyethyl cellulose; (4) The conductive agent includes at least one of Super-Li, activated carbon, carbon nanotubes, acetylene black, Ketjen black and graphite.

7. A method for preparing a pole piece, characterized in that: The steps include: mixing the active material and the conductive agent to form a first mixture; The first mixture and a composite binder are mixed and subjected to a fiberization treatment to form a second mixture; the composite binder comprises a first polyhydroxyalkanoate, a second polyhydroxyalkanoate, and a non-biodegradable binder; the first polyhydroxyalkanoate has an average molecular weight of 100,000 to 600,000; the second polyhydroxyalkanoate has an average molecular weight of 1.5 million to 3 million; forming the second mixture into a film to form an active layer; The active layer is compounded with the current collector to form the pole piece.

8. The preparation method according to claim 7, wherein The film forming includes at least one of roller film forming, extrusion film forming, dry spray film forming and hot pressing film forming; optionally, the conditions of roller film forming include: pressure 1T-4T; temperature 80℃-120℃.

9. A battery, characterized in that: The invention comprises the pole piece according to any one of claims 1 to 6 or the pole piece prepared by the preparation method according to claim 7 or 8.

10. An electrical device, characterized in that: The invention comprises the pole piece according to any one of claims 1 to 6, the pole piece prepared by the preparation method according to claim 7 or 8, or the battery according to claim 9.

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