Electrode plate, preparation method thereof and battery

Abstract

The invention provides an electrode plate, a preparation method thereof and a battery, and relates to the technical field of secondary batteries. The electrode plate comprises a current collector layer, an active substance layer is formed on at least one side of the current collector layer, the active substance layer comprises an active substance, a conductive agent, a binder, a first pore-forming agent and a second pore-forming agent, the first pore-forming agent and the second pore-forming agent are both soluble in a polar organic solvent, the first pore-forming agent and the second pore-forming agent are both high-molecular polymers, and the conductive agent and the binder are both soluble in a polar organic solvent. The first pore-forming agent is granular, and the second pore-forming agent is one or a combination of a plurality of materials selected from a fibrous material, a tubular material and a sheet material. After the battery is assembled, the polar organic solvent in the electrolyte can dissolve the first pore-forming agent and the second pore-forming agent through the processes such as placement aging or charging and discharging, and three-dimensional holes are left in the electrode plate, so that the infiltration effect of the electrode plate on the electrolyte is improved, and sufficient infiltration of the electrolyte and rapid transmission of ions are facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to an electrode plate and a preparation method thereof, and a battery. Background Art

[0002] In secondary batteries, increasing the surface density of positive and negative electrodes is considered to be an effective means to increase battery energy density, but at the same time it will also cause the positive and negative electrodes to become less wettable and the ions to diffuse slowly, resulting in a decrease in battery performance. Therefore, pores need to be formed in the electrode plates.

[0003] In the conventional technology, a pore-forming agent is added to the electrode slurry, applied to the electrode sheet, and then subjected to a high-temperature sintering treatment to volatilize the pore-forming agent, thereby leaving holes in the obtained electrode sheet, thereby improving the wetting effect of the electrolyte.

[0004] However, high-temperature sintering treatment will cause the polymer binder in the electrode to carbonize, making it unable to effectively exert its bonding ability, and cause a significant decrease in the cohesive strength and peel strength of the electrode plate. Summary of the invention

[0005] Based on this, it is necessary to provide an electrode plate and a method for preparing the electrode plate, and a battery that can form holes in the electrode plate without using high-temperature sintering.

[0006] In a first aspect, the present application provides an electrode plate, comprising a current collector layer, an active material layer formed on at least one side of the current collector layer, the active material layer comprising an active material, a conductive agent, a binder, a first pore former and a second pore former, both of which are soluble in polar organic solvents, both of which are high molecular polymers, the first pore former is granular, and the second pore former is one or more combinations of fibrous, tubular, and sheet-like.

[0007] The first pore former and the second pore former in the active material layer of the electrode plate provided in the present application are both polymers, which have good solubility in polar organic solvents, and the polymers have thermoplasticity, so a variety of processing methods can be used to prepare polymers of different morphologies as the first pore former and the second pore former. The first pore former is set to be granular. Specifically, dispersion polymerization, emulsion polymerization, and seed swelling polymerization can be used to form microspherical granular polymer materials when the polymer as the first pore former is polymerized. The second pore former is set to be fibrous. Specifically, the polymer as the second pore former can be dissolved in a polar organic solvent, and a fibrous polymer material can be prepared by electrospinning. Alternatively, the second pore former is set to be tubular. Specifically, a tubular polymer material can be prepared by a porous template method, and the polymer as the second pore former is dissolved in a polar organic solvent to obtain a polymer solution, and then the polymer solution is infiltrated into the pores of the porous alumina template, and then the template is removed to prepare a tubular polymer material. Alternatively, the second pore-forming agent is set to be in sheet form. Specifically, a sheet-like polymer material can be prepared by common plastic film processing techniques such as casting, extrusion and blow molding, or a nano-sheet polymer material can be prepared by a soft template method.

[0008] The present application adds a first pore-forming agent and a second pore-forming agent of a polymer material to the active material layer at the same time, wherein the first pore-forming agent is in a granular form, and the second pore-forming agent is in a fiber-shaped, tubular, or sheet-shaped form or a combination thereof, and both the first pore-forming agent and the second pore-forming agent are soluble in polar organic solvents. Thus, after a battery is prepared using the electrode plate provided by the present application, after being placed for aging or charge-discharge processes, the polar organic solvent in the electrolyte can dissolve the first pore-forming agent and the second pore-forming agent, thereby leaving holes in the electrode plate. In addition, the first pore-forming agent in a granular form can form circular holes, i.e., generate zero-dimensional holes; the second pore-forming agent in a fiber-shaped, tubular, or sheet-shaped form can form holes with extended lengths such as fiber-shaped, tubular, or sheet-shaped holes, i.e., generate one-dimensional and / or two-dimensional holes. Thereby, holes of different morphologies are formed in the electrode plate. The holes with extended length formed by the second pore-forming agent can connect the circular holes formed by the first pore-forming agent and dispersed in the electrode plate, so as to realize a three-dimensional network hole structure in the electrode plate. The existence of the three-dimensional network holes can improve the wetting effect of the electrode plate on the electrolyte, which is beneficial to the sufficient wetting of the electrolyte and the rapid transmission of ions. At the same time, the pore-forming method provided in the present application does not require high-temperature treatment, thereby avoiding the binder being damaged by high temperature.

[0009] In one embodiment, the active material layer includes, by mass percentage: 94% to 99% of active material, 0.2% to 3% of conductive agent, 0.2% to 3% of binder, 0.05% to 2% of first pore former and 0.05% to 2% of second pore former; wherein the sum of the mass of the first pore former and the second pore former accounts for 0.2% to 3% of the mass percentage of the active material layer.

[0010] In one embodiment, the mass ratio of the second pore-forming agent to the first pore-forming agent is (0.8-7.5):1.

[0011] In one embodiment, the single-sided surface density of the active material layer is 100 g / m 2 ~300 g / m 2 ; and / or, the single-sided thickness of the active material layer is 70μm~400μm.

[0012] In one embodiment, the first pore-forming agent and / or the second pore-forming agent include one or more combinations of homopolymers of ethylene monosubstituted, homopolymers of ethylene 1,1-disubstituted, copolymers of ethylene monosubstituted, copolymers of ethylene 1,1-disubstituted, and copolymers of ethylene monosubstituted and ethylene 1,1-disubstituted.

[0013] In one embodiment, the homopolymer of the ethylene monosubstituted product includes at least one of polystyrene, polyvinyl carbazole, polyvinyl acetate, polymethyl acrylate, and polybutyl acrylate.

[0014] In one embodiment, the homopolymer of ethylene 1,1-disubstituted product includes at least one of polymethyl methacrylate, polylauryl methacrylate, polybutyl methacrylate, and poly-α-methylstyrene.

[0015] In one embodiment, the copolymer of the ethylene monosubstituted product includes at least one of poly(styrene-co-vinyl carbazole), poly(styrene-co-vinyl acetate), poly(styrene-co-methyl acrylate), poly(styrene-co-butyl acrylate), poly(vinyl carbazole-co-vinyl acetate), poly(vinyl carbazole-co-methyl acrylate), poly(vinyl carbazole-co-butyl acrylate), poly(vinyl acetate-co-methyl acrylate), and poly(vinyl acetate-co-butyl acrylate).

[0016] In one embodiment, the copolymer of ethylene 1,1-disubstituted products includes at least one of poly(methyl methacrylate-co-lauryl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(methyl methacrylate-co-α-methylstyrene), poly(lauryl methacrylate-co-butyl methacrylate), poly(lauryl methacrylate-co-α-methylstyrene), and poly(butyl methacrylate-co-α-methylstyrene).

[0017] In one embodiment, the copolymer of ethylene monosubstituted and ethylene 1,1-disubstituted includes at least one of poly(styrene-co-methyl methacrylate), poly(methyl acrylate-co-methyl methacrylate), and poly(butyl acrylate-co-methyl methacrylate).

[0018] In one embodiment, the particle size of the first pore-forming agent is 0.02 μm to 2 μm.

[0019] In one embodiment, the second pore-forming agent satisfies at least one of the following (1) to (3):

[0020] (1) The diameter of the fiber is 0.02 μm~2 μm, and the length is 2 μm~200 μm;

[0021] (2) The inner diameter of the tubular tube is 0.02 μm~2 μm, the outer diameter is 0.03 μm~3 μm, and the length is 2 μm~200 μm;

[0022] (3) The thickness of the sheet is 0.01μm~0.5μm, and the circumference is 1μm~500μm.

[0023] In a second aspect, the present application also provides a method for preparing the electrode sheet, comprising the following steps:

[0024] Applying electrode slurry on the current collector layer to obtain an intermediate; the electrode slurry includes an active material, a conductive agent, a binder, a first solvent, a first pore-forming agent and a second pore-forming agent;

[0025] The intermediate is dried, pressed and cut to obtain electrode plates.

[0026] In one embodiment, the solid matter in the electrode slurry includes, by mass percentage, 94% to 99% of active material, 0.2% to 3% of conductive agent, 0.2% to 3% of binder, 0.2% to 3% of first pore-forming agent and second pore-forming agent, wherein the mass percentage of the first pore-forming agent is 0.05% to 2%, and the mass percentage of the second pore-forming agent is 0.05% to 2%. The above solid matter is dispersed in a first solvent to obtain the electrode slurry, and the mass percentage of the solid matter in the electrode slurry is 35% to 80%.

[0027] In one embodiment, the mass ratio of the second pore-forming agent to the first pore-forming agent is (0.8-7.5):1.

[0028] In a third aspect, the present application also provides a battery obtained by aging a battery precursor, wherein the battery precursor includes the electrode plate and an electrolyte, wherein the electrolyte includes a polar organic solvent; and the polar organic solvent includes a carboxylate solvent and a carbonate solvent.

[0029] In one embodiment, the carboxylate solvent includes at least one of ethyl acetate, propyl acetate, methyl formate, methyl acetate, methyl butyrate, and ethyl propionate.

[0030] In one embodiment, the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

[0031] It should be noted that polar organic solvents include carboxylate solvents and carbonate solvents, among which carboxylate solvents have stronger polarity, better dissolution effect on the first pore-forming agent and the second pore-forming agent, and higher dielectric constant, lower viscosity and lower freezing point, so it is beneficial to improve the ionic conductivity of the electrolyte at low temperature and the fast charging performance of the battery; in addition, carbonate solvents help to form a more stable SEI film (Solid Electrolyte Interface membrane), which is beneficial to improve the cycle performance of the battery.

[0032] In the above-mentioned electrode plate, a first pore-forming agent and a second pore-forming agent of a polymer material are added simultaneously to the active material layer, wherein the first pore-forming agent is granular, and the second pore-forming agent is one or more combinations of fibrous, tubular, and sheet-like, and both the first pore-forming agent and the second pore-forming agent are soluble in polar organic solvents. In this way, after a battery is prepared using the electrode plate provided by the present application, after being placed for aging or charge and discharge processes, the polar organic solvent in the electrolyte can dissolve the first pore-forming agent and the second pore-forming agent, thereby leaving holes in the electrode plate. Furthermore, the first pore-forming agent in granular form can form circular holes, and the second pore-forming agent in fibrous, tubular or sheet form can form holes with extended lengths, thereby forming holes of different morphologies in the electrode plate. The holes with extended lengths formed by the second pore-forming agent can connect the circular holes formed by the first pore-forming agent dispersed in the electrode plate, thereby realizing a three-dimensional network hole structure in the electrode plate. The presence of the three-dimensional network holes can improve the wetting effect of the electrode plate on the electrolyte, which is beneficial to the sufficient wetting of the electrolyte and the rapid transmission of ions. At the same time, the pore-forming method provided in the present application does not require high-temperature treatment, thereby avoiding the binder being damaged by high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of a method for preparing an electrode plate according to an embodiment. DETAILED DESCRIPTION

[0034] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0035] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0036] In the present 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.

[0037] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] If there is no special explanation, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S12 and S14, which means that the method may include steps S12 and S14 performed sequentially, or may include steps S14 and S12 performed sequentially. For example, it is mentioned that the method may also include step S16, which means that step S16 may be added to the method in any order, for example, the method may include steps S12, S14 and S16, or may include steps S12, S16 and S14, or may include steps S16, S12 and S14, etc.

[0041] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0042] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, 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).

[0043] An electrode plate includes a current collector layer, an active material layer is formed on at least one side of the current collector layer, the active material layer includes an active material, a conductive agent, a binder, a first pore former and a second pore former, the first pore former and the second pore former are both high molecular polymers, both the first pore former and the second pore former are soluble in polar organic solvents, the first pore former is granular, and the second pore former is one or more combinations of fibrous, tubular, and sheet-like.

[0044] In the above-mentioned electrode plate, a first pore former and a second pore former of a polymer material are added simultaneously to the active material layer, wherein the first pore former is granular, and the second pore former is a combination of one or more of fibrous, tubular, and sheet-like, and both the first pore former and the second pore former are soluble in polar organic solvents. Thus, after a battery is prepared using the electrode plate provided by the present application, after being placed for aging or charge and discharge, the polar organic solvent in the electrolyte can dissolve the first pore former and the second pore former, thereby leaving holes in the electrode plate. In addition, the granular first pore former can form circular holes, i.e., generate zero-dimensional holes; the fibrous, tubular, or sheet-like second pore former can form fibrous, tubular, or sheet-like holes and other holes with extended lengths, i.e., generate one-dimensional and / or two-dimensional holes. Thereby, holes of different morphologies are formed in the electrode plate. The holes with extended length formed by the second pore-forming agent can connect the circular holes formed by the first pore-forming agent and dispersed in the electrode plate, so as to realize a three-dimensional network hole structure in the electrode plate. The existence of the three-dimensional network holes can improve the wetting effect of the electrode plate on the electrolyte, which is beneficial to the sufficient wetting of the electrolyte and the rapid transmission of ions. At the same time, the pore-forming method provided in the present application does not require high-temperature treatment, thereby avoiding the binder being damaged by high temperature.

[0045] For example, the current collector layer may be aluminum foil, copper foil or a composite current collector. The composite current collector is a sandwich structure with an insulating layer in the middle and metal layers on both sides.

[0046] For example, the conductive agent may be any one of carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and carbon fibers, or a combination of at least two thereof.

[0047] Exemplarily, the binder may be an aqueous binder, which is a polymer binder using water as a solvent or dispersant, and includes any one of polyacrylic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, sodium carboxymethyl starch, agar, gum arabic, and styrene-butadiene rubber, or a combination of at least two thereof.

[0048] In some embodiments, the active material layer includes, by mass percentage: 94%~99% active material, 0.2%~3% conductive agent, 0.2%~3% binder, 0.05%~2% first pore former and 0.05%~2% second pore former; wherein the sum of the mass of the first pore former and the second pore former accounts for 0.2~3% of the mass percentage of the active material layer.

[0049] If the total amount of the first pore-forming agent and the second pore-forming agent is too low, after being dissolved by the polar organic solvent in the electrolyte during aging or charge-discharge processes, the generated pores are scattered and insufficient in number, resulting in an insufficient three-dimensional pore structure. On the one hand, it will cause the porosity of the electrode plate to decrease, the charge transfer impedance to increase, the gram capacity to decrease, and the internal resistance of the battery to increase. On the other hand, it is not conducive to the effective wetting of the electrolyte on the electrode plate, thereby failing to effectively improve the electrochemical performance of the battery using the electrode plate. If the total amount of the first pore-forming agent and the second pore-forming agent is too high, on the one hand, it will cause the porosity of the electrode plate to be too high, thereby reducing the structural strength of the electrode plate. On the other hand, it will cause the content of active materials in the electrode plate to decrease, thereby reducing the gram capacity of the electrode plate and reducing the electrochemical performance of the battery such as the rate performance and charge-discharge cycle.

[0050] In some embodiments, the mass ratio of the second pore-forming agent to the first pore-forming agent is (0.8-7.5): 1, so that an appropriate number of connecting channels and circular holes can be formed. When forming holes, the holes in the extended structure formed by the second pore-forming agent can serve as connecting channels to connect the circular holes formed by the first pore-forming agent, and finally form a good three-dimensional hole structure, thereby improving the wetting effect of the electrode plate on the electrolyte.

[0051] If the mass ratio of the second pore former to the first pore former is too low, since there is not enough second pore former to be dissolved by the polar organic solvent in the electrolyte and generate pores with extended lengths after aging or charge and discharge, the electrolyte cannot smoothly diffuse in the electrode plate and dissolve all the first pore formers, and thus, not enough circular holes can be generated. In addition, since there are not enough fibrous, tubular or sheet-like holes and circular holes to form a three-dimensional network pore structure, the three-dimensional pore structure formed is not good enough. On the one hand, it will cause the porosity of the electrode plate to decrease, the charge transfer impedance to increase, the gram capacity to decrease, and the internal resistance of the battery to increase. On the other hand, it cannot provide sufficient ion diffusion channels, which will affect the rate performance and electrochemical properties such as charge and discharge cycle of the battery using the electrode plate. If the mass ratio of the second pore-forming agent to the first pore-forming agent is too high, more fibrous, tubular or sheet-like holes will be produced after the electrode plate is dissolved by the polar organic solvent in the electrolyte during aging or charge and discharge processes, making the formed three-dimensional hole structure unstable. On the one hand, it will cause the porosity of the electrode plate to decrease, the charge transfer impedance to increase, the gram capacity to decrease and the internal resistance of the battery to increase. On the other hand, it will cause the structural integrity and stability of the electrode plate to decrease and affect the cycle stability of the battery using the electrode plate.

[0052] Exemplarily, the mass fraction of the active material may be, but is not limited to, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5% or 99%, etc. Exemplarily, the mass fraction of the conductive agent may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. Exemplarily, the mass fraction of the binder may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. Exemplarily, the total mass fraction of the first pore-forming agent and the second pore-forming agent may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. In this way, the amount of active material can be guaranteed, so that the battery has a good energy density, and an appropriate amount of holes can be formed in the electrode plate to improve the wettability of the electrolyte and the transmission effect of ions.

[0053] For example, the mass fraction of the first pore-forming agent may be, but is not limited to, 0.05%, 0.1%, 0.12%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc. Further, the mass fraction of the first pore-forming agent may be, but is not limited to, 0.2% to 1%.

[0054] For example, the mass fraction of the second pore-forming agent may be, but is not limited to, 0.05%, 0.1%, 0.12%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc. Further, the mass fraction of the second pore-forming agent may be, but is not limited to, 0.8% to 1.5%.

[0055] For example, the mass percentage of the sum of the mass of the first pore former and the second pore former in the active material layer may be, but is not limited to, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0056] Illustratively, the mass ratio of the second pore former to the first pore former may be, but is not limited to, 0.8:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, etc.

[0057] In some embodiments, the single-sided surface density of the active material layer is 100 g / m 2 ~300 g / m 2 ; and / or, the single-sided thickness of the active material layer is 70μm~400μm.

[0058] For example, the single-sided surface density of the active material layer may be, but is not limited to, 100 g / m 2, 120 g / m 2 , 150 g / m 2 , 180 g / m 2 , 200 g / m 2 , 220 g / m 2 , 250 g / m 2 , 280 g / m 2 or 300 g / m 2 In the above range, the gram weight of the active material layer is guaranteed, while excessive density is avoided to reduce the infiltration effect of the electrolyte.

[0059] Exemplarily, the single-sided thickness of the active material layer may be 70 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm or 400 μm, etc. Within the above range, the transmission effect of ions is guaranteed and the transmission path is prevented from being too long. Further, the single-sided thickness of the active material layer may be 200 μm to 300 μm.

[0060] In some embodiments, the first pore-forming agent and / or the second pore-forming agent include one or more combinations of homopolymers of ethylene monosubstituted, homopolymers of ethylene 1,1-disubstituted, copolymers of ethylene monosubstituted, copolymers of ethylene 1,1-disubstituted, and copolymers of ethylene monosubstituted and ethylene 1,1-disubstituted. Copolymers of ethylene monosubstituted refer to copolymers formed by several different monosubstituted ethylene, that is, the monomers of the copolymers are all ethylene monosubstituted. Copolymers of ethylene 1,1-disubstituted refer to copolymers formed by several different 1,1-disubstituted ethylene, that is, the monomers of the copolymers are all ethylene 1,1-disubstituted. Copolymers of ethylene monosubstituted and ethylene 1,1-disubstituted refer to at least one monomer of the copolymer is ethylene monosubstituted, and at least one monomer is ethylene 1,1-disubstituted.

[0061] Illustratively, the first pore former and the second pore former may both be homopolymers of ethylene monosubstituted; one of the first pore former and the second pore former may be a homopolymer of ethylene monosubstituted and the other a homopolymer of ethylene 1,1-disubstituted; one of the first pore former and the second pore former may be a copolymer of ethylene monosubstituted and the other a copolymer of ethylene 1,1-disubstituted, and so on.

[0062] Illustratively, the homopolymer of ethylene monosubstituted product includes at least one of polystyrene, polyvinyl carbazole, polyvinyl acetate, polymethyl acrylate, and polybutyl acrylate.

[0063] Illustratively, the homopolymer of ethylene 1,1-disubstituted product includes at least one of polymethyl methacrylate, polylauryl methacrylate, polybutyl methacrylate, and poly-α-methylstyrene.

[0064] Exemplarily, the copolymer of ethylene monosubstituted products includes at least one of poly(styrene-co-vinyl carbazole), poly(styrene-co-vinyl acetate), poly(styrene-co-methyl acrylate), poly(styrene-co-butyl acrylate), poly(vinyl carbazole-co-vinyl acetate), poly(vinyl carbazole-co-methyl acrylate), poly(vinyl carbazole-co-butyl acrylate), poly(vinyl acetate-co-methyl acrylate), and poly(vinyl acetate-co-butyl acrylate).

[0065] Exemplarily, the copolymer of ethylene 1,1-disubstituted products includes at least one of poly(methyl methacrylate-co-lauryl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(methyl methacrylate-co-α-methylstyrene), poly(lauryl methacrylate-co-butyl methacrylate), poly(lauryl methacrylate-co-α-methylstyrene), and poly(butyl methacrylate-co-α-methylstyrene).

[0066] Illustratively, the copolymer of ethylene monosubstituted and ethylene 1,1-disubstituted includes at least one of poly(styrene-co-methyl methacrylate), poly(methyl acrylate-co-methyl methacrylate), and poly(butyl acrylate-co-methyl methacrylate).

[0067] In some embodiments, the particle size of the first pore-forming agent is 0.02 μm to 2 μm. Exemplarily, the particle size of the first pore-forming agent may be 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm or 2 μm. Within the above range, after the first pore-forming agent is dissolved in the polar organic solvent in the electrolyte through aging or charge and discharge processes, it can leave holes of corresponding sizes in the electrode plate, so that the holes of such pore size can maintain the mechanical strength of the electrode plate, and form a space for containing the electrolyte, thereby improving the infiltration effect of the electrolyte. Further, the particle size of the first pore-forming agent is 0.5 μm to 1.2 μm.

[0068] In some embodiments, the second pore-forming agent satisfies at least one of the following (1) to (3): (1) the diameter of the fiber is 0.02 μm to 2 μm, and the length is 2 μm to 200 μm; (2) the inner diameter of the tubular is 0.02 μm to 2 μm, the outer diameter is 0.03 μm to 3 μm, and the length is 2 μm to 200 μm; (3) the thickness of the sheet is 0.01 μm to 0.5 μm, and the circumference is 1 μm to 500 μm. Exemplarily, the fiber, tubular and sheet all have an extension direction, such as the extension direction of the fiber and tubular is the length direction, and the extension direction of the sheet is the long side direction. In this way, the holes formed with the extension direction can connect the circular holes formed by the first pore-forming agent, thereby forming a three-dimensional hole structure. It can be understood that the length of the second pore-forming agent should be within a suitable range, so that the purpose of connecting the circular holes can be achieved and the mechanical strength of the electrode sheet can be prevented from being deteriorated, such as the peeling strength.

[0069] For example, when the second pore-forming agent includes a fibrous structure, the diameter of the fibrous structure may be, but is not limited to, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm or 2 μm. The length may be, but is not limited to, 2 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm or 200 μm.

[0070] Illustratively, when the second pore-forming agent includes a tubular structure, the inner diameter of the tubular structure may be, but is not limited to, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm or 2 μm. The outer diameter may be, but is not limited to, 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 2 μm, 2.4 μm, 2.8 μm or 3 μm. The length may be, but is not limited to, 2 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm or 200 μm.

[0071] For example, when the second pore forming agent includes a sheet structure, the thickness of the sheet structure may be, but is not limited to, 0.01 μm, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm or 0.5 μm. The perimeter may be, but is not limited to, 1 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm or 500 μm.

[0072] In some embodiments, the active material includes at least one of a lithium ion battery positive electrode active material, a lithium ion battery negative electrode active material, a sodium ion battery positive electrode active material, a sodium ion battery negative electrode active material, and a lithium sulfur battery positive electrode active material.

[0073] Exemplarily, the electrode plate can be used in lithium-ion batteries, such as as the positive electrode of a lithium-ion battery, in which case the active material is the positive electrode active material of a lithium-ion battery, and the positive electrode active material of a lithium-ion battery includes any one or a combination of at least two of lithium iron manganese phosphate, lithium vanadium phosphate, lithium iron phosphate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, and lithium cobalt oxide. It can also be used as the negative electrode of a lithium-ion battery, in which case the active material is the negative electrode active material of a lithium-ion battery, and the negative electrode active material of a lithium-ion battery includes any one or a combination of at least two of graphite, lithium titanate, silicon, and silicon oxide.

[0074] For example, the electrode plate can be applied to a sodium ion battery, such as a positive electrode of a sodium ion battery. In this case, the active material is a positive electrode active material of a sodium ion battery, and the positive electrode active material of a sodium ion battery includes O 3 -Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 2 、Na x M 1 [M 2 (CN) 6 ] (where M 1 =Ni, Fe, Mn, M 2 =Fe, Mn), NaFePO 4 、Na 3 V 2 (PO 4 ) 3 It can also be used as the negative electrode of a sodium ion battery, in which case the active material is a negative electrode active material of a sodium ion battery, and the negative electrode active material of a sodium ion battery can be any one of hard carbon and soft carbon or a combination of at least two of them.

[0075] Exemplarily, the electrode plate can be applied to a lithium-sulfur battery, such as as a positive electrode of a lithium-sulfur battery. In this case, the active material is a positive electrode active material of a lithium-sulfur battery, and the positive electrode active material of a lithium-sulfur battery can be sulfur.

[0076] See also Figure 1 The present application also provides a method for preparing an electrode sheet, comprising the following steps:

[0077] S11, coating the electrode slurry on the current collector layer to obtain an intermediate; the electrode slurry includes an active material, a conductive agent, a binder, a first solvent, a first pore-forming agent and a second pore-forming agent.

[0078] S12, drying the intermediate, pressing and cutting to obtain electrode plates.

[0079] In some embodiments, the solid matter in the electrode slurry includes, by mass percentage, 94% to 99% of active material, 0.2% to 3% of conductive agent, 0.2% to 3% of binder, 0.05% to 2% of first pore former and 0.05% to 2% of second pore former; wherein the sum of the mass of the first pore former and the second pore former accounts for 0.2% to 3% of the mass percentage of the active material layer. The above solid matter is dispersed in a first solvent to obtain the electrode slurry, and the mass percentage of the solid matter in the electrode slurry is 35% to 80%.

[0080] In some embodiments, the mass ratio of the second pore-forming agent to the first pore-forming agent is (0.8-7.5):1.

[0081] Exemplarily, the mass fraction of the active material may be, but is not limited to, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5% or 99%, etc. Exemplarily, the mass fraction of the conductive agent may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. Exemplarily, the mass fraction of the binder may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. Exemplarily, the total mass fraction of the first pore-forming agent and the second pore-forming agent may be, but is not limited to, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5% or 3%, etc. The first solvent may be water, and the mass fraction of the first solvent may be, but is not limited to, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%, etc.

[0082] For example, the mass fraction of the first pore former may be, but is not limited to, 0.05%, 0.1%, 0.12%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc.

[0083] For example, the mass fraction of the second pore former may be, but is not limited to, 0.05%, 0.1%, 0.12%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc.

[0084] Illustratively, the mass percentage of the sum of the masses of the first pore former and the second pore former in the active material layer may be, but is not limited to, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%.

[0085] Illustratively, the mass ratio of the second pore former to the first pore former may be, but is not limited to, 0.8:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, etc.

[0086] The present application also provides a battery, which is obtained by aging a battery precursor, wherein the battery precursor includes an electrode plate and an electrolyte, wherein the electrolyte includes a polar organic solvent; the polar organic solvent includes a carboxylic acid ester solvent and a carbonate ester solvent. Thus, during the aging treatment, the first pore-forming agent and the second pore-forming agent can be dissolved in the polar organic solvent of the electrolyte, leaving pores in the battery plate.

[0087] Exemplarily, the electrolyte includes a carboxylate solvent and a carbonate solvent. Further, the mass ratio of the carboxylate solvent to the carbonate solvent is between 3:1 and 1:3.

[0088] The carboxylate solvent includes any one of ethyl acetate, propyl acetate, methyl formate, methyl acetate, methyl butyrate, and ethyl propionate, or a combination of at least two thereof. The carbonate solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate, or a combination of at least two thereof.

[0089] It should be noted that polar organic solvents include carboxylate solvents and carbonate solvents, among which carboxylate solvents have stronger polarity, better dissolution effect on the first pore-forming agent and the second pore-forming agent, and higher dielectric constant, lower viscosity and lower freezing point, so it is beneficial to improve the ionic conductivity of the electrolyte at low temperature and the fast charging performance of the battery; in addition, carbonate solvents help to form a more stable SEI film, which is beneficial to improve the cycle performance of the battery.

[0090] Exemplarily, the aging treatment is a standing process after the electrolyte is injected into the battery, the standing time is 10h~96h, and the standing temperature is 30℃~70℃. Exemplarily, the standing time can be but not limited to 10h, 12h, 20h, 24h, 30h, 36h, 40h, 48h, 50h, 60h, 70h, 72h, 80h, 84h, 90h or 96h. The standing temperature can be but not limited to 30℃, 40℃, 50℃, 60℃, or 70℃.

[0091] The following are specific embodiments.

[0092] Example 1

[0093] Preparation of positive electrode for lithium-ion battery:

[0094] 96.7 wt% of active material lithium iron phosphate, 0.5 wt% of conductive agent carbon black, 0.5 wt% of conductive agent carbon nanotube, 0.5 wt% of binder sodium carboxymethyl cellulose, 1 wt% of first pore-forming agent polystyrene microspheres (0.1 μm particle size) and 0.8 wt% of second pore-forming agent fibrous poly (butyl acrylate-co-methyl methacrylate) (0.05 μm diameter, 2 μm length) were dispersed in deionized water to prepare positive electrode slurry, and the solid content in the positive electrode slurry was 60 wt%. Then the prepared positive electrode slurry was coated on the current collector aluminum foil and dried to form an active material layer on the current collector aluminum foil, and then the dried positive electrode sheet was rolled and cut and then vacuum dried at high temperature to obtain the positive electrode sheet, and the single-side surface density was 250 g / m 2 , single-sided thickness is 100 μm.

[0095] Preparation of negative electrode for lithium-ion battery:

[0096] 95.2 wt% of active material hard carbon, 0.5 wt% of conductive agent carbon black, 0.5 wt% of conductive agent carbon nanotubes, 2 wt% of binder polyacrylic acid, 1 wt% of first pore former polystyrene microspheres (0.1 μm particle size) and 0.8 wt% of second pore former poly(butyl acrylate-co-methyl methacrylate) fiber (0.05 μm diameter, 2 μm length) were dispersed in deionized water to prepare a negative electrode slurry, and the solid content in the slurry was 45 wt%. The negative electrode slurry was then coated on a current collector copper foil and dried. The dried negative electrode sheet was then rolled and cut and then vacuum dried at high temperature to obtain the negative electrode sheet, with a single-sided surface density of 110 g / m2 and a single-sided thickness of 70 μm.

[0097] Lithium-ion battery electrolyte

[0098] The invention comprises 30 wt% of ethylene carbonate, 20 wt% of diethyl carbonate, 25 wt% of ethyl acetate, 18 wt% of sodium perchlorate, 5 wt% of vinylene carbonate and 2 wt% of vinyl sulfate.

[0099] Preparation of lithium-ion batteries:

[0100] (1) Place the positive electrode sheet and separator (Celgard ® 2400) and the negative electrode sheet are stacked to obtain a pole core;

[0101] (2) placing the electrode core obtained in step (1) into a battery casing and encapsulating it to obtain a battery cell;

[0102] (3) Injecting electrolyte into the battery cell obtained in step (2), aging at 45° C. for 36 h, performing negative pressure formation, and then performing volume separation and coating to obtain a lithium-ion battery.

[0103] Example 2

[0104] The preparation method of Example 2 is substantially the same as that of Example 1, except that:

[0105] In the positive electrode active material layer, the first pore former is polyvinyl carbazole, and the second pore former is poly(styrene-co-methyl methacrylate). The diameter of the first pore former is 0.02 μm, and the second pore former is a tubular structure with an inner diameter of 0.05 μm, an outer diameter of 0.5 μm, and a length of 2 μm.

[0106] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 96.4%, 0.5%, 0.5%, 0.5%, 0.7% and 1.4%, respectively.

[0107] Example 3

[0108] The preparation method of Example 3 is substantially the same as that of Example 1, except that:

[0109] In the positive electrode active material layer, the first pore former is polyvinyl acetate and the second pore former is polymethyl methacrylate. The diameter of the first pore former is 0.5 μm, and the second pore former is a sheet structure with an inner diameter of 0.05 μm, a thickness of 0.05 μm and a perimeter of 2 μm.

[0110] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 96.5%, 0.5%, 0.5%, 0.5%, 0.5% and 1.5%, respectively.

[0111] Example 4

[0112] The preparation method of Example 4 is substantially the same as that of Example 1, except that:

[0113] In the positive electrode active material layer, the first pore former is polymethyl methacrylate, and the second pore former is polyvinyl acetate. The diameter of the first pore former is 1 μm, and the second pore former is a fiber structure with a diameter of 2 μm and a length of 200 μm.

[0114] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 97.4%, 0.5%, 0.5%, 0.5%, 0.2% and 0.9%, respectively.

[0115] Example 5

[0116] The preparation method of Example 5 is substantially the same as that of Example 1, except that:

[0117] In the positive electrode active material layer, the first pore former is poly(styrene-co-methyl methacrylate) and the second pore former is polyvinyl carbazole. The diameter of the first pore former is 1.5 μm, and the second pore former is a tubular structure with an inner diameter of 2 μm, an outer diameter of 3 μm, and a length of 200 μm.

[0118] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 97.1%, 0.5%, 0.5%, 0.5%, 0.2% and 1.2%, respectively.

[0119] Example 6

[0120] The preparation method of Example 6 is substantially the same as that of Example 1, except that:

[0121] In the positive electrode active material layer, the first pore former is poly(butyl acrylate-co-methyl methacrylate), and the second pore former is polystyrene. The diameter of the first pore former is 2 μm, and the second pore former is a sheet structure with a thickness of 0.5 μm and a perimeter of 500 μm.

[0122] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent, and the second pore-forming agent are 96.8%, 0.5%, 0.5%, 0.5%, 0.2%, and 1.5%, respectively.

[0123] Example 7

[0124] The preparation method of Example 7 is substantially the same as that of Example 1, except that Example 7 is a sodium ion battery, and the positive electrode active material of the sodium ion battery is O 3 -Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 2 (NNFM).

[0125] Example 8

[0126] The preparation method of Example 8 is substantially the same as that of Example 1, except that:

[0127] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 96.7%, 0.5%, 0.5%, 0.5%, 1.2% and 0.6%, respectively.

[0128] Example 9

[0129] The preparation method of Example 9 is substantially the same as that of Example 1, except that:

[0130] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 97.6%, 0.5%, 0.5%, 0.5%, 0.1% and 0.8%, respectively.

[0131] Example 10

[0132] The preparation method of Example 10 is substantially the same as that of Example 1, except that:

[0133] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 98.4%, 0.5%, 0.5%, 0.5%, 0.05% and 0.05%, respectively.

[0134] Embodiment 11

[0135] The preparation method of Example 11 is substantially the same as that of Example 1, except that:

[0136] In the positive electrode active material layer, the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, the first pore-forming agent and the second pore-forming agent are 95.3%, 0.5%, 0.5%, 0.5%, 1.6% and 1.6%, respectively.

[0137] Comparative Example 1

[0138] The preparation method of Comparative Example 1 is substantially the same as that of Example 1, except that:

[0139] The positive electrode active material layer does not contain the second pore-forming agent, and the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose and the first pore-forming agent are 97.5%, 0.5%, 0.5%, 0.5% and 1%, respectively.

[0140] Comparative Example 2

[0141] The preparation method of Comparative Example 2 is substantially the same as that of Example 1, except that:

[0142] The positive electrode active material layer does not contain the first pore-forming agent, and the mass contents of lithium iron phosphate, carbon black, carbon nanotubes, sodium carboxymethyl cellulose and the second pore-forming agent are 97.7%, 0.5%, 0.5%, 0.5% and 0.8% respectively.

[0143] Comparative Example 3

[0144] The preparation method of Comparative Example 3 is substantially the same as that of Example 1, except that:

[0145] The positive electrode active material layer does not contain the first pore-forming agent and the second pore-forming agent, and the mass contents of lithium iron phosphate, carbon black, carbon nanotubes and sodium carboxymethyl cellulose are 98.5%, 0.5%, 0.5% and 0.5% respectively.

[0146] The raw materials and process parameters in the preparation methods of Examples 1 to 11 and Comparative Examples 1 to 3 are listed in Table 1 below:

[0147] Table 1

[0148]

[0149] The electrode sheets or batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to performance tests, and the test results are shown in Table 2 below.

[0150] Among them, the test conditions or test standards for each performance test item are:

[0151] (1) Porosity of positive electrode sheet: The porosity of the electrode sheets prepared in the above embodiments and comparative examples was tested using a fully automatic porosity analyzer.

[0152] (2) Peel strength of positive electrode sheet: The positive electrode sheet samples prepared in the above-mentioned embodiments and comparative examples are fixed on a peel strength testing machine, and a tensile force perpendicular to the positive electrode sheet samples is applied. The magnitude of the tensile force can be adjusted as needed. As the tensile force increases, the positive electrode sheet samples begin to be subjected to the tensile force until peeling occurs. The peel strength value is measured by a force sensor.

[0153] (3) Charge transfer impedance of positive electrode sheet: The impedance of the electrode sheet prepared in the above embodiment and comparative example was tested using a button half-cell. The electrode sheet prepared in the above embodiment and comparative example and a lithium sheet were assembled into a button half-cell. After three cycles of charge and discharge at a current density of 100 mA / g in the voltage range of 2.5V to 3.65 V, the electrochemical AC impedance was tested in an empty state. The charge transfer impedance of the positive electrode sheet was obtained by fitting the equivalent circuit. The electrochemical AC impedance was tested using an electrochemical workstation, with a perturbed AC signal of 5 mV and a frequency range of 0.01 Hz to 10 kHz.

[0154] (4) Gram capacity of active material in positive electrode sheet: The gram capacity of active material in the electrode sheets prepared in the above embodiments and comparative examples was tested using a button half-cell. The electrode sheets prepared in the above embodiments and comparative examples and a lithium sheet were assembled into a button half-cell. The cells were charged and discharged for three cycles at a current density of 50 mA / g in a voltage range of 2.5 V to 3.65 V. The gram capacity of active material in the electrode sheets was calculated by dividing the average of the three discharge capacities by the mass of the active material.

[0155] (5) 1C discharge capacity of secondary battery: At 25°C, the secondary batteries prepared in the above embodiments and comparative examples were charged at 0.5 C constant current to 3.65 V, then charged at constant voltage until the charge termination current dropped to 0.05 C, and then stopped charging and left for 30 min. They were discharged at 1 C current to 2.5 V for three cycles, and the average of the three discharge capacities was taken as the discharge capacity of the secondary batteries prepared in the above embodiments and comparative examples.

[0156] (6) Cycle performance of secondary batteries: After 500 charge and discharge cycles of the secondary batteries prepared in the above examples and comparative examples according to the steps of 1C discharge capacity test at 25°C, the capacity retention rate was obtained by calculating the ratio of the discharge capacity before and after the cycle.

[0157] (7) Internal resistance of secondary batteries: The secondary batteries prepared in the above examples and comparative examples were first charged to 3.18 V, and then the internal resistance of the secondary batteries was tested using a voltage internal resistance meter.

[0158] According to the above test methods, the porosity, peel strength, charge transfer impedance and gram capacity of the positive electrode sheets provided in Examples 1 to 11 and Comparative Examples 1 to 3 were tested, and the internal resistance, 1C discharge capacity and cycle performance of the assembled secondary battery were tested. The test results are shown in Table 2:

[0159] Table 2

[0160]

[0161] It can be seen from the data in Table 2 that the electrode plate provided by the present invention exhibits excellent structural strength, and the secondary battery prepared from the electrode plate exhibits excellent electrochemical performance.

[0162] Specifically, compared with the comparative example, the lithium ion batteries provided in Examples 1 to 6 and the sodium ion batteries provided in Example 7 all use an appropriate amount of the first pore-forming agent and the second pore-forming agent, and the second pore-forming agent is any one of a fibrous, tubular, and sheet-like morphology, and is used in combination with the first pore-forming agent of a spherical morphology, so that a good three-dimensional mesh pore structure can be formed inside the electrode plate, thereby reducing the charge transfer impedance of the electrode plate and exerting a relatively high active material gram capacity; in addition, the use amount of the first pore-forming agent and the second pore-forming agent is within an appropriate range, which will not destroy the structural integrity of the electrode and reduce the peel strength. The lithium ion battery and the sodium ion battery prepared in this way both exhibit excellent electrochemical performance, and have excellent rate performance and cycle performance.

[0163] In Example 8, the mass ratio of the second pore former to the first pore former is too low, so that the three-dimensional pore structure formed is not good enough. On the one hand, it will cause the porosity of the electrode sheet to decrease, the charge transfer impedance to increase, the gram capacity to decrease, and the internal resistance of the battery to increase. On the other hand, it cannot provide sufficient ion diffusion channels, which will affect the rate performance and electrochemical properties such as charge and discharge cycles of the battery using the electrode sheet. In Example 9, the mass ratio of the second pore former to the first pore former is too high, so that the three-dimensional pore structure formed is not stable enough. On the one hand, it will cause the porosity of the electrode sheet to decrease, the charge transfer impedance to increase, the gram capacity to decrease, and the internal resistance of the battery to increase. On the other hand, it will cause the structural integrity and stability of the electrode sheet to decrease and affect the cycle stability of the battery using the electrode sheet.

[0164] In Example 10, the total amount of the first pore former and the second pore former is too low, so that the three-dimensional pore structure formed is not good enough. On the one hand, it will cause the porosity of the electrode plate to decrease, the charge transfer impedance to increase, the specific capacity to decrease, and the internal resistance of the battery to increase. On the other hand, it is not conducive to the effective infiltration of the electrolyte into the electrode plate, and thus the electrochemical performance of the battery using the electrode plate cannot be effectively improved. In Example 11, the total amount of the first pore former and the second pore former is too high. On the one hand, it will cause the porosity of the electrode plate to be too high, thereby reducing the structural strength of the electrode plate. On the other hand, it will cause the active material content in the electrode plate to decrease, thereby reducing the specific capacity of the electrode plate and reducing the electrochemical performance of the battery such as the rate performance and charge-discharge cycle.

[0165] Comparative Examples 1 and 2 respectively use only the first pore former and the second pore former, and respectively have only zero-dimensional pores formed by the first pore former and one-dimensional and / or two-dimensional pores formed by the second pore former, the porosity of the electrode sheet is lower, the charge transfer impedance is further increased, and the gram capacity of the active material is further reduced, and the electrochemical performance of the lithium ion battery prepared thereby is further reduced. Comparative Example 3 does not use any pore former at all, and an effective pore structure cannot be formed, and the performance of the electrode sheet and the electrochemical performance of the lithium ion battery prepared thereby are even worse than those of Comparative Examples 1 and 2.

[0166] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0167] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electrode plate, characterized in that: The electrode plate includes a current collector layer, an active material layer is formed on at least one side of the current collector layer, the active material layer includes an active material, a conductive agent, a binder, a first pore former and a second pore former, the first pore former and the second pore former are both soluble in polar organic solvents, the first pore former and the second pore former are both high molecular polymers, the first pore former is granular, and the second pore former is one or more combinations of fibrous, tubular, and sheet-like.

2. The electrode plate according to claim 1, characterized in that: The active material layer includes, by mass percentage, 94% to 99% of active material, 0.2% to 3% of conductive agent, 0.2% to 3% of binder, 0.05% to 2% of first pore former and 0.05% to 2% of second pore former; wherein the sum of the mass of the first pore former and the second pore former accounts for 0.2% to 3% of the mass percentage of the active material layer.

3. The electrode plate according to claim 2, characterized in that: The mass ratio of the second pore-forming agent to the first pore-forming agent is (0.8-7.5):

1.

4. The electrode plate according to claim 1, characterized in that: The first pore-forming agent and / or the second pore-forming agent include at least one of a homopolymer of ethylene monosubstituted, a homopolymer of ethylene 1,1-disubstituted, a copolymer of ethylene monosubstituted, a copolymer of ethylene 1,1-disubstituted, and a copolymer of ethylene monosubstituted and ethylene 1,1-disubstituted.

5. The electrode plate according to claim 4, characterized in that: The homopolymer of the ethylene monosubstituted product includes at least one of polystyrene, polyvinyl carbazole, polyvinyl acetate, polymethyl acrylate, and polybutyl acrylate; and / or, The homopolymer of ethylene 1,1-disubstituted product includes at least one of polymethyl methacrylate, polylauryl methacrylate, polybutyl methacrylate and poly-α-methylstyrene; and / or, The copolymer of the ethylene monosubstituted product includes at least one of poly(styrene-co-vinyl carbazole), poly(styrene-co-vinyl acetate), poly(styrene-co-methyl acrylate), poly(styrene-co-butyl acrylate), poly(vinyl carbazole-co-vinyl acetate), poly(vinyl carbazole-co-methyl acrylate), poly(vinyl carbazole-co-butyl acrylate), poly(vinyl acetate-co-methyl acrylate), and poly(vinyl acetate-co-butyl acrylate); and / or, The copolymer of 1,1-disubstituted ethylene includes at least one of poly(methyl methacrylate-co-lauryl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(methyl methacrylate-co-α-methylstyrene), poly(lauryl methacrylate-co-butyl methacrylate), poly(lauryl methacrylate-co-α-methylstyrene), poly(butyl methacrylate-co-α-methylstyrene); and / or The copolymer of ethylene monosubstituted product and ethylene 1,1-disubstituted product includes at least one of poly(styrene-co-methyl methacrylate), poly(methyl acrylate-co-methyl methacrylate), and poly(butyl acrylate-co-methyl methacrylate).

6. The electrode plate according to claim 1, characterized in that: The particle size of the first pore-forming agent is 0.02 μm to 2 μm.

7. The electrode plate according to claim 1, characterized in that: The second pore-forming agent satisfies at least one of the following (1) to (3): (1) The diameter of the fiber is 0.02 μm~2 μm, and the length is 2 μm~200 μm; (2) The inner diameter of the tubular tube is 0.02 μm~2 μm, the outer diameter is 0.03 μm~3 μm, and the length is 2 μm~200 μm; (3) The thickness of the sheet is 0.01μm~0.5μm, and the circumference is 1μm~500μm.

8. The electrode plate according to claim 1, characterized in that: The single surface density of the active material layer is 100 g / m 2 ~300 g / m 2 and / or, The single-side thickness of the active material layer is 70 μm to 400 μm.

9. A method for preparing an electrode sheet according to any one of claims 1 to 8, characterized in that: The following steps are involved: Applying electrode slurry on the current collector layer to obtain an intermediate; the electrode slurry includes an active material, a conductive agent, a binder, a first solvent, a first pore-forming agent and a second pore-forming agent; The intermediate is dried, pressed and cut to obtain electrode plates.

10. A battery, characterized in that: The battery precursor is obtained by aging treatment, wherein the battery precursor comprises the electrode plate according to any one of claims 1 to 8 and an electrolyte, wherein the electrolyte comprises a polar organic solvent; The polar organic solvent includes carboxylate solvents and carbonate solvents.

Images