Lithium ion battery, positive plate and preparation method of positive plate
By using conductive carbon black and adding solvents and positive electrode active materials multiple times, combined with the stirring technology of a planetary mixer, the problem of high cost and uneven dispersion of carbon nanotubes in the positive electrode sheet of lithium-ion battery is solved, and efficient electrochemistry is achieved Performance and stability reduce production costs.
Patent Information
- Application Number
- CN202411377090.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2025-01-07
AI Technical Summary
The application of carbon nanotubes in lithium-ion battery cathode sheets has problems of high cost and uneven dispersion, resulting in insufficient electrochemical performance and stability.
Conductive carbon black is used as a substitute material, and by adding solvent and positive electrode active material multiple times, combined with high-speed and slow stirring of a planetary mixer, uniform positive electrode slurry is prepared, which improves the degree of dispersion and stability and reduces production costs.
It achieves better electrochemical performance and stability, reduces production costs, avoids the problem of difficult carbon nanotubes being mixed with other materials, and improves electrical conductivity.
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Figure CN119275244A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present application relate to the technical field of lithium-ion batteries, and specifically to a lithium-ion battery, a positive electrode sheet, and a method for preparing the same. Background Art
[0002] Since carbon nanotubes have good electrical conductivity, they are usually selected as binders in positive electrode slurries to make the prepared positive electrode sheets have better electrochemical properties. However, due to the time-consuming and energy-consuming production process, the actual application cost of carbon nanotubes is relatively high.
[0003] In addition, due to the high surface energy of carbon nanotubes, carbon nanotubes are prone to agglomeration, resulting in uneven dispersion and difficulty in mixing with other materials.
[0004] Therefore, the present application proposes a method for preparing a positive electrode sheet that replaces carbon nanotubes to avoid the problems caused by using carbon nanotubes as a binder. Summary of the invention
[0005] The present application provides a lithium ion battery, a positive electrode sheet and a preparation method thereof, which can reduce the production and processing costs of the positive electrode sheet.
[0006] In a first aspect, the present application provides a method for preparing a positive electrode sheet, comprising the steps of:
[0007] The binder, dispersant and conductive agent are stirred uniformly to prepare a mixture.
[0008] A first portion of the solvent is added to the mixture and stirred to obtain a first slurry.
[0009] The first part of the positive electrode active material and the second part of the solvent are added to the first slurry, and stirred evenly to prepare the second slurry.
[0010] The second portion of the positive electrode active material is added to the second slurry and stirred evenly to obtain a third slurry.
[0011] The third slurry is added into a planetary mixer and stirred at high speed for 150 to 250 minutes to obtain a fourth slurry.
[0012] The fourth slurry was added into a planetary mixer and stirred at a slow speed to obtain a positive electrode slurry.
[0013] The positive electrode slurry is evenly coated on the surface of the current collector and dried to obtain a positive electrode sheet.
[0014] Among them, the conductive agent is conductive carbon black, the solid content of the electrode slurry is 70% to 71%, and the mass proportion of the conductive carbon black in the electrode slurry is 1 to 2%.
[0015] Through the above scheme, the above-mentioned method of adding solvent and positive electrode active material in batches can make the substances in the positive electrode slurry stir evenly in multiple times, reduce the workload and the difficulty of stirring evenly each time, thereby improving the dispersion degree of each substance in the positive electrode slurry, so that the positive electrode sheet has good electrochemical performance and stability. Among them, the method of adding solvent multiple times can also make the processing material more fully dissolved in the solvent, reduce processing loss, reduce the resistance of stirring, reduce the difficulty of stirring processing, and improve the utilization rate of processing materials, so as to reduce the production and processing cost of the positive electrode sheet to a certain extent. The stirring uniformity of the slurry is closely related to the stirring speed and time. Generally speaking, the higher the stirring speed and the longer the stirring time, the better the stirring uniformity of the slurry. Therefore, stirring the third slurry at a high speed for a long time can further improve the stirring uniformity of the positive electrode slurry to improve the dispersion degree of each substance in the positive electrode slurry. In addition, compared with carbon nanotubes, the conductivity of conductive carbon black is poor. The above-mentioned preparation method can improve the conductivity of the positive electrode sheet by increasing the uniform dispersibility of the positive electrode slurry to compensate for the problem of conductivity loss caused by conductive carbon black.
[0016] In a possible design, the stirring time of the binder, dispersant and conductive agent is 200 to 300 minutes.
[0017] Through the above scheme, a longer stirring time can make the binder, dispersant and conductive agent dispersed more evenly in the solvent, so that the first slurry has better uniformity. The uniformly dispersed binder can make the coating of the positive electrode slurry have better peel strength and structural stability, so that the positive electrode sheet has better stability.
[0018] In a possible design, the rotation speed of the planetary mixer during high-speed stirring is 1500-2000 rpm, and the rotation speed of the planetary mixer during slow-speed stirring is 400 rpm-600 rpm.
[0019] In a possible design, the mass ratio of the first portion of the positive electrode active material to the second portion of the positive electrode active material is (40-60):(40-60).
[0020] Through the above scheme, the mass ratio of the first part of the positive electrode active material and the second positive electrode active material is close to 1, that is, the added amount of the first part of the positive electrode active material and the second positive electrode active material is relatively close. This method can facilitate stirring when the positive electrode active material is mixed with other materials, and avoids adding too much positive electrode active material at one time, resulting in poor stirring and mixing effect.
[0021] In a possible design, the mass ratio of the first part of the solvent to the second part of the solvent is (50-70):(30-50).
[0022] According to the above scheme, since the first part of the solvent needs to dissolve more substances, appropriately increasing the amount of the first part of the solvent added can improve the dissolving effect of the solvent, so as to facilitate the stirring process of the slurry.
[0023] In a possible design, the mass proportion of the positive electrode active material in the electrode slurry is 96-97%, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, a ternary positive electrode material and lithium iron phosphate.
[0024] Through the above scheme, the main role of the positive electrode active material is to provide the electrochemical properties required by the positive electrode material, including the insertion and deinsertion of lithium ions, so as to realize the charging and discharging process of the battery. The positive electrode active material determines the key performance parameters of the battery, such as the energy density, voltage platform, and charge and discharge cycle life.
[0025] In a possible design, the binder accounts for 1-2% by mass in the electrode slurry, and the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and polyimide.
[0026] Through the above scheme, the main function of the binder is to bond the positive electrode active material, the conductive agent and the current collector together to form a solid electrode structure so that the positive electrode sheet has better stability.
[0027] In a possible design, the mass proportion of the dispersant in the electrode slurry is 0.05-0.1%, and the dispersant includes at least one of polyvinyl alcohol, polyacrylic acid, sulfonate, and sulfate.
[0028] Through the above scheme, the main role of the dispersant in the positive electrode slurry is to improve the dispersibility of each substance in the slurry, prevent particle agglomeration, and ensure the uniformity and stability of the slurry. Specifically, due to the high surface energy of some substances in the positive electrode slurry, agglomeration is prone to occur, which will affect the performance of the positive electrode sheet. The addition of the dispersant can effectively reduce the surface tension between the active material particles, improve their dispersibility in the solvent, and thus avoid particle agglomeration.
[0029] In a second aspect, the present application also provides a positive electrode sheet, which is prepared by the preparation method of the first aspect.
[0030] The beneficial effects of the positive electrode sheet provided in the above second aspect and each possible design of the above second aspect can refer to the beneficial effects brought about by the above first aspect and each possible implementation method of the first aspect, and will not be repeated here.
[0031] In a third aspect, the present application further provides a lithium-ion battery, comprising a negative electrode sheet, a separator and the positive electrode sheet of the second aspect.
[0032] The beneficial effects of the lithium-ion battery provided in the third aspect and each possible design of the third aspect can be referred to the beneficial effects brought about by the first aspect and each possible implementation method of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 A scanning electron microscope schematic diagram of a cathode slurry at a scale provided in an embodiment of the present application.
[0034] Figure 2 A scanning electron microscope schematic diagram of the positive electrode slurry at another scale provided in an embodiment of the present application.
[0035] Figure 3 A scanning electron microscope schematic diagram of the positive electrode slurry at another scale provided in an embodiment of the present application.
[0036] Figure 4 A scanning electron microscope schematic diagram of the positive electrode slurry at another scale provided in an embodiment of the present application. DETAILED DESCRIPTION
[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.
[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0040] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.
[0041] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the current limiting module of the present application. For example, in the description of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.
[0042] In addition, the terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.
[0043] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).
[0044] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure can refer to a physical connection. For example, the physical connection can be a fixed connection, such as a fixed connection through a barrier, such as a fixed connection through a screw, bolt or other barrier; the physical connection can also be a detachable connection, such as a mutual snap connection or snap connection; the physical connection can also be an integral connection, such as welding, bonding or integral molding to form a connection for connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. The "connection" or "connection" of a circuit structure can refer to not only a physical connection, but also an electrical connection or a signal connection. For example, it can be a direct connection, that is, a physical connection, or it can be indirectly connected through at least one intermediate element, as long as the circuit is connected, and it can also be the internal connection of two elements; the signal connection can refer to a signal connection through a media medium, such as a radio wave, in addition to a signal connection through a circuit. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0045] The present application discloses a bare cell, a battery cell and an electric device, wherein the battery cell includes the bare cell, the electric device includes the battery cell, and can be provided with electric energy by the battery cell. The electric device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, an energy storage device, an amusement device, an elevator and a lifting device, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. The spacecraft may include an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy or an electric airplane toy, etc. The electric tool may include a metal cutting electric tool, a grinding electric tool, an assembly electric tool and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The energy storage device may be an energy storage wall, a base station energy storage, a container energy storage, etc. The amusement device may be a carousel, a jumping machine, etc. This application does not impose any special restrictions on the above-mentioned electrical equipment.
[0046] For new energy vehicles, the above-mentioned battery cells can be used as driving power sources, thereby replacing fossil fuels to provide driving power.
[0047] Generally, a battery cell includes a battery casing and a bare cell, and the bare cell is contained in the battery casing. The bare cell is the smallest unit in the battery that performs electrochemical reactions and realizes the charging and discharging of the battery cell. It usually includes a positive electrode sheet, a negative electrode sheet, and a diaphragm that separates the positive electrode sheet from the negative electrode sheet. The battery casing is injected with an electrolyte, which can infiltrate the inside of the bare cell, providing an ion migration path for the bare cell to perform electrochemical reactions and playing a conductive role.
[0048] The present application provides a method for preparing a positive electrode sheet, comprising the steps of:
[0049] The binder, dispersant and conductive agent are stirred uniformly to prepare a mixture.
[0050] A first portion of the solvent is added to the mixture and stirred to obtain a first slurry.
[0051] The first part of the positive electrode active material and the second part of the solvent are added to the first slurry, and stirred evenly to prepare the second slurry.
[0052] The second portion of the positive electrode active material is added to the second slurry and stirred evenly to obtain a third slurry.
[0053] The third slurry is added into a planetary mixer and stirred at high speed for 150 to 250 minutes to obtain a fourth slurry.
[0054] The fourth slurry was added into a planetary mixer and stirred at a slow speed to obtain a positive electrode slurry.
[0055] The positive electrode slurry is evenly coated on the surface of the current collector and dried to obtain a positive electrode sheet.
[0056] Among them, the conductive agent is conductive carbon black, the solid content of the electrode slurry is 70% to 71%, and the mass proportion of the conductive carbon black in the electrode slurry is 1 to 2%.
[0057] The production and processing cost of the positive electrode sheet can be reduced by using conductive carbon black, which has a lower application cost, instead of carbon nanotubes. In addition, conductive carbon black has good dispersibility and is easy to mix with other materials, thus avoiding the problem that carbon nanotubes are difficult to mix with other materials.
[0058] , firstly, part of the solvent is stirred evenly with the mixture to form a first slurry with uniform dispersion, then part of the positive electrode active material, the first slurry and the remaining solvent are stirred evenly to obtain a second slurry, and finally the remaining positive electrode active material is added to the second slurry and stirred evenly. The above-mentioned method of adding the solvent and the positive electrode active material in batches can make the substances in the positive electrode slurry be stirred evenly in multiple batches, reducing the workload and difficulty of stirring evenly each time, thereby improving the dispersion degree of each substance in the positive electrode slurry, so that the positive electrode sheet has better electrochemical performance and stability.
[0059] Among them, the method of adding solvent multiple times can also make the processing materials more fully dissolved in the solvent, reduce processing losses, reduce stirring resistance, thereby reducing the difficulty of stirring processing and improving the utilization rate of processing materials, thereby reducing the production and processing costs of positive electrode sheets to a certain extent.
[0060] The stirring uniformity of the slurry is closely related to the stirring speed and time. Generally speaking, the higher the stirring speed and the longer the stirring time, the better the stirring uniformity of the slurry. Therefore, stirring the third slurry at a high speed for a longer time can further improve the stirring uniformity of the positive electrode slurry, thereby improving the dispersion of various substances in the positive electrode slurry.
[0061] In addition, compared with carbon nanotubes, the conductivity of conductive carbon black is poor. The above preparation method can improve the conductivity of the positive electrode sheet by increasing the uniform dispersion of the positive electrode slurry to compensate for the conductivity loss caused by the conductive carbon black.
[0062] Optionally, the stirring time of the binder, dispersant and conductive agent is 200 to 300 minutes.
[0063] A longer stirring time can make the binder, dispersant and conductive agent dispersed more evenly in the solvent, so that the first slurry has better uniformity. The evenly dispersed binder can make the coating of the positive electrode slurry have better peel strength and structural stability, so that the positive electrode sheet has better stability.
[0064] Specifically, the stirring time of the binder, dispersant and conductive agent can be 200 min, 210 min, 220 min, 230 min, 240 min, 250 min, 260 min, 270 min, 280 min, 290 min, 300 min, etc.
[0065] Optionally, the rotation speed of the planetary mixer during high-speed stirring is 1500-2000 rpm, and the rotation speed of the planetary mixer during slow stirring is 400 rpm-600 rpm.
[0066] Specifically, the rotation speed of the planetary mixer during high-speed stirring can be 1500rpm, 1550rpm, 1600rpm, 1650rpm, 1700rpm, 1750rpm, 1800rpm, 1850rpm, 1900rpm, 1950rpm, 2000rpm, etc.
[0067] Specifically, the rotation speed of the planetary mixer during slow stirring can be 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc.
[0068] Optionally, the mass ratio of the first portion of the positive electrode active material to the second portion of the positive electrode active material is (40-60):(40-60).
[0069] The mass ratio of the first part of the positive electrode active material and the second positive electrode active material is close to 1, that is, the added amount of the first part of the positive electrode active material and the second positive electrode active material is relatively close. This method can facilitate stirring when the positive electrode active material is mixed with other materials, and avoids adding too much positive electrode active material at one time, resulting in poor stirring and mixing effect.
[0070] Optionally, the mass ratio of the first part of the solvent to the second part of the solvent is (50-70):(30-50).
[0071] Since the solvent needs to dissolve more substances in the early stage, appropriately increasing the amount of solvent added can improve the dissolution effect of the solvent, so as to facilitate the stirring process of the slurry.
[0072] Optionally, the mass proportion of the positive electrode active material in the electrode slurry is 96-97%, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, a ternary positive electrode material and lithium iron phosphate.
[0073] The main function of the positive electrode active material is to provide the electrochemical properties required by the positive electrode material, including the insertion and deinsertion of lithium ions, so as to realize the charging and discharging process of the battery. The positive electrode active material determines the key performance parameters of the battery, such as the energy density, voltage platform, and charge and discharge cycle life.
[0074] Specifically, the mass proportion of the positive electrode active material in the electrode slurry can be 96%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, 96.6%, 96.7%, 96.8%, 96.9%, and 97%.
[0075] Optionally, the binder accounts for 1-2% by mass in the electrode slurry, and the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and polyimide.
[0076] The main function of the binder is to bond the positive electrode active material, conductive agent and current collector together to form a solid electrode structure so that the positive electrode sheet has better stability.
[0077] Specifically, the mass proportion of the binder in the electrode slurry can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.
[0078] Optionally, the mass proportion of the dispersant in the electrode slurry is 0.05-0.1%, and the dispersant includes at least one of polyvinyl alcohol, polyacrylic acid, sulfonate, and sulfate.
[0079] The main function of the dispersant in the positive electrode slurry is to improve the dispersibility of various substances in the slurry, prevent particle agglomeration, and ensure the uniformity and stability of the slurry. Specifically, since some substances in the positive electrode slurry have high surface energy, agglomeration is prone to occur, which will affect the performance of the positive electrode sheet. The addition of dispersants can effectively reduce the surface tension between active material particles, improve their dispersibility in the solvent, and thus avoid particle agglomeration.
[0080] Specifically, the mass proportion of the dispersant in the electrode slurry may be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.
[0081] The present application also provides a positive electrode sheet, which is prepared using the above-mentioned preparation method.
[0082] The present invention is described in detail below through specific examples. The examples are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.
[0083] Example 1
[0084] 1. Preparation of positive electrode
[0085] 1.1 The binder, dispersant and conductive agent are stirred evenly to obtain a mixture, wherein the stirring time is 250 minutes.
[0086] 1.2 Add the first part of solvent into the mixture and stir evenly to obtain the first slurry.
[0087] 1.3 Add the first part of the positive electrode active material and the second part of the solvent into the first slurry and stir evenly to prepare the second slurry.
[0088] 1.4 Add the second portion of positive electrode active material to the second slurry and stir evenly to obtain a third slurry.
[0089] 1.5 Add the third slurry into a planetary mixer and stir at high speed for 200 min to obtain a fourth slurry. The rotation speed of the planetary mixer is 1750 rpm.
[0090] 1.6 Add the fourth slurry into the planetary mixer and stir slowly to obtain the positive electrode slurry. The rotation speed of the planetary mixer is 500 rpm.
[0091] 1.7 The positive electrode slurry is evenly coated on the surface of the current collector and dried to obtain a positive electrode sheet.
[0092] Among them, the binder is polyvinylidene fluoride, the dispersant is polyvinyl alcohol, and the conductive agent is conductive carbon black. The positive electrode active material is a ternary positive electrode material, and the mass ratio of the first part of the positive electrode active material to the second part of the positive electrode active material is 50:50. The solvent is N-methylpyrrolidone, and the mass ratio of the first part of the solvent to the second part of the solvent is 60:40. The solid content of the electrode slurry is 70.5%, the mass proportion of conductive carbon black in the electrode slurry is 1.5%, the mass proportion of the positive electrode active material in the electrode slurry is 96.9%, the mass proportion of the binder in the electrode slurry is 1.5%, and the mass proportion of the dispersant in the electrode slurry is 0.1%.
[0093] Comparative Example 1
[0094] 1. Preparation of positive electrode
[0095] 1.1 The positive electrode active material, the binder and the conductive agent are stirred evenly to obtain a mixture, wherein the stirring time is 15 minutes.
[0096] 1.2 Add the solvent to the mixture and stir evenly to obtain the first slurry, wherein the stirring time is 30 minutes.
[0097] 1.3 Add the first slurry into a planetary mixer and stir at high speed for 140 minutes to obtain a fourth slurry. The rotation speed of the planetary mixer is 2000 rpm.
[0098] 1.6 Add the fourth slurry into the planetary mixer and stir slowly to obtain the positive electrode slurry. The rotation speed of the planetary mixer is 600 rpm.
[0099] 1.7 The positive electrode slurry is evenly coated on the surface of the current collector and dried to obtain a positive electrode sheet.
[0100] Among them, the binder is polyvinylidene fluoride, the conductive agent is carbon nanotubes, the positive electrode active material is a ternary positive electrode material, and the solvent is N-methylpyrrolidone. The solid content of the electrode slurry is 70.5%, the mass proportion of the conductive agent in the electrode slurry is 1.5%, the mass proportion of the positive electrode active material in the electrode slurry is 97%, and the mass proportion of the binder in the electrode slurry is 1.5%.
[0101] The performance of the positive electrode is tested using the following method:
[0102] (1) Peel force test: The positive electrode sheet was cut into strips of not less than 50 cm × 50 cm in size, the strips were peeled off using 3M tape, and the peel force was measured using a force sensor with a range of 20 N and 1000 N.
[0103] (2) Electrode resistance test: Use the tester to connect the sample in series with an equivalent analog circuit, and measure the resistance by applying a certain voltage. Specifically, the size of the sample must be no less than 10cm×10cm, the impedance range is 0.1uΩ~3kΩ, and the resolution is 0.1uΩ.
[0104] The performance test results of the positive electrode sheets prepared in Example 1 and Comparative Example 1 are summarized in Table 1.
[0105] Table 1
[0106]
[0107] As can be seen from Table 1, the performance of the positive electrode sheet prepared in Example 1 and the positive electrode sheet prepared in Comparative Example 1 are relatively close. Among them, the test results of the electrode sheet resistance test show that the preparation method of the present application can improve the conductivity of the positive electrode sheet to make up for the lack of conductivity of the conductive carbon black. The test results of the peeling force show that the preparation method of the present application can make the positive electrode sheet have good structural strength and stability.
[0108] Figure 1 A schematic diagram of a scanning electron microscope of a cathode slurry at a certain scale provided in an embodiment of the present application. Figure 2 A schematic diagram of a scanning electron microscope of a positive electrode slurry at another scale provided in an embodiment of the present application, Figure 3 A schematic diagram of a scanning electron microscope of a positive electrode slurry at another scale provided in an embodiment of the present application, Figure 4A scanning electron microscope schematic diagram of the positive electrode slurry at another scale provided in an embodiment of the present application.
[0109] In addition, see Figures 1 to 4 The positive electrode slurry prepared by the preparation method of the present application has good uniformity, which can make the positive electrode sheet have good electrochemical performance.
[0110] In summary, the positive electrode sheet prepared by the preparation method of the present application has good performance and can replace the positive electrode sheet using carbon nanotubes as a binder.
Claims
1. A method for preparing a positive electrode sheet, characterized in that: Includes steps: The binder, the dispersant and the conductive agent are stirred uniformly to obtain a mixture; Adding the first portion of solvent into the mixture and stirring evenly to obtain a first slurry; Adding a first portion of the positive electrode active material and a second portion of the solvent to the first slurry and stirring them uniformly to obtain a second slurry; Adding the second portion of the positive electrode active material to the second slurry and stirring evenly to obtain a third slurry; Add the third slurry into a planetary mixer and stir at high speed for 150 to 250 minutes to obtain a fourth slurry; Add the fourth slurry into a planetary mixer and stir slowly to prepare a positive electrode slurry; The positive electrode slurry is evenly coated on the surface of the current collector, and after drying, a positive electrode sheet is obtained; Wherein, the conductive agent is conductive carbon black, the solid content of the electrode slurry is 70% to 71%, and the mass proportion of the conductive carbon black in the electrode slurry is 1 to 2%.
2. The preparation method according to claim 1, characterized in that: The stirring time of the binder, dispersant and conductive agent is 200 to 300 minutes.
3. The preparation method according to claim 1, characterized in that: The rotation speed of the planetary mixer during high-speed stirring is 1500-2000 rpm, and the rotation speed of the planetary mixer during slow stirring is 400-600 rpm.
4. The preparation method according to claim 1, characterized in that: The mass ratio of the first portion of positive electrode active material to the second portion of positive electrode active material is (40-60):(40-60).
5. The preparation method according to claim 1, characterized in that: The mass ratio of the first part of solvent to the second part of solvent is (50-70):(30-50).
6. The preparation method according to claims 1 to 5, characterized in that: The positive electrode active material accounts for 96-97% of the mass of the electrode slurry, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, a ternary positive electrode material and lithium iron phosphate.
7. The preparation method according to claims 1 to 5, characterized in that: The binder accounts for 1-2% by weight of the electrode slurry, and the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and polyimide.
8. The preparation method according to claims 1 to 5, characterized in that: The mass proportion of the dispersant in the electrode slurry is 0.05-0.1%, and the dispersant includes at least one of polyvinyl alcohol, polyacrylic acid, sulfonate, and sulfate.
9. A positive electrode sheet, characterized in that: The method is prepared according to any one of claims 1 to 8.
10. A lithium ion battery, characterized in that: The invention comprises a negative electrode sheet, a separator and the positive electrode sheet as claimed in claim 9.