Electrode plate, lithium ion battery, and preparation method and equipment of electrode plate

Abstract

The embodiment of the invention provides an electrode plate, a lithium ion battery, and a preparation method and equipment of the electrode plate. The electrode plate comprises a current collecting layer, an active material layer and a hydrophobic layer which are arranged in sequence, the active material layer comprises an electrode active material, and the active material layer is located on the current collecting layer; the hydrophobic layer comprises a hydrophobic material, and the hydrophobic layer is located on the active material layer, so that the electrode pole piece can effectively control the invasion of moisture outside the battery, the increase of the moisture content of the electrode active material is avoided, and the performance of the battery is ensured. Furthermore, the hydrophobic layer is low in preparation cost and simple in preparation process; the hydrophobic material is arranged on the surface of the active material layer, does not influence the property of the active material of the positive electrode, and has low influence on the overall energy density of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to an electrode sheet, a lithium-ion battery, and a method and apparatus for preparing the electrode sheet. Background Technology

[0002] Lithium-ion batteries contain LMFP (Lithium Metal Fluorophosphate) as an electrode active material, which can improve the intercalation and deintercalation capabilities of lithium ions, while also exhibiting good thermal stability, cycle stability, and electrochemical properties, thus significantly enhancing the performance of lithium-ion batteries. However, this material still faces some challenges in practical applications. For example, it is quite sensitive to moisture; when the moisture content of LMFP is high, it can cause severe failure phenomena such as reduced coulombic efficiency, severe gas generation, and cycle failure. Current technologies typically involve preparing hydrophobic materials into a slurry and then combining it with the battery's electrode active material to optimize the battery's hydrophobic properties. However, this method involves high slurry costs, complex preparation processes, and long preparation cycles; slurry composites can also affect the properties of the electrode active material and increase the battery's dead weight, thus reducing the battery's energy density. Summary of the Invention

[0003] To address the aforementioned problems, embodiments of the present invention disclose an electrode sheet, a lithium-ion battery, and a method and apparatus for preparing the electrode sheet.

[0004] In a first aspect, embodiments of the present invention provide an electrode sheet, the electrode sheet comprising a current collecting layer, an active material layer and a hydrophobic layer arranged sequentially;

[0005] The active material layer comprises an electrode active material, and the active material layer is located on the current collector layer;

[0006] The hydrophobic layer comprises a hydrophobic material and is located on the active material layer.

[0007] Optionally, the areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

[0008] Optionally, the thickness of the hydrophobic layer is 2.9 μm-3.1 μm.

[0009] Optionally, the water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

[0010] Optionally, the hydrophobic material in the hydrophobic layer is at least partially infiltrated into the surface of the active material layer.

[0011] Optionally, the hydrophobic layer is at least partially dissolved in the electrolyte.

[0012] Optionally, the active material layer is formed in an environment with a dew point temperature of less than -40 degrees Celsius.

[0013] Optionally, the electrode active material includes lithium manganese iron phosphate.

[0014] Optionally, the hydrophobic material includes one of 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

[0015] Secondly, embodiments of the present invention provide a lithium-ion battery, the lithium-ion battery including the electrode plates described above.

[0016] Optionally, it also includes an electrolyte in which the hydrophobic layer is at least partially dissolved.

[0017] Optionally, the content of hydrophobic material in the electrode sheet is greater than 5 times the content of hydrophobic material in the electrolyte.

[0018] Thirdly, embodiments of the present invention provide a method for preparing an electrode sheet, the method comprising:

[0019] A slurry containing electrode active materials is coated on the current collector layer to obtain an active material layer.

[0020] A hydrophobic material is coated onto the active material layer to obtain a hydrophobic layer, which is then used to obtain the electrode sheet.

[0021] Optionally, the method further includes:

[0022] The hydrophobic material is atomized and then coated onto the active material layer.

[0023] Optionally, the areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

[0024] Optionally, the thickness of the hydrophobic layer is 2.9 μm-3.1 μm.

[0025] Optionally, the water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

[0026] Optionally, the hydrophobic material in the hydrophobic layer is at least partially infiltrated into the surface of the active material layer.

[0027] Optionally, the hydrophobic material includes one of 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

[0028] Fourthly, embodiments of the present invention provide an electrical device, including the electrode sheet described above, the lithium-ion battery described above, or the electrode sheet prepared by the preparation method described above.

[0029] The embodiments of the present invention have the following advantages:

[0030] The electrode sheet of this invention includes a current collector layer, an active material layer, and a hydrophobic layer arranged sequentially. The active material layer contains electrode active material and is located on the current collector layer. The hydrophobic layer contains hydrophobic material and is located on the active material layer. Therefore, the electrode sheet can effectively control the intrusion of external moisture into the battery, preventing an increase in the water content of the electrode active material and ensuring battery performance. Furthermore, the hydrophobic layer has low manufacturing cost and a simple manufacturing process; the hydrophobic material is disposed on the surface of the active material layer and does not affect the properties of the electrode active material, thus having a low impact on the overall energy density of the battery. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a structural block diagram of an electrode sheet according to an embodiment of the present invention;

[0033] Figure 2 This is a flowchart illustrating the steps of a method for preparing an electrode sheet according to an embodiment of the present invention;

[0034] Figure 3 This is a logic diagram of a method for preparing an electrode sheet according to an embodiment of the present invention. Detailed Implementation

[0035] The main sources of moisture in lithium-ion batteries are as follows: insufficient moisture content in the positive and negative electrode powder materials before feeding; inadequate dew point control during the manufacturing process; insufficient moisture content in the positive and negative electrode sheets and other battery components; and insufficient moisture content in the electrolyte, etc. Addressing the issue of insufficient moisture content in the positive electrode sheet, this invention proposes an electrode sheet, a lithium-ion battery, and a method for preparing the electrode sheet. The aim is to improve the hydrophobicity of the battery at low cost and without affecting its performance. To achieve this goal, the electrode sheet provided in this embodiment includes a current collector layer, an active material layer, and a hydrophobic layer arranged sequentially, thereby effectively controlling the intrusion of external moisture into the battery through the hydrophobic layer on the surface of the active material layer.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Reference Figure 1 The diagram shows a structural block diagram of an electrode sheet according to an embodiment of the present invention. The electrode sheet 10 includes a current collecting layer, an active material layer and a hydrophobic layer arranged sequentially.

[0038] The active material layer comprises an electrode active material, and the active material layer is located on the current collector layer;

[0039] The hydrophobic layer comprises a hydrophobic material and is located on the active material layer.

[0040] The electrode sheet of this invention includes a current collector layer, an active material layer, and a hydrophobic layer arranged sequentially. The active material layer contains an electrode active material and is located on the current collector layer. The hydrophobic layer contains a hydrophobic material and is located on the active material layer. This invention can effectively control the intrusion of external moisture into the battery through the hydrophobic layer on the surface of the active material layer, avoid the increase of water content in the electrode active material in the active material layer, and ensure the performance of the battery.

[0041] In one embodiment, the electrode active material comprises lithium manganese iron phosphate; the active material layer is formed in an environment with a dew point temperature of less than -40 degrees Celsius. Lithium manganese iron phosphate is highly sensitive to moisture; when its moisture content is high, it can cause severe failure phenomena such as reduced coulombic efficiency, severe gas generation, and cycle failure.

[0042] In this embodiment of the invention, the electrode active material including lithium manganese iron phosphate powder can be baked with other auxiliary materials such as binder and conductive agent, and then mixed in a low dew point environment to prepare an active slurry. The active slurry is then coated on the current collector layer to obtain an active material layer.

[0043] The dew point temperature refers to the temperature at which water vapor in the air condenses into dew (or frost) under constant atmospheric pressure; it is the temperature at which the water vapor content in the air reaches saturation. When the actual temperature drops below the dew point temperature, the water vapor in the air will condense into liquid water, forming phenomena such as dew, fog, or clouds. The lower the dew point temperature, the less water vapor is required to reach saturation, and the lower the relative humidity.

[0044] In environments with a dew point temperature below -40 degrees Celsius, the water vapor content in the air is extremely low, almost approaching a vacuum. During the preparation of the reactive slurry and coating process, the dew point temperature can be lowered to below -40 degrees Celsius to control humidity. Those skilled in the art can, based on the concept of this invention, set the environment for preparing the reactive slurry and forming the reactive material layer to other appropriate dew point temperature values; this invention does not limit such settings.

[0045] In addition, lithium iron manganese phosphate (LiMnFePO4) is a cathode material for lithium-ion batteries. It belongs to the category of phosphate-based lithium-ion battery materials. This material combines the advantages of lithium iron phosphate (LiFePO4) and lithium manganese phosphate (LiMnPO4), and has high energy density, good thermal stability and cycle stability.

[0046] The main function of binders in the manufacture of lithium-ion battery electrodes is to tightly bind the active materials, conductive agents, and current collectors that make up the current collector layer together to form a stable electrode structure. In the embodiments of this invention, the binder can be at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), or polyvinyl alcohol (PVA), and this invention is not limited thereto.

[0047] The main function of conductive agents in the manufacture of lithium-ion battery electrodes is to provide electronic conduction pathways, ensuring that the active materials in the electrodes can effectively participate in electrochemical reactions. Conductive agents are typically highly conductive materials that are added to the electrode slurry and mixed with the active materials and binders to form a conductive network, thereby improving the overall conductivity of the electrode. In the embodiments of this invention, the binder can be at least one of the following: carbon black, graphite, carbon nanotubes (CNTs), conductive fibers (such as carbon fibers), or metal powders (such as silver powder or copper powder). This invention is not limited to this specific type.

[0048] In this embodiment of the invention, lithium manganese iron phosphate is used as one of the materials for making active slurry, which can improve the performance of lithium-ion batteries. At the same time, making active slurry and forming active material layer in an environment with a dew point temperature of less than -40 degrees Celsius can ensure that the moisture content of the environment is low, thereby reducing the water content of the active material layer.

[0049] In one embodiment, the water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

[0050] This invention allows for the baking of lithium manganese iron phosphate powder, binders, conductive agents, and other auxiliary materials to reduce the moisture content of these materials to 200 ppm (parts per million) of their total mass. At this point, the moisture content of all materials is reduced to a acceptable level, enabling the preparation of the active slurry and the formation of the active material layer at a dew point temperature below -40°C. The moisture content of the active material layer is then further reduced to 200 ppm (parts per million) of its total mass through baking. The moisture content of each material can be calculated as follows:

[0051] 1) Drying method (oven drying method): Take a certain amount of LMFP sauce sample, usually 1-2 grams; put the sample into a pre-weighed weighing bottle and record the initial weight; put the weighing bottle into an oven and dry it at about 105℃ until constant weight; take out the weighing bottle, put it in a desiccator to cool to room temperature, and weigh it again; calculate the moisture content: Moisture content (%) = (initial weight - weight after drying) / initial weight × 100%.

[0052] 2) Karl Fischer titration: Titration is performed using Karl Fischer reagent (a mixture of iodine, sulfur dioxide, pyridine, and methanol); the water in the sample reacts with the reagent, and the water content is determined by the titration endpoint; this reaction is quantitative, that is, one mole of water consumes one mole of iodine; by measuring the amount of iodine consumed, the water content in the sample can be calculated.

[0053] 3) Infrared moisture determination method: Using an infrared moisture analyzer, the sample is heated by infrared radiation; the instrument will automatically record the mass change of the sample, thereby calculating the moisture content.

[0054] 4) Microwave Moisture Determination: A microwave moisture analyzer is used to heat the sample with microwaves; the instrument automatically records the mass change of the sample, thereby calculating the moisture content.

[0055] The choice of which method to use to calculate the moisture content of a material depends on the laboratory equipment, the nature of the sample, and the required accuracy. The drying method is preferred in this embodiment of the invention because it is simple, inexpensive, and applicable to most samples.

[0056] In one embodiment, the hydrophobic material includes one of 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

[0057] In this embodiment of the invention, the hydrophobic material can be 2H,3H-decafluoropentane. 2H,3H-decafluoropentane can be coated onto the active material layer to obtain a hydrophobic layer. 2H,3H-decafluoropentane (HFC), also known as decafluoropentane, has the molecular formula C5H2F. 10 With a molecular weight of 252.05, purity >98%, density 1.6 g / mL, melting point -80℃, and boiling point 55℃, HFC is a colorless, odorless liquid with extremely low surface tension and high chemical stability, thus exhibiting excellent hydrophobic properties. Furthermore, because all hydrogen atoms in its molecule are replaced by fluorine atoms, this compound possesses high thermal stability and chemical inertness, making it resistant to reaction with other substances.

[0058] In addition, the hydrophobic material can also be one of polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane. Those skilled in the art can select suitable materials to fabricate the hydrophobic layer according to the principles of this invention, and this invention does not limit such selection.

[0059] In one embodiment, the hydrophobic material in the hydrophobic layer at least partially penetrates the surface of the active material layer.

[0060] In one embodiment, the hydrophobic layer is at least partially dissolved in the electrolyte.

[0061] In this embodiment of the invention, after the hydrophobic layer dries, the electrode sheet, which includes a current collector layer, an active material layer, and a hydrophobic layer, is rolled. During the rolling process, the hydrophobic material of the hydrophobic layer can at least partially penetrate into the surface of the active material layer. When the electrode sheet comes into contact with the electrolyte, the hydrophobic layer can also at least partially dissolve in the electrolyte. Specifically, the hydrophobic material of the hydrophobic layer that has not penetrated into the active material layer can dissolve in the electrolyte.

[0062] The hydrophobic material of the hydrophobic layer in this embodiment of the invention is soluble in the electrolyte to inhibit electrolyte acidification and improves oxidation resistance by changing the solvation structure of the electrolyte. Preferably, the hydrophobic material can spontaneously evaporate under specified conditions without affecting the battery capacity.

[0063] In one embodiment, the thickness of the hydrophobic layer is 2.9 μm-3.1 μm.

[0064] In one embodiment, the areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

[0065] In this embodiment of the invention, the thickness of the hydrophobic layer can be 2.9 μm-3.1 μm. The areal density of the hydrophobic material in the hydrophobic layer can be 4.6 g / m³. 2 -5g / m 2 The thickness of the hydrophobic layer can be determined based on its waterproof performance. Experiments have shown that a hydrophobic layer with a thickness of 2.9 μm to 3.1 μm exhibits good waterproof performance. Those skilled in the art can also set the thickness of the hydrophobic layer to other appropriate values ​​based on the principles of this invention, and this invention does not impose any limitations on this.

[0066] Excessive hydrophobic material content will affect the battery's energy density; insufficient hydrophobic material content will have limited effect on the electrolyte's antioxidant properties. Experiments showed that when the areal density of the hydrophobic material is 4.8 ± 0.2 g / m², the hydrophobic material dissolved in the electrolyte effectively improves the electrolyte's antioxidant properties. Preferably, the hydrophobic material is HFC. After determining the surface area of ​​the current collector, the amount of hydrophobic material can be determined based on the surface area and areal density of the current collector; then, the hydrophobic material is densely and uniformly coated onto the active material layer at a dosage of 4.8 ± 0.2 g / m² for a single electrode.

[0067] After the hydrophobic material is coated on the active material layer, the areal density of the hydrophobic layer can be measured as follows: First, measure the mass of the electrode sheet with a fixed area coated with the hydrophobic material; then immerse the electrode sheet in a solution to dissolve the hydrophobic layer; next, dry the electrode sheet and weigh it; the mass of the hydrophobic material in the hydrophobic layer can be obtained by the mass difference of the electrode sheet before and after the hydrophobic layer dissolves; the areal density of the hydrophobic layer can be obtained by the mass of the hydrophobic material and the area of ​​the electrode sheet.

[0068] This invention uses HFC and other materials as hydrophobic materials for the hydrophobic layer, which can effectively control the intrusion of external moisture into the battery, avoid increasing the water content of lithium manganese iron phosphate, and ensure battery performance. Meanwhile, the preparation cost of the hydrophobic layer is low and the preparation process is simple; the hydrophobic material only needs to be sprayed onto the surface of the active material layer, and does not need to be incorporated into the slurry of the positive electrode material, avoiding a reduction in the proportion of positive electrode active material and having a low impact on the overall energy density of the battery; furthermore, the hydrophobic material can be dissolved in the electrolyte as a diluent to locally dilute the electrolyte, improving oxidation resistance by changing the solvation structure of the electrolyte; and HFC does not affect the battery capacity.

[0069] Furthermore, if the surface area of ​​the electrode is too large, or the number of electrodes is too great, a hydrophobic layer can be formed by atomizing the hydrophobic material and then spraying it onto the active material layer, thereby improving the efficiency of hydrophobic layer production. Specifically, the hydrophobic material can be atomized in a certain area, ensuring that the atomized hydrophobic material is evenly distributed in that area. Then, the baked and coated electrodes are passed through that area sequentially at a specific speed, so that the surface of all electrodes is evenly coated with the hydrophobic material, forming a hydrophobic layer.

[0070] An electrode sheet provided in this invention includes a current collector layer, an active material layer, and a hydrophobic layer sequentially disposed therefrom. The active material layer is formed by coating the current collector layer with a slurry containing lithium manganese iron phosphate. The hydrophobic layer is formed by baking the coated electrode sheet and then spraying the hydrophobic material onto the active material layer. This effectively controls the intrusion of external moisture into the battery, preventing an increase in the water content of the lithium manganese iron phosphate and ensuring battery performance. Furthermore, the hydrophobic layer has low manufacturing cost, a simple preparation process, and minimal impact on the overall energy density of the battery, without affecting its capacity.

[0071] This invention also provides a lithium-ion battery, which includes the electrode plates described above.

[0072] In one embodiment, the lithium-ion battery further includes an electrolyte, and the hydrophobic layer is at least partially dissolved in the electrolyte; the content of hydrophobic material in the electrode sheet is greater than 5 times the content of hydrophobic material in the electrolyte.

[0073] In this embodiment of the invention, the electrode sheet comprising a current collector layer, an active material layer, and a hydrophobic layer can be rolled. During the rolling process, the hydrophobic material of the hydrophobic layer can at least partially penetrate into the surface of the active material layer. The lithium-ion battery also includes an electrolyte. When the electrode sheet comes into contact with the electrolyte, the hydrophobic layer can also at least partially dissolve in the electrolyte. For example, the hydrophobic material of the hydrophobic layer that has not penetrated into the active material layer can dissolve in the electrolyte.

[0074] However, the hydrophobic material that penetrates the active material layer during the rolling process cannot dissolve in the electrolyte. Therefore, after disassembling the lithium-ion battery provided in this embodiment of the invention, the content of hydrophobic material in the electrode sheet and the electrolyte can be tested separately. The test results show that the content of hydrophobic material in the electrode sheet is more than 5 times higher than that in the electrolyte. Typically, the content of hydrophobic material in the electrode sheet is approximately 1000ppm-10000ppm, and the content of hydrophobic material in the electrolyte is approximately 1000ppm-5000ppm.

[0075] Based on the test results, this embodiment of the invention can determine whether the hydrophobic material is coated on the electrode sheet or directly added to the electrolyte. If the content of the hydrophobic material in the electrode sheet is more than 5 times the content of the hydrophobic material in the electrolyte, it indicates that the hydrophobic material is coated on the electrode sheet; if the content of the hydrophobic material in the electrode sheet is less than or equal to 5 times the content of the hydrophobic material in the electrolyte, it indicates that the hydrophobic material is directly added to the electrolyte.

[0076] The content of hydrophobic material in the electrode sheet is more than 5 times that in the electrolyte, which can effectively ensure the hydrophobicity of the electrode and the antioxidant properties of the electrolyte.

[0077] Reference Figure 2 The diagram illustrates a step-by-step flowchart of a method for preparing an electrode sheet according to an embodiment of the present invention. The method may specifically include the following steps:

[0078] Step 201: Coat the current collector layer with a slurry containing electrode active material to obtain an active material layer;

[0079] In one embodiment, the electrode active material comprises lithium manganese iron phosphate; the active material layer is formed in an environment with a dew point temperature of less than -40 degrees Celsius.

[0080] In this embodiment of the invention, the electrode active material, including lithium manganese iron phosphate powder, is baked with other auxiliary materials such as binders and conductive agents, and then mixed in a low dew point environment to prepare an active slurry. The active slurry is then coated onto the current collector layer to obtain an active material layer. This embodiment of the invention prepares the active slurry in an environment with a dew point temperature below -40 degrees Celsius, ensuring low moisture content in the environment and thus reducing the water content of the active material layer.

[0081] In one embodiment, the water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

[0082] This invention allows for the baking of lithium manganese iron phosphate powder, binders, conductive agents, and other auxiliary materials to reduce the moisture content of these materials to 200 ppm (parts per million) of their total mass. At this point, the moisture content of each material is reduced to a acceptable level, enabling the preparation of the active slurry and the formation of the active material layer at a dew point temperature below -40°C. Baking further reduces the moisture content of the active material layer to 200 ppm (parts per million) of its total mass. This invention further reduces the moisture content of the active material layer through baking, thereby improving the performance of the electrode sheets.

[0083] Step 202: Coat the active material layer with a hydrophobic material to obtain a hydrophobic layer, thereby obtaining the electrode sheet.

[0084] In one embodiment, the hydrophobic material includes one of 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

[0085] In this embodiment of the invention, the hydrophobic material may include one of 2H, 3H-decafluoropentane, etc. Once the water content of the active material layer meets the standard, the hydrophobic material can be coated onto the active material layer to obtain a hydrophobic layer, thus obtaining the final electrode sheet. This electrode sheet includes a current collector layer, an active material layer, and a hydrophobic layer arranged sequentially. The hydrophobic layer can effectively control moisture intrusion and prevent the water content of the electrode active material in the active material layer from increasing.

[0086] In one embodiment, the method further includes: rolling the current collection layer, the active material layer and the hydrophobic layer to obtain the electrode sheet.

[0087] During the rolling process, the hydrophobic material in the hydrophobic layer at least partially penetrates into the surface of the active material layer; the hydrophobic layer at least partially dissolves in the electrolyte.

[0088] In this embodiment of the invention, the electrode sheet can be rolled, during which the hydrophobic material of the hydrophobic layer can at least partially penetrate into the surface of the active material layer. When the electrode sheet comes into contact with the electrolyte, the hydrophobic layer can also at least partially dissolve in the electrolyte. For example, the hydrophobic material of the hydrophobic layer that has not penetrated into the active material layer can dissolve in the electrolyte, while the hydrophobic material that has penetrated into the active material layer cannot dissolve in the electrolyte. The hydrophobic material of the hydrophobic layer in this embodiment of the invention can dissolve in the electrolyte to inhibit electrolyte acidification and improve oxidation resistance by changing the solvation structure of the electrolyte; moreover, the hydrophobic material can volatilize under specified conditions without affecting the battery capacity. The hydrophobic material is preferably HFC.

[0089] In one embodiment, the thickness of the hydrophobic layer is 2.9 μm-3.1 μm; the areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

[0090] In this embodiment of the invention, the thickness of the hydrophobic layer can be 2.9 μm-3.1 μm, and the areal density of the hydrophobic material in the hydrophobic layer can be 4.6 g / m³. 2 -5g / m 2The thickness of the hydrophobic layer can be determined based on its waterproof performance. Experiments have shown that a hydrophobic layer with a thickness of 2.9 μm to 3.1 μm exhibits good waterproof performance. The areal density of the hydrophobic material can be obtained based on the thickness of the hydrophobic layer and the surface area of ​​the current collector layer, or it can be calculated based on the effect of the hydrophobic material in the electrolyte. Those skilled in the art can also set the thickness of the hydrophobic layer and the areal density of the hydrophobic material to other appropriate values ​​according to the principles of this invention, and this invention does not impose any limitations on this.

[0091] In one embodiment, the method may further include: atomizing the hydrophobic material and coating the atomized hydrophobic material onto the active material layer.

[0092] In this embodiment of the invention, if the surface area of ​​the electrode is too large or the number of electrodes is too large, the coating efficiency can be improved by atomizing the hydrophobic material before spraying. Specifically, the hydrophobic material can be atomized in a certain area to uniformly distribute the atomized hydrophobic material in that area. Then, the baked and coated electrodes are passed through that area sequentially at a specific speed, so that the surface of all electrodes can be uniformly coated with the hydrophobic material.

[0093] After the electrode sheet coated with the hydrophobic material has naturally dried, it can be subjected to a rolling process. Before rolling, the rollers of the rolling mill can be wiped with alcohol to ensure they are clean and dry, preventing damage to the hydrophobic coating. After rolling, the electrode sheet can be placed in a high-moisture environment without failure. When reusing the electrode sheet, simply transfer it from a high-moisture environment to a low-moisture environment and allow it to stand for at least one hour to allow the surface moisture to evaporate naturally before normal use. Increasing the temperature appropriately can reduce the standing time. Those skilled in the art can set the standing time to other appropriate values ​​based on the concept of this invention, and this invention does not limit this.

[0094] The electrode preparation method provided in this invention involves coating an active material layer onto the current collector layer of the electrode using a slurry containing lithium manganese iron phosphate. Then, a hydrophobic material is used as the hydrophobic layer material. This hydrophobic material is either directly sprayed onto the active material layer, or atomized and sprayed onto the active material layer to obtain the hydrophobic layer. This effectively controls external moisture intrusion into the battery, preventing an increase in the water content of the lithium manganese iron phosphate and ensuring battery performance. Furthermore, the hydrophobic layer preparation is low-cost and simple. Since the hydrophobic material is disposed on the surface of the active material layer, it does not affect the properties of the materials within the active material layer, resulting in minimal impact on the overall energy density and capacity of the battery.

[0095] It should be noted that the electrode preparation method provided in the embodiments of the present invention can also be applied to other moisture-sensitive cathode materials, for example, in applications including but not limited to long-term storage of electrodes and emergency protection of electrodes in high-moisture environments.

[0096] Reference Figure 3 The diagram illustrates a logic diagram of an electrode preparation method according to an embodiment of the present invention. To enable those skilled in the art to better understand the embodiments of the present invention, the following explanation is provided. Figure 3 The embodiments of the present invention are described below:

[0097] Step 301: The moisture content of lithium manganese iron phosphate powder, as well as other auxiliary materials such as binders and conductive agents, is baked to 1 / 200 million per square meter, and then mixed and formulated into LMFP slurry under a low dew point environment.

[0098] Step 302: Coating the current collection layer of the electrode in a low dew point environment, and baking the moisture content of the coated electrode to 200 ppm per square meter (parts per million).

[0099] Step 303: According to the hydrophobic material content of 4.6-5.0 grams per square meter of electrode surface area, the hydrophobic material is sprayed onto the surface of the active material layer to form a hydrophobic layer with a thickness of 3μm.

[0100] Step 304: Wipe the rollers of the roller press with alcohol, and after the hydrophobic layer dries naturally, roll the electrode sheet;

[0101] Step 305: After the electrode is rolled, if the electrode is to be used, transfer the electrode to a low-moisture environment and let it stand until the moisture on the surface of the electrode evaporates on its own, then it can be used normally.

[0102] The electrode preparation method provided in this invention involves coating an active material layer onto the current collector layer of the electrode using a slurry containing lithium manganese iron phosphate. Then, a hydrophobic material is used as the hydrophobic layer material. This hydrophobic material is either directly sprayed onto the active material layer, or atomized and sprayed onto the active material layer to obtain the hydrophobic layer. This effectively controls external moisture intrusion into the battery, preventing an increase in the water content of the lithium manganese iron phosphate and ensuring battery performance. Furthermore, the hydrophobic layer preparation is low-cost, simple, has minimal impact on the overall energy density of the battery, and does not affect the battery capacity.

[0103] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0104] The following detailed description of the effects of the electrode preparation method provided in the embodiments of the present invention will be carried out through specific experiments.

[0105] The moisture content of lithium manganese iron phosphate powder, binder (PVDF) and conductive agent (carbon black) is baked to less than 1 / 200 million, and then mixed in a low dew point environment (-40°C) to prepare LMFP slurry; wherein the mass ratio of lithium manganese iron phosphate powder, binder (PVDF) and conductive agent (carbon black) is 96:2:2; the above slurry is coated on one side of the current collector and dried to obtain the primary electrode sheet;

[0106] 1) Take 6 primary electrode sheets from the same batch. Each primary electrode sheet is 100 mm * 100 mm in size, with an areal density of 110 g / m² and a compaction density of 2.4 g / m³. Coat one side of each electrode sheet and then bake the electrode sheet at 105 degrees Celsius for 24 hours.

[0107] 2) After baking, randomly select two primary electrode sheets and name them a and b respectively. Samples are taken at five points evenly distributed on the primary electrode sheets and the moisture content at the five sampling points is tested to obtain the initial moisture values ​​a1, a2...a5 and b1, b2...b5 corresponding to the two selected primary electrode sheets respectively.

[0108] 3) The remaining four primary electrode sheets are randomly divided into three groups: A, B, and C. Group A contains two electrode sheets, while groups B and C each contain one electrode sheet. Hydrophobic material is uniformly sprayed onto both sides of the two primary electrode sheets in group A to form a hydrophobic layer, thus obtaining the electrode sheet. The areal density of the hydrophobic material in the hydrophobic layer is 4.7 g / m³. 2 The thickness of the hydrophobic layer is 3.0 μm. Groups B and C, as control groups, did not undergo any treatment on the electrode sheets.

[0109] 4) Place the electrode sheets of group A and the primary electrode sheets of group B in an atmospheric environment with a dew point of 26 degrees Celsius for 24 hours, and store the primary electrode sheets of group C in an environment with a dew point of -40 degrees Celsius for later use.

[0110] 5) After 24 hours, randomly select one electrode from the electrode sheets of group A and name it c. Select the primary electrode sheet from group B and name it d. Sample and test the moisture content at 5 points evenly distributed on the electrode sheets to obtain moisture values ​​c1, c2...c5 and d1, d2...d5.

[0111] 6) Name another electrode sheet from group A as e, and the primary electrode sheet from group C as f. Assemble them into lithium coin cells, five in each group. Record the coin cell capacities as e1, e2...e5 and f1, f2...f5, respectively. Here, the coin cell capacity represents the rated capacity of the battery after a certain number of charge-discharge cycles.

[0112] Based on the ideas of this invention, those skilled in the art can set the number of electrodes and the number of samples in the experiment to other appropriate values, and this invention does not limit this.

[0113] The moisture content was tested using a coulometric Karl Fischer moisture analyzer, and the results are shown in Table 1. The unit for moisture content is parts per million (ppm).

[0114] Table 1

[0115]

[0116] As shown in Table 1, when electrodes with the same initial moisture content are placed in a high-moisture environment, the moisture content of the electrodes coated with hydrophobic materials remains basically unchanged, while the moisture content of the control group increases by more than 10 times, indicating that the hydrophobic layer can effectively isolate moisture intrusion.

[0117] Using 1 mol / L LiPF6 as the electrolyte (solvent consisting of 15% DMC + 40% EMC + 15% DEC + 30% EC by mass), a polypropylene separator, and a lithium metal sheet as the negative electrode, an R2023 button cell was tested with the above electrode assembly.

[0118] Using a 5V-3A test cabinet from Blue Electric, the electrode was charged to 4.3V under constant current and constant voltage conditions at 0.1C, with a cutoff current of 0.02C; then discharged to 2.5V under constant current conditions at 0.1C. This charge-discharge cycle was repeated three times, and the discharge capacity of the third cycle was taken as the coin capacity (mAh / g). The capacity (mAh / g) after 100 cycles was used to evaluate the cycle stability of the electrode. The test results are shown in Table 2.

[0119] Table 2

[0120]

[0121] As shown in the table above, under the same conditions, the coin capacity of lithium-ion batteries assembled with electrodes coated with hydrophobic materials is almost the same as that of the control group, indicating that the hydrophobic layer formed by the hydrophobic material does not affect the battery capacity. Meanwhile, the battery without a hydrophobic layer shows significant capacity decay after 100 coin cycles, suggesting that the hydrophobic layer can also improve the battery's cycle performance.

[0122] Experiments in this invention demonstrate that coating the electrode sheet with hydrophobic material effectively controls external moisture intrusion into the battery, preventing an increase in the water content of lithium manganese iron phosphate and ensuring battery performance. Furthermore, the hydrophobic layer prepared from the hydrophobic material is low-cost and simple to prepare; it only needs to be sprayed onto the surface of the active material layer and does not need to be incorporated into the positive electrode slurry, thus avoiding a decrease in the proportion of positive electrode active material and having a minimal impact on the overall energy density of the battery. Moreover, the hydrophobic material in the hydrophobic layer can be dissolved in the electrolyte as a diluent for localized dilution, improving oxidation resistance by altering the solvation structure of the electrolyte without affecting battery capacity. This invention also provides an electrical device comprising the aforementioned electrode sheet, the aforementioned lithium-ion battery, or the electrode sheet prepared by the aforementioned method.

[0123] The electrical devices in this invention can be electric vehicles, such as electric cars. Furthermore, the electrical devices may also include: portable electronic devices, wearable devices, power tools, medical devices, energy storage systems, industrial equipment, etc. The lithium-ion battery provided in this invention has good hydrophobicity, large capacity, and high reliability, enabling these electrical devices to provide longer usage time, lighter weight, and smaller size, thereby improving the user experience. With technological advancements and cost reductions, the application of lithium-ion batteries in more types of electrical devices will continue to expand.

[0124] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0125] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0126] Finally, it should be noted that in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or terminal device.

[0127] The present invention has provided a detailed description of an electrode sheet, a lithium-ion battery, and a method and apparatus for preparing the electrode sheet. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An electrode sheet, characterized in that, The electrode sheet includes a current collecting layer, an active material layer and a hydrophobic layer arranged sequentially. The active material layer comprises an electrode active material, and the active material layer is located on the current collector layer; The hydrophobic layer comprises a hydrophobic material and is located on the active material layer.

2. The electrode sheet according to claim 1, characterized in that, The areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

3. The electrode sheet according to claim 1, characterized in that, The thickness of the hydrophobic layer is 2.9 μm-3.1 μm.

4. The electrode sheet according to claim 1, characterized in that, The water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

5. The electrode sheet according to claim 1, characterized in that, The hydrophobic material in the hydrophobic layer at least partially penetrates the surface of the active material layer.

6. The electrode sheet according to claim 1, characterized in that, The hydrophobic layer is at least partially dissolved in the electrolyte.

7. The electrode sheet according to claim 1, characterized in that, The active material layer is formed in an environment with a dew point temperature of less than -40 degrees Celsius.

8. The electrode sheet according to claim 1, characterized in that, The electrode active material includes lithium manganese iron phosphate.

9. The electrode sheet according to claim 1, characterized in that, The hydrophobic material includes one of the following: 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the electrode plates described in claims 1-9.

11. The lithium-ion battery according to claim 10, characterized in that, It also includes an electrolyte, in which the hydrophobic layer is at least partially dissolved.

12. The lithium-ion battery according to claim 11, characterized in that, The content of hydrophobic material in the electrode sheet is more than 5 times the content of hydrophobic material in the electrolyte.

13. A method for preparing an electrode sheet, characterized in that, The method includes: A slurry containing electrode active materials is coated on the current collector layer to obtain an active material layer. A hydrophobic material is coated onto the active material layer to obtain a hydrophobic layer, which is then used to obtain the electrode sheet.

14. The method according to claim 13, characterized in that, The method further includes: The hydrophobic material is atomized and then coated onto the active material layer.

15. The method according to claim 13, characterized in that, The areal density of the hydrophobic material in the hydrophobic layer is 4.6 g / m³. 2 -5g / m 2 .

16. The method according to claim 13, characterized in that, The thickness of the hydrophobic layer is 2.9 μm-3.1 μm.

17. The method according to claim 13, characterized in that, The water content of the active material layer is less than or equal to 200 parts per million of the total mass of the active material layer.

18. The method according to claim 13, characterized in that, The hydrophobic material in the hydrophobic layer is at least partially infiltrated into the surface of the active material layer.

19. The method according to claim 13, characterized in that, The hydrophobic material includes one of the following: 2H,3H-decafluoropentane, polydimethylsiloxane, polytetrafluoroethylene, silica nanoparticles, alumina nanoparticles, polyurethane, polyimide, acrylate polymers, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, and perfluorodecane.

20. An electrical appliance, characterized in that, The electrode sheet includes the electrode sheet according to any one of claims 1-9, the lithium-ion battery according to any one of claims 10-12, or the electrode sheet prepared by the preparation method according to any one of claims 13-19.

Images