Cells and batteries

Abstract

This improves the cell's cycle characteristics, ensuring battery stability and reliability during long-term use. [Solution] The present invention discloses a cell and a battery. The cell includes a negative electrode plate, a separator, and a positive electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode active material coating. The positive electrode plate includes a positive electrode current collector and a positive electrode active material coating. The separator includes a substrate, a first coating, and a second coating. If the porosity of the first coating is A, the thickness of the first coating is a μm, the porosity of the second coating is B, the thickness of the second coating is b μm, the porosity of the negative electrode active material coating is C, the thickness of the negative electrode active material coating is c μm, the porosity of the positive electrode active material coating is D, and the thickness of the positive electrode active material coating is d μm, then by limiting the porosity to 0.8 ≤ [(Dd + Bb) / (b + d)] / [(Aa + Cc) / (a ​​+ c)] ≤ 1.2, the porosity of both sides of the substrate of the separator is made relatively close.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to cells and batteries.

Background Art

[0002] In the development process of lithium-ion batteries, the optimization of cell characteristics has always been a core research direction. A cell is a major component of a battery, and its characteristics directly determine important indicators such as the energy density, cycle life, and safety of the battery.

[0003] As an important component of a cell, a separator not only isolates the positive and negative electrodes to prevent short circuits but also plays an important role in storing the electrolyte and ion conduction. However, in the current cell design and manufacturing process, the problem of balancing the porosity on both sides of the separator substrate has not been effectively solved. When there is a large difference in the porosity on both sides of the separator substrate, an imbalance occurs in the adsorption and retention ability of the electrolyte for the double-sided coating. For example, if the porosity on one side is too high, excessive adsorption of the electrolyte occurs, and if the porosity on the other side is too low, insufficient penetration of the electrolyte occurs, which has a significant impact on the uniform distribution of the electrolyte in the cell. When the distribution of the electrolyte becomes non-uniform, further obstacles to ion transport occur. During the charge and discharge process of the battery, lithium ions cannot be transported smoothly and uniformly on both sides of the separator, and the consistency of the electrochemical reaction in the cell is impaired. As a result, not only does the energy conversion efficiency of the cell decrease, but it also has a significant impact on the cycle characteristics of the cell. As the number of charge and discharge cycles increases, the degradation of cell characteristics becomes severe, and the stability and reliability of the battery are significantly reduced.

[0004] Conventional technologies have limitations in controlling the porosity distribution on both sides of the separator, making it difficult to accurately control the electrolyte distribution and ion transport environment within the cell. Therefore, there is an urgent need to develop technologies that effectively balance the porosity on both sides of the separator and ensure a balanced electrolyte volume to improve the cell's cycle characteristics and stability. This has significant practical implications for promoting the development and application of lithium-ion battery technology. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to solve at least one of the technical problems present in the prior art. The present invention aims to provide a cell and a battery that ensure the stability and reliability of the battery during long-term use. [Means for solving the problem]

[0006] To achieve the above objective, in a first aspect, the present invention provides a cell comprising, in order, a negative electrode plate, a separator, and a positive electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active material coating, the negative electrode active material coating being applied to the surface of the negative electrode current collector facing the separator, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating, the positive electrode active material coating being applied to the surface of the positive electrode current collector facing the separator, and the separator comprising a substrate, a first coating, and a second coating, the first coating The first coating is applied to the surface of the substrate facing the negative electrode plate and is in contact with the negative electrode active material coating, and the second coating is applied to the surface of the substrate opposite to the first coating and is in contact with the positive electrode active material coating. If the porosity of the first coating is A, the thickness of the first coating is a μm, the porosity of the second coating is B, the thickness of the second coating is b μm, the porosity of the negative electrode active material coating is C, the thickness of the negative electrode active material coating is c μm, the porosity of the positive electrode active material coating is D, and the thickness of the positive electrode active material coating is d μm, then The condition satisfies 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2.

[0007] In some embodiments, 0.25 ≤ C / A ≤ 0.67.

[0008] In some embodiments, 0.11 ≤ D / B ≤ 0.43.

[0009] In some embodiments, 60% ≤ A ≤ 80% and 0.5 μm ≤ a ≤ 3 μm.

[0010] In some embodiments, 70% ≤ B ≤ 90% and 0.5 μm ≤ b ≤ 5 μm.

[0011] In some embodiments, 20% ≤ C ≤ 40% and 50.5 μm ≤ c ≤ 54 μm.

[0012] In some embodiments, 10% ≤ D ≤ 30% and 42 μm ≤ d ≤ 46 μm.

[0013] In some embodiments, if the pore size of the first coating is Eμm, the pore size of the second coating is Fμm, and the pore size of the substrate is Gμm, The following conditions are met: 0.1≦E≦2, 0.3≦F≦4, 0.02≦G≦0.08, and F>E>G.

[0014] In some embodiments, if the air permeability of the first coating is Js / 100cc and the air permeability of the second coating is Ks / 100cc, The following conditions are met: 5 ≤ J ≤ 70, 5 ≤ K ≤ 50, and J ≥ K.

[0015] In some embodiments, the substrate includes one or more of polyethylene, polypropylene, polyimide, and polyethylene terephthalate. The first coating consists of a first organic polymer and a first inorganic material. The aforementioned second coating consists of a second organic polymer and a second inorganic material. The first organic polymer includes one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metharamid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate. The first inorganic material includes one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate. The second organic polymer includes one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metharamid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate. The second inorganic material includes one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate.

[0016] In some embodiments, the mass ratio of the first organic polymer to the first inorganic material is (0-9.5):1, and the mass ratio of the second organic polymer to the second inorganic material is (0-9.5):1.

[0017] In some embodiments, the first inorganic material comprises first inorganic particles, the second inorganic material comprises second inorganic particles, and the average particle diameter of the first inorganic particles under an electron microscope is Hμm, and the average particle diameter of the second inorganic particles under an electron microscope is Iμm. The conditions 0.2 ≤ H ≤ 0.8, 0.4 ≤ I ≤ 1.5, and I ≥ H are satisfied.

[0018] In a second aspect, the present invention also provides a battery, the battery including a cell according to any one of the above, further including a case and an electrolyte, the cell and the electrolyte both being provided within the case.

[0019] In a third aspect, the present invention also provides a method for manufacturing a battery according to any one of the above, the manufacturing method including steps of manufacturing a positive electrode plate, manufacturing a negative electrode plate, manufacturing a separator, manufacturing an electrolyte, and manufacturing a battery. The step of manufacturing the positive electrode plate includes coating a mixture obtained by sufficiently stirring lithium cobaltate, acetylene black, and polyvinylidene fluoride in an N-methylpyrrolidone solvent system until uniformly mixed onto a positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode plate. The step of manufacturing the negative electrode plate includes coating a mixture obtained by sufficiently stirring artificial graphite, acetylene black, styrene-butadiene rubber as a binder, and sodium carboxymethyl cellulose as a thickener in a deionized water solvent system until uniformly mixed onto a negative electrode current collector, followed by drying, cold pressing, and slitting to obtain the negative electrode plate. The step of manufacturing the separator includes applying a first coating onto one surface of a substrate and applying a second coating onto the other surface of the substrate. The step of manufacturing the electrolyte includes using a solution formulated with a lithium salt and a non-aqueous organic solvent as the electrolyte. The step of manufacturing the battery includes sequentially laminating the negative electrode plate, the separator, and the positive electrode plate, fabricating a cell through a winding process or a lamination process, placing the cell into a case, injecting the electrolyte into the case and sealing it to obtain the battery.

[0020] In some embodiments, in the step of manufacturing the positive electrode plate, the mass ratio of the lithium cobaltate, the acetylene black, and the polyvinylidene fluoride is 95:3:2.

[0021] In some embodiments, in the step of manufacturing the negative electrode plate, the mass ratio of the artificial graphite, the acetylene black, the styrene-butadiene rubber as the binder, and the sodium carboxymethyl cellulose as the thickener is 96:1:1.5:1.5.

[0022] In some embodiments, in the step of manufacturing the electrolyte, the mass ratio of the lithium salt and the non-aqueous organic solvent is 8:92.

[0023] In some embodiments, the non-aqueous organic solvent is prepared from 20 parts by weight of ethylene carbonate, ext{30} parts by weight of diethyl carbonate, 20 parts by weight of propylene carbonate, 28 parts by weight of propyl propionate, and 2 parts by weight of vinylene carbonate as raw materials.

Advantages of the Invention

[0024] Examples of the present invention provide a cell, and compared with the prior art, the beneficial effects are as follows. By limiting the condition of 0.8≦[(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)]≦1.2, the porosity on both sides of the base material of the separator can be made in a relatively close state, thereby balancing the porosity distribution on both sides of the base material, and further making the adsorption and retention capabilities of the coatings located on both sides of the base material for the electrolyte consistent, which contributes to maintaining the balance of the liquid retention amounts of the electrolyte of the coatings located on both sides of the base material. By taking the balance of the liquid retention amounts, the ion transport environment in the cell is stabilized, and further, the obstacles to ion transport caused by the non-uniform distribution of the electrolyte on both sides of the battery separator can be avoided, which contributes to improving the cycle characteristics of the cell and ensuring the stability and reliability of the battery during long-term use.

Brief Description of the Drawings

[0025] [Figure 1] It is a schematic structural diagram of the cell provided by the example of the present invention.

Modes for Carrying Out the Invention

[0026] Specific embodiments of the present invention will be described in further detail below with reference to the drawings and examples. The following examples are used to illustrate the present invention and are not intended to limit the scope of the invention.

[0027] In the description of this invention, directions or positional relationships indicated by terms such as "length," "width," "thickness," "top," "bottom," "vertical," "horizontal," "summit," "bottom," "inside," and "outside" are based on the directions or positional relationships shown in the drawings. These terms are used for convenience in explaining the invention and to simplify the explanation, and do not indicate or imply that the devices or elements mentioned have a specific direction or must be configured and operate in a specific direction. Therefore, they should not be understood as limiting the invention.

[0028] The terms “First” and “Second” are used for descriptive purposes only and should not be understood as indicating or implying relative importance or the number of technical features being described. Therefore, features limited by “First” or “Second” may explicitly or implicitly include one or more such features.

[0029] In this invention, unless otherwise specified or limited, terms such as “attach,” “connect,” “join,” and “fix” should be understood in a broad sense, and may include, for example, fixed connections, removable connections, or integral connections. These may be mechanical or electrical connections. They may be direct connections, indirect connections via an intermediate medium, internal communication between two elements, or interaction relationships between two elements. Those skilled in the art will understand the specific meanings of these terms in this invention depending on the specific context.

[0030] In the present invention, unless otherwise specified or limited, the statement that a first feature is "above" or "below" a second feature may include the first and second features being in direct contact, or being in contact with each other via another feature, even if they are not in direct contact. Furthermore, the statement that a first feature is "above," "above," and "higher than" a second feature includes the first feature being directly above and diagonally above the second feature, or simply indicating that the first feature is higher horizontally than the second feature. The statement that a first feature is "below," "below," and "lower than" a second feature includes the first feature being directly below and diagonally below the second feature, or simply indicating that the first feature is lower horizontally than the second feature.

[0031] Unless otherwise defined, all technical and scientific terms used in this Application have the same meaning as those commonly understood by those skilled in the art. Terms used in this Specification are solely for the purpose of describing specific embodiments and are not intended to limit this Application. The terms “including” and “having,” and their variations, in the Specification and Claims of this Application, as well as in the description of the above drawings, are intended to be non-exclusive inclusions.

[0032] References to “Examples” in this Application mean that certain features, structures, or properties described with reference to an Example may be included in at least one Example of this Application. The term, appearing in various parts of the Specification, does not necessarily refer to the same Example, nor are they mutually exclusive, independent, or alternative Examples. First aspect

[0033] As shown in Figure 1, an embodiment of the present invention provides a cell comprising a negative electrode plate 1, a separator 3, and a positive electrode plate 2, which are stacked in order.

[0034] The negative electrode plate 1 includes a negative electrode current collector 11 and a negative electrode active material coating 12, the negative electrode active material coating 12 being applied to the surface of the negative electrode current collector 11 facing the separator 3; the positive electrode plate 2 includes a positive electrode current collector 21 and a positive electrode active material coating 22, the positive electrode active material coating 22 being applied to the surface of the positive electrode current collector 21 facing the separator 3; the separator 3 includes a base material 31, a first coating 32, and a second coating 33, the first coating 32 being applied to the surface of the base material 31 facing the negative electrode plate 1 and in contact with the negative electrode active material coating 12; and the second coating 33 being applied to the surface of the base material 31 opposite to the first coating 32 and in contact with the positive electrode active material coating 22.

[0035] If the porosity of the first coating 32 is A, the thickness of the first coating 32 is a μm, the porosity of the second coating 33 is B, the thickness of the second coating 33 is b μm, the porosity of the negative electrode active material coating 12 is C, the thickness of the negative electrode active material coating 12 is c μm, the porosity of the positive electrode active material coating 22 is D, and the thickness of the positive electrode active material coating 22 is d μm, then the equation 0.8 ≤ [(Dd + Bb) / (b + d)] / [(Aa + Cc) / (a + c)] ≤ 1.2 is satisfied.

[0036] According to this technical solution, by limiting the condition to 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2, the porosity on both sides of the substrate 31 can be made relatively close, balancing the porosity distribution on both sides of the substrate 31. This allows the adsorption and retention capacity of the coatings located on each side of the substrate 31 to be matched, which contributes to maintaining a balance in the electrolyte volume of the coatings located on both sides of the substrate 31. By balancing the electrolyte volume, the ion transport environment within the cell is stabilized, and ion transport problems caused by the uneven distribution of electrolyte on both sides of the battery separator 3 can be avoided. This improves the cell's cycle characteristics and contributes to ensuring the stability and reliability of the battery during long-term use.

[0037] In the present invention, the method for measuring the thickness of the first coating 32, the second coating 33, the negative electrode active material coating 12, and the positive electrode active material coating 22 is as follows. The first coating 32 is subjected to argon ion polishing to obtain a cross-section of the first coating 32, the cross-sectional morphology in the thickness direction of the first coating 32 is observed using a field emission scanning electron microscope (Philips XL-30), a scanning electron microscope image is taken, and the thickness a of the first coating 32 is measured using the scanning electron microscope.

[0038] The second coating 33 is subjected to argon ion polishing to obtain a cross-section of the second coating 33. The cross-sectional morphology in the thickness direction of the second coating 33 is observed using a field emission scanning electron microscope (Philips XL-30), scanning electron microscope images are taken, and the thickness b of the second coating 33 is measured using the scanning electron microscope.

[0039] The negative electrode active material coating 12 is subjected to argon ion polishing to obtain a cross-section of the negative electrode active material coating 12. The cross-sectional morphology in the thickness direction of the negative electrode active material coating 12 is observed using a field emission scanning electron microscope (Philips XL-30), scanning electron microscope images are taken, and the thickness c of the negative electrode active material coating 12 is measured using the scanning electron microscope.

[0040] The positive electrode active material coating 22 is subjected to argon ion polishing to obtain a cross-section of the positive electrode active material coating 22. The cross-sectional morphology in the thickness direction of the positive electrode active material coating 22 is observed using a field emission scanning electron microscope (Philips XL-30), scanning electron microscope images are taken, and the thickness d of the positive electrode active material coating 22 is measured using the scanning electron microscope.

[0041] In the present invention, the methods for measuring the porosity A of the first coating 32, the porosity B of the second coating 33, the porosity C of the negative electrode active material coating 12, and the porosity D of the positive electrode active material coating 22 are as follows.

[0042] A separator sample containing the first coating, substrate, and second coating is taken, and the second coating is removed using N-methylpyrrolidone (NMP) solvent to obtain a single-sided sample consisting only of the substrate and first coating. The porosity Pa of the single-sided sample is then measured according to ASTM D-2873. The first coating is then removed to obtain a sample consisting only of the substrate, and the porosity Pb ​​of the sample consisting only of the substrate is measured according to ASTM D-2873. Furthermore, the separator is subjected to argon ion polishing to obtain a cross-section of the separator, and the thickness Ta of the single-sided sample, the thickness Tb of the substrate, and the thickness Tc of the first coating are measured using a scanning electron microscope. Based on the following equations Ta = Tb + Tc and Tb / Ta × Pb + Tc / Ta × A = Pa (weighted average of substrate and coating), the porosity A is calculated according to the following equation A = (Tb × Pa - Ta × Pb) / Tc.

[0043] Similarly, the first coating of the separator is removed using NMP solvent to obtain a single-sided separator sample consisting only of the substrate and the second coating, and the porosity B of the second coating is calculated according to the measurement steps and calculation logic described above.

[0044] Similarly, by following the measurement steps and calculation logic described above, the porosity C of the negative electrode active material coating and the porosity D of the positive electrode active material coating can be obtained.

[0045] In some embodiments of the present invention, the negative electrode current collector 11 is copper foil, and the positive electrode current collector 21 is aluminum foil.

[0046] In some embodiments of the present invention, the first coating 32 is an organic polymer coating, and the second coating 33 is one or more of the ceramic coating and organic polymer coatings.

[0047] The appropriate porosity of the positive electrode, negative electrode, and separator 3 of a lithium-ion battery is crucial for improving the battery's energy density. The porosity allows for greater electrolyte capacity, enabling smoother ion transport during the charge-discharge process and contributing to increased energy density. However, the impact of porosity on battery characteristics is multifaceted. If the porosity of the positive and negative electrodes is too high, it can lead to loosening of the electrode plate structure, potentially reducing the battery's mechanical strength. During battery use, an unstable electrode structure can degrade battery performance. Conversely, if the porosity of the positive electrode, negative electrode, and separator 3 is too low, electrolyte penetration and ion transport are restricted, significantly impacting the normal performance of the battery and preventing it from reaching an ideal operating state during the charge-discharge process.

[0048] In some embodiments of the present invention, 0.11 ≤ D / B ≤ 0.43. By limiting the porosity D of the positive electrode active material coating 22 of the positive electrode plate 2 and the porosity B of the second coating 33 of the separator 3 to satisfy 0.11 ≤ D / B ≤ 0.43, the porosity of the positive electrode can be controlled within an appropriate ratio range. Within this ratio range, the positive electrode plate 2 can accommodate more electrolyte with an appropriate porous structure without impairing mechanical strength, providing a sufficient ion transport medium for electrochemical reactions, thereby contributing to an improvement in the energy density of the battery, and ensuring the stability of the electrode plate structure, thereby avoiding the problem of structural loosening caused by excessive porosity. Furthermore, limiting it to 0.11 ≤ D / B ≤ 0.43 also contributes to improving the cycle characteristics of the cell during the charge-discharge process and extending the battery life.

[0049] In some embodiments of the present invention, 0.25 ≤ C / A ≤ 0.67. By limiting the porosity C of the negative electrode active material coating 12 of the negative electrode plate 1 and the porosity A of the first coating 32 of the separator 3 to satisfy 0.25 ≤ C / A ≤ 0.67, the porosity of the negative electrode can be controlled within an appropriate ratio range. Within this ratio range, the negative electrode plate can sufficiently absorb the electrolyte with an appropriate porosity structure without impairing mechanical strength, making the insertion and release of lithium ions in the negative electrode region smoother and contributing to an improvement in the energy density of the battery. Furthermore, by ensuring the stability of the electrode plate structure, the problem of structural loosening caused by excessive porosity can be avoided. In addition, limiting to 0.25 ≤ C / A ≤ 0.67 also contributes to improving the cycle characteristics of the cell during the charge and discharge process and extending the battery life.

[0050] In some embodiments of the present invention, 60% ≤ A ≤ 80%. By limiting the porosity A of the first coating 32 of the separator 3 to 60% ≤ A ≤ 80%, an ideal passage for the distribution and transport of the electrolyte in the negative electrode region can be constructed. This porosity range ensures sufficient voids in the coating, allowing the electrolyte to penetrate and adhere well to the negative electrode active material coating 12, creating favorable conditions for lithium ion insertion and release, and also avoiding the fragility of the coating structure caused by excessively high porosity.

[0051] In some embodiments of the present invention, 0.5 μm ≤ a ≤ 3 μm. By limiting the thickness a of the first coating 32 to 0.5 μm ≤ a ≤ 3 μm, the first coating 32 of the separator 3 can ensure effective ion transport without excessively increasing the ion transport path length, thereby improving the lithium ion conduction efficiency in the negative electrode region and optimizing the electrochemical reaction rate of the negative electrode.

[0052] In some embodiments of the present invention, B is 70% ≤ B ≤ 90%. Limiting the porosity B of the second coating 33 of the separator 3 to 70% ≤ B ≤ 90% creates an excellent environment for the electrolyte to penetrate and distribute in the positive electrode region. This range of porosity ensures that the coating has sufficient void volume to adequately absorb the electrolyte, promotes adhesion with the positive electrode active material coating 22, provides an abundant ion source for lithium ion insertion and release at the positive electrode, avoids the problem of loosening of the coating structure due to excessively high porosity, and ensures the structural stability of the coating in high-potential and strong oxidizing environments.

[0053] In some embodiments of the present invention, 0.5 μm ≤ b ≤ 5 μm. By limiting the thickness b of the second coating 33 of the separator 3 to 0.5 μm ≤ b ≤ 5 μm, the second coating 33 of the separator 3 can ensure effective ion transport without excessively increasing the ion transport path length, thereby improving the lithium ion conduction efficiency in the positive electrode region and optimizing the electrochemical reaction rate of the positive electrode.

[0054] In some embodiments of the present invention, 20% ≤ C ≤ 40%. The porosity C of the negative electrode active material coating 12 is limited to 20% ≤ C ≤ 40%. This range ensures that the negative electrode active material coating 12 has an appropriate porous structure. Sufficient voids allow the electrolyte to penetrate completely, providing sufficient passages for lithium ion insertion and release, and promoting efficient electrochemical reactions. A moderate porosity avoids loosening of the electrode structure due to excessive voids, thereby ensuring the structural stability of the negative electrode active material coating 12 during the charge-discharge process.

[0055] In some embodiments of the present invention, c is 50.5 μm ≤ c ≤ 54 μm. By limiting the thickness c of the negative electrode active material coating 12 to 50.5 μm ≤ c ≤ 54 μm, the migration path of lithium ions within the coating is optimized while maintaining the amount of negative electrode active material supported. With an appropriate thickness, the storage capacity of the active material does not decrease if it is too thin, thus not affecting the battery capacity, and the diffusion distance of lithium ions does not increase if it is too thick, thus not degrading the battery's charge and discharge characteristics. As a result, the electrochemical reaction efficiency in the negative electrode region is effectively improved, and the charge and discharge characteristics of the battery are improved.

[0056] In some embodiments of the present invention, 10% ≤ D ≤ 30%. By limiting the porosity D of the positive electrode active material coating 22 to 10% ≤ D ≤ 30%, an ideal microstructure is constructed in the positive electrode region. The appropriate porosity provides sufficient transport channels for the electrolyte to penetrate the coating sufficiently, allowing lithium ions to be inserted during charging and released during discharge, thereby greatly promoting efficient electrochemical reactions. At the same time, a reasonable number of voids avoids loosening of the electrode structure due to too many voids, ensuring that the positive electrode active material coating 22 maintains a stable structure even under complex environments of high potential and strong oxidation, thereby ensuring the reliability of the cell during charge-discharge cycles.

[0057] In some embodiments of the present invention, 42 μm ≤ d ≤ 46 μm. By limiting the thickness d of the positive electrode active material coating 22 to the range of 42 μm ≤ d ≤ 46 μm, the migration path of lithium ions within the coating is optimized while ensuring a sufficient amount of active material to maintain a high battery capacity. With an appropriate thickness, not only is the problem of reduced storage capacity of the active material and limited battery capacity due to being too thin is avoided, but the diffusion distance of lithium ions is also prevented by being too thick, thus avoiding a decrease in the battery's charge and discharge characteristics, reliably and effectively improving the electrochemical reaction efficiency in the positive electrode region, and significantly improving the battery's charge and discharge characteristics.

[0058] In some embodiments of the present invention, if the pore size of the first coating 32 is Eμm, the pore size of the second coating 33 is Fμm, and the pore size of the substrate 31 is Gμm, then the following conditions are satisfied: 0.1≦E≦2, 0.3≦F≦4, 0.02≦G≦0.08, and F>E>G.

[0059] By limiting the pore size E of the first coating 32 to 0.1 ≤ E ≤ 2 μm, the pore size F of the second coating 33 to 0.3 ≤ F ≤ 4 μm, and the pore size G of the substrate 31 to 0.02 ≤ G ≤ 0.08 μm, while satisfying the relationship F > E > G, the problem of pore clogging can be effectively avoided. Specifically, the larger the pore size of the coating, the smoother the electrolyte penetrates between the separator 3 and the electrode active material coating during the charge-discharge cycle of the cell, ensuring a path for lithium ions to move, avoiding obstruction of ion transport due to pore clogging, and improving the cycle characteristics of the cell.

[0060] By limiting the parameters to 0.1≦E≦2, 0.3≦F≦4, 0.02≦G≦0.08, and F>E>G, good compatibility is achieved between the first coating 32, the second coating 33, and the substrate. The combination of the larger pore size of the coating and the relatively small pore size of the substrate 31 ensures that the coating can adequately absorb and store the electrolyte and provide a sufficient ion source for the electrochemical reaction, while the smaller pore size of the substrate 31 maintains the basic barrier function of the separator and prevents short circuits between the positive and negative electrodes. This coordinated operating mode optimizes the overall characteristics of the separator, enabling the cell to operate safely and stably while achieving efficient energy conversion.

[0061] Optionally, E can be any number satisfying 0.1 ≤ E ≤ 2, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, etc., and is not limited to any specific value.

[0062] Optionally, F can be any number satisfying 0.3 ≤ E ≤ 4, such as 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, etc., and is not limited to any other number.

[0063] Optionally, G can be any number satisfying 0.02 ≤ G ≤ 0.08, such as 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, etc., and is not limited to any specific value.

[0064] In the present invention, the pore diameter of the first coating 32, the pore diameter of the second coating 33, and the pore diameter of the substrate 31 can be measured by the following method. Using a TESCAN VEGA3 scanning electron microscope, in secondary electron imaging mode, with an acceleration voltage of 20kV, a magnification of 5000x, and a scanning range of 25μm × 25μm, 50 micropores are randomly selected from the surface of the coating (or substrate) within this range, the size of the micropores is measured, the pore diameter of the micropore is calculated from the starting point to the ending point (from the starting point to the longest endpoint of the micropore), and the average of the sizes of the 50 micropores is taken as the average pore diameter.

[0065] In some embodiments of the present invention, if the air permeability of the first coating 32 is Js / 100cc and the air permeability of the second coating 33 is Ks / 100cc, then the following conditions are met: 5 ≤ J ≤ 70, 5 ≤ K ≤ 50, and J ≥ K.

[0066] Since a lower permeability of the coating results in a higher porosity, limiting the permeability J of the first coating 32 to 5 ≤ J ≤ 70 s / 100 cc and the permeability K of the second coating 33 to 5 ≤ K ≤ 50 s / 100 cc, while also ensuring that J ≥ K, ensures that the coating has an appropriate porosity. A high porosity allows the first coating 32 and the second coating 33 to absorb the electrolyte sufficiently, providing a sufficient ion transport medium for the electrochemical reaction within the cell. By limiting the permeability J of the first coating 32 and the permeability K of the second coating 33 to have the relationship J ≥ K, the electrolyte environments on both sides of the separator are relatively balanced, reducing ion transport problems caused by excessive differences between the two sides, creating a stable environment for the electrochemical reaction within the cell, improving the cell's cycle stability, and extending the battery's lifespan.

[0067] J can be any number that satisfies 5 ≤ ​​J ≤ 70, such as 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, or 70, and is not limited to any specific value.

[0068] K can be any number that satisfies 5 ≤ ​​K ≤ 50, such as 5, 6, 7, 8, 9, 10, 20, 30, 40, or 50, and is not limited to any specific value.

[0069] The aforementioned air permeability can be measured by the following method. First, the substrate is placed in a test machine (air permeability test machine manufactured by Asahi Seiko Co., Ltd.), and 100 ml of gas is pushed from one gas chamber to the other at a constant pressure (e.g., 0.05 MPa), and the time it takes for the gas to pass through is recorded as S1. Next, the separator with the coating applied to the substrate is measured using the above method, and the time it takes for the gas to pass through is recorded as S2. The air permeability S of the coating is given by S = S2 - S1. For example, the first coating 32 is applied to the substrate, and the gas passage time is obtained by measuring using the above method, and this is recorded as S 21 In this case, the air permeability of the first coating 32 is S 21 - This becomes S1. The second coating 33 is applied to the substrate 31, and the gas permeation time is obtained by measuring it using the method described above, and this is S 22 In that case, the air permeability of the second coating 33 is S 22 -S1

[0070] In some embodiments of the present invention, the substrate 31 includes, but is not limited to, one or more of polyethylene, polypropylene, polyimide, and polyethylene terephthalate.

[0071] The first coating 32 consists of a first organic polymer and a first inorganic material.

[0072] The second coating 33 consists of a second organic polymer and a second inorganic material.

[0073] In some embodiments of the present invention, the first organic polymer may include, but is not limited to, one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metharamid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate.

[0074] In some embodiments of the present invention, the first inorganic material may include, but is not limited to, one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate.

[0075] In some embodiments of the present invention, the second organic polymer may include, but is not limited to, one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metharamid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate.

[0076] In some embodiments of the present invention, the second inorganic material may include, but is not limited to, one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate.

[0077] In some embodiments of the present invention, the mass ratio of the first organic polymer to the first inorganic material is (0-9.5):1, and the mass ratio of the second organic polymer to the second inorganic material is (0-9.5):1.

[0078] In some embodiments of the present invention, the first inorganic material comprises first inorganic particles, and the second inorganic material comprises second inorganic particles. If the average particle diameter of the first inorganic particles is Hμm and the average particle diameter of the second inorganic particles is Iμm, then the following conditions are satisfied: 0.2≦H≦0.8, 0.4≦I≦1.5, and I≧H.

[0079] The larger the particle size of the inorganic particles in the coating, the more likely the porosity of the coating is to increase. In this invention, the average particle size H of the first inorganic particles is limited to 0.2 ≤ H ≤ 0.8 μm, and the average particle size I of the second inorganic particles is limited to 0.4 ≤ I ≤ 1.5 μm, and I ≥ H. From the perspective of the difference between the positive electrode reaction and the negative electrode reaction, the positive electrode reaction is more complex. During charging, lithium ions are released from the positive electrode, but this process involves complex oxidation-reduction reactions, placing high demands on electrolyte consumption and ion transport rate. The second inorganic particles, having a larger particle size, can construct a richer and larger void network in the second coating 33, store more electrolyte, and continuously supply lithium ions to the positive electrode region, thereby meeting the high demand for ion transport. The negative electrode reaction is relatively simple. The void structure formed by the small-particle-diameter first inorganic particles in the first coating 32 can meet the anode's demands for electrolyte adsorption and ion transport, avoiding problems such as the shedding of anode active material due to excessive voids, and ensuring the stability of the anode structure.

[0080] In the present invention, the average particle diameter of inorganic particles can be measured by the following method. Using a TESCAN VEGA3 scanning electron microscope, in secondary electron imaging mode, with an acceleration voltage of 20kV, a magnification of 5000x, and a scanning range of 25μm × 25μm, 50 particles are randomly selected within this range, their size is measured, the particle size is calculated from the starting point to the ending point of the particle (from the starting point to the longest endpoint of the particle), and the average of the sizes of the 50 particles is taken as the average particle diameter. Second aspect

[0081] The present invention also provides a battery comprising a cell as described in any one of the above paragraphs, further comprising a case and an electrolyte, wherein both the cell and the electrolyte are provided within the case.

[0082] Third aspect The present invention also provides a method for manufacturing a battery as described in any one of the above claims, the manufacturing method comprising the steps of manufacturing a positive electrode plate 2, manufacturing a negative electrode plate 1, manufacturing a separator 3, manufacturing an electrolyte, and manufacturing a battery. The steps for manufacturing the positive electrode plate 2 include thoroughly stirring lithium cobalt oxide, acetylene black, and polyvinylidene fluoride in an N-methylpyrrolidone solvent system to obtain a homogeneous mixture, coating it onto the positive electrode current collector 21, drying, cold pressing, and slitting to obtain the positive electrode plate 2. The steps for manufacturing the negative electrode plate 1 include thoroughly stirring artificial graphite, acetylene black, styrene-butadiene rubber as a binder, and sodium carboxymethylcellulose as a thickener in a deionized aqueous solvent system to obtain a homogeneous mixture, coating the mixture onto the negative electrode current collector 11, drying, cold pressing, and slitting to obtain the negative electrode plate 1. The steps for manufacturing the separator 3 include applying a first coating 32 to one surface of the substrate 31 and applying a second coating 33 to the other surface of the substrate 31. The step of preparing the electrolyte includes preparing a solution containing a lithium salt and a non-aqueous organic solvent as the electrolyte. The steps for manufacturing a battery include sequentially stacking a negative electrode plate 1, a separator 3, and a positive electrode plate 2 to create a cell by a winding or lamination process, placing the cell in a case, injecting electrolyte into the case and sealing it, and obtaining a battery.

[0083] Using the battery manufacturing method described above, batteries of six examples and six comparative examples were manufactured. In the step of manufacturing the positive electrode plate 2, the mass ratio of lithium cobalt oxide, acetylene black, and polyvinylidene fluoride was 95:3:2. In the step of manufacturing the negative electrode plate 1, the mass ratio of artificial graphite, acetylene black, styrene-butadiene rubber (binder), and sodium carboxymethylcellulose (thickener) was 96:1:1.5:1.5. In the step of manufacturing the electrolyte, the mass ratio of lithium salt to non-aqueous organic solvent was 8:92. The non-aqueous organic solvent was prepared using 20 parts by weight of ethylene carbonate, 30 parts by weight of diethyl carbonate, 20 parts by weight of propylene carbonate, 28 parts by weight of propyl propionate, and 2 parts by weight of vinylene carbonate as raw materials. In the step of manufacturing the battery, the negative electrode plate 1, separator 3, and positive electrode plate 2 were stacked in order, and a cell was manufactured by a winding process.

[0084] The batteries in the six examples and six comparative examples differ only in the values ​​of A, a, B, b, C, c, D, and d. The specific data for the six examples and six comparative examples are shown in Table 1 below.

[0085] [Table 1]

[0086] The C / A, D / B, and [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] for Examples 1-6 and Comparative Examples 1-6 obtained from the specific data in Table 1 are shown in Table 2 below.

[0087] [Table 2]

[0088] As can be seen from Table 2, all of Examples 1 to 6 satisfy the three conditions: 0.25 ≤ C / A ≤ 0.67, 0.11 ≤ D / B ≤ 0.43, and 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2.

[0089] Comparative Example 1 does not satisfy the two conditions 0.11 ≤ D / B ≤ 0.43 and 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2.

[0090] Comparative Examples 2 and 6 do not satisfy the condition 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2.

[0091] Comparative Examples 3 and 4 do not satisfy the condition 0.25 ≤ C / A ≤ 0.67.

[0092] Comparative Example 5 does not satisfy the two conditions 0.25 ≤ C / A ≤ 0.67 and 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2.

[0093] The test method for the battery's room-temperature cycle characteristics is as follows: Perform the initial charge and discharge in a 25°C environment. Charge at a constant current and voltage of 0.1C (the current value at which the theoretical capacity is completely discharged within 10 hours) until the upper voltage reaches 4.3V. Then, discharge at a constant current of 1C until the cutoff voltage reaches 3V, and record the discharge capacity of the first cycle. Subsequently, perform 100 charge-discharge cycles and record the discharge capacity at the 100th cycle.

[0094] The cycle capacity retention rate at 200 cycles = (discharge capacity at 200 cycles / discharge capacity at 1 cycle) × 100%, at 400 cycles = (discharge capacity at 400 cycles / discharge capacity at 1 cycle) × 100%, at 600 cycles = (discharge capacity at 600 cycles / discharge capacity at 1 cycle) × 100%, and at 800 cycles = (discharge capacity at 800 cycles / discharge capacity at 1 cycle) × 100%.

[0095] The test samples were set up as five parallel sample groups, and the final test results were statistically calculated as the average of the five parallel sample groups.

[0096] The batteries of Examples 1-6 and Comparative Examples 1-6 were tested using the room temperature cycle characteristic test method described above. The specific test results are shown in Table 3 below.

[0097] [Table 3]

[0098] As can be seen from Tables 1 to 3, when a battery cell satisfies the three conditions 0.25 ≤ C / A ≤ 0.67, 0.11 ≤ D / B ≤ 0.43, and 0.8 ≤ [(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)] ≤ 1.2, the cell's cycle characteristics are significantly improved, and the battery's stability and reliability during long-term use are enhanced.

[0099] The above describes only preferred embodiments of the present invention. Those skilled in the art will understand that various improvements and substitutions are possible without departing from the technical principles of the present invention. These improvements and substitutions are also covered within the scope of the present invention. [Explanation of Symbols]

[0100] 1. Negative electrode plate 11 Negative electrode current collector 12. Negative electrode active material coating 2 Positive plate 21 Positive electrode current collector 22 Positive electrode active material coating 3 Separators 31 Base material 32. First Coating 33. Second Coating

Claims

1. It is a cell, It includes a negative electrode plate, a separator, and a positive electrode plate, which are stacked in order. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material coating, wherein the negative electrode active material coating is applied to the surface of the negative electrode current collector facing the separator. The positive electrode plate includes a positive electrode current collector and a positive electrode active material coating, wherein the positive electrode active material coating is applied to the surface of the positive electrode current collector facing the separator. The separator comprises a substrate, a first coating, and a second coating, wherein the first coating is applied to the surface of the substrate facing the negative electrode plate and is in contact with the negative electrode active material coating, and the second coating is applied to the surface of the substrate opposite to the first coating and is in contact with the positive electrode active material coating. If the porosity of the first coating is A, the thickness of the first coating is a μm, the porosity of the second coating is B, the thickness of the second coating is b μm, the porosity of the negative electrode active material coating is C, the thickness of the negative electrode active material coating is c μm, the porosity of the positive electrode active material coating is D, the thickness of the positive electrode active material coating is d μm, the pore diameter of the first coating is E μm, the pore diameter of the second coating is F μm, and the pore diameter of the substrate is G μm, then 0.8≦[(Dd+Bb) / (b+d)] / [(Aa+Cc) / (a+c)]≦1.2, 60% ≤ A ≤ 80%, 0.5 μm ≤ a ≤ 3 μm, 70% ≤ B ≤ 90%, 0.5 μm ≤ b ≤ 5 μm, 20% ≤ C ≤ 40%, 50.5 μm ≤ c ≤ 54 μm, 10% ≤ D ≤ 30%, 42 μm ≤ d ≤ 46 μm, A cell characterized by satisfying 0.1 ≤ E ≤ 2, 0.3 ≤ F ≤ 4, 0.02 ≤ G ≤ 0.08, and F > E > G.

2. The cell according to claim 1, characterized in that 0.25 ≤ C / A ≤ 0.

67.

3. The cell according to claim 1, characterized in that 0.11 ≤ D / B ≤ 0.

43.

4. The cell according to claim 1, characterized in that, if the air permeability of the first coating is Js / 100cc and the air permeability of the second coating is Ks / 100cc, then 5 ≤ J ≤ 70, 5 ≤ K ≤ 50, and J ≥ K.

5. The aforementioned substrate includes one or more of polyethylene, polypropylene, polyimide, and polyethylene terephthalate. The first coating described above consists of a first organic polymer and a first inorganic material. The second coating described above consists of a second organic polymer and a second inorganic material. The first organic polymer includes one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metharamid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate. The first inorganic material is one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate. The second organic polymer includes one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, polyacrylonitrile, polyetherimide, polyamide, metaaramid, paraaramid, polymethyl methacrylate, polyethylene, styrene-butadiene rubber, and polyacrylate. The cell according to claim 1, characterized in that the second inorganic material is one or more of the following: alumina, magnesium oxide, silicon oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, zeolite, and calcium carbonate.

6. The mass ratio of the first organic polymer to the first inorganic material is (0 to 9.5):

1. The cell according to claim 5, characterized in that the mass ratio of the second organic polymer to the second inorganic material is (0 to 9.5):

1.

7. The first inorganic material comprises first inorganic particles, and the second inorganic material comprises second inorganic particles. The cell according to claim 5, characterized in that, if the average particle diameter of the first inorganic particles is H μm and the average particle diameter of the second inorganic particles is I μm, then 0.2 ≤ H ≤ 0.8, 0.4 ≤ I ≤ 1.5, and I ≥ H.

8. It is a battery, A battery comprising a cell according to any one of claims 1 to 7, further comprising a case and an electrolyte, wherein both the cell and the electrolyte are provided within the case.

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