Secondary battery, separator, and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a secondary battery, a diaphragm and an electric device. The secondary battery comprises a positive pole piece, a negative pole piece and a diaphragm; the diaphragm comprises a base membrane, a surface coating is arranged on one side, facing the negative pole piece, of the base membrane, and a gap is formed in the surface of one side, facing the negative pole piece, of the surface coating. The diaphragm comprises the base membrane, the surface coating is arranged on one side, facing the negative pole piece, of the base membrane, and the gap is formed in the surface of one side, facing the negative pole piece, of the surface coating and provides a space for deposition of metal on the negative pole side, so that the risk of cell expansion caused by deposition of active ions on the negative pole is reduced, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a secondary battery, a separator, and an electrical device. Background Technology

[0002] Secondary batteries, such as lithium-ion batteries, have attracted much attention due to their high specific energy, long cycle life, low self-discharge, and good safety performance. Currently, lithium-ion batteries are used in all aspects of daily life, such as cameras, laptops, and electric vehicles.

[0003] In some cases, secondary batteries may expand in volume during cycling, which reduces the battery's cycle performance. Summary of the Invention

[0004] The main objective of this application is to provide a secondary battery that aims to improve the cycle performance of the secondary battery.

[0005] To achieve the above objectives, this application proposes a secondary battery, which includes a positive electrode, a negative electrode, and a separator.

[0006] The diaphragm includes a base membrane, and the base membrane has a surface coating on the side facing the negative electrode sheet. The surface coating has voids on the side facing the negative electrode sheet.

[0007] The separator in this application includes a base film, and a surface coating is provided on the side of the base film facing the negative electrode. The surface of the surface coating facing the negative electrode has voids, which provide space for the deposition of metal on the negative electrode side, reduce the risk of cell expansion caused by the deposition of active ions on the negative electrode, and improve the cycle performance of the battery.

[0008] It is understandable that the metal on the negative electrode side needs space to grow during the deposition process. If the deposition space is insufficient, the deposited metal will cause the battery to expand. For example, due to insufficient deposition space, the metal on the negative electrode side will form a deposition layer between the negative electrode and the separator, squeezing the separator. The metal dendrites in the deposition layer exert pressure on the separator, which can easily lead to the risk of puncturing the separator and causing a short circuit between the positive and negative electrodes. Alternatively, the deposition layer may exert large compressive stress on the separator, causing the separator to be over-compressed, reducing the permeability of active ions in the separator, increasing the internal resistance of the battery, and thus affecting the battery's cycle performance. To alleviate the above problems, a surface coating is set on the side of the base film facing the negative electrode. The surface of the surface coating facing the negative electrode has gaps for metal deposition. In this way, the risk of cell expansion caused by the deposition of active ions on the negative electrode is reduced, and the battery's cycle performance is improved.

[0009] Optionally, the particle size Dv50 of the particles in the surface coating is from 13 μm to 30 μm.

[0010] It is understandable that there are gaps between particles, and as the particle size increases, the gaps between particles also increase. This application creates these gaps on the surface of the surface coating by adjusting the particle size of the particles in the coating layer. The particle size affects the size of these gaps. It is understandable that if the particle size in the surface coating layer is too small, the gap space on the surface coating layer is insufficient, making it difficult to meet the space required for metal growth; if the particle size in the surface coating layer is too large, it will cause uneven metal deposition and reduce the volumetric energy density of the battery. In this application, the particle size in the surface coating layer meets the above-mentioned range, which helps to provide more gaps for metal growth on the negative electrode side and also promotes uniform metal deposition.

[0011] It is understandable that uneven metal deposition on the negative electrode side is more likely to cause the growth of longer dendrites, which can easily lead to the risk of short circuit caused by the puncture of the separator. The appropriate particle size in the coating of this application can reduce the risk of short circuit in the battery.

[0012] Optionally, the particle size Dv50 of the particles in the surface coating is d, in μm;

[0013] The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The capacity of the positive electrode active material per unit area on one surface of the positive electrode coating is Q, with units of mAh / m³. 2 ;

[0014] The condition d and Q satisfy: 0.6Q≤d≤1.9Q.

[0015] It is understandable that the capacity on the positive electrode side determines the space for metal growth on the negative electrode side. For example, under certain conditions, the more positive electrode active material on the positive electrode side, the more active ions are provided on the positive electrode side, and the more metal will be deposited on the negative electrode side. At the same time, the particle size in the coating affects the size of the gaps for metal growth; that is, the particle size in the coating is related to the capacity on the positive electrode side. In this application, the particle size Dv50 of the surface coating is d, in μm. The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The capacity of the positive electrode active material per unit area on one surface of the positive electrode coating is Q, in mAh / m³. 2 d and Q satisfy: 0.6Q≤d≤1.9Q. Based on the above logic, this application provides the above relationship. The secondary battery separator that satisfies the above relationship has suitable gaps for metal growth on the negative electrode side, reducing the risk of battery expansion.

[0016] Optionally, the morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes.

[0017] Understandably, a quasi-spherical surface refers to a shape similar to a sphere, where every part of the spherical surface is equidistant from the center. However, some parts of the quasi-spherical surface may have distances greater or less than r from the center. The particles in the surface coating are spherical or quasi-spherical, and the width of the voids tends to increase along the direction of the surface coating. These voids provide space for the deposition of metal on the negative electrode side. Simultaneously, the width of these voids also tends to increase along the direction of the surface coating, thus facilitating the return of metal to the positive electrode during battery discharge.

[0018] It is also understandable that the morphology of particles in the surface coating can be island-like, which refers to the presence of protrusions or bumps on the particle surface, such as the morphology of multiple particles agglomerated. The morphology of particles in the surface coating can also be columnar.

[0019] Optionally, the material of the particles in the surface coating includes organic polymers and / or inorganic materials.

[0020] It is understandable that the particles in the surface coating can be made of organic polymers, inorganic materials, or a mixture of organic polymers and inorganic materials. For example, including inorganic materials in the surface coating can improve the overall mechanical strength and thermal insulation of the membrane, while organic polymers in the surface coating have adhesive properties, which helps to bond the surface coating to the base membrane surface.

[0021] Optionally, the particles in the surface coating are binders.

[0022] Understandably, all the particles in the surface coating are binders. The binder helps to ensure that the negative electrode sheet and the separator are tightly bonded together, reducing the risk of misalignment between the separator and the negative electrode sheet after metal deposition on the negative electrode side.

[0023] Optionally, the mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 ;

[0024] And / or, the adhesive material includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, polymethyl methacrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

[0025] It is understandable that the mass of binder per unit area in the surface coating meets the above range, which helps to form a uniformly dispersed binder layer, so that the binder particles are evenly distributed, reducing agglomeration, and forming a uniform void distribution between the binder particles, which helps to improve the uniformity of metal deposition on the negative electrode side.

[0026] It is understood that the binder materials include at least one of polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose, and polyacrylic acid. These binder materials have low deformation resistance. When stress is generated inside the battery, the binder particles in the surface coating can better resist deformation, reducing the problem of the gaps between binder particles being squeezed and reduced during deformation.

[0027] Optionally, a base coating layer is further provided between the base film and the surface coating layer.

[0028] Understandably, the base coating is a layered structure placed close to the base membrane. The base coating can provide functions for the diaphragm, such as improving the diaphragm's heat resistance, puncture resistance, or adhesion.

[0029] Optionally, the base coating includes ceramic particles;

[0030] And / or, the base coating includes binder particles.

[0031] In one embodiment, when the base coating includes ceramic particles, the mechanical strength of the diaphragm can be improved, thus enhancing its puncture resistance. In another embodiment, the base coating includes binder particles, which facilitates adhesion of the top coating to the base coating.

[0032] Optionally, the mass percentage of ceramic particles in the base coating is 30% to 70% based on the total mass of the base coating.

[0033] And / or, the particle size Dv50 of the particles in the undercoat is from 0.01 μm to 2.0 μm;

[0034] And / or, the material of the ceramic particles includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, and zirconium dioxide;

[0035] And / or, the thickness of the base coating on one side is 0.5 μm to 3.0 μm.

[0036] Considering that the adhesion of pure ceramic particles in the base coating is insufficient, a binder can be added to the base coating. In order to improve the mechanical strength of the base coating, the mass percentage of ceramic particles in the base coating, based on the total mass of the base coating, should meet the above-mentioned range.

[0037] To improve the puncture resistance of the base coating, the particle size of the particles in the base coating meets the above-mentioned range, so that smaller voids are formed in the base coating, reducing the risk of metal dendrites puncturing the diaphragm.

[0038] The thickness of the base coating meets the above range, and the diaphragm has good puncture resistance and heat resistance.

[0039] Optionally, the compression ratio of the diaphragm is T1, which satisfies: 12% ≤ T1 ≤ 22%.

[0040] In this application, the separator is compressible, and its compressibility comes from the base membrane. The compressible separator can reduce the stress when the negative electrode expands and improve the overall cycle performance of the cell.

[0041] The diaphragm's compression ratio meets the above range, which ensures that the diaphragm has good compressibility without being compressed too thin, thus helping to isolate the positive and negative electrodes.

[0042] Optionally, the initial thickness of the base film is H, which satisfies 6μm≤H≤25μm.

[0043] The initial thickness of the base membrane refers to the thickness of the membrane before it is compressed, that is, the thickness of the base membrane in its natural state. The base membrane meets the above initial thickness so that the membrane can maintain a suitable thickness range after being compressed, thus providing the function of the membrane to isolate the positive and negative electrodes.

[0044] Optionally, the initial thickness H of the base film, the compression ratio T1 of the separator, and the capacity Q of the positive active material per unit area of ​​one surface of the positive electrode coating in the positive electrode sheet satisfy: 0.6Q≤H×T1≤1.9Q.

[0045] It is understandable that the initial thickness H of the base film, the compression ratio T1 of the separator, and the capacity Q of the active material per unit area of ​​the coating on the positive electrode side satisfy the above relationship. That is, the capacity of the positive electrode active material on the positive electrode side is related to the amount of metal deposited on the negative electrode side. The larger the capacity of the positive electrode active material on the positive electrode side, the greater the amount of metal deposited on the negative electrode side will be within a certain range. After the metal on the negative electrode side grows to a certain thickness, it will compress the separator. During the process of generating extrusion force, the base film will be compressed. The metal deposited on the negative electrode can be located in the space formed by the compression, reducing the risk of cell expansion. At the same time, the base film can be compressed, which weakens the piercing force between the metal dendrites and the separator, reducing the risk of metal dendrites piercing the separator.

[0046] Optionally, the base film is made of at least one of polyethylene, polypropylene, nonwoven fabric and polyimide;

[0047] And / or, the porosity of the base membrane is 30% to 70%.

[0048] The base film material includes at least one of polyethylene, polypropylene, nonwoven fabric and polyimide.

[0049] A porosity within the aforementioned range helps achieve compressibility while ensuring good air permeability, which facilitates ion transport.

[0050] Optionally, the secondary battery is a metal battery.

[0051] Metal batteries are metal deposition type batteries. In metal batteries, active ions are deposited at the negative electrode. For example, taking lithium metal batteries as an example, lithium metal batteries directly use lithium metal as the negative electrode. Lithium ions gain electrons on the surface of the lithium metal electrode and are reduced to elemental lithium and precipitated.

[0052] Metal batteries are at greater risk of swelling. Applying the above-mentioned separator to metal batteries can effectively improve the swelling problem and improve the cycle performance of the battery.

[0053] Optionally, the metal battery includes a lithium metal battery, a sodium metal battery, an aluminum metal battery, and a zinc metal battery;

[0054] And / or, the secondary battery includes stacked batteries, square batteries, cylindrical batteries, and pouch batteries.

[0055] In one embodiment, the metal battery includes lithium metal batteries, sodium metal batteries, aluminum metal batteries, zinc metal batteries, etc. In another embodiment, the secondary battery includes stacked batteries, prismatic batteries, cylindrical batteries, and pouch batteries.

[0056] Optionally, this application also provides a diaphragm, the diaphragm comprising a base membrane, wherein at least one side of the base membrane is provided with a surface coating, and the surface of the surface coating has voids.

[0057] Optionally, the particle size Dv50 of the particles in the surface coating is from 13 μm to 30 μm.

[0058] Optionally, the morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes;

[0059] And / or, the particles in the surface coating are a binder.

[0060] Optionally, the mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 ;

[0061] And / or, the adhesive material includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, polymethyl methacrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

[0062] Optionally, the compression ratio of the diaphragm is T1, which satisfies: 12% ≤ T1 ≤ 22%;

[0063] And / or, the initial thickness of the base film is H, satisfying 6μm≤H≤25μm.

[0064] Optionally, this application also provides an electrical device, which includes a secondary battery as described above.

[0065] The secondary battery of this application includes a positive electrode, a negative electrode, and a separator; the separator includes a base film, and a surface coating is provided on the side of the base film facing the negative electrode. The surface coating has voids on the side of the surface coating facing the negative electrode. The voids provide space for the deposition of metal on the negative electrode side, reduce the risk of cell expansion caused by the deposition of active ions on the negative electrode, and improve the cycle performance of the battery. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0067] Figure 1 This is a schematic diagram of the diaphragm structure according to an embodiment of this application;

[0068] Figure 2 This is a schematic diagram of the diaphragm structure according to another embodiment of this application;

[0069] Figure 3 This is a schematic diagram of the diaphragm structure according to another embodiment of this application;

[0070] Figure 4 This is a schematic diagram of the structure of the diaphragm and negative electrode sheet stacked in an embodiment of this application;

[0071] Figure 5 This is a schematic diagram of the structure of metal deposition on the negative electrode side and compression of the base film in an embodiment of this application;

[0072] Figure 6 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0073] Figure 7 yes Figure 6 An exploded view of a battery cell according to one embodiment of this application is shown.

[0074] Figure 8 This is a schematic diagram of a battery module according to one embodiment of this application;

[0075] Figure 9 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0076] Figure 10 yes Figure 9 An exploded view of a battery pack according to one embodiment of this application is shown;

[0077] Figure 11This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0078] Explanation of icon numbers:

[0079]

[0080]

[0081] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0082] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0083] The secondary battery, separator, and power supply device of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0084] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0085] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0086] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0087] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0088] In some cases, secondary batteries may expand in volume during cycling, which can reduce the battery's cycle performance.

[0089] For example, with the rapid development of electric vehicles, the demand for batteries with higher power density and faster charging speed has risen sharply. Among them, metal batteries without negative electrodes eliminate the traditional negative electrode components in the battery, which is expected to realize a breakthrough energy storage method. However, correspondingly, due to the deposition of negative electrode metal during the charging process, the battery expansion is also greatly worse than that of traditional batteries, thus reducing the cycle performance of the battery.

[0090] For example, taking metal batteries as an example, metal batteries are metal deposition type batteries, where metal ions are deposited on the negative electrode side as metal elements, causing the cell volume to expand. Therefore, it is necessary to reduce the performance degradation caused by cell expansion.

[0091] This application proposes a secondary battery, which includes a positive electrode, a negative electrode, and a separator; the separator includes a base film, and a surface coating is provided on the side of the base film facing the negative electrode, and the surface coating has voids on the side of the surface coating facing the negative electrode.

[0092] The surface coating refers to the coating structure applied to the surface of the base film.

[0093] The surface of the coating layer facing the negative electrode has voids. These voids are directly connected to the surface of the coating layer, allowing material from the surface to enter. Located on the negative electrode side of the coating layer, these voids facilitate the inclusion of material from the negative electrode side into these voids. Figure 1 As shown, the surface coating 20 has a void 201 that is connected to the surface of the surface coating, so that the material on the surface of the surface coating 20 can be accommodated in the void 201.

[0094] The separator in this application includes a base film, and a surface coating is provided on the side of the base film facing the negative electrode. The surface of the surface coating facing the negative electrode has voids, which provide space for the deposition of metal on the negative electrode side, reduce the risk of cell expansion caused by the deposition of active ions on the negative electrode, and improve the cycle performance of the battery.

[0095] It is understandable that the metal on the negative electrode side needs space to grow during the deposition process. If the deposition space is insufficient, the deposited metal will cause the battery to expand. For example, due to insufficient deposition space, the metal on the negative electrode side will form a deposition layer between the negative electrode and the separator, squeezing the separator. The metal dendrites in the deposition layer exert pressure on the separator, which can easily lead to the risk of puncturing the separator and causing a short circuit between the positive and negative electrodes. Alternatively, the deposition layer may exert large compressive stress on the separator, causing the separator to be over-compressed, reducing the permeability of active ions in the separator, increasing the internal resistance of the battery, and thus affecting the battery's cycle performance. To alleviate the above problems, a surface coating is set on the side of the base film facing the negative electrode. The surface of the surface coating facing the negative electrode has gaps for metal deposition. In this way, the risk of cell expansion caused by the deposition of active ions on the negative electrode is reduced, and the battery's cycle performance is improved.

[0096] In one embodiment, the particle size Dv50 of the particles in the surface coating is 13 μm to 30 μm.

[0097] Dv50 is the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than Dv50, and 50% are smaller than Dv50.

[0098] Dv50 can be tested using methods known in the art. As an example, GB / T19077-2016 can be referenced for characterization testing using a Malvern laser particle size analyzer, such as the Malvern Mastersizer-3000. For instance, particles in the surface coating of the base film can be peeled off to test its Dv50.

[0099] Test method and steps for particle size in the top coating of the base film: Disassemble the battery to obtain the separator, use cryo-ion beam cutting technology to obtain the cross-section of the separator, use scanning electron microscope (SEM) to test the particle size of the particles at the separator cross-section, randomly select 20 to 100 particles and test their Dv50.

[0100] It is understandable that gaps exist between particles, and these gaps increase with particle size. This application creates these gaps on the surface of the coating by adjusting the particle size of the particles in the coating layer. The particle size affects the size of these gaps. If the particle size is too small, the surface space of the coating layer will be insufficient, making it difficult to provide the space required for metal growth. If the particle size is too large, it will cause uneven metal deposition and reduce the volumetric energy density of the battery. In this application, the particle size in the coating layer meets the above-mentioned range, which helps to provide more gaps for metal growth on the negative electrode side and also promotes uniform metal deposition. It is understood that uneven metal deposition on the negative electrode side is more likely to cause the growth of longer dendrites, which can easily lead to the risk of short circuits caused by puncturing the separator. The appropriate particle size in the coating layer of this application can reduce the risk of short circuits in the battery.

[0101] like Figures 1 to 5 As shown, the surface of the base film 10 is provided with a surface coating 20, and there are gaps 201 between the particles on the surface of the surface coating 20. During the deposition of the negative electrode, the metal can be deposited in the gaps 201.

[0102] The values ​​in the range of 13μm to 30μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 13μm, 15μm, 18μm, 20μm, 21μm, 25μm, 30μm, etc., and the range values ​​between any two of the above point values.

[0103] In one embodiment, the particle size Dv50 of the particles in the surface coating is d, in μm; the positive electrode includes a positive current collector and a positive coating disposed on at least one surface of the positive current collector, and the capacity of the positive active material per unit area of ​​one surface of the positive coating is Q, in mAh / m³. 2 ; d and Q satisfy: 0.6Q≤d≤1.9Q.

[0104] Test method and steps for the capacity of positive electrode active material in positive electrode sheet: Taking lithium metal battery as an example, the positive electrode sheet is punched into small round pieces, and assembled into a coin cell with lithium sheet, separator and electrolyte. The discharge capacity can be obtained by charging and discharging according to 0~100% SOC. This discharge capacity is the capacity of positive electrode active material.

[0105] It is understandable that the capacity on the positive electrode side determines the space for metal growth on the negative electrode side. For example, under certain conditions, the more positive electrode active material on the positive electrode side, the more active ions are provided on the positive electrode side, and the more metal will be deposited on the negative electrode side. At the same time, the particle size in the coating affects the size of the gaps for metal growth; that is, the particle size in the coating is related to the capacity on the positive electrode side. In this application, the particle size Dv50 of the surface coating is d, in μm. The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The capacity of the positive electrode active material per unit area on one surface of the positive electrode coating is Q, in mAh / m³. 2 d and Q satisfy: 0.6Q≤d≤1.9Q. Based on the above logic, this application provides the above relationship. The secondary battery separator that satisfies the above relationship has suitable gaps for metal growth on the negative electrode side, reducing the risk of battery expansion.

[0106] In one embodiment, the morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes.

[0107] Understandably, a quasi-spherical surface refers to a shape similar to a sphere, where every part of the spherical surface is equidistant from the center. However, some parts of the quasi-spherical surface may have distances greater or less than r from the center. The particles in the surface coating are spherical or quasi-spherical, and the width of the voids tends to increase along the direction of the surface coating. These voids provide space for the deposition of metal on the negative electrode side. Simultaneously, the width of these voids also tends to increase along the direction of the surface coating, thus facilitating the return of metal to the positive electrode during battery discharge.

[0108] It is also understandable that the morphology of particles in the surface coating can be island-like, which refers to the presence of protrusions or bumps on the particle surface, such as the morphology of multiple particles agglomerated. The morphology of particles in the surface coating can also be columnar.

[0109] In one embodiment, the material of the particles in the surface coating includes organic polymers and / or inorganic materials.

[0110] It is understandable that the particles in the surface coating can be made of organic polymers, inorganic materials, or a mixture of organic polymers and inorganic materials. For example, including inorganic materials in the surface coating can improve the overall mechanical strength and thermal insulation of the membrane, while organic polymers in the surface coating have adhesive properties, which helps to bond the surface coating to the base membrane surface.

[0111] For example, the organic polymers in the surface coating include, but are not limited to, at least one of the following: copolymers of vinylidene fluoride-hexafluoropropylene, copolymers of vinylidene fluoride-trichloroethylene, polyacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, copolymers of ethylene and vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, copolymers of acrylonitrile-styrene-butadiene, polyvinyl alcohol, copolymers of styrene-butadiene, and polyvinylidene fluoride.

[0112] The inorganic materials in the surface coating include, but are not limited to, at least one of the following: silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, and barium titanate.

[0113] In one embodiment, the particles in the surface coating are a binder.

[0114] Understandably, all the particles in the surface coating are binders. The binder helps to ensure that the negative electrode sheet and the separator are tightly bonded together, reducing the risk of misalignment between the separator and the negative electrode sheet after metal deposition on the negative electrode side.

[0115] In one embodiment, the mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 In one embodiment, the adhesive material includes at least one selected from polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl methacrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

[0116] It is understandable that the mass of binder per unit area in the surface coating meets the above range, which helps to form a uniformly dispersed binder layer, so that the binder particles are evenly distributed, reducing agglomeration, and forming a uniform void distribution between the binder particles, which helps to improve the uniformity of metal deposition on the negative electrode side.

[0117] It is understood that the binder materials include at least one of polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose, and polyacrylic acid. These binder materials have low deformation resistance. When stress is generated inside the battery, the binder particles in the surface coating can better resist deformation, reducing the problem of the gaps between binder particles being squeezed and reduced during deformation.

[0118] The above 0.4g / m 2 Up to 1.8g / m 2 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 0.4 g / m 2 0.5g / m 2 0.8g / m 2 1g / m 2 1.4g / m 2 1.7g / m 2 1.8g / m 2 And so on, as well as the range of values ​​between any two of the above point values.

[0119] In one embodiment, a base coating layer is further provided between the base film and the top coating layer.

[0120] Understandably, the base coating is a layered structure placed close to the base membrane. The base coating can provide functions for the diaphragm, such as improving the diaphragm's heat resistance, puncture resistance, or adhesion.

[0121] like Figure 3 As shown, a base coating 30 is provided on the surface of the base film 10, and a top coating 20 is provided on the surface of the base coating 30. For example... Figure 4 As shown, the structure is such that the diaphragm and the negative electrode 40 are arranged adjacent to each other. The side with the surface coating 20 is in contact with the negative electrode, which helps the metal on the negative side to be deposited in the gaps on the surface of the surface coating.

[0122] In one embodiment, the primer layer includes ceramic particles; in another embodiment, the primer layer includes binder particles.

[0123] In one embodiment, when the base coating includes ceramic particles, the mechanical strength of the diaphragm can be improved, thus enhancing its puncture resistance. In another embodiment, the base coating includes binder particles, which facilitates adhesion of the top coating to the base coating.

[0124] In one embodiment, the ceramic particles in the base coating constitute 30% to 70% of the total mass of the base coating; in one embodiment, the particle size Dv50 of the particles in the base coating is 0.01 μm to 2.0 μm; in one embodiment, the material of the ceramic particles includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, and zirconium dioxide; in one embodiment, the single-sided thickness of the base coating is 0.5 μm to 3.0 μm.

[0125] Considering that the adhesion of pure ceramic particles in the base coating is insufficient, a binder can be added to the base coating. In order to improve the mechanical strength of the base coating, the mass percentage of ceramic particles in the base coating, based on the total mass of the base coating, should meet the above-mentioned range.

[0126] To improve the puncture resistance of the base coating, the particle size of the particles in the base coating meets the above-mentioned range, so that smaller voids are formed in the base coating, reducing the risk of metal dendrites puncturing the diaphragm.

[0127] The thickness of the base coating meets the above range, and the diaphragm has good puncture resistance and heat resistance.

[0128] The values ​​in the range of 30% to 70% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 30%, 40%, 50%, 60%, 70%, etc., as well as the range values ​​between any two of the above point values.

[0129] The values ​​in the range of 0.01μm to 2.0μm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.01μm, 0.1μm, 0.5μm, 1μm, 1.5μm, 2.0μm, etc., as well as the range values ​​between any two of the above point values.

[0130] The values ​​in the range of 0.5μm to 3.0μm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.5μm, 1μm, 1.5μm, 2.0μm, 3.0μm, etc., as well as the range values ​​between any two of the above point values.

[0131] In one embodiment, the compression ratio of the diaphragm is T1, which satisfies: 12% ≤ T1 ≤ 22%.

[0132] In this application, the separator is compressible, and its compressibility comes from the base membrane. The compressible separator can reduce the stress when the negative electrode expands and improve the overall cycle performance of the cell.

[0133] The diaphragm's compression ratio meets the above range, which ensures that the diaphragm has good compressibility without being compressed too thin, thus helping to isolate the positive and negative electrodes.

[0134] Test method and procedure for diaphragm compression ratio: Use a micrometer to measure the thickness L10 of the diaphragm before compression. With a pressure sensor, compress the diaphragm at 2.5 MPa and measure the thickness L20 after compression. Calculate the compression ratio using the formula T1 = (L10 - L20) / L10 × 100%.

[0135] In the above 12%≤T1≤22%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 12%, 15%, 18%, 20%, 22%, etc., and the range values ​​between any two of the above point values.

[0136] like Figure 5 As shown, metal 41 is deposited on the surface of the negative electrode 40, and a surface coating 20 is provided on the surface of the base film 10. The surface coating 20 has voids that allow the deposited metal 41 to grow. Furthermore, after a metal deposition layer of a certain thickness is formed on the surface of the negative electrode 40, the base film 10 can be compressed, which can reduce the stress on the battery and improve the battery cycle performance.

[0137] In one embodiment, the initial thickness of the base film is H, which satisfies 6μm≤H≤25μm.

[0138] The initial thickness of the base membrane refers to the thickness of the base membrane in its uncompressed, i.e., natural state. The base membrane meets the above initial thickness so that it can maintain a suitable thickness range after being compressed, thus providing the function of a separator to isolate the positive and negative electrodes.

[0139] In the above 6μm≤H≤25μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 6μm, 8μm, 10μm, 12μm, 15μm, 20μm, 25μm, etc., and the range values ​​between any two of the above point values.

[0140] In one embodiment, the initial thickness of the base film is H, the compression ratio of the separator is T1, and the positive electrode includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The capacity of the positive electrode active material per unit area on one surface of the positive electrode coating is Q, with units of mAh / m³. 2 It satisfies: 0.6Q≤H×T1≤1.9Q.

[0141] It is understandable that the initial thickness H of the base film, the compression ratio T1 of the separator, and the capacity Q of the active material per unit area of ​​the coating on the positive electrode side satisfy the above relationship. That is, the capacity of the positive electrode active material on the positive electrode side is related to the amount of metal deposited on the negative electrode side. The larger the capacity of the positive electrode active material on the positive electrode side, the greater the amount of metal deposited on the negative electrode side will be within a certain range. After the metal on the negative electrode side grows to a certain thickness, it will compress the separator. During the process of generating extrusion force, the base film will be compressed. The metal deposited on the negative electrode can be located in the space formed by the compression, reducing the risk of cell expansion. At the same time, the base film can be compressed, which weakens the piercing force between the metal dendrites and the separator, reducing the risk of metal dendrites piercing the separator.

[0142] In one embodiment, the base membrane material includes at least one selected from polyethylene, polypropylene, nonwoven fabric and polyimide; in another embodiment, the porosity of the base membrane is 30% to 70%.

[0143] The base film material includes at least one of polyethylene, polypropylene, nonwoven fabric and polyimide.

[0144] A porosity within the aforementioned range helps achieve compressibility while ensuring good air permeability, which facilitates ion transport.

[0145] Porosity is the ratio of pore volume to the total volume of the sample. The formula for calculating porosity is P = [V / V0] * 100%. V0 is the volume of the material in its natural state, and V is the volume of all pores in the material. It can be tested using the national standard "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion Porosimetry and Gas Adsorption Methods - Part 1: Mercury Intrusion Porosimetry".

[0146] The values ​​in the range of 30% to 70% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 30%, 40%, 50%, 60%, 70%, etc., as well as the range values ​​between any two of the above point values.

[0147] In one embodiment, the secondary battery is a metal battery.

[0148] Metal batteries are metal deposition type batteries. In metal batteries, active ions are deposited at the negative electrode. For example, taking lithium metal batteries as an example, lithium metal batteries directly use lithium metal as the negative electrode. Lithium ions gain electrons on the surface of the lithium metal electrode and are reduced to elemental lithium and precipitated.

[0149] Metal batteries are at greater risk of swelling. Applying the above-mentioned separator to metal batteries can effectively improve the swelling problem and improve the cycle performance of the battery.

[0150] In one embodiment, the metal battery includes a lithium metal battery, a sodium metal battery, an aluminum metal battery, and a zinc metal battery; and / or, the secondary battery includes a stacked battery, a prismatic battery, a cylindrical battery, and a pouch battery.

[0151] In one embodiment, the metal battery includes lithium metal batteries, sodium metal batteries, aluminum metal batteries, zinc metal batteries, etc. In another embodiment, the secondary battery includes stacked batteries, prismatic batteries, cylindrical batteries, and pouch batteries.

[0152] In one embodiment, this application also provides a diaphragm, the diaphragm including a base membrane, at least one side of the base membrane having a surface coating, the surface of the surface coating having voids.

[0153] In one embodiment, the particle size Dv50 of the particles in the surface coating is 13 μm to 30 μm.

[0154] In one embodiment, the morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes; in one embodiment, the material of the particles in the surface coating includes organic polymers and / or inorganic materials; in one embodiment, the particles in the surface coating are a binder.

[0155] In one embodiment, the mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 In one embodiment, the adhesive material includes at least one selected from polyvinylidene fluoride, styrene-butadiene rubber, polymethyl methacrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

[0156] In one embodiment, the compression ratio of the diaphragm is T1, which satisfies: 12% ≤ T1 ≤ 22%; in another embodiment, the initial thickness of the base film is H, which satisfies 6 μm ≤ H ≤ 25 μm.

[0157] In one embodiment, this application also provides an electrical device, which includes a secondary battery as described above.

[0158] In addition, the battery (cell battery, module battery, pack battery) and electrical device of this application will be described below with appropriate reference to the accompanying drawings.

[0159] In one embodiment of this application, a battery cell is provided.

[0160] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the electrodes while allowing ions to pass through. The separator described above is the improved separator of this application.

[0161] The positive electrode includes a positive current collector and a positive coating disposed on at least one surface of the positive current collector.

[0162] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive coating is disposed on either or both of the two opposite surfaces of the positive current collector.

[0163] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0164] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0165] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0166] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0167] In some embodiments, the positive electrode coating may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0168] In some embodiments, the positive electrode coating may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0169] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0170] The secondary battery in this application can be an ion battery, and the following negative electrode sheet is the structure of the negative electrode sheet of an ion battery.

[0171] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0172] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0173] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0174] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0175] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0176] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0177] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li)).

[0178] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0179] Furthermore, the secondary battery of this application is also applicable to metal batteries. The negative electrode of the metal battery includes a negative current collector (including lithium foil, copper foil, aluminum foil, etc.) and its surface functionalized layer (conductive carbon layer, nanoparticle modification, metal plating, organic coating, 3D framework, etc.). For example, in one embodiment, the negative electrode of the metal battery does not include a negative active material, and active ions can be directly deposited on the negative current collector.

[0180] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0181] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0182] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0183] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0184] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0185] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0186] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 The example shown is a square-structured battery cell 5.

[0187] In some implementations, refer to Figure 7The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0188] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0189] Figure 8 This is battery module 4, used as an example. (See reference...) Figure 8 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0190] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0191] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0192] Figure 9 and Figure 10 This is battery pack 1 as an example. (See reference...) Figure 9 and Figure 10 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0193] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0194] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0195] Figure 11 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0196] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0197] Example

[0198] Example 1

[0199] Preparation of the positive electrode sheet:

[0200] The positive electrode active material (NaFePO4), conductive agent acetylene black, and binder carboxymethyl cellulose are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to form a uniform positive electrode slurry. The positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die cutting, the positive electrode sheet is obtained.

[0201] Preparation of negative electrode sheet:

[0202] The negative electrode sheet provided in this embodiment includes a negative electrode current collector, which comprises a substrate and a coating. The coating is disposed on one side of the substrate, wherein the substrate is a copper foil with a conductive carbon layer coated on its surface. Carbon nanotubes and sodium alginate are added to deionized water and stirred to form a uniform slurry. This slurry is coated onto the copper foil, and after drying, a "negative electrode-free" negative electrode sheet is obtained. The areal density of the coating is 20 g / m³. 2 .

[0203] Preparation of the diaphragm:

[0204] The base film is made of polyethylene and has an initial thickness of 12μm.

[0205] The diaphragm compression ratio is 20%.

[0206] Preparation of the base coating: Ceramic particles (alumina) and binder particles (polyacrylate) are mixed in water at a mass ratio of 4:1 and stirred to obtain a base coating slurry; the base coating slurry is coated on the surface of the base film to obtain a base coating with a thickness of 1μm.

[0207] Preparation of the top coating: The binder particles (polyacrylate polymer, Dv5015μm) and solvent water are mixed at a mass ratio of 2:8 and stirred to obtain the top coating slurry; the top coating slurry is coated on the surface of the base coating and dried to obtain the top coating.

[0208] Electrolyte preparation:

[0209] The electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then uniformly dissolving LiPF6:LiFSI (2:8) in the mixture. The concentration of lithium salt in the electrolyte was 1 mol / L.

[0210] Assembly:

[0211] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell, which is then placed in an aluminum casing and baked at 110°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, formation, shaping, and capacity testing to obtain the lithium-ion battery product.

[0212] Examples 2 to 4

[0213] Based on Example 1, the initial thickness of the base film was adjusted.

[0214] Examples 5 to 7

[0215] Based on Example 1, the compression ratio of the diaphragm was adjusted.

[0216] Examples 8 to 10

[0217] Based on Example 1, the Dv50 of the binder particles in the surface coating was adjusted.

[0218] Example 11

[0219] Based on Example 1, the material of the binder in the surface coating was adjusted, the Dv50 of the binder particles in the surface coating was adjusted, the initial thickness of the base film was adjusted, and the compression ratio of the diaphragm was adjusted.

[0220] Example 12

[0221] Based on Example 1, the material of the binder in the surface coating was adjusted, the Dv50 of the binder particles in the surface coating was adjusted, the initial thickness of the base film was adjusted, and the compression ratio of the diaphragm was adjusted.

[0222] Example 13

[0223] Based on Example 1, no base coating is applied to the surface of the base membrane, and the compression ratio of the diaphragm is adjusted to 2%.

[0224] Comparative Example 1

[0225] Based on Example 1, the diaphragm consists only of the base membrane.

[0226] Comparative Example 2

[0227] Based on Example 1, the diaphragm includes a base membrane and a bottom coating.

[0228] Cyclic expansion force test

[0229] The test environment was room temperature (45℃) and normal pressure. The battery casing was an aluminum square shell.

[0230] Charging process: 0% SOC to 100% SOC uses 0.33C constant current charging; Discharging process: 0% SOC to 100% SOC uses 1C constant current discharging.

[0231] The pressure sensor collects pressure changes, and the formula for calculating the percentage increase in cyclic expansion force is: ((pressure at 200 cycles - pressure at the first cycle) / pressure at the first cycle) × 100%.

[0232] Battery cycle performance test: The battery capacity retention rate test process is as follows: Using the above charging and discharging process, the capacity obtained from the first charge and discharge is recorded as the initial capacity C0. Repeat the above steps for the same battery, and simultaneously record the battery discharge capacity Cn after the nth cycle. Then, the battery capacity retention rate Pn after each cycle is Pn = Cn / C0*100%. Using the 200 points P1, P2...P200 as the vertical axis and the corresponding cycle number as the horizontal axis, the relationship between the battery capacity retention rate and the number of cycles is obtained.

[0233] Table 1. List of data for each embodiment

[0234]

[0235] As shown in Table 1 above, compared to the comparative examples, the cycle expansion force of the battery in the examples decreased, while the cycle performance of the battery was improved. From Examples 1 to 4, it can be seen that, within a certain range, the cycle expansion force decreased with the increase of the initial thickness of the base film. From Examples 5 to 7, it can be seen that, within a certain range, the cycle expansion force decreased with the increase of the base film compression ratio. From Examples 8 to 10, it can be seen that, within a certain range, the cycle expansion force decreased with the increase of the binder particle Dv50 in the top coating. From Examples 7 and 13, it can be seen that Example 13, without a base coating, had a greater cycle expansion force than Example 7, but its 200-cycle capacity retention rate was lower than that of Example 7. When the base coating includes ceramic particles, it can improve the mechanical strength of the separator, improve puncture resistance, and improve the cycle performance of the battery.

[0236] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, and a separator; The diaphragm includes a base membrane, and the base membrane has a surface coating on the side facing the negative electrode sheet. The surface coating has voids on the side facing the negative electrode sheet.

2. The secondary battery as described in claim 1, characterized in that, The particle size Dv50 of the particles in the surface coating is 13 μm to 30 μm.

3. The secondary battery as described in claim 1 or 2, characterized in that, The particle size Dv50 of the particles in the surface coating is d, in μm; The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The capacity of the positive electrode active material per unit area on one surface of the positive electrode coating is Q, with units of Ah / m². 2 ; The condition d and Q satisfy: 0.6Q≤d≤1.9Q.

4. The secondary battery as described in any one of claims 1 to 3, characterized in that, The morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes.

5. The secondary battery as described in any one of claims 1 to 4, characterized in that, The material of the particles in the coating includes organic polymers and / or inorganic materials.

6. The secondary battery as described in any one of claims 1 to 5, characterized in that, The particles in the surface coating are adhesives.

7. The secondary battery as described in claim 6, characterized in that, The mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 ; And / or, the adhesive material includes at least one selected from polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

8. The secondary battery as described in any one of claims 1 to 7, characterized in that, An undercoat layer is also provided between the base film and the topcoat layer.

9. The secondary battery as described in claim 8, characterized in that, The base coating includes ceramic particles; And / or, the base coating includes binder particles.

10. The secondary battery as described in claim 8 or 9, characterized in that, The percentage of ceramic particles in the base coating is 30% to 70% based on the total mass of the base coating. And / or, the particle size Dv50 of the particles in the undercoat is from 0.01 μm to 2.0 μm; And / or, the material of the ceramic particles includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, and zirconium dioxide; And / or, the thickness of the base coating on one side is 0.5 μm to 3.0 μm.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, The compression ratio of the diaphragm is T1, which satisfies the following condition: 12% ≤ T1 ≤ 22%.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The initial thickness of the base film is H, which satisfies 6μm≤H≤25μm.

13. The secondary battery as described in any one of claims 1 to 12, characterized in that, The initial thickness H of the base film, the compression ratio T1 of the separator, and the capacity Q of the positive active material per unit area on one surface of the positive electrode coating in the positive electrode sheet satisfy: 0.6Q≤H×T1≤1.9Q.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The base film is made of at least one of polyethylene, polypropylene, nonwoven fabric and polyimide; And / or, the porosity of the base membrane is 30% to 70%.

15. The secondary battery as described in any one of claims 1 to 14, characterized in that, The secondary battery is a metal battery.

16. The secondary battery as described in claim 15, characterized in that, The metal batteries include lithium metal batteries, sodium metal batteries, aluminum metal batteries, and zinc metal batteries; And / or, the secondary battery includes stacked batteries, square batteries, cylindrical batteries, and pouch batteries.

17. A diaphragm, characterized in that, The diaphragm includes a base membrane, and at least one side of the base membrane is provided with a surface coating, the surface of which has voids.

18. The diaphragm as claimed in claim 17, characterized in that, The particle size Dv50 of the particles in the surface coating is 13 μm to 30 μm.

19. The diaphragm as claimed in claim 17 or 18, characterized in that, The morphology of the particles in the surface coating includes at least one of spherical, near-spherical, island-shaped, and columnar shapes; And / or, the particles in the surface coating are a binder.

20. The diaphragm as claimed in claim 19, characterized in that, The mass of adhesive per unit area in the surface coating is 0.4 g / m². 2 Up to 1.8g / m 2 ; And / or, the adhesive material includes at least one selected from polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose, and polyacrylic acid.

21. The diaphragm according to any one of claims 17 to 20, characterized in that, The compression ratio of the diaphragm is T1, which satisfies: 12% ≤ T1 ≤ 22%; And / or, the initial thickness of the base film is H, satisfying 6μm≤H≤25μm.

22. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1 to 16.

Images