Battery cell and electric device

Abstract

This application provides a battery cell and an electrical device. The battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer. The positive electrode film layer includes a positive active material, which includes a lithium phosphate-containing material. It also includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer. The negative electrode film layer includes a negative active material, which includes at least one of a carbon material or lithium titanate. A separator includes a substrate and an elastic coating, which includes an elastic material. The substrate is located between the elastic coating and the negative electrode sheet. The compressibility of the elastic material is 50%-90%, and the areal density D1 of the elastic material satisfies 0.4 g / m³. 2 ≤D1≤1g / m 2 The thickness D2 of the negative electrode active material satisfies: 80μm≤D2≤150μm. The technical solution of this application can improve the reliability and safety of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell and an electrical device. Background Technology

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, capacity, fast charging performance, and reliability. Therefore, improving battery reliability is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell with high reliability and high safety.

[0005] To achieve the above objectives, this application provides a battery cell and an electrical device.

[0006] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer, the positive electrode film layer being disposed on at least one side of the positive current collector, the positive electrode film layer including a positive active material, the positive active material including a lithium phosphate; a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer, the negative electrode film layer being disposed on at least one side of the negative current collector, the negative electrode film layer including a negative active material, the negative active material including at least one of a carbon material or lithium titanate; and a separator, the separator comprising a substrate and an elastic coating, the elastic coating including an elastic material, the substrate being located between the elastic coating and the negative electrode sheet; wherein the compressibility of the elastic material is 50%-90%, and the areal density D1 of the elastic material satisfies: 0.4 g / m³. 2 ≤D1≤1g / m 2 The thickness D2 of the negative electrode active material satisfies: 80μm≤D2≤150μm.

[0007] In this embodiment, the battery cell includes a positive electrode, a negative electrode, and a separator. The separator includes a substrate and an elastic coating. The elastic coating comprises an elastic material, and the negative electrode comprises a negative active material. The areal density of the elastic material is D1, and the thickness of the negative electrode is D2. The negative active material expands during battery cell cycling, and D1 is maintained at 0.4 g / m³. 2 ≤D1≤1g / m 2To ensure that D2 satisfies: 80μm≤D2≤150μm, and that the compressibility of the elastic material is 50%-90%, the elastic coating provides rebound space for the expanding negative electrode sheet. This reduces the possibility of the negative electrode sheet breaking due to insufficient rebound space, and also reduces the possibility of the central hole collapsing due to excessive expansion of the negative electrode sheet, thus improving the reliability and safety of the battery cell.

[0008] In one possible implementation, D1 and D2 satisfy: D1 / D2 ≥ 3200 g / m 3 .

[0009] In this embodiment, the battery cell includes a separator and a negative electrode sheet. The separator has an elastic coating, and the negative electrode sheet includes a negative electrode active material. The elastic coating comprises an elastic material, and the areal density D1 of the elastic material and the thickness D2 of the negative electrode active material satisfy: D1 / D2 ≥ 3200 g / m². 3 This elastic coating provides sufficient space for the expansion of the negative electrode active material, thereby further reducing the possibility of collapse of the central hole of the battery cell and breakage of the negative electrode sheet, which is beneficial to improving the safety and reliability of the battery cell.

[0010] In one possible implementation, D1 and D2 satisfy: 5000 g / m 3 ≤D1 / D2≤9000g / m 3 .

[0011] In this embodiment, the areal density of the elastic material is D1, and the thickness of the negative electrode active material is D2. Further, the relationship between D1 and D2 is set to 5000 g / m². 3 ≤D1 / D2≤9000g / m 3 While avoiding the collapse of the central hole and the breakage of the electrode, and under the premise of improving the reliability and safety of the battery cell, shortening the transport path of lithium ions between the electrode film layers can reduce the internal resistance of the battery cell and improve its power performance.

[0012] In one possible implementation, D1 satisfies: 0.6 g / m 2 ≤D1≤0.8g / m 2 The D2 satisfies: 90μm≤D2≤120μm.

[0013] In this embodiment of the application, D1 is further made to satisfy: 0.6 g / m 2 ≤D1≤0.8g / m 2The requirement that D2 satisfies 90μm≤D2≤120μm allows sufficient expansion space for the negative electrode during battery cell cycling. This reduces the possibility of the negative electrode breaking and the central hole collapsing during battery cell cycling, while shortening the ion transport path, which is beneficial for balancing the reliability, safety and power performance of the battery cell.

[0014] In one possible implementation, the elastic material comprises a fluoropolymer.

[0015] In this embodiment, the elastic coating needs to be elastic to allow for rebound space for the negative electrode active material. By setting an elastic material, including a fluoropolymer, on the elastic coating, the possibility of negative electrode sheet breakage and central hole collapse can be effectively reduced.

[0016] In one possible implementation, the fluoropolymer comprises polyvinylidene fluoride.

[0017] In this application embodiment, polyvinylidene fluoride is readily available and inexpensive. By including polyvinylidene fluoride in the elastic coating, it is beneficial to reduce the production cost of battery cells and to enable their widespread industrial application.

[0018] In one possible implementation, the volume average particle size Dv50 of the elastic material 1 Satisfies: 2μm≤Dv50 1 ≤10μm.

[0019] In this embodiment, the elastic material on the elastic coating not only provides rebound space for the negative electrode sheet during battery cell cycling, but also adsorbs electrolyte. This is achieved by making the volume average particle size Dv50 of the elastic material... 1 Satisfies: 2μm≤Dv50 1 A thickness of ≤10μm can improve the adsorption capacity of the elastic coating for electrolyte, ensure the smooth transport of ions in the battery cell, and reduce the possibility of lithium plating, thereby improving the cycle performance of the battery cell.

[0020] In one possible implementation, the volume average particle size Dv50 of the elastic material 1 Satisfies: 6μm≤Dv50 1 ≤7μm.

[0021] In this embodiment of the application, the volume average particle size Dv50 of the elastic material is made... 1 Satisfies: 6μm≤Dv50 1 With a thickness of ≤7μm, the transport of lithium ions in the battery cell can be further improved, thereby enhancing the cycle performance of the battery cell.

[0022] In one possible implementation, the elastic coating comprises an inorganic non-metallic material.

[0023] In this embodiment, by adding inorganic non-metallic materials to the elastic coating, the heat shrinkage resistance of the battery cell and the compressive strength of the elastic coating can be increased, and the liquid retention function of the separator can be further improved, thereby improving the overall performance of the battery cell.

[0024] In one possible implementation, based on the total mass of the elastic coating, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 1≤Q1 / Q2≤9.

[0025] In this embodiment, the elastic coating comprises an elastic material and an inorganic non-metallic material. The elastic material provides the negative electrode sheet with rebound space during battery cell cycling, reducing the possibility of breakage due to stretching and improving the reliability of the battery cell. The inorganic non-metallic material improves the compressive strength of the elastic coating and the heat shrinkage resistance of the battery cell. By ensuring that the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy 1 ≤ Q1 / Q2 ≤ 9, a reasonable mass ratio of the two materials in the elastic coating can be achieved, thus balancing various aspects of battery performance.

[0026] In one possible implementation, based on the total mass of the elastic coating, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 13 / 7 ≤ Q1 / Q2 ≤ 4.

[0027] In this embodiment of the application, by ensuring that the mass content of inorganic non-metals Q1 and the mass content of elastic materials Q2 satisfy the condition 13 / 7≤Q1 / Q2≤4, it is beneficial to further consider the various performance aspects of the battery cell.

[0028] In one possible implementation, the volume average particle size Dv50 of the inorganic non-metallic material 2 Satisfies: 60nm≤Dv50 2 ≤1000nm.

[0029] In this embodiment of the application, the volume average particle size Dv50 of the inorganic non-metallic material is made... 2 Satisfies: 60nm≤Dv50 2 With a wavelength of ≤1000nm, more electrolyte can be stored in the elastic coating of the separator, which helps to ensure the smooth transport of ions.

[0030] In one possible implementation, the volume average particle size Dv50 of the inorganic non-metallic material 2 Satisfies: 200nm≤Dv50 2 ≤500nm.

[0031] In this embodiment of the application, the volume average particle size Dv50 of the inorganic non-metallic material is made... 2 Satisfies: 200nm≤Dv50 2 ≤500nm can further improve the smooth transport of ions.

[0032] In one possible implementation, the inorganic non-metallic material includes ceramic materials.

[0033] In this embodiment, the ceramic material has high strength and is readily available. By including the ceramic material in the inorganic non-metallic material, both the compressive strength of the elastic coating and the production cost of the battery cell can be reduced.

[0034] In one possible implementation, the negative electrode film layer further includes a binder; the binder accounts for 1%-3% of the total mass of the negative electrode film layer.

[0035] In this embodiment of the application, by making the mass ratio of the binder in the negative electrode film layer 1%-3%, the expansion of the negative electrode sheet during the charging and discharging process can be suppressed, the expansion rebound rate of the negative electrode sheet can be reduced, and the possibility of the negative electrode sheet breaking can be further reduced.

[0036] In one possible implementation, the binder accounts for 1.5%-2.5% of the total mass of the negative electrode film.

[0037] In this embodiment of the application, by making the mass ratio of the binder in the negative electrode film layer 1.5%-2.5%, both the adhesion performance of the negative electrode film layer and the low expansion performance of the negative electrode sheet can be taken into account.

[0038] In one possible implementation, the lithium-containing phosphate has the general formula Li. a Fe 1-x-y Mn x M y PO4, wherein 0.6≤a≤1.1, 0≤x≤1, 0≤y≤0.1, and M is selected from at least one of transition metal elements other than Fe and Mn and non-transition metal elements.

[0039] In this embodiment of the application, by using lithium phosphate as the positive electrode material, the energy density of the battery cell can be improved.

[0040] In one possible implementation, the lithium-containing phosphate is selected from at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified compounds; the carbon material includes graphite.

[0041] In a second aspect, an electrical device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the structure of the isolation membrane according to one embodiment of this application;

[0044] Figure 2 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0045] Figure 3 This is a schematic diagram of a battery according to an embodiment of this application;

[0046] Figure 4 This is a schematic diagram of an electrical device according to an embodiment of this application;

[0047] Figure 5 This is a schematic diagram of an electrical device according to another embodiment of this application. Detailed Implementation

[0048] Embodiments of the battery cell and power supply device of this application have been described in detail with reference to the accompanying drawings, but 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0049] 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0052] 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.

[0053] Most lithium-ion batteries use carbon materials such as graphite as the negative electrode active material. During the charging and discharging process, lithium ions continuously extract from and embed into the carbon material, causing the negative electrode to expand. This expansion is especially pronounced in today's pursuit of fast charging performance. This expansion can lead to several problems. First, the negative electrode may break due to insufficient space for rebound, resulting in adverse battery consequences. Second, the central hole inside the battery may collapse due to excessive compression from the negative electrode, causing it to overlap with the positive electrode and potentially resulting in a short circuit. In short, the expansion of the negative electrode can significantly impact the reliability and safety of the battery.

[0054] It should be understood that the positive electrode sheet, separator, and negative electrode sheet are wound to form an electrode assembly, which is then processed to form a battery cell. During the winding process, a center pin is usually used as a reference for winding. After the electrode assembly is wound, the center pin is removed, leaving a hole in the electrode assembly, which is the center hole described in the embodiments of this application.

[0055] In view of this, embodiments of this application provide a battery cell and an electrical device. The battery cell includes a positive electrode, a negative electrode, and a separator. The separator includes a substrate and an elastic coating. The negative electrode includes a negative electrode active material. The elastic coating provides elastic space for the expansion of the negative electrode, thereby reducing the possibility of the negative electrode breaking and the possibility of the central hole collapsing, thus improving the safety and reliability of the battery cell.

[0056] The following embodiments will use lithium-ion batteries as an example for detailed explanation. However, it should be noted that the technical solutions of this application are applicable to any battery system, including but not limited to lithium batteries, sodium batteries, magnesium-aluminum batteries, etc.

[0057] During the charging process of a single battery cell, lithium ions are released from the positive electrode active material, move and embed into the negative electrode; while during the discharging process, they move and embed into the positive electrode active material.

[0058] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated into the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” and “deintercalation” processes described in this application refer to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0059] In this application's embodiments, a single battery cell can refer to the smallest structural unit of a battery. Multiple battery cells can first be assembled into a battery module, and then the battery module can be assembled into a battery; multiple battery cells can also be directly assembled into a battery.

[0060] [Battery cell]

[0061] This application provides a single battery cell. The single battery cell includes a positive electrode, a negative electrode, and a separator. The negative electrode includes a negative electrode active material, which includes at least one of carbon materials or lithium titanate; the positive electrode includes a positive electrode active material, which includes lithium phosphate.

[0062] Specifically, the negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes at least one of carbon materials or lithium carbonate. The negative electrode film layer has two opposing surfaces along its own thickness direction. The negative electrode film layer may be disposed on one surface of the negative current collector or on both surfaces of the negative current collector.

[0063] Specifically, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate. The positive electrode film layer has two opposing surfaces along its own thickness direction. The positive electrode film layer can be disposed on one surface of the positive current collector or on both surfaces of the positive current collector.

[0064] Figure 1 This is a schematic diagram of the structure of the isolation membrane according to one embodiment of this application. Figure 1 As shown, the separator 20 includes a substrate 21 and an elastic coating 22. The elastic coating 22 includes an elastic material, and the substrate 21 is located between the elastic coating 22 and the negative electrode sheet.

[0065] The separator is used to separate the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator 20 are manufactured into an electrode assembly through a winding process.

[0066] In other words, the negative electrode sheet, the substrate 21, and the elastic coating 22 are arranged sequentially in the thickness direction.

[0067] The compressibility of the elastic material is 50%-90%, and the areal density D1 of the elastic material satisfies: 0.4 g / m³. 2 ≤D1≤1g / m 2 The thickness D2 of the negative electrode active material satisfies: 80μm≤D2≤150μm.

[0068] The compressibility of an elastic material refers to the amount of deformation it undergoes after being compressed by a pressure of 1 MPa for 1 hour. The greater the compressibility of an elastic material, the greater its inherent elasticity.

[0069] The areal density D1 of the elastic material refers to the mass of the elastic material per unit area of ​​the separator 20, expressed in g / m². 2The greater the areal density D1 of the elastic material, the greater the elasticity of the elastic coating 22. Conversely, the greater the thickness of the negative electrode active material, the greater its expansion during cycling. By limiting the values ​​of D1 and D2 respectively, the elastic coating 22 can provide a reasonable rebound space for the negative electrode active material.

[0070] As mentioned above, during the charge-discharge cycle of a battery cell, the negative electrode sheet expands due to the insertion and extraction of lithium ions. On the one hand, when the negative electrode sheet expands, the central hole inside the battery cell may collapse due to the rebound stress of the negative electrode sheet exceeding the support strength of the central hole; on the other hand, the negative current collector of the negative electrode sheet may break due to insufficient rebound space.

[0071] An elastic coating 22 is provided on the separator 20. When the negative electrode expands, the negative electrode will squeeze the separator 20. Because the elastic coating 22 is elastic, the negative electrode has enough rebound space, which can reduce the possibility of the central hole collapse and the negative electrode breakage.

[0072] In the above scheme, the battery cell includes a positive electrode, a negative electrode, and a separator 20. The separator 20 includes a substrate 21 and an elastic coating 22. The negative electrode, substrate 21, and elastic coating 22 are sequentially arranged in the thickness direction. The elastic coating 22 comprises an elastic material with an areal density of D1. The negative electrode includes a negative active material with a thickness of D2. D1 is set to satisfy 0.4 g / m³. 2 ≤D1≤1g / m 2 The D2 should satisfy: 80μm≤D2≤150μm. The compressibility of the elastic material should be 50%-90%. The elastic coating 22 will provide sufficient rebound space for the expanding negative electrode sheet. In this way, on the one hand, the possibility of the negative electrode sheet breaking due to insufficient rebound space can be reduced, and on the other hand, the possibility of the central hole collapsing due to excessive expansion of the negative electrode sheet squeezing the central hole can be reduced, which is conducive to improving the reliability and safety of the battery cell.

[0073] In addition, the elastic coating 22 is equivalent to setting an insertable gap between the electrode layers, which can increase the internal space of the battery cell and improve the electrolyte injection speed during the manufacturing process.

[0074] In addition, the elastic coating 22 is provided on the side of the separator 20 close to the negative electrode sheet. If the positive electrode active material in the battery cell will also expand significantly, the elastic coating 22 can also be provided on both sides of the separator 20.

[0075] It should be noted that the above mechanism is only used to explain why the internal structure of a battery cell becomes stable, and is not a limitation on the battery cell.

[0076] Specifically, D1 can be 0.4 g / m 2 0.45g / m 2 0.58g / m 2 0.74g / m 2 0.85g / m 2 1g / m 2 Or any value within the above range.

[0077] Specifically, D2 can be 80μm, 100μm, 125μm, 140μm, 150μm or any value within the above range.

[0078] In some implementations, D1 and D2 satisfy: D1 / D2 ≥ 3200 g / m 3 .

[0079] In the above scheme, the battery cell includes a separator 20 and a negative electrode sheet. The separator 20 has an elastic coating 22, and the negative electrode sheet includes a negative electrode active material. The elastic coating 22 is composed of an elastic material, and the areal density D1 of the elastic material and the thickness D2 of the negative electrode active material satisfy: D1 / D2 ≥ 3200 g / m³. 3 This elastic coating provides sufficient space for the expansion of the negative electrode active material, thereby reducing the possibility of collapse of the central hole of the battery cell and breakage of the negative electrode sheet, which is beneficial to improving the safety and reliability of the battery cell.

[0080] Specifically, the ratio of D1 to D2 can be 3200 g / m³. 3 3500g / m 3 3865g / m 3 5000g / m 3 10000g / m 3 Or any value within the above range.

[0081] In some implementations, D1 and D2 satisfy: 5000g / m 3 ≤D1 / D2≤9000g / m 3 .

[0082] The larger the value of D1, the greater the elasticity of the elastic coating 22, the greater the rebound space left for the negative electrode sheet, and the stronger the suppression ability. However, the thickness of the elastic coating 22 will also increase, resulting in a longer lithium-ion transport path, a higher internal resistance of the battery, and poorer power performance.

[0083] D2 represents the thickness of the negative electrode sheet. A larger D2 value indicates a thicker negative electrode sheet, which allows for greater expansion during battery cell cycling and a longer lithium-ion transport path. However, if the D2 value is too small, the negative electrode sheet lacks sufficient toughness, increasing the likelihood of breakage.

[0084] In the above scheme, the areal density of the elastic material is D1, and the thickness of the negative electrode active material is D2. Furthermore, the relationship between D1 and D2 is made to satisfy: 5000 g / m². 3 ≤D1 / D2≤9000g / m 3 This improves the safety and reliability of individual battery cells while shortening the transport path of lithium ions between different film layers, thereby reducing the internal resistance of individual battery cells and improving their power performance.

[0085] In some implementations, D1 satisfies: 0.6 g / m 2 ≤D1≤0.8g / m 2 D2 satisfies: 90μm≤D2≤120μm.

[0086] In the above scheme, further, by making D1 satisfy: 0.6 g / m 2 ≤D1≤0.8g / m 2 The requirement that D2 satisfies 90μm≤D2≤120μm allows sufficient expansion space for the negative electrode during battery cell cycling. This reduces the possibility of the negative electrode breaking and the central hole collapsing during battery cell cycling, while shortening the ion transport path, which is beneficial for balancing the reliability, safety and power performance of the battery cell.

[0087] In some implementations, the elastic material includes a fluoropolymer.

[0088] Fluoropolymers are a class of polymers containing fluorine atoms. These materials are widely used in various industries due to their excellent chemical stability, thermal stability, and corrosion resistance. Among them, polytetrafluoroethylene (PTFE), fluororubber, and polyvinylidene fluoride (PVDF) all exhibit good elasticity.

[0089] In the above scheme, the elastic coating 22 needs to be elastic to allow for rebound space for the negative electrode sheet. By setting an elastic material, including a fluoropolymer, on the elastic coating 22, the possibility of breakage of the negative electrode sheet and collapse of the central hole can be effectively reduced.

[0090] In some embodiments, the fluoropolymer includes polyvinylidene fluoride.

[0091] In the above scheme, polyvinylidene fluoride is readily available and inexpensive. By including polyvinylidene fluoride in the elastic coating 22, it is beneficial to reduce the production cost of battery cells and to enable its widespread industrial application.

[0092] In some embodiments, the volume average particle size Dv50 of the elastic material 1 Satisfies: 2μm≤Dv50 1 ≤10μm.

[0093] An elastic material is coated onto the substrate of the separator 20 to form an elastic coating 22. The particulate elastic material can adsorb the electrolyte, ensuring smooth lithium ion transport during charge-discharge cycles.

[0094] Dv50 can refer to the particle size at which the cumulative particle size distribution number (DV50) of a sample reaches 50%, meaning that particles smaller than DV50 account for 50% of the total particle size distribution. Here, Dv50... 1 This is to be compatible with the Dv50 below. 2 To distinguish them, the volume average particle size is indicated.

[0095] In the above scheme, the elastic material on the elastic coating 22 can not only provide rebound space for the negative electrode sheet during the cycle of the battery cell, but also adsorb electrolyte. This is achieved by making the volume average particle size Dv50 of the elastic material... 1 Satisfies: 2μm≤Dv50 1 A depth of ≤10μm can improve the smooth transport of ions in the battery cell, reduce the possibility of lithium plating, and thus improve the cycle performance of the battery cell.

[0096] In addition, since the elastic material provided on the elastic coating 22 can adsorb and lock the electrolyte, it can prevent the electrolyte from being extracted when the battery cell is in a negative pressure state during the formation stage. This can reduce electrolyte loss and prevent the surface of the battery cell from being contaminated by overflowing electrolyte.

[0097] Specifically, the volume average particle size Dv50 of the elastic material 1 It can be 2μm, 4.5μm, 5.5μm, 7.4μm, 10μm or any value within the above range.

[0098] In some embodiments, the volume average particle size Dv50 of the elastic material 1 Satisfies: 6μm≤Dv50 1 ≤7μm.

[0099] In the above scheme, by making the volume average particle size Dv50 of the elastic material 1 Satisfies: 6μm≤Dv50 1 With a thickness of ≤7μm, the transport of lithium ions in the battery cell can be further improved, thereby enhancing the cycle performance of the battery cell.

[0100] In some embodiments, the elastic coating 22 comprises an inorganic non-metallic material.

[0101] The elastic coating 22 may also include inorganic non-metallic materials, which can increase the elastic coating 22's ability to adsorb electrolyte and improve its electrolyte retention capacity. In addition, inorganic non-metallic materials can also enhance the elastic coating 22's physical properties, such as compressive strength.

[0102] In the above scheme, by adding inorganic non-metallic materials to the elastic coating 22, the heat shrinkage resistance of the battery cell and the compressive strength of the elastic coating 22 can be increased, and the liquid retention function of the separator 20 can be further improved, thereby improving the overall performance of the battery cell.

[0103] In some embodiments, based on the total mass of the elastic coating 22, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 1≤Q1 / Q2≤9.

[0104] The elastic coating 22 includes an elastic material, giving the separator 20 elasticity to provide rebound space for the negative electrode and suppress excessive expansion of the negative electrode. Inorganic non-metallic materials can enhance the physical properties of the elastic coating 22, such as compressive strength. The proportions of both must be kept within a reasonable range; otherwise, the performance of the elastic coating 22 will be affected.

[0105] In the above scheme, the elastic coating 22 includes elastic materials and inorganic non-metallic materials. The elastic material provides the negative electrode sheet with rebound space during battery cell cycling, reducing the possibility of breakage due to stretching and improving the reliability of the battery cell. The inorganic non-metallic material improves the compressive strength of the elastic coating 22 and the heat shrinkage resistance of the battery cell. By ensuring that the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy 1≤Q1 / Q2≤9, a reasonable mass ratio of the two in the elastic coating 22 can be achieved, thus balancing various aspects of battery performance.

[0106] Specifically, the ratio of the mass content Q1 of inorganic non-metallic materials to the mass content Q2 of elastic materials can be 1, 2.5, 4.2, 6, 8.1, 9 or any value within the above range.

[0107] In some embodiments, based on the total mass of the elastic coating 22, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 13 / 7 ≤ Q1 / Q2 ≤ 4.

[0108] In the above scheme, by ensuring that the mass content of inorganic non-metals Q1 and the mass content of elastic materials Q2 satisfy: 13 / 7≤Q1 / Q2≤4, it is beneficial to further take into account the various performance aspects of the battery cell.

[0109] In some embodiments, the volume average particle size Dv50 of the inorganic non-metallic material 2 It satisfies: 60nm≤Dv502≤1000nm.

[0110] In the above scheme, by making the volume average particle size Dv50 of the inorganic non-metallic material 2 By satisfying the condition that 60nm≤Dv502≤1000nm, more electrolyte can be stored in the elastic coating 22 of the separator 20, which in turn helps to ensure the smooth transport of ions.

[0111] Specifically, the volume average particle size Dv50 of inorganic non-metallic materials 2 It can be 60nm, 200nm, 550nm, 740nm, 1000nm or any value within the above range.

[0112] In some embodiments, the volume average particle size Dv50 of the inorganic non-metallic material 2 Satisfies: 200nm≤Dv50 2 ≤500nm.

[0113] In the above scheme, by making the volume average particle size Dv50 of the inorganic non-metallic material 2 Satisfies: 200nm≤Dv50 2 ≤500nm can further improve the smooth transport of ions.

[0114] In some implementations, inorganic nonmetals include ceramic materials.

[0115] In the above scheme, ceramic materials have high strength and are readily available. By including ceramic materials in inorganic non-metallic materials, both the compressive strength of the elastic coating 22 and the production cost of the battery cells can be reduced.

[0116] In some embodiments, the negative electrode film layer includes a binder; the binder accounts for 1%-3% of the total mass of the negative electrode film layer.

[0117] The negative electrode sheet expands during the charge and discharge cycles of a single battery cell. By optimizing the binder content in the negative electrode sheet, the expansion of the negative electrode sheet can be suppressed, thereby reducing the expansion rebound rate at the electrode layer level.

[0118] In the above scheme, by making the mass ratio of the binder in the negative electrode film layer 1%-3%, the expansion of the negative electrode sheet during the charging and discharging process can be suppressed, the expansion rebound rate of the negative electrode sheet can be reduced, and the possibility of the negative electrode sheet breaking can be further reduced.

[0119] Specifically, based on the total mass of the negative electrode film, the mass percentage of the binder can be 1%, 1.4%, 1.8%, 2%, 2.5%, 3%, or any value within the above range.

[0120] In some implementations, the binder accounts for 1.5%-2.5% of the total mass of the negative electrode film.

[0121] In the above scheme, by making the mass ratio of the binder in the negative electrode film layer 1.5%-2.5%, both the adhesion performance of the negative electrode film layer and the low expansion performance of the negative electrode sheet can be taken into account.

[0122] In some embodiments, the general formula for lithium phosphate is Li a Fe 1-x-y Mn x M y PO4, wherein 0.6≤a≤1.1, 0≤x≤1, 0≤y≤0.1, and M is selected from at least one of the transition metal elements other than Fe and Mn, as well as non-transition metal elements.

[0123] It should be noted that during the charging and discharging process of the battery, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li at different discharge states. In the examples of positive electrode active materials in this application, the molar contents of Li refer to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li will change after charge-discharge cycles.

[0124] Similarly, in the examples of positive electrode active materials in the embodiments of this application, the molar content of O is only a theoretical state value. The release of oxygen from the crystal lattice will cause the molar content of oxygen to change. In the actual charging and discharging process of the battery, the molar content of O will fluctuate.

[0125] In some embodiments, the lithium-containing phosphate is selected from at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified compounds.

[0126] The embodiments of this application do not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape.

[0127] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application. For example, such as... Figure 2 As shown, the battery cell 3 is a square lithium-ion battery cell 3. The battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31.

[0128] The electrode assembly 33 can be made from a positive electrode, a negative electrode, and a separator 20 by a winding process or a stacking process.

[0129] End cap assembly 32 includes electrode terminals 322, such as Figure 2 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0130] The battery cell 3 also includes a current collector 34, which is used to connect the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, in the case of a positive electrode in this embodiment, one current collector 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another current collector 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0131] In some embodiments, the battery cell 3 includes an electrode assembly 33, which includes an electrode assembly body 330 and a tab 331 extending from the electrode assembly body 330.

[0132] In some embodiments, the battery cell 3 can be assembled into a battery module, and the number of battery cells 3 contained in the battery module 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 module.

[0133] [Positive electrode plate]

[0134] The positive electrode current collector can be a metal foil or a composite positive electrode current collector. For example, the positive electrode current collector can be an aluminum foil.

[0135] 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.).

[0136] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. 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 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), 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.

[0137] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0138] In some embodiments, the positive electrode film 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.

[0139] 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.

[0140] [Negative electrode plate]

[0141] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0142] 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 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 (copper, copper 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.).

[0143] 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, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material 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.

[0144] 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).

[0145] 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.

[0146] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0147] 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.

[0148] [Electrolytes]

[0149] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0150] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0151] Electrolyte salts may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0152] Solvents may include one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0153] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0154] [Isolation membrane]

[0155] As described above, the separator membrane comprises a substrate and an elastic coating.

[0156] This application does not impose any particular restrictions on the type of separator substrate. Any well-known porous separator with good chemical and mechanical stability can be selected as the separator substrate described in the embodiments of this application.

[0157] The substrate material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions.

[0158] Positive electrode, negative electrode and separator can be made into electrode assembly by winding process or stacking process.

[0159] [Battery]

[0160] This application provides a battery, including the battery cell described in the above embodiments. The lithium-ion battery cell can be a lithium-ion battery cell after formation and aging processes. Figure 3 This is a schematic diagram of a battery according to an embodiment of this application. Figure 3 As shown, battery 5 may include multiple battery cells 3 (not shown in the figure).

[0161] Battery cells 3 can be directly assembled into battery 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 5.

[0162] [Electrical appliances]

[0163] This application provides an electrical device, including the battery described in the above embodiments.

[0164] In some embodiments, the electrical device includes an energy storage device or a heavy-duty truck. Energy storage devices and heavy-duty trucks have high requirements for the lifespan and long-term cycle performance of lithium-ion battery cells. Applying lithium-ion battery cells to the above-mentioned electrical devices can improve the lifespan of the electrical devices.

[0165] Electrical devices can also be lighting devices, spacecraft, etc., and the embodiments of this application include, but are not limited to, these.

[0166] Figure 4 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 4 As shown, this application provides an electrical device, which is a heavy-duty truck 6. The battery in the heavy-duty truck 6 can be replaced by a battery swapping device to replace the battery with insufficient power with a fully charged battery.

[0167] Figure 5 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 5As shown, this application provides an electrical device, which is an energy storage device 7, and the energy storage device 7 may include multiple batteries 5. The energy storage device 7 can be applied to a power storage station to store and release electrical energy.

[0168] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0169] [Examples and Comparative Examples]

[0170] [Example 1]

[0171] (1) Preparation of the release liner: Polyvinylidene fluoride (PVDF) powder, binder, and water were mixed evenly in a mass ratio of 15:15:70 to form an elastic coating slurry. The elastic coating slurry was then applied to the release liner substrate using a coating machine. After drying, a release liner with a PVDF elastic coating was obtained. The release liner substrate was a 12 μm thick polypropylene film, the PVDF compressibility was 90%, and the areal density D1 of the elastic coating was 0.5 g / m³. 2 .

[0172] (2). Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 96:1:1:2 and mixed thoroughly to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet, wherein the thickness D2 of the negative electrode sheet is 80μm.

[0173] (3). Preparation of positive electrode sheet: The positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF) and the conductive agent (carbon black) are mixed evenly in a weight ratio of 96:2:2 and dissolved in the solvent N-methylpyrrolidone (NMP). After being stirred and mixed evenly, a positive electrode slurry is prepared. The positive electrode slurry is evenly coated on the two opposite surfaces of the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0174] (4). Preparation of electrolyte: Ethyl carbonate, diethyl carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L of LiPF6.

[0175] (5) Preparation of battery cells: The cells are arranged in the order of "separator-negative electrode sheet-separator-positive electrode sheet". One end of the positive electrode sheet, negative electrode sheet and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode sheet, negative electrode sheet and two separators. After the positive and negative current collectors of the electrode assembly are flattened, they are put into the cylindrical shell to obtain a wound cylindrical battery.

[0176] [Example 2]

[0177] The difference between Example 2 and Example 1 is that D2 in Example 2 is 120 μm.

[0178] [Example 3]

[0179] The difference between Example 3 and Example 2 is that D1 in Example 3 is 0.6 g / m 2 .

[0180] [Example 4]

[0181] The difference between Example 4 and Example 2 is that D1 in Example 4 is 0.81 g / m 2 .

[0182] [Comparative Example 1]

[0183] The difference between Comparative Example 1 and Example 1 is that the isolation membrane of Comparative Example 1 does not have an elastic coating.

[0184] [Comparative Example 2]

[0185] The difference between Comparative Example 2 and Example 2 is that D1 in Comparative Example 2 is 0.35 g / m 2 .

[0186] [Comparative Example 3]

[0187] The difference between Comparative Example 3 and Example 2 is that D1 in Comparative Example 3 is 0.48 g / m 2 D2 is 164μm.

[0188] Table 1. Specific parameters of Examples 1-4 and Comparative Examples 1-3

[0189]

[0190] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0191] 1. Compressibility of elastic materials: At 25°C, the elastic material is placed between the upper and lower plates of a Mar thickness tester, and a pressure of 1 MPa is applied. After 1 hour of pressing, the ratio of the deformation of the elastic material in thickness to the original thickness of the elastic material is calculated.

[0192] 2. Measurement of the areal density of elastic materials: The areal density of the elastic coating can be obtained by dividing the mass of the elastic material by the area of ​​the substrate.

[0193] 3. Size of the negative electrode active material: can be measured directly.

[0194] 4. Measurement of volume average particle size Dv50: This can be determined by measuring the raw materials used in preparation. As an example, the volume average particle size Dv50 can be measured using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. Alternatively, the volume average particle size can be calculated by observing the material surface using a scanning electron microscope, taking a specific area, and estimating the size and number of particles observed within that area.

[0195] 5. Observation of the center hole of the battery cell: The prepared battery cell is used as the test object.

[0196] After standing at 60℃ for 5 minutes, charge the battery cells at 1C constant current and constant voltage to 3.65V, and let them stand for 1 hour. Then discharge them at 1C constant current to 2V, and let them stand for 2 hours. Repeat this cycle 1000 times, and observe the results using computed tomography (CT) scan.

[0197] 6. Observation of the state of the negative electrode sheet: The prepared battery cell is used as the test object.

[0198] After standing at 60℃ for 5 minutes, the battery cells are charged at 1C constant current and constant voltage to 3.65V and left to stand for 1 hour. Then, they are discharged at 1C constant current to 2V and left to stand for 2 hours. After repeating this cycle 1000 times, the electrode plates are checked for breakage by CT scan and then disassembled to confirm whether the electrode plates are broken.

[0199] 7. Internal resistance test of individual battery cells: The prepared individual battery cells are used as the test objects.

[0200] At 25℃, after standing for 5 minutes, the battery cells are charged at a constant current and constant voltage of 0.33C to a voltage of 3.65V, and then left to stand for 1 hour. Then, they are discharged at a constant current of 0.33C to a voltage of 2V, and left to stand for 2 hours to obtain the capacity C0. The cells are then charged at a constant current and constant voltage of 0.33C to a voltage of 3.65V, and left to stand for 1 hour. Then, they are discharged at a constant current of 1C0 for 0.5 hours, left to stand for 2 hours, and then adjusted to 50% SOC. The cells are then discharged at a current of 10C0 for 10 seconds, and the voltage drop U0 is recorded. The internal resistance R = U0 / 10C0 is calculated.

[0201] Table 2 Test results of Examples 1-4 and Comparative Examples 1-3

[0202]

[0203] As can be seen from Examples 1-4 and Comparative Examples 1-3, by ensuring that the areal density D1 of the elastic coating of the separator in the battery cell satisfies 0.4 g / m², 2 ≤D1≤1g / m 2 Ensuring the thickness D2 of the negative electrode sheet satisfies 80μm≤D2≤150μm can prevent the collapse of the center hole of the battery cell and the breakage of the electrode sheet, thereby improving the safety and reliability of the battery.

[0204] As can be seen from Examples 1-4 and Comparative Examples 2-3, by ensuring that the ratio of D1 to D2 is not less than 3200 g / m³, 3 This can prevent the collapse of the central hole of the battery cell and the breakage of the electrode, thereby improving the safety and reliability of the battery.

[0205] As can be seen from Examples 1-2, under the premise of ensuring that the central hole of the battery cell does not collapse and the electrode does not break, reducing the value of D2 is beneficial to reducing the internal resistance of the battery cell, thereby enabling the battery cell to balance safety, reliability and power performance.

[0206] As can be seen from Examples 2-4, under the premise of ensuring that the central hole of the battery cell does not collapse and the electrode does not break, reducing the value of D1 is beneficial to reducing the internal resistance of the battery cell, thereby enabling the battery cell to balance safety, reliability and power performance.

[0207] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer, the positive electrode film layer being disposed on at least one side of the positive current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising a lithium phosphate; A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer, the negative electrode film layer being disposed on at least one side of the negative current collector, the negative electrode film layer comprising a negative electrode active material, the negative electrode active material comprising at least one of carbon material or lithium titanate; A separator membrane, comprising a substrate and an elastic coating, wherein the elastic coating comprises an elastic material, and the substrate is located between the elastic coating and the negative electrode sheet; in, The compressibility of the elastic material is 50%-90%, and the areal density D1 of the elastic material satisfies: 0.4 g / m³. 2 ≤D1≤1g / m 2 The thickness D2 of the negative electrode active material satisfies: 80μm≤D2≤150μm.

2. The battery cell according to claim 1, characterized in that, The conditions D1 and D2 satisfy: D1 / D2 ≥ 3200g / m 3 .

3. The battery cell according to claim 1 or 2, characterized in that, The conditions D1 and D2 satisfy: 5000g / m 3 ≤D1 / D2≤9000g / m 3 .

4. The battery cell according to any one of claims 1-3, characterized in that, The D1 satisfies: 0.6 g / m 2 ≤D1≤0.8g / m 2 The D2 satisfies: 90μm≤D2≤120μm.

5. The battery cell according to any one of claims 1-4, characterized in that, The elastic material includes fluoropolymers.

6. The battery cell according to any one of claims 1-5, characterized in that, The elastic material includes polyvinylidene fluoride.

7. The battery cell according to any one of claims 1-6, characterized in that, The volume average particle size of the elastic material is Dv50. 1 Satisfies: 2μm≤Dv50 1 ≤10μm.

8. The battery cell according to any one of claims 1-7, characterized in that, The volume average particle size of the elastic material is Dv50. 1 Satisfies: 6μm≤Dv50 1 ≤7μm.

9. The battery cell according to any one of claims 1-8, characterized in that, The elastic coating also includes inorganic non-metallic materials.

10. The battery cell according to claim 9, characterized in that, Based on the total mass of the elastic coating, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 1≤Q1 / Q2≤9.

11. The battery cell according to claim 9 or 10, characterized in that, Based on the total mass of the elastic coating, the mass content Q1 of the inorganic non-metallic material and the mass content Q2 of the elastic material satisfy: 13 / 7≤Q1 / Q2≤4.

12. The battery cell according to any one of claims 9-11, characterized in that, The volume average particle size of the inorganic non-metallic material is Dv50. 2 Satisfies: 60nm≤Dv50 2 ≤1000nm.

13. The battery cell according to any one of claims 9-12, characterized in that, The volume average particle size of the inorganic non-metallic material is Dv50. 2 Satisfies: 200nm≤Dv50 2 ≤500nm.

14. The battery cell according to any one of claims 9-13, characterized in that, The inorganic non-metallic materials include ceramic materials.

15. The battery cell according to any one of claims 1-14, characterized in that, The negative electrode film layer includes a binder; Based on the total mass of the negative electrode film, the binder accounts for 1%-3% of the total mass.

16. The battery cell according to claim 15, characterized in that, Based on the total mass of the negative electrode film, the binder accounts for 1.5%-2.5% of the total mass.

17. The battery cell according to any one of claims 1-16, characterized in that, The general formula of the lithium phosphate is Li a Fe 1-x-y Mn x M y PO4, wherein 0.6≤a≤1.1, 0≤x≤1, 0≤y≤0.1, and M is selected from at least one of transition metal elements other than Fe and Mn and non-transition metal elements.

18. The battery cell according to any one of claims 1-17, characterized in that, The lithium-containing phosphate is selected from at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified compounds; The carbon material includes graphite.

19. An electrical appliance, characterized in that, include: The battery cell according to any one of claims 1-18.

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