Winding battery cell, battery and electric device

Abstract

The embodiment of the invention provides a winding battery cell, a battery and a power utilization device, and relates to the technical field of batteries, the winding battery cell comprises a pole piece and a fixing layer, the pole piece is bent to form a bent part, in the height direction of the winding battery cell, the ratio of the total size of an inactive material area to the size of the pole piece is x, the fixed layer is at least partially pasted on the active material layer located at the bending part, the fixed layer is at least partially pasted on the non-active material area located at the bending part, the fixed layer is provided with a through hole, the fixed layer closest to the head end of the pole piece is a first fixed layer in the winding direction of the winding cell, and the fixed layer closest to the head end of the pole piece is a second fixed layer in the winding direction of the winding cell. A first area is formed between the edge, away from the head end of the pole piece, of the first fixing layer and the head end of the pole piece, the bonding area of the first fixing layer and the pole piece is S1 mm < 2 >, the area of the first area is S2 mm < 2 >, the ratio of S1 to S2 is y, and the hole density of the first fixing layer is z. And (x * y) / z is greater than or equal to 0.0005 and less than or equal to 3.6305, so that lithium precipitation is not easy to occur, and the thermal runaway risk is relatively low in the use process of the battery.

Description

Technical Field

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

[0002] Lithium-ion batteries have advantages such as high energy density, good cycle performance, no memory effect, safety, and environmental friendliness, and are widely used in electric vehicles and portable electronic products. The cell of a lithium-ion battery is formed by winding electrodes and a separator.

[0003] In related technologies, the stress is concentrated in the corner area of ​​the wound cell of lithium-ion battery. At the same time, as the energy density of the battery increases, the electrode sheets are made thicker and thicker. In order to reduce the shedding of the active material layer, a fixing layer is set in the corner area of ​​the wound cell.

[0004] However, lithium-ion batteries pose a significant risk of thermal runaway during use. Summary of the Invention

[0005] This application provides a wound battery cell, a battery, and an electrical device to address the problem of a high risk of thermal runaway during battery use.

[0006] In a first aspect, embodiments of this application provide a wound battery cell, comprising:

[0007] An electrode sheet is bent to form a bent portion. The starting end of the winding of the electrode sheet is the first end of the electrode sheet. The electrode sheet is provided with an active material layer. In the height direction of the wound cell, at least one end of the electrode sheet is formed with an inactive material region. The ratio of the total size of the inactive material region to the size of the electrode sheet is x.

[0008] A fixing layer is at least partially adhered to the active material layer located at the bend, and at least partially adhered to the inactive material area located at the bend, and the fixing layer is provided with through holes;

[0009] In the winding direction of the wound cell, the fixing layer closest to the first end of the electrode is the first fixing layer. A first region is formed between the edge of the first fixing layer away from the first end of the electrode and the first end of the electrode. The bonding area between the first fixing layer and the electrode is S1mm. 2 The area of ​​the first region is S2mm 2 The ratio of S1 to S2 is y;

[0010] The pore density of the first fixing layer is z%.

[0011] The x, y, and z satisfy the condition: 0.0005 ≤ (x × y) / z ≤ 3.6305.

[0012] Secondly, embodiments of this application provide a battery, including a housing and a wound cell as described in the first aspect. The housing has a first surface in the height direction of the wound cell, and a liquid injection hole is provided on the first surface. The housing forms a receiving space, and the wound cell is disposed in the receiving space.

[0013] Thirdly, embodiments of this application provide an electrical device including a battery as described in the second aspect.

[0014] This application provides a wound cell, battery, and power device. By ensuring that (x×y) / z is greater than or equal to 0.0005 and less than or equal to 3.6305, lithium plating is less likely to occur, resulting in a lower risk of thermal runaway during battery use and less likelihood of the fixing layer falling off, thereby improving the overall energy density of the battery. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This application provides a schematic diagram of the structure of a wound battery cell according to an embodiment of the present application;

[0017] Figure 2 for Figure 1 A top view of the wound battery cell;

[0018] Figure 3 This application provides a schematic diagram of the first type of electrode and fixing layer after unfolding, as shown in the embodiments of this application.

[0019] Figure 4 This application provides a schematic diagram of the second type of electrode and fixing layer after unfolding, as part of an embodiment.

[0020] Figure 5 This application provides a schematic diagram of the third type of electrode after unfolding;

[0021] Figure 6 A fourth type of electrode section schematic diagram is provided for embodiments of this application;

[0022] Figure 7 This application provides a schematic diagram of the fifth type of electrode and fixing layer after unfolding;

[0023] Figure 8 This application provides a schematic diagram of the sixth type of electrode and fixing layer after unfolding;

[0024] Figure 9 This application provides a schematic diagram of the seventh type of electrode and fixing layer after unfolding;

[0025] Figure 10 This application provides a cross-sectional schematic diagram of a fixing layer according to an embodiment;

[0026] Figure 11 A cross-sectional schematic diagram of another fixing layer is provided for embodiments of this application;

[0027] Figure 12 This application provides a schematic diagram of the structure of a battery.

[0028] Figure 13 for Figure 12 A schematic diagram of the internal structure of the battery.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Wound cell; 10-Electrode; 1010-Starting end; 100-Bending section; 101-Inactive material area; 102-Active material layer; 103-Insulating layer; 104-Taper; 20-Fixing layer; 201-Through hole; 202-Blank area; 30-Separator;

[0031] 10a-First end; 10b-Second end; 21-Insulating film; 22-Adhesive part; 2-Housing shell; 300-Injection hole; 200-First surface; 210-Second surface; 1000-Straight area; 2000-Bending area. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0036] In the above description, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0037] In the process of preparing a wound battery cell, the active material layer is first coated on the surface of the current collector. After drying, the fixing layer is fixed to the corner of the electrode. Then, the battery is wound into a battery cell and installed in the casing. After installation, the battery needs to be injected with electrolyte. In order to improve the cycle life of the battery, it will undergo multiple electrolyte injections. After the fixing layer comes into contact with the electrolyte, the fixing layer near the opening edge of the wound battery cell will swell and lose its adhesiveness under the immersion of the electrolyte. Therefore, an inactive material area can be set at the end of the electrode to improve the adhesion strength of the fixing layer.

[0038] However, if the size of the inactive material region is too large in the height direction of the wound cell, it will lead to a reduction in the size of the active material layer, a reduction in the lithium-ion transport area, and an easy formation of lithium plating, which will affect the safety of battery use. Therefore, holes can be made in the fixing layer to improve the lithium-ion transport rate, while reducing the size of the inactive material region in the height direction of the wound cell.

[0039] The first end of the electrode is the starting end of the electrode winding. Lithium-ion transport is difficult at the first end of the electrode, and lithium plating is prone to occur. Therefore, it is necessary to control the ratio of the bonding area of ​​the first fixing layer to the area of ​​the region from the first fixing layer to the first end of the electrode to ensure that the fixing layer does not fall off and is not prone to lithium plating, thus ensuring the safety and energy density of the battery.

[0040] The wound battery cell 1, battery and power-consuming device provided in this application embodiment will be described in detail below with reference to specific embodiments.

[0041] Firstly, see [the following] Figure 1 This application provides a wound battery cell 1, including an electrode 10, a separator 30, and a fixing layer 20. The fixing layer 20 is fixed to the electrode 10, and then the electrode 10 and the separator 30 are wound together to form the wound battery cell 1. The winding direction of the electrode 10 is the same as the winding direction of the wound battery cell 1.

[0042] The length direction of the wound cell 1 is the X direction. The thickness direction of the wound cell 1 is the Y direction. The height direction of the wound cell 1 is the Z direction. The X, Y, and Z directions are perpendicular to each other.

[0043] The wound cell 1 is the component in the battery where electrochemical reactions occur; it is the smallest unit in the battery capable of carrying out electrochemical reactions such as charging or discharging.

[0044] The wound cell 1 is the basic unit in a battery. For example, the wound cell 1 is a lithium-ion cell. Lithium-ion cells operate by relying on the insertion and extraction of lithium ions between the positive and negative electrode plates.

[0045] The wound cell 1 includes a flat region 1000 and two bending regions 2000. In the length direction of the wound cell 1, the two bending regions 2000 are located on both sides of the flat region 1000.

[0046] The straight portion of the wound cell 1 is designated as the straight zone 1000. The bent portion of the wound cell 1 is designated as the bent zone 2000.

[0047] See Figure 2 The starting end of the electrode 10 is the first end 1010 of the electrode 10. In the winding direction of the battery cell, the first end 1010 of the electrode 10 is located inside the battery cell 1, that is, in the winding direction of the battery cell, the end of the electrode 10 located inside the battery cell is the first end 1010 of the electrode 10.

[0048] The electrode 10 is wound. The electrode 10 is bent to form a bent portion 100, that is, the electrode 10 forms a bent portion 100 in the bending area 2000 of the wound cell 1. There are multiple bent portions 100.

[0049] See Figure 3 The electrode 10 includes a current collector and an active material layer 102 disposed on the current collector.

[0050] The separator 30 is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode and prevent the positive electrode and the negative electrode from short-circuiting due to contact.

[0051] The diaphragm 30 can be made of at least one of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the surface of the diaphragm 30, which can be an inorganic coating and / or an organic coating. The inorganic coating material includes at least one of alumina, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, and boehmite. The organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0052] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (e.g., lithium ions) are released from the lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (e.g., lithium ions) are released from the negative electrode and intercalate into the lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0053] The current collector of the positive electrode is a positive electrode current collector, and the active material layer 102 of the positive electrode is a positive electrode active material layer. The positive electrode active material layer is coated on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0054] The positive electrode active material includes, but is not limited to, at least one of the following materials: lithium phosphate, lithium transition metal oxide and their respective modified compounds, or other materials that can be used as positive electrode active materials for batteries. These positive electrode active materials can be used alone or in combination of two or more.

[0055] Lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4, also referred to as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxides (e.g., LiCoO2), lithium nickel oxides (e.g., LiNiO2), lithium manganese oxides (e.g., LiMnO2 or LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds.

[0056] The conductive agent of the positive electrode includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black or Super P), carbon nanotubes, graphene and carbon nanofibers.

[0057] The binder for the positive electrode includes, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0058] The positive electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, aluminum alloy, nickel, carbon electrode, or titanium with a silver-plated surface. Composite current collectors can also be used, which may include a polymer material base layer and a metal layer. Composite current collectors are formed by forming metal materials (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0059] During battery charging, active ions (such as Li) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through an external circuit, maintaining charge balance. During discharging, the active ions (such as Li) previously embedded in the negative electrode are released, while electrons from the negative electrode are transferred to the positive electrode through an external circuit, maintaining charge balance and achieving energy storage and release.

[0060] The current collector of the negative electrode is a negative electrode current collector, and the active material layer 102 of the negative electrode is a negative electrode active material layer. The negative electrode active material layer is disposed on at least one surface of the negative electrode current collector.

[0061] The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, aluminum alloy, nickel, carbon electrode, or titanium with a silver-plated surface. Composite current collectors can also be used, which may include a polymer material base layer and a metal layer. Composite current collectors are formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy, etc.) on a polymer material substrate (such as a polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene substrate).

[0062] The negative electrode active material layer includes the negative electrode active material, conductive agent, binder, etc. The negative electrode active material can be a carbon-based material such as graphite, porous carbon, hard carbon, soft carbon, or mesophase carbon microspheres, or a silicon-based material such as elemental silicon, silicon oxide, silicon-carbon composite, or silicon-nitrogen composite.

[0063] The conductive agent in the negative electrode active material layer can be conductive carbon black or carbon nanotubes, and the binder can be styrene-butadiene rubber or polyacrylic acid, etc.

[0064] The electrode 10 can be a positive electrode or a negative electrode. The dimension of the electrode 10 in the height direction of the wound cell 1 is greater than or equal to 70 mm and less than or equal to 160 mm. The dimension of the electrode 10 in the height direction of the wound cell 1 can be 70 mm, 80 mm, 100 mm, 150 mm or 160 mm, etc.

[0065] See Figure 3 In the height direction of the wound cell 1, at least one end of the electrode 10 has an inactive material region 101. Specifically, in the height direction of the wound cell 1, one end of the electrode 10 may have an inactive material region 101. Alternatively, in the height direction of the wound cell 1, both ends of the electrode 10 may have inactive material regions 101.

[0066] The inactive material region 101 is the area at the end of the electrode 10 where no active material is coated.

[0067] In the height direction of the wound cell 1, the ratio of the total size of the inactive material region 101 to the size of the electrode 10 is x.

[0068] It should be noted that when an inactive material region 101 is formed at one end of the electrode 10 along the height direction of the wound cell 1, that is, when there is only one inactive material region 101 on the electrode 10, the size of the inactive material region 101 along the height direction of the wound cell 1 is the total size of the inactive material region 101. When inactive material regions 101 are formed at both ends of the electrode 10 along the height direction of the wound cell 1, that is, when there are two inactive material regions 101 on the electrode 10, the sum of the sizes of the two inactive material regions 101 along the height direction of the wound cell 1 is the total size of the inactive material region 101.

[0069] The number of fixed layers 20 can be one or more.

[0070] The fixing layer 20 can be disposed on at least one surface of the active material layer 102 corresponding to one bend 100 of the wound cell 1, or it can be disposed on at least one surface of the active material layer 102 corresponding to all bends 100 of the wound cell 1.

[0071] The fixing layer 20 is at least partially adhered to the active material layer 102 located in the bend portion 100, and at least partially adhered to the inactive material area 101 located in the bend portion 100. The fixing layer 20 is used to relieve bending stress and suppress electrode shedding. By way of example, the fixing layer 20 can be an adhesive tape.

[0072] It should be noted that the shedding of the active material layer 102 on the electrode 10 indicates material loss.

[0073] The fixing layer 20 includes an insulating film 21 and an adhesive portion 22 (see [link]). Figure 10 The adhesive portion 22 is coated on the insulating film 21, which serves to support the adhesive portion 22.

[0074] The insulating film 21 can be made of at least one of the following: polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, and nonwoven fabric.

[0075] The thickness of the insulating film 21 is greater than or equal to 10 μm and less than or equal to 70 μm. The thickness of the insulating film 21 can be 10 μm, 15 μm, 20 μm, 50 μm, 60 μm or 70 μm, etc.

[0076] The insulating film 21 is bonded to the electrode 10 through the adhesive portion 22, that is, the insulating film 21 is bonded to the active material layer 102 and the inactive material region 101 through the adhesive portion 22.

[0077] The adhesive part 22 may be made of at least one of the following: acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic-grafted polypropylene, polyvinylidene fluoride, maleic anhydride-grafted polypropylene, carboxymethyl cellulose, polyimide, polyetherimide, styrene-isoprene-styrene copolymer rubber, polyethylene phthalate, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, and styrene-isoprene-styrene copolymer.

[0078] The thickness of the adhesive portion 22 is greater than or equal to 10 μm and less than or equal to 50 μm. The thickness of the adhesive portion 22 can be 10 μm, 15 μm, 20 μm, 30 μm, 40 μm or 50 μm, etc.

[0079] In some examples, the ratio of the thickness of the adhesive portion 22 to the thickness of the insulating film 21 is greater than or equal to 0.1 and less than or equal to 0.5.

[0080] If the ratio of the thickness of the adhesive portion 22 to the thickness of the insulating film 21 is greater than 0.5, the thickness of the adhesive portion 22 will be too large, leading to difficulties in lithium-ion transport during battery use, easy lithium plating, and a high risk of short circuits between the electrodes of the wound cell, resulting in a greater risk of thermal runaway. If the ratio of the thickness of the adhesive portion 22 to the thickness of the insulating film 21 is less than 0.1, the thickness of the adhesive portion 22 will be too small, making it easy for the fixing layer 20 to detach, causing the wound cell 1 to shed material and reducing the overall energy density of the battery. By ensuring that the ratio of the thickness of the adhesive portion 22 to the thickness of the insulating film 21 is greater than or equal to 0.1 and less than or equal to 0.5, lithium plating is less likely to occur, the risk of thermal runaway during battery use is lower, the fixing layer 20 is less likely to detach, and the overall energy density of the battery is improved.

[0081] For example, the ratio of the thickness of the adhesive portion 22 to the thickness of the insulating film 21 is 0.3.

[0082] See Figure 3 The fixed layer 20 is provided with through holes 201. During the operation of the battery, lithium ions can pass through the through holes 201, which can improve the lithium ion transmission rate.

[0083] In the winding direction of the wound cell 1, the fixing layer 20 closest to the first end 1010 of the electrode 10 is the first fixing layer, and a first region C is formed between the edge of the first fixing layer away from the first end 1010 of the electrode 10 and the first end 1010 of the electrode 10. Figure 3 The area enclosed by the hollow frame in the diagram is the first region C.

[0084] In the winding direction of the battery cell 1, the distance between the first fixing layer and the first end 1010 of the electrode 10 is greater than or equal to 80 mm and less than or equal to 700 mm. The distance between the first fixing layer and the first end 1010 of the electrode 10 in the winding direction of the battery cell 1 can be 80 mm, 100 mm, 200 mm, 300 mm, 500 mm, or 700 mm, etc.

[0085] If the distance between the first fixing layer and the beginning 1010 of the electrode 10 is greater than 700mm in the winding direction of the wound cell 1, the distance between the first fixing layer and the beginning 1010 of the electrode 10 is too far, resulting in an excessively small size of the first fixing layer in the winding direction of the wound cell 1. This makes the first fixing layer prone to detachment, causing the wound cell 1 to easily lose material and reducing the overall energy density of the battery. If the distance between the first fixing layer and the beginning 1010 of the electrode 10 is less than 80mm in the winding direction of the wound cell 1, the distance between the first fixing layer and the beginning 1010 of the electrode 10 is too close, resulting in an excessively large size of the first fixing layer in the winding direction of the wound cell 1. This makes lithium-ion transport difficult during battery use, easily leading to lithium plating, causing short circuits between the electrodes of the wound cell, and increasing the risk of thermal runaway. By ensuring that the distance between the first fixing layer and the first end 1010 of the electrode 10 is greater than or equal to 80 mm and less than or equal to 700 mm in the winding direction of the wound cell 1, lithium plating is less likely to occur, resulting in a lower risk of thermal runaway during battery use and making it less likely for the fixing layer 20 to fall off, thereby improving the overall energy density of the battery.

[0086] The bonding area between the first fixing layer and the electrode 10 is S1mm. 2 The area of ​​the first region is S2mm 2 The ratio of S1 to S2 is y. It should be noted that mm represents millimeters.

[0087] The pore density of the first fixed layer is z%. Pore density refers to the percentage of pore area per unit area.

[0088] x, y, and z satisfy: 0.0005 ≤ (x × y) / z ≤ 3.6305. (x × y) / z can take values ​​of 0.0005, 0.001, 0.01, 0.1, 1, 2, 3, 3.5, or 3.6305, etc.

[0089] If (x×y) / z is greater than 3.6305, at least one of the following situations will occur: x is too large, y is too large, and z is too small. This will make lithium-ion transport difficult during battery operation, making lithium plating more likely. This will cause short circuits between the electrodes 10 of the wound cell 1, resulting in a greater risk of thermal runaway.

[0090] It should be noted that if (x×y) / z is greater than 3.6305, the proportion of x is too large, which makes the proportion of the non-active material region 101 on the electrode 10 too large in the height direction of the wound cell 1, resulting in the active material layer 102 on the electrode 10 being smaller. The lithium-ion transport area is concentrated, which makes lithium-ion transport difficult during battery operation, making lithium plating easy to occur. This can lead to short circuits between the electrodes 10 of the wound cell 1 and a greater risk of thermal runaway.

[0091] If (x×y) / z is greater than 3.6305, the proportion of y is too large, which makes the bonding area between the fixed layer 20 and the electrode 10 too large in the first region. This will make it difficult for lithium ions to be transported in the first region during battery operation, and lithium plating is likely to occur. This will make it easy for short circuits to occur between the electrodes 10 of the wound cell 1, and the risk of thermal runaway is relatively high.

[0092] If (x×y) / z is greater than 3.6305, the proportion of z is too small, resulting in a small pore density in the fixed layer 20. This makes it difficult for lithium ions to pass through the fixed layer 20 during battery operation, which can easily lead to lithium plating. This can cause short circuits between the electrodes 10 of the wound cell 1, resulting in a greater risk of thermal runaway.

[0093] If (x×y) / z is less than 0.0005, at least one of the following situations will occur: x is too small, y is too small, and z is too large. This will make the fixing layer 20 easy to fall off, causing the wound cell 1 to fall off easily, which will reduce the overall energy density of the battery.

[0094] It should be noted that if (x×y) / z is less than 0.0005, the proportion of x will be too small, resulting in the proportion of the non-active material area 101 on the electrode 10 being too small in the height direction of the wound cell 1. This will cause the bonding size between the fixing layer 20 and the active material layer 102 to be too large. Since there are many pores in the area where the active material layer 102 is located, the electrolyte can easily swell the bonding part 22 of the fixing layer 20 through the pores, resulting in poor bonding strength of the fixing layer 20. This will make the fixing layer 20 easy to fall off, causing the wound cell 1 to easily lose material, which will reduce the overall energy density of the battery.

[0095] If (x×y) / z is less than 0.0005, the proportion of y will be too small, resulting in the bonding area between the fixing layer 20 and the electrode 10 being too small in the area of ​​the first region. This will lead to poor bonding strength of the fixing layer 20, making it easy for the fixing layer 20 to fall off, causing the wound cell 1 to easily lose material, and reducing the overall energy density of the battery.

[0096] If (x×y) / z is less than 0.0005, z will be too large, resulting in an excessively high pore density in the fixing layer 20. This makes it easy for the electrolyte to enter the pores of the fixing layer 20, causing swelling of the adhesive portion 22 of the fixing layer 20. This results in poor adhesive strength of the fixing layer 20, making it easy for the fixing layer 20 to fall off. Consequently, the wound cell 1 is prone to material loss, leading to a reduction in the overall energy density of the battery.

[0097] With (x×y) / z greater than or equal to 0.0005 and less than or equal to 3.6305, lithium plating is less likely to occur, resulting in a lower risk of thermal runaway during battery use. The fixed layer 20 is less likely to fall off, thus improving the overall energy density of the battery.

[0098] In one possible implementation, see Figure 3 In the height direction of the wound cell 1, the total size of the non-active material region 101 is B1mm. B1 satisfies: 1mm≤B1mm≤10mm. The value of B1mm can be 1mm, 1.5mm, 2mm, 3mm, 5mm, 6mm, 9mm or 10mm, etc.

[0099] If B1mm is greater than 10mm, the total size of the inactive material region 101 in the height direction of the wound cell 1 will be too large, resulting in a smaller area of ​​the active material layer 102. This leads to excessive concentration of lithium ions during transport, making lithium plating more likely and forming lithium dendrites. This can cause short circuits between the electrodes 10 of the wound cell 1 during battery use, increasing the risk of thermal runaway. If B1mm is less than 1mm, the bonding area between the fixing layer 20 and the inactive material region 101 will be too small, resulting in low bonding strength. The fixing layer 20 will easily detach, causing the wound cell 1 to shed material and reducing the overall energy density of the battery. By ensuring B1mm is greater than or equal to 1mm and less than or equal to 10mm, lithium plating is less likely to occur during battery use, the risk of thermal runaway is lower, the fixing layer 20 is less likely to detach, and the overall energy density of the battery is improved.

[0100] x satisfies: 0.007 ≤ x ≤ 0.14. The values ​​of x can be 0.007, 0.008, 0.01, 0.015, 0.02, 0.05, 0.1, or 0.14, etc. In some examples, 0.01 ≤ x ≤ 0.1.

[0101] If x is greater than 0.14, the bonding area between the fixed layer 20 and the inactive material region 101 will be too large, resulting in a smaller area of ​​the active material layer 102. This leads to excessive concentration of lithium ions during transport, making lithium plating more likely and forming lithium dendrites. This can cause short circuits between the electrodes 10 of the wound cell 1, increasing the risk of thermal runaway during battery use. If x is less than 0.007, the bonding area between the fixed layer 20 and the inactive material region 101 will be too small, resulting in low bonding strength. This makes the fixed layer 20 prone to detachment, causing material loss from the wound cell 1 and reducing the overall energy density of the battery. By setting x to ≥0.007 and ≤0.14, lithium plating is less likely to occur during battery use, the risk of thermal runaway is lower, the fixed layer 20 is less likely to detach, and the overall energy density of the battery is improved.

[0102] It should be noted that, in this embodiment, the wound cell 1 can satisfy only that B1mm is greater than or equal to 1mm and less than or equal to 10mm, or only that x is greater than or equal to 0.007 and less than or equal to 0.14, or simultaneously satisfy that B1mm is greater than or equal to 1mm and less than or equal to 10mm, and x is greater than or equal to 0.007 and less than or equal to 0.14.

[0103] In one possible implementation, see Figure 3 In the height direction of the wound cell 1, an inactive material region 101 is disposed at one end of the electrode 10; that is, an inactive material region 101 is formed at one end of the electrode 10 in the height direction of the wound cell 1. In this example, x satisfies: 0.01 ≤ x ≤ 0.14. The value of x can be 0.01, 0.015, 0.02, 0.05, 0.1, or 0.14, etc.

[0104] If x is greater than 0.14, the bonding area between the fixed layer 20 and the inactive material region 101 at one end of the electrode 10 will be too large, resulting in a smaller area of ​​the active material layer 102. This leads to excessive concentration of lithium ions during transport, making lithium plating more likely and forming lithium dendrites. This can cause short circuits between the electrodes 10 of the wound cell 1, increasing the risk of thermal runaway during battery use. If x is less than 0.01, the bonding area between the fixed layer 20 and the inactive material region 101 at one end of the electrode 10 will be too small, resulting in low bonding strength between the fixed layer 20 and the inactive material region 101. This makes the fixed layer 20 prone to detachment, causing material loss from the wound cell 1 and reducing the overall energy density of the battery. By setting x to ≥0.01 and ≤0.14, lithium plating is less likely to occur during battery use, the risk of thermal runaway is lower, the fixed layer 20 is less likely to detach, and the overall energy density of the battery is increased.

[0105] In this embodiment, the size of the inactive material region 101 in the height direction of the wound cell 1 is B1mm.

[0106] In the height direction of the wound cell 1, the electrode 10 has a first end 10a close to the inactive material region 101 and a second end 10b away from the inactive material region 101, and the end of the fixing layer 20 away from the inactive material region 101 extends beyond the second end 10b. This arrangement ensures that the fixing layer 20 and the active material layer 102 are fully bonded in the height direction of the wound cell 1, thereby improving the bonding strength between the fixing layer 20 and the active material layer 102.

[0107] See in some examples Figure 3 In the height direction of the wound cell 1, the distance by which the end of the fixing layer 20 away from the inactive material region 101 extends beyond the second end 10b is A1mm, where A1 satisfies: 0.1mm≤A1mm≤10mm. The value of A1mm can be 0.1mm, 0.2mm, 1mm, 2mm, 5mm, or 10mm, etc.

[0108] If A1mm is less than 10mm, the distance from the end of the fixing layer 20 away from the inactive material region 101 to the second end 10b is too small in the height direction of the wound cell 1, making it difficult to bond the fixing layer 20 to the active material layer 102. If A1mm is greater than 0.1mm, the distance from the end of the fixing layer 20 away from the inactive material region 101 to the second end 10b is too large in the height direction of the wound cell 1, resulting in excessive material usage for the fixing layer 20 and increasing the battery production cost. A1mm being greater than or equal to 0.1mm and less than or equal to 10mm facilitates the bonding of the fixing layer 20 and reduces the battery production cost.

[0109] See in some examples Figure 4 In the thickness direction of the electrode 10, the fixing layer 20 disposed opposite to the first fixing layer on a single bent portion 100 is the second fixing layer, and the first fixing layer and the second fixing layer are respectively disposed on both sides of the electrode 10.

[0110] In the height direction of the wound cell, the ends of the first and second fixing layers that are away from the inactive material region 101 extend beyond the second end 10b, and the portions of the first and second fixing layers extending beyond the second end 10b are bonded together. This arrangement, through the bonding of the first and second fixing layers, makes it less likely for them to detach. Figure 4 One of the fixed layers 20 is the first fixed layer, and the other fixed layer 20 is the second fixed layer. The dashed box represents the second fixed layer.

[0111] For example, in the height direction of the wound cell, the bonding dimension of the first fixing layer and the second fixing layer at the end away from the inactive material region 101 is A2mm. A2 satisfies: 0.1mm≤A2mm≤10mm. The value of A2mm can be 0.1mm, 0.2mm, 1mm, 2mm, 5mm or 10mm, etc.

[0112] If A2mm is less than 0.1mm, and A1mm is greater than or equal to 0.1mm and less than or equal to 10mm, the bonding size of the first and second fixing layers is too small in the height direction of the wound cell 1, making it inconvenient to bond the first and second fixing layers. If A2mm is greater than 10mm, and A1mm is greater than or equal to 0.1mm and less than or equal to 10mm, the bonding size of the first and second fixing layers is too large in the height direction of the wound cell 1, making it easy for the first and second fixing layers to accidentally contact components such as terminals, causing thermal shrinkage and detachment. By ensuring that A2mm is greater than or equal to 0.1mm and less than or equal to 10mm, and A1mm is greater than or equal to 0.1mm and less than or equal to 10mm, the bonding of the first and second fixing layers can be facilitated, and the first and second fixing layers are less likely to detach.

[0113] In one possible implementation, see Figure 5 In the height direction of the wound cell 1, an inactive material region 101 is provided at each of the opposite ends of the electrode 10. The size of the inactive material region 101 is A3mm, where A3 satisfies: 1mm≤A3mm≤8mm. The value of A3mm can be 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, or 8mm, etc.

[0114] If A3mm is greater than 8mm, the size of the inactive material region 101 will be too large in the height direction of the wound cell 1, resulting in a smaller area of ​​the active material layer 102. This causes lithium ion transport to become too concentrated, making lithium plating more likely and forming lithium dendrites. This can lead to short circuits between the electrodes 10 of the wound cell 1 during battery use, increasing the risk of thermal runaway. If A3mm is less than 1mm, the bonding area between the fixing layer 20 and the inactive material region 101 will be too small, resulting in low bonding strength. The fixing layer 20 will easily detach, causing the wound cell 1 to shed material and reducing the overall energy density of the battery. By ensuring A3mm is greater than or equal to 1mm and less than or equal to 8mm, lithium plating is less likely to occur, reducing the risk of thermal runaway during battery use, preventing the fixing layer 20 from detaching, and improving the overall energy density of the battery.

[0115] In this embodiment, the sum of the dimensions of the two inactive material regions 101 in the height direction of the wound cell 1 is B1mm.

[0116] In one possible implementation, see Figure 6 An insulating layer 103 is provided on the inactive material region 101, and the fixing layer 20 is adhered to the insulating layer 103. This arrangement can improve the adhesion strength between the fixing layer 20 and the inactive material region 101 and prevent the fixing layer 20 from falling off.

[0117] The insulating layer 103 is coated on at least one side of the current collector of an electrode 10 near the tab, or on at least one side of the tab surface. This can prevent the tab from short-circuiting with another electrode 10 of opposite polarity, and also prevent the tab from breaking when bent during battery assembly.

[0118] The insulating layer 103 is made of insulating materials such as polyvinylidene fluoride (PVDF), boehmite, polypropylene, or polyethylene.

[0119] The thickness of the insulating layer 103 is greater than or equal to 20 μm and less than or equal to 110 μm. The thickness of the insulating layer 103 can be 20 μm, 30 μm, 50 μm, 100 μm or 110 μm, etc.

[0120] The thickness of the active material layer 102 of the electrode 10 is greater than or equal to 30 μm and less than or equal to 210 μm. The thickness of the active material layer 102 of the electrode 10 can be 30 μm, 50 μm, 70 μm, 100 μm, 200 μm or 210 μm, etc.

[0121] The thickness of the active material layer 102 of the electrode 10 is greater than or equal to the thickness of the insulating layer 103. This arrangement avoids gaps between the electrodes 10 due to the protrusion of the insulating layer 103, which would affect lithium-ion transport and lead to lithium plating.

[0122] In some examples, the difference between the thickness of the active material layer 102 and the thickness of the insulating layer 103 is greater than or equal to 10 μm and less than or equal to 190 μm. If the difference between the thickness of the active material layer 102 and the thickness of the insulating layer 103 is greater than 190 μm, the thickness of the insulating layer 103 will be too small, resulting in poor adhesion between the fixing layer 20 and the insulating layer 103, making the fixing layer 20 prone to detachment, causing the wound cell 1 to easily shed material, thus reducing the overall energy density of the battery. If the difference between the thickness of the active material layer 102 and the thickness of the insulating layer 103 is less than 10 μm, the thickness of the insulating layer 103 will be too large, resulting in excessive material usage for the insulating layer 103, increasing the battery production cost. By ensuring that the difference between the thickness of the active material layer 102 and the thickness of the insulating layer 103 is greater than or equal to 10 μm and less than or equal to 190 μm, the fixing layer 20 is less likely to detach, the wound cell 1 is less likely to shed material, the overall energy density of the battery is improved, and the battery production cost is reduced.

[0123] See in some examples Figure 6 The active material layer 102 and the insulating layer 103 have an overlapping area. Specifically, in the thickness direction of the electrode 10, the area where the active material layer 102 is covered by the insulating layer 103 is the overlapping area.

[0124] In the height direction of the wound cell 1, the size of the overlapping area is A4mm, and A4 satisfies: 0.1mm≤A4mm≤3mm. The value of A4 can be 0.1mm, 0.5mm, 1mm, 1.1mm, 1.5mm, 2mm or 3mm, etc.

[0125] If A4mm is greater than 3mm, it will affect electrolyte wetting, hinder lithium-ion transport, and lead to easy lithium plating. If A4mm is less than 0.1mm, the overlapping area in the height direction of the wound cell 1 will be too small, and the edge of the active material layer 102 in the height direction of the wound cell 1 will easily shed material. When A4mm is greater than or equal to 0.1mm and less than or equal to 3mm, lithium plating is less likely to occur during battery operation, and the edge of the active material layer 102 in the height direction of the wound cell 1 is less likely to shed material.

[0126] In one possible implementation, see Figure 7 In the height direction of the wound cell 1, the electrode 10 has a first end 10a and a second end 10b that are disposed opposite to each other.

[0127] Among them, the first end 10a leads out the tab 104, and the inactive material region 101 is disposed at the first end 10a.

[0128] The tab 104 is disposed on one side of the current collector of the electrode 10. The tab 104 can be welded to the current collector or integrally formed with the current collector, thereby making the tab 104 electrically connected to the current collector to conduct the current on the corresponding current collector.

[0129] The tab 104 is made of a metallic material (such as copper, aluminum or nickel).

[0130] See Figure 7 In the height direction of the wound cell 1, the size of the overlapping portion of the fixing layer 20 and the inactive material region 101 is A5mm, where A5 satisfies: 0.1mm≤A5mm≤8mm. The value of A5mm can be 0.1mm, 0.5mm, 1mm, 2mm, 5mm, 6mm or 8mm, etc.

[0131] If A5mm is greater than 8mm, the overlapping portion of the fixing layer 20 and the inactive material region 101 in the height direction of the wound cell 1 will be too large, causing the fixing layer 20 to easily shrink and detach when the tab 104 generates heat. If A5mm is less than 0.1mm, the overlapping portion of the fixing layer 20 and the inactive material region 101 in the height direction of the wound cell 1 will be too small, resulting in an insufficient bonding area between the fixing layer 20 and the inactive material region 101, making the fixing layer 20 prone to detachment. When A5mm is greater than or equal to 0.1mm and less than or equal to 8mm, the fixing layer 20 is less likely to detach.

[0132] In one possible implementation, see Figure 7 In the height direction of the wound cell 1, the end of the fixing layer 20 does not extend beyond the outer end of the inactive material region 101. This arrangement facilitates the wetting of the electrolyte at the bend 100, improves the lithium-ion transport capacity, and reduces the risk of lithium plating.

[0133] The outer end of the inactive material region 101 is the end of the inactive material region 101 that is far away from the active material layer 102 in the height direction of the winding cell 1.

[0134] See in some examples Figure 7 In the height direction of the wound cell 1, the distance between the end of the fixing layer 20 and the outer end of the inactive material region 101 is A6mm, where A6 satisfies: 0.1mm≤A6mm≤2.6mm. The value of A6mm can be 0.1mm, 0.5mm, 1mm, 1mm, 1.5mm, 2mm, 2.5mm or 2.6mm, etc.

[0135] It should be noted that when an inactive material region 101 is formed at one end of the electrode 10 in the height direction of the wound cell 1, one end of the fixing layer 20 does not extend beyond the outer end of the inactive material region 101, and the distance between the end of the fixing layer 20 and the outer end of the inactive material region 101 is A6mm. When inactive material regions 101 are formed at both ends of the electrode 10 in the height direction of the wound cell 1, neither end of the fixing layer 20 extends beyond the outer ends of the two inactive material regions 101. The sum of the distances between the two ends of the fixing layer 20 and the outer ends of the two inactive material regions 101 is A6mm.

[0136] If A6mm is greater than 2.6mm, the distance between the end of the fixing layer 20 and the outer end of the inactive material region 101 will be too large in the height direction of the wound cell 1. This results in an insufficient bonding area between the fixing layer 20 and the inactive material region 101, making the fixing layer 20 prone to detachment. Consequently, the wound cell 1 is prone to material loss, reducing the overall energy density of the battery. If A6mm is less than 0.1mm, the distance between the end of the fixing layer 20 and the outer end of the inactive material region 101 will be too small in the height direction of the wound cell 1. This affects electrolyte wetting, hinders lithium-ion transport, and makes lithium plating more likely. By ensuring that A6mm is greater than or equal to 0.1mm and less than or equal to 2.6mm, lithium plating is less likely to occur during battery operation, the fixing layer 20 is less likely to detach, and the wound cell 1 is less likely to lose material, thus improving the overall energy density of the battery.

[0137] In one possible implementation, in the height direction of the wound cell 1, the end of the fixing layer 20 extends beyond the outer end of the inactive material region 101 by an amount of A7 mm (see [reference]). Figure 3 A7 satisfies: 0.1mm ≤ A7mm ≤ 13mm. The value of A7mm can be 0.1mm, 0.2mm, 1mm, 2mm, 5mm, 10mm or 13mm, etc.

[0138] It should be noted that when an inactive material region 101 is formed at one end of the electrode 10 in the height direction of the wound cell 1, one end of the fixing layer 20 extends beyond the outer end of the inactive material region 101, and the distance between the end of the fixing layer 20 and the outer end of the inactive material region 101 is A7mm. When inactive material regions 101 are formed at both ends of the electrode 10 in the height direction of the wound cell 1, both ends of the fixing layer 20 extend beyond the outer ends of the two inactive material regions 101. The sum of the distances between the two ends of the fixing layer 20 and the outer ends of the two inactive material regions 101 is A7mm.

[0139] If A7mm is greater than 13mm, the extension of the end of the fixing layer 20 beyond the outer end of the inactive material region 101 in the height direction of the wound cell 1 is too large, making it easy for the fixing layer 20 to accidentally contact components such as the electrode post, causing thermal shrinkage and detachment. If A7mm is less than 0.1mm, the extension of the end of the fixing layer 20 beyond the outer end of the inactive material region 101 in the height direction of the wound cell 1 is too small, making it inconvenient to bond the fixing layer 20 to the inactive material region 101. By ensuring that A7mm is greater than or equal to 0.1mm and less than or equal to 13mm, the fixing layer 20 is less likely to detach, and it is also convenient to bond the fixing layer 20 to the inactive material region 101.

[0140] In some examples, in the thickness direction of the electrode 10, the fixing layer 20 disposed opposite to the first fixing layer on a single bent portion 100 is a second fixing layer, and the first fixing layer and the second fixing layer are respectively disposed on both sides of the electrode 10.

[0141] In the height direction of the wound cell, the ends of the first fixing layer and the second fixing layer that are away from the inactive material region 101 extend beyond the second end 10b, and the portions of the first fixing layer and the second fixing layer that extend beyond the second end are bonded together.

[0142] In the height direction of the wound cell, the bonding dimension of the end of the first fixing layer and the second fixing layer away from the inactive material region 101 is A2mm, where A2 satisfies: 0.1mm≤A2mm≤8mm. The value of A2mm can be 0.1mm, 0.2mm, 1mm, 2mm, 5mm or 8mm, etc.

[0143] If A2mm is less than 0.1mm, and A7mm is greater than or equal to 0.1mm and less than or equal to 13mm, the bonding size of the first and second fixing layers is too small in the height direction of the wound cell 1, making it inconvenient to bond the first and second fixing layers. If A2mm is greater than 8mm, and A7mm is greater than or equal to 0.1mm and less than or equal to 13mm, the bonding size of the first and second fixing layers is too large in the height direction of the wound cell 1, making it easy for the first and second fixing layers to accidentally contact components such as the electrode posts, causing thermal shrinkage and detachment. By ensuring that A2mm is greater than or equal to 0.1mm and less than or equal to 8mm, and A7mm is greater than or equal to 0.1mm and less than or equal to 13mm, the bonding of the first and second fixing layers can be facilitated, and the first and second fixing layers are less likely to detach.

[0144] In some examples, the wound cell 1 also includes a separator 30 that is stacked and wound with the electrode 10, wherein the fixing layer 20 extends beyond the separator 30 by an dimension of A8 mm in the height direction of the wound cell 1 (see [reference]). Figure 3 A8 satisfies: A8mm≤9.4mm. The value of A8mm can be 1mm, 2mm, 5mm, 9mm or 9.4mm, etc.

[0145] If A8mm is greater than 9.4mm, the fixing layer 20 will extend too far beyond the separator 30 in the height direction of the wound cell 1. This will cause the fixing layer 20 to easily stick to other separators 30, affecting electrolyte wetting, resulting in a lower lithium-ion transport rate, and also making other separators 30 more prone to folding, leading to insulation failure. By keeping A8mm less than or equal to 9.4mm, the lithium-ion transport rate can be improved, and the folding of the separator 30 can be prevented, ensuring insulation.

[0146] See in some examples Figure 7 The wound cell 1 also includes a separator 30 that is stacked and wound around the electrode 10. In the height direction of the wound cell 1, the outer end of the fixing layer 20 does not extend beyond the end of the separator 30. With this arrangement, the fixing layer 20 is less likely to stick to other separators 30, and the separators 30 are less likely to fold, thus ensuring insulation.

[0147] In some examples, the thickness of electrode 10 is greater than or equal to 70 μm. If the thickness of electrode 10 is less than 70 μm, the fixing layer 20 is prone to sticking to other separators 30, affecting electrolyte wetting, resulting in a lower lithium-ion transport rate, and also easily causing other separators 30 to fold, leading to insulation failure. By ensuring the thickness of electrode 10 is greater than or equal to 70 μm, the lithium-ion transport rate can be improved. Furthermore, it also prevents separators 30 from folding, ensuring insulation.

[0148] The thickness of electrode 10 is less than or equal to 300 μm. If the thickness of electrode 10 is greater than 300 μm, it will be too thick, causing material to fall off during the winding process, thus reducing the overall energy density of the battery. By keeping the thickness of electrode 10 less than or equal to 300 μm, the overall energy density of the battery can be improved.

[0149] In one possible implementation, S2 satisfies: 6300mm 2 ≤S2mm 2 ≤116800mm 2 S2mm 2 The value can be 6300mm 2 7000mm 2 8000mm 2 10000mm 2 50000mm 2 100,000 mm 2 Or 116800mm 2 wait.

[0150] If S2mm 2 Greater than 116800mm 2 This can lead to an excessively large area ratio in the first region, resulting in an insufficient bonding area for the first fixing layer. Consequently, the fixing layer 20 is prone to detachment, and the wound cell 1 is prone to material loss, thus affecting the overall energy density of the battery. If S2mm 2 Less than 6300mm 2 This can lead to a situation where the area ratio of the first region is too small, resulting in an excessively large bonding area for the first fixing layer. The first fixing layer then hinders lithium-ion transport, making lithium plating more likely. This can be addressed using S2mm. 2 ≥6300mm 2 And less than or equal to 116800mm 2This makes it easier for the fixing layer 20 to fall off during battery operation, and for the wound cell 1 to not fall off, thereby improving the overall energy density of the battery and making it less prone to lithium plating.

[0151] The property y satisfies: 0.014 ≤ y ≤ 0.27. The values ​​of y can be 0.014, 0.02, 0.05, 0.1, 0.2, or 0.27, etc. In some examples, 0.02 ≤ y ≤ 0.25.

[0152] If y is greater than 0.27, the ratio of the adhesive area of ​​the first fixing layer to the area of ​​the first region will be too small, causing the fixing layer 20 to easily detach and the wound cell 1 to easily shed material, thus affecting the overall energy density of the battery. If y is less than 0.014, the ratio of the adhesive area of ​​the first fixing layer to the area of ​​the first region will be too large, and the first fixing layer will hinder lithium-ion transport, leading to easy lithium plating. By setting y to be greater than or equal to 0.11 and less than or equal to 0.27, the fixing layer 20 is less likely to detach during battery operation, the wound cell 1 is less likely to shed material, the overall energy density of the battery is improved, and lithium plating is less likely to occur.

[0153] It should be noted that, in this embodiment, the wound cell 1 can only meet the requirement of S2mm. 2 ≥6300mm 2 And less than or equal to 116800mm 2 Alternatively, it can simply satisfy y > 0.11 and < 0.27, or simultaneously satisfy S2mm. 2 ≥6300mm 2 And less than or equal to 116800mm 2 y is greater than or equal to 0.11 and less than or equal to 0.27.

[0154] In one possible implementation, in the winding direction of the wound cell 1, a tab 104 is provided between the first end 1010 of the electrode 10 and the first fixing layer, and the distance between the tab 104 and the first fixing layer is A9mm (see [reference]). Figure 3 A9 satisfies: 15mm ≤ A9mm ≤ 250mm. The value of A9mm can be 15mm, 50mm, 100mm, 150mm, 200mm, 220mm or 250mm, etc.

[0155] If A9mm is greater than 250mm, the distance between the tab 104 and the first fixing layer will be too large in the winding direction of the battery cell 1. This will increase the electron migration resistance at the point where the electrode 10 is covered by the first fixing layer, causing the battery temperature to rise too high and reducing battery safety. If A9mm is less than 15mm, the distance between the tab 104 and the first fixing layer will be too small in the winding direction of the battery cell 1. When the tab 104 generates heat, the fixing layer 20 is prone to shrinkage and detachment due to heat. By ensuring that A9 is greater than or equal to 15mm and less than or equal to 250mm, the excessive battery temperature rise can be reduced, battery safety can be improved, and the first fixing layer is less likely to detach.

[0156] In one possible implementation, see Figure 8 The electrode 10 is provided with tabs 104. In the winding direction of the wound cell 1, the tab 104 closest to the beginning end 1010 of the electrode 10 is the first tab. A first fixing layer is provided between the beginning end 1010 of the electrode 10 and the first tab. The distance from the first tab to the first fixing layer is A10mm, and A10 satisfies: 25mm≤A10mm≤250mm. The value of A10mm can be 25mm, 50mm, 100mm, 150mm, 200mm, 220mm, or 250mm, etc.

[0157] If A10mm is greater than 250mm, the distance between the first tab and the first fixing layer will be too large in the winding direction of the battery cell 1. This will increase the internal resistance of electron migration at the point where the electrode 10 is covered by the first fixing layer, resulting in excessive battery temperature rise and reduced battery safety. If A10mm is less than 25mm, the distance between the first tab and the first fixing layer will be too small in the winding direction of the battery cell 1. When the first tab generates heat, the fixing layer 20 is prone to shrinkage and detachment due to heat. By ensuring that A10mm is greater than or equal to 25mm and less than or equal to 250mm, excessive battery temperature rise can be reduced, battery safety can be improved, and the first fixing layer is less likely to detach.

[0158] In one possible implementation, see Figure 2 Along the length of the wound cell 1, the electrode 10 has two opposing bends 100, each with a fixing layer 20. This arrangement can alleviate the bending stress at the opposing bends 100 of the electrode 10 and suppress electrode shedding.

[0159] Among them, the two opposite bends 100 of the electrode 10 are located on both sides of the length direction of the electrode 10 winding the cell 1.

[0160] In one possible implementation, a fixing layer 20 is provided within the first five turns of the electrode 10 closest to the first end 1010 of the wound cell 1. This arrangement addresses the issue of stress concentration and a large radius of curvature in the inner turns of the electrode 10 near its first end 1010, which poses a significant risk of material loss. Therefore, the fixing layer 20 within the first five turns closest to the first end 1010 of the electrode 10 protects the active material layer 102 of the electrode 10 and reduces the risk of material loss.

[0161] One turn of the electrode 10 has an initial end and a tail end along the winding direction of the winding cell 1. The initial end and the tail end are located in the flat region 1000. One turn of the electrode 10 passes through two bending regions 2000 of the winding cell 1. The initial end and the tail end overlap in the thickness direction of the winding cell 1.

[0162] For example, the first end 1010 of the electrode 10 can be used as the initial end of the first turn of the electrode 10 in the winding cell 1 that is closest to the first end 1010 of the electrode 10. The first turn 1010 of the electrode 10 is wound 5 times as the 5 turns of the electrode 10 in the winding cell 1 that are closest to the first end 1010 of the electrode 10.

[0163] In one possible implementation, the dimension of the fixing layer 20 is A11mm in the winding direction of the wound cell 1 (see...). Figure 3 A11 satisfies: 10mm≤A11mm≤30mm. The value of A11mm can be 10mm, 11mm, 15mm, 20mm, 25mm or 30mm, etc.

[0164] If A11mm is greater than 30mm, it results in excessive material usage for the fixing layer 20, increasing the battery production cost. If A11mm is less than 10mm, the bonding area of ​​the fixing layer 20 will be too small, making it prone to detachment. A11mm being greater than or equal to 10mm and less than or equal to 30mm reduces battery production costs and also makes the fixing layer 20 less likely to detach.

[0165] In one possible implementation, z satisfies: 1% ≤ z% ≤ 30%. The value of z% can be 1%, 5%, 10%, 15%, 20%, 29%, or 30%, etc. In some examples, 2% ≤ z% ≤ 27%.

[0166] The pore density of the first fixing layer can be adjusted by adjusting the diameter of a single through-hole 201 on the first fixing layer. Alternatively, the pore density of the first fixing layer can be adjusted by adjusting the spacing between adjacent through-holes 201.

[0167] The diameter of a single through-hole 201 on the first fixing layer increases, thus increasing the pore density of the first fixing layer. The spacing between adjacent through-holes 201 on the first fixing layer decreases, thus increasing the pore density of the first fixing layer.

[0168] If z% is greater than 30%, the pore density of the first fixing layer will be too high, resulting in a large contact area between the electrolyte and the adhesive part 22. The adhesive part 22 will swell and lose its adhesive strength, causing the first fixing layer to detach and making the battery cell prone to material loss. If z% is less than 1%, the pore density of the first fixing layer will be too low, resulting in a greater obstruction to lithium-ion transport, making lithium plating more likely and forming lithium dendrites, which can easily lead to short circuits between the electrodes 10 of the battery cell. When z% is greater than or equal to 1% and less than or equal to 30%, lithium plating is less likely, short circuits between the electrodes 10 of the battery cell are less likely, and material loss from the battery cell is less likely.

[0169] x, y, and z satisfy the condition: 0.0011 ≤ (x×y) / z ≤ 1.195. (x×y) / z can take values ​​of 0.0011, 0.01, 0.1, 1, 1.1, or 1.195, etc. Compared to (x×y) / z being greater than 1.195 and less than or equal to 3.6305, (x×y) / z being less than or equal to 1.195 reduces the likelihood of lithium plating, thus lowering the risk of thermal runaway during battery use. Compared to (x×y) / z being greater than or equal to 0.0005 and less than 0.0011, (x×y) / z being greater than or equal to 0.0011 reduces the likelihood of the fixing layer 20 detaching, thus increasing the overall energy density of the battery. With (x×y) / z greater than or equal to 0.0005 and (x×y) / z less than or equal to 1.195, lithium plating is less likely to occur, resulting in a lower risk of thermal runaway during battery use. Furthermore, the fixed layer 20 is less likely to detach, thus improving the overall energy density of the battery.

[0170] It should be noted that, in this embodiment, the wound cell 1 can satisfy only that z% is greater than or equal to 1% and less than or equal to 30%, or only that (x×y) / z is greater than or equal to 0.0011 and less than or equal to 1.195, or simultaneously satisfy z% is greater than or equal to 1% and less than or equal to 30%, and (x×y) / z is greater than or equal to 0.0011 and less than or equal to 1.195.

[0171] In one possible implementation, the fixing layer 20 includes an insulating film 21 and an adhesive portion 22. The adhesive portion 22 is coated on the insulating film 21, and the insulating film 21 is bonded to the electrode 10 through the adhesive portion 22. A through hole 201 is provided on the insulating film 21. During battery operation, lithium ions can pass through the through hole 201, which can improve the lithium ion transport rate.

[0172] In some examples, the electrode 10 is provided with an active material layer 102, which is disposed opposite to the through hole 201 (see [reference]). Figure 3 z satisfies: 3% ≤ z% ≤ 30%.

[0173] If z% is greater than 30%, the pore density of the first fixing layer will be too high, resulting in a large contact area between the electrolyte and the bonding portion 22 at the active material layer 102. This bonding portion 22 will swell and lose its adhesive strength, causing the first fixing layer to detach and making the cell prone to material loss. If z% is less than 3%, the pore density of the first fixing layer will be too low, resulting in a large obstruction to lithium-ion transport in the portion corresponding to the first fixing layer and the active material layer 102. This can easily lead to lithium plating and the formation of lithium dendrites, making short circuits between the electrodes 10 of the cell more likely. When z% is greater than or equal to 3% and less than or equal to 30%, lithium plating is less likely, short circuits between the electrodes 10 of the cell are less likely, and material loss from the cell is less likely.

[0174] See in some examples Figure 9 The inactive material region 101 is positioned opposite to the through hole 201, and z satisfies: 1% ≤ z% ≤ 20%.

[0175] If z% is greater than 20%, the pore density of the first fixing layer will be too high, resulting in a large contact area between the electrolyte and the bonding portion 22 at the inactive material region 101. The bonding portion 22 will swell and lose its adhesive strength, causing the first fixing layer to detach and making the cell prone to material loss. If z% is less than 1%, the pore density of the first fixing layer will be too low, resulting in a large obstruction to lithium-ion transport in the portion corresponding to the first fixing layer and the inactive material region 101. This can easily lead to lithium plating and the formation of lithium dendrites, making short circuits between the electrodes 10 of the cell more likely. When z% is greater than or equal to 1% and less than or equal to 20%, lithium plating is less likely, short circuits between the electrodes 10 of the cell are less likely, and material loss from the cell is less likely.

[0176] See in some examples Figure 10 A blank area 202 is provided on the adhesive portion 22. The ratio of the area of ​​the blank area 202 to the area of ​​the adhesive portion 22 is greater than or equal to 0.05 and less than or equal to 0.5. The blank area 202 is provided on the adhesive portion 22, and the ratio of the area of ​​the blank area 202 to the area of ​​the adhesive portion 22 can be 0.05, 0.1, 0.2, 0.3, or 0.5, etc.

[0177] The part of the adhesive portion 22 without adhesive is the blank area 202.

[0178] If the ratio of the area of ​​the blank area 202 to the area of ​​the adhesive portion 22 is greater than 0.5, the area of ​​the blank area 202 will be too large, resulting in an insufficient bonding area between the fixing layer 20 and the electrode 10. This leads to low bonding strength between the fixing layer 20 and the electrode 10, making the fixing layer 20 prone to detachment. If the ratio of the area of ​​the blank area 202 to the area of ​​the adhesive portion 22 is less than 0.5, the area of ​​the blank area 202 will be too small, resulting in an excessively large bonding area between the fixing layer 20 and the electrode 10. In this case, the fixing layer 20 will hinder lithium-ion transport, leading to easy lithium plating. By ensuring that the ratio of the area of ​​the blank area 202 to the area of ​​the adhesive portion 22 is greater than or equal to 0.05 and less than or equal to 0.5, the fixing layer 20 is less likely to detach and lithium plating is less likely to occur during battery operation.

[0179] See in some examples Figure 10 A blank area 202 is provided on the adhesive part 22. In the winding direction of the winding cell 1, the blank area 202 is provided on both sides of the fixing layer 20.

[0180] See in some examples Figure 11 A blank area 202 is provided on the adhesive part 22. In the winding direction of the winding cell 1, the blank area 202 is located in the middle of the fixing layer 20.

[0181] In some examples, a blank area 202 is provided on the adhesive portion 22, and the blank area 202 is disposed opposite to the through hole 201. Compared with the adhesive portion of the adhesive portion 22 being disposed opposite to the through hole 201, the placement of the blank area 202 opposite to the through hole 201 can improve the lithium-ion transport rate during battery operation.

[0182] In one possible implementation, the first turn of the electrode 10 closest to the beginning 1010 of the winding cell 1 is designated as the first turn, and the bend 100 of the first turn is a crease, which is covered by the fixing layer 20. This arrangement effectively reduces the risk of material loss at the crease by covering it with the fixing layer 20, as stress is concentrated in the first turn.

[0183] In the winding direction of the battery cell 1, the distance by which the end of the fixing layer 20 extends beyond the crease is greater than or equal to 3 mm. If the distance by which the end of the fixing layer 20 extends beyond the crease is less than 3 mm in the winding direction of the battery cell 1, the size of the fixing layer 20 will be smaller in the winding direction of the battery cell 1, and the fixing layer 20 will be more likely to fall off. By ensuring that the distance by which the end of the fixing layer 20 extends beyond the crease is greater than or equal to 3 mm in the winding direction of the battery cell 1, the fixing layer 20 is less likely to fall off.

[0184] Secondly, see Figure 12 and Figure 13This application provides a battery including a housing 2 and a wound cell 1. The housing has a first surface 200 and a second surface 210 disposed opposite to each other in the height direction of the wound cell 1. An injection hole 300 is provided on the first surface 200. The housing 2 forms a receiving space, and the wound cell 1 is disposed in the receiving space.

[0185] The wound battery cell 1 in this embodiment has the same structure as the wound battery cell 1 provided in any of the above embodiments, and can bring the same or similar technical effects. It will not be described in detail here, but can be referred to the description of the above embodiments.

[0186] The housing 2 is a component used to provide a receiving space to house the wound battery cell 1 and other components and isolate them from the outside environment. The housing 2 includes a body and a cover plate with an opening and a receiving cavity at at least one end. The opening of the body can be closed by the cover plate to seal and isolate the internal environment of the battery from the external environment.

[0187] The material of the shell 2 includes, but is not limited to, metals or alloys such as copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium.

[0188] In one possible implementation, in the height direction of the wound cell 1, the inactive material region 101 and the first surface 200 of the wound cell 1 are located on the same side of the active material layer 102 of the wound cell 1. This arrangement reduces the immersion of the fixing layer 20 on the active material layer 102 of the wound cell 1 by the electrolyte, making it less likely for the fixing layer 20 on the active material layer 102 of the wound cell 1 to detach, reducing material loss from the wound cell, and thus improving the overall energy density of the battery.

[0189] In some examples, the distance between the first surface 200 and the inactive material region 101 in the height direction of the wound cell 1 is A12mm, where A12 satisfies: 4mm≤A12mm≤8.5mm. The value of A12mm can be 4mm, 4.5mm, 5mm, 6mm, 7mm, 8mm, or 8.5mm, etc.

[0190] If A12mm is greater than 8.5mm, the distance between the first surface 200 and the inactive material region 101 is too far in the height direction of the wound cell 1, which will affect electrolyte wetting, hinder lithium-ion transport, and lead to easy lithium plating. If A12mm is less than 4mm, the distance between the first surface 200 and the inactive material region 101 is too close in the height direction of the wound cell 1, which will cause the fixing layer 20 at the opening edge of the wound cell 1 to swell and lose its adhesiveness under the immersion of electrolyte, making the fixing layer 20 easy to fall off. By having A12mm greater than or equal to 4mm and less than or equal to 8.5mm, lithium plating is not easy during battery operation, and the fixing layer 20 is not easy to fall off.

[0191] Thirdly, embodiments of this application provide an electrical device including the battery of the second aspect.

[0192] The battery in this embodiment has the same structure as the battery provided in any of the above embodiments and can bring the same or similar technical effects. It will not be described in detail here. For details, please refer to the description of the above embodiments.

[0193] Batteries can serve as the operating power source for electrical devices, or as the driving power source for electrical devices, replacing or partially replacing fuel or natural gas to provide driving power for vehicles.

[0194] Electrical devices include energy storage equipment, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and devices in the aerospace field.

[0195] The battery pack provided in this application will be described in detail below through specific embodiments.

[0196] Preparation of lithium-ion batteries

[0197] (1) Preparation of the positive electrode:

[0198] The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet is obtained.

[0199] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0200] (2) Preparation of negative electrode:

[0201] The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0202] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0203] (3) Preparation of electrolyte:

[0204] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0205] (4) Preparation of the diaphragm:

[0206] Polyethylene film is selected as the diaphragm.

[0207] (5) Preparation of lithium-ion batteries:

[0208] The positive electrode, separator, and negative electrode are stacked in sequence to form a bare wound battery cell 1. Before stacking, a fixing layer 20 is attached to the corresponding bending portion 100 of the wound cell 1. The bare wound cell 1 is placed in the battery casing 2, which is a square casing. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0209] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate.

[0210] The negative electrode active material can be selected from one or more of the following negative electrode active main materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.

[0211] The following steps can be used to test pore density:

[0212] Remove the fixation layer 20 from the battery sample as a sample, and dry the fixation layer 20 in an environment of 60°C for 60 minutes. After ensuring that the sample is dry, measure the length and width of the fixation layer 20 sample with a micrometer and calculate the sample area.

[0213] The pore structure of the through holes 201 in the fixed layer 20 sample was observed by scanning electron microscopy (SEM), and the total area of ​​the through holes 201 in the fixed layer 20 sample was measured.

[0214] Pore ​​density calculation formula: Pore density = (Total area of ​​through holes 201 / Sample area) × 100%.

[0215] Regarding the testing method for x:

[0216] Discharge the battery to the lower limit voltage, remove the electrode 10 with the fixing layer 20, and measure the dimension of the inactive material region 101 along the height direction of the wound cell 1 using vernier calipers (accuracy 0.1mm). Record this as B1mm, and the dimension of the electrode 10 as x1mm. Calculate the value of x using the formula x=B1 / x1. When the positive electrode active material of the battery is lithium nickel cobalt manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate, the lower limit voltage is 2.5V; when the positive electrode active material is lithium nickel manganese oxide, the lower limit voltage is 3.5V.

[0217] Regarding the testing method for y:

[0218] Discharge the battery to the lower limit voltage, remove the electrode 10 with the fixing layer 20, and use a vernier caliper (accuracy 0.1mm) to measure the distance from the first end 1010 of the electrode 10 to the fixing layer 20 closest to the first end 1010 along the winding direction of the wound cell 1. Record the dimension of the fixing layer 20 on the side furthest from the first end 1010 as L1mm, and the dimension of the fixing layer 20 as L2mm. Along the height direction of the wound cell 1, measure the dimension of the electrode 10 as x1mm, and the bonding dimension between the fixing layer 20 closest to the first end 1010 and the electrode 10 as x2mm. S1 = x2 × L2. S2 = x1 × L1. Calculate the value of y using the formula y = S1 / S2. When the positive electrode active material of the battery is lithium nickel cobalt manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate, the lower limit voltage is 2.5V; when the positive electrode active material is lithium nickel manganese oxide, the lower limit voltage is 3.5V.

[0219] If (x×y) / z is too small, the fixing layer is prone to falling off. The test method is as follows:

[0220] Following the battery fabrication method described above, 200 lithium-ion batteries were prepared for each embodiment and comparative example. Specifically, in the height direction of the wound cell 1, the ratio of the total size of the inactive material region 101 to the size of the electrode 10 is x; the bonding area between the first fixing layer and the electrode 10 is S1 mm. 2 The area of ​​the first region is S2mm 2 The ratio of S1 to S2 is y; the pore density of the first fixing layer is z% (see Table 1). All other structures are the same. The lithium-ion batteries of each embodiment and comparative example were cycle-tested at 25°C according to the following procedure, and the detachment of the fixing layer 20 was tested.

[0221] For lithium iron phosphate lithium-ion batteries:

[0222] 1) Charge at a constant current rate of 1C to 3.65V, and then charge at a constant voltage until the current drops to 0.05C;

[0223] 2) Let it stand for 30 minutes;

[0224] 3) Discharge to 2.5V at a 1C rate;

[0225] 4) Let it stand for 30 minutes;

[0226] Repeat steps 1)-4) for 100 cycles.

[0227] For nickel-cobalt-manganese ternary lithium-ion batteries:

[0228] 1) Charge at a constant current rate of 1C to 4.35V, and then charge at a constant voltage until the current drops to 0.05C;

[0229] 2) Let it stand for 20 minutes;

[0230] 3) Discharge to 2.75V at a 1C rate;

[0231] 4) Let it stand for 20 minutes;

[0232] Repeat steps 1)-4) for 100 cycles.

[0233] After cycling, the lithium-ion battery was placed in a vibration table and subjected to random vibration in the Z / Y / X directions and sinusoidal fixed-frequency vibration under the conditions of GB38031-2020.8.2. The random vibration duration in each direction was 12 hours and the sinusoidal fixed-frequency vibration duration was 2 hours. Then, the lithium-ion battery was removed and disassembled. The electrode 10 with the fixing layer 20 was taken out and made into a sample. The width of the fixing layer 20 in the sample is the size of the fixing layer 20 in the electrode unfolding direction, and the length of the fixing layer 20 in the sample is the size of the fixing layer 20 in the height direction of the wound cell 1, i.e., the Z direction. The peel strength of the fixing layer 20 in the sample was measured using a universal tensile testing machine at 300 mm / min, with the fixing layer 20 fixed at one end and the electrode 10 fixed at the other end, and the test angle was 180°. If the peel strength is less than 0.5 N / cm, the fixing layer 20 has fallen off; otherwise, the fixing layer 20 has not fallen off. The number of lithium-ion batteries with the fixing layer 20 falling off was recorded as n. The percentage of batteries in different embodiments and comparative examples where the fixed layer 20 has detached is calculated using the formula (n / 200) × 100%. This percentage is the detachment rate of the fixed layer 20. If the detachment rate is less than or equal to 3%, it is considered good. If the detachment rate is greater than 3% but less than or equal to 5%, it is considered qualified. Otherwise, it is considered unqualified. In other words, if the detachment rate is less than or equal to 5%, it is considered qualified. If the detachment rate is greater than 5%, it is considered unqualified.

[0234] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0235] If (x×y) / z is too large, lithium plating is likely to occur. The test method is as follows:

[0236] According to the above battery preparation method, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. In the lithium-ion batteries obtained in each embodiment and comparative example, the ratio of the total size of the inactive material region 101 to the size of the electrode 10 in the height direction of the wound cell 1 is x; the bonding area between the first fixing layer and the electrode 10 is S1 mm. 2 The area of ​​the first region is S2mm 2 The ratio of S1 to S2 is y; the pore density of the first fixed layer is z% (see Table 1). All other structures are the same. The lithium-ion battery is charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged at a constant voltage until the current drops to 0.05C. After resting for 5 minutes, the battery is discharged at a constant current of 0.33C to the lower limit voltage. This constitutes one cycle. 2000 cycles are performed. Then, the lithium-ion battery is charged at 0.33C to the upper limit voltage, with a cutoff current less than or equal to 0.05C, resulting in a fully charged battery.

[0237] Disassemble the battery, then remove the electrodes and observe the lithium plating on the surface of the negative electrode at the 100-degree bend.

[0238] In the thickness direction of electrode 10, the portion where the projection of a single fixing layer 20 coincides with that of the negative electrode is the first region, and the lithium deposition area of ​​the first region is measured and recorded as S3mm. 2 The area of ​​the active material layer 102 in the first region is S4mm. 2 According to the formula, the percentage of lithium deposition area on the surface of the negative electrode at the 100° bend is calculated as (S3 / S4)×100%. If the percentage of lithium deposition area on the surface of the negative electrode at the 100° bend is less than 10%, it is considered slight lithium deposition. If the percentage of lithium deposition area on the surface of the negative electrode at the 100° bend is between 10% and 50%, it is considered moderate lithium deposition. Both slight and moderate lithium deposition are acceptable. If the percentage of lithium deposition area on the surface of the negative electrode at the 100° bend is greater than 50%, it is considered severe lithium deposition. Severe lithium deposition is unacceptable.

[0239] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0240] In this test, the positive electrode active material of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder satisfies 95:2:1:2.

[0241] Table 1

[0242]

[0243] Compared to Comparative Example 1 and Comparative Example 4, when x, y, and z satisfy: 0.0005≤(x×y) / z, the fixation layer detachment is acceptable. Restricting x, y, and z to meet this condition makes the fixation layer less prone to detachment.

[0244] Compared to Comparative Examples 2 and 3, when x, y, and z satisfy (x×y) / z≤3.6305, there is no severe lithium plating. Restricting x, y, and z to satisfy this condition can make the battery less prone to lithium plating.

[0245] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A wound battery cell, characterized in that, include: An electrode sheet is bent to form a bent portion. The starting end of the winding of the electrode sheet is the first end of the electrode sheet. The electrode sheet is provided with an active material layer. In the height direction of the wound cell, at least one end of the electrode sheet is formed with an inactive material region. The ratio of the total size of the inactive material region to the size of the electrode sheet is x. A fixing layer is at least partially adhered to the active material layer located at the bend, and at least partially adhered to the inactive material area located at the bend, and the fixing layer is provided with through holes; In the winding direction of the wound cell, the fixing layer closest to the first end of the electrode is the first fixing layer. A first region is formed between the edge of the first fixing layer away from the first end of the electrode and the first end of the electrode. The bonding area between the first fixing layer and the electrode is S1mm. 2 The area of ​​the first region is S2mm 2 The ratio of S1 to S2 is y; The pore density of the first fixing layer is z%. The x, y, and z satisfy the condition: 0.0005 ≤ (x × y) / z ≤ 3.6305.

2. The wound battery cell according to claim 1, characterized in that, In the height direction of the wound cell, the total size of the inactive material region is B1mm, wherein B1 satisfies: 1mm≤B1mm≤10mm; and / or, x satisfies: 0.007≤x≤0.

14.

3. The wound battery cell according to claim 1, characterized in that, In the height direction of the wound cell, the inactive material region is disposed at one end of the electrode, and x satisfies: 0.01≤x≤0.

14.

4. The wound battery cell according to claim 3, characterized in that, In the height direction of the wound cell, the electrode has a first end close to the inactive material region and a second end away from the inactive material region. The distance between the end of the fixing layer away from the inactive material region and the second end is A1 mm, where A1 satisfies: 0.1 mm ≤ A1 mm ≤ 10 mm.

5. The wound battery cell according to claim 4, characterized in that, In the thickness direction of the electrode sheet, the fixing layer disposed opposite to the first fixing layer on a single bending portion is the second fixing layer. The first fixing layer and the second fixing layer are respectively disposed on both sides of the electrode sheet. In the height direction of the wound cell, the ends of the first fixing layer and the second fixing layer away from the inactive material region extend beyond the second end. The portions of the first fixing layer and the second fixing layer extending beyond the second end are bonded together. The bonding dimension of the ends of the first fixing layer and the second fixing layer away from the inactive material region is A2mm, where A2 satisfies: 0.1mm≤A2mm≤10mm.

6. The wound battery cell according to claim 1, characterized in that, In the height direction of the wound cell, an inactive material region is provided at each of the opposite ends of the electrode. The size of the inactive material region is A3mm, and A3 satisfies: 1mm≤A3mm≤8mm.

7. The wound battery cell according to claim 1, characterized in that, An insulating layer is provided on the inactive material area, and the fixing layer is adhered to the insulating layer.

8. The wound battery cell according to claim 7, characterized in that, The thickness of the active material layer is greater than or equal to the thickness of the insulating layer.

9. The wound battery cell according to claim 8, characterized in that, The difference between the thickness of the active material layer and the thickness of the insulating layer is greater than or equal to 10 μm and less than or equal to 190 μm.

10. The wound battery cell according to claim 7, characterized in that, The active material layer and the insulating layer form an overlapping area. In the height direction of the wound cell, the size of the overlapping area is A4mm, and A4 satisfies: 0.1mm≤A4mm≤3mm.

11. The wound battery cell according to claim 1, characterized in that, In the height direction of the wound cell, the electrode has a first end close to the inactive material region, the first end leads out an electrode tab, and the dimension of the overlapping portion of the fixing layer and the inactive material region is A5mm, wherein A5 satisfies: 0.1mm≤A5mm≤8mm.

12. The wound battery cell according to any one of claims 1-11, characterized in that, In the height direction of the wound cell, the end of the inactive material region away from the active material layer is the outer end of the inactive material region, and the end of the fixing layer does not extend beyond the outer end of the inactive material region.

13. The wound battery cell according to claim 12, characterized in that, In the height direction of the wound cell, the distance between the end of the fixing layer and the outer end of the inactive material region is A6mm, where A6 satisfies: 0.1mm≤A6mm≤2.6mm.

14. The wound battery cell according to any one of claims 1-11, characterized in that, In the height direction of the wound cell, the end of the inactive material region away from the active material layer is the outer end of the inactive material region, and the end of the fixing layer extends beyond the outer end of the inactive material region by a dimension of A7mm, wherein A7 satisfies: 0.1mm≤A7mm≤13mm.

15. The wound battery cell according to claim 14, characterized in that, In the thickness direction of the electrode sheet, the fixing layer disposed opposite to the first fixing layer on a single bending portion is the second fixing layer. The first fixing layer and the second fixing layer are respectively disposed on both sides of the electrode sheet. In the height direction of the wound cell, the ends of the first fixing layer and the second fixing layer away from the inactive material region extend beyond the second end of the electrode sheet. The portions of the first fixing layer and the second fixing layer extending beyond the second end are bonded together. The bonding dimension of the ends of the first fixing layer and the second fixing layer away from the inactive material region is A2mm, where A2 satisfies: 0.1mm≤A2mm≤8mm.

16. The wound battery cell according to claim 14, characterized in that, It also includes a separator that is stacked and wound around the electrode sheet. In the height direction of the wound cell, the dimension of the fixing layer that extends beyond the separator is A8mm, where A8 satisfies: A8mm≤9.4mm.

17. The wound battery cell according to claim 14, characterized in that, It also includes a separator that is stacked and wound around the electrode sheet, wherein, in the height direction of the wound cell, the outer end of the fixing layer does not extend beyond the end of the separator.

18. The wound battery cell according to claim 14, characterized in that, The thickness of the electrode is greater than or equal to 70 μm.

19. The wound battery cell according to any one of claims 1-11, characterized in that, S2 satisfies: 6300mm 2 ≤S2mm 2 ≤116800mm 2 The given y satisfies: 0.014≤y≤0.

27.

20. The wound battery cell according to any one of claims 1-11, characterized in that, In the winding direction of the wound cell, a tab is provided between the first end of the electrode sheet and the first fixing layer. The distance between the tab and the first fixing layer is A9mm, and A9 satisfies: 15mm≤A9mm≤250mm.

21. The wound battery cell according to any one of claims 1-11, characterized in that, The electrode sheet is provided with tabs. In the winding direction of the wound cell, the tab closest to the beginning of the electrode sheet is the first tab. A first fixing layer is provided between the beginning of the electrode sheet and the first tab. The distance from the first tab to the first fixing layer is A10mm. A10 satisfies: 25mm≤A10mm≤250mm.

22. The wound battery cell according to any one of claims 1-11, characterized in that, Along the length of the wound cell, the electrode has two oppositely arranged bending portions, and each bending portion is provided with a fixing layer.

23. The wound battery cell according to any one of claims 1-11, characterized in that, The electrode sheet has a fixing layer within 5 turns of the first end of the electrode sheet in the wound cell.

24. The wound battery cell according to any one of claims 1-11, characterized in that, In the winding direction of the wound cell, the size of the fixing layer is A11mm, and A11 satisfies: 10mm≤A11mm≤30mm.

25. The wound battery cell according to any one of claims 1-11, characterized in that, The z satisfies: 1% ≤ z% ≤ 30%; and / or, the x, the y, and the z satisfy: 0.0011 ≤ (x × y) / z ≤ 1.1952.

26. The wound battery cell according to any one of claims 1-11, characterized in that, The fixing layer includes an insulating film and an adhesive portion. The adhesive portion is coated on the insulating film, and the insulating film is bonded to the electrode through the adhesive portion. The through hole is provided on the insulating film.

27. The wound battery cell according to claim 26, characterized in that, The active material layer is disposed opposite to the through hole, and z satisfies: 3% ≤ z% ≤ 30%.

28. The wound battery cell according to claim 26, characterized in that, The inactive material region is positioned opposite to the through hole, and z satisfies: 1% ≤ z% ≤ 20%.

29. The wound battery cell according to claim 26, characterized in that, The adhesive portion has a blank area, and the ratio of the area of ​​the blank area to the area of ​​the adhesive portion is greater than or equal to 0.05 and less than or equal to 0.

5.

30. The wound battery cell according to claim 26, characterized in that, The adhesive portion has a blank area, which is located on both sides of the fixing layer in the winding direction of the wound battery cell; and / or, the adhesive portion has a blank area, which is located in the middle of the fixing layer in the winding direction of the wound battery cell.

31. The wound battery cell according to claim 26, characterized in that, The adhesive portion has a blank area, which is positioned opposite to the through hole.

32. The wound battery cell according to any one of claims 1-11, characterized in that, The first turn of the electrode closest to the beginning of the electrode in the wound cell is called the first turn, and the bend in the first turn is called the crease. The fixing layer covers the crease.

33. The wound battery cell according to claim 32, characterized in that, In the winding direction of the wound cell, the distance by which the end of the fixing layer extends beyond the crease is greater than or equal to 3 mm.

34. A battery, characterized in that, The device includes a housing and a wound battery cell as described in any one of claims 1-33, wherein the housing has a first surface in the height direction of the wound battery cell, the first surface is provided with a liquid injection hole, the housing forms a receiving space, and the wound battery cell is disposed in the receiving space.

35. The battery according to claim 34, characterized in that, In the height direction of the wound cell, the inactive material region of the wound cell and the first surface are located on the same side of the active material layer of the wound cell.

36. The battery according to claim 35, characterized in that, In the height direction of the wound cell, the distance between the first surface and the inactive material region is A12mm, where A12 satisfies: 4mm≤A12mm≤8.5mm.

37. An electrical device, characterized in that, Includes the battery as described in any one of claims 34-36.

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