Secondary battery, battery pack, and electronic device

Abstract

The present application provides a secondary battery, a battery pack, and an electronic device, the secondary battery comprising: a case including an end wall and a side wall surrounding the end wall, the end wall having an opening portion; the electrode assembly is accommodated in the shell and comprises a positive electrode piece, a negative electrode piece and a diaphragm, the negative electrode piece comprises a negative electrode current collector and a negative electrode active material layer, and the direction from a negative electrode uncoated area to a negative electrode coated area of the negative electrode current collector is a preset direction; the pole penetrates through the opening part and is fixed on the end wall; the current collecting disc is arranged between the electrode assembly and the end wall and electrically connected with the electrode assembly and the pole, the electrode assembly comprises a first area far away from a center hole of the electrode assembly and a second area close to the center hole in the radial direction of the electrode assembly, and the first area and the second area are arranged in the projection range of the first area in the first direction. The minimum distance LA mm between the surface, facing the electrode assembly, of the current collecting disc and the first end, in the first direction, of the negative electrode active material layer is larger than or equal to 1.5 mm. According to the technical scheme, at least the safety of the battery in the use process can be improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and more specifically, to a secondary battery, a battery pack, and an electronic device. Background Technology

[0002] In the field of new energy power batteries, the application of rechargeable batteries is becoming increasingly widespread. These batteries (such as lithium-ion batteries) can be used in vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, e-cigarettes, digital products, power tools, power units, and other electronic devices. One type of rechargeable battery is the cylindrical battery, which includes a casing and an electrode assembly. The electrode assembly consists of a positive electrode, a first separator, a negative electrode, and a second separator, which are stacked sequentially and wound to form the electrode assembly, which is then encapsulated within the casing. However, existing rechargeable batteries still require further improvement in terms of safety. Utility Model Content

[0003] In view of the problems existing in the related technologies, the purpose of this utility model is to provide a secondary battery, battery pack and electronic device that can at least improve the safety of the battery during use.

[0004] To achieve the above objectives, embodiments of this application provide a secondary battery, comprising: a casing including an end wall and a side wall surrounding the end wall, the end wall having an opening; and an electrode assembly housed within the casing, including a negative electrode, a positive electrode, and a separator disposed between the negative and positive electrode, wherein the negative electrode includes a negative current collector and a negative active material layer coated on a portion of the surface of the negative current collector, the negative current collector including a negative electrode coated area covered by the negative active material layer and a negative electrode uncoated area not covered by the negative active material layer. The direction from the uncoated area to the coated area is a preset direction; the electrode post passes through the opening and is fixed to the end wall, and is insulated from the end wall; the current collector is disposed between the electrode assembly and the end wall, and electrically connects the electrode assembly and the electrode post; along the radial direction of the electrode assembly, the electrode assembly includes a first region away from the central hole of the electrode assembly and a second region close to the central hole; the negative electrode active material layer has a first end along the preset direction; within the projection range of the first region along the preset direction, one surface of the current collector faces the electrode assembly; the minimum distance between the surface of the current collector and the first end along the preset direction is L. A mm, L A mm ≥ 1.5 mm.

[0005] In some embodiments, 6mm≥L A mm ≥ 1.5mm; the maximum height of the secondary battery is H mm, H / L A The value range is 13-100.

[0006] In some embodiments, within the projection range of the second region along a preset direction, the minimum distance between the surface of the collector disk and the first end along the preset direction is L. B mm, 6mm≥L B mm ≥ 1.34 mm.

[0007] In some embodiments, the electrode assembly further includes a third region along the radial direction of the electrode assembly. This third region is closer to the central hole than the second region. Within the projection range of the third region along a predetermined direction, the minimum distance L between the surface of the collector disk and the first end along the predetermined direction is [value missing]. C mm, 6mm≥L C mm ≥ 1.1 mm.

[0008] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer. The positive current collector includes a positive coated area covered by the positive active material layer and a positive uncoated area not covered by the positive active material layer. The positive coated area to the positive uncoated area is a preset direction. Along the preset direction, the positive uncoated area includes a positive electrode tab and a positive connection area connected between the positive electrode tab and the positive coated area. The electrode assembly also includes an insulating layer that covers the positive connection area. The width of the insulating layer in the preset direction ranges from 1.9 mm to 2.7 mm.

[0009] In some embodiments, the width of the insulating layer in a predetermined direction is greater than 2 mm.

[0010] In some embodiments, the insulating layer includes a first end in a predetermined direction, and the first end of the negative electrode active material layer extends beyond the first end of the insulating layer by a distance greater than 0.9 mm in the predetermined direction.

[0011] In some embodiments, the side of the terminal post opposite to the electrode assembly has a hole recessed toward the electrode assembly; the secondary battery also includes a sealing pin that covers the blind hole.

[0012] In some embodiments, the secondary battery further includes a cover plate that seals the opening to encapsulate the electrode assembly inside the housing; the hole is a blind hole, and the cover plate has a liquid injection hole that passes through the cover plate, and the bottom surface of the blind hole has a weld mark formed by welding the electrode post and the current collector.

[0013] Embodiments of this application also provide a battery pack comprising the aforementioned secondary battery.

[0014] Embodiments of this application also provide an electronic device that includes the battery pack described above.

[0015] Because the first region of the electrode assembly is close to the side of the housing, and the side of the housing is highly susceptible to compression. The technical solution of this application addresses this by minimizing the distance L between the positive current collector corresponding to the first region and the first end of the negative active material layer.A The lower limit of 1.5mm is set to prevent the battery from failing due to compression of the casing, thus improving the safety of the battery during use. Attached Figure Description

[0016] 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.

[0017] Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.

[0018] Figure 2 A perspective view of a secondary battery according to an embodiment of this application is shown.

[0019] Figure 3 A cross-sectional perspective view of a secondary battery according to an embodiment of this application is shown.

[0020] Figure 4 A cross-sectional view of an electrode assembly according to some embodiments is shown.

[0021] Figure 5 The positive electrode plate is shown in Figure 4 A schematic diagram of the cross-section at region A1.

[0022] Figure 6 A partial schematic diagram of the dimensional configuration of a secondary battery on the positive electrode side according to some embodiments is shown.

[0023] Figure 7 An enlarged cross-sectional schematic diagram of a portion of the electrode assembly is shown. Detailed Implementation

[0024] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0025] Embodiments of this application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are represented by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0026] As used herein, the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.

[0027] In this specification, unless otherwise specified or limited, relative terms such as “central,” “longitudinal,” “lateral,” “front,” “rear,” “right,” “left,” “inner,” “outer,” “lower,” “higher,” “horizontal,” “vertical,” “above,” “below,” “above,” “below,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.

[0028] For ease of description, the terms "first," "second," "third," etc., are used herein to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe corresponding components. Furthermore, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Secondary batteries (such as large cylindrical battery products like 4680, 4695, and 46120) require shoulder dynamic compression testing to simulate battery safety under compression. For example, batteries installed in vehicles are sometimes subjected to compression during use. Shoulder dynamic compression testing typically uses a blunt-tipped tool to compress the battery at a pressure of, for example, 500N at a speed of 1m / s along the positive electrode edge, displacing the battery by 4mm. Shoulder dynamic compression testing requires no fire, smoke, or explosion. However, with existing designs regarding the distance from the lower end face of the positive current collector towards the electrode assembly to the edge of the active material layer of the negative electrode and the width of the insulating layer of the positive electrode, shoulder dynamic compression testing can probabilistically result in fire and / or short circuits. For example, some test results show a 2 / 6 probability of fire and a 3 / 6 probability of internal short circuit, which does not meet customer requirements. This indicates that under existing secondary battery designs, batteries are prone to fire and / or internal short circuits when compressed during use. Therefore, the pass rate of the shoulder dynamic compression test needs to be improved, which can improve the safety of the battery during use.

[0030] This application provides an electronic device 1000. For ease of explanation, the following embodiments use a vehicle as an example to illustrate the electronic device 1000. See also... Figure 1The vehicle has a battery pack 1002 installed inside, which can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The working part of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part is the vehicle body, and the battery pack 1002 is located at the bottom of the vehicle body, providing electrical power for the vehicle's movement or the operation of its internal electrical components. However, in some other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part can obtain electrical energy from the battery pack 1002 and perform corresponding functions, such as a fan blade rotation unit or a vacuum cleaner's suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1000.

[0031] Battery pack 1002 may include multiple secondary batteries (such as...) Figure 2 The secondary battery 100 and the casing that houses multiple secondary batteries are described below. In the following description, a cylindrical battery is used as an example for illustration. Figure 2 A cross-sectional perspective view of a secondary battery 100 according to an embodiment of this application is shown.

[0032] See Figure 2The secondary battery 100 can be a cylindrical battery. The secondary battery 100 may include an electrode assembly 120, an electrolyte, a housing 200, and a cover plate 202. The housing 200 includes a peripheral sidewall 109 and an end wall 111 connected to one end of the peripheral sidewall 109. An opening 205 is provided at the other end of the peripheral sidewall 109 opposite to the end wall 111, and the cover plate 202 covers the opening 205. The cover plate 202 can be used to encapsulate the electrode assembly 120 and the electrolyte together with the housing 200. The housing 200 can be made of any of a variety of available materials, such as copper, iron, aluminum, steel, or aluminum alloy. The housing 200 can be cylindrical and define a receiving cavity in which the electrode assembly 120 is disposed. The outer diameter of the housing 200 can be determined according to the specific diameter of the electrode assembly 120; for example, the outer diameter of the housing 200 can be, for example, 18 mm, 21 mm, or 46 mm. In some embodiments, the secondary battery 100 may be a 4680 cylindrical battery (outer diameter 46mm, height 80mm), or a 4695 cylindrical battery (outer diameter 46mm, height 95mm), or a 46120 cylindrical battery (outer diameter 46mm, height 120mm).

[0033] The electrode assembly 120 can be formed primarily by sequentially stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets (described in detail below). The wound electrode assembly 120 can have a central hole 120c. In some embodiments, the positive electrode sheet may include a positive current collector and a positive active material layer, the positive active material layer being coated on a portion of the surface of the positive current collector. The uncoated positive electrode area 28b of the positive current collector, which is not covered by the positive electrode coating area, can be used to form a positive electrode tab. The negative electrode sheet may include a negative current collector and a negative active material layer, the negative active material layer being coated on a portion of the surface of the negative current collector. The uncoated negative electrode area 18b of the negative current collector, which is not covered by the negative electrode coating area, can be used to form a negative electrode tab.

[0034] An inwardly protruding crimping portion 113 (also referred to as a groove) is formed on the peripheral sidewall of the housing 200 adjacent to the opening 205. An electrode assembly 120 is disposed between the end wall 111 and the crimping portion 113, and the crimping portion 113 restricts the movement of the electrode assembly 120 in the height direction (parallel to the first direction D1) and the opposite direction between the end wall 111 and the crimping portion 113. The end of the peripheral sidewall 109 of the housing 200 on the opening 205 side can be configured as a rolled edge portion 32, which extends radially inward along the housing 200. The rolled edge portion 32 and the crimping portion 113 are spaced apart along the height direction, and the crimping portion 113 and the rolled edge portion 32 can jointly clamp the cover plate 220. The cover plate 220 is electrically insulated from the housing 200.

[0035] The uncoated negative electrode area 18b of the electrode assembly 120 faces the opening 205 and can be electrically connected to the housing 200 via a negative electrode current collector located between the cover plate 220 and the electrode assembly 120, thereby making the housing 200 negatively charged. The negative electrode current collector can be welded to the housing 200 by laser welding. Specifically, the welding position between the negative electrode current collector and the housing 200 is located on the side of the crimp portion 113 facing the electrode assembly 120.

[0036] The cylindrical battery 100 may further include a terminal post 160 that passes through and is insulated from the end wall 111. A positive current collector 202 is disposed between the electrode assembly 120 and the end wall 111. The positive current collector 202 may electrically connect the terminal post 160 and the electrode assembly 120, for example, to the uncoated positive electrode region 28b of the positive electrode sheet, thereby making the terminal post 160 positively charged. In some embodiments, the terminal post 160 may be welded to the positive current collector 202 by laser penetration welding.

[0037] Figure 3 yes Figure 2 A magnified view of a portion of the pole at position 160. See also... Figure 3 As shown, the end wall 111 has an opening 111V. The electrode post 160 passes through the opening 111V and is fixed to the end wall 111. In this embodiment, the electrode post 160 is fixed to the end wall 111 by riveting. The side of the electrode post 160 facing away from the electrode assembly has a hole 117 recessed toward the electrode assembly 120. A sealing pin 211 covers the hole 117. The outer surface edge of the sealing pin 211 can be welded to the sidewall of the hole 117 to form a weld mark 270.

[0038] In some embodiments, the hole 117 may be a through hole, and in such embodiments, the hole 117 may be used for injecting electrolyte. Figure 3 In the illustrated embodiment, hole 117 is a blind hole. The bottom surface of hole 117 has a weld mark 280 formed by welding the electrode post 160 to the positive electrode current collector 202. The weld mark 280 can extend from the electrode post 160 below hole 117 into the positive electrode current collector 202. In the embodiment where hole 117 is a blind hole, an injection hole can be provided in the cover plate 220 to inject electrolyte through the cover plate 220 on the negative electrode side.

[0039] The electrode post 160 is insulated from the end wall 111 by the lower plastic 60 and the upper plastic 70, and the opening 111V is sealed by the sealing element 90. The electrode post 160 can be assembled with the end wall 111 of the housing by riveting. The upper plastic 70 is clamped between the outer flange of the electrode post 160 and the end wall 111, and the lower plastic 60 is clamped between the inner flange of the electrode post 160 and the end wall 111. The upper plastic 70, the lower plastic 60, and the sealing element 90 can each have an annular shape surrounding the electrode post 160.

[0040] In one example of the cylindrical battery 100 of this application, the method for manufacturing the cylindrical battery 100 of this application includes the following steps:

[0041] Winding: A winding structure is formed by stacking and winding the negative electrode sheet, the separator, and the positive electrode sheet. The uncoated negative electrode area 18b of the negative electrode sheet and the uncoated positive electrode area 28b of the positive electrode sheet are used as the positive electrode tab and the negative electrode tab, and the uncoated positive electrode area 28b and the uncoated negative electrode area 18b are bent along the radial direction of the electrode assembly 120.

[0042] Welding of current collectors to electrode assemblies: The positive current collector 202 and the negative current collector are welded to the surface areas of the bent positive uncoated area 28b and negative uncoated area 18b, respectively.

[0043] Installation: The electrode assembly 120, which has been welded to the negative current collector and the positive current collector 202, is installed into the housing 200 through the opening 205. The method of installing the electrode assembly 120 in this step is not limited. For example, it can be installed manually or by a robot.

[0044] Install pole 160.

[0045] Electrolyte injection: The method of electrolyte injection is not limited, and injection can be carried out through opening 205. In this embodiment, electrolyte is injected through opening 205, which reduces the step of opening an injection hole in the end wall 111. The existing opening 205 can be used directly for injection, simplifying the process and reducing costs.

[0046] Sealing: The cover plate 220 is sealed and installed on the opening 205. There are various sealing methods, and this is not limited to one. In some embodiments, a pressing portion 113 recessed towards the center of the housing 200 is first formed by rolling the outer periphery of the housing 200 to restrict the movement of the electrode assembly 120 in the height direction. Then, a mechanical sealing process is used to press and seal the cover plate 220 to form a rolled edge portion 32, thereby sealing and installing the cover plate 220 on the opening 205 of the housing 200. This step is a mature process, low in cost, and highly efficient.

[0047] Figure 4 A cross-sectional view of an electrode assembly 120 according to some embodiments is shown. See also Figure 4 As shown, the electrode assembly 120 is mainly formed by winding a negative electrode 10 and a positive electrode 20, and a separator 122 is provided between the negative electrode 10 and the positive electrode 20. Electrolyte can be filled between the negative electrode 10, the positive electrode 20 and the separator 122.

[0048] The negative electrode 10 may include a negative electrode current collector 18 and a negative electrode active material layer 16. A portion of the opposing surfaces of the negative electrode current collector 18 along its thickness direction is covered by the negative electrode active material layer 16. Therefore, the negative electrode current collector 18 includes a negative electrode coated region 18a covered by the negative electrode active material layer 16 and a negative electrode uncoated region 18b not covered by the negative electrode active material layer 16. The positive electrode 20 includes a positive electrode current collector 28 and a positive electrode active material layer 26. At least a portion of the opposing surfaces of the positive electrode current collector 28 along its thickness direction is covered by the positive electrode active material layer 26. Therefore, the positive electrode current collector 28 includes a positive electrode coated region 28a covered by the positive electrode active material layer 26 and a positive electrode uncoated region 28b not covered by the positive electrode active material layer 26. The direction from the positive electrode coated region 28a to the positive electrode uncoated region 28b is a first direction D1. Furthermore, the direction from the negative electrode uncoated region 18b to the negative electrode coated region 18a is also the first direction D1. The first direction D1 can be referred to as the preset direction, and the first direction D1 is parallel to the height direction of the secondary battery 100. The uncoated negative electrode region 18b of the negative electrode current collector 18 can be used to form a negative electrode tab. The uncoated positive electrode region 28b of the positive electrode current collector 28 can be used to form a positive electrode tab.

[0049] Taking a lithium-ion battery as an example, the material of the negative electrode current collector 18 can be, for example, copper, and the negative electrode current collector 18 can be copper foil. The negative electrode active material of the negative electrode active material layer 16 can be carbon or silicon, etc. The material of the positive electrode current collector 28 can be, for example, aluminum, and the positive electrode active material of the positive electrode active material layer 26 can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The material of the separator 122 can be PP (polypropylene) or PE (polyethylene), etc.

[0050] Figure 5 The positive electrode 20 is shown in Figure 4 A cross-sectional schematic diagram of region A1. (Reference) Figure 5 As shown, the uncoated positive electrode region 28b includes a positive electrode tab 28b2 and a positive electrode connection region 28b1 connecting the positive electrode tab 28b2 and the positive electrode coated region 28a. The positive electrode tab 28b2 may specifically include a positive electrode tab body 28b22 and a positive electrode tab transition 28b21 connecting the positive electrode connection region 28b1 and the positive electrode tab body 28b22.

[0051] The positive electrode tab transition portion 28b21 includes a first positive electrode tab transition endpoint E21 connected to the positive electrode connection region 28b1. The first positive electrode tab transition endpoint E21 is the position where the tangent of the positive electrode tab transition portion 28b21 intersects the extending direction of the positive electrode connection region 28b1. The positive electrode tab transition portion 28b21 also includes a second positive electrode tab transition endpoint E22, the position where the tangent of the positive electrode tab transition portion 28b21 intersects the extending direction of the positive electrode tab body 28b22. An insulating layer 40 covers the positive electrode connection region 28b1. Providing an insulating layer 40 minimizes the possibility of contact between the negative electrode plate 10 and the positive electrode plate 20. The insulating layer 40 can be provided on both sides of the uncoated positive electrode region 28b. The insulating layer 40 can effectively prevent electrical contact between the negative electrode plate 10 and the positive electrode plate 20.

[0052] In some embodiments, the insulating layer 40 is mainly composed of boehmite and PVDF (polyvinylidene fluoride). Boehmite accounts for 80% of the composition, and PVDF accounts for 20%. In some embodiments, the insulating layer is a ceramic material layer. The thickness of the insulating layer 40 is 1.5mm-2.5mm, for example, 1.5mm, 1.7mm, 2mm, 2.1mm, 2.3mm, or 2.5mm. By setting the thickness range of the insulating layer 40, it is avoided that the coating thickness of the insulating layer 40 is too thin, making it difficult to obtain the required electrical insulation and support strength; at the same time, it is avoided that the thickness of the insulating layer 40 is too thick, which may lead to a longer curing time for the coating layer and an increase in the overall structural thickness.

[0053] In some embodiments, the insulating layer 40 includes a color developer to distinguish whether the side coated with the insulating layer 40 is the front or back side of the positive electrode 20 through the color development effect of the color developer, including but not limited to distinguishing the areal density of the front and back sides of the positive electrode 20. The main component of the color developer may be bismuth vanadate, which is yellow in color.

[0054] Figure 6 A partial schematic diagram shows the dimensional configuration of a secondary battery on the positive electrode side according to some embodiments. See also Figure 6 Along the radial direction of the electrode assembly 120, the electrode assembly 12 includes a first region Ra away from the central hole 120c, and a second region Rb closer to the central hole 120c than the first region Ra. The negative electrode active material layer 16 has a first end 16u along a first direction D1. The surface 202s of the positive electrode current collector 202 faces the electrode assembly 120. The minimum distance between the surface 202s of the positive electrode current collector 202 and the first end 16u of the negative electrode active material layer 16 along the first direction D1 is L mm. According to embodiments of this application, this distance L mm has different requirements for different regions of the electrode assembly 120.

[0055] Specifically, within the projection range of the first region Ra along the first direction D1, the minimum distance between the surface 202s of the positive electrode current collector 202 and the first end 16u of the negative electrode active material layer 16 along the first direction D1 is L. A mm, L A mm ≥ 1.5mm. Because the first region Ra is close to the side of the casing, the side is likely to be squeezed under conditions such as battery installation in a vehicle, so the minimum distance L is 1.5mm. A mm has the greatest impact. By using L A The lower limit of mm is set to 1.5mm, which can prevent the battery from failing due to the casing being squeezed, improve the safety of the battery during use, and thus improve the pass rate of the shoulder dynamic compression test.

[0056] In some embodiments, L A The value of mm is in the range of 6 mm ≥ L A mm ≥ 1.5mm. By giving L A Setting the upper limit of mm to 6mm can prevent the distance between the surface 202s of the positive current collector 202 and the first end 16u of the negative active material layer 16 from occupying too much battery height space, thereby improving the energy density of the battery.

[0057] In some embodiments, the maximum height of the secondary battery is H mm. The value of H mm can be, for example, 80 mm (corresponding to a 4680 cylindrical battery), 95 mm (corresponding to a 4695 cylindrical battery), 120 mm (corresponding to a 46120 cylindrical battery), or 150 mm (corresponding to a 46150 cylindrical battery). In some embodiments, H / L A The value range is 13-100. Based on this maximum height H mm, and setting H / L... A The range of values ​​for the ratio can avoid L for secondary batteries of different heights. A The size of the mm value can be adjusted to improve safety and increase the energy density of secondary batteries of different heights.

[0058] In some embodiments, within the projection range of the second region Rb along the first direction D1, the minimum distance along the first direction D1 between the surface 202s of the positive electrode current collector 202 and the first end 16u of the negative electrode active material layer 16 is L. B mm, 6mm≥L B mm ≥ 1.34 mm. (This is in accordance with the requirement of L...) A Based on this, further L B The upper limit for the diameter is controlled to be no less than 1.34 mm, which can reduce the risk of short circuit in the battery under extreme deformation. BControlling the thickness (mm) to no more than 6mm can improve the energy density of the battery. Preferably, it is necessary to simultaneously satisfy L... A mm, L B The above-mentioned value requirements for mm. Combining the test results in Tables 1 and 2 below, if L... A mm, L B If mm does not meet the above value requirements, the failure probability of the shoulder dynamic compression test is >50%; if L A If mm does not meet the above requirements, the failure probability of the shoulder dynamic compression test is >20%.

[0059] In some embodiments, the electrode assembly 120 further includes a third region Rc along its radial direction, the third region Rc being closer to the central hole 120c than the second region Rb. In some embodiments, the electrode assembly 120 can be divided into a first region Ra, a second region Rb, and a third region Rc along its radial direction.

[0060] Within the projection range of the third region Rc along the first direction D1, the minimum distance between the surface 202s of the positive electrode current collector 202 and the first end 16u of the negative electrode active material layer 16 along the first direction D1 is L. C mm, 6mm≥L C mm ≥ 1.1 mm. For L C Controlling the lower limit of mm makes it easier to meet the requirements of L in the manufacturing process. A mm, L B mm control. L C By controlling the thickness to no more than 6 mm, the energy density of the battery can be improved.

[0061] Figure 7 An enlarged cross-sectional schematic diagram of a portion of the electrode assembly is shown. See also Figure 6 and Figure 7 The insulating layer 40 has a width of W1 mm ​​in the first direction. In some embodiments, the value of W1 mm ​​ranges from 1.9 mm to 2.7 mm, i.e., 2.7 mm ≥ W1 mm ​​≥ 1.9 mm. See also Figure 7The insulating layer 40 includes a first end 40u in the first direction D1. By controlling the lower limit of the width W1mm of the insulating layer 40 to be greater than 1.9mm, the distance from the first end 26u of the positive electrode active material layer 26 to the first end 40u of the insulating layer 40 can be improved. The distance by which the first end 16u of the negative electrode active material layer 16 extends beyond the first end 26u of the positive electrode active material layer 26 along the first direction D1 is d mm. The distance by which the first end 40u of the insulating layer 40 extends beyond the first end 16u along the first direction D1 is W1mm-d mm. By controlling the lower limit of the width W1mm of the insulating layer 40 to be greater than 1.9mm, it can be ensured that the distance by which the first end 40u extends beyond the first end 16u is not too small. In some existing secondary batteries, the width of the insulating layer 40 is typically 1.3mm to 2.7mm. According to an embodiment of this application, by controlling the lower limit of the width W1 mm ​​of the insulating layer 40 to be greater than 1.9 mm, the insulating layer 40 can provide some support when the battery fails, thus preventing the battery from catching fire.

[0062] In some embodiments, the distance d mm is typically 1 mm. In such embodiments, the distance by which the first end 16u of the negative electrode active material layer 16 extends beyond the first end 40u of the insulating layer 40 can be no less than 0.9 mm. Because of the presence of the insulating layer 40 extending at least 0.9 mm beyond the first end 16u, the insulating layer 40 can provide some support in the event of battery failure, preventing the battery from catching fire.

[0063] Furthermore, in some embodiments, the width W1 mm ​​of the insulating layer 40 is greater than 2 mm, i.e., 2.7 mm ≥ W1 mm ​​≥ 2 mm. By further strictly controlling the lower limit of the width W1 mm, the supporting effect of the insulating layer in the event of battery failure can be further enhanced, preventing the battery from catching fire.

[0064] Tables 1 and 2 below show the results of shoulder dynamic compression tests on the eight secondary batteries provided in the embodiments of this application and the seven secondary batteries provided in the comparative examples.

[0065] Table 1

[0066]

[0067]

[0068] Table 2

[0069]

[0070] As can be seen from the test results in Tables 1 and 2 above, the pass rate of the dynamic compression test on the shoulder of the secondary battery provided in this application embodiment can reach 100%, with no fire or explosion occurring. This indicates that the safety of the secondary battery under compression during use has been improved.

[0071] In summary, this application addresses the different requirements for distance L mm in different regions by dividing the electrode assembly into zones and controlling the distance L corresponding to each zone. A mm, L B mm, L C The combined constraint of the width W1 mm ​​of the insulation layer with the width W1 mm ​​can prevent the battery from failing due to compression and improve the safety of the battery during use.

[0072] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A secondary battery, characterized in that, include: The housing includes an end wall and a side wall surrounding the end wall, the end wall having an opening; An electrode assembly, housed inside the housing, includes a negative electrode sheet, a positive electrode sheet, and a separator disposed between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet includes a negative current collector and a negative active material layer coated on a portion of the surface of the negative current collector. The negative current collector includes a negative electrode coated area covered by the negative active material layer and a negative electrode uncoated area not covered by the negative active material layer. The direction from the negative electrode uncoated area to the negative electrode coated area is a predetermined direction. The pole, passing through the opening and fixed to the end wall, is insulated from the end wall. A collector plate is disposed between the electrode assembly and the end wall, and is electrically connected to the electrode assembly and the electrode post; Along the radial direction of the electrode assembly, the electrode assembly includes a first region away from the central hole of the electrode assembly and a second region near the central hole, and the negative electrode active material layer has a first end along the predetermined direction. Within the projection range of the first region along the preset direction, one surface of the current collector faces the electrode assembly, and the minimum distance between the surface of the current collector and the first end along the preset direction is L. A mm, L A mm ≥ 1.5 mm.

2. The secondary battery according to claim 1, characterized in that, 6mm≥L A mm≥1.5mm; The maximum height of the secondary battery is H mm, H / L A The value range is 13-100; Within the projection range of the second region along the preset direction, the minimum distance between the surface of the collector disk and the first end along the preset direction is L. B mm, 6mm≥L B mm ≥ 1.34 mm.

3. The secondary battery according to claim 1, characterized in that, Along the radial direction of the electrode assembly, the electrode assembly further includes a third region that is closer to the central aperture than the second region. Within the projection range of the third region along the preset direction, the minimum distance between the surface of the collector disk and the first end along the preset direction is L. C mm, 6mm≥L C mm ≥ 1.1 mm.

4. The secondary battery according to any one of claims 1-3, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector includes a positive electrode coated area covered by the positive active material layer and a positive electrode uncoated area not covered by the positive active material layer. The direction from the positive electrode coated area to the positive electrode uncoated area is the preset direction. Along the predetermined direction, the uncoated positive electrode area includes a positive electrode tab and a positive electrode connection area connecting the positive electrode tab and the coated positive electrode area. The electrode assembly further includes an insulating layer that covers the positive electrode connection area, and the width of the insulating layer in the preset direction ranges from 1.9 mm to 2.7 mm.

5. The secondary battery according to claim 4, characterized in that, The width of the insulating layer in the preset direction is greater than 2 mm.

6. The secondary battery according to claim 4, characterized in that, The insulating layer includes a first end in the preset direction, and the distance by which the first end of the negative electrode active material layer extends beyond the first end of the insulating layer in the preset direction is greater than 0.9 mm.

7. The secondary battery according to claim 1, characterized in that, The side of the electrode post opposite to the electrode assembly has a hole that is recessed toward the electrode assembly; The secondary battery also includes a sealing pin, which covers the hole.

8. The secondary battery according to claim 7, characterized in that, Also includes: A cover plate seals the opening to encapsulate the electrode assembly inside the housing; The hole is a blind hole, and the cover plate has an injection hole that passes through the cover plate. The bottom surface of the blind hole has a weld mark formed by welding the pole and the collector plate.

9. A battery pack, characterized in that, Includes the secondary battery as described in any one of claims 1-8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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