Single battery and battery pack

Abstract

The embodiment of the utility model relates to the technical field of batteries, and particularly discloses a single battery and a battery pack. The electrode assembly is arranged in the shell; the end cover is arranged at one axial end of the shell and is connected with the shell; the current collecting component comprises a current collecting body and an electric connecting part connected with the current collecting body, the current collecting body is arranged between the electrode assembly and the end cover, and the current collecting body is electrically connected with the electrode assembly through the electric connecting part; the current collecting body comprises a welding area, the electric connecting parts are arranged in the welding area, and the multiple electric connecting parts are arranged at intervals in the radial direction. According to the invention, the electronic conduction path in the single battery is optimized, the impedance of the single battery is reduced, the overall overcurrent performance of the single battery is improved, and the rate capability of the single battery is finally improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a single battery and a battery pack. BACKGROUND

[0002] New energy vehicles replace traditional fuel vehicles, which is of great significance to improve the energy and pollution problems faced by the global transportation industry, and is also the trend of the times. With the rapid development of the new energy industry, there is an urgent need for batteries with greater capacity, greater durability, and longer endurance. As one of the core performances of the battery, how to improve the rate performance of the battery becomes a problem to be solved. CONTENT OF THE INVENTION

[0003] Embodiments of the present application provide a single battery and a battery pack to improve the rate performance of the single battery.

[0004] To solve the above technical problems, embodiments of the present application disclose the following technical solutions:

[0005] On the one hand, a single battery is provided, comprising: a shell having an axial direction and a radial direction intersecting each other;

[0006] An electrode assembly is arranged in the shell;

[0007] An end cover is arranged at one end of the shell in the axial direction and connected with the shell;

[0008] A current collecting member includes a current collecting body and an electrical connection part connected with the current collecting body, the current collecting body is arranged between the electrode assembly and the end cover, and the current collecting body is electrically connected with the electrode assembly through the electrical connection part;

[0009] The current collecting body includes a welding area, the electrical connection part is arranged in the welding area, and the electrical connection part is provided with a plurality of electrical connection parts, the plurality of electrical connection parts are arranged at intervals in the radial direction; in the radial direction, the maximum size of each electrical connection part is L1 mm, the distance between the adjacent two electrical connection parts is L2 mm, and the following conditions are met: 0.01≤L1 / L2≤2.

[0010] In addition to one or more features disclosed above, or instead, the maximum size L1 mm of each electrical connection part in the radial direction also meets: 0.1≤L1≤1; and / or,

[0011] The distance L2 mm between the adjacent two electrical connection parts in the radial direction also meets: 0.5≤L2≤10.

[0012] In addition to one or more features disclosed above, or instead, the shell also has a reference plane perpendicular to the axial direction;

[0013] The welding region has a normal projection on the reference plane in the shape of a sector, and two radii of the welding region extend in the radial direction.

[0014] In addition to one or more of the above disclosed features, or alternatively, the sector-shaped projection of the welding region on the reference plane has a central angle of α, satisfying: 9°≤α.

[0015] In addition to one or more of the above disclosed features, or alternatively, the single battery further has a circumferential direction around the axial direction.

[0016] The welding region is provided in a plurality, the plurality of welding regions are arranged in the circumferential direction, and the radii of the plurality of welding regions intersect at a common vertex, and the plurality of welding regions are symmetric about the common vertex.

[0017] In addition to one or more of the above disclosed features, or alternatively, the sum of the central angles of the sector-shaped projections of the plurality of welding regions on the reference plane P is α m , satisfying: 18°≤α m ≤360°.

[0018] In addition to one or more of the above disclosed features, or alternatively, the shell further has a circumferential direction around the axial direction, and a reference plane perpendicular to the axial direction.

[0019] Each electrical connection portion extends in the circumferential direction, and a normal projection of each electrical connection portion on the reference plane is in the shape of an arc around the common vertex; and each welding region is provided with a plurality of electrical connection portions arranged in the radial direction.

[0020] In addition to one or more of the above disclosed features, or alternatively, in the radial direction, the maximum size of the electrical connection portion in the circumferential direction increases in the direction away from the common vertex.

[0021] In addition to one or more of the above disclosed features, or alternatively, the electrode assembly is welded to the current collecting member to form the electrical connection portion.

[0022] In another aspect, a battery pack is further disclosed, in addition to one or more of the above disclosed features, or alternatively, the battery pack includes a box body; and

[0023] The single battery as in any one of the above, the single battery is arranged in the box body.

[0024] One of the above technical solutions has the following advantages or beneficial effects: the application limits the ratio of the maximum size L1 mm of each electrical connection part in the radial direction X and the spacing L2 mm between adjacent two electrical connection parts in the radial direction X to be within the range of 0.01-2, so as to reasonably design the structural size of the electrical connection part on the current collecting member, to optimize the electronic conduction path in the single battery, to reduce the impedance of the single battery, to improve the overall overcurrent performance of the single battery, and finally to improve the rate performance and cycle performance of the single battery. BRIEF DESCRIPTION OF DRAWINGS

[0025] The technical solutions and other beneficial effects of the application will become apparent from the following detailed description of the application, taken in conjunction with the accompanying drawings.

[0026] Fig. 1 is an exploded structural view of a single battery according to an embodiment of the application;

[0027] Fig. 2 is a top view of a current collecting member according to an embodiment of the application;

[0028] Fig. 3 is a top view of a current collecting member according to another embodiment of the application.

[0029] BRIEF DESCRIPTION OF DRAWINGS:

[0030] 100, single battery;

[0031] 110, housing;

[0032] 120, electrode assembly;

[0033] 130, end cover;

[0034] 140, current collecting member; 141, current collecting body; 1411, welding area; 142, electrical connection part. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and beneficial effects of the application clearer and more apparent, the application will be further described in detail below in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described in the specification are only for the purpose of explaining the application, and are not intended to limit the application.

[0036] In the description of the application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0037] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, it can be direct connection, or indirect connection through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0038] In the present application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "under" and "under" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0039] The existing cylindrical secondary battery is a multi-tab or full-tab design, and the tabs are electrically connected with the pole by a current collector plate. The welding track of the current collector plate and the tab in the existing cylindrical secondary battery is linear and distributed along the radial direction of the battery. Due to the different lengths of the tabs at different levels of the inner and outer rings of the electrode assembly in the battery, the conduction current of the tabs gradually increases from the inside to the outside of the electrode assembly, and the overcurrent requirement of the tab welding also gradually increases from the inside to the outside, which cannot meet the requirement of the overcurrent capacity of the tabs for the tabs at different levels of the inner and outer rings, and the performance failure or decay under large rate charging and discharging conditions is easy to occur, which affects the performance of the battery.

[0040] To solve the above problems, in the embodiments of the present application, referring to Figs. 1 to 3 The present application provides a single battery 100.

[0041] Specifically, the single battery 100 comprises a shell 110, an electrode assembly 120, an end cover 130 and a current collecting member 140.

[0042] The shell 110 has an axial direction Z, a radial direction X intersecting the axial direction Z, a circumferential direction R around the axial direction Z and a reference plane perpendicular to the axial direction Z. For example, the shell 110 has an axial direction Z, a radial direction X perpendicular to the axial direction Z, a circumferential direction R around the axial direction Z and a reference plane perpendicular to the axial direction Z.

[0043] The electrode assembly 120 is arranged in the shell 110; the end cover 130 is arranged at one end of the shell 110 in the axial direction Z and connected with the shell 110; the current collecting member 140 comprises a current collecting body 141 and an electrical connection part 142 connected with the current collecting body 141, the current collecting body 141 is arranged between the electrode assembly 120 and the end cover 130, and the current collecting body 141 is electrically connected with the electrode assembly 120 through the electrical connection part 142.

[0044] The single battery 100 can be a secondary battery, which refers to a single battery that can be activated by charging after discharging to continue to use. For example, the single battery 100 can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery or a nickel cadmium battery, but is not limited thereto.

[0045] The single battery 100 can be a prismatic battery, a soft package battery or other shaped battery. For example, in the present application, the single battery 100 is a cylindrical battery.

[0046] The shell 110 described above can be made of a metal or other strength material, but is not limited thereto. For example, the shell 110 described above is made of aluminum profile, but is not limited thereto.

[0047] The end cover 130 can be integrally formed with the shell 110, that is, the end cover 130 can be an outer wall of the shell 110; the end cover 130 can also be fixedly connected with the shell 110, for example, the end cover 130 is fixedly connected with one end of the shell 110 in the axial direction Z through welding or other processes. In this application, no specific limitation is made, and specific settings can be made according to actual conditions. For example, in this application, the end cover 130 is separately provided with the shell 110, and the end cover 130 is fixedly connected with the shell 110 by welding.

[0048] The current collecting member 140 can be a positive current collecting member, and can also be a negative current collecting member, and no specific limitation is made in this application, and specific settings can be made according to actual conditions.

[0049] The material of the current collecting member 140 can be various, for example, the material of the current collecting member 140 can be copper, iron, aluminum, steel or aluminum alloy, but is not limited thereto.

[0050] The electrode assembly 120 is welded with the current collecting member 140 to form an electrical connection part 142. Specifically, the tab in the electrode assembly 120 is welded with the current collecting member 140 to form the electrical connection part 142.

[0051] The single battery 100 further includes electrolyte, pole post and other functional components, the electrolyte can be conventional electrolyte, and can also be special electrolyte added with additives, and the electrolyte is used for soaking the electrode assembly 120. The electrode assembly 120 is a component in which electrochemical reaction occurs in the single battery 100, and the electrode assembly can be one or more. The electrode assembly 120 is mainly formed by winding or stacking the positive plate, the separator and the negative plate. The part of the positive plate and the negative plate having active material constitutes the main part of the electrode assembly 120, and the part of the positive plate and the negative plate not having active material constitutes the tab. In the charging and discharging process of the single battery 100, the positive active material and the negative active material react with the electrolyte, the tab is electrically connected with the pole post through the current collecting member 140 to form a current loop, so that the single battery 100 is normally used.

[0052] Specifically, the current collecting body 141 includes a welding area 1411, the electrical connection part 142 is arranged on the welding area 1411, and the electrical connection part 142 is provided with a plurality of electrical connection parts 142, and the plurality of electrical connection parts 142 are arranged at intervals in the radial direction X, so that the plurality of electrical connection parts 142 are respectively electrically connected with the tabs of different levels in the electrode assembly 120, thereby optimizing the electron conduction path in the single battery 100, reducing the impedance of the single battery 100, and improving the overall overcurrent performance of the single battery 100.

[0053] Specifically, in the radial direction X, the maximum dimension of each of the electrical connection portions 142 is L1 mm, and the interval between the adjacent two electrical connection portions 142 is L2 mm, satisfying: 0.01≤L1 / L2≤2. That is, the ratio of the maximum dimension L1 mm of each of the electrical connection portions 142 in the radial direction X to the interval L2 mm between the adjacent two electrical connection portions 142 in the radial direction X can be controlled within the range of 0.01 to 2. Exemplarily, L1 / L2 can be one of 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, or 2, or a range consisting of any two of them. The above specific values of L1 / L2 are only exemplarily given, and any value within the range of 0.01 to 2 is within the protection scope of the present application.

[0054] In the radial direction X, the maximum dimension L1 mm of each of the electrical connection portions 142 can be obtained by measuring the dimension of different positions of the electrical connection portions 142 on the current collecting member 140 in the radial direction X respectively multiple times and calculating the average value after the actual single battery 100 is disassembled. Exemplarily, the maximum dimension L1 mm of each of the electrical connection portions 142 in the radial direction X can be obtained by measuring the dimension of both end portions of the electrical connection portions 142 on the current collecting member 140 in the radial direction X respectively and measuring the dimension of the middle region of the electrical connection portions 142 on the current collecting member 140 in the radial direction X and calculating the average value. The measuring tool can be any one of a ruler, a vernier caliper, or other size measuring instruments, but is not limited thereto.

[0055] In the radial direction X, the interval L2 mm between the adjacent two electrical connection portions 142 can be obtained by measuring the distance between different positions of the electrical connection portions 142 on the current collecting member 140 in the radial direction X respectively multiple times and calculating the average value after the actual single battery 100 is disassembled. Exemplarily, the interval L2 mm between the adjacent two electrical connection portions 142 in the radial direction X can be obtained by measuring the distance between both end portions of the adjacent two electrical connection portions 142 on the current collecting member 140 in the radial direction X respectively and measuring the distance between the middle regions of the adjacent two electrical connection portions 142 on the current collecting member 140 in the radial direction X and calculating the average value. The measuring tool can be any one of a ruler, a vernier caliper, or other size measuring instruments, but is not limited thereto.

[0056] The present application limits the ratio of the maximum dimension L1 mm of each electric connection part 142 in the radial direction X and the spacing L2 mm between two adjacent electric connection parts 142 in the radial direction X to be within the range of 0.01-2, so as to reasonably design the structural size of the electric connection part 142 on the current collecting member 140, to optimize the electronic conduction path in the single battery 100, to reduce the impedance of the single battery 100, to improve the overall overcurrent performance of the single battery 100, and finally to improve the rate performance and cycle performance of the single battery 100.

[0057] In an embodiment, the maximum dimension L1 mm of each electric connection part 142 in the radial direction X also satisfies: 0.1≤L1≤1, i.e. the maximum dimension L1 mm of each electric connection part 142 in the radial direction X can be controlled within the range of 0.1-1 mm. Exemplarily, L1 mm can be one of 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, or a range consisting of any two of them. The above specific values of L1 mm are only exemplarily given, and any value within the range of 0.1-1 mm is within the protection scope of the present application.

[0058] The present application limits the maximum dimension L1 mm of each electric connection part 142 in the radial direction X to be within the range of 0.1-1 mm, so as to further reasonably design the structural size of the electric connection part 142 on the current collecting member 140, to further optimize the electronic conduction path in the single battery 100, to reduce the impedance of the single battery 100, to improve the overall overcurrent performance of the single battery 100, and finally to improve the rate performance and cycle performance of the single battery 100.

[0059] In an embodiment, the maximum dimension L1 mm of each electric connection part 142 in the radial direction X is uniform.

[0060] The spacing L2 mm between two adjacent electric connection parts 142 in the radial direction X also satisfies: 0.5≤L2≤10, i.e. the spacing L2 mm between two adjacent electric connection parts 142 in the radial direction X can be controlled within the range of 0.5-10 mm. Exemplarily, L2 mm can be one of 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm or 10 mm, or a range consisting of any two of them. The above specific values of L1 mm are only exemplarily given, and any value within the range of 0.5-10 mm is within the protection scope of the present application.

[0061] The application further reasonably designs the structure size of the electric connection part 142 on the current collecting member 140 by limiting the spacing L2 between two adjacent electric connection parts 142 in the radial direction X to be within the range of 0.5mm-10mm, so as to further optimize the electronic conduction path in the single battery 100, reduce the impedance of the single battery 100, improve the overall overcurrent performance of the single battery 100, and finally improve the rate performance and cycle performance of the single battery 100.

[0062] In an embodiment, each electric connection part 142 extends along the circumferential direction R, and the orthographic projection of each electric connection part 142 on the reference plane P is in the shape of an arc around the common vertex Q, and each welding area 1411 is provided with a plurality of electric connection parts 142 arranged at intervals in the radial direction X.

[0063] It can be understood that, since the electrode assembly 120 is formed by winding the pole piece, the pole piece in each coil is in the shape of an arc, and the tabs on each coil of pole piece are also arranged in the shape of an arc. In the application, the orthographic projection of each electric connection part 142 on the reference plane P is limited to be in the shape of an arc, so as to ensure that each electric connection part 142 matches the shape of the tab, further optimizes the electronic conduction path in the single battery 100, and improves the overall overcurrent performance of the single battery 100.

[0064] In an embodiment, in the radial direction X, the maximum size of the electric connection part 142 in the circumferential direction R increases in the direction away from the common vertex Q.

[0065] It can be understood that, since the electrode assembly 120 is formed by winding the pole piece, the lengths of the pole pieces at different levels are different, resulting in different currents conducted by the pole pieces at different levels. In the application, the maximum size of the electric connection part 142 in the circumferential direction R is limited to increase, so as to ensure that different electric connection parts 142 fully match the tabs of the pole pieces at different levels, further optimize the electronic conduction path in the single battery 100, meet the overcurrent demand of the pole pieces at different levels, and improve the overall overcurrent performance of the single battery 100.

[0066] In an embodiment, the current collecting body 141 includes a welding area 1411, the electric connection part 142 is arranged on the welding area 1411, and the orthographic projection of the welding area 1411 on the reference plane P is in the shape of a sector, and the two radii of the welding area 1411 extend along the radial direction X.

[0067] It can be understood that, by limiting the welding area 1411 to be in the shape of a sector, the curvature of the plurality of electric connection parts 142 located in the welding area 1411 is uniform, so as to ensure that each electric connection part 142 meets the overcurrent demand of the electrode assembly 120 at different levels under the smallest area, thereby improving the performance of the single battery 100.

[0068] In an embodiment, the central angle of the fan-shaped projection of the welding region 1411 on the reference plane P is a, and a satisfies: 9°≤a. That is, the central angle a of the fan-shaped projection of the welding region 1411 on the reference plane P is not less than 9°. Exemplarily, the central angle a can be one of 9°, 18°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, 330° or 360°, but is not limited thereto. The above specific values of the central angle a are only exemplarily given, and any value in the range of not less than 9° is within the protection scope of the present application.

[0069] The central angle a of the fan-shaped projection of the welding region 1411 on the reference plane P can be obtained by measuring the central angle of the welding region 1411 on the current collector 140 multiple times after the actual single battery 100 is disassembled and calculating the average value. Exemplarily, the central angle a of the fan-shaped projection of the welding region 1411 on the reference plane P can be obtained by connecting the two ends of any two electrical connection parts 142 located on the same side of the welding region 1411 to generate auxiliary lines, and then measuring the included angle between the two auxiliary lines multiple times by a measuring tool and calculating the average value. The measuring tool can be a protractor, but is not limited thereto.

[0070] The present application limits the central angle a of the fan-shaped projection of the welding region 1411 on the reference plane P to be not less than 9°, so as to ensure that the welding region 1411 has sufficient welding area, and then ensure that the electrical connection part of the welding region 1411 has sufficient connection area and electrical connection with the electrode assembly 120, so as to optimize the electronic conduction path in the single battery 100, reduce the impedance of the single battery 100, improve the overall overcurrent performance of the single battery 100, and finally improve the rate performance of the single battery 100.

[0071] In an embodiment, the welding region 1411 is provided in plurality. Exemplarily, the welding region 1411 can be provided in two, and the welding region 1411 can also be provided in four, but is not limited thereto. The plurality of welding regions 1411 are arranged at intervals along the circumferential direction R, and the radii of the plurality of welding regions 1411 intersect at a common apex Q, and the plurality of welding regions 1411 are centrally symmetric about the common apex Q.

[0072] The central angles of the fan-shaped projections of the plurality of welding regions 1411 on the reference plane P can be the same or different, which is not specifically limited by the present application and can be specifically selected according to the actual situation.

[0073] The non-welding region is formed between the adjacent two welding regions 1411.

[0074] It can be understood that the application sets multiple welding areas 1411 to be electrically connected with the tab of the electrode assembly 120 through the electrical connection part 142 in the multiple welding areas 1411, so as to form multiple current conduction paths between the current collecting member 140 and the tab of the electrode assembly 120, to further optimize the electron conduction path in the single battery 100, reduce the impedance of the single battery 100, improve the overall overcurrent performance of the single battery 100, and finally improve the rate performance of the single battery 100.

[0075] In an embodiment, the sum of the central angles of the fan-shaped projections of the multiple welding areas 1411 on the reference plane P is α m , satisfying: 18°≤α m ≤360°. That is, the sum α m of the central angles of the fan-shaped projections of the multiple welding areas 1411 on the reference plane P can be controlled within the range of 18°-360°. Exemplarily, α m may be one of 18°, 20°, 40°, 60°, 80°, 100°, 120°, 140°, 160°, 180°, 200°, 220°, 240°, 260°, 280°, 300°, 320°, 340° or a range consisting of any two of them. The above specific values of α m are only exemplarily given, and any value within the range of 18°-360° is within the protection scope of the application.

[0076] In an embodiment, the sum of the central angles of the fan-shaped projections of the multiple welding areas 1411 on the reference plane P is α m may be obtained by disassembling the actual single battery 100 and respectively measuring the central angles of the multiple welding areas 1411 on the current collecting member 140 by a measuring tool and summing them up.

[0077] The application controls the sum α m of the central angles of the fan-shaped projections of the multiple welding areas 1411 on the reference plane P within the range of 18°-360°, to further ensure that the welding area 1411 has sufficient welding area, and then ensure that the electrical connection part of the welding area 1411 has sufficient connection area and is electrically connected with the electrode assembly 120, so as to optimize the electron conduction path in the single battery 100, reduce the impedance of the single battery 100, improve the overall overcurrent performance of the single battery 100, and finally improve the rate performance of the single battery 100.

[0078] On the other hand, in the embodiments of the application, the application also provides a battery pack, comprising: a box body; and the single battery 100 according to any one of the above embodiments, which is arranged in the box body.

[0079] The battery pack can be a battery pack with three levels of single battery 100-battery module-battery pack, that is, the single batteries 100 are grouped into battery modules first, and then the battery modules are placed in the box to form the battery pack; or the battery pack with two levels of single battery 100-battery pack, that is, the single batteries 100 are directly accommodated in the box to form the battery pack. In this application, no specific limitation is made, and it can be specifically set according to the actual situation as long as it does not affect the effect of the application.

[0080] In another aspect, in the embodiments of the present application, the present application also provides a power utilization device comprising the battery pack as described above, which serves as a power supply for the power utilization device.

[0081] The power utilization device can be, but is not limited to, a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0082] In order to better understand the technical solutions of the present application, the following takes lithium ion batteries as an example for further explanation and description.

[0083] Embodiment 1

[0084] The present embodiment provides a preparation method of a lithium ion battery, and the specific process is as follows:

[0085] 1. Preparation of positive electrode sheet

[0086] The positive electrode active material is lithium iron phosphate, the conductive agent is conductive carbon black (SP), and the binder is polyvinylidene fluoride (PVDF) with a mass ratio of 96:2:2. Then, N-methyl pyrrolidone (NMP) is added as a solvent for mixing. Stirring is carried out under vacuum until the system appears uniform. The positive electrode slurry is obtained. The positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil. Then, it is transferred to a 120°C oven for drying. Then, after rolling, slitting and cutting, the positive electrode sheet is obtained.

[0087] 2. Preparation of negative electrode sheet

[0088] The negative electrode active material is graphite, the conductive agent is conductive carbon black (SP), the thickening agent is sodium carboxymethyl cellulose (CMC), and the binder is styrene butadiene rubber (SBR) with a mass ratio of 96.2:1.2:1.2:1.4. Then, deionized water is added as a solvent for mixing. Stirring is carried out under vacuum until the system appears uniform. The negative electrode slurry is obtained. The negative electrode slurry is uniformly coated on both sides of the negative electrode current collector copper foil. Then, it is transferred to a 110°C oven for drying. Then, after rolling, slitting and cutting, the negative electrode sheet is obtained.

[0089] 3. Preparation of electrolyte

[0090] Vinyl carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC) were mixed in a mass ratio of 3:4:3 to obtain an organic solvent, 1 mQl / L of LiPF6 was added and mixed uniformly, and then vinylene carbonate, vinyl sulfate and lithium difluorophosphate were added to prepare the electrolyte.

[0091] 4. Preparation of separator

[0092] PP film was used as the separator.

[0093] 5. Preparation of lithium ion battery

[0094] The negative electrode sheet and the positive electrode sheet prepared by the above steps were dried, and then were used together with the separator to prepare a wound electrode roll by using a winding machine. The positive electrode tab and the negative electrode tab were welded on the end cover, and the electrode assembly with the top cover welded was placed in an aluminum shell for packaging. After filling the electrolyte and forming the constant volume, a lithium ion battery was prepared.

[0095] The number of the welding areas on the current collecting member 140 is two, the number of the electrical connection parts 142 in each welding area 1411 is seven, the maximum size L1 of each electrical connection part 142 in the radial direction X is 1 mm, the interval L2 between the adjacent two electrical connection parts 142 in the radial direction X is 2 mm, the ratio L1 / L2 of the maximum size L1 of each electrical connection part 142 in the radial direction X to the interval L2 between the adjacent two electrical connection parts 142 in the radial direction X is 0.5, the central angle a of the fan-shaped projection of the welding area 1411 on the reference plane P is 90°, and the sum a of the central angles of the fan-shaped projections of the plurality of welding areas 1411 on the reference plane P is 180°. m

[0096] In Examples 2 to 16, the lithium ion batteries were prepared according to the method in Example 1, and the differences between Examples 2 to 16 and Example 1 were that the values of L1, L2 and L1 / L2 were changed.

[0097] In Examples 17 to 25, the lithium ion batteries were prepared according to the method in Example 1, and the differences between Examples 17 to 25 and Example 1 were that the number of the welding areas, the values of a and a m were changed.

[0098] Comparative Example 1

[0099] The lithium ion battery was prepared according to the method in Example 1, and the difference was that:

[0100] ​The maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X is 0.09 mm, the interval L2 mm between two adjacent electrical connection portions 142 in the radial direction X is 11 mm, and the ratio L1 / L2 of the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X to the interval L2 mm between two adjacent electrical connection portions 142 in the radial direction X is 0.008.

[0101] Comparative Example 2

[0102] A lithium ion battery was prepared according to the method of Example 1, except that:

[0103] The maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X is 1.2 mm, the interval L2 mm between two adjacent electrical connection portions 142 in the radial direction X is 0.4 mm, and the ratio L1 / L2 of the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X to the interval L2 mm between two adjacent electrical connection portions 142 in the radial direction X is 3.

[0104] Comparative Example 3

[0105] A lithium ion battery was prepared according to the method of Example 1, except that:

[0106] The central angle a of the fan-shaped projection of the welding area 1411 on the reference plane P is 5°, and the sum a of the central angles of the fan-shaped projections of the plurality of welding areas 1411 on the reference plane P is 10°. m

[0107] Comparative Example 4

[0108] A lithium ion battery was prepared according to the method of Example 1, except that:

[0109] The number of welding areas on the current collecting member 140 is 4, the central angle a of the fan-shaped projection of the welding area 1411 on the reference plane P is 4°, and the sum a of the central angles of the fan-shaped projections of the plurality of welding areas 1411 on the reference plane P is 16°. m

[0110] Comparative Example 5

[0111] A lithium ion battery was prepared according to the method of Example 1, except that:

[0112] ​​The maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X is 0.09 mm, the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 11 mm, the ratio L1 / L2 of the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X to the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 0.08, the central angle a of the sector projection of the welding region 1411 on the reference plane P is 5°, and the sum a of the central angles of the sector projections of the plurality of welding regions 1411 on the reference plane P is 10°. m .

[0113] Comparative Example 6

[0114] A lithium ion battery was prepared according to the method of Example 1, except that:

[0115] The maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X is 1 mm, the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 2 mm, the ratio L1 / L2 of the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X to the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 0.5, the central angle a of the sector projection of the welding region 1411 on the reference plane P is 5°, and the sum a of the central angles of the sector projections of the plurality of welding regions 1411 on the reference plane P is 10°. m .

[0116] Comparative Example 7

[0117] A lithium ion battery was prepared according to the method of Example 1, except that:

[0118] The number of welding regions on the current collecting member 140 is 4, the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X is 0.09 mm, the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 11 mm, the ratio L1 / L2 of the maximum dimension L1 mm of each electrical connection portion 142 in the radial direction X to the interval L2 mm between adjacent two electrical connection portions 142 in the radial direction X is 0.08, the central angle a of the sector projection of the welding region 1411 on the reference plane P is 4°, and the sum a of the central angles of the sector projections of the plurality of welding regions 1411 on the reference plane P is 16°. m .

[0119] Comparative Example 8

[0120] A lithium ion battery was prepared according to the method of Example 1, except that:

[0121] The number of the welding areas on the current collecting member 140 is 4, the maximum size L1 of each electrical connection part 142 in the radial direction X is 1 mm, the interval L2 between two adjacent electrical connection parts 142 in the radial direction X is 2 mm, the ratio L1 / L2 of the maximum size L1 of each electrical connection part 142 in the radial direction X and the interval L2 between two adjacent electrical connection parts 142 in the radial direction X is 0.5, the central angle a of the fan-shaped projection of the welding area 1411 on the reference plane P is 4°, and the sum a of the central angles of the fan-shaped projections of the plurality of welding areas 1411 on the reference plane P is 16°. m

[0122] The batteries prepared in the above examples and comparative examples were subjected to performance tests, and the methods of the specific test items were as follows:

[0123] 1. Test method of impedance performance of lithium ion battery

[0124] At 25°C, the lithium ion battery was charged to the upper limit voltage at a 1C rate, and then discharged to 50% SQC at a 1C rate, and then discharged at a 3C rate for 10 s, and then rested for 30 min, and the direct current internal resistance of the lithium ion battery was calculated.

[0125] 2. Test method of cycle performance of lithium ion battery

[0126] At 25°C, the lithium ion battery prepared was charged to 4.2 V at a 1C rate, and then discharged to 2.8 V at a 1C rate, and then subjected to cycle test, until the capacity of the lithium ion battery was attenuated to 80% of the initial capacity, and the cycle number was recorded.

[0127] The related parameters and test results in the above examples and comparative examples were recorded in Table 1.

[0128]

[0129]

[0130] From the data in Table 1, it can be seen that in Comparative Examples 1 to 8, the lithium ion batteries do not exhibit corresponding performance, which does not meet the requirements.

[0131] ​Therefore, by limiting the ratio of the maximum size L1 mm of each electric connection part 142 in the radial direction X and the spacing L2 mm between adjacent two electric connection parts 142 in the radial direction X to be within the range of 0.01-2, limiting the maximum size L1 mm of each electric connection part 142 in the radial direction X to be within the range of 0.1 mm-1 mm, limiting the spacing L2 mm between adjacent two electric connection parts 142 in the radial direction X to be within the range of 0.5 mm-10 mm, limiting the central angle a of the circular projection of the welding area 1411 on the reference plane P to be not less than 9°, and limiting the sum of the central angles a of the circular projections of the plurality of welding areas 1411 on the reference plane P to be not less than 9°, the structure of the single battery 100 is optimized, the impedance of the single battery 100 is reduced, the overall overcurrent performance of the single battery 100 is improved, and finally the rate performance and cycle performance of the single battery 100 are improved. m In the range of 18°-360°, the structural size of the electric connection part 142 on the current collecting member 140 is reasonably designed to optimize the electron conduction path in the single battery 100, reduce the impedance of the single battery 100, improve the overall overcurrent performance of the single battery 100, and finally improve the rate performance and cycle performance of the single battery 100.

[0132] The above steps provide an introduction to help understand the method, structure and core idea of the present application. For those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also belong to the scope of protection of the present application.

Claims

1. A single cell, characterized by, The single battery comprises: a shell having an axial direction and a radial direction intersecting each other; an electrode assembly arranged in the shell; an end cover arranged at one end of the shell in the axial direction and connected with the shell; a current collecting member, the current collecting member comprising a current collecting body and an electrical connecting portion connecting the current collecting body, the current collecting body being arranged between the electrode assembly and the end cover, and the current collecting body being electrically connected with the electrode assembly through the electrical connecting portion; the current collecting body comprises a welding area, the electrical connecting portion is arranged in the welding area, and the electrical connecting portion is arranged in multiple, the multiple electrical connecting portions being arranged in the radial direction at intervals; in the radial direction, the maximum size of each electrical connecting portion is L1 mm, the interval between adjacent two electrical connecting portions is L2 mm, and the following condition is met: 0.01≤L1 / L2≤2.

2. The unit cell of claim 1, wherein, The maximum size L1 mm of each electrical connecting portion in the radial direction further meets the following condition: 0.1≤L1≤1; and / or, the interval L2 mm between adjacent two electrical connecting portions in the radial direction further meets the following condition: 0.5≤L2≤10.

3. The unit cell according to any one of claims 1 to 2, wherein the shell further has a reference plane perpendicular to the axial direction; the welding area has a fan-shaped projection on the reference plane, and two radii of the welding area extend along the radial direction respectively.

4. The unit cell of claim 3, wherein, The central angle of the fan-shaped projection of the welding area on the reference plane is α, and the following condition is met: 9°≤α.

5. The unit cell of claim 3, wherein, The single battery further has a circumferential direction around the axial direction; the welding area is arranged in multiple, the multiple welding areas being arranged in the circumferential direction at intervals, and the radii of the multiple welding areas intersect at a common vertex, and the multiple welding areas are centrosymmetric about the common vertex.

6. The unit cell of claim 5, wherein, The sum of the central angles of the fan-shaped projections of the plurality of welding areas on the reference plane is α m , satisfying: 18°≤α m ≤360°.

7. The single battery of claim 5, wherein each electrical connecting portion extends along the circumferential direction, and the projection of each electrical connecting portion on the reference plane is in the shape of an arc around the common vertex; and each welding area is arranged with multiple electrical connecting portions arranged in the radial direction at intervals.

8. The unit cell of claim 7, wherein, In the radial direction, in the direction away from the common vertex, the maximum size of the electrical connecting portion in the circumferential direction increases.

9. The cell of claim 1 wherein, The electrode assembly and the current collecting member are welded to form the electrical connecting portion.

10. A battery pack, characterized by, The single battery comprises: a box body; and the single battery of any one of claims 1-9 is arranged in the box body.

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