Single cell and battery pack

Abstract

Embodiments of the present application disclose a single battery and a battery pack. The single battery comprises a shell and an electrode assembly. The electrode assembly comprises a first pole piece, a second pole piece and a separator. The first pole piece, the second pole piece and the separator are wound to form the electrode assembly. The first pole piece comprises a first pole piece main body and a first pole tab. The first pole tab is arranged on one side of the first pole piece main body in a first direction. The size of the first pole tab of the ith coil in the first direction after being flattened is H i mm, and satisfies: H i =H max -(n-i)×(L1+L2+2L3), i≤n. The size of the first pole tab of the Nth coil in the first direction after being flattened is H N mm, and satisfies: H N =H max , N>n. According to the present application, the electronic conduction path in the single battery is optimized, the internal resistance of the single battery is reduced, the temperature change of the single battery during high-rate charging and discharging is reduced, and the fast charging performance and the rate performance of the single battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a single cell battery and a battery pack. Background Technology

[0002] The replacement of traditional fuel vehicles with new energy vehicles is of great significance to improving the energy and pollution problems faced by the global transportation industry, and it is also an inevitable trend. Among them, the power battery, as a key component of new energy vehicles, has attracted much attention. The performance of the power battery directly affects the key indicators of new energy vehicles such as driving range, charging time, and safety performance.

[0003] With the rapid development of the new energy industry, batteries with high capacity, long cycle life, and high rate performance have been widely used and developed. At the same time, the demand for batteries with even larger capacity and greater durability is urgent. As rate performance is one of the core performance characteristics of a battery, improving battery rate performance has become a pressing issue. Utility Model Content

[0004] Embodiments of this application provide a single battery cell and a battery pack to improve the fast charging performance and rate performance of the single battery cell.

[0005] To address the aforementioned technical problems, embodiments of this application disclose the following technical solutions:

[0006] On one hand, a single-cell battery is provided, having a first orientation, including:

[0007] Casing; and

[0008] An electrode assembly is disposed within a housing and includes a first electrode, a second electrode, and a diaphragm. The first electrode and the second electrode have opposite polarities, and the diaphragm is disposed between the first electrode and the second electrode. The first electrode, the second electrode, and the diaphragm are wound together to form the electrode assembly.

[0009] The first electrode includes: a first electrode body and a first electrode tab, wherein the first electrode tab is disposed on one side of the first electrode body in a first direction;

[0010] Among them, the first pole piece of the i-th ring, after being flattened, has a dimension of H in the first direction. i mm, satisfying: H i =H max -(ni)×(L1+L2+2L3);

[0011] n is the number of the first winding turns of the electrode assembly, and n ≥ i, where n and i are integers not less than 1. H maxmm represents the maximum dimension of the first electrode tab in the first direction after being flattened; L1 mm represents the thickness of the first electrode plate; L2 mm represents the thickness of the second electrode plate; and L3 mm represents the thickness of the diaphragm. The dimension of the first electrode tab in the Nth turn after being flattened in the first direction is H. N mm, satisfying: H N =H max ;

[0012] Where N is the number of the second winding turns of the electrode assembly, and N > n.

[0013] In addition to one or more of the features disclosed above, or alternatively, the first number of turns n and the second number of turns N of the electrode assembly also satisfy: 0.1≤n / N≤0.9, 20≤N≤80.

[0014] In addition to one or more of the features disclosed above, or alternatively, the first number of turns n of the electrode assembly also satisfies: 2≤n≤72.

[0015] In addition to one or more of the features disclosed above, or alternatively, the first tab, when flattened, has a maximum dimension H in the first direction. max mm also satisfies: 2≤H max ≤10.

[0016] In addition to one or more of the features disclosed above, or as an alternative, the second electrode includes: a second electrode body and a second electrode tab, the second electrode tab being disposed on one side of the second electrode body in the first direction;

[0017] Among them, the second pole piece of the i-th ring, after being flattened, has a dimension of T in the first direction. i mm, satisfying: T i =T max -(ni)×(L1+L2+2L3);

[0018] Among them, T max mm is the maximum dimension of the second electrode in the first direction after it is flattened.

[0019] In addition to one or more of the features disclosed above, or alternatively, the second pole piece of the Nth turn, after being flattened, has a dimension of T in the first direction. N mm, satisfying: T N =T max ;

[0020] Where N is the number of the second winding turns of the electrode assembly, and N > n.

[0021] In addition to one or more of the features disclosed above, or alternatively, the second electrode tab, when flattened, has a maximum dimension T in the first direction.max mm also satisfies: 2≤T max ≤10.

[0022] In addition to one or more of the features disclosed above, or alternatively, the single cell also has a second direction intersecting the first direction;

[0023] When the electrode assembly is flattened, the first electrode extends along the second direction;

[0024] Multiple first electrodes are provided, and the multiple first electrodes are distributed at intervals in the second direction;

[0025] In the second direction, the distance between two adjacent first pole pieces is W1 mm, satisfying: 0 < W1 ≤ 1; and / or,

[0026] The maximum dimension of the first electrode in the second direction is W2 mm, which satisfies: 2≤W2≤10.

[0027] In addition to one or more of the features disclosed above, or alternatively, the single cell also has a second direction intersecting the first direction;

[0028] When the electrode assembly is flattened, the second electrode extends along the second direction;

[0029] Multiple second electrodes are provided, and the multiple second electrodes are distributed at intervals in the second direction;

[0030] In the second direction, the distance between two adjacent second pole pieces is W3 mm, satisfying: 0 < W3 ≤ 1; and / or,

[0031] The maximum dimension of the second electrode in the second direction is W4 mm, which satisfies: 2≤W4≤10.

[0032] On the other hand, a battery pack is further disclosed, which, in addition to one or more of the features disclosed above, or alternatively, includes a housing; and individual cells as described in any of the preceding claims, the individual cells being disposed within the housing.

[0033] One of the above technical solutions has the following advantages or beneficial effects: This application defines the dimension H of the first electrode tab of the i-th ring in the first direction after it is flattened. i mm satisfies: H i =H max -(ni)×(L1+L2+2L3), i≤n; and the first pole piece of the Nth ring is limited to having a dimension of H in the first direction after being flattened. N mm satisfies: H N =H maxN > n, so as to optimize the structural dimensions of the first tab, so that the size of the first tab on the inner side of the wound electrode assembly is shortened in the first direction. This ensures that after the first tabs at different positions on the wound electrode assembly are cut, stacked and flattened, a region with a consistent stacking height of the first tabs 1212 is formed in the inner layer position on the plane perpendicular to the first direction Z. This increases the effective welding area of ​​the first tab, thereby optimizing the electronic conduction path in the single cell, reducing the polarization phenomenon of the first electrode sheet on the inner side of the wound electrode assembly, thereby reducing the internal resistance of the single cell and the temperature change of the single cell during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell. Attached Figure Description

[0034] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0035] Figure 1 This is a three-dimensional structural view of a single battery cell provided according to an embodiment of this application;

[0036] Figure 2 This is a schematic diagram of the structure of the electrode assembly provided according to the embodiments of this application;

[0037] Figure 3 This is a schematic diagram of the first electrode sheet in an unfolded state according to an embodiment of this application;

[0038] Figure 4 This is a schematic diagram of the second pole piece in its unfolded state according to an embodiment of this application;

[0039] Figure 5 This is a diagram showing the relationship between the stacking height of the tabs and the number of winding turns according to an embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 100. Single cell; 110. Casing; 120. Electrode assembly; 121. First electrode; 1211. First electrode body; 1212. First tab; 122. Second electrode; 1221. Second electrode body; 1222. Second tab; 123. Separator; 130. End cap. Detailed Implementation

[0042] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0043] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0045] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] To ensure the overcurrent function of secondary batteries, existing secondary batteries flatten the positive and negative tabs after the electrode assembly is wound. After the tabs are cut, stacked, and flattened, they need to be connected to the current collector as a whole through laser welding or other methods to achieve electrical conduction. The tabs in existing secondary batteries are all of equal height and spacing. To prevent the inner ring tabs from folding after flattening, tab-free areas are usually reserved on both the inner and outer rings of the electrode assembly. This results in fewer tab layers on the inner and outer rings, leading to a lower tab stacking height than the middle ring. This unevenness reduces the welding area between the tab stacking surface and the current collector, affecting the internal resistance and temperature rise during high-rate charging and discharging, thus impacting the rate performance of the secondary battery.

[0047] To address the aforementioned problems, this application provides a single-cell battery 100 in its embodiments, which has a first direction Z and a second direction X intersecting in pairs. Exemplarily, the single-cell battery 100 has a first direction Z and a second direction X that are mutually perpendicular in pairs. It should be noted that the introduction of the first direction Z and the second direction X in the embodiments of this application is merely for the convenience of describing spatial relationships and should not be construed as limiting the scope of the embodiments of this application. Therefore, the mutually perpendicular relationship between the first direction Z and the second direction X can be interpreted, depending on the actual technical scenario, as the first direction Z and the second direction X representing three mutually perpendicular directions in three-dimensional space, or reasonably interpreted as a nearly perpendicular relationship between the first direction Z and the second direction X, for example, the included angle between the first direction Z and the second direction X being within the range of 85°-95°… Any technical solution that conforms to the spirit of this application or achieves the technical effects described in this application can be considered to fall within the scope defined by the appended claims.

[0048] Specifically, refer to Figures 1 to 2 The single cell 100 includes: a housing 110, an electrode assembly 120, and an end cap 130.

[0049] Specifically, the electrode assembly 120 is disposed within the housing 110, and the electrode assembly 120 includes: a first electrode 121, a second electrode 122, and a diaphragm 123. The first electrode 121 and the second electrode 122 have opposite polarities. The diaphragm 123 is disposed between the first electrode 121 and the second electrode 122 to separate the first electrode 121 and the second electrode 122. The first electrode 121, the second electrode 122, and the diaphragm 123 are wound together to form the electrode assembly 120. The end cap 130 is connected to one end of the housing 110 to seal the housing 110.

[0050] The single cell 100 can be a rechargeable battery, which refers to a single cell that can be recharged after discharge to activate the active materials and continue to be used. For example, the single cell 100 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery, but is not limited to these.

[0051] The single cell 100 can be a prismatic cell, a pouch cell, or a cell of other shapes. For example, in this application, the single cell 100 is a cylindrical cell.

[0052] The end cap 130 can be integrally formed with the housing 110, meaning the end cap 130 can be the outer wall of the housing 110. The end cap 130 can also be fixedly connected to the housing 110, for example, by welding or other processes, to one end of the housing 110 in the Z-axis direction. This application does not impose specific limitations and can be configured according to actual circumstances. For example, in this application, the end cap 130 and the housing 110 are separately disposed, and the end cap 130 and the housing 110 are fixedly welded together.

[0053] The first electrode 121 can be a positive electrode or a negative electrode. This application does not make specific limitations and can be set according to the actual situation.

[0054] The single-cell battery 100 also includes an electrolyte, terminals, and other functional components. The electrolyte can be a conventional electrolyte or a special electrolyte with additives. The electrolyte is used to wet the electrode assembly 120. The electrode assembly 120 is the component in the single-cell battery 100 where electrochemical reactions occur, and there can be one or more electrode assemblies. The portions of the first electrode 121 and the second electrode 122 containing active material constitute the main body of the electrode assembly 120. The portion of the first electrode 121 without active material constitutes the first tab 1212, and the portion of the second electrode 122 without active material constitutes the second tab 1222. During the charging and discharging process of the single-cell battery 100, the positive and negative active materials react with the electrolyte. The first tab 1212 and the second tab 1222 are electrically connected to the terminals and the casing 110, respectively, to form a current circuit, enabling the single-cell battery 100 to function normally.

[0055] Specifically, the first electrode 121 includes: a first electrode body 1211 and a first electrode tab 1212, wherein the first electrode tab 1212 is disposed on one side of the first electrode body 1211 in the first direction Z.

[0056] The first electrode 1212 can be a positive electrode or a negative electrode. This application does not make specific limitations and the choice can be made according to the actual situation.

[0057] For example, in this application, the first electrode 121 is a positive electrode and the first tab 1212 is a positive tab.

[0058] The first tab 1212 can be integrally formed with the first electrode body 1211, meaning the first electrode body 1211 and the first tab 1212 are a single, integrated structure. For example, the portion of the first electrode body 1211 without the active material layer can be cut to form the first tab 1212. The first tab 1212 can also be fixedly connected to the first electrode body 1211. For example, the first tab 1212 is welded to the first electrode body 1211. This application does not impose specific limitations and can be configured according to actual circumstances. For example, in this application, the first tab 1212 and the first electrode body 1211 are integrally formed.

[0059] Specifically, refer to Figures 2 to 3 The first pole piece 1212 of the i-th ring, after being flattened, has a dimension H in the first direction Z. i mm, satisfying: H i =H max -(ni)×(L1+L2+2L3); n is the number of the first winding turns of the electrode assembly 120, and n≥i, where n and i are integers not less than 1, H max mm is the maximum dimension of the first electrode tab 1212 in the first direction Z after it is flattened, L1 mm is the thickness of the first electrode 121, L2 mm is the thickness of the second electrode 122, and L3 mm is the thickness of the diaphragm 123.

[0060] Among them, the first pole lug 1212 of the i-th ring, after being flattened, has a dimension H in the first direction Z. i mm can be obtained by disassembling the actual single cell 100, unwinding the first electrode 121 from a wound state to a flat state, and then measuring the dimension of the first electrode tab 1212 located at the i-th turn in the first direction Z multiple times using a measuring tool and calculating the average value. The measuring tool can be any one of a ruler, vernier caliper, or other dimensional measuring instruments, but is not limited to this.

[0061] The first number of turns n of the electrode assembly 120 can be obtained by directly observing the wound electrode assembly 120 after disassembling the actual single cell 100.

[0062] The first tab 1212, after being flattened, has its maximum dimension H in the first direction Z. maxThe actual single cell 100 can be disassembled, and the first electrode 121 can be unwound from a wound state to a flat state. Then, the dimensions of the first electrode tab 1212 on the side of the first electrode 121 away from the winding center can be measured multiple times using a measuring tool in the first direction Z, and the average value can be calculated. The measuring tool can be any one of a ruler, vernier caliper, or other dimensional measuring instruments, but is not limited to this.

[0063] The thickness L1 mm of the first electrode 121 can be obtained by disassembling the actual single cell 100, first flattening the first electrode 121 to its unfolded state, and then using a measuring tool to measure the thickness of the active material layer of the first electrode 121 at different locations multiple times and calculating the average value. The measuring tool can be any one of a thickness gauge or a micrometer.

[0064] The thickness L2 mm of the second electrode 122 can be obtained by disassembling the actual single cell 100, first flattening the second electrode 122 to its unfolded state, then using a measuring tool to measure the thickness of the active material layer of the second electrode 122 at different locations multiple times and calculating the average value. The measuring tool can be any one of a thickness gauge or a micrometer.

[0065] The thickness L2 mm of the separator 123 can be obtained by disassembling the actual single cell 100, first flattening the separator 123 to its unfolded state, then using a measuring tool to measure the thickness of the separator 123 at different positions multiple times and calculating the average value. The measuring tool can be any one of a thickness gauge or a micrometer.

[0066] Understandably, this application defines the dimension H of the first pole piece 1212 of the i-th ring in the first direction Z after it is flattened. i mm satisfies: H i =H max -(ni)×(L1+L2+2L3) is used to optimize the structural dimensions of the first tab 1212, so that the dimension of the first tab 1212 on the inner side of the wound electrode assembly 120 in the first direction Z is shortened. This ensures that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening, and increases the effective welding area of ​​the first tab 1212. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0067] In one embodiment, reference is made to Figure 2 , Figure 3 and Figure 5The first pole piece 1212 of the Nth ring, after being flattened, has a dimension of H in the first direction Z. N mm, satisfying: H N =H max N is the number of the second winding turns of the electrode assembly 120, and N > n. That is, after the nth turn, in the (n+1), (n+2), (n+3), ..., (N)th turns, the first electrode tab 1212 of each turn maintains the same dimension in the first direction Z after being flattened, i.e., H n+1 =H n+2 =H n+3 =……=H N =H max To further optimize the structural dimensions of the first tab 1212, after the first tabs 1212 at different positions on the wound electrode assembly 120 are cut, stacked and flattened, a region with a consistent stacking height of the first tabs 1212 is formed in the inner layer position on the plane perpendicular to the first direction Z, thereby increasing the effective welding area of ​​the first tab 1212, thus optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0068] Among them, the first pole lug 1212 of the Nth ring, after being flattened, has a dimension H in the first direction Z. N The actual single cell 100 can be disassembled, and the first electrode 121 can be unwound from a wound state to a flat state. Then, the dimensions of the first electrode tab 1212 on the side of the first electrode 121 away from the winding center can be measured multiple times using a measuring tool in the first direction Z, and the average value can be calculated. The measuring tool can be any one of a ruler, vernier caliper, or other dimensional measuring instruments, but is not limited to this.

[0069] The second number of turns N of the electrode assembly 120 can be obtained by directly observing the wound electrode assembly 120 after the actual single cell 100 is disassembled.

[0070] In one embodiment, the first number of turns n and the second number of turns N of the electrode assembly 120 further satisfy: 0.1 ≤ n / N ≤ 0.9. That is, the ratio of the first number of turns n and the second number of turns N of the electrode assembly 120 can be controlled within the range of 0.1 to 0.9. For example, the ratio of the first number of turns n and the second number of turns N of the electrode assembly 120 can be one of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, or any combination of two of them. The specific values ​​of n / N given above are merely illustrative, and any value within the range of 0.1 to 0.9 is within the scope of protection of this application.

[0071] This application limits the ratio of the first winding number n of the electrode assembly 120 to the second winding number N of the electrode assembly 120 to within the range of 0.1 to 0.9, so as to ensure that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after cutting and flattening, thereby increasing the effective welding area of ​​the first tabs 1212, thus optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode sheet 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0072] In one embodiment, the first number of turns n of the electrode assembly 120 further satisfies: 2 ≤ n ≤ 72. That is, the first number of turns n of the electrode assembly 120 can be controlled within the range of 2 to 72 turns. For example, the first number of turns n of the electrode assembly 120 can be one or a combination of any two of the following: 2 turns, 10 turns, 20 turns, 30 turns, 40 turns, 50 turns, 60 turns, 70 turns, or 72 turns. The specific values ​​of the first number of turns n are given above as examples only, and any value within the range of 2 to 72 turns is within the protection scope of this application.

[0073] This application limits the number of first winding turns n of the electrode assembly 120 to within the range of 2 to 72 turns, so as to ensure that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after being cut, stacked and flattened, thereby increasing the effective welding area of ​​the first tabs 1212, thereby optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode sheet 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0074] The second winding number N of the electrode assembly 120 also satisfies: 20 ≤ N ≤ 80. That is, the second winding number N of the electrode assembly 120 can be controlled within the range of 20 to 80 turns. For example, the second winding number N of the electrode assembly 120 can be one of 20, 30, 40, 50, 60, 70, or 80 turns, or any combination thereof. The specific values ​​of the second winding number N given above are only illustrative examples, and any value within the range of 20 to 80 turns is within the protection scope of this application.

[0075] This application limits the number of second winding turns N of the electrode assembly 120 to within the range of 20 to 80 turns to ensure that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after being cut, stacked and flattened, thereby increasing the effective welding area of ​​the first tabs 1212, thus optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode sheet 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0076] In one embodiment, reference is made to Figure 3 The first electrode 1212, after being flattened, has a maximum dimension H in the first direction Z. max mm also satisfies: 2≤H max ≤10. That is, the maximum dimension H of the first tab 1212 in the first direction Z after it is flattened. max The diameter (mm) can be controlled within the range of 2mm to 10mm. For example, the maximum dimension H of the first tab 1212 in the first direction Z after being flattened is... max mm can be a range of one or more of 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm, or any combination thereof. H max The specific values ​​for mm mentioned above are merely illustrative examples, and any value within the range of 2mm to 10mm is within the scope of protection of this application.

[0077] This application defines the maximum dimension H of the first tab 1212 in the first direction Z after it is flattened. maxThe thickness is within the range of 2mm to 10mm to further optimize the structural dimensions of the first tab 1212, ensuring that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening, increasing the effective welding area of ​​the first tab 1212, thereby optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0078] In one embodiment, reference is made to Figure 2 and Figure 4 The second electrode 122 includes a second electrode body 1221 and a second electrode tab 1222, wherein the second electrode tab 1222 is disposed on one side of the second electrode body 1221 in the first direction Z.

[0079] Specifically, the second pole piece 1222 of the i-th ring, after being flattened, has a dimension of T in the first direction Z. i mm, satisfying: T i =T max -(ni)×(L1+L2+2L3); T max mm is the maximum dimension of the second tab 1222 in the first direction Z after it is flattened.

[0080] Among them, the second pole lug 1222 of the i-th ring, after being flattened, has a dimension T in the first direction Z. i The actual single cell 100 can be disassembled, and the second electrode 122 can be unwound from a wound state to a flat state. Then, the dimensions of the second electrode tab 1222 located at the i-th turn in the first direction Z can be measured multiple times using a measuring tool, and the average value can be calculated. The measuring tool can be any one of a ruler, vernier caliper, or other dimensional measuring instruments, but is not limited to this.

[0081] The second electrode 1222, after being flattened, has its maximum dimension T in the first direction Z. max The actual single cell 100 can be disassembled, and the second electrode 122 can be unwound from a wound state to a flat state. Then, the dimensions of the first electrode 1212 located on the side away from the winding center on the second electrode 1222 in the first direction Z can be measured multiple times using a measuring tool, and the average value can be calculated. The measuring tool can be any one of a ruler, vernier caliper, or other dimensional measuring instruments, but is not limited to this.

[0082] This application defines the dimension T of the second pole piece 1222 of the i-th ring in the first direction Z after it is flattened. i mm, satisfying: T i =Tmax -(ni)×(L1+L2+2L3) is used to optimize the structural dimensions of the second tab 1222, thereby shortening the dimension of the second tab 1222 on the inner side of the wound electrode assembly 120 in the first direction Z. This ensures that the stacking height of the second tabs 1222 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening, increasing the effective welding area of ​​the second tab 1222. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0083] In one embodiment, reference is made to Figure 2 and Figure 4 The second pole piece 1222 of the Nth ring, after being flattened, has a dimension of T in the first direction Z. N mm, satisfying: T N =T max N is the second number of turns of the electrode assembly 120, and N > n. After the nth turn, the second tab 1222 maintains the same size in the first direction Z after being flattened, so as to further optimize the structural size design of the second tab 1222, so as to ensure that the stacking height of the second tabs 1222 at different positions on the wound electrode assembly 120 is consistent after being cut, stacked and flattened, increasing the effective welding area of ​​the second tab 1222, thereby optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0084] In one embodiment, reference is made to Figure 2 and Figure 4 The second electrode 1222, after being flattened, has a maximum dimension T in the first direction Z. max mm also satisfies: 2≤T max ≤10. That is, the maximum dimension T of the second electrode 1222 in the first direction Z after being flattened. max The diameter (mm) can be controlled within the range of 2mm to 10mm. For example, the maximum dimension T of the second electrode tab 1222 in the first direction Z after being flattened is... max mm can be a range of one or more of 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm, or any combination of two of them. T max The specific values ​​for mm mentioned above are merely illustrative examples, and any value within the range of 2mm to 10mm is within the scope of protection of this application.

[0085] This application defines the maximum dimension T of the second tab 1222 in the first direction Z after it is flattened. max Within a mm range, the structural dimensions of the second tab 1222 are further optimized to ensure that the stacking height of the second tabs 1222 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening. This increases the effective welding area of ​​the second tab 1222, thereby optimizing the electronic conduction path in the single cell 100, reducing the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0086] In one embodiment, reference is made to Figure 3 When the electrode assembly 120 is flattened, the first electrode 121 extends along the second direction X; multiple first electrode tabs 1212 are provided, and the multiple first electrode tabs 1212 are distributed at intervals in the second direction X.

[0087] Specifically, in the second direction X, the distance between two adjacent first electrodes 1212 is W1 mm, satisfying: 0 < W1 ≤ 1. That is, the distance W1 mm ​​between two adjacent first electrodes 1212 can be controlled within the range of 0 to 1 mm (excluding the endpoint value 0). For example, the distance W1 mm ​​between two adjacent first electrodes 1212 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 any combination of two of them. The specific values ​​of W1 mm ​​mentioned above are only given as examples, and any value within the range of 0 to 1 mm (excluding the endpoint value 0) is within the protection scope of this application.

[0088] This application optimizes the structural dimensions of the first tabs 1212 by limiting the distance W1 mm ​​between two adjacent first tabs 1212 to within the range of 0 to 1 mm (excluding the endpoint value 0). This ensures that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after cutting and flattening, increasing the effective welding area of ​​the first tabs 1212. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0089] The maximum dimension of the first electrode 1212 in the second direction X is W2 mm, satisfying: 2 ≤ W2 ≤ 10. That is, the maximum dimension W2 mm of the first electrode 1212 in the second direction X can be controlled within the range of 2 mm to 10 mm. For example, the maximum dimension W2 mm of the first electrode 1212 in the second direction X can be one of 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm, or any combination thereof. The specific value of W2 mm given above is only illustrative, and any value within the range of 2 mm to 10 mm is within the protection scope of this application.

[0090] This application further optimizes the structural dimensions of the first tab 1212 by limiting its maximum size W2 mm in the second direction X to within the range of 2 mm to 10 mm. This ensures that the stacking height of the first tabs 1212 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening, thereby increasing the effective welding area of ​​the first tab 1212. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0091] In one embodiment, the first electrode 1212 has a first axis, and the angle between the first axis of the first electrode 1212 and the second direction X is α1, satisfying: 0 < α1 ≤ 90°. That is, the angle α1 between the first axis of the first electrode 1212 and the second direction X can be controlled within the range of 0 to 90° (excluding the endpoint value 0).

[0092] The determination of the first axis of the first electrode tab 1212 can be achieved by first unfolding the first electrode plate 121 and the first electrode tab 1212, flattening the unfolded first electrode plate 121 into a straight state, and then determining the central axis set along the extension direction of the first electrode tab 1212 as the first axis of the first electrode tab 1212.

[0093] The angle α1 between the first axis of the first tab 1212 and the second direction X can be obtained by first disassembling the single cell 100, unfolding the first electrode 121, flattening the unfolded first electrode 121 into a straight state, and then repeatedly measuring the angle between the first axis of the first tab 1212 on the first electrode 121 and the second direction X using a measuring tool and calculating the average value. The measuring tool can be an angle measuring instrument.

[0094] In one embodiment, reference is made to Figure 4When the electrode assembly 120 is flattened, the second electrode 122 extends along the second direction X; multiple second electrode tabs 1222 are provided, and the multiple second electrode tabs 1222 are distributed at intervals in the second direction X.

[0095] Specifically, in the second direction X, the distance between two adjacent second electrodes 1222 is W3 mm, satisfying: 0 < W3 ≤ 1. That is, the distance W3 mm between two adjacent second electrodes 1222 can be controlled within the range of 0 to 1 mm (excluding the endpoint value 0). For example, the distance W3 mm between two adjacent second electrodes 1222 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 any combination of two of them. The specific value of W3 mm mentioned above is only given as an example, and any value within the range of 0 to 1 mm (excluding the endpoint value 0) is within the protection scope of this application.

[0096] This application optimizes the structural dimensions of the second tabs 1222 by limiting the spacing W3 mm between two adjacent second tabs 1222 to within the range of 0 to 1 mm (excluding the endpoint value 0). This ensures that the stacking height of the second tabs 1222 at different positions on the wound electrode assembly 120 is consistent after cutting, stacking and flattening, thereby increasing the effective welding area of ​​the second tabs 1222. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, and improving the fast charging performance and rate performance of the single cell 100.

[0097] The maximum dimension of the second electrode 1222 in the second direction X is W4 mm, satisfying: 2 ≤ W4 ≤ 10. That is, the maximum dimension W4 mm of the second electrode 1222 in the second direction X can be controlled within the range of 2 mm to 10 mm. For example, the maximum dimension W4 mm of the second electrode 1222 in the second direction X can be one of 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm, or any combination thereof. The specific value of W4 mm given above is merely illustrative; any value within the range of 2 mm to 10 mm is within the protection scope of this application.

[0098] This application further optimizes the structural dimensions of the second tab 1222 by limiting its maximum size W4 mm in the second direction X to within the range of 2 mm to 10 mm. This ensures that the stacking height of the second tabs 1222 at different positions on the wound electrode assembly 120 is consistent after cutting and flattening, thereby increasing the effective welding area of ​​the second tab 1222. This optimizes the electronic conduction path in the single cell 100, reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120, thereby reducing the internal resistance of the single cell 100 and the temperature change during high-rate charging and discharging of the single cell 100, and improving the fast charging performance and rate performance of the single cell 100.

[0099] In one embodiment, the second electrode 1222 has a second axis, and the angle between the second axis of the second electrode 1222 and the second direction X is α2, satisfying: 0 < α2 ≤ 90°. That is, the angle α2 between the second axis of the second electrode 1222 and the second direction X can be controlled within the range of 0 to 90° (excluding the endpoint value 0).

[0100] The method for measuring the angle α2 between the second axis of the second electrode 1222 and the second direction X is the same as the method for measuring the angle α1 between the first axis of the first electrode 1212 and the second direction X, and will not be elaborated here. Please refer to the above description.

[0101] In another embodiment, this application also provides a battery pack, including: a housing, a single battery 100 as in any of the above embodiments, and a housing cover, wherein the single battery 100 is disposed in the housing, the housing cover is connected to the housing, and the housing cover seals the housing.

[0102] The battery pack can be a three-tiered system consisting of individual cells 100, battery modules, and a battery pack. This means the individual cells 100 are first grouped into battery modules, and then the battery modules are placed inside a housing to form the battery pack. Alternatively, it can be a two-tiered system consisting of individual cells 100 and a battery pack, where the individual cells 100 are directly housed inside a housing to form the battery pack. No specific limitations are imposed in this application; the design can be tailored to the specific circumstances, as long as it does not affect the effectiveness of this application.

[0103] To better understand the technical solution of this application, the following explanation uses a lithium-ion battery as an example.

[0104] This test example provides a method for preparing a lithium-ion battery, the specific process of which is as follows:

[0105] 1. Preparation of positive electrode sheet

[0106] The positive electrode active material, conductive agent, and binder are mixed according to the mass ratio, and then a solvent is added for further mixing. The mixture is stirred under vacuum until the system becomes homogeneous, thus obtaining a positive electrode slurry. The positive electrode slurry is then uniformly coated on both sides of the positive electrode current collector, and then transferred to an oven for drying. After rolling, slitting, and cutting, the positive electrode sheet is obtained.

[0107] 2. Preparation of negative electrode sheet

[0108] The negative electrode active material, conductive agent, thickener, and binder are mixed according to the mass ratio, and then a solvent is added for mixing. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both sides of the negative electrode current collector, and then transferred to an oven for drying. After that, the negative electrode sheet is obtained by rolling, slitting, and cutting.

[0109] 3. Preparation of electrolyte

[0110] An organic solvent is obtained by mixing multiple solvents in a certain mass ratio, and then an electrolyte is added and mixed evenly to prepare an electrolyte solution.

[0111] 4. Preparation of the diaphragm

[0112] PP film is used as the separator.

[0113] 5. Preparation of lithium-ion batteries

[0114] After drying, the negative and positive electrode sheets prepared by the above steps are used together with the separator to prepare a wound electrode assembly using a winding machine. The different posts on the end caps of the positive and negative electrode tabs are directly welded together, and the welded electrode assembly with the top cap is placed into an aluminum shell for encapsulation. After filling with electrolyte and forming and fixing the volume, a lithium-ion battery is obtained.

[0115] The lithium-ion single cell batteries 100 in each test example were all prepared according to the above-mentioned preparation method. The structural dimensions and performance test data of each test example are shown in Table 1 and Table 2.

[0116] The lithium-ion single cell 100 prepared in the above test example was subjected to performance testing. The specific test methods are as follows:

[0117] The single-cell battery 100 test system used for performance testing must support constant current charging and discharging, constant voltage charging and data recording. The system has a constant temperature chamber to control the ambient temperature at 25±1℃. Multimeters (calibrated voltage / current), data cables, insulating clamps, micrometers, vernier calipers, etc. are used to measure various data.

[0118] Before measurement, the lithium-ion single cell 100 needs to be pretreated. The steps include:

[0119] 1) Initial activation: Perform 1-2 complete charge-discharge cycles at a low charge-discharge rate (e.g., 0.2C) to bring the lithium-ion single cell to a stable state.

[0120] 2) Let it stand for 10-30 minutes after each charge and discharge cycle to ensure that polarization is eliminated.

[0121] When performing a charge / discharge rate test, you should first select a suitable charge / discharge rate. Common rate ranges include 0.2C, 0.5C, 1C, 2C, 3C, and 4C (adjusted according to the design of a single battery cell). Pay attention to the symmetry of charge and discharge. You can test the charge and discharge conditions at the same rate, or fix the charging rate (e.g., 0.5C) and change the discharge rate.

[0122] The testing procedure for lithium-ion single-cell batteries 100 includes:

[0123] 1) During the charging phase, constant current charging is performed first, followed by constant voltage charging: first, constant current charging is performed at the standard rate (e.g., 0.5C) until the cutoff voltage (e.g., 4.2V), then the constant voltage mode is switched and the charging stops when the current drops to the cutoff current (e.g., 0.05C).

[0124] 2) Set a preset time for standing, for example, 10 minutes.

[0125] 3) Discharge stage: The discharge stage is carried out in the form of constant current discharge, such as constant current discharge at the target rate (e.g., 1C) until the cutoff voltage (e.g., 2.5V or 3.0V, depending on the material).

[0126] 4) Let it stand for the preset time again, for example, 10 minutes.

[0127] 5) Repeat the test: Change to different expansion ratios (e.g., 0.2C→0.5C→1C→2C→3C→4C), and repeat each expansion ratio 2-3 times.

[0128] Finally, data were recorded and analyzed for key parameters such as discharge capacity, charging capacity, and surface temperature of individual cells. The ratio of discharge capacity at each rate to rated capacity (capacity obtained by testing at 0.2C charge and discharge) was determined, and the capacity retention rate was calculated (capacity retention rate = discharge capacity at different rates / rated capacity * 100%).

[0129] Table 1. Parameters and test results for the test control group and the test examples.

[0130]

[0131]

[0132]

[0133] As can be seen from the data in the table above, the single cell 100 provided in each embodiment of this application benefits from the fact that the size of the first electrode tab 1212 on the inner side of the wound electrode assembly 120 in the first direction Z is such that the size Hi mm of the first electrode tab 1212 in the first direction Z after being flattened in the i-th turn (i < n) satisfies Hi = Hmax - (ni) × (L1 + L2 + 2L3), and the size of the first electrode tab 1212 in the first direction Z after being flattened in the N-th turn (N > n) is H. N mm, satisfying H N =H max The shortening of the rule allows the first tabs 1212 at different positions on the wound electrode assembly 120 to form a region with a consistent stacking height on the inner layer position of the plane perpendicular to the first direction Z after the cutting and flattening process. This increases the effective welding area of ​​the first tabs 1212, thereby optimizing the electronic conduction path in the single cell 100. Compared with the traditional design, it reduces the polarization phenomenon of the first electrode 121 on the inner side of the wound electrode assembly 120. The measurement results show that, under different charging efficiencies, it can effectively reduce the internal resistance of the single cell 100 and the temperature change of the single cell 100 during high-rate charging and discharging, thereby improving the fast charging performance and rate performance of the single cell 100.

[0134] The above steps are provided only to help understand the method, structure, and core ideas of this application. Those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A single-cell battery having a first orientation, characterized in that, include: case; as well as An electrode assembly is disposed within the housing, and the electrode assembly includes: a first electrode, a second electrode, and a diaphragm, wherein the first electrode and the second electrode have opposite polarities, and the diaphragm is disposed between the first electrode and the second electrode, and the first electrode, the second electrode, and the diaphragm are wound together to form the electrode assembly; The first electrode includes: a first electrode body and a first electrode tab, wherein the first electrode tab is disposed on one side of the first electrode body in the first direction; Wherein, the first electrode tab of the i-th ring, after being flattened, has a dimension H in the first direction. i mm, satisfying: H i =H max -(ni)×(L1+L2+2L3); n is the number of the first winding turns of the electrode assembly, and n ≥ i, where n and i are integers not less than 1. max mm is the maximum dimension of the first electrode tab in the first direction after it is flattened, L1 mm is the thickness of the first electrode sheet, L2 mm is the thickness of the second electrode sheet, and L3 mm is the thickness of the diaphragm. The first tab of the Nth ring, after being flattened, has a dimension H in the first direction. N mm, satisfying: H N =H max ; Wherein, N is the second number of turns of the electrode assembly, and N > n.

2. The single-cell battery as described in claim 1, characterized in that, The first number of turns n and the second number of turns N of the electrode assembly also satisfy: 0.1≤n / N≤0.9, 20≤N≤80.

3. The single-cell battery as described in claim 2, characterized in that, The first number of turns n of the electrode assembly also satisfies: 2≤n≤72.

4. The single-cell battery according to any one of claims 1 to 3, characterized in that, The first tab, after being flattened, has a maximum dimension H in the first direction. max mm also satisfies: 2≤H max ≤10.

5. The single-cell battery as described in claim 1, characterized in that, The second electrode includes: a second electrode body and a second electrode tab, wherein the second electrode tab is disposed on one side of the second electrode body in the first direction; Wherein, the second electrode tab of the i-th ring, after being flattened, has a dimension T in the first direction. i mm, satisfying: T i =T max -(ni)×(L1+L2+2L3); Among them, T max mm is the maximum dimension of the second electrode tab in the first direction after it is flattened.

6. The single-cell battery as described in claim 5, characterized in that, The second electrode tab of the Nth ring, after being flattened, has a dimension T in the first direction. N mm, satisfying: T N =T max ; Wherein, N is the second number of turns of the electrode assembly, and N > n.

7. The single-cell battery as described in claim 6, characterized in that, The second electrode tab, after being flattened, has a maximum dimension T in the first direction. max mm also satisfies: 2≤T max ≤10.

8. The single-cell battery as described in claim 1, characterized in that, The single cell also has a second direction intersecting the first direction; When the electrode assembly is flattened, the first electrode extends along the second direction; Multiple first electrodes are provided, and the multiple first electrodes are distributed at intervals in the second direction; In the second direction, the distance between two adjacent first electrodes is W1 mm, satisfying: 0 < W1 ≤ 1; and / or, The maximum dimension of the first electrode in the second direction is W2 mm, which satisfies: 2≤W2≤10.

9. The single-cell battery as described in claim 5, characterized in that, The single cell also has a second direction intersecting the first direction; When the electrode assembly is flattened, the second electrode extends along the second direction; Multiple second electrodes are provided, and the multiple second electrodes are distributed at intervals in the second direction; In the second direction, the distance between two adjacent second pole pieces is W3 mm, satisfying: 0 < W3 ≤ 1; and / or, The maximum dimension of the second electrode tab in the second direction is W4 mm, which satisfies: 2≤W4≤10.

10. A battery pack, characterized in that, include: Box; as well as The single-cell battery as described in any one of claims 1 to 9, wherein the single-cell battery is disposed within the housing.

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