Battery core assembly and battery

Abstract

The application relates to the technical field of batteries, and particularly provides a winding core assembly of a battery and the battery. The winding core assembly of the application is formed by winding a negative electrode, a first diaphragm, a positive electrode and a second diaphragm in sequence, the negative electrode comprises a first negative electrode material layer, a second negative electrode material layer and a negative electrode current collector, the positive electrode comprises a first positive electrode material layer, a second positive electrode material layer and a positive electrode current collector, the ratio of the effective capacity per unit area of the second negative electrode material layer to the effective capacity per unit area of the first positive electrode material layer decreases along the direction away from the center hole of the winding core assembly, and / or the ratio of the effective capacity per unit area of the first negative electrode material layer to the effective capacity per unit area of the second positive electrode material layer increases along the direction away from the center hole of the winding core assembly. Through the arrangement, the design allowance of the NP ratio can be reduced, so that the waste of the negative electrode active material can be avoided or reduced, and the energy density of the winding core can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically providing a battery core assembly and a battery. Background Technology

[0002] In recent years, with the rapid development of power, energy storage, smart wearables and other fields, increasingly higher requirements have been put forward for battery energy storage technology.

[0003] Taking lithium-ion batteries as an example, lithium-ion batteries have become the primary choice in the battery field due to their high energy density and relatively mature manufacturing technology.

[0004] Lithium-ion batteries typically consist of the following components: positive and negative electrodes that allow lithium ions to intercalate and deintercalate; a separator that provides electronic insulation and ion transport; an electrolyte that conducts lithium ions; and accessories such as current collectors, tabs, and a casing. Common lithium-ion batteries exist in three forms: cylindrical, prismatic, and pouch cells. Cylindrical batteries are the most prevalent due to their extremely high manufacturing efficiency, high performance, reliability, and durability.

[0005] like Figure 1 As shown, a common cylindrical lithium-ion battery core assembly is formed by winding together a negative electrode 1, a first separator 3, a positive electrode 2, and a second separator 4 arranged in sequence. The core assembly is inserted into the battery casing 6, and a battery cell is formed after a series of processes such as welding, liquid injection, and sealing.

[0006] To prevent lithium deposition during battery cell recycling, the negative electrode material layer must cover the positive electrode material layer in all directions, and the effective capacity of the negative electrode material layer must be greater than the effective capacity of the corresponding positive electrode material layer. This ensures that lithium ions in the positive electrode active material can be completely inserted into the corresponding negative electrode active material during insertion / extraction.

[0007] The ratio of the effective capacity of the negative electrode material layer to the effective capacity of the positive electrode material layer is generally called the NP ratio (positive-negative electrode ratio). The NP ratio is a critical parameter in lithium-ion battery design, affecting not only the safety of the battery but also directly the cycle life and energy density of the cell. To ensure that lithium deposition does not occur during the battery's operation, current lithium-ion battery designs have a large margin in the NP ratio, which results in a significant waste of negative electrode material.

[0008] Therefore, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0009] The present invention aims to solve or alleviate the above-mentioned technical problems, namely, to solve or alleviate the problem that the existing battery NP ratio design has a large margin, resulting in a large waste of negative electrode material.

[0010] In a first aspect, the present application provides a jelly-roll assembly of a battery, which is formed by winding a negative electrode, a first separator, a positive electrode and a second separator in sequence, the negative electrode comprising a first negative electrode material layer, a second negative electrode material layer and a negative electrode current collector between the first negative electrode material layer and the second negative electrode material layer, the positive electrode comprising a first positive electrode material layer, a second positive electrode material layer and a positive electrode current collector between the first positive electrode material layer and the second positive electrode material layer, the first separator being between the second negative electrode material layer and the first positive electrode material layer, and the second separator being between the first negative electrode material layer and the second positive electrode material layer, wherein a ratio of an effective capacity per unit area of the second negative electrode material layer to an effective capacity per unit area of the first positive electrode material layer decreases along a direction away from a central hole of the jelly-roll assembly, and / or a ratio of an effective capacity per unit area of the first negative electrode material layer to an effective capacity per unit area of the second positive electrode material layer increases along the direction away from the central hole of the jelly-roll assembly.

[0011] In a preferred technical solution of the above jelly-roll assembly, the ratio of the effective capacity per unit area of the first negative electrode material layer to the effective capacity per unit area of the second positive electrode material layer is smaller than the ratio of the effective capacity per unit area of the second negative electrode material layer to the effective capacity per unit area of the first positive electrode material layer, and a ratio of a width of the first negative electrode material layer to a width of the second positive electrode material layer is equal to a ratio of a width of the second negative electrode material layer to a width of the first positive electrode material layer.

[0012] In a preferred technical solution of the above jelly-roll assembly, the face density of the second negative electrode material layer decreases along the direction away from the central hole, and the face density of the first positive electrode material layer remains substantially unchanged.

[0013] In a preferred technical solution of the above jelly-roll assembly, the compactness of the second negative electrode material layer decreases along the direction away from the central hole and the thickness of the second negative electrode material layer remains substantially unchanged, or the thickness of the second negative electrode material layer decreases along the direction away from the central hole and the compactness of the second negative electrode material layer remains substantially unchanged.

[0014] In a preferred technical solution of the above jelly-roll assembly, the face density of the second negative electrode material layer remains substantially unchanged, and the face density of the first positive electrode material layer increases along the direction away from the central hole.

[0015] In a preferred technical solution of the above jelly-roll assembly, the compactness of the first positive electrode material layer increases along the direction away from the central hole and the thickness of the first positive electrode material layer remains substantially unchanged.

[0016] In the preferred technical solution of the above-mentioned winding core assembly, the surface density of the first negative electrode material layer increases along the direction away from the center hole, and the surface density of the second positive electrode material layer remains substantially unchanged.

[0017] In the preferred technical solution of the above-mentioned winding core assembly, the compaction degree of the first negative electrode material layer increases along the direction away from the center hole and the thickness of the first negative electrode material layer remains substantially unchanged, or the thickness of the first negative electrode material layer increases along the direction away from the center hole and the compaction degree of the first negative electrode material layer remains substantially unchanged.

[0018] In the preferred technical solution of the above-mentioned winding core assembly, the surface density of the first negative electrode material layer remains substantially unchanged, and the surface density of the second positive electrode material layer decreases along the direction away from the center hole.

[0019] In the second aspect, the application further provides a battery comprising the above-mentioned winding core assembly.

[0020] In the case of adopting the above-mentioned technical solution, the winding core assembly of the application is formed by winding the negative electrode, the first separator, the positive electrode and the second separator arranged in sequence, the negative electrode comprises the first negative electrode material layer, the second negative electrode material layer and the negative electrode current collector between the first negative electrode material layer and the second negative electrode material layer, the positive electrode comprises the first positive electrode material layer, the second positive electrode material layer and the positive electrode current collector between the first positive electrode material layer and the second positive electrode material layer, the first separator is located between the second negative electrode material layer and the first positive electrode material layer, and the second separator is located between the first negative electrode material layer and the second positive electrode material layer, wherein the ratio of the effective capacity per unit area of the second negative electrode material layer to the effective capacity per unit area of the first positive electrode material layer decreases along the direction away from the center hole of the winding core assembly, and / or the ratio of the effective capacity per unit area of the first negative electrode material layer to the effective capacity per unit area of the second positive electrode material layer increases along the direction away from the center hole of the winding core assembly. Through such a setting, the design margin of the NP ratio can be reduced, thereby avoiding or reducing the waste of negative electrode active material.

[0021] Further, the ratio of the effective capacity per unit area of the first negative electrode material layer to the effective capacity per unit area of the second positive electrode material layer is less than the ratio of the effective capacity per unit area of the second negative electrode material layer to the effective capacity per unit area of the first positive electrode material layer. Through such a setting, the design margin of the NP ratio can be further reduced.

[0022] In addition, the battery further provided by the application on the basis of the above-mentioned technical solution has the technical effects possessed by the above-mentioned winding core assembly due to the adoption of the above-mentioned winding core assembly. Compared with the battery before improvement, the design margin of the NP ratio of the battery of the application is small, thereby avoiding or reducing the waste of negative electrode active material. BRIEF DESCRIPTION OF DRAWINGS

[0023] The preferred embodiments of the present application will be described below with reference to the lithium-ion battery as an example and in conjunction with the accompanying drawings, in which:

[0024] Figure 1 is a structural schematic diagram of the lithium-ion battery of the present application;

[0025] Figure 2 is a cross-sectional partial schematic diagram of the roll core assembly of the present application;

[0026] Figure 3 is a structural schematic diagram of the negative electrode and the positive electrode of the first embodiment of the present application;

[0027] Figure 4 is a structural schematic diagram of the negative electrode and the positive electrode of the second embodiment of the present application;

[0028] Figure 5 is a structural schematic diagram of the negative electrode and the positive electrode of the third embodiment of the present application;

[0029] Figure 6 is a structural schematic diagram of the negative electrode and the positive electrode of the fourth embodiment of the present application;

[0030] Figure 7 is a structural schematic diagram of the negative electrode and the positive electrode of the fifth embodiment of the present application;

[0031] Figure 8 is a structural schematic diagram of the negative electrode and the positive electrode of the sixth embodiment of the present application.

[0032] List of reference signs:

[0033] 1, negative electrode; 11, first negative electrode material layer; 12, second negative electrode material layer; 13, negative electrode current collector; 2, positive electrode; 21, first positive electrode material layer; 22, second positive electrode material layer; 23, positive electrode current collector; 3, first separator; 4, second separator; 5, center hole; 6, shell. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present application will be described below with reference to the lithium-ion battery as an example and in conjunction with the accompanying drawings, in which:

[0035] For example, although the following is introduced with the lithium-ion battery as an example, the technical solutions of the present application can also be applied to other batteries with similar structures to the lithium-ion battery, such as sodium-ion batteries and the like, and such adjustment and change of the application object do not deviate from the principles and scope of the present application, and should be limited within the protection scope of the present application.

[0036] It should be noted that in the description of the present application, the terms "upper", "lower", "left", "right", and the like indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings, which is merely for the convenience of description, and does not indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0037] First refer to Figure 1 and Figure 2 , wherein, Figure 1 is a structural schematic diagram of the lithium ion battery of the present application; Figure 2 is a cross-sectional partial schematic diagram of the roll core assembly of the present application.

[0038] As shown in Figure 1 and Figure 2 , the lithium ion battery of the present application comprises a shell 6 and a roll core assembly located in the shell 6, wherein the roll core assembly comprises a negative electrode 1, a first separator 3, a positive electrode 2 and a second separator 4 stacked in sequence, the negative electrode 1, the first separator 3, the positive electrode 2 and the second separator 4 are wound to form a roll core assembly, and a central hole 5 is formed at the center position of the roll core assembly after winding is completed.

[0039] Continue to refer to Figure 1 and Figure 2 , the negative electrode 1 comprises a first negative electrode material layer 11, a second negative electrode material layer 12 and a negative electrode current collector 13 located between the first negative electrode material layer 11 and the second negative electrode material layer 12, the positive electrode 2 comprises a first positive electrode material layer 21, a second positive electrode material layer 22 and a positive electrode current collector 23 located between the first positive electrode material layer 21 and the second positive electrode material layer 22, the first separator 3 is located between the second negative electrode material layer 12 and the first positive electrode material layer 21, and the second separator 4 is located between the first negative electrode material layer 11 and the second positive electrode material layer 22.

[0040] Among them, the negative electrode current collector 13 generally adopts copper foil, and the negative electrode active material is coated on both sides of the copper foil to form the first negative electrode material layer 11 and the second negative electrode material layer 12 on both sides of the negative electrode current collector 13, and the positive electrode current collector 23 generally adopts aluminum foil, and the positive electrode active material is coated on both sides of the aluminum foil to form the first positive electrode material layer 21 and the second positive electrode material layer 22 on both sides of the positive electrode current collector 23.

[0041] The ratio of the effective capacity per unit area of ​​the second negative electrode material layer 12 to the effective capacity per unit area of ​​the first positive electrode material layer 21 decreases in the direction away from the center hole 5 of the core assembly, and / or the ratio of the effective capacity per unit area of ​​the first negative electrode material layer 11 to the effective capacity per unit area of ​​the second positive electrode material layer 22 increases in the direction away from the center hole 5 of the core assembly.

[0042] This configuration reduces the design margin of the NP ratio, thereby avoiding or minimizing the waste of negative electrode active material.

[0043] Specifically, such as Figure 2 As shown, during battery use, lithium ions that are deintercalated from the first positive electrode material layer 21 pass through the first separator 3 and are embedded into the second negative electrode material layer 12 at the corresponding position. In order to avoid lithium deposition, the effective capacity of the second negative electrode material layer 12 must be greater than the effective capacity of the first positive electrode material layer 21 at the corresponding position.

[0044] For ease of understanding, the ratio of the effective capacity of the second negative electrode material layer 12 to the effective capacity of the first positive electrode material layer 21 in each turn is used as a unit, i.e., the NP ratio = (L... S2 ×a×Qs2) / (Ln1×b×Qn1), where L S2 Let be the arc length of the second negative electrode material layer 12, a be the width of the second negative electrode material layer 12, Qs2 be the effective capacity per unit area of ​​the second negative electrode material layer 12, Ln1 be the arc length of the first positive electrode material layer 21, b be the width of the first positive electrode material layer 21, and Qn1 be the effective capacity per unit area of ​​the first positive electrode material layer 21.

[0045] The height of the battery (or the length of the battery) is fixed, that is, the width a of the second negative electrode material layer 12 and the width b of the first positive electrode material layer 21 are both fixed values. In addition, in the existing lithium-ion battery design, the effective capacity Qs2 per unit area of ​​the second negative electrode material layer 12 and the effective capacity Qn1 per unit area of ​​the first positive electrode material layer 21 are also fixed values.

[0046] from Figure 2 As can be seen, the first positive electrode material layer 21 surrounds the outer side of the second negative electrode material layer 12. Therefore, the arc length Ln1 of the first positive electrode material layer 21 is greater than the arc length L of the corresponding position of the second negative electrode material layer 12. S2 As the diameter of the core assembly increases, L S2 As the ratio of Ln1 increases, the NP ratio per turn also increases. That is, the closer to the center hole 5 of the core assembly, the smaller the NP ratio, and the farther away from the center hole 5 of the core assembly, the larger the NP ratio.

[0047] Assuming that the ratio of the effective capacity of the second negative electrode material layer 12 to the effective capacity of the first positive electrode material layer 21, i.e. NP, in the first circle (the circle closest to the center hole 5 of the winding core assembly) is designed to be 1.1, the NP ratio in the fifth circle can reach 1.4, and the total NP ratio of the second negative electrode material layer 12 and the first positive electrode material layer 21 can be close to 1.3, which is too large in design allowance, resulting in a huge waste of negative electrode active material.

[0048] In the present application, the ratio of the effective capacity per unit area of the second negative electrode material layer 12 to the effective capacity per unit area of the first positive electrode material layer 21 decreases in the direction away from the center hole 5 of the winding core assembly.

[0049] In this way, as the winding diameter of the winding core assembly increases, although L S2 The ratio of Ln1 to L increases, but the ratio of Qs2 to Qn1 decreases, so that the NP ratio of each odd-numbered circle (1, 3, 5,...) can remain unchanged or change little, thereby avoiding or reducing the waste of negative electrode active material.

[0050] Similarly, as Figure 2 shown, during battery use, lithium ions deintercalated from the second positive electrode material layer 22 pass through the second separator 4 and are intercalated into the corresponding first negative electrode material layer 11, and in order to avoid lithium deposition, the effective capacity of the first negative electrode material layer 11 must be greater than the effective capacity of the corresponding second positive electrode material layer 22.

[0051] Again, in units of circles, the ratio of the effective capacity of the first negative electrode material layer 11 to the effective capacity of the second positive electrode material layer 22 in each circle, i.e. NP ratio = (L S1 × a × Qs1) / (Ln2 × b × Qn2), where L S1 is the arc length of the first negative electrode material layer 11, a is the width of the first negative electrode material layer 11, Qs1 is the effective capacity per unit area of the first negative electrode material layer 11, Ln2 is the arc length of the second positive electrode material layer 22, b is the width of the second positive electrode material layer 22, and Qn2 is the effective capacity per unit area of the second positive electrode material layer 22.

[0052] In the design of existing lithium ion batteries, the width a of the first negative electrode material layer 11, the effective capacity per unit area Qs1 of the first negative electrode material layer 11, the width b of the second positive electrode material layer 22, and the effective capacity per unit area Qn2 of the second positive electrode material layer 22 are all fixed values.

[0053] As can be seen from Figure 2 , the first negative electrode material layer 11 is arranged on the outside of the second positive electrode material layer 22, so the arc length L S1The ratio of L to Ln2 becomes smaller as the winding diameter of the winding core assembly increases, and thus the NP ratio of each turn also becomes smaller, that is, the NP ratio is larger closer to the center hole 5 of the winding core assembly and smaller farther from the center hole 5 of the winding core assembly. S1 The ratio of L to Ln2 becomes smaller as the winding diameter of the winding core assembly increases, and thus the NP ratio of each turn also becomes smaller, that is, the NP ratio is larger closer to the center hole 5 of the winding core assembly and smaller farther from the center hole 5 of the winding core assembly.

[0054] Suppose that the ratio of the effective capacity of the first negative electrode material layer 11 to the effective capacity of the second positive electrode material layer 22, that is, the NP ratio, is designed to be 1.1 for the sixth turn (farthest from the center hole 5 of the winding core assembly), the NP ratio for the second turn can reach 1.4, and the total NP ratio of the first negative electrode material layer 11 and the second positive electrode material layer 22 can be close to 1.3, and the design margin of the NP ratio is too large, resulting in a large waste of negative electrode active material.

[0055] In the present application, the ratio of the effective capacity per unit area of the first negative electrode material layer 11 to the effective capacity per unit area of the second positive electrode material layer 22 becomes larger in the direction away from the center hole 5 of the winding core assembly.

[0056] In this way, as the winding diameter of the winding core assembly increases, although L S1 The ratio of L to Ln2 becomes smaller as the winding diameter of the winding core assembly increases, and thus the NP ratio of each turn also becomes smaller, that is, the NP ratio is larger closer to the center hole 5 of the winding core assembly and smaller farther from the center hole 5 of the winding core assembly.

[0057] Preferably, the ratio of the effective capacity per unit area of the first negative electrode material layer 11 to the effective capacity per unit area of the second positive electrode material layer 22 is smaller than the ratio of the effective capacity per unit area of the second negative electrode material layer 12 to the effective capacity per unit area of the first positive electrode material layer 21, and the ratio of the width of the first negative electrode material layer 11 to the width of the second positive electrode material layer 22 is equal to the ratio of the width of the second negative electrode material layer 12 to the width of the first positive electrode material layer 21.

[0058] That is, Q S1 / Qn2 < Q S2 / Qn1, by such a setting, the design margin of the NP ratio can be further reduced.

[0059] Specifically, in the design of the existing lithium ion battery, the effective capacity per unit area Q S1 of the first negative electrode material layer 11 is the same as the effective capacity per unit area Q S2 of the second negative electrode material layer 12, and similarly, the effective capacity per unit area Qn1 of the first positive electrode material layer 21 is the same as the effective capacity per unit area Qn2 of the second positive electrode material layer 22, then Q S1 / Qn2 = Q S2 / Qn1.

[0060] FromFigure 3 As can be seen, the first positive material layer 21 is arranged outside the second negative material layer 12, so the arc length Ln1 of the first positive material layer 21 is greater than the arc length Ln2 of the corresponding position of the second negative material layer 12, and L S2 S2 / n1<1; the first negative material layer 11 is arranged outside the second positive material layer 22, so the arc length Ln1 of the first negative material layer 11 is greater than the arc length Ln2 of the corresponding position of the second positive material layer 22, and L S1 S1 / Ln2>1.

[0061] Exemplarily, L S2 / n1=0.8, L S1 / Ln2=1.1, a / b=1.05, the ratio of the effective capacity of the second negative material layer 12 to the effective capacity of the first positive material layer 21 is NP1=1.1;

[0062] Then, Q S2 / Qn1=NP1÷(L S2 / n1×a / b) = 1.1÷(0.8×1.05)≈1.31;

[0063] Then, Qs1 / Qn2=Q S2 / Qn1≈1.31;

[0064] Then, the ratio of the effective capacity of the first negative material layer 11 to the effective capacity of the second positive material layer 22 is NP2=L S1 / Ln2×a / b×Qs1 / Qn2=1.1×1.05×1.31≈1.51, NP2 is quite different from NP1.

[0065] However, in the present application, Qs1 / Qn2<Q S2 / Qn1, and then according to the above example, Q S2 / Qn1=1.31, Qs1 / Qn2 can be designed as 1.0,

[0066] Then, NP2=L S1 / Ln2×a / b×Qs1 / Qn2=1.1×1.05×1.0=1.16, NP2 is quite different from NP1. Qs1 / Qn2 can also be designed as 0.95,

[0067] Then, NP2=L S1 / Ln2×a / b×Qs1 / Qn2=1.1×1.05×0.95≈1.1, NP2 is the same as NP1.

[0068] ​​It should be noted that, in practical applications, the effective capacity per unit area of ​​the first negative electrode material layer 11 can be equal to the effective capacity per unit area of ​​the second negative electrode material layer 12, while the effective capacity per unit area of ​​the first positive electrode material layer 21 can be less than the effective capacity per unit area of ​​the second positive electrode material layer 22. Alternatively, the effective capacity per unit area of ​​the first positive electrode material layer 21 can be equal to the effective capacity per unit area of ​​the second positive electrode material layer 22, while the effective capacity per unit area of ​​the first negative electrode material layer 11 can be less than the effective capacity per unit area of ​​the second negative electrode material layer 12, and so on. Such flexible adjustments and changes do not deviate from the principles and scope of the present invention and should all be limited to the protection scope of the present invention.

[0069] The technical solution of the present invention will be described in detail below with reference to six specific embodiments.

[0070] Implementation 1

[0071] The following is combined Figure 3 The first embodiment of the present invention will be described in detail.

[0072] like Figure 3 As shown, the negative electrode 1 in this embodiment includes a first negative electrode material layer 11, a second negative electrode material layer 12, and a negative electrode current collector 13, wherein the first negative electrode material layer 11 is disposed on the upper surface of the negative electrode current collector 13, and the second negative electrode material layer 12 is disposed on the lower surface of the negative electrode current collector 13.

[0073] Continue reading Figure 3 In this embodiment, the positive electrode 2 includes a first positive electrode material layer 21, a second positive electrode material layer 22, and a positive electrode current collector 23. The first positive electrode material layer 21 is disposed on the upper surface of the positive electrode current collector 23, and the second positive electrode material layer 22 is disposed on the lower surface of the positive electrode current collector 23.

[0074] For example, when manufacturing the core assembly, winding begins with the left ends of the negative electrode 1 and the positive electrode 2 as the starting point. After winding is completed, the left ends of the negative electrode 1 and the positive electrode 2 are close to the center hole 5 of the core assembly, and the right ends of the negative electrode 1 and the positive electrode 2 are far away from the center hole 5 of the core assembly.

[0075] Continue reading Figure 3 The areal density of the second negative electrode material layer 12 decreases along the direction away from the central hole 5, that is, the areal density of the second negative electrode material layer 12 decreases from left to right; the areal density of the first positive electrode material layer 21 remains basically unchanged.

[0076] As the areal density of the second negative electrode material layer 12 decreases, the effective capacity per unit area of ​​the second negative electrode material layer 12 also decreases. As the areal density of the first positive electrode material layer 21 remains basically unchanged, the effective capacity per unit area of ​​the first positive electrode material layer 21 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the second negative electrode material layer 12 to the effective capacity per unit area of ​​the corresponding first positive electrode material layer 21 decreases along the direction away from the central hole 5.

[0077] Continue reading Figure 3 The compaction degree of the second negative electrode material layer 12 decreases in the direction away from the central hole 5, while the thickness of the second negative electrode material layer 12 remains basically unchanged. That is, the compaction degree of the second negative electrode material layer 12 decreases from left to right. With the thickness remaining basically unchanged, the compaction degree decreases, and the effective capacity per unit area decreases accordingly.

[0078] Continue reading Figure 3 The areal density of the first negative electrode material layer 11 increases in the direction away from the central hole 5, that is, the areal density of the first negative electrode material layer 11 increases from left to right; the areal density of the second positive electrode material layer 22 remains basically unchanged.

[0079] As the areal density of the first negative electrode material layer 11 increases, the effective capacity per unit area of ​​the first negative electrode material layer 11 also increases. As the areal density of the second positive electrode material layer 22 remains basically unchanged, the effective capacity per unit area of ​​the second positive electrode material layer 22 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the first negative electrode material layer 11 to the effective capacity per unit area of ​​the corresponding second positive electrode material layer 22 increases along the direction away from the central hole 5.

[0080] Continue reading Figure 4 The compaction degree of the first negative electrode material layer 11 increases in the direction away from the central hole 5 while the thickness of the first negative electrode material layer 11 remains basically unchanged. That is, the compaction degree of the first negative electrode material layer 11 increases from left to right. With the thickness remaining basically unchanged, the compaction degree increases, and the effective capacity per unit area increases accordingly.

[0081] Example 2

[0082] The following is combined Figure 4 The second embodiment of the present invention will be described in detail.

[0083] like Figure 5 As shown, in this embodiment, while keeping other settings unchanged in the first embodiment, the thickness of the second negative electrode material layer 12 decreases along the direction away from the central hole 5, and the compaction degree of the second negative electrode material layer 12 remains basically unchanged. That is, the thickness of the second negative electrode material layer 12 decreases from left to right. With the compaction degree remaining basically unchanged, the thickness decreases, and the effective capacity per unit area decreases accordingly.

[0084] The thickness of the first negative electrode material layer 11 increases in the direction away from the central hole 5, while the compaction degree of the first negative electrode material layer 11 remains basically unchanged. That is, the thickness of the first negative electrode material layer 11 increases from left to right. With the compaction degree remaining basically unchanged, the thickness increases, and the effective capacity per unit area increases accordingly.

[0085] Example 3

[0086] The following is combined Figure 5 The third embodiment of the present invention will be described in detail.

[0087] like Figure 5 As shown, similar to Embodiment 1, the negative electrode 1 in this embodiment includes a first negative electrode material layer 11, a second negative electrode material layer 12, and a negative electrode current collector 13, wherein the first negative electrode material layer 11 is disposed on the upper surface of the negative electrode current collector 13, and the second negative electrode material layer 12 is disposed on the lower surface of the negative electrode current collector 13; the positive electrode 2 includes a first positive electrode material layer 21, a second positive electrode material layer 22, and a positive electrode current collector 23, wherein the first positive electrode material layer 21 is disposed on the upper surface of the positive electrode current collector 23, and the second positive electrode material layer 22 is disposed on the lower surface of the positive electrode current collector 23.

[0088] For example, when manufacturing the core assembly, the left ends of the negative electrode 1 and the positive electrode 2 are taken as the starting ends. After winding, the left ends of the negative electrode 1 and the positive electrode 2 are close to the center hole 5 of the core assembly, and the right ends of the negative electrode 1 and the positive electrode 2 are far away from the center hole 5 of the core assembly.

[0089] Continue reading Figure 5 The areal density of the second negative electrode material layer 12 remains basically unchanged; the areal density of the first positive electrode material layer 21 increases in the direction away from the central hole 5, that is, the areal density of the first positive electrode material layer 21 increases from left to right.

[0090] As the areal density of the first positive electrode material layer 21 increases, the effective capacity per unit area of ​​the first positive electrode material layer 21 also increases. As the areal density of the second negative electrode material layer 12 remains basically unchanged, the effective capacity per unit area of ​​the second negative electrode material layer 12 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the second negative electrode material layer 12 to the effective capacity per unit area of ​​the corresponding first positive electrode material layer 21 decreases along the direction away from the central hole 5.

[0091] Continue reading Figure 5 The compaction degree of the first positive electrode material layer 21 increases in the direction away from the central hole 5 while the thickness of the first positive electrode material layer 21 remains basically unchanged. That is, the compaction degree of the first positive electrode material layer 21 increases from left to right. With the thickness remaining basically unchanged, the compaction degree increases, and the effective capacity per unit area increases accordingly.

[0092] Continue reading Figure 5The areal density of the first negative electrode material layer 11 increases in the direction away from the central hole 5, that is, the areal density of the first negative electrode material layer 11 increases from left to right; the areal density of the second positive electrode material layer 22 remains basically unchanged.

[0093] As the areal density of the first negative electrode material layer 11 increases, the effective capacity per unit area of ​​the first negative electrode material layer 11 also increases. As the areal density of the second positive electrode material layer 22 remains basically unchanged, the effective capacity per unit area of ​​the second positive electrode material layer 22 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the first negative electrode material layer 11 to the effective capacity per unit area of ​​the corresponding second positive electrode material layer 22 increases along the direction away from the central hole 5.

[0094] Continue reading Figure 6 The compaction degree of the first negative electrode material layer 11 increases in the direction away from the central hole 5 while the thickness of the first negative electrode material layer 11 remains basically unchanged. That is, the compaction degree of the first negative electrode material layer 11 increases from left to right. With the thickness remaining basically unchanged, the compaction degree increases, and the effective capacity per unit area increases accordingly.

[0095] Implementation 4

[0096] The following is combined Figure 6 The fourth embodiment of the present invention will be described in detail.

[0097] like Figure 6 As shown, similar to the first embodiment, in this embodiment, the negative electrode 1 includes a first negative electrode material layer 11, a second negative electrode material layer 12, and a negative electrode current collector 13, wherein the first negative electrode material layer 11 is disposed on the upper surface of the negative electrode current collector 13, and the second negative electrode material layer 12 is disposed on the lower surface of the negative electrode current collector 13; the positive electrode 2 includes a first positive electrode material layer 21, a second positive electrode material layer 22, and a positive electrode current collector 23, wherein the first positive electrode material layer 21 is disposed on the upper surface of the positive electrode current collector 23, and the second positive electrode material layer 22 is disposed on the lower surface of the positive electrode current collector 23.

[0098] For example, when manufacturing the core assembly, the left ends of the negative electrode 1 and the positive electrode 2 are taken as the starting ends. After winding, the left ends of the negative electrode 1 and the positive electrode 2 are close to the center hole 5 of the core assembly, and the right ends of the negative electrode 1 and the positive electrode 2 are far away from the center hole 5 of the core assembly.

[0099] Continue reading Figure 6 The areal density of the second negative electrode material layer 12 decreases along the direction away from the central hole 5, that is, the areal density of the second negative electrode material layer 12 decreases from left to right; the areal density of the first positive electrode material layer 21 remains basically unchanged.

[0100] As the areal density of the second negative electrode material layer 12 decreases, the effective capacity per unit area of ​​the second negative electrode material layer 12 also decreases. As the areal density of the first positive electrode material layer 21 remains basically unchanged, the effective capacity per unit area of ​​the first positive electrode material layer 21 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the second negative electrode material layer 12 to the effective capacity per unit area of ​​the corresponding first positive electrode material layer 21 decreases along the direction away from the central hole 5.

[0101] Continue reading Figure 6 The compaction degree of the second negative electrode material layer 12 decreases along the direction away from the central hole 5, while the thickness of the second negative electrode material layer 12 remains essentially constant; that is, the compaction degree of the second negative electrode material layer 12 decreases from left to right. With the thickness remaining essentially constant, the decrease in compaction degree leads to a decrease in the effective capacity per unit area.

[0102] Continue reading Figure 6 The surface density of the first negative electrode material layer 11 remains basically unchanged; the surface density of the second positive electrode material layer 22 decreases along the direction away from the central hole 5, that is, the surface density of the second positive electrode material layer 22 decreases from left to right.

[0103] As the areal density of the second positive electrode material layer 22 decreases, the effective capacity per unit area of ​​the second positive electrode material layer 22 also decreases. As the areal density of the first negative electrode material layer 11 remains basically unchanged, the effective capacity per unit area of ​​the first negative electrode material layer 11 also remains basically unchanged. The ratio of the effective capacity per unit area of ​​the first negative electrode material layer 11 to the effective capacity per unit area of ​​the corresponding second positive electrode material layer 22 increases along the direction away from the central hole 5.

[0104] Continue reading Figure 7 The compaction degree of the second positive electrode material layer 22 decreases in the direction away from the central hole 5, while the thickness of the second positive electrode material layer 22 remains basically unchanged. That is, the compaction degree of the second positive electrode material layer 22 decreases from left to right. With the thickness remaining basically unchanged, the compaction degree decreases, and the effective capacity per unit area decreases accordingly.

[0105] Implementation of Five

[0106] The following is combined Figure 7 The fifth embodiment of the present invention will now be described in detail.

[0107] like Figure 7As shown, similar to the first embodiment, in the present embodiment, the negative electrode 1 comprises the first negative electrode material layer 11, the second negative electrode material layer 12 and the negative electrode current collector 13, wherein the first negative electrode material layer 11 is arranged on the upper surface of the negative electrode current collector 13, and the second negative electrode material layer 12 is arranged on the lower surface of the negative electrode current collector 13; the positive electrode 2 comprises the first positive electrode material layer 21, the second positive electrode material layer 22 and the positive electrode current collector 23, wherein the first positive electrode material layer 21 is arranged on the upper surface of the positive electrode current collector 23, and the second positive electrode material layer 22 is arranged on the lower surface of the positive electrode current collector 23.

[0108] Exemplarily, when the roll core assembly is made, the left end of the negative electrode 1 and the positive electrode 2 is taken as the starting end, after the winding is completed, the left end of the negative electrode 1 and the positive electrode 2 is close to the center hole 5 of the roll core assembly, and the right end of the negative electrode 1 and the positive electrode 2 is away from the center hole 5 of the roll core assembly.

[0109] Continuing to refer to Figure 7 , the surface density of the second negative electrode material layer 12 is basically kept unchanged; the surface density of the first positive electrode material layer 21 is increased along the direction away from the center hole 5, that is, the surface density of the first positive electrode material layer 21 is increased from left to right.

[0110] The surface density of the first positive electrode material layer 21 is increased, then the effective capacity per unit area of the first positive electrode material layer 21 is increased, the surface density of the second negative electrode material layer 12 is basically kept unchanged, then the effective capacity per unit area of the second negative electrode material layer 12 is also basically kept unchanged, and the ratio of the effective capacity per unit area of the second negative electrode material layer 12 to the effective capacity per unit area of the corresponding first positive electrode material layer 21 is decreased along the direction away from the center hole 5.

[0111] Continuing to refer to Figure 7 , the compaction degree of the first positive electrode material layer 21 is increased along the direction away from the center hole 5 and the thickness of the first positive electrode material layer 21 is basically kept unchanged. That is, the compaction degree of the first positive electrode material layer 21 is increased from left to right, and in the case that the thickness is basically kept unchanged, the compaction degree is increased, and then the effective capacity per unit area is increased.

[0112] Continuing to refer to Figure 7 , the surface density of the first negative electrode material layer 11 is basically kept unchanged; the surface density of the second positive electrode material layer 22 is decreased along the direction away from the center hole 5, that is, the surface density of the second positive electrode material layer 22 is decreased from left to right.

[0113] The face density of the second positive material layer 22 is smaller, the effective capacity per unit area of the second positive material layer 22 is smaller, the face density of the first negative material layer 11 is basically unchanged, the effective capacity per unit area of the first negative material layer 11 is basically unchanged, and the ratio of the effective capacity per unit area of the first negative material layer 11 to the effective capacity per unit area of the corresponding second positive material layer 22 is larger along the direction away from the center hole 5.

[0114] Continuing to refer to Figure 8 , the compaction degree of the second positive material layer 22 is smaller along the direction away from the center hole 5 and the thickness of the second positive material layer 22 is basically unchanged, that is, the thickness of the second positive material layer 22 is smaller from left to right, and in the case that the compaction degree is basically unchanged, the thickness is smaller, and the effective capacity per unit area is smaller.

[0115] Embodiment six

[0116] The sixth embodiment of the present application will be described in detail below. Figure 8

[0117] As ​ shown, in the fifth embodiment, other setting conditions are unchanged, and in the present embodiment, the thickness of the first positive material layer 21 is larger along the direction away from the center hole 5 and the compaction degree of the first positive material layer 21 is basically unchanged, that is, the thickness of the first positive material layer 21 is larger from left to right, and in the case that the compaction degree is basically unchanged, the thickness is larger, and the effective capacity per unit area is larger.

[0118] The thickness of the second positive material layer 22 is smaller along the direction away from the center hole 5 and the compaction degree of the second positive material layer 22 is basically unchanged, that is, the thickness of the second positive material layer 22 is smaller from left to right, and in the case that the compaction degree is basically unchanged, the thickness is smaller, and the effective capacity per unit area is smaller.

[0119] In summary, in view of the problem that the design margin of the NP ratio of the existing lithium ion battery is large, the present application designs a non-uniform electrode, that is, the face density of the electrode has a design change along the length direction of the electrode, and by using the non-uniform electrode, the design margin of the NP ratio can be greatly reduced.

[0120] Thus far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.​

Claims

1. A battery winding assembly, characterized in that, The core assembly includes a negative electrode, a first separator, a positive electrode, and a second separator stacked sequentially. The stacked negative electrode, first separator, positive electrode, and second separator are wound to form the core assembly. The negative electrode includes a first negative electrode material layer, a second negative electrode material layer, and a negative electrode current collector located between the first negative electrode material layer and the second negative electrode material layer. The positive electrode includes a first positive electrode material layer, a second positive electrode material layer, and a positive electrode current collector located between the first positive electrode material layer and the second positive electrode material layer. The first separator is located between the second negative electrode material layer and the first positive electrode material layer, and the second separator is located between the first negative electrode material layer and the second positive electrode material layer. Wherein, the ratio of the effective capacity per unit area of ​​the second negative electrode material layer to the effective capacity per unit area of ​​the first positive electrode material layer decreases along the direction away from the center hole of the winding assembly, and / or The ratio of the effective capacity per unit area of ​​the first negative electrode material layer to the effective capacity per unit area of ​​the second positive electrode material layer increases in the direction away from the center hole of the core assembly.

2. The core assembly of claim 1, wherein, The ratio of the effective capacity per unit area of ​​the first negative electrode material layer to the effective capacity per unit area of ​​the second positive electrode material layer is less than the ratio of the effective capacity per unit area of ​​the second negative electrode material layer to the effective capacity per unit area of ​​the first positive electrode material layer, and The ratio of the width of the first negative electrode material layer to the width of the second positive electrode material layer is equal to the ratio of the width of the second negative electrode material layer to the width of the first positive electrode material layer.

3. The core assembly of claim 1, wherein, The areal density of the second negative electrode material layer decreases along the direction away from the central hole, while the areal density of the first positive electrode material layer remains essentially unchanged.

4. The core assembly of claim 3, wherein, The compaction of the second negative electrode material layer decreases along the direction away from the central hole, while the thickness of the second negative electrode material layer remains essentially constant. The thickness of the second negative electrode material layer decreases in the direction away from the central hole, and the compaction of the second negative electrode material layer remains basically unchanged.

5. The core assembly of claim 1, wherein, The areal density of the second negative electrode material layer remains essentially unchanged, while the areal density of the first positive electrode material layer increases in the direction away from the central hole.

6. The core assembly of claim 5, wherein, The compaction of the first positive electrode material layer increases in the direction away from the central hole, while the thickness of the first positive electrode material layer remains essentially unchanged.

7. The core assembly of any one of claims 1 to 6, wherein, The areal density of the first negative electrode material layer increases in the direction away from the central hole, while the areal density of the second positive electrode material layer remains essentially unchanged.

8. The core assembly of claim 7, wherein, The compaction of the first negative electrode material layer increases along the direction away from the central hole, while the thickness of the first negative electrode material layer remains essentially constant. The thickness of the first negative electrode material layer increases in the direction away from the central hole, while the compaction of the first negative electrode material layer remains essentially unchanged.

9. The core assembly of any one of claims 1 to 6, wherein, The areal density of the first negative electrode material layer remains essentially unchanged, while the areal density of the second positive electrode material layer decreases along the direction away from the central hole.

10. A battery, characterized by Includes the core assembly according to any one of claims 1 to 9.

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