Laminated cell and lithium ion battery

Abstract

The embodiment of the invention provides a laminated cell and a lithium ion battery, and relates to the technical field of lithium ion batteries. The laminated battery core comprises a first laminated core and a second laminated core, the first laminated core comprises a first positive plate (10), a first diaphragm and a first negative plate, the first positive plate, the first diaphragm and the first negative plate are staggered and laminated, and the second laminated core comprises a second positive plate, a second diaphragm and a second negative plate, and the second positive plate, the second diaphragm and the second negative plate are arranged in a staggered and laminated manner. The first stack core is used as a part with high mass energy density, and the second stack core is used as a quick charge part, so that the battery cell of the lithium ion battery has both high mass energy density and quick charge performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a laminated battery core and a lithium ion battery. Background Art

[0002] Lithium-ion batteries have been widely used in new energy vehicles due to their high energy density, no memory effect, and long cycle life. New energy vehicles currently have a common problem of range anxiety.

[0003] In the related technology, the range anxiety problem can be eliminated by increasing the driving range on a single charge, that is, the lithium-ion battery cell needs to have a high energy density to eliminate the range anxiety problem; the range anxiety problem can also be eliminated by shortening the single charging time, that is, improving the fast charging performance of the lithium-ion battery cell to eliminate the range anxiety problem.

[0004] However, lithium-ion battery cells have the problem of not being able to balance high energy density and fast charging performance. Summary of the invention

[0005] The embodiments of the present invention provide a laminated battery cell and a lithium-ion battery to solve the problem that the battery cell of the lithium-ion battery cannot balance high energy density and fast charging performance.

[0006] On the one hand, an embodiment of the present invention provides a laminated battery cell, comprising

[0007] A first core stack, wherein the first core stack comprises a first positive electrode sheet, a first separator and a first negative electrode sheet, wherein the first positive electrode sheet, the first separator and the first negative electrode sheet are alternately stacked;

[0008] The first positive electrode sheet comprises a first positive electrode current collector and a first positive electrode active material layer located on at least one side of the surface of the first positive electrode current collector;

[0009] The first negative electrode sheet comprises a first negative electrode current collector and a first negative electrode active material layer, wherein the first negative electrode active material layer is arranged on at least one side of the first negative electrode current collector in a thickness direction, and the first negative electrode active material layer comprises a first negative electrode active material, and the first negative electrode active material comprises a first silicon-based material;

[0010] A second core stack, wherein the second core stack comprises a second positive electrode sheet, a second separator and a second negative electrode sheet, wherein the second positive electrode sheet, the second separator and the second negative electrode sheet are alternately stacked;

[0011] The second positive electrode sheet comprises a second positive electrode current collector and a second positive electrode active material layer located on at least one side of the surface of the second positive electrode current collector;

[0012] The second negative electrode sheet comprises a second negative electrode current collector and a second negative electrode active material layer, the second negative electrode active material layer is arranged on at least one side of the second negative electrode current collector in a thickness direction, the second negative electrode active material layer comprises a second negative electrode active material, and the second negative electrode active material comprises a second silicon-based material;

[0013] The first stacked core is connected to a first positive electrode tab and a first negative electrode tab, and the second stacked core is connected to a second positive electrode tab and a second negative electrode tab;

[0014] Wherein, the surface density of the first positive electrode active material layer of the first positive electrode sheet is greater than the surface density of the second positive electrode active material layer of the second positive electrode sheet; and / or,

[0015] The content of the first silicon-based material in the first negative electrode active material layer of the first negative electrode sheet is greater than the content of the second silicon-based material in the second negative electrode active material layer of the second negative electrode sheet.

[0016] In a possible implementation manner, in the thickness direction of the laminated battery core, a third positive electrode sheet is disposed between the first separator and the second separator at the innermost side of the laminated battery core, and the surface density of the positive electrode active material layer of the third positive electrode sheet facing the first laminated core is greater than the surface density of the positive electrode active material layer of the third positive electrode sheet facing the second laminated core;

[0017] And / or, the N / P ratio of the first negative electrode sheet to the third positive electrode sheet and the N / P ratio of the second negative electrode sheet to the third positive electrode sheet are both 1.01 to 1.25, and the difference between the N / P ratio of the first negative electrode sheet to the third positive electrode sheet and the N / P ratio of the second negative electrode sheet to the third positive electrode sheet is -0.5 to 0.5.

[0018] In a possible implementation manner, a lithium supplement layer is provided on a surface of the first negative electrode active material layer of the first negative electrode sheet away from the first negative electrode current collector;

[0019] Preferably, the lithium replenishing layer comprises metal segments spaced apart from each other;

[0020] Preferably, the area of ​​the negative electrode active material layer of the first negative electrode sheet not covered by the lithium replenishing layer is the first area, the area of ​​the negative electrode active material layer of the first negative electrode sheet covered by the lithium replenishing layer is the second area, and the area ratio of the first area to the second area is 0.2-5.

[0021] In a possible implementation, the first negative electrode composite current collector includes a polymer layer and two metal layers located on opposite sides of the polymer layer, the thickness of the two metal layers is 0.3 to 5 μm, and the thickness of the polymer layer is 1 to 20 μm;

[0022] The material of the polymer layer includes polyethylene terephthalate, polyethylene or polypropylene;

[0023] Preferably, the tensile strength of the first negative electrode sheet is greater than or equal to 100 MPa.

[0024] In a possible implementation manner, the second positive electrode active material layer of the second positive electrode sheet and / or the second negative electrode active material layer of the second negative electrode sheet are provided with a recessed portion.

[0025] In a possible implementation manner, the recessed portion is disposed on the second negative electrode active material layer, and the recessed portion includes a plurality of circular holes or grooves spaced apart from each other;

[0026] Preferably, the distance between the centers of two adjacent circular holes is 0.5 to 5 mm, the diameter of the circular hole is 20 to 2000 μm, and the depth of the circular hole is 3 to 70 μm; or, in the thickness direction of the laminated battery core, the depth of the circular hole is greater than the sum of the thickness of the second negative electrode active material layer and the thickness of the second negative electrode current collector;

[0027] Preferably, the spacing between two adjacent grooves is 0.5-5 mm, and the depth of the groove is 3-70 μm; or, in the thickness direction of the laminated battery core, the depth of the groove is greater than the sum of the thickness of the second negative electrode active material layer and the thickness of the second negative electrode current collector.

[0028] In a possible implementation, the material of the first negative electrode active material layer of the first negative electrode sheet includes first graphite, and the median particle size (Dv50) of the first graphite is 2 to 40 μm;

[0029] The material of the second negative electrode active material layer of the second negative electrode sheet includes a second graphite, and the median particle size (Dv50) of the second graphite is 1 to 30 μm;

[0030] The median particle size of the second graphite is smaller than the median particle size (Dv50) of the first graphite, and the compaction density of the first graphite is greater than the compaction density of the second graphite.

[0031] In a possible implementation manner, the first negative electrode tab and the second negative electrode tab are connected to form a third negative electrode tab.

[0032] In a possible implementation manner, switches are provided between the first positive electrode tab and the first stacked core, and between the first negative electrode tab and the first stacked core;

[0033] In the length direction of the laminated battery core, the first positive electrode ear and the second positive electrode ear are located on the same side of the laminated battery core, and the first negative electrode ear and the second negative electrode ear are located on the same side of the laminated battery core;

[0034] In the length direction of the laminated battery core, the first positive electrode tab and the first negative electrode tab are respectively located on both sides of the laminated battery core, and the second positive electrode tab and the second negative electrode tab are respectively located on both sides of the laminated battery core.

[0035] In a possible implementation manner, the surface density of the first positive electrode active material layer of the first positive electrode sheet is 5 to 40 mg / cm 2 ;

[0036] The surface density of the second positive electrode active material layer of the second positive electrode sheet is 5 to 40 mg / cm 2 ;

[0037] The first silicon-based material content in the first negative electrode active material layer of the first negative electrode sheet is 5-50 wt %; the second silicon-based material content in the second negative electrode active material layer of the second negative electrode sheet is 0-40 wt %.

[0038] On the other hand, an embodiment of the present invention provides a lithium-ion battery, comprising a housing and the laminated battery core as described above, wherein the laminated battery core is disposed in the housing.

[0039] The embodiments of the present invention provide a laminated battery cell and a lithium-ion battery. By making the surface density of the positive electrode active material layer of the first positive electrode sheet greater than the surface density of the positive electrode active material layer of the second positive electrode sheet, the mass of the positive electrode active material layer of the first positive electrode sheet can be greater than the mass of the positive electrode active material layer of the second positive electrode sheet, thereby making the first laminated battery cell have a high mass energy density.

[0040] The content of the first silicon-based material in the first negative electrode active material layer of the first negative electrode sheet is greater than the content of the second silicon-based material in the second negative electrode active material layer of the second negative electrode sheet, so that the gram capacity of the first negative electrode active material layer is greater than the gram capacity of the second negative electrode active material layer, thereby making the capacity of the first negative electrode sheet greater than the capacity of the second negative electrode sheet, which helps to improve the mass energy density of the first stack, thereby making the first stack have high mass energy density.

[0041] By using the first core stack as the high-quality energy density part and the second core stack as the fast-charging part, the lithium-ion battery cell can have both high-quality energy density and fast-charging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic diagram of the structure of a lithium-ion battery provided in Embodiment 1 of the present invention;

[0044] Figure 2 A schematic diagram of the structure of a laminated battery cell provided in the first embodiment of the present invention;

[0045] Figure 3 A schematic cross-sectional view of a first positive electrode sheet provided in Embodiment 1 of the present invention;

[0046] Figure 4 A cross-sectional schematic diagram of a first negative electrode sheet provided in Embodiment 1 of the present invention;

[0047] Figure 5 for Figure 4 A schematic top view of the first negative electrode sheet in FIG.

[0048] Figure 6 A cross-sectional schematic diagram of a second positive electrode sheet provided in Embodiment 1 of the present invention;

[0049] Figure 7 A schematic cross-sectional view of a second negative electrode sheet provided in Embodiment 1 of the present invention;

[0050] Figure 8 for Figure 7 A schematic top view of the second negative electrode sheet in FIG.

[0051] Fig. 9 A schematic top view of another second negative electrode sheet provided in the first embodiment of the present invention;

[0052] Fig.10 A schematic cross-sectional view of a third positive electrode sheet provided in the first embodiment of the present invention;

[0053] Fig.11 A physical schematic diagram of a lithium-ion battery provided in Example 1 of the present invention;

[0054] Fig.12 This is a schematic diagram of the structure of a lithium-ion battery provided in Example 2 of the present invention.

[0055] Description of reference numerals:

[0056] 100-first core stack; 10-first positive electrode sheet;

[0057] 10a-first positive electrode current collector; 10b-first positive electrode active material layer;

[0058] 11-a first negative electrode sheet; 11a-a first negative electrode current collector;

[0059] 11b-first negative electrode active material layer; 11c-lithium supplement layer;

[0060] 111-metal segment; 200-second core stack;

[0061] 20-a second positive electrode sheet; 20a-a second positive electrode current collector;

[0062] 20b - second positive electrode active material layer; 21 - second negative electrode sheet;

[0063] 21a-second negative electrode current collector; 21b-second negative electrode active material layer;

[0064] 20c-depressed portion; 30-third positive electrode sheet;

[0065] 30a-third positive electrode current collector; 30b-third positive electrode active material layer;

[0066] 301-first positive electrode ear; 401-second positive electrode ear;

[0067] 302-first negative electrode ear; 402-second negative electrode ear;

[0068] 500-Third negative electrode ear. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0071] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", "fixation" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0073] In the above description, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0074] In the related technology, the range anxiety problem can be eliminated by increasing the driving range of a single charge, that is, the lithium-ion battery cell needs to have a high energy density to eliminate the range anxiety problem; the range anxiety problem can also be eliminated by shortening the single charging time, that is, improving the fast charging performance of the lithium-ion battery cell to eliminate the range anxiety problem. However, the lithium-ion battery cell has the problem of not taking into account both high energy density and fast charging performance.

[0075] In order to solve the above problems, an embodiment of the present invention provides a laminated battery cell and a lithium-ion battery, which divides the laminated battery cell into two parts, one part of the battery cell has high quality energy density, and the other part has fast charging performance, so that the battery cell of the lithium-ion battery has both high quality energy density and fast charging performance.

[0076] The laminated battery cell and lithium-ion battery provided by the embodiments of the present invention are described in detail below in conjunction with specific embodiments.

[0077] See also Figure 1 , Figure 2 and Fig.11 As shown, an embodiment of the present invention provides a laminated battery core, including a first laminated core 100 and a second laminated core 200 .

[0078] See also Figure 2As shown, the length direction of the laminated battery core is the X-axis direction, and the width direction of the laminated battery core is the Y-axis direction (see Figure 5 As shown in the figure, the thickness direction of the laminated battery cell is the Z-axis direction, and the X-axis, Y-axis and Z-axis are perpendicular to each other.

[0079] See also Figure 2 As shown, the first stacked core 100 includes a first positive electrode sheet 10, a first separator (not shown in the figure) and a first negative electrode sheet 11. In the thickness direction of the stacked core, the first positive electrode sheet 10, the first separator and the first negative electrode sheet 11 are alternately stacked. The first separator is arranged between the first positive electrode sheet 10 and the first negative electrode sheet 11, and the first separator plays a role in isolating electrons.

[0080] The second stacked core 200 includes a second positive electrode sheet 20, a second separator (not shown in the figure) and a second negative electrode sheet 21. In the thickness direction of the stacked core, the second positive electrode sheet 20, the second separator and the second negative electrode sheet 21 are alternately stacked. The second separator is arranged between the second positive electrode sheet 20 and the second negative electrode sheet 21, and the second separator plays the role of isolating electrons.

[0081] The first positive electrode sheet 10 includes a first positive electrode current collector 10 a and a first positive electrode active material layer 10 b located on at least one side of a surface of the first positive electrode current collector 10 a .

[0082] The first negative electrode sheet 11 includes a first negative electrode collector 11a and a first negative electrode active material layer 11b. The first negative electrode active material layer 11b is arranged on at least one side of the first negative electrode collector 11a in the thickness direction, that is, the first negative electrode active material layer 11b is arranged on at least one side of the surface of the first negative electrode collector 11a.

[0083] In the thickness direction of the laminated battery core, when the outermost electrode sheet of the first laminated core 100 is the first positive electrode sheet 10, only one side of the surface of the first positive electrode collector 10a of the first positive electrode sheet 10 is provided with the first positive electrode active material layer 10b, and the first positive electrode active material layers 10b are respectively provided on both sides of the surface of the first positive electrode collector 10a of the remaining first positive electrode sheets 10 of the first laminated core 100, and the first negative electrode active material layers 11b are respectively provided on both sides of the surface of the first negative electrode collector 11a of each first negative electrode sheet 11 of the first laminated core 100.

[0084] In the thickness direction of the laminated battery cell, when the outermost electrode sheet of the first laminated core 100 is the first negative electrode sheet 11, only one side of the surface of the first negative electrode collector 11a of the first negative electrode sheet 11 is provided with the first negative electrode active material layer 11b, and the first negative electrode active material layers 11b are respectively provided on both sides of the surface of the first negative electrode collector 11a of the remaining first negative electrode sheets 11 of the first laminated core 100, and the first positive electrode active material layers 10b are respectively provided on both sides of the surface of the first positive electrode collector 10a of each first positive electrode sheet 10 of the first laminated core 100.

[0085] For example, see Figure 3 As shown, the first positive electrode sheet 10 includes a first positive electrode current collector 10a and two first positive electrode active material layers 10b located on the first positive electrode current collector 10a. Aluminum foil, copper foil or a composite current collector can be used as the first positive electrode current collector 10a.

[0086] The two first positive electrode active material layers 10 b are disposed on opposite sides of the first positive electrode current collector 10 a in the thickness direction, that is, one first positive electrode active material layer 10 b is disposed on each side of the first positive electrode current collector 10 a in the thickness direction.

[0087] The thicknesses of the first positive electrode active material layers 10 b of the first core stack 100 may be the same.

[0088] The material of the first positive electrode active material layer 10 b includes lithium cobalt oxide, ternary materials, lithium iron phosphate, lithium iron manganese phosphate or lithium-rich manganese-based materials, etc. The ternary materials include nickel-cobalt-manganese or nickel-cobalt-aluminum.

[0089] As the first negative electrode current collector 11 a , an aluminum foil, a copper foil, or a composite current collector may be used.

[0090] The outermost electrode sheet of the first stacked core 100 in the thickness direction of the stacked core is the first negative electrode sheet 11, and the first negative electrode sheet 11 is provided with a first negative electrode active material layer 11b, and the first negative electrode active material layer 11b is provided on one side of the first negative electrode current collector 11a in the thickness direction. Figure 4 As shown, the remaining first negative electrode sheet 11 is provided with two layers of first negative electrode active material layer 11b, and the two layers of first negative electrode active material layer 11b are arranged on opposite sides of the thickness direction of the first negative electrode collector 11a, that is, one layer of first negative electrode active material layer 11b is respectively arranged on both sides of the thickness direction of the first negative electrode collector 11a.

[0091] The first negative electrode active material layers 11 b of the first core stack 100 have the same thickness.

[0092] The first negative electrode active material layer 11 b includes a first negative electrode active material, which includes at least one of first graphite, hard carbon, silicon-oxygen material, and silicon-carbon.

[0093] The N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is the ratio of the capacity of the first negative electrode sheet 11 facing the first positive electrode sheet to the capacity of the first positive electrode sheet 10 facing the first negative electrode sheet 11 .

[0094] In some examples, the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is 1.01 to 1.25. Exemplarily, the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 can be 1.01, 1.1, 1.2 or 1.25, etc., which is not limited here. In this way, when the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is less than 1.01, the first negative electrode sheet 11 has a high degree of lithium insertion. As the cycle progresses, when the lithium insertion site is lost, the cycle expansion is serious and the cycle life is affected; when the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is greater than 1.25, the first negative electrode sheet 11 has a low degree of lithium insertion, but it will increase the degree of lithium removal of the positive electrode, causing the positive electrode structure to collapse, and then causing the lithium-ion battery to fail. When the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is 1.01-1.25, the first core stack 100 has a small cycle expansion and a long cycle life, and will not increase the degree of lithium desorption of the positive electrode.

[0095] In one possible implementation, see Figure 4 and Figure 5 As shown, a lithium supplement layer 11c is provided on the surface of the first negative electrode active material layer 11b of the first negative electrode sheet 11 away from the first negative electrode current collector 11a. In this way, the first negative electrode sheet 11 can be supplemented with lithium, thereby improving the first efficiency of the first stacked core 100 and increasing the mass energy density of the first stacked core 100. The mass energy density of the first stacked core 100 can also be made greater than the mass energy density of the second stacked core 200, so that the first stacked core 100 of the lithium-ion battery has a high mass energy density.

[0096] The material of the lithium replenishing layer 11c may include but is not limited to lithium strips, lithium sheets, lithium powder or other lithium-containing materials.

[0097] The lithium replenishing layer 11 c includes metal segments 111 spaced apart from each other.

[0098] The region where the first negative electrode active material layer 11b of the first negative electrode sheet 11 is not covered by the lithium replenishing layer 11c is the first region. The region where the first negative electrode active material layer 11b of the first negative electrode sheet 11 is covered by the lithium replenishing layer 11c is the second region.

[0099] The area of ​​the second region is equal to the projection area of ​​the lithium replenishing layer 11 c in the thickness direction of the laminated battery cell.

[0100] The difference between the projected area of ​​the first negative electrode active material layer 11 b in the thickness direction of the laminated battery cell and the area of ​​the second region is the area of ​​the first region.

[0101] The ratio of the area of ​​the first region to the area of ​​the second region may be 0.2 to 5. In an optional embodiment, the ratio of the area of ​​the first region to the area of ​​the second region may be 0.9 to 1.1. For example, the ratio of the area of ​​the first region to the area of ​​the second region may be 1. In this way, the area of ​​the second region refers to the area covered with metallic lithium. When the ratio is less than 0.2, the area of ​​the second region is too large, the energy density of the first stacked core 100 is high, and the metallic lithium in the second region will produce byproducts, which will affect the transmission capacity of lithium ions and thus lead to deterioration of the cycle life; when the ratio is greater than 5, the cycle life of the first stacked core 100 is more seriously deteriorated (compared with the ratio of 0.2 to 5). Relative to the ratio less than 0.2, when the ratio is 0.2 to 5, the energy density of the first stacked core 100 is relatively low, and there are fewer byproducts in the second region, which reduces the deterioration of the cycle life. Relative to the ratio greater than 5, when the ratio is 0.2 to 5, the cycle life is reduced.

[0102] In a possible implementation, the first negative electrode current collector 11a of the first negative electrode sheet 11 is a composite current collector. The composite current collector may include a polymer layer and two metal layers located on opposite sides of the polymer layer, specifically, the two metal layers are located on both sides of the polymer layer in the thickness direction of the laminated battery core. The material of the polymer layer includes polyethylene terephthalate, polyethylene or polypropylene.

[0103] In some examples, the density of the composite current collector is less than the density of the copper foil. Compared with the copper foil, the first negative electrode current collector 11a of the first negative electrode sheet 11 adopts the composite current collector, which can reduce the mass of the first negative electrode sheet 11, thereby reducing the mass of the first stacked core 100, and further when the discharge energy remains unchanged, the mass energy density of the first stacked core 100 can be increased, so that the first stacked core 100 can be used as a part of the high mass energy density of the lithium-ion battery.

[0104] The thickness of the polymer layer in the thickness direction of the laminated battery core is 1 to 20 μm. For example, the thickness is 1 μm, 5 μm, 10 μm, 15 μm or 20 μm, etc., without specific limitation. The ductility of the polymer layer makes the first negative electrode sheet 11 less likely to break, which can improve the mechanical strength of the first laminated core 100 of the lithium-ion battery.

[0105] The metal layer may be an aluminum layer or a copper layer. The thickness of the two metal layers in the thickness direction of the laminated battery core is 0.3 to 5 μm. For example, the thickness is 0.3 μm, 1 μm, 3 μm or 5 μm, etc. There is no specific limitation.

[0106] The tensile strength of the first negative electrode sheet 11 may be greater than or equal to 100 MPa. This arrangement can improve the mechanical strength of the first stacked core 100 of the lithium-ion battery and reduce the risk of breakage during manufacturing, assembly and use.

[0107] The second positive electrode sheet 20 includes a second positive electrode current collector 20 a and a second positive electrode active material layer 20 b located on at least one side of the surface of the second positive electrode current collector 20 a .

[0108] The second negative electrode sheet 21 includes a second negative electrode collector 21a and a second negative electrode active material layer 21b. The second negative electrode active material layer 21b is arranged on at least one side of the second negative electrode collector 21a in the thickness direction, that is, the second negative electrode active material layer 21b is arranged on at least one side of the surface of the second negative electrode collector 21a.

[0109] In the thickness direction of the laminated battery core, when the outermost electrode sheet of the second laminated core 200 is the second positive electrode sheet 20, only one side of the surface of the second positive electrode collector 20a of the second positive electrode sheet 20 is provided with the second positive electrode active material layer 20b, and the second positive electrode active material layers 20b are respectively provided on both sides of the surface of the second positive electrode collector 20a of the remaining second positive electrode sheets 20 of the second laminated core 200, and the second negative electrode active material layers 21b are respectively provided on both sides of the surface of the second negative electrode collector 21a of each second negative electrode sheet 21 of the second laminated core 200.

[0110] In the thickness direction of the laminated battery cell, when the outermost electrode sheet of the second laminated core 200 is the second negative electrode sheet 21, only one side of the surface of the second negative electrode collector 21a of the second negative electrode sheet 21 is provided with the second negative electrode active material layer 21b, and the second negative electrode active material layers 21b are respectively provided on both sides of the surface of the second negative electrode collector 21a of the remaining second negative electrode sheets 21 of the second laminated core 200, and the second positive electrode active material layers 20b are respectively provided on both sides of the surface of the second positive electrode collector 20a of each second positive electrode sheet 20 of the second laminated core 200.

[0111] For example, see Figure 6 As shown, the second positive electrode sheet 20 includes a second positive electrode current collector 20a and two second positive electrode active material layers 20b located on the second positive electrode current collector 20a. Aluminum foil, copper foil or a composite current collector can be used as the second positive electrode current collector 20a.

[0112] The two second positive electrode active material layers 20 b are disposed on opposite sides of the second positive electrode current collector 20 a in the thickness direction, that is, one second positive electrode active material layer 20 b is disposed on each side of the second positive electrode current collector 20 a in the thickness direction.

[0113] The thickness of each second positive electrode active material layer 20 b of the second core stack 200 may be the same.

[0114] The material of the second positive electrode active material layer 20 b may be the same as that of the first positive electrode active material layer 10 b .

[0115] The gram capacity of the second positive electrode active material layer 20 b may be equal to the gram capacity of the first positive electrode active material layer 10 b .

[0116] As the second negative electrode current collector 21 a , an aluminum foil, a copper foil, or a composite current collector may be used.

[0117] The outermost electrode sheet of the second stacked core 200 in the thickness direction of the stacked core is the second negative electrode sheet 21, and the second negative electrode sheet 21 is provided with a second negative electrode active material layer 21b. Figure 7 As shown, the remaining second negative electrode sheet 21 is provided with two layers of second negative electrode active material layer 21b, and the two layers of second negative electrode active material layer 21b are arranged at two opposite layers in the thickness direction of the second negative electrode collector 21a, that is, one layer of second negative electrode active material layer 21b is respectively arranged on both sides of the thickness direction of the second negative electrode collector 21a.

[0118] The thickness of each second negative electrode active material layer 21 b of the second core stack 200 is the same.

[0119] The second negative electrode active material layer 21 b includes a second negative electrode active material, which includes at least one of first graphite, hard carbon, silicon-oxygen material, and silicon-carbon.

[0120] The second negative electrode active material may be the same as the first negative electrode active material, or may be the same as the first negative electrode active material.

[0121] The N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is the ratio of the capacity of the side of the second negative electrode sheet 21 facing the second positive electrode sheet 20 to the capacity of the side of the second positive electrode sheet 20 facing the second negative electrode sheet 21 .

[0122] In some examples, the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is 1.01-1.25.

[0123] Exemplarily, the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 can be 1.01, 1.1, 1.2 or 1.25, etc., which is not limited here. In this way, when the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is less than 1.01, the second negative electrode sheet 21 has a high degree of lithium insertion. As the cycle progresses, when the lithium insertion site is lost, the cycle expansion is serious and the cycle life is affected; when the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is greater than 1.25, the second negative electrode sheet 21 has a low degree of lithium insertion, but it will increase the degree of lithium removal of the positive electrode, causing the positive electrode structure to collapse, and then cause the lithium-ion battery to fail. When the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is 1.01 to 1.25, the second stacked core 200 has a small cycle expansion and a long cycle life, and will not increase the degree of lithium removal of the positive electrode.

[0124] Among them, the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is greater than the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20, so that the mass of the first positive electrode active material layer 10b of the first positive electrode sheet 10 can be greater than the mass of the second positive electrode active material layer 20b of the second positive electrode sheet 20, so that the mass energy density of the first core stack 100 can be greater than the mass energy density of the second core stack 200, and thus the first core stack 100 has a high mass energy density.

[0125] In some examples, the area of ​​the first positive current collector 10a facing the first positive active material layer 10b is equal to the area of ​​the second positive current collector 20a facing the second positive active material layer 20b, and the surface density of the first positive active material layer 10b of the first positive electrode sheet 10 is greater than the surface density of the second positive active material layer 20b of the second positive electrode sheet 20, so that the mass of the first positive active material layer 10b of the first positive electrode sheet 10 is greater than the mass of the second positive active material layer 20b of the second positive electrode sheet 20, and the thickness of the first positive active material layer 10b is greater than the thickness of the second positive active material layer 20b.

[0126] The surface density of the first positive electrode active material layer 10 b of the first positive electrode sheet 10 may be 5 to 40 mg / cm 2 .

[0127] For example, the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 may be 5 mg / cm 2 、10mg / cm 2 、15mg / cm 2 , 20mg / cm 2 , 25mg / cm 2 、30mg / cm 2 、35mg / cm 2 or 40mg / cm 2 In this way, when the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is less than 5 mg / cm 2 When the energy density is too low, it is not conducive to improving the battery life of the lithium-ion battery; when the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is greater than 40 mg / cm 2 When the energy density of the electrode is high (relative to 5-40 mg / cm 2 If the electrode sheet is too thick, the polarization of the lithium-ion battery will be large, resulting in a deterioration of the cycle life. When the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is 5 to 40 mg / cm 2 When used in conjunction with a lithium-ion battery, the battery life can be improved and the deterioration of the cycle life can be reduced.

[0128] The surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 may be 5 to 40 mg / cm 2 .

[0129] For example, the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 may be 5 mg / cm 2 、10mg / cm 2 、15mg / cm 2 , 20mg / cm 2 , 25mg / cm 2 、30mg / cm 2 、35mg / cm 2 or 40mg / cm 2 In this way, when the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 is less than 5 mg / cm 2 When the energy density is too low, it is not conducive to improving the battery life of the lithium-ion battery; when the surface density of the second positive active material layer 20b of the second positive electrode sheet 20 is greater than 40 mg / cm 2 When the energy density of the electrode is high (relative to 5-40 mg / cm 2 If the electrode sheet is too thick, the polarization of the lithium-ion battery will be large, resulting in a deterioration of the cycle life. When the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 is 5 to 40 mg / cm 2 When used in conjunction with a lithium-ion battery, the battery life can be improved and the deterioration of the cycle life can be reduced.

[0130] In the embodiment of the present application, it is sufficient that the mass energy density of the first core stack 100 is greater than the mass energy density of the second core stack 200. Exemplarily, the N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is equal to the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20.

[0131] The second positive active material layer 20b of the second positive electrode sheet 20 and / or the second negative active material layer 21b of the second negative electrode sheet 21 are provided with a recessed portion 20c. The recessed portion 20c can improve the wettability of the electrolyte to the material of the active material layer of the second stacked core 200, and can improve the utilization rate of the active material layer of the second stacked core 200, so that the second stacked core 200 has a fast charging performance. By making the surface density of the first positive active material layer 10b of the first positive electrode sheet 10 greater than the surface density of the second positive active material layer 20b of the second positive electrode sheet 20, the first stacked core 100 can have a high mass energy density, so that the battery cell of the lithium-ion battery can have both high mass energy density and fast charging performance.

[0132] The recessed portion 20c can be formed by laser.

[0133] See also Figure 7 and Figure 8 As shown, the second negative electrode active material layer 21b may be provided with a recessed portion 20c. In other embodiments, the second positive electrode active material layer 20b may be provided with a recessed portion 20c, or both the second positive electrode active material layer 20b and the second negative electrode active material layer 21b may be provided with a recessed portion 20c.

[0134] In one possible implementation, see Figure 7 and Figure 8 As shown, the recessed portion 20c includes a plurality of circular holes spaced apart from each other.

[0135] The diameter of the circular hole may be 20 to 2000 μm. For example, the diameter of the circular hole is 20 μm, 50 μm, 100 μm, 500 μm, 1000 μm, 1500 μm or 2000 μm, etc., without specific limitation.

[0136] The distance L between the centers of two adjacent circular holes may be 0.5 to 5 mm. For example, the distance L is 0.5 mm, 1 mm, 3 mm or 5 mm, etc., without specific limitation.

[0137] In the thickness direction of the laminated battery cell, the depth of the circular hole may be less than the thickness of the second negative electrode active material layer 21 b , that is, the circular hole does not penetrate the second negative electrode active material layer 21 b .

[0138] The depth of the circular hole is 3 to 70 μm. Exemplarily, the depth of the circular hole can be 3 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm, etc., which is not limited here. In this way, when the depth of the circular hole is less than 3 μm, the improvement of the negative electrode sheet dynamics is not obvious; when the depth of the circular hole is greater than 70 μm, the thickness of the single side of the electrode sheet is required to be greater than 70 μm, which is not conducive to the improvement of the cycle life. When the depth of the circular hole is 3 to 70 μm, it is beneficial to improve the negative electrode sheet dynamics and the cycle life.

[0139] In other embodiments, in the thickness direction of the laminated battery cell, the depth of the circular hole may be equal to the thickness of the second negative electrode active material layer 21b, or may be greater than the sum of the thickness of the second negative electrode active material layer 21b and the thickness of the second negative electrode current collector 21a.

[0140] In another possible implementation, see Fig. 9 As shown, the recessed portion 20c may include a plurality of mutually spaced grooves, which penetrate the second negative electrode active material layer 21b in the width direction of the laminated battery core.

[0141] The spacing between two adjacent grooves may be 0.5-5 mm. For example, the spacing is 0.5 mm, 1 mm, 3 mm or 5 mm, etc., without specific limitation.

[0142] In the thickness direction of the laminated battery cell, the depth of the groove may be less than the thickness of the second negative electrode active material layer 21 b , that is, the groove does not penetrate the second negative electrode active material layer 21 b .

[0143] The depth of the groove is 3 to 70 μm. Exemplarily, the depth of the groove can be 3 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm, etc., which is not limited here. In this way, when the depth of the groove is less than 3 μm, the improvement of the negative electrode sheet dynamics is not obvious; when the depth of the groove is greater than 70 μm, the thickness of the single side of the electrode sheet is required to be greater than 70 μm, which is not conducive to the improvement of the cycle life. When the depth of the groove is 3 to 70 μm, it is beneficial to improve the negative electrode sheet dynamics and the cycle life.

[0144] The laminated battery cell provided in the embodiment of the present invention has high mass energy density through the first laminated core 100 and fast charging performance through the second laminated core 200, so that the battery cell of the lithium-ion battery can have both high mass energy density and fast charging performance.

[0145] In some examples, the material of the second negative electrode active material layer 21 b includes a second graphite, and the second graphite includes a fast-charging graphite. This configuration can improve the fast-charging performance of the second stacked core 200 .

[0146] The particle size of the first graphite in the first negative electrode active material layer 11 b is larger than the particle size of the second graphite in the second negative electrode active material layer 21 b .

[0147] In some examples, the first graphite has a median particle size (D50) that is greater than the median particle size (D50) of the second graphite.

[0148] The median particle size (D50) of the first graphite is 2 to 40 μm. For example, the median particle size (D50) of the first graphite may be 2 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., which is not limited here.

[0149] The median particle size (D50) of the second graphite is 1 to 30 μm. For example, the median particle size (D50) of the second graphite may be 2 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., which is not limited here.

[0150] The compaction density of the first graphite is greater than the compaction density of the second graphite. In this way, the first graphite can store more lithium ions, thereby increasing the capacity of the first stacked core 100 and enabling the first stacked core 100 to have high mass energy density.

[0151] In a possible implementation, the first negative electrode active material includes a first silicon-based material. The first silicon-based material includes at least one of a silicon-oxygen material and silicon-carbon.

[0152] The second negative electrode active material includes a second silicon-based material, which includes at least one of a silicon-oxygen material and silicon-carbon.

[0153] The content of the first silicon-based material in the first negative electrode active material layer 11b of the first negative electrode sheet 11 is greater than the content of the second silicon-based material in the second negative electrode active material layer 21b of the second negative electrode sheet 21. In this way, the gram capacity of the first negative electrode active material layer 11b can be greater than the gram capacity of the second negative electrode active material layer 21b, so that the capacity of the first negative electrode sheet 11 is greater than the capacity of the second negative electrode sheet 21, which helps to improve the mass energy density of the first stacked core 100, and further enables the first stacked core 100 of the lithium-ion battery to have a high mass energy density.

[0154] In some examples, the first silicon-based material content in the first negative active material layer 11b of the first negative electrode sheet 11 is 5-50wt%, for example, 5wt%, 8wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%.

[0155] In some examples, the second silicon-based material content in the second negative active material layer 21b of the second negative electrode sheet 21 is 0-40wt%, for example, 0wt%, 0.1wt%, 1wt%, 5wt%, 8wt%, 10wt%, 20wt%, 30wt%, 40wt%.

[0156] Preferably, in some examples, the content of the second silicon-based material in the second negative electrode active material layer 21 b of the second negative electrode sheet 21 is 0-10 wt %.

[0157] In one possible implementation, see Figure 2 As shown, in the thickness direction of the laminated battery core, a third positive electrode sheet 30 is arranged between the innermost first diaphragm and the second diaphragm of the laminated battery core. In this way, the third positive electrode sheet 30 is arranged between the innermost first diaphragm and the second diaphragm, so that the electrode sheets of the laminated battery core can be ensured to be the first negative electrode sheet 11 and the second negative electrode sheet 21. The first negative electrode sheet 11 has a low material cost relative to the first positive electrode sheet 10 and the third positive electrode sheet 30, respectively. The second negative electrode sheet 21 has a low material cost relative to the second positive electrode sheet 20 and the third positive electrode sheet 30, respectively, thereby reducing the production cost of the lithium-ion battery.

[0158] In the thickness direction of the laminated battery core, the innermost side of the laminated battery core refers to the position of the third positive electrode sheet 30 and the first and second separators in contact with the third positive electrode sheet 30 in the laminated battery core.

[0159] See also Fig.10 As shown, the third positive electrode sheet 30 includes a third positive electrode current collector 30a and two third positive electrode active material layers 30b located on the third positive electrode current collector 30a. Aluminum foil, copper foil or a composite current collector can be used as the third positive electrode current collector 30a.

[0160] The material of the third positive electrode active material layer 30 b may be the same as that of the first positive electrode active material layer 10 b .

[0161] The gram capacity of the third positive electrode active material layer 30 b may be equal to the gram capacity of the first positive electrode active material layer 10 b .

[0162] It should be noted that the third positive electrode sheet 30 is provided with a third positive electrode active material layer 30 b on both sides of the third positive electrode sheet 30 in the thickness direction of the laminated battery core.

[0163] The first core stack 100 includes a third positive electrode active material layer 30 b on a side of the third positive electrode sheet 30 facing the first core stack 100 .

[0164] The second core stack 200 includes a third positive electrode active material layer 30 b on a side of the third positive electrode sheet 30 facing the second core stack 200 .

[0165] The surface density of the third positive electrode active material layer 30b of the third positive electrode sheet 30 facing the first core stack 100 is greater than the surface density of the third positive electrode active material layer 30b of the third positive electrode sheet 30 facing the second core stack 200, so that the mass of the third positive electrode active material layer 30b of the third positive electrode sheet 30 facing the first core stack 100 can be greater than the mass of the third positive electrode active material layer 30b of the third positive electrode sheet 30 facing the second core stack 200, thereby making the mass energy density of the first core stack 100 greater than the mass energy density of the second core stack 200, and further making the first core stack 100 have a high mass energy density.

[0166] The third positive active material layer 30b of the third positive electrode sheet 30 facing the second stacked core 200 is provided with a recessed portion 20c. In this way, the fast charging performance of the second stacked core 200 can be improved.

[0167] In some examples, the area of ​​the third positive electrode sheet 30 facing the first core stack 100 is equal to the area of ​​the third positive electrode sheet 30 facing the second core stack 200, and the surface density of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the first core stack 100 is greater than the surface density of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the second core stack 200, so that the mass of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the first core stack 100 is greater than the mass of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the second core stack 200, and the thickness of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the first core stack 100 is greater than the thickness of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the second core stack 200.

[0168] The N / P ratio of the first negative electrode sheet 11 to the third positive electrode sheet 30 is the ratio of the capacity of the first negative electrode sheet 11 facing the third positive electrode sheet 30 to the capacity of the third positive electrode sheet 30 facing the first negative electrode sheet 11 .

[0169] The N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 is 1.01 to 1.25. Exemplarily, the N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 can be 1.01, 1.1, 1.2 or 1.25, etc., which is not limited here. In this way, when the N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 is less than 1.01, the first negative electrode sheet 11 has a high degree of lithium insertion. As the cycle progresses, when the lithium insertion site is lost, the cycle expansion is serious and the cycle life is affected; when the N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 is greater than 1.25, the first negative electrode sheet 11 has a low degree of lithium insertion, but it will increase the degree of lithium removal of the positive electrode, causing the positive electrode structure to collapse, and then causing the lithium-ion battery to fail. When the N / P ratio of the first negative electrode sheet 11 to the third positive electrode sheet 30 is 1.01-1.25, the first core stack 100 has a small cycle expansion and a long cycle life, and will not increase the degree of lithium desorption of the positive electrode.

[0170] The N / P ratio of the second negative electrode sheet 21 to the third positive electrode sheet 30 is the ratio of the capacity of the side of the second negative electrode sheet 21 facing the second positive electrode sheet 20 to the capacity of the side of the third positive electrode sheet 30 facing the second negative electrode sheet 21 .

[0171] The N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 is 1.01 to 1.25. Exemplarily, the N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 can be 1.01, 1.1, 1.2 or 1.25, etc., which is not limited here. In this way, when the N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 is less than 1.01, the second negative electrode sheet 21 has a high degree of lithium insertion. As the cycle progresses, when the lithium insertion site is lost, the cycle expansion is serious and the cycle life is affected; when the N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 is greater than 1.25, the second negative electrode sheet 21 has a low degree of lithium insertion, but it will increase the degree of lithium removal of the positive electrode, causing the positive electrode structure to collapse, and then causing the lithium-ion battery to fail. When the N / P ratio of the second negative electrode sheet 21 to the third positive electrode sheet 30 is 1.01-1.25, the second stacked core 200 has a small cycle expansion and a long cycle life, and will not increase the degree of lithium desorption of the positive electrode.

[0172] Furthermore, the N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 may be the same as or different from the N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30, as long as the mass energy density between the first negative electrode sheet 11 and the third positive electrode sheet 30 is greater than the mass energy density between the second negative electrode sheet 21 and the third positive electrode sheet 30.

[0173] In some examples, the difference between the N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 and the N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 is -0.5 to 0.5. Exemplarily, the difference may be -0.5, 1 or 0.5, without specific limitation. In this way, the first stack 100 and the second stack 200 have small cycle expansion and long cycle life, and will not increase the degree of lithium desorption of the positive electrode.

[0174] Exemplarily, the N / P ratio of the first negative electrode sheet 11 to the third positive electrode sheet 30 is 1.1, and the N / P ratio of the second negative electrode sheet 21 to the third positive electrode sheet 30 is 1.12.

[0175] In one possible implementation, see Figure 1 As shown, the first stacked core 100 is connected with a first positive electrode tab 301 and a first negative electrode tab 302 .

[0176] The second core stack 200 is connected to a second positive electrode tab 401 and a second negative electrode tab 402 .

[0177] The first positive electrode tab 301 and the second positive electrode tab 401 may be connected or not connected. In some examples, the first positive electrode tab 301 and the second positive electrode tab 401 are electrically connected. Specifically, the first positive electrode tab 301 and the second positive electrode tab 401 are connected by a wire.

[0178] The lithium-ion battery is equipped with a battery management system. A switch is provided between the first positive electrode ear 301 and the first stacked core 100 and between the first negative electrode ear 302 and the first stacked core 100. When the lithium-ion battery is charged at a 3C rate, the switch is disconnected by the battery management system, so that part of the first stacked core 100 cannot be charged, that is, the first stacked core 100 is partially disconnected.

[0179] Exemplarily, when the lithium-ion battery is charged at a rate less than 1C, both the first core stack 100 and the second core stack 200 are charged.

[0180] When the lithium-ion battery is charged at a 3C rate, the battery management system partially disconnects the first core stack 100 and charges the second core stack 200. It can be understood that when the lithium-ion battery is charged at a 3C rate, only the second core stack 200 is charged.

[0181] Furthermore, in the length direction of the laminated battery core, the first positive electrode ear 301 and the second positive electrode ear 401 are located on the same side of the laminated battery core, and the first negative electrode ear 302 and the second negative electrode ear 402 are located on the same side of the laminated battery core. This arrangement facilitates the lamination of the laminated battery core.

[0182] The first positive electrode tab 301 and the second positive electrode tab 401 are located on one side of the laminated battery cell in the -X axis direction.

[0183] The first negative electrode tab 302 and the second negative electrode tab 402 are located on one side of the laminated battery cell in the +X axis direction.

[0184] In another possible implementation, see Fig.12 As shown, the first core stack 100 is provided with a first positive electrode ear 301, the second core stack is provided with a second positive electrode ear 401, and the first negative electrode ear of the first core stack 100 and the second negative electrode ear of the second core stack are connected to form a third negative electrode ear 500. It can be understood that the first core stack 100 and the second core stack 200 share the third negative electrode ear 500.

[0185] The first positive electrode tab 301 and the second positive electrode tab 401 may be connected or not connected. In some examples, the first positive electrode tab 301 and the second positive electrode tab 401 are electrically connected. Specifically, the first positive electrode tab 301 and the second positive electrode tab 401 are connected by a wire.

[0186] The lithium-ion battery is equipped with a battery management system.

[0187] Exemplarily, when the lithium-ion battery is charged at a rate less than 1C, both the first core stack 100 and the second core stack 200 are charged.

[0188] When the lithium-ion battery is charged at a 3C rate, the battery management system partially disconnects the first core stack 100 and charges the second core stack 200. It can be understood that when the lithium-ion battery is charged at a 3C rate, only the second core stack 200 is charged.

[0189] The embodiment of the present invention provides a lithium-ion battery, comprising a shell and a laminated battery core, wherein the laminated battery core is arranged in the shell.

[0190] Among them, the structure of the laminated battery cell in this embodiment is the same as that of the laminated battery cell provided in any of the above embodiments, and can bring the same or similar technical effects, which will not be described one by one here, and the details can be referred to the description of the above embodiments.

[0191] The lithium-ion battery of the present application is described in detail below through specific embodiments, and the specific differences of the lithium-ion batteries are shown below.

[0192] Example 1-1

[0193] The preparation of the lithium ion battery of this embodiment includes the following steps:

[0194] 1. Preparation of the first positive electrode sheet 10, the second positive electrode sheet 20 and the third positive electrode sheet 30

[0195] Lithium cobalt oxide, polyvinylidene fluoride, carbon black, and carbon tubes are added to N-methylpyrrolidone at a mass ratio of 97.5:1.5:0.5:0.5, and a positive electrode slurry is obtained by dispersion. The positive electrode slurry is coated on aluminum foil, and then rolled, cut, etc. to obtain a first positive electrode sheet 10.

[0196] The current collector of the first positive electrode sheet 10 is aluminum foil.

[0197] The surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 can be 25 mg / cm 2 .

[0198] The thickness of the first positive electrode active material layer 10 b may be 73.5 μm.

[0199] The ternary material, polyvinylidene fluoride, carbon black and carbon tube are added to N-methylpyrrolidone at a mass ratio of 97.5:1.5:0.5:0.5, and a positive electrode slurry is obtained after dispersion. The positive electrode slurry is coated on aluminum foil, and then rolled, cut and the like to obtain a second positive electrode sheet 20.

[0200] The current collector of the second positive electrode sheet 20 is aluminum foil.

[0201] The surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 can be 15 mg / cm 2 .

[0202] The thickness of the second positive electrode active material layer 20 b may be 44 μm.

[0203] Lithium cobalt oxide, polyvinylidene fluoride, carbon black and carbon tubes are added to N-methylpyrrolidone at a mass ratio of 97.5:1.5:0.5:0.5, and a positive electrode slurry is obtained by dispersion. The positive electrode slurry is coated on aluminum foil, and then rolled, cut and the like to obtain a third positive electrode sheet 30.

[0204] The current collector of the third positive electrode sheet 30 is aluminum foil.

[0205] The surface density of the third positive electrode active material layer 30 b on the side of the third positive electrode sheet 30 facing the first stack is 25 mg / cm 2 , with a thickness of 73.5 μm; the surface density of the third positive electrode active material layer 30 b on the side facing the second core stack is 15 mg / cm 2 , thickness is 44μm.

[0206] 2. Preparation of the first negative electrode sheet 11 and the second negative electrode sheet 21

[0207] Artificial graphite is used as the first graphite. The first graphite, styrene-butadiene rubber, lithium polyacrylate and carbon black are added into deionized water at a mass ratio of 98:1.0:0.5:0.5, and the negative electrode slurry is obtained by dispersion. The positive electrode slurry is coated on copper foil, and then the first negative electrode sheet 11 is obtained by rolling and slitting.

[0208] The median particle size (Dv50) of the first graphite was 16 μm.

[0209] The compacted density of the first graphite is 1.7g / cm 3 .

[0210] The current collector of the first negative electrode sheet 11 is copper foil.

[0211] The N / P ratio of the first negative electrode sheet 11 to the first positive electrode sheet 10 is 1.1.

[0212] The N / P ratio of the first negative electrode sheet 11 and the third positive electrode sheet 30 may be 1.1.

[0213] Artificial graphite is used as the second graphite, and the second graphite, styrene-butadiene rubber, lithium polyacrylate and carbon black are added into deionized water at a mass ratio of 98:1.0:0.5:0.5, and the negative electrode slurry is obtained by dispersion. The positive electrode slurry is coated on copper foil, and then rolled, cut, etc. to obtain the second negative electrode sheet 21.

[0214] The median particle size (Dv50) of the second graphite was 16 μm.

[0215] The compacted density of the first graphite is 1.7 g / cm 3 .

[0216] The current collector of the second negative electrode sheet 21 is copper foil.

[0217] The second negative electrode active material layer 21 b of the second negative electrode sheet 21 is provided with a plurality of circular holes spaced apart from each other. The diameter of the circular holes may be 50 μm, the distance between the centers of two adjacent circular holes is 1 mm, and the depth of the circular holes is 10 μm.

[0218] The N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is 1.1.

[0219] The N / P ratio of the second negative electrode sheet 21 and the third positive electrode sheet 30 is 1.1.

[0220] It should be noted that, in this embodiment, neither the first graphite nor the second graphite is fast-filling graphite. The median particle size (Dv50) of the first graphite is 16 μm. The median particle size (Dv50) of the second graphite is 16 μm.

[0221] 3. Diaphragm

[0222] 4. Assembly

[0223] The number of the first positive electrode sheets 10 and the number of the second positive electrode sheets 20 are both 10. The number of the first negative electrode sheets 11 and the number of the second negative electrode sheets 21 are both 10.

[0224] The first positive electrode sheets 10 and the first negative electrode sheets 11 are alternately stacked to form a first part.

[0225] The second positive electrode sheets 20 and the second negative electrode sheets 21 are alternately stacked to form a second part.

[0226] A third positive electrode sheet is stacked between the first part and the second part to form a first stacked core 100 and a second stacked core 200 .

[0227] The first core stack 100 is connected with a first positive electrode tab and a first negative electrode tab.

[0228] The second core stack 200 is connected to a second positive electrode tab and a second negative electrode tab.

[0229] The stacked cells are packaged, injected, formed and sorted to obtain lithium-ion batteries.

[0230] Example 1-2

[0231] The difference between Example 1-2 and Example 1-1 is that the second graphite is fast-filling graphite, and the median particle size (Dv50) of the fast-filling graphite is 10 μm.

[0232] The compacted density of fast-filled graphite is 1.55g / cm 3 .

[0233] Examples 1-3

[0234] The difference between Example 1-3 and Example 1-2 is that the first negative electrode active material layer material further includes a first silicon-based material. The first silicon-based material is silicon carbon. The first silicon-based material content in the first negative electrode active material layer 11b of the first negative electrode sheet 11 is 25wt%.

[0235] Examples 1-4

[0236] The difference between Example 1-4 and Example 1-2 is that the first negative electrode active material layer material is a first silicon-based material, but does not include the first graphite. The first silicon-based material is silicon carbon.

[0237] Examples 1-5

[0238] The difference between Example 1-5 and Example 1-3 is that the first negative electrode current collector 11a of the first negative electrode sheet 11 is a composite current collector. The composite current collector may include a polymer layer and two metal layers respectively located on opposite sides of the polymer layer. Specifically, the two metal layers are respectively located on both sides of the polymer layer in the thickness direction of the laminated battery core. The material of the polymer layer may be polypropylene. The thickness of the polymer layer in the thickness direction of the laminated battery core is 10 μm. The metal layer may be an aluminum layer. The thickness of the two metal layers in the thickness direction of the laminated battery core is 3 μm.

[0239] Examples 1-6

[0240] The difference between Example 1-6 and Example 1-3 is that a lithium supplement layer 11 c is provided on the surface of the first negative electrode active material layer 11 b of the first negative electrode sheet 11 .

[0241] Examples 1-7

[0242] The difference between Example 1-5 and Example 1-3 is that the N / P ratio of the second negative electrode sheet 21 to the second positive electrode sheet 20 is 1.12; the N / P ratio of the second negative electrode sheet 21 to the third positive electrode sheet 30 is 1.12.

[0243] Examples 1-8

[0244] The difference between Example 1-8 and Example 1-3 is that the second negative electrode active material layer 21 b of the second negative electrode sheet 21 is provided with a plurality of grooves spaced apart from each other.

[0245] Examples 1-9

[0246] The difference between Example 1-9 and Example 1-3 is that the median particle size (Dv50) of the first graphite is 40 μm.

[0247] Examples 1-10

[0248] The difference between Example 1-10 and Example 1-2 is that the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 can be 15 mg / cm 2 The thickness of the first positive electrode active material layer 10 b may be 44 μm.

[0249] The number of the first positive electrode sheets 10 and the number of the first negative electrode sheets 11 are both 15.

[0250] Embodiment 1-11

[0251] The difference between Example 1-11 and Example 1-3 is that the material of the first positive electrode active material layer 10 b includes lithium cobalt oxide, and does not include a ternary material.

[0252] Examples 1-12

[0253] The difference between Example 1-12 and Example 1-3 is that the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is 30 mg / cm 2 , thickness is 87.5μm.

[0254] Examples 1-13

[0255] The difference between Example 1-13 and Example 1-3 is that the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 is 35 mg / cm 2 , thickness is 102μm.

[0256] Examples 1-14

[0257] The difference between Example 1-14 and Example 1-3 is that the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 is 10 mg / cm 2 , thickness is 28.5μm.

[0258] Examples 1-15

[0259] The difference between Example 1-15 and Example 1-3 is that the surface density of the second positive electrode active material layer 20b of the second positive electrode sheet 20 is 20 mg / cm 2 , thickness is 58μm.

[0260] Comparative Example 1

[0261] The difference between Comparative Example 1 and Example 1-1 is that the surface density of the first positive electrode active material layer 10b of the first positive electrode sheet 10 can be 15 mg / cm 2 The thickness of the first positive electrode active material layer 10 b may be 44 μm.

[0262] The second negative electrode active material layer 21 b of the second negative electrode sheet 21 has no circular holes.

[0263] Comparative Example 2

[0264] The difference between Comparative Example 2 and Comparative Example 1 is that the second graphite is fast-filling graphite.

[0265] Table 1

[0266]

[0267]

[0268]

[0269]

[0270] Table 2

[0271]

[0272]

[0273]

[0274]

[0275] Table 3

[0276]

[0277]

[0278] Mass energy density: The mass energy density of lithium-ion batteries is WED = E / M, where E is the discharge energy of the battery. The test method is to charge the lithium-ion battery to the upper voltage limit at a current of 0.2C, then charge at a constant voltage until the current drops to 0.025C, and then discharge at a current of 0.2C to 2.75V. The discharged energy is E. M is the mass of the lithium-ion battery. The mass of the lithium-ion battery is obtained by measuring and weighing the finished lithium-ion battery. E / M is the mass energy density obtained by the test.

[0279] Charging time: The charging time described in this application is the time required to charge the battery from 0% SOC to 100% SOC. The test method is: at 25°C, charge the lithium-ion battery at a rate of 0.5C to the upper limit voltage, and then charge at a constant voltage until the current drops to 0.025C. The time T required for this process is recorded, which is the charging time of the battery.

[0280] Area density test: Cut or prepare a sample with a regular shape (such as a rectangle or circle); use a precision balance to measure the mass of the sample; use a measuring tool to measure the length and width of the sample, and calculate the area of ​​the sample; the mass of the sample / the area of ​​the sample is the area density obtained by the test.

[0281] Particle size (Dv50) test: disperse the sample to be tested in a liquid medium to ensure that the particles are fully dispersed and not agglomerated; start the laser particle size analyzer and calibrate the instrument; inject the dispersed sample into the sample cell; the laser beam passes through the sample cell and the particles scatter the laser beam; the detector collects the scattered light signal and obtains the particle size distribution through software analysis; calculate and output the particle size distribution data; find the Dv50 value on the particle size distribution curve.

[0282] By comparing Example 1-1 with Comparative Example 1, it can be seen that the surface density of the positive active material layer of the first positive electrode sheet is greater than the surface density of the positive active material layer of the second positive electrode sheet, so that the first stack has high quality energy density; the second negative active material layer is provided with holes, so that the second stack has fast charging performance.

[0283] By comparing Example 1-2 with Example 1-1, it can be seen that the second graphite is fast-charging graphite, which can improve the fast-charging performance of the second stacked core.

[0284] By comparing Example 1-3 with Example 1-2, it can be seen that the first negative electrode active material layer of the first negative electrode sheet is provided with silicon carbon, which can improve the mass energy density of the first stacked core.

[0285] By comparing Example 1-6 with Example 1-3, it can be seen that adding a lithium supplement layer to the first negative electrode active material layer can improve the mass energy density of the first stacked core.

[0286] By comparing Example 1-5 with Example 1-3, it can be seen that the first negative electrode current collector is a composite current collector, which can improve the mass energy density of the first stacked core.

[0287] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laminated battery cell, characterized in that: include: A first core stack (100), the first core stack (100) comprising a first positive electrode sheet (10), a first separator and a first negative electrode sheet (11), the first positive electrode sheet (10), the first separator and the first negative electrode sheet (11) being arranged in an alternating manner; The first positive electrode sheet (10) comprises a first positive electrode current collector (10a) and a first positive electrode active material layer (10b) located on at least one side of the surface of the first positive electrode current collector (10a); The first negative electrode sheet (11) comprises a first negative electrode current collector (11a) and a first negative electrode active material layer (11b), wherein the first negative electrode active material layer (11b) is arranged on at least one side of the first negative electrode current collector (11a) in a thickness direction, and the first negative electrode active material layer (11b) comprises a first negative electrode active material, and the first negative electrode active material comprises a first silicon-based material; A second core stack (200), wherein the second core stack (200) comprises a second positive electrode sheet (20), a second separator and a second negative electrode sheet (21), wherein the second positive electrode sheet (20), the second separator and the second negative electrode sheet (21) are alternately stacked; The second positive electrode sheet (20) comprises a second positive electrode current collector (20a) and a second positive electrode active material layer (20b) located on at least one side of the surface of the second positive electrode current collector (20a); The second negative electrode sheet (21) comprises a second negative electrode current collector (21a) and a second negative electrode active material layer (21b), wherein the second negative electrode active material layer (21b) is arranged on at least one side of the second negative electrode current collector (21a) in a thickness direction, and the second negative electrode active material layer (21b) comprises a second negative electrode active material, and the second negative electrode active material comprises a second silicon-based material; The first stacked core (100) is connected to a first positive electrode tab (301) and a first negative electrode tab (302), and the second stacked core (200) is connected to a second positive electrode tab (401) and a second negative electrode tab (402); The surface density of the first positive electrode active material layer (10b) of the first positive electrode sheet (10) is greater than the surface density of the second positive electrode active material layer (20b) of the second positive electrode sheet (20); and / or the content of the first silicon-based material in the first negative electrode active material layer (11b) of the first negative electrode sheet (11) is greater than the content of the second silicon-based material in the second negative electrode active material layer (21b) of the second negative electrode sheet (21).

2. The laminated battery cell according to claim 1, characterized in that: In the thickness direction of the laminated battery core, a third positive electrode sheet (30) is arranged between the first diaphragm and the second diaphragm at the innermost side of the laminated battery core, and the surface density of the positive electrode active material layer of the third positive electrode sheet (30) facing the first laminated core (100) is greater than the surface density of the positive electrode active material layer of the third positive electrode sheet (30) facing the second laminated core (200); And / or, the N / P ratio of the first negative electrode sheet (11) to the third positive electrode sheet (30) and the N / P ratio of the second negative electrode sheet (21) to the third positive electrode sheet (30) are both 1.01 to 1.25, and the difference between the N / P ratio of the first negative electrode sheet (11) to the third positive electrode sheet (30) and the N / P ratio of the second negative electrode sheet (21) to the third positive electrode sheet (30) is -0.5 to 0.

5.

3. The laminated battery cell according to claim 1, characterized in that: A lithium supplement layer (11c) is provided on a surface of the first negative electrode active material layer (11b) of the first negative electrode sheet (11) away from the first negative electrode current collector (11a); Preferably, the lithium replenishing layer (11c) comprises metal segments spaced apart from each other; Preferably, the area of ​​the negative electrode active material layer of the first negative electrode sheet (11) not covered by the lithium replenishing layer (11c) is the first area, and the area of ​​the negative electrode active material layer of the first negative electrode sheet (11) covered by the lithium replenishing layer (11c) is the second area, and the area ratio of the first area to the second area is 0.2 to 5.

4. The laminated battery cell according to claim 1, characterized in that: The composite current collector of the first negative electrode sheet (11) comprises a polymer layer and two metal layers respectively located on opposite sides of the polymer layer, the thickness of the two metal layers is 0.3 to 5 μm, and the thickness of the polymer layer is 1 to 20 μm; The material of the polymer layer includes polyethylene terephthalate, polyethylene or polypropylene; Preferably, the tensile strength of the first negative electrode sheet (11) is greater than or equal to 100 MPa.

5. The laminated battery cell according to claim 1, characterized in that: The second positive electrode active material layer (20b) of the second positive electrode sheet (20) and / or the second negative electrode active material layer (21b) of the second negative electrode sheet (21) are provided with a recessed portion (20c).

6. The laminated battery cell according to claim 5, characterized in that: The recessed portion (20c) is arranged on the second negative electrode active material layer (21b), and the recessed portion comprises a plurality of circular holes or grooves spaced apart from each other; Preferably, the distance between the centers of two adjacent circular holes is 0.5 to 5 mm, the diameter of the circular hole is 20 to 2000 μm, and the depth of the circular hole is 3 to 70 μm; or, in the thickness direction of the laminated battery core, the depth of the circular hole is greater than the sum of the thickness of the second negative electrode active material layer (21b) and the thickness of the second negative electrode current collector (21a); Preferably, the spacing between two adjacent grooves is 0.5 to 5 mm, and the depth of the groove is 3 to 70 μm; or, in the thickness direction of the laminated battery core, the depth of the groove is greater than the sum of the thickness of the second negative electrode active material layer (21b) and the thickness of the second negative electrode current collector (21a).

7. The laminated battery cell according to claim 1, characterized in that: The material of the first negative electrode active material layer (11b) of the first negative electrode sheet (11) includes first graphite, and the median particle size (Dv50) of the first graphite is 2 to 40 μm; The material of the second negative electrode active material layer (21b) of the second negative electrode sheet (21) includes second graphite, and the median particle size (Dv50) of the second graphite is 1 to 30 μm; The median particle size of the second graphite is smaller than the median particle size (Dv50) of the first graphite, and the compaction density of the first graphite is greater than the compaction density of the second graphite.

8. The laminated battery cell according to any one of claims 1 to 7, characterized in that: The first negative electrode tab (302) and the second negative electrode tab (402) are connected to form a third negative electrode tab (500).

9. The laminated battery cell according to claim 8, characterized in that: A switch is provided between the first positive electrode tab (301) and the first stacked core (100), and between the first negative electrode tab (302) and the first stacked core (100); In the length direction of the laminated battery core, the first positive electrode ear and the second positive electrode ear are located on the same side of the laminated battery core, and the first negative electrode ear and the second negative electrode ear are located on the same side of the laminated battery core; In the length direction of the laminated battery core, the first positive electrode tab and the first negative electrode tab are respectively located on both sides of the laminated battery core, and the second positive electrode tab and the second negative electrode tab are respectively located on both sides of the laminated battery core.

10. The laminated battery cell according to any one of claims 1 to 7, characterized in that: The surface density of the first positive electrode active material layer (10b) of the first positive electrode sheet (10) is 5 to 40 mg / cm 2 ; The surface density of the second positive electrode active material layer (20b) of the second positive electrode sheet (20) is 5 to 40 mg / cm 2 ; The first silicon-based material content in the first negative electrode active material layer (11b) of the first negative electrode sheet (11) is 5 to 50 wt %; the second silicon-based material content in the second negative electrode active material layer (21b) of the second negative electrode sheet (21) is 0 to 40 wt %.

11. A lithium ion battery, characterized in that: It comprises a shell and a laminated battery core as claimed in any one of claims 1 to 10, wherein the laminated battery core is arranged in the shell.

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