Laminated cells and lithium-ion batteries

Abstract

This invention provides a stacked battery cell and a lithium-ion battery, relating to the field of lithium-ion battery technology. The stacked battery cell includes a first stacked cell and a second stacked cell. The first stacked cell includes a first positive electrode (10), a first separator, and a first negative electrode, which are alternately stacked. The second stacked cell includes a second positive electrode, a second separator, and a second negative electrode, which are also alternately stacked. By using the first stacked cell as the high-energy-density component and the second stacked cell as the fast-charging component, the lithium-ion battery cell can achieve both high-energy-density and fast-charging performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a stacked cell and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, lack of memory effect, and long cycle life, have been widely used in new energy vehicles. However, range anxiety is a common problem in new energy vehicles.

[0003] In related technologies, range anxiety can be eliminated by increasing the driving range on a single charge, which means that the lithium-ion battery cells need to have high energy density to eliminate range anxiety; or range anxiety can be eliminated by shortening the charging time on a single charge, which means improving the fast charging performance of the lithium-ion battery cells to eliminate range anxiety.

[0004] However, lithium-ion battery cells have a trade-off between high energy density and fast charging performance. Summary of the Invention

[0005] This invention provides a stacked cell and a lithium-ion battery to solve the problem that lithium-ion battery cells cannot simultaneously achieve high energy density and fast charging performance.

[0006] On one hand, embodiments of the present invention provide a stacked battery cell, including

[0007] The first core stack includes a first positive electrode sheet, a first separator, and a first negative electrode sheet, which are stacked alternately.

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

[0009] The first negative electrode sheet includes a first negative electrode current collector and a first negative electrode active material layer. The first negative electrode active material layer is disposed on at least one side of the thickness direction of the first negative electrode current collector. The first negative electrode active material layer includes a first negative electrode active material, which includes a first silicon-based material.

[0010] The second core stack includes a second positive electrode sheet, a second separator, and a second negative electrode sheet, which are stacked alternately.

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

[0012] The second negative electrode sheet includes a second negative electrode current collector and a second negative electrode active material layer. The second negative electrode active material layer is disposed on at least one side of the thickness direction of the second negative electrode current collector. The second negative electrode active material layer includes a second negative electrode active material, which includes a second silicon-based material.

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

[0014] Wherein, the areal density of the first positive electrode active material layer of the first positive electrode sheet is greater than the areal 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 one possible implementation, in the thickness direction of the stacked cell, a third positive electrode is disposed between the first separator and the second separator on the innermost side of the stacked cell, and the surface density of the positive active material layer of the third positive electrode facing the first stacked cell is greater than the surface density of the positive active material layer of the third positive electrode facing the second stacked cell.

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

[0018] In one possible implementation, a lithium replenishment layer is provided on the surface of the first negative electrode active material layer away from the first negative electrode current collector.

[0019] Preferably, the lithium replenishment 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 replenishment layer is a first region, and the area of ​​the negative electrode active material layer of the first negative electrode sheet covered by the lithium replenishment layer is a second region, and the area ratio of the first region to the second region is 0.2 to 5.

[0021] In one 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, wherein 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 polymer layer is made of 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 one possible implementation, 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 recesses.

[0025] In one possible implementation, the recess is disposed on the second negative electrode active material layer, and the recess includes a plurality of spaced-apart circular holes or grooves.

[0026] Preferably, the distance between the centers of two adjacent circular holes is 0.5 to 5 mm, the diameter of the circular holes is 20 to 2000 μm, and the depth of the circular holes is 3 to 70 μm; or, in the thickness direction of the stacked cell, the depth of the circular holes 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 to 5 mm, and the depth of the groove is 3 to 70 μm; or, in the thickness direction of the stacked cell, 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 one 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 that of the first graphite (Dv50), and the compaction density of the first graphite is greater than that of the second graphite.

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

[0032] In one possible implementation, a switch is 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] Along the length of the laminated battery cell, the first positive tab and the second positive tab are located on the same side of the laminated battery cell, and the first negative tab and the second negative tab are located on the same side of the laminated battery cell.

[0034] Along the length of the laminated battery cell, the first positive tab and the first negative tab are located on both sides of the laminated battery cell, and the second positive tab and the second negative tab are located on both sides of the laminated battery cell.

[0035] In one possible implementation, the areal density of the first positive electrode active material layer of the first positive electrode sheet is 5–40 mg / cm³. 2 ;

[0036] The areal density of the second positive electrode active material layer of the second positive electrode sheet is 5–40 mg / cm³. 2 ;

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

[0038] On the other hand, embodiments of the present invention provide a lithium-ion battery, including a casing and a stacked cell as described above, wherein the stacked cell is disposed in the casing.

[0039] This invention provides a stacked cell and a lithium-ion battery. By having a higher surface density of the positive active material layer of the first positive electrode than that of the positive active material layer of the second positive electrode, the mass of the positive active material layer of the first positive electrode can be greater than that of the positive active material layer of the second positive electrode, thereby enabling the first stacked cell to have a high 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. This makes the specific capacity of the first negative electrode active material layer greater than the specific 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. This helps to improve the mass energy density of the first stacked core, and thus enables the first stacked core to have a high mass energy density.

[0041] By using the first stack of cells as the high-quality energy density component and the second stack of cells as the fast-charging component, lithium-ion battery cells can achieve both high-quality energy density and fast-charging performance. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0044] Figure 2 This is a schematic diagram of a stacked battery cell provided in Embodiment 1 of the present invention;

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

[0046] Figure 4 This is 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 top view of the first negative electrode plate in the process;

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

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

[0050] Figure 8 for Figure 7 A top view of the second negative electrode plate;

[0051] Figure 9 This is a top view schematic diagram of another second negative electrode sheet provided in Embodiment 1 of the present invention;

[0052] Figure 10 This is a cross-sectional schematic diagram of a third positive electrode sheet provided in Embodiment 1 of the present invention;

[0053] Figure 11 This is a schematic diagram of a lithium-ion battery provided in Embodiment 1 of the present invention;

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

[0055] Explanation of reference numerals in the attached figures:

[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-First negative electrode plate; 11a-First negative electrode current collector;

[0059] 11b - First negative electrode active material layer; 11c - Lithium replenishment layer;

[0060] 111 - Metal segment; 200 - Second core stack;

[0061] 20 - Second positive electrode plate; 20a - Second positive 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 - Recessed portion; 30 - Third positive electrode plate;

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

[0066] 301 - First positive electrode tab; 401 - Second positive electrode tab;

[0067] 302 - First negative electrode tab; 402 - Second negative electrode tab;

[0068] 500 - Third negative electrode. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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 construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0072] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0073] In the above description, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] In related technologies, range anxiety can be eliminated by increasing the driving range on a single charge, which requires lithium-ion battery cells to have high energy density; alternatively, range anxiety can be eliminated by shortening the charging time on a single charge, which means improving the fast-charging performance of lithium-ion battery cells. However, lithium-ion battery cells present a challenge in simultaneously achieving high energy density and fast-charging performance.

[0075] To address the aforementioned issues, this invention provides a stacked cell and a lithium-ion battery, which divides the stacked cell into two parts: one part possesses high energy density, and the other part possesses fast charging performance, thus enabling the lithium-ion battery cell to balance high energy density and fast charging performance.

[0076] The stacked cell and lithium-ion battery provided in the embodiments of the present invention will be described in detail below with reference to specific embodiments.

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

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

[0079] See Figure 2 As shown, the first stacked core 100 includes a first positive electrode 10, a first separator (not shown in the figure), and a first negative electrode 11. The first positive electrode 10, the first separator, and the first negative electrode 11 are stacked alternately in the thickness direction of the stacked core. The first separator is disposed between the first positive electrode 10 and the first negative electrode 11, and the first separator serves to isolate electrons.

[0080] The second stacked core 200 includes a second positive electrode 20, a second separator (not shown in the figure), and a second negative electrode 21. The second positive electrode 20, the second separator, and the second negative electrode 21 are stacked alternately in the thickness direction of the stacked core. The second separator is disposed between the second positive electrode 20 and the second negative electrode 21, and serves to isolate electrons.

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

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

[0083] In the thickness direction of the stacked cells, when the outermost electrode of the first stacked core 100 is the first positive electrode 10, the first positive current collector 10a of the first positive electrode 10 has a first positive active material layer 10b on only one side, the other first positive electrode 10s of the first positive current collector 10a have a first positive active material layer 10b on both sides, and each of the first negative electrode 11s of the first negative electrode 100 has a first negative active material layer 11b on both sides.

[0084] In the thickness direction of the stacked cell, when the outermost electrode of the first stacked cell 100 is the first negative electrode 11, the first negative electrode current collector 11a of the first negative electrode 11 has a first negative electrode active material layer 11b on only one side. The first negative electrode current collector 11a of the remaining first negative electrode 11s of the first stacked cell 100 has a first negative electrode active material layer 11b on both sides. The first positive electrode current collector 10a of each first positive electrode 10 of the first stacked cell 100 has a first positive electrode active material layer 10b on both sides.

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

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

[0087] The thickness of each of the first positive electrode active material layers 10b in the first core stack 100 can be the same.

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

[0089] Aluminum foil, copper foil, or composite current collectors can be used as the first negative electrode current collector 11a.

[0090] The outermost electrode of the first stacked core 100 in the thickness direction of the stacked cells is the first negative electrode 11. This first negative electrode 11 has a first negative electrode active material layer 11b disposed on one side of the first negative electrode current collector 11a in the thickness direction. (See also...) Figure 4 As shown, the remaining first negative electrode sheet 11 is provided with two layers of first negative electrode active material 11b. The two layers of first negative electrode active material 11b are provided on opposite sides of the thickness direction of the first negative electrode current collector 11a, that is, one layer of first negative electrode active material 11b is provided on each side of the thickness direction of the first negative electrode current collector 11a.

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

[0092] The first negative electrode active material layer 11b includes a first negative electrode active material. The first negative electrode active material 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 11 to the first positive electrode 10 is the ratio of the capacity of the side of the first negative electrode 11 facing the first positive electrode to the capacity of the side of the first positive electrode 10 facing the first negative electrode 11.

[0094] In some examples, the N / P ratio of the first negative electrode 11 to the first positive electrode 10 is 1.01 to 1.25. Exemplarily, the N / P ratio of the first negative electrode 11 to the first positive electrode 10 can be 1.01, 1.1, 1.2, or 1.25, etc., and is not limited to a single value. With this configuration, when the N / P ratio of the first negative electrode 11 to the first positive electrode 10 is less than 1.01, the first negative electrode 11 has a high degree of lithium insertion. As cycling progresses, the loss of lithium insertion sites leads to severe cycle expansion and affects cycle life. When the N / P ratio of the first negative electrode 11 to the first positive electrode 10 is greater than 1.25, the first negative electrode 11 has a low degree of lithium insertion, but this will increase the degree of delithiation of the positive electrode, causing the positive electrode structure to collapse, and ultimately leading to lithium-ion battery failure. When the N / P ratio of the first negative electrode 11 to the first positive electrode 10 is 1.01 to 1.25, the first stacked core 100 has small cyclic expansion and long cycle life, and will not promote an increase in the degree of delithiation of the positive electrode.

[0095] In one possible implementation, see Figure 4 and Figure 5 As shown, a lithium replenishment layer 11c is disposed on the surface of the first negative electrode active material layer 11b away from the first negative electrode current collector 11a. This arrangement allows for lithium replenishment of the first negative electrode 11, thereby improving the initial efficiency of the first stack 100 and increasing its mass energy density. It also allows the mass energy density of the first stack 100 to be greater than that of the second stack 200, thus enabling the first stack 100 of the lithium-ion battery to possess a high mass energy density.

[0096] The lithium replenishment layer 11c can be made of materials including but not limited to lithium strips, lithium sheets, lithium powder or other lithium-containing materials.

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

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

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

[0100] The difference between the projected area of ​​the first negative electrode active material layer 11b in the thickness direction of the laminated 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 can be 0.2 to 5. In an optional embodiment, the ratio can be 0.9 to 1.1. For example, the ratio can be 1. In this configuration, the area of ​​the second region refers to the region covered with lithium metal. When the ratio is less than 0.2, the second region is too large, resulting in a high energy density of the first core 100. The lithium metal present in the second region will generate byproducts, affecting the lithium-ion transport capacity and thus leading to a deterioration in cycle life. When the ratio is greater than 5, the cycle life of the first core 100 deteriorates significantly (compared to a ratio of 0.2 to 5). Compared to a ratio less than 0.2, when the ratio is 0.2 to 5, the energy density of the first core 100 is relatively low, and there are fewer byproducts in the second region, reducing cycle life deterioration. Compared to a ratio greater than 5, when the ratio is 0.2 to 5, cycle life deterioration is reduced.

[0102] In one possible implementation, the first negative electrode current collector 11a of the first negative electrode 11 is a composite current collector. This 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 opposite sides of the polymer layer in the thickness direction of the laminated cell. The polymer layer is made of polyethylene terephthalate, polyethylene, or polypropylene.

[0103] In some examples, the density of the composite current collector is less than that of the copper foil. Compared to the copper foil, the first negative electrode current collector 11a of the first negative electrode 11 uses a composite current collector, which can reduce the mass of the first negative electrode 11, thereby reducing the mass of the first stacked core 100. Consequently, when the discharge energy remains constant, the mass energy density of the first stacked core 100 can be increased, making the first stacked core 100 a high-mass energy density component of the lithium-ion battery.

[0104] The polymer layer has a thickness of 1 to 20 μm in the thickness direction of the stacked battery cell. For example, the thickness can be 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 11 less prone to breakage, thereby improving the mechanical strength of the first stacked core 100 of the lithium-ion battery.

[0105] The metal layers can be aluminum or copper. The thickness of the two metal layers in the thickness direction of the laminated cell is 0.3–5 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 11 can be greater than or equal to 100 MPa. This setting can improve the mechanical strength of the first stack 100 of the lithium-ion battery and reduce the risk of breakage during manufacturing, assembly and use.

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

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

[0109] In the thickness direction of the stacked cell, when the outermost electrode of the second stacked core 200 is the second positive electrode 20, the second positive current collector 20a of the second positive electrode 20 has a second positive active material layer 20b on only one side, and the other second positive electrode 20s of the second positive current collector 20a have a second positive active material layer 20b on both sides. The second negative electrode 21 of each second negative electrode 21 of the second stacked core 200 has a second negative active material layer 21b on both sides.

[0110] In the thickness direction of the stacked cell, when the outermost electrode of the second stacked core 200 is the second negative electrode 21, the second negative electrode current collector 21a of the second negative electrode 21 has a second negative electrode active material layer 21b on only one side, and the second negative electrode current collector 21a of the remaining second negative electrode 21s of the second stacked core 200 has a second negative electrode active material layer 21b on both sides. The second positive electrode current collector 20a of each second positive electrode 20 of the second stacked core 200 has a second positive electrode active material layer 20b on both sides.

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

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

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

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

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

[0116] Aluminum foil, copper foil, or composite current collectors can be used as the second negative electrode current collector 21a.

[0117] In the second stacked core 200, the outermost electrode in the thickness direction of the stacked cell is the second negative electrode 21, which has a second negative electrode active material layer 21b disposed thereon. (See also...) Figure 7 As shown, the remaining second negative electrode sheet 21 is provided with two layers of second negative electrode active material 21b. The two layers of second negative electrode active material 21b are provided on opposite sides of the thickness direction of the second negative electrode current collector 21a, that is, one layer of second negative electrode active material 21b is provided on each side of the thickness direction of the second negative electrode current collector 21a.

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

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

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

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

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

[0123] For example, the N / P ratio of the second negative electrode 21 to the second positive electrode 20 can be 1.01, 1.1, 1.2, or 1.25, etc., and is not limited to a single value. With this configuration, when the N / P ratio of the second negative electrode 21 to the second positive electrode 20 is less than 1.01, the second negative electrode 21 has a high degree of lithium insertion. As cycling progresses, the loss of lithium insertion sites leads to severe cycle expansion and affects cycle life. When the N / P ratio of the second negative electrode 21 to the second positive electrode 20 is greater than 1.25, the second negative electrode 21 has a low degree of lithium insertion, but it will increase the degree of lithium delithiation in the positive electrode, causing the positive electrode structure to collapse and ultimately leading to lithium-ion battery failure. When the N / P ratio of the second negative electrode 21 to the second positive electrode 20 is between 1.01 and 1.25, the second stack 200 experiences small cycle expansion, has a long cycle life, and does not increase the degree of lithium delithiation in the positive electrode.

[0124] In this case, the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is greater than the areal density of the second positive electrode active material layer 20b of the second positive electrode 20, which makes the mass of the first positive electrode active material layer 10b of the first positive electrode 10 greater than the mass of the second positive electrode active material layer 20b of the second positive electrode 20, thereby making the mass energy density of the first core 100 greater than the mass energy density of the second core 200, and thus enabling the first core 100 to have 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. The areal density of the first positive active material layer 10b of the first positive electrode 10 is greater than the areal density of the second positive active material layer 20b of the second positive electrode 20, thereby making the mass of the first positive active material layer 10b of the first positive electrode 10 greater than the mass of the second positive active material layer 20b of the second positive electrode 20, and the thickness of the first positive active material layer 10b greater than the thickness of the second positive active material layer 20b.

[0126] The areal density of the first positive electrode active material layer 10b of the first positive electrode plate 10 can be 5–40 mg / cm³. 2 .

[0127] For example, the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 can be 5 mg / cm³. 2 10mg / cm 2 15mg / cm 2 20mg / cm 2 25mg / cm 2 30mg / cm 2 35mg / cm 2 Or 40mg / cm 2 Etc. This is not a unique limitation. With this configuration, when the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is less than 5 mg / cm³... 2 When the energy density is too low, it is not conducive to improving the battery life of lithium-ion batteries; when the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is greater than 40 mg / cm³, it is not conducive to improving the battery life of lithium-ion batteries. 2 At that time, the electrode energy density was relatively high (relative to 5–40 mg / cm³). 2 In general, if the electrode is too thick, the polarization of the lithium-ion battery is large, leading to a deterioration in cycle life. When the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is 5–40 mg / cm³... 2 This can improve the battery life of lithium-ion batteries and reduce the degradation of cycle life.

[0128] The areal density of the second positive electrode active material layer 20b of the second positive electrode 20 can be 5–40 mg / cm³. 2 .

[0129] For example, the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 can be 5 mg / cm³. 2 10mg / cm 2 15mg / cm 2 20mg / cm 2 25mg / cm 2 30mg / cm 2 35mg / cm 2 Or 40mg / cm 2 Etc. This is not a unique limitation. With this configuration, when the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 is less than 5 mg / cm³... 2 When the energy density is too low, it is not conducive to improving the battery life of lithium-ion batteries; when the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 is greater than 40 mg / cm³, it is also not conducive to improving the battery life of lithium-ion batteries. 2 At that time, the electrode energy density was relatively high (relative to 5–40 mg / cm³). 2 (In other words), if the electrode is too thick, the polarization of the lithium-ion battery is large, leading to a deterioration in cycle life. When the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 is 5–40 mg / cm³... 2 This can improve the battery life of lithium-ion batteries and reduce the degradation of cycle life.

[0130] In this embodiment, the mass energy density of the first core stack 100 is greater than that of the second core stack 200. For example, the N / P ratio of the first negative electrode 11 to the first positive electrode 10 is equal to the N / P ratio of the second negative electrode 21 to the second positive electrode 20.

[0131] The second positive electrode active material layer 20b of the second positive electrode 20 and / or the second negative electrode active material layer 21b of the second negative electrode 21 are provided with recesses 20c. These recesses 20c can improve the wettability of the electrolyte to the active material layer of the second core 200, thereby increasing the utilization rate of the active material layer of the second core 200 and enabling the second core 200 to have fast-charging performance. Since the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is greater than the areal density of the second positive electrode active material layer 20b of the second positive electrode 20, the first core 100 can have a high energy density, thus enabling the lithium-ion battery cell to achieve both high energy density and fast-charging performance.

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

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

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

[0135] The diameter of the circular hole can be 20 to 2000 μm. For example, the diameter of the circular hole can be 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 can be 0.5 to 5 mm. For example, the distance L can be 0.5 mm, 1 mm, 3 mm or 5 mm, etc., without specific limitation.

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

[0138] The depth of the circular hole is 3–70 μm. For example, the depth can be 3 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm, etc., and is not limited to a single depth. With this setting, when the depth of the circular hole is less than 3 μm, the improvement in negative electrode kinetics is not significant; when the depth of the circular hole is greater than 70 μm, the single-sided thickness of the electrode must also be greater than 70 μm, which is detrimental to improving cycle life. When the depth of the circular hole is 3–70 μm, it is beneficial to improve both negative electrode kinetics and cycle life.

[0139] In other embodiments, in the thickness direction of the stacked cell, the depth of the circular hole can be equal to the thickness of the second negative electrode active material layer 21b, or the depth of the circular hole can 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 Figure 9 As shown, the recess 20c may include a plurality of spaced grooves. The grooves penetrate the second negative electrode active material layer 21b in the width direction of the laminated cell.

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

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

[0143] The depth of the groove is 3–70 μm. For example, the groove depth can be 3 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm, etc., and is not limited to a single depth. With this setting, when the groove depth is less than 3 μm, the improvement in negative electrode dynamics is not significant; when the groove depth is greater than 70 μm, the single-sided thickness of the electrode must also be greater than 70 μm, which is detrimental to improving cycle life. A groove depth of 3–70 μm is beneficial for improving both negative electrode dynamics and cycle life.

[0144] The stacked cell provided in this embodiment of the invention has a high energy density in the first stack 100 and fast charging performance in the second stack 200, thereby enabling the lithium-ion battery cell to have both high energy density and fast charging performance.

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

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

[0147] In some examples, the median grain size (D50) of the first graphite is larger than that 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 can be 2 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., and is not limited to a single value.

[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 can be 2 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., and is not limited to a single value.

[0150] The compaction density of the first graphite is greater than that of the second graphite. This arrangement allows the first graphite to store more lithium ions, increasing the capacity of the first core 100 and enabling the first core 100 to possess high-quality energy density.

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

[0152] The second negative electrode active material includes a second silicon-based material. The second silicon-based material includes at least one of silicon-oxygen materials 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 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 21. This configuration allows the specific capacity of the first negative electrode active material layer 11b to be greater than that of the second negative electrode active material layer 21b, thereby increasing the capacity of the first negative electrode 11 compared to the second negative electrode 21. This helps to improve the mass energy density of the first stacked core 100, thus enabling the first stacked core 100 of the lithium-ion battery to possess a high mass energy density.

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

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

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

[0157] In one possible implementation, see Figure 2 As shown, in the thickness direction of the stacked battery cell, a third positive electrode 30 is disposed between the innermost first separator and the second separator. This arrangement, with the third positive electrode 30 disposed between the innermost first separator and the second separator, ensures that the electrodes of the stacked battery cell are a first negative electrode 11 and a second negative electrode 21. The first negative electrode 11 has a lower material cost compared to both the first positive electrode 10 and the third positive electrode 30. Similarly, the second negative electrode 21 has a lower material cost compared to both the second positive electrode 20 and the third positive electrode 30, thereby reducing the production cost of lithium-ion batteries.

[0158] In the thickness direction of the laminated cell, the innermost part of the laminated cell refers to the position of the third positive electrode 30 and the first and second separators that are in contact with the third positive electrode 30 in the laminated cell.

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

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

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

[0162] It should be noted that the third positive electrode 30 has a third positive electrode active material layer 30b on both sides of the stacked cell in the thickness direction.

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

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

[0165] The areal density of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the first core 100 is greater than the areal density of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the second core 200. This makes 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 100 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 200. As a result, the mass energy density of the first core 100 is greater than the mass energy density of the second core 200, thereby enabling the first core 100 to have a high mass energy density.

[0166] The third positive electrode plate 30 has a recessed portion 20c on the side of the third positive electrode active material layer 30b facing the second core 200. This configuration improves the fast charging performance of the second core 200.

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

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

[0169] The N / P ratio of the first negative electrode 11 to the third positive electrode 30 is 1.01 to 1.25. For example, the N / P ratio of the first negative electrode 11 to the third positive electrode 30 can be 1.01, 1.1, 1.2, or 1.25, etc., and is not limited to a single value. With this configuration, when the N / P ratio of the first negative electrode 11 to the third positive electrode 30 is less than 1.01, the first negative electrode 11 has a high degree of lithium insertion. As cycling progresses, the loss of lithium insertion sites leads to severe cycle expansion and affects cycle life. When the N / P ratio of the first negative electrode 11 to the third positive electrode 30 is greater than 1.25, the first negative electrode 11 has a low degree of lithium insertion, but this will increase the degree of lithium delithiation in the positive electrode, causing the positive electrode structure to collapse, and ultimately leading to lithium-ion battery failure. When the N / P ratio of the first negative electrode 11 to the third positive electrode 30 is 1.01 to 1.25, the first stacked core 100 has small cyclic expansion and long cycle life, and will not promote an increase in the degree of delithiation of the positive electrode.

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

[0171] The N / P ratio of the second negative electrode 21 to the third positive electrode 30 is 1.01 to 1.25. For example, the N / P ratio of the second negative electrode 21 to the third positive electrode 30 can be 1.01, 1.1, 1.2, or 1.25, etc., and is not limited to a single value. With this configuration, when the N / P ratio of the second negative electrode 21 to the third positive electrode 30 is less than 1.01, the second negative electrode 21 has a high degree of lithium insertion. As cycling progresses, the loss of lithium insertion sites leads to severe cycle expansion and affects cycle life. When the N / P ratio of the second negative electrode 21 to the third positive electrode 30 is greater than 1.25, the second negative electrode 21 has a low degree of lithium insertion, but this will increase the degree of delithiation of the positive electrode, causing the positive electrode structure to collapse, and ultimately leading to lithium-ion battery failure. When the N / P ratio of the second negative electrode 21 to the third positive electrode 30 is 1.01 to 1.25, the second stacked core 200 has small cycle expansion and long cycle life, and will not promote an increase in the degree of delithiation of the positive electrode.

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

[0173] In some examples, the difference between the N / P ratio of the first negative electrode 11 to the third positive electrode 30 and the N / P ratio of the second negative electrode 21 to the third positive electrode 30 is -0.5 to 0.5. Exemplarily, this difference can be -0.5, 1, or 0.5, without specific limitation. With this configuration, the cycle expansion of the first core stack 100 and the second core stack 200 is small, the cycle life is long, and it does not promote an increase in the degree of lithium delithiation of the positive electrode.

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

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

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

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

[0178] The lithium-ion battery is equipped with a battery management system. Switches are installed between the first positive tab 301 and the first stacked core 100, and between the first negative tab 302 and the first stacked core 100. When the lithium-ion battery is charged at a 3C rate, the battery management system disconnects the switches, preventing partial charging of the first stacked core 100, i.e., partially disconnecting the first stacked core 100.

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

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

[0181] Furthermore, along the length of the laminated battery cell, the first positive tab 301 and the second positive tab 401 are located on the same side of the laminated battery cell, and the first negative tab 302 and the second negative tab 402 are located on the same side of the laminated battery cell. This arrangement facilitates the stacking of the laminated battery cells.

[0182] Among them, the first positive tab 301 and the second positive tab 401 are located on one side of the -X axis direction of the laminated cell.

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

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

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

[0186] Lithium-ion batteries are equipped with a battery management system.

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

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

[0189] This invention provides a lithium-ion battery, including a casing and stacked cells, wherein the stacked cells are disposed in the casing.

[0190] The stacked battery cell in this embodiment has the same structure as the stacked battery cell provided in any of the above embodiments, and can bring the same or similar technical effects. It will not be described in detail here, but can be referred to the description of the above embodiments.

[0191] The lithium-ion battery of this application will be 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 lithium-ion battery preparation in this embodiment includes the following steps:

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

[0195] Lithium cobalt oxide, polyvinylidene fluoride, carbon black, and carbon nanotubes were added to N-methylpyrrolidone in a mass ratio of 97.5:1.5:0.5:0.5. After dispersion, a positive electrode slurry was obtained. The positive electrode slurry was coated onto aluminum foil and then rolled and slit to obtain the first positive electrode sheet 10.

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

[0197] The areal density of the first positive electrode active material layer 10b of the first positive electrode plate 10 can be 25 mg / cm³. 2 .

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

[0199] Ternary materials, polyvinylidene fluoride, carbon black, and carbon nanotubes are added to N-methylpyrrolidone in a mass ratio of 97.5:1.5:0.5:0.5. After dispersion, a positive electrode slurry is obtained. The positive electrode slurry is coated onto aluminum foil, and then rolled and slit to obtain the second positive electrode sheet 20.

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

[0201] The areal density of the second positive electrode active material layer 20b of the second positive electrode 20 can be 15 mg / cm³. 2 .

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

[0203] Lithium cobalt oxide, polyvinylidene fluoride, carbon black, and carbon nanotubes were added to N-methylpyrrolidone in a mass ratio of 97.5:1.5:0.5:0.5. After dispersion, a positive electrode slurry was obtained. The positive electrode slurry was coated onto aluminum foil and then rolled and slit to obtain the third positive electrode sheet 30.

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

[0205] The areal density of the third positive electrode active material layer 30b on the side of the third positive electrode sheet 30 facing the first core is 25 mg / cm³. 2 The thickness is 73.5 μm; the areal density of the third positive electrode active material layer 30b facing the second core stack is 15 mg / cm³. 2 The thickness is 44μm.

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

[0207] Artificial graphite is used as the first graphite. The first graphite, styrene-butadiene rubber, lithium polyacrylate and carbon black are added to deionized water in a mass ratio of 98:1.0:0.5:0.5. After dispersion, a negative electrode slurry is obtained. The positive electrode slurry is coated onto copper foil and then rolled, slit and other processes are used to obtain the first negative electrode sheet 11.

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

[0209] The compacted density of the first graphite is 1.7 g / cm³. 3 .

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

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

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

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

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

[0215] The compacted density of the first graphite is 1.7 g / cm³. 3 .

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

[0217] The second negative electrode active material layer 21b of the second negative electrode sheet 21 is provided with a plurality of mutually spaced circular holes. The diameter of the circular holes can 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 21 to the second positive electrode 20 is 1.1.

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

[0220] It should be noted that in this embodiment, neither the first graphite nor the second graphite is fast-charging 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 10 and the number of the second positive electrode 20 are both 10. The number of the first negative electrode 11 and the number of the second negative electrode 21 are both 10.

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

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

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

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

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

[0229] Lithium-ion batteries are obtained by processing stacked cells through steps such as packaging, liquid injection, formation, and sorting.

[0230] Examples 1-2

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

[0232] The compacted density of fast-charging graphite is 1.55 g / cm³. 3 .

[0233] Examples 1-3

[0234] The difference between Examples 1-3 and Examples 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 content of the first silicon-based material in the first negative electrode active material layer 11b of the first negative electrode sheet 11 is 25 wt%.

[0235] Examples 1-4

[0236] The difference between Examples 1-4 and Examples 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 Examples 1-5 and Examples 1-3 is that the first negative electrode current collector 11a of the first negative electrode 11 is a composite current collector. This 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 opposite sides of the polymer layer in the thickness direction of the laminated cell. The polymer layer can be made of polypropylene. The thickness of the polymer layer in the thickness direction of the laminated cell is 10 μm. The metal layers can be aluminum layers. The thickness of the two metal layers in the thickness direction of the laminated cell is 3 μm.

[0239] Examples 1-6

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

[0241] Examples 1-7

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

[0243] Examples 1-8

[0244] The difference between Examples 1-8 and Examples 1-3 is that the second negative electrode active material layer 21b of the second negative electrode sheet 21 is provided with multiple mutually spaced grooves.

[0245] Examples 1-9

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

[0247] Examples 1-10

[0248] The difference between Examples 1-10 and Examples 1-2 is that the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 can be 15 mg / cm³. 2 The thickness of the first positive electrode active material layer 10b can be 44 μm.

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

[0250] Examples 1-11

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

[0252] Examples 1-12

[0253] The difference between Examples 1-12 and Examples 1-3 is that the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is 30 mg / cm³. 2 The thickness is 87.5 μm.

[0254] Examples 1-13

[0255] The difference between Examples 1-13 and Examples 1-3 is that the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 is 35 mg / cm³. 2 The thickness is 102μm.

[0256] Examples 1-14

[0257] The difference between Examples 1-14 and Examples 1-3 is that the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 is 10 mg / cm³. 2 The thickness is 28.5μm.

[0258] Examples 1-15

[0259] The difference between Examples 1-15 and Examples 1-3 is that the areal density of the second positive electrode active material layer 20b of the second positive electrode 20 is 20 mg / cm³. 2 The thickness is 58μm.

[0260] Comparative Example 1

[0261] The difference between Comparative Example 1 and Example 1-1 is that the areal density of the first positive electrode active material layer 10b of the first positive electrode 10 can be 15 mg / cm³. 2 The thickness of the first positive electrode active material layer 10b can be 44 μm.

[0262] The second negative electrode active material layer 21b of the second negative electrode 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-charging 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 a lithium-ion battery is WED = E / M, where E is the battery's discharge energy. The test method involves charging the lithium-ion battery at a current of 0.2C to its upper voltage limit, then charging it at a constant voltage until the current drops to 0.025C, and then discharging it at a current of 0.2C until it reaches 2.75V. The energy discharged is E. M is the mass of the lithium-ion battery, obtained by weighing a finished lithium-ion battery. E / M is the measured mass energy density.

[0279] Charging time: The charging time described in this application is the time required to charge the battery cell from 0% SOC to 100% SOC. The test method is as follows: Under 25°C conditions, the lithium-ion battery is charged at a rate of 0.5C to the upper limit voltage, and then charged 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 cell.

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

[0281] Particle size (Dv50) testing: Disperse the sample to be tested in a liquid medium to ensure that the particles are fully dispersed and do not agglomerate; 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 and 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 that of the positive active material layer of the second positive electrode sheet, so that the first core has a high energy density; the second negative active material layer is provided with pores, so that the second core has fast charging performance.

[0283] A comparison between Examples 1-2 and Example 1-1 shows that the second graphite is fast-charging graphite, which can improve the fast-charging performance of the second stacked core.

[0284] By comparing Examples 1-3 and Examples 1-2, it can be seen that setting silicon-carbon in the first negative electrode active material layer of the first negative electrode sheet can improve the mass energy density of the first stacked core.

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

[0286] By comparing Examples 1-5 with Examples 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above 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: The first core stack (100) includes a first positive electrode (10), a first separator and a first negative electrode (11), wherein the first positive electrode (10), the first separator and the first negative electrode (11) are stacked alternately; The first positive electrode sheet (10) includes a first positive current collector (10a) and a first positive active material layer (10b) located on at least one side of the surface of the first positive current collector (10a). The first negative electrode sheet (11) includes a first negative electrode current collector (11a) and a first negative electrode active material layer (11b). The first negative electrode active material layer (11b) is disposed on at least one side of the thickness direction of the first negative electrode current collector (11a). The first negative electrode active material layer (11b) includes a first negative electrode active material, which includes a first silicon-based material. The second core (200) includes a second positive electrode (20), a second separator and a second negative electrode (21), wherein the second positive electrode (20), the second separator and the second negative electrode (21) are stacked alternately; The second positive electrode sheet (20) includes a second positive current collector (20a) and a second positive active material layer (20b) located on at least one side of the surface of the second positive current collector (20a). The second negative electrode sheet (21) includes a second negative electrode current collector (21a) and a second negative electrode active material layer (21b). The second negative electrode active material layer (21b) is disposed on at least one side of the thickness direction of the second negative electrode current collector (21a). The second negative electrode active material layer (21b) includes a second negative electrode active material, which includes 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). Wherein, the areal density of the first positive electrode active material layer (10b) of the first positive electrode (10) is greater than the areal density of the second positive electrode active material layer (20b) of the second positive electrode (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 (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 (21); The second positive electrode active material layer (20b) of the second positive electrode (20) and / or the second negative electrode active material layer (21b) of the second negative electrode (21) are provided with recesses (20c).

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

5.

3. The laminated cell according to claim 1, characterized in that, A lithium replenishment 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).

4. The laminated cell according to claim 3, characterized in that, The lithium replenishment layer (11c) includes metal segments spaced apart from each other.

5. The laminated cell according to claim 3, characterized in that, The area of ​​the negative electrode active material layer of the first negative electrode sheet (11) that is not covered by the lithium replenishment layer (11c) is the first region, and the area of ​​the negative electrode active material layer of the first negative electrode sheet (11) that is covered by the lithium replenishment layer (11c) is the second region. The area ratio of the first region to the second region is 0.2 to 5.

6. The laminated cell according to claim 1, characterized in that, The first negative electrode (11) 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 being 0.3 to 5 μm and the thickness of the polymer layer being 1 to 20 μm; The polymer layer is made of materials including polyethylene terephthalate, polyethylene, or polypropylene.

7. The laminated cell according to claim 6, characterized in that, The tensile strength of the first negative electrode (11) is greater than or equal to 100 MPa.

8. The laminated cell according to claim 1, characterized in that, The recess (20c) is disposed on the second negative electrode active material layer (21b), and the recess includes a plurality of spaced-apart circular holes or grooves.

9. The laminated cell according to claim 8, characterized in that, The distance between the centers of two adjacent circular holes is 0.5~5mm, the diameter of the circular holes is 20~2000μm, and the depth of the circular holes is 3~70μm; or, in the thickness direction of the stacked cell, the depth of the circular holes 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).

10. The laminated cell according to claim 8, characterized in that, The spacing between two adjacent grooves is 0.5~5mm, and the depth of the groove is 3~70μm; or, in the thickness direction of the stacked cell, 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).

11. The laminated 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 that of the first graphite (Dv50), and the compaction density of the first graphite is greater than that of the second graphite.

12. The laminated cell according to any one of claims 1-11, characterized in that, The first negative electrode tab (302) and the second negative electrode tab (402) are connected to form the third negative electrode tab (500).

13. The laminated cell according to claim 12, 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); Along the length of the laminated battery cell, the first positive tab and the second positive tab are located on the same side of the laminated battery cell, and the first negative tab and the second negative tab are located on the same side of the laminated battery cell. Along the length of the laminated battery cell, the first positive tab and the first negative tab are located on both sides of the laminated battery cell, and the second positive tab and the second negative tab are located on both sides of the laminated battery cell.

14. The laminated cell according to any one of claims 1-11, characterized in that, The areal density of the first positive electrode active material layer (10b) of the first positive electrode plate (10) is 5-40 mg / cm³. 2 ; The areal density of the second positive electrode active material layer (20b) of the second positive electrode plate (20) is 5-40 mg / cm³. 2 ; The content of the first silicon-based material in the first negative electrode active material layer (11b) of the first negative electrode (11) is 5~50wt%; the content of the second silicon-based material in the second negative electrode active material layer (21b) of the second negative electrode (21) is 0~40wt%.

15. A lithium-ion battery, characterized in that, It includes a housing and a laminated cell as described in any one of claims 1-14, wherein the laminated cell is disposed in the housing.

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