Battery and electronic device

Abstract

A battery and an electronic device. The battery comprises a casing, an electrode assembly, a first negative terminal, and a second negative terminal. The electrode assembly is accommodated in the casing. The electrode assembly comprises a first laminate body and a second laminate body, the first laminate body comprising a first negative electrode sheet, a first separator and a first positive electrode sheet which are stacked in a thickness direction of the electrode assembly, and the second laminate body comprising a second negative electrode sheet, a second separator and a second positive electrode sheet which are stacked in the thickness direction of the electrode assembly. The first negative electrode sheet comprises a first negative active material layer containing a silicon-based material, the silicon-based material being at least one of silicon, silicon carbon and silica. The second negative electrode sheet comprises a second negative electrode active material layer containing graphite. The first negative terminal is electrically connected to the first negative electrode sheet, and the second negative terminal is electrically connected to the second negative electrode sheet. The first negative terminal and the second negative terminal extend from the inside of the casing to the outside of the casing and extend out of the casing.

Description

Batteries and electronic devices Technical Field

[0001] The present application relates to the field of energy storage devices, and in particular to a battery and electronic equipment. Background Art

[0002] With the advancement of the times and the development of science and technology, the requirements for secondary batteries are becoming increasingly higher. Secondary batteries must not only have high energy density, power density and high safety, but also have a long service life. This is especially true in the fields of electric vehicles and large-scale energy storage, where the lifespan requirements for secondary batteries are becoming increasingly stringent.

[0003] Summary of the Invention

[0004] One object of the present application is to provide a battery with a higher cycle life.

[0005] In a first aspect, the present application provides a battery comprising a housing, an electrode assembly, a first negative electrode terminal, and a second negative electrode terminal. The electrode assembly is housed in the housing. The electrode assembly comprises a first stack and a second stack. The first stack comprises a first negative electrode sheet, a first separator, and a first positive electrode sheet stacked along the thickness direction of the electrode assembly. The second stack comprises a second negative electrode sheet, a second separator, and a second positive electrode sheet stacked along the thickness direction of the electrode assembly. The first negative electrode sheet comprises a first negative electrode active material layer comprising a silicon-based material, wherein the silicon-based material is at least one of silicon, silicon carbon, and silicon oxygen. The second negative electrode sheet comprises a second negative electrode active material layer comprising graphite. The first negative terminal is electrically connected to the first negative electrode sheet, and the second negative terminal is electrically connected to the second negative electrode sheet. The first negative terminal and the second negative terminal extend from the inside of the housing to the outside of the housing and extend out of the housing.

[0006] The present application configures the first stack and the second stack as two electrode assemblies. The negative active material of the first stack contains a silicon-based material, and the negative active material of the second stack is graphite, so that the fast charging and long life characteristics of graphite can be utilized. When charging the battery: first charge the second stack at a higher rate (such as 3C-10C), and then charge the first stack at a lower rate (such as 1C-3C); when discharging the battery: the second stack is discharged first, and after the second stack is discharged, the first stack starts to discharge, serving as a backup power supply. Such a structural design utilizes both the high energy density characteristics of the first stack and the fast charging and long life characteristics of the second stack.

[0007] According to some embodiments of the present application, the battery further includes a positive terminal, and the first positive electrode sheet and the second positive electrode sheet are both electrically connected to the positive terminal. The first stack and the second stack share the same positive terminal, which facilitates processing and manufacturing.

[0008] According to some embodiments of the present application, the battery further includes a first positive terminal and a second positive terminal, wherein the first positive terminal is electrically connected to the first positive electrode sheet, and the second positive terminal is electrically connected to the second positive electrode sheet. Different positive terminals are used for the first and second stacks to reduce the risk of mutual interference.

[0009] According to some embodiments of the present application, the content of silicon in the first negative electrode active material layer is greater than 5 wt % and less than or equal to 50 wt %.

[0010] According to some embodiments of the present application, the silicon content in the first negative electrode active material layer is 9% to 24 wt%, which further improves the cycle expansion rate of the battery, thereby allowing the battery to have a higher capacity retention rate and is conducive to improving the cycle life.

[0011] According to some embodiments of the present application, the first negative electrode active material layer further includes graphite.

[0012] According to some embodiments of the present application, a cavity is provided in the shell, and the first stacked body and the second stacked body are both accommodated in the cavity.

[0013] According to some embodiments of the present application, a first cavity and a second cavity that are independent of each other are provided in the shell, the first stacked body is accommodated in the first cavity, and the second stacked body is accommodated in the second cavity.

[0014] According to some embodiments of the present application, in the thickness direction of the electrode assembly, the outermost electrode sheet of the first stack facing the shell is a single-sided coated positive electrode sheet, the coated surface of which faces the inner side of the electrode assembly, and the surface facing the shell is not coated with positive electrode active material, so that the positive electrode active material of the outermost positive electrode sheet and the negative electrode active material of the adjacent negative electrode sheet can be fully utilized, thereby improving the energy density.

[0015] According to some embodiments of the present application, in the thickness direction of the electrode assembly, the outermost electrode sheet of the first stack facing the second stack is a double-sided coated electrode sheet.

[0016] A second aspect of the present application further provides an electronic device comprising the above-mentioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] FIG1 is a schematic structural diagram of a battery provided in one embodiment of the present application.

[0019] FIG2 is a schematic structural diagram of an electrode assembly provided in one embodiment of the present application.

[0020] FIG3 is a schematic cross-sectional view of an electrode assembly provided in one embodiment of the present application.

[0021] FIG4 is an exploded view of the battery shown in FIG1 .

[0022] FIG5 is a schematic structural diagram of a battery provided in another embodiment of the present application.

[0023] FIG6 is an exploded view of the battery shown in FIG5 .

[0024] Description of main component symbols

[0025] Battery 100;

[0026] Housing 10;

[0027] Electrode assembly 20;

[0028] positive terminal 30;

[0029] negative terminal 40;

[0030] a first negative electrode terminal 41;

[0031] a second negative terminal 42;

[0032] First stack 21;

[0033] a second stacked body 22;

[0034] a first negative electrode plate 211;

[0035] a first diaphragm 212;

[0036] a first positive electrode plate 213;

[0037] a second negative electrode plate 221;

[0038] a second diaphragm 222;

[0039] a second positive electrode plate 223;

[0040] First positive electrode current collector 213a;

[0041] First positive electrode active material layer 213b;

[0042] First positive electrode tab 213c;

[0043] Second positive electrode current collector 223a;

[0044] Second positive electrode active material layer 223b;

[0045] Second positive electrode tab 223c;

[0046] a first negative electrode current collector 211 a;

[0047] First negative electrode active material layer 211b;

[0048] First negative electrode tab 211c;

[0049] Second negative electrode current collector 221a;

[0050] Second negative electrode active material layer 221b;

[0051] Second negative electrode tab 221c;

[0052] a first housing portion 11;

[0053] a second housing portion 12;

[0054] Cavity 101;

[0055] Sealing portion 102;

[0056] a first positive terminal 31;

[0057] a second positive terminal 32;

[0058] Separator 13;

[0059] First cavity 101a;

[0060] Second cavity 101b;

[0061] The thickness direction Z of the electrode assembly. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0063] In addition, for the sake of brevity and clarity, the size or thickness of various components or layers may be exaggerated in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, element A can be directly connected to element B, or there may be an intermediate element C and element A and element B can be indirectly connected to each other.

[0064] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0065] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0066] It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below may be referred to as the second element, component, region, layer or part without departing from the teachings of the exemplary embodiments.

[0067] Referring to Figure 1 , one embodiment of the present application provides a battery 100 comprising a housing 10, an electrode assembly 20 and electrolyte contained within the housing 10, and a positive terminal 30 and a negative terminal 40 protruding from the exterior of the housing 10. Both the positive terminal 30 and the negative terminal 40 are connected to the electrode assembly 20, extending from the interior of the housing 10 toward the exterior of the housing 10 and extending beyond the housing 10 for connection to external components. In this embodiment, there is one positive terminal 30 and two negative terminals 40, comprising a first negative terminal 41 and a second negative terminal 42.

[0068] Referring to Figures 2 (the separator is not shown) and 3, the electrode assembly 20 includes a first stack 21 and a second stack 22. The first stack 21 includes a first negative electrode sheet 211, a first separator 212, and a first positive electrode sheet 213 alternately stacked along the thickness direction Z of the electrode assembly. The first separator 212 is disposed between the first negative electrode sheet 211 and the first positive electrode sheet 213 to reduce the risk of direct contact and short circuit between the first negative electrode sheet 211 and the first positive electrode sheet 213. The second stack 22 includes a second negative electrode sheet 221, a second separator 222, and a second positive electrode sheet 223 alternately stacked along the thickness direction Z of the electrode assembly. The second separator 222 is disposed between the second negative electrode sheet 221 and the second positive electrode sheet 223 to reduce the risk of direct contact and short circuit between the second negative electrode sheet 221 and the second positive electrode sheet 223.

[0069] The first positive electrode sheet 213 includes a first positive current collector 213a, a first positive active material layer 213b, and a first positive electrode tab 213c. The first positive active material layer 213b is disposed on at least one surface of the first positive current collector 213a. The second positive electrode sheet 223 includes a second positive current collector 223a, a second positive active material layer 223b, and a second positive electrode tab 223c. The second positive active material layer 223b is disposed on at least one surface of the second positive current collector 223a. The first positive electrode tab 213c is electrically connected to the first positive current collector 213a, and the second positive electrode tab 223c is electrically connected to the second positive current collector 223a. Both the first positive electrode tab 213c and the second positive electrode tab 223c are electrically connected to the positive terminal 30. In this embodiment, the first positive electrode tab 213c extends outward from one end of the first positive current collector 213a in the region away from the first positive active material layer 213b, and the second positive electrode tab 223c extends outward from one end of the second positive current collector 223a in the region away from the second positive active material layer 223b. In other embodiments, the first positive electrode tab 213c can be welded to the region where the first positive current collector 213a leaves the first positive active material layer 213b, and the second positive electrode tab 223c can be welded to the region where the second positive current collector 223a leaves the second positive active material layer 223b. The first positive electrode collector 213a, the first positive electrode tab 213c, the second positive electrode tab 223a, and the second positive electrode tab 223c can each include at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof.

[0070] The first positive electrode active material layer 213b and the second positive electrode active material layer 223b each include a positive electrode active material, a conductive agent, and a binder. The positive electrode active material may include one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate. The conductive agent may include one or more of doxen black, conductive carbon black, acetylene black, graphene, carbon nanotubes, carbon fibers, and the like. The binder may include one or more of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, and sodium carboxymethyl cellulose.

[0071] The first negative electrode sheet 211 includes a first negative electrode current collector 211a, a first negative electrode active material layer 211b, and a first negative electrode tab 211c. The first negative electrode active material layer 211b is disposed on at least one surface of the first negative electrode current collector 211a, and the first negative electrode tab 211c is electrically connected to the first negative electrode current collector 211a and the first negative electrode terminal 41. The second negative electrode sheet 221 includes a second negative electrode current collector 221a, a second negative electrode active material layer 221b, and a second negative electrode tab 221c. The second negative electrode active material layer 221b is disposed on at least one surface of the second negative electrode current collector 221a, and the second negative electrode tab 221c is electrically connected to the second negative electrode current collector 221a and the second negative electrode terminal 42. In this embodiment, the first negative electrode tab 211c extends outward from one end of the first negative electrode current collector 211a in the region where it leaves the first negative electrode active material layer 211b, and the second negative electrode tab 221c extends outward from one end of the second negative electrode current collector 221a in the region where it leaves the second negative electrode active material layer 221b. In other embodiments, the first negative electrode tab 211c can be welded to the region where the first negative electrode current collector 211a leaves the first negative electrode active material layer 211b, and the second negative electrode tab 221c can also be welded to the region where the second negative electrode current collector 221a leaves the second negative electrode active material layer 221b. The first negative electrode current collector 211a, the first negative electrode tab 211c, the second negative electrode tab 221a, and the second negative electrode tab 221c can each include at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof.

[0072] The first negative electrode active material layer 211b and the second negative electrode active material layer 221b both include a negative electrode active material, a conductive agent and a binder. The conductive agent may include at least one of conductive carbon black, carbon nanotubes, carbon fibers or graphene, and the binder may include at least one of styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylic acid or sodium carboxymethyl cellulose.

[0073] The negative electrode active material of the first negative electrode active material layer 211b comprises a silicon-based material, which includes at least one of silicon, silicon-carbon, and silicon-oxygen. The negative electrode active material of the second negative electrode active material layer 221b is graphite. When silicon-based materials are added to graphite for use as the negative electrode active material, the battery's cycle life can be drastically reduced and cyclic expansion can be dramatically increased. This is due to, on the one hand, the generation of byproducts from the silicon-based material itself, and, on the other hand, the impact of these side reactions on the graphite cycle. In this application, the configuration of a first negative electrode plate 211 comprising a silicon-based material as the negative electrode active material and a second negative electrode plate 221 comprising graphite as the negative electrode active material reduces the impact of the silicon-based material on the graphite compared to a case where both negative electrode plates comprise silicon-based materials and graphite. The silicon-based material of the first negative electrode plate 211 does not cause expansion or cyclic attenuation on the second negative electrode plate 221, thereby improving cycle life.

[0074] The present application configures a first negative terminal 41 and a second negative terminal 42 connected to the first stack 21 and the second stack 22, respectively. The first stack 21 can be charged and discharged through the first negative terminal 41 and the positive terminal 30, and the second stack 22 can be charged and discharged through the second negative terminal 42 and the positive terminal 30. The negative electrode active material of the first negative electrode plate 211 of the first stack 21 includes a silicon-based material, and the negative electrode active material of the second negative electrode plate 221 of the second stack 22 is graphite. Taking advantage of the fast charging characteristics of graphite, during the charging process of the battery 100, the second stack 22 is first charged at a high rate, and then the first stack 21 is charged at a low rate until the battery 100 is fully charged; during the discharge process of the battery 100, the second stack 22 is preferentially used for discharge. After the second stack 22 has been discharged, the first stack 21 is used for discharge, thereby improving the cycle life.

[0075] Please refer to Figure 2. The first stack 21 and the second stack 22 are stacked along the thickness direction Z of the electrode assembly. The outermost layer of the first stack 21 facing the shell 10 in the thickness direction Z of the electrode assembly is a single-sided coated positive electrode sheet, so that the positive electrode active material of the outermost positive electrode sheet and the negative electrode active material of the adjacent negative electrode sheet can be fully utilized, thereby improving the energy density. The electrode sheet of the first stack 21 facing the second stack 22 in the thickness direction Z of the electrode assembly is a double-sided coated electrode sheet. In this application, a single-sided coated positive electrode sheet refers to a positive electrode sheet with positive electrode active material coated on only one surface, and a double-sided coated electrode sheet refers to a electrode sheet with active material coated on both surfaces. It can be understood that the surface of the single-sided coated positive electrode sheet that is not coated with positive electrode active material can be coated with other functional layers, such as an insulating layer.

[0076] In some embodiments, when viewed along the thickness direction Z of the electrode assembly, the first positive electrode tab 213c and the second positive electrode tab 223c have an overlapping portion, which facilitates connecting the first positive electrode tab 213c and the second positive electrode tab 223c to the positive electrode terminal 30. When viewed along the thickness direction Z of the electrode assembly, the first negative electrode tab 211c and the second negative electrode tab 221c are separated, which facilitates connecting the first negative electrode tab 211c and the second negative electrode tab 221c to the first negative electrode terminal 41 and the second negative electrode terminal 42, respectively.

[0077] In some embodiments, the negative active material of the first negative active material layer 211 b further includes graphite.

[0078] In some embodiments, the silicon content in the first negative electrode active material layer 211b is greater than 5 wt% and less than or equal to 50 wt%. Preferably, the silicon content in the first negative electrode active material layer 211b is 9% to 24 wt%, which is beneficial to improving cycle life.

[0079] The first diaphragm 212 and the second diaphragm 222 can be films made of one or more materials selected from polyethylene, polypropylene, non-woven fabrics, and polyfibers.

[0080] The electrolyte can be a solution containing one or more organic carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate as a solvent, and one or more lithium salts selected from LiPF6, LiBF4, LiBOB, LiAsF6, Li(CF3SO2)2N, LiCF3SO3, and LiCTO4 as a solute.

[0081] Referring to Figures 1 and 4, the housing 10 includes a first housing portion 11 and a second housing portion 12 that are opposite to each other in the thickness direction Z of the electrode assembly. The first housing portion 11 and the second housing portion 12 are connected to form a cavity 101 and a sealing portion 102 that surrounds and seals the cavity 101. The first stack 21 and the second stack 22 are both accommodated in the cavity 101, and the first stack 21 and the second stack 22 are in contact with each other on two adjacent surfaces in the thickness direction Z of the electrode assembly. The first stack 21 and the second stack 22 are housed in the same cavity 101 and share the electrolyte contained in the cavity 101, which facilitates manufacturing and processing.

[0082] Referring to FIG. 5 , in some embodiments, there are two positive terminals 30 , including a first positive terminal 31 and a second positive terminal 32 . The first positive terminal 31 is electrically connected to the first positive electrode tab 213 c of the first stack 21 . The second positive terminal 32 is electrically connected to the second positive electrode tab 223 c of the second stack 22 . The first positive terminal 31 and the first negative terminal 41 enable charging and discharging of the first stack 21 . The second positive terminal 32 and the second negative terminal 42 enable charging and discharging of the second stack 22 .

[0083] Referring to FIG6 , in some embodiments, the housing 10 further includes a partition 13 disposed between the first housing portion 11 and the second housing portion 12, dividing the chamber 101 into a first chamber 101a and a second chamber 101b. The first stack 21 is housed in the first chamber 101a, and the second stack 22 is housed in the second chamber 101b. The first stack 21 and the second stack 22 are housed in two independent chambers and do not share electrolyte, thereby reducing the risk of mutual interference.

[0084] One embodiment of the present application further provides an electronic device comprising the battery of the present application. The electronic device can be any electrical device that uses a battery, for example, a mobile phone, a portable device, a laptop computer, a battery-powered vehicle, an electric vehicle, a ship, a spacecraft, an electric toy, or an electric tool.

[0085] Some specific embodiments and comparative examples are listed below to better illustrate the present application, wherein a lithium-ion battery is used as an example.

[0086] Example 1

[0087] Preparation of the positive electrode: Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride were mixed in a weight ratio of 97:1.4:1.6, and N-methylpyrrolidone was added as a solvent. The mixture was stirred evenly to obtain a slurry with a solid content of 72 wt%. The slurry was evenly coated on aluminum foil to a thickness of 80 μm, dried at 85°C, and then cold pressed, cut, and slit. The resulting positive electrode was then dried under vacuum at 85°C for 4 hours to obtain the positive electrode.

[0088] Preparation of the negative electrode plate: 95.5wt% of negative electrode active material (14wt% silicon carbon and 86wt% graphite), 2.5wt% polyacrylic acid, 1wt% sodium carboxymethyl cellulose and 1wt% carbon nanotubes are mixed and coated on copper foil to form a negative electrode active material layer to obtain a first negative electrode plate. The content of silicon element in the active material layer of the first negative electrode plate is 7wt%; 97.5wt% of graphite, 1.5wt% of styrene-butadiene rubber and 1wt% sodium carboxymethyl cellulose are mixed and coated on copper foil to form a negative electrode active material layer to obtain a second negative electrode plate. Since the second negative electrode plate does not contain silicon-based material, the content of silicon element in the second negative electrode plate is 0%.

[0089] Preparation of diaphragm: A polyethylene film with a thickness of 7 μm was selected as the diaphragm.

[0090] Preparation of electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:PC:DEC = 1:1:1, dissolved and stirred thoroughly, and then lithium salt LiPF6 was added. After mixing evenly, an electrolyte was obtained, in which the concentration of lithium salt LiPF6 was 1 mol / L.

[0091] Preparation of a lithium-ion battery: The positive electrode sheet, separator, first negative electrode sheet, and second negative electrode sheet are stacked in sequence, with the separator positioned between the positive electrode sheet and the corresponding negative electrode sheet to provide isolation. The stacking process yields the electrode assembly shown in Figure 2. The silicon content in the negative active material layer of all negative electrode sheets (first negative electrode sheet and second negative electrode sheet) is 5 wt% (i.e., the total silicon content of the battery). The electrode assembly is placed in an outer aluminum-plastic film package, dehydrated at 80°C, and then injected with the aforementioned electrolyte and packaged. After formation, degassing, and trimming, the lithium-ion battery shown in Figure 1 is obtained.

[0092] Examples 2-8

[0093] The difference from Example 1 is that the content of silicon in the negative electrode active material layer of all negative electrode sheets is different.

[0094] Comparative Example 1

[0095] The difference from Example 1 lies in the preparation of the negative electrode sheet and the preparation of the lithium-ion battery.

[0096] Preparation of the negative electrode sheet: 97.5wt% of the negative electrode active material (10wt% silicon carbon and 95wt% graphite), 2wt% of polyacrylic acid, 1wt% of sodium carboxymethyl cellulose and 0.5wt% of carbon nanotubes are mixed and coated on a copper foil to form a negative electrode active material layer to obtain a negative electrode sheet.

[0097] Preparation of a lithium-ion battery: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is formed by stacking the sheets. The silicon content in the negative active material layer of all negative electrode sheets is 5 wt%. The electrode assembly is placed in an aluminum-plastic film package, dehydrated at 80°C, and then the electrolyte is injected and packaged. After formation, degassing, and trimming, a lithium-ion battery similar to Figure 1 is obtained, with a single negative terminal.

[0098] The lithium-ion batteries of the comparative examples and embodiments were subjected to cycle performance tests and cycle thickness expansion tests. The test results are shown in Table 1.

[0099] 25°C Cycling Capacity Retention: The battery under test is placed at 25°C and left to rest for 5 minutes. The lithium-ion battery is then charged to 4.5V at a constant current of 1.5C. Then, it is charged to 0.05C at a constant voltage of 4.5V. After 5 minutes of rest, the battery is discharged to 3.0V at a constant current of 1.0C and left to rest for 5 minutes. The capacity at this point is recorded as D0. Repeat this charge and discharge process 500 times, recording the final discharge capacity as D1. After cycling at 25°C, the capacity decay rate is D1 / D0, expressed in %.

[0100] Cyclic Thickness Expansion Test: A lithium-ion battery is placed at a test temperature of 25°C and allowed to rest for 5 minutes. The battery is then charged to 4.5V at a constant current of 1.5C. Then, it is charged to 0.05C at a constant voltage of 4.5V and allowed to rest for 5 minutes. The thickness of the battery, T0, is measured using a flat-plate thickness tester. The battery is then discharged to 3.0V at a constant current of 0.5C and allowed to rest for 5 minutes. This charge and discharge cycle is repeated 500 times, and the battery thickness, T1, is measured again. The thickness growth rate is calculated as (T1-T0) / T0.

[0101] Table 1

[0102] It can be seen from Comparative Example 1 and Examples 1-8 that, under the condition of the same silicon content, part of the negative electrode sheet in Comparative Example 1 is replaced by a second negative electrode sheet whose negative electrode active material is graphite, and the number of negative terminals is set to two. Compared with the comparative example, under the same silicon content in the overall negative electrode sheet, the battery cycle retention rate and thickness expansion during the cycle can be improved by separating the first negative electrode sheet and the second negative electrode sheet. If the silicon content in the first electrode sheet is low (such as Example 1), the improvement effect is not obvious; if the silicon content in the first electrode sheet is too high (such as Examples 7 and 8), the expansion increases and the cycle will deteriorate. It is speculated that the high silicon content may cause part of the silicon to lose electrical contact after the expansion and contraction of the first electrode sheet during the cycle, and the cycle will deteriorate. Therefore, the silicon content in the first electrode sheet needs to be controlled at an appropriate proportion.

[0103] The above disclosure is only a preferred embodiment of the present application and certainly cannot be used to limit the present application. Therefore, equivalent changes made based on the present application are still within the scope covered by the present application.

Claims

1. A battery, comprising a housing and an electrode assembly, wherein the electrode assembly is accommodated in the housing, characterized in that: The electrode assembly includes a first stack and a second stack, the first stack includes a first negative electrode sheet, a first separator and a first positive electrode sheet stacked along the thickness direction of the electrode assembly, the second stack includes a second negative electrode sheet, a second separator and a second positive electrode sheet stacked along the thickness direction of the electrode assembly, the first negative electrode sheet includes a first negative electrode active material layer containing a silicon-based material, and the silicon-based material is at least one of silicon, silicon carbon and silicon oxygen; the second negative electrode sheet includes a second negative electrode active material layer whose negative electrode active material is graphite; the battery also includes a first negative terminal and a second negative terminal, the first negative terminal is electrically connected to the first negative electrode sheet, the second negative terminal is electrically connected to the second negative electrode sheet, and the first negative terminal and the second negative terminal extend from the inside of the shell to the outside of the shell and extend out of the shell.

2. The battery according to claim 1, characterized in that The battery further includes a positive terminal, and the first positive electrode sheet and the second positive electrode sheet are both electrically connected to the positive terminal.

3. The battery according to claim 1, characterized in that The battery further includes a first positive terminal and a second positive terminal, wherein the first positive terminal is electrically connected to the first positive electrode sheet, and the second positive terminal is electrically connected to the second positive electrode sheet.

4. The battery according to claim 1, characterized in that The content of silicon in the first negative electrode active material layer is greater than 5 wt % and less than or equal to 50 wt %.

5. The battery according to claim 4, characterized in that The content of silicon in the first negative electrode active material layer is 9% to 24 wt %.

6. The battery according to claim 4 or 5, characterized in that The first negative electrode active material layer further includes graphite.

7. The battery according to claim 1, characterized in that A cavity is provided in the shell, and the first stacked body and the second stacked body are both accommodated in the cavity.

8. The battery according to claim 1, characterized in that A first cavity and a second cavity which are independent of each other are arranged in the shell, the first stacked body is accommodated in the first cavity, and the second stacked body is accommodated in the second cavity.

9. The battery according to claim 1, characterized in that The outermost layer of the first stack facing the shell in the thickness direction of the electrode assembly is a single-sided coated positive electrode sheet.

10. The battery according to claim 1, characterized in that The outermost electrode sheet of the first stack facing the second stack in the thickness direction of the electrode assembly is a double-sided coated electrode sheet.

11. An electronic device, characterized in that: Comprising the battery according to any one of claims 1 to 10.

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