Battery cell, secondary battery, and electric device

Abstract

This application discloses a battery cell, a secondary battery, and an electrical device, belonging to the field of battery technology. The battery cell includes a negative electrode, a separator, and a positive electrode. The negative electrode includes a negative current collector, a negative active material layer, and a lithium replenishment layer arranged sequentially. The separator includes a fluorinated carbon material layer, a base film, and a first ceramic layer arranged sequentially. This application places the fluorinated carbon material layer between the base film and the lithium replenishment layer of the negative electrode, allowing the fluorinated carbon material and the lithium replenishment material to react during battery charging and discharging to generate lithium fluoride and carbon. This not only improves the stability, uniformity, and mechanical strength of the SEI film, preventing the separator from being punctured by dead lithium or lithium dendrites, but also suppresses side reactions between the lithium replenishment material and the electrolyte, improving lithium replenishment efficiency. This application also places the first ceramic layer on the side of the base film facing the positive electrode, which improves the puncture strength of the separator, reduces chemical reaction heat, and enhances battery safety.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell, a secondary battery, and an electrical device. Background Technology

[0002] During the first charge of a lithium-ion battery, a series of complex electrochemical reactions occur. For example, the electrolyte reacts with the negative electrode material to form a solid electrolyte interphase (SEI) film. This process consumes lithium ions, resulting in irreversible lithium loss. As the pursuit of higher energy density in lithium-ion batteries increases, novel high-capacity negative electrode materials such as silicon-based negative electrodes are being used more and more widely. However, compared with commonly used negative electrode materials such as graphite, silicon-based negative electrode materials undergo greater volume changes during charge and discharge, leading to a more complex SEI film formation process and more severe lithium loss.

[0003] Given the widespread application of silicon anode materials and the pursuit of high energy density in batteries, pre-lithiation of the anode to compensate for irreversible lithium loss and thus improve the battery's initial efficiency and capacity is a necessary measure. Currently, industrially, a lithium layer is often placed on the active material layer of the anode. This allows the lithium consumed during SEI film formation to be provided by the lithium layer, thus avoiding the waste of lithium ions released from the cathode. However, this method directly alters the thermodynamic and kinetic formation process of the SEI film. While this may optimize the SEI film's chemical composition (e.g., by increasing inorganic components), it also presents challenges in terms of SEI film thickness, uniformity, and mechanical stability, thereby affecting the battery's energy density. Utility Model Content

[0004] The purpose of this application is to overcome the shortcomings of existing technologies and provide a battery cell, a secondary battery, and an electrical device. This application places a fluorinated carbon material layer between the base film and the lithium replenishment layer of the negative electrode sheet. During battery charging and discharging, the fluorinated carbon material reacts with the lithium replenishment material to generate lithium fluoride and carbon. This not only improves the stability, uniformity, and mechanical strength of the SEI film, preventing the separator from being punctured by dead lithium or lithium dendrites, but also suppresses side reactions between the lithium replenishment material and the electrolyte, improving lithium replenishment efficiency. The generated carbon can increase the liquid retention of the negative electrode and improve the electronic conductivity network at the negative electrode interface. This application also places a first ceramic layer on the side of the base film facing the positive electrode sheet, which can improve the puncture strength of the separator, reduce the heat of chemical reaction, and prevent separator failure caused by shrinkage along the puncture holes, thereby improving the battery's safety performance.

[0005] To achieve the above objectives, in a first aspect of this application, this application provides a battery cell, including a negative electrode sheet, a separator, and a positive electrode sheet, wherein the separator is disposed between the negative electrode sheet and the positive electrode sheet, and the negative electrode sheet includes a negative current collector, a negative active material layer, and a lithium replenishment layer disposed sequentially, wherein the negative active material layer is located between the negative current collector and the lithium replenishment layer.

[0006] The separator comprises a fluorinated carbon material layer, a base film, and a first ceramic layer arranged sequentially. The fluorinated carbon material layer is located between the base film and the lithium replenishment layer, and the first ceramic layer is located between the base film and the positive electrode sheet.

[0007] As an embodiment of this application, the ratio of the thickness of the fluorinated carbon material layer to the thickness of the lithium replenishment layer is 1:(0.1~100).

[0008] As an embodiment of this application, the thickness of the fluorinated carbon material layer is 0.1 to 10 μm.

[0009] As an embodiment of this application, the fluorocarbon material layer includes fluorocarbon material, and the particle size Dv50 of the fluorocarbon material is 1nm to 8μm.

[0010] As an embodiment of this application, the thickness of the diaphragm is 5–25 μm.

[0011] As an embodiment of this application, the porosity of the diaphragm is 20-80%.

[0012] As an embodiment of this application, the thickness of the first ceramic layer is 0.5 to 5 μm.

[0013] As an embodiment of this application, the first ceramic layer includes a ceramic material, wherein the particle size Dv50 of the ceramic material in the first ceramic layer is 0.01 to 2 μm.

[0014] As an embodiment of this application, the separator further includes a lithiophilic layer disposed between the fluorinated carbon material layer and the base film, the lithiophilic layer having a thickness of 0.1–3 μm.

[0015] As an embodiment of this application, the diaphragm further includes a second ceramic layer disposed between the fluorocarbon material layer and the base membrane.

[0016] Furthermore, the thickness of the second ceramic layer is 0.5–5 μm.

[0017] Furthermore, the second ceramic layer comprises a ceramic material, wherein the particle size Dv50 of the ceramic material in the second ceramic layer is 0.01–2 μm.

[0018] In a second aspect of this application, a secondary battery is provided, including the battery cell provided in the first aspect of this application.

[0019] In a third aspect of this application, an electrical device is provided, including the secondary battery provided in the second aspect of this application. Attached Figure Description

[0020] Figure 1 A partial cross-sectional view of the battery cell provided in this application;

[0021] Figure 2 Another partial cross-sectional view of the battery cell provided in this application;

[0022] Figure 3 Another partial cross-sectional view of the battery cell provided in this application.

[0023] In the figure, 1-negative electrode, 11-negative current collector, 12-negative active material layer, 13-lithium replenishment layer, 2-separator, 21-base film, 22-fluorinated carbon material layer, 23-first ceramic layer, 24-lithophile layer, 25-second ceramic layer, 3-positive electrode, 31-positive current collector, 32-positive active material layer. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, the use of "first" and "second" is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0027] In this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0028] In this application, the terms "an embodiment," "some embodiments," "illustrative embodiment," "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 the embodiments or examples of this application. In this application, 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.

[0029] To achieve the above objectives, in a first aspect of this application, this application provides a battery cell, including a negative electrode 1, a separator 2, and a positive electrode 3. The separator 2 is disposed between the negative electrode 1 and the positive electrode 3. The negative electrode 1 includes a negative current collector 11, a negative active material layer 12, and a lithium replenishment layer 13 disposed sequentially. The negative active material layer is located between the negative current collector and the lithium replenishment layer.

[0030] The separator 2 includes a fluorinated carbon material layer 22, a base membrane 21 and a first ceramic layer 23 arranged sequentially. The fluorinated carbon material layer 22 is located between the base membrane 21 and the lithium replenishment layer 13, and the first ceramic layer 23 is located between the base membrane 21 and the positive electrode 3.

[0031] This application sequentially arranges a fluorinated carbon material layer 22, a base film 21, and a first ceramic layer 23, with the fluorinated carbon material layer 22 positioned between the base film 21 and the lithium replenishment layer 13. This allows the fluorinated carbon material to react with the lithium replenishment material during battery charging and discharging to generate lithium fluoride and carbon. The generated lithium fluoride is a component of the SEI film, which can improve the stability, uniformity, and mechanical strength of the SEI film, thereby preventing the separator 2 from being pierced by dead lithium or lithium dendrites. It can also suppress side reactions between the lithium replenishment material and the electrolyte, improving the lithium replenishment efficiency. The generated carbon can increase the liquid retention of the negative electrode and improve the electronic conductivity network at the negative electrode interface.

[0032] This application provides a first ceramic layer 23 on the side of the base film 21 facing the positive electrode 3, which can improve the puncture strength of the separator 2, reduce the heat of chemical reaction, avoid the problem of separator 2 failure caused by the shrinkage of the separator 2 along the needle hole, and thus improve the safety performance of the battery.

[0033] In some embodiments, the ratio of the thickness of the fluorinated carbon material layer 22 to the thickness of the lithium replenishment layer 13 is 1:(0.1 to 100). When the ratio of the thickness of the fluorinated carbon material layer 22 to the thickness of the lithium replenishment layer 13 is within the above range, the liquid retention capacity of the negative electrode is improved, and the energy density of the secondary battery is higher.

[0034] For example, the ratio of the thickness of the fluorinated carbon material layer 22 to the thickness of the lithium replenishment layer 13 can be 1:0.1, 1:1, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100 or any range of two sets of values.

[0035] In some embodiments, the thickness of the fluorinated carbon material layer 22 is 0.1 to 10 μm.

[0036] For example, the thickness of the fluorinated carbon material layer 22 can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or any two of these values.

[0037] In some embodiments, the fluorocarbon material layer 22 includes fluorocarbon material, and the particle size Dv50 of the fluorocarbon material is 1 nm to 8 μm.

[0038] For example, the particle size Dv50 of the fluorocarbon material can be 1nm, 10nm, 50nm, 100nm, 500nm, 800nm, 1μm, 5μm, 6μm, 7μm, 8μm, or a range of any two sets of values ​​therein.

[0039] It is understood that the particle size Dv50 of the fluorocarbon material is smaller than the thickness of the fluorocarbon material layer.

[0040] In some embodiments, the fluorocarbon material layer 22 includes fluorocarbon material and a binder, wherein the mass percentage of the fluorocarbon material in the fluorocarbon material layer 22 is 90-99%, and the mass percentage of the binder in the fluorocarbon material layer 22 is 1-10%.

[0041] Fluorinated carbon materials can be materials known in the art that consist of fluorine and carbon elements, wherein the molar ratio of fluorine to carbon elements is (0.2 to 1.2):1. For example, fluorinated carbon materials include at least one of fluorinated graphite, fluorinated activated carbon, fluorinated carbon black, fluorinated carbon nanotubes, fluorinated carbon fibers, fluorinated graphene, and fluorinated graphene oxide.

[0042] In some embodiments, the thickness of the diaphragm 2 is 5–25 μm.

[0043] For example, the thickness of the diaphragm 2 can be 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm or any range of two sets of values.

[0044] In some embodiments, the porosity of the diaphragm 2 is 20-80%.

[0045] For example, the porosity of the membrane 2 can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any two of these values.

[0046] In some embodiments, the thickness of the first ceramic layer 23 is 0.5 to 5 μm.

[0047] For example, the thickness of the first ceramic layer 23 can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or any two of these values.

[0048] In some embodiments, the first ceramic layer 23 includes a ceramic material, wherein the particle size Dv50 of the ceramic material in the first ceramic layer 23 is 0.01 to 2 μm.

[0049] It is understandable that the particle size Dv50 of the ceramic material in the first ceramic layer 23 is smaller than the thickness of the first ceramic layer 23.

[0050] For example, the particle size Dv50 of the ceramic material in the first ceramic layer 23 can be 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm or any two of these values.

[0051] In some embodiments, the first ceramic layer 23 includes a ceramic material and a binder, wherein the mass percentage of the ceramic material in the first ceramic layer 23 is 90-99%, and the mass percentage of the binder in the first ceramic layer 23 is 1-10%.

[0052] In some embodiments, the separator 2 further includes a lithiophilic layer 24 disposed between the fluorocarbon material layer 22 and the base film 21, and the thickness of the lithiophilic layer 24 is 0.1 to 3 μm.

[0053] For example, the thickness of the lithiophilic layer 24 can be 0.1, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or any two of these values.

[0054] This application provides a lithiophilic layer 24 between the fluorinated carbon material layer 22 and the base film 21, which can effectively promote uniform lithium deposition, avoid the phenomenon of dead lithium, and thus improve the safety and cycle performance of the battery cell.

[0055] In some embodiments, the material of the lithiophilic layer 24 includes at least one of Zn, Al, In, Sn, Au, Ag, Ti, Si, MgF2, LiF2, LiI, MgI2, Li3N, and ZnO.

[0056] In this application, the lithiophilic layer 24 can be formed on the base film 21 by existing magnetron sputtering process.

[0057] In some embodiments, the diaphragm 2 further includes a second ceramic layer 25, which is disposed between the fluorinated carbon material layer 22 and the base membrane 21. The thickness of the second ceramic layer 25 is 0.5 to 5 μm, and the second ceramic layer 25 includes ceramic material. The particle size Dv50 of the ceramic material in the second ceramic layer 25 is 0.01 to 2 μm.

[0058] For example, the thickness of the second ceramic layer 25 can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or any two of these values.

[0059] It is understandable that the particle size Dv50 of the ceramic material in the second ceramic layer 25 is smaller than the thickness of the second ceramic layer 25.

[0060] For example, the particle size Dv50 of the ceramic material in the second ceramic layer 25 can be 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 2μm or any two of these values.

[0061] This application improves the thermal stability and mechanical strength of the separator 2 by setting a second ceramic layer 25 between the fluorocarbon material layer 22 and the base film 21, thereby improving the safety of the battery cell.

[0062] The second ceramic layer 25 includes ceramic material and binder. The ceramic material in the second ceramic layer 25 has a mass percentage content of 90-99%, and the binder in the second ceramic layer 25 has a mass percentage content of 1-10%.

[0063] In some embodiments, the lithium replenishment layer 13 in the negative electrode 1 is made of Li.

[0064] In this application, the lithium replenishment layer 13 can be formed on the negative electrode active material layer 12 by existing rolling or evaporation lithium replenishment processes.

[0065] In some embodiments, the negative current collector 11 in the negative electrode 1 may be a copper foil.

[0066] In some embodiments, the negative electrode active material layer 12 may include the following components by weight percentage: 96-98.5% negative electrode active material, 0.5-1% conductive agent, 0.5-2% binder and 0.5-2% thickener.

[0067] The negative electrode active material also includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon, silicon oxide, and silicon-carbon composite.

[0068] In some embodiments, the positive electrode 3 includes a positive current collector 31, and a positive active material layer 32 is disposed on at least one side surface of the positive current collector 31.

[0069] The positive current collector 31 is a metal foil, which can be aluminum foil.

[0070] The positive electrode active material layer 32 may include the following components in weight percentage: 95-98.5% positive electrode active material, 0.5-3% conductive agent, and 1-2% binder.

[0071] The positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, transition metal phosphate, and lithium iron phosphate.

[0072] In this application, the base film 21 is made of at least one of polypropylene, polyethylene, and nonwoven fabric.

[0073] In this application, the ceramic material in the first ceramic layer 23 and the ceramic material in the second ceramic layer 25 each independently include at least one of alumina, silicon oxide, titanium oxide, zirconium oxide, barium oxide, boehmite, magnesium oxide and magnesium hydroxide.

[0074] In this application, the conductive agent in the positive electrode active material layer 32 and the conductive agent in the negative electrode active material layer 12 each independently include at least one of conductive carbon black, graphite, carbon nanofibers, and carbon nanotubes.

[0075] In this application, the binder in the fluorocarbon material layer 22, the binder in the first ceramic layer 23, the binder in the second ceramic layer 25, the binder in the positive electrode active material layer 32, and the binder in the negative electrode active material layer 12 each independently include at least one of polyvinylidene fluoride, polyacrylic acid, polyvinylidene fluoride, styrene-butadiene rubber, chloroprene rubber, polyacrylate, and sodium hydroxymethyl cellulose.

[0076] In a second aspect of this application, a secondary battery is provided, including the battery cell provided in the first aspect of this application.

[0077] In a third aspect of this application, an electrical device is provided, including the secondary battery provided in the second aspect of this application.

[0078] The inventors conducted numerous research experiments during the research process, including designing and fabricating different secondary batteries and testing their performance. Some of the experimental examples and test results are listed below to illustrate this application:

[0079] Example 1

[0080] Please see Figure 3 This embodiment provides a secondary battery including a cell, the cell including a negative electrode 1, a separator 2 and a positive electrode 3, the separator 2 being disposed between the negative electrode 1 and the positive electrode 3, the negative electrode 1 including a negative current collector 11, a negative active material layer 12 and a lithium replenishment layer 13 arranged sequentially; the positive electrode 3 including a positive current collector 31 and a positive active material layer 32 arranged sequentially; the separator 2 including a first ceramic layer 23, a base film 21, a second ceramic layer 25, a lithiophilic layer 24 and a fluorinated carbon material layer 22 arranged sequentially, the first ceramic layer 23 being adjacent to and in contact with the positive active material layer 32, and the fluorinated carbon material layer 22 being adjacent to and in contact with the lithium replenishment layer 13.

[0081] The thickness of the positive electrode active material layer 32 is 70 μm, and the thickness of the negative electrode active material layer 12 is 50 μm.

[0082] The thicknesses of the fluorinated carbon material layer 22, the lithium replenishment layer 13, the first ceramic layer 23, the lithiophilic layer 24, and the second ceramic layer 25 are shown in Table 1.

[0083] The preparation method of the secondary battery is as follows:

[0084] S1. Preparation of the diaphragm:

[0085] S11. Select a polyethylene wet-process membrane with a thickness of 5μm and a porosity of 38% as the base membrane.

[0086] S12. Grind the alumina powder and sieve it to obtain ceramic material with a particle size Dv50 of 0.8μm;

[0087] Ceramic materials and binder polyacrylic acid are mixed at a mass ratio of 95:5 and added to deionized water to prepare a ceramic slurry with a solid content of 35%. The ceramic slurry is coated on one side of the diaphragm and dried to obtain the first ceramic layer. The ceramic slurry is coated on the other side of the diaphragm and dried to obtain the second ceramic layer.

[0088] S13. A lithium-loving layer of Al material is formed on the second ceramic layer by magnetron sputtering.

[0089] S14. Fluorographite and binder polyacrylic acid are mixed at a mass ratio of 95:5 and added to deionized water to prepare a fluorographite slurry with a solid content of 30%. The fluorographite slurry is coated on a lithiophilic layer and dried to obtain a fluorinated carbon material layer.

[0090] S2, Preparation of the negative electrode sheet:

[0091] Graphite, silicon carbide (SiC), conductive carbon nanotubes (CNTs), binder polyacrylic acid (PAA), and sodium carboxymethyl cellulose (CMC) were thoroughly mixed in a deionized water solvent at a mass ratio of graphite:SiC:CNT:PAA:CMC = 85:12:1:1.2:0.8 to obtain a negative electrode slurry with a solid content of 40%. The negative electrode slurry was coated onto a current collector copper foil, dried at 85°C, and then cold-pressed to form a negative electrode active material layer. The material was then trimmed and slit, and dried under vacuum at 85°C for 12 hours. Under a low humidity environment with an ambient relative humidity of 3%, lithium strips were rolled and laminated onto the negative electrode active material layer using a lithium supplementation method to obtain a lithium supplementation layer. Finally, electrode tabs were welded under low humidity conditions to obtain the negative electrode sheet.

[0092] S3. Preparation of the positive electrode sheet:

[0093] The positive electrode active material LiCoO2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in N-methylpyrrolidone solvent (NMP) at a mass ratio of 97:2:1 to obtain a positive electrode slurry with a solid content of 70%. The positive electrode slurry was coated on a current collector aluminum foil, dried at 85°C, cold-pressed, trimmed and slit, dried under vacuum at 85°C for 6 hours, and then the tabs were welded to obtain the positive electrode sheet.

[0094] S4. Preparation of electrolyte:

[0095] Lithium hexafluorophosphate (LiPF6) was dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) (mass ratio of DMC, EC, and EMC was 3:5:2) to obtain the electrolyte.

[0096] S5. Preparation of secondary batteries:

[0097] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and then wound to obtain a battery cell. The battery cell is placed in an aluminum-plastic film outer packaging for sealing, and then baked in an 85°C vacuum oven for 48 hours. Electrolyte is injected into the dried battery, followed by sealing, settling, formation, shaping, and capacity testing, and then a second sealing to obtain the rechargeable battery.

[0098] Examples 2-7

[0099] The difference between Examples 2-7 and Example 1 is that the thickness of each layer in Examples 2-7 is shown in Table 1.

[0100] Example 8

[0101] The difference between this embodiment and Embodiment 1 is that, please refer to... Figure 1In this embodiment, the second ceramic layer 25 and the lithiophilic layer 24 are not provided.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that this comparative example does not have a fluorinated carbon material layer 22, and the thickness of the lithium replenishment layer 13 is shown in Table 1.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is that this comparative example does not have a fluorinated carbon material layer 22.

[0106] Table 1

[0107]

[0108] In Table 1, " / " indicates that no corresponding structural layer has been set.

[0109] Performance testing

[0110] The performance of the secondary batteries in the above embodiments and comparative examples was tested using the following methods:

[0111] (1) Liquid retention: In the secondary battery preparation process of the above embodiments and comparative examples, the cell weight was weighed before the electrolyte injection step and after the second sealing step, and the liquid retention was calculated by the following formula: Liquid retention = cell weight after second sealing + air bag weight - cell weight before liquid injection.

[0112] (2) Energy density: Discharge capacity (Ah) is obtained by discharging at a constant current of 0.2C to the cutoff voltage of 3.0V; the energy density calculation formula is: energy density = discharge capacity × working voltage / battery volume.

[0113] (3) First-time effect: The first-time effect is calculated according to the following formula: First-time effect = First-time discharge capacity / First-time charge capacity * 100%. The first-time charge and discharge capacity here refers to the first-time charge capacity and first-time discharge capacity generated during battery formation and capacity grading. The capacity grading cabinet is used for testing. The capacity grading process is as follows: 0.5C constant current charging, cutoff voltage 4.53V; 4.53V constant voltage charging, cutoff current 0.025C; rest for 5 minutes; 0.2C constant current discharge, cutoff voltage 3.0V; 0.5C constant current charging, cutoff voltage 4.0V.

[0114] The test results are shown in Table 2.

[0115] Table 2

[0116] project Liquid retention (g) Energy density (Wh / L) First-efficacy (%) Example 1 9.8 831 92.9 Example 2 9 813 91.6 Example 3 10.2 809 92.8 Example 4 10.4 795 91.0 Example 5 9.2 815 91.7 Example 6 9.7 820 92.7 Example 7 10.3 805 92.3 Example 8 9.4 828 92.7 Comparative Example 1 8.8 803 90.2 Comparative Example 2 9.1 810 90.8

[0117] As can be seen from Table 2, this application places the fluorinated carbon material layer between the base film and the lithium replenishment layer of the negative electrode sheet, which can significantly improve the liquid retention of the secondary battery while ensuring the battery energy density and first efficiency.

[0118] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A battery cell, characterized in that, The device includes a negative electrode sheet, a separator, and a positive electrode sheet. The separator is disposed between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet includes a negative current collector, a negative active material layer, and a lithium replenishment layer disposed sequentially. The negative active material layer is located between the negative current collector and the lithium replenishment layer. The separator comprises a fluorinated carbon material layer, a base film, and a first ceramic layer arranged sequentially. The fluorinated carbon material layer is located between the base film and the lithium replenishment layer, and the first ceramic layer is located between the base film and the positive electrode sheet.

2. The battery cell as described in claim 1, characterized in that, The ratio of the thickness of the fluorinated carbon material layer to the thickness of the lithium replenishment layer is 1:(0.1~100).

3. The battery cell as described in claim 2, characterized in that, The thickness of the fluorinated carbon material layer is 0.1–10 μm; And / or, the fluorocarbon material layer comprises fluorocarbon material, wherein the particle size Dv50 of the fluorocarbon material is 1 nm to 8 μm.

4. The battery cell as described in claim 1, characterized in that, The thickness of the diaphragm is 5–25 μm; And / or, the porosity of the diaphragm is 20-80%.

5. The battery cell as described in claim 1, characterized in that, The thickness of the first ceramic layer is 0.5–5 μm; And / or, the first ceramic layer comprises a ceramic material, wherein the particle size Dv50 of the ceramic material in the first ceramic layer is 0.01 to 2 μm.

6. The battery cell as described in claim 1, characterized in that, The membrane further includes a lithiophilic layer disposed between the fluorinated carbon material layer and the base membrane, the lithiophilic layer having a thickness of 0.1–3 μm.

7. The battery cell as described in claim 1, characterized in that, The membrane further includes a second ceramic layer disposed between the fluorinated carbon material layer and the base membrane.

8. The battery cell as described in claim 7, characterized in that, The thickness of the second ceramic layer is 0.5–5 μm; And / or, the second ceramic layer comprises a ceramic material, wherein the particle size Dv50 of the ceramic material in the second ceramic layer is 0.01 to 2 μm.

9. A secondary battery, characterized in that, Includes the battery cell as described in any one of claims 1 to 8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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