Battery cell and preparation method therefor, battery device, and electric device

Abstract

Disclosed in the present application are a battery cell and a preparation method therefor, a battery device, and an electric device. The battery cell comprises: a first electrolyte, which comprises a carbonate solvent; and a negative-electrode composite electrode sheet, which comprises a negative electrode sheet and a solid-state electrolyte film, wherein the solid-state electrolyte film is located on a surface of the negative-electrode composite electrode sheet, the negative-electrode composite electrode sheet is formed by subjecting the negative electrode sheet to a film-forming treatment in a second electrolyte so as to form the solid-state electrolyte film on the surface of the negative electrode sheet, and the second electrolyte comprises one or more of an ether solvent and a sulfone solvent.

Description

Battery cells and their preparation methods, battery devices and electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411180055.5, filed on August 27, 2024, entitled “Battery cell and method of preparation thereof, battery device and power consumption device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to a battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0004] Battery cells possess characteristics such as high capacity and long lifespan, making them widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. As the application of battery cells becomes increasingly widespread, users are placing higher performance demands on them.

[0005] To improve the performance of individual battery cells, the negative electrode within the cell is typically optimized and improved. However, currently, when negative electrode plates are used in individual battery cells, the electrochemical performance of the cells remains relatively poor. Summary of the Invention

[0006] This application provides a battery cell and its preparation method, a battery device, and an electrical device, which enable the battery cell to have good cycle life and good dynamic performance.

[0007] In a first aspect, embodiments of this application provide a single battery cell, comprising:

[0008] The first electrolyte includes a carbonate solvent;

[0009] A negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, wherein the solid electrolyte membrane is located on the surface of the negative electrode. The negative electrode composite electrode is formed by performing a film-forming treatment on the negative electrode in a second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode. The second electrolyte includes one or more of ether solvents and sulfone solvents.

[0010] In this embodiment, the negative electrode sheet is treated in a second electrolyte system using a first electrolyte system comprising ether solvents and / or sulfone solvents to obtain a solid electrolyte membrane. This solid electrolyte membrane has better stability and elasticity than a solid electrolyte membrane obtained in a carbonate solvent, and has good affinity for active ions. This results in improved kinetic and cycle performance for the battery cell containing the negative electrode sheet, the solid electrolyte membrane, and the first electrolyte.

[0011] Furthermore, performing a film-forming treatment in the second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode can overcome the problem that battery cells are prone to decomposition at high voltages (e.g., >4.0V) when using ether-based electrolytes. This solid electrolyte membrane can achieve higher rate performance in carbonate solvents.

[0012] In summary, the battery cell includes the first electrolyte and the solid electrolyte membrane described above, and the battery cell has good cycle capacity stability and kinetic performance.

[0013] In some optional embodiments, the ether solvent includes one or more of 1,2-dimethoxypropane, 1,2-dimethoxyethylene, tetrahydrofuran, 1,3-dioxocyclopentane, dipentyl ether, dimethyl ethyl ether, di(2-methoxyethyl) ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. The second electrolyte containing the ether solvent improves the composition and thickness of the SEI film, thereby enhancing the kinetic performance and cycle life of the battery cells.

[0014] In some optional embodiments, the sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, ethyl methyl sulfone, diphenyl sulfone, methanesulfonylmethane, and dimethyl sulfone. The second electrolyte containing a sulfone solvent improves the composition and thickness of the SEI film, thereby enhancing the kinetic performance and cycle life of the battery cell.

[0015] In some alternative embodiments, the conductivity of the first electrolyte is from 5 ms / cm to 12 ms / cm.

[0016] In the embodiments of this application, the conductivity of the first electrolyte is within the aforementioned range, which enables more effective conduction of lithium ions or other active ions, reduces ion transport resistance within the battery, improves rate performance, and provides a more uniform electric field distribution, thereby enhancing the overall electrochemical performance of the battery cell. In some optional embodiments, the conductivity of the first electrolyte is between 7 ms / cm and 10 ms / cm.

[0017] In some optional embodiments, the negative electrode sheet includes a negative electrode active material film layer, the areal density of which is 150–300 mg / 1540.25 mm². 2 .

[0018] In the embodiments of this application, the areal density of the negative electrode active material film layer is within the above range, which can optimize the electrode structure, make the ion and electron transport paths shorter and more uniform, reduce the internal resistance of the battery cell, enhance the performance of the battery cell under high-rate discharge conditions, and improve the dynamic performance of the battery cell.

[0019] In some optional embodiments, the negative electrode sheet includes a negative electrode active material film layer, the compaction density of which is 1.3 g / cm³. 3 Up to 1.7 g / cm 3 .

[0020] In the embodiments of this application, the compacted thickness of the negative electrode active material film layer is within the above-mentioned range, which improves the material volume utilization rate and thus increases the energy density of the battery. The compacted density of the negative electrode active material film layer within the above-mentioned range can improve the mechanical strength of the electrode material, reduce material pulverization and shedding during charging and discharging, reduce the internal resistance of the battery cell, improve the electron and ion transport efficiency, and balance the kinetic performance, cycle stability, and lifespan of the battery cell.

[0021] In some optional embodiments, the thickness of the solid electrolyte membrane is from 2 nm to 90 nm. This improves the ionic conductivity of the solid electrolyte membrane and enhances the kinetic performance of the battery cell.

[0022] In some optional embodiments, the membrane impedance of the solid electrolyte membrane is from 0.01 to 15 Ω. Therefore, the active ion throughput rate of the solid electrolyte membrane is improved, as are the ionic conductivity and fast charging capability of the battery cell, thereby enhancing the kinetic performance of the battery cell.

[0023] In some optional embodiments, the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, and methyl acetate.

[0024] In this embodiment, the negative electrode composite electrode exhibits better specific capacity in carbonate-based electrolytes including those described above, and the polarization of the battery single-layer charge-discharge curve is lower. That is, the solid electrolyte membrane in the negative electrode composite electrode has good stability. Furthermore, the solid electrolyte membrane in this negative electrode composite electrode hardly decomposes under high voltage, improving the specific capacity and cycle life of the battery cell.

[0025] In some alternative embodiments, the operating voltage of the battery cell is from 2.5V to 4.4V. This increases the energy density of the battery cell.

[0026] In some optional embodiments, the battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive active material film layer, the positive active material film layer includes a positive active material, and the positive active material includes a lithium-containing transition metal oxide material. This allows the battery cell to operate at a relatively high voltage, and the formed solid electrolyte film exhibits good stability.

[0027] Secondly, embodiments of this application provide a method for preparing a single battery cell, comprising:

[0028] A negative electrode is processed in an environment including a second electrolyte to obtain a negative electrode composite electrode, wherein the negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, and the second electrolyte includes one or more of ether solvents and sulfone solvents.

[0029] The first electrolyte and the negative electrode composite sheet are assembled to obtain a battery cell, wherein the first electrolyte includes a carbonate solvent.

[0030] In the embodiments of this application, the negative electrode sheet is treated with a first electrolyte system including ether solvents and / or sulfone solvents to obtain a solid electrolyte membrane. This solid electrolyte membrane has better stability and elasticity than the solid electrolyte membrane obtained in carbonate solvents, and has a good affinity for active ions. As a result, the battery cell containing the negative electrode sheet, the solid electrolyte membrane and the first electrolyte has improved kinetic performance.

[0031] Furthermore, performing a film-forming treatment in the second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode can overcome the problem that battery cells are prone to decomposition at high voltages (e.g., >4.0V) when using ether-based electrolytes. This solid electrolyte membrane can achieve higher rate performance in carbonate solvents.

[0032] In summary, the battery cell includes the first electrolyte and the solid electrolyte membrane described above, and the battery cell has good cycle capacity stability and kinetic performance.

[0033] In some optional embodiments, the thickness of the solid electrolyte membrane is ≤2 nm. Therefore, the ionic conductivity of the solid electrolyte membrane is improved, thereby enhancing the kinetic performance of the battery cell.

[0034] Thirdly, embodiments of this application provide a battery device, including a battery cell according to the first aspect of this application or a battery cell prepared by the preparation method according to the second aspect of this application.

[0035] The battery device provided in this application therefore has at least the same advantages as the battery cell.

[0036] Fourthly, embodiments of this application provide an electrical device, including a battery cell of the first aspect or a battery cell prepared by the preparation method of the second aspect.

[0037] The electrical device of this application includes the battery device provided in this application, and therefore has at least the same advantages as the battery device. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0039] Figure 1 is a schematic diagram of one embodiment of the battery cell of this application.

[0040] Figure 2 is a schematic diagram of one embodiment of the battery module of this application.

[0041] Figure 3 is a schematic diagram of one embodiment of the battery pack of this application.

[0042] Figure 4 is an exploded view of an embodiment of the battery pack shown in Figure 3.

[0043] Figure 5 is a schematic diagram of one embodiment of an electrical device that uses the battery of this application as a power source.

[0044] The accompanying drawings are not necessarily drawn to scale.

[0045] The following are the annotations in the attached diagram: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Individual battery cell. Detailed Implementation

[0046] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its preparation method, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0047] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0049] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0050] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0051] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0052] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0053] The battery device mentioned in the embodiments of this application may include a single physical module containing one or more battery cells to provide higher voltage and capacity. For example, the battery device mentioned in this application may include battery cells, battery modules, or battery packs.

[0054] In some alternative implementations, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc. The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0055] In some alternative implementations, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0056] In some alternative embodiments, the battery device may be a battery pack, which may include a housing and one or more individual battery cell assemblies housed within the housing. In some alternative embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0057] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0058] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0059] A battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 1 shows a cuboid battery cell 5 as an example.

[0060] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some alternative implementations, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module.

[0061] In some alternative implementations, battery cells can be assembled into a battery module. The number of battery cells in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 2 is a schematic diagram of a battery module 4 as an example. As shown in Figure 2, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0062] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0063] In some alternative implementations, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0064] Figures 3 and 4 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 3 and 4, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 and forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0065] The active ion in this application can be lithium ion. The battery cells provided in the embodiments of this application can include lithium-ion battery cells, lithium metal battery cells, and negative electrode-less lithium metal battery cells, etc. The battery cells provided in the embodiments of this application can be secondary batteries, primary batteries, etc. The specific type of battery cell will result in differences in the structure and composition of the negative electrode.

[0066] The battery cell provided in this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a separator, and a negative electrode. The electrode assembly can be a wound structure or a stacked structure; this application is not limited in this regard. The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and the electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as one or more of aluminum-plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0067] To improve battery life and dynamic performance, existing solutions often involve reducing the thickness of the positive electrode active material film or coating on the positive electrode sheet. These measures often reduce the battery's energy density. Alternatively, highly conductive electrolytes can be used to improve the battery system, but highly conductive electrolytes also lead to a significant increase in costs.

[0068] In some alternative implementations, this application provides a battery cell, comprising:

[0069] The first electrolyte includes a carbonate solvent;

[0070] A negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, wherein the solid electrolyte membrane is located on the surface of the negative electrode. The negative electrode composite electrode is formed by performing a film-forming treatment on the negative electrode in a second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode. The second electrolyte includes one or more of ether solvents and sulfone solvents.

[0071] In this embodiment, the negative electrode sheet is treated in a second electrolyte system using a first electrolyte system comprising ether solvents and / or sulfone solvents to obtain a solid electrolyte membrane. This solid electrolyte membrane has better stability and elasticity than a solid electrolyte membrane obtained in a carbonate solvent, and has good affinity for active ions. This results in improved kinetic and cycle performance for the battery cell containing the negative electrode sheet, the solid electrolyte membrane, and the first electrolyte.

[0072] Furthermore, performing a film-forming treatment in the second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode can overcome the problem that battery cells are prone to decomposition at high voltages (e.g., >4.0V) when using ether-based electrolytes. This solid electrolyte membrane can achieve higher rate performance in carbonate solvents.

[0073] In summary, the battery cell includes the first electrolyte and the solid electrolyte membrane described above, and the battery cell has good cycle capacity stability and kinetic performance.

[0074] The negative electrode composite electrode is formed by performing a film-forming treatment on the negative electrode in a second electrolyte to composite the solid electrolyte membrane (SEI membrane) on the surface of the negative electrode. This treatment can adjust the initial thickness and composition of the SEI membrane. Compared with the SEI membrane formed in the first electrolyte, the SEI membrane formed in the second electrolyte is thinner, about 2 nm, and also has better stability and elasticity. The compositional difference between the two SEI membranes is that the ratio of organic to inorganic components in the SEI membrane formed in electrolytes containing ether and sulfone solvents is greater than that in the SEI membrane formed in carbonate solvents. This difference determines that the SEI membrane formed in electrolytes containing ether and sulfone solvents in the negative electrode composite electrode has better active ion transport capacity and active ion insertion / extraction rate. A detailed analysis follows:

[0075] Generally, SEI films typically exhibit a bilayer structure, with an outer layer composed of porous organic components and an inner layer composed of dense inorganic components. Taking Li as an example... + Taking this active ion as an example, Li + The diffusion in the outer layer is mainly characterized by porous electrode diffusion, while the diffusion in the inner inorganic layer is characterized by grain boundary diffusion. Taking an ether-based electrolyte containing ether solvents and a graphite negative electrode as an example, the negative electrode composite sheet formed after the battery cell formation can be understood as having an SEI film on the graphite surface. This SEI can be pre-cycled in an ester electrolyte containing carbonate solvents at rates of 0.1, 0.2, 0.5, and 1C to form an SEI, thus improving the specific capacity of the battery cell and resulting in lower polarization in the battery charge-discharge curve. In summary, this negative electrode composite sheet improves the specific capacity of the battery cell.

[0076] For example, the proportion of LF material in the SEI film formed in ether-based electrolytes is much higher than that in the SEI film formed in ester-based electrolytes. This indicates that the SEI film composition in ester-based electrolytes mainly originates from the products of ether solvent decomposition, while the SEI film composition in ether-based electrolytes is mainly dominated by lithium salts such as LiTFSI, LiNO3, and LiPF6. The SEI film composition in ether-based electrolytes is mainly composed of organic compounds, while the content of inorganic compounds is much lower than that in ester-based electrolytes. Compared with the inorganic matter contained in the SEI film, the thin organic matter in the SEI film gives the negative electrode better flexibility, makes stress concentration less likely to occur inside the SEI film, and allows the SEI film to withstand Li more stably. + The volume change during the insertion / extraction process leads to better cycle stability.

[0077] The chemical composition of the SEI film can be analyzed using X-ray photoelectron spectroscopy (XPS). The differences in the content of organic and inorganic components can characterize the differences in film formation of different solvents.

[0078] In some optional embodiments, in order to improve the composition and thickness of the SEI film and enhance the kinetic performance and cycle life of the battery cell, the ether solvent includes one or more of 1,2-dimethoxypropane, 1,2-dimethoxyethylene, tetrahydrofuran, 1,3-dioxocyclopentane, dipentyl ether, dimethyl ethyl ether, di(2-methoxyethyl) ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

[0079] For example, 1,2-dimethoxypropane (DMP), as a chain-like ether solvent, participates in the formation of the SEI film and can form the outer organic component, giving the SEI film good electrochemical stability. The SEI film can exist stably over a wide voltage range, protecting the electrode from further decomposition and side reactions.

[0080] In some optional embodiments, in order to improve the composition and thickness of the SEI film and enhance the kinetic performance and cycle life of the battery cell, the sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, ethyl methyl sulfone, diphenyl sulfone, methanesulfonylmethane, and dimethyl sulfone.

[0081] In some optional embodiments, the conductivity of the first electrolyte is from 5 mS / cm to 12 mS / cm. Optionally, the conductivity of the first electrolyte can be any value or a range thereof from 5 mS / cm, 6 mS / cm, 7 mS / cm, 8 mS / cm, 9 mS / cm, 10 mS / cm, 11 mS / cm, and 12 mS / cm. In some optional embodiments, the conductivity of the first electrolyte is from 7 mS / cm to 10 mS / cm.

[0082] In the embodiments of this application, the conductivity of the first electrolyte is within the above-mentioned range, which can more effectively conduct lithium ions or other active ions, reduce the ion transport resistance inside the battery, improve rate performance, and provide a more uniform electric field distribution, thereby improving the overall electrochemical performance of the battery cell.

[0083] In this application, the conductivity of the electrolyte has a meaning known in the art and can be tested using methods known in the art, such as a conductivity meter. An exemplary test method is as follows: using a conductivity meter (e.g., Leici DDSJ-318), at 25°C and an AC impedance of 1kHz, the resistance of the electrolyte is tested, and the conductivity of the electrolyte is calculated.

[0084] In some optional embodiments, the negative electrode sheet includes a negative electrode active material film layer, the areal density of which is 150 g / 1540.25 mm². 2 Up to 300g / 1540.25mm 2 .

[0085] Optionally, the areal density of the negative electrode active material film can be 150 g / 1540.25 mm². 2 160g / 1540.25mm 2 170g / 1540.25mm 2 180g / 1540.25mm 2 190g / 1540.25mm 2 200g / 1540.25mm 2 210g / 1540.25mm 2 220g / 1540.25mm 2 230g / 1540.25mm 2 240g / 1540.25mm 2 250g / 1540.25mm 2 260g / 1540.25mm 2 270g / mm 2 280g / 1540.25mm 2 290g / 1540.25mm 2 300g / 1540.25mm 2 Any value or range of its composition in [the specified value]. In some alternative embodiments, the areal density of the negative electrode active material film is 250 g / 1540.25 mm². 2 Up to 280g / 1540.25mm 2 .

[0086] In the embodiments of this application, the areal density of the negative electrode active material film layer is within the above range, which can optimize the electrode structure, making the ion and electron transport paths shorter and more uniform, thereby reducing the internal resistance of the battery, enhancing the performance of the battery cell under high-rate discharge conditions, and improving the dynamic performance of the battery cell.

[0087] The areal density of the negative electrode active material film is a term known in the art and can be measured using instruments and methods known in the art. For example, take a negative electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated negative electrode sheet, the negative electrode active material film on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh them, and record their weight as M1. Then wipe off the negative electrode active material film of the weighed negative electrode sheet, weigh the negative electrode current collector, and record it as M0. The areal density of the negative electrode active material film = (weight of the negative electrode sheet M1 - weight of the negative electrode current collector M0) / S1.

[0088] In some alternative embodiments, the negative electrode sheet includes a negative electrode active material film layer, the compaction density of which is 1.3 to 1.7 g / cm³. 3Optionally, the compaction density of the negative electrode active material film layer can be 1.3 g / cm³. 3 1.4g / cm 3 1.5g / cm 3 1.55g / cm 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 Any value or range of its composition in [the specified range]. In some alternative embodiments, the compaction density of the negative electrode active material film is 1.6 g / cm³. 3 Up to 1.65 g / cm 3 .

[0089] In the embodiments of this application, the compaction density of the negative electrode active material film layer is within the above range, which improves the material volume utilization rate and thus improves the energy density of the battery; it can also improve the mechanical strength of the electrode material, reduce the pulverization and shedding of the material during charging and discharging, reduce the internal resistance of the battery cell, improve the electron and ion transport efficiency, and take into account the dynamic performance, cycle stability and life of the battery cell.

[0090] The compaction density of the negative electrode active material film is a well-known concept in the art and can be measured using instruments and methods known in the art. For example, take a negative electrode sheet that has been coated on one side and cold-pressed, test the thickness of the negative electrode active material film, and then test the areal density of the negative electrode active material film using the method described above. The compaction density of the negative electrode active material film = areal density of the negative electrode active material film / thickness of the negative electrode active material film.

[0091] In some optional embodiments, to ensure that active ions have a suitable transport distance, reduce ion impedance, improve the ionic conductivity of the solid electrolyte membrane, and enhance the kinetic performance of the battery cell, the thickness of the solid electrolyte membrane is from 2 nm to 90 nm. Optionally, the thickness of the solid electrolyte membrane can be any value or a range thereof from 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, and 90 nm. The above-mentioned thickness of the solid electrolyte membrane can be understood as being obtained by disassembling and testing the composite negative electrode sheet from the battery cell after multiple electrochemical cycles.

[0092] The thickness of the solid electrolyte membrane can be measured using methods commonly used in the field, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). For example, the thickness of the solid electrolyte membrane can be measured at multiple sites in the composite negative electrode sheet; up to 20 points can be measured, and the average value taken.

[0093] In some optional embodiments, to improve the ionic conductivity and fast charging capability of the battery cell, and to enhance the active ion throughput rate of the solid electrolyte membrane, thereby improving the kinetic performance of the battery cell, the membrane impedance of the solid electrolyte membrane is from 0.01 to 15 Ω. Optionally, the impedance of the solid electrolyte membrane can be any value or a range of combinations thereof from 0.01 Ω, 0.02 Ω, 0.03 Ω, 0.04 Ω, 0.05 Ω, 0.06 Ω, 0.07 Ω, 0.08 Ω, 0.09 Ω, 0.1 Ω, 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω, 0.6 Ω, 0.7 Ω, 0.8 Ω, 0.9 Ω, 1 Ω, 2 Ω, 3 Ω, 4 Ω, 5 Ω, 6 Ω, 7 Ω, 8 Ω, 9 Ω, 10 Ω, 11 Ω, 12 Ω, 13 Ω, 14 Ω, and 15 Ω.

[0094] The impedance of the negative electrode composite sheet and the solid electrolyte membrane is a well-known concept in the art and can be tested using methods known in the art. For example, a BER1300 multifunctional electrode resistance meter and in-situ electrochemical impedance spectroscopy (In-situ EIS) can be used for testing. For example, first, the negative electrode composite sheet is cut into a test sample of a certain size; the resistance meter, pressure display power supply, and computer are turned on; the gas valve is opened; and the upper and lower copper probes are cleaned with lint-free paper soaked in alcohol. The computer software is then opened, the port, pressure, and test mode are selected, and the terminal test area of ​​154.02 mm² is entered. 2 Place the test electrode between the two probes and click the run button on the software to start the test. After the test, record the test result R1. To ensure the accuracy of the test results, five sets of test samples can be taken simultaneously, and the average value of these five sets of test samples can be calculated. Remove the solid electrolyte film on the surface of the negative electrode composite electrode, repeat the above steps, and measure the result R2. The impedance of the solid electrolyte film is the absolute value of R1-R2.

[0095] The impedance of any two circular areas with the same area and a center-to-center distance of 20cm on the negative electrode composite sheet can be tested using the test method described above, and the average value can be taken.

[0096] In some optional embodiments, the negative electrode sheet may include a negative current collector and a negative active material film layer located on at least one surface of the negative current collector. The negative active material film layer includes a negative active material, which may include one or more of lithium titanate, carbon-based materials, silicon-based materials, tin-based materials, and lithium metal.

[0097] Optionally, the carbon-based material may include, but is not limited to, one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres. Optionally, the silicon-based material may include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. Optionally, the tin-based material may include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy materials.

[0098] In some alternative embodiments, the negative electrode active material film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some alternative embodiments, the negative electrode active material film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0100] In some alternative embodiments, the negative electrode active material film layer may also include other additives. For example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0101] In some alternative embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, and nickel alloy foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0102] In some alternative embodiments, the negative electrode may include a negative current collector and a lithium metal layer disposed on at least one surface of the negative current collector.

[0103] Because lithium metal has a relatively high theoretical specific capacity, relatively low density, and a relatively negative electrode potential, using lithium metal as the negative electrode active material can significantly improve the energy density of a single battery cell. In this case, the battery cell can be called a lithium metal battery cell.

[0104] In some alternative implementations, the negative electrode may include a negative current collector but not a lithium metal layer. In this case, the battery cell may be referred to as a negative electrode-free lithium metal battery cell.

[0105] In some optional embodiments, the operating voltage of the battery cell is from 2.5V to 4.4V. Optionally, the operating voltage of the battery cell can be any value or a range of combinations thereof from 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, 3.0V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4.0V, 4.1V, 4.2V, 4.3V, 4.35V, and 4.4V. Therefore, the energy density of the battery cell can be improved.

[0106] [Positive electrode plate]

[0107] In some alternative embodiments, the positive electrode may include a positive current collector and a positive active material film layer disposed on at least one surface of the positive current collector, the positive active material film layer comprising a positive active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive active material film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0108] The positive electrode active material includes materials capable of extracting and inserting lithium. Optionally, the positive electrode active material may include, but is not limited to, one or more of lithium-containing phosphates and lithium transition metal oxides. Examples of lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0109] In some alternative embodiments, the battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive active material film layer, the positive active material film layer includes a positive active material, and the positive active material includes a lithium-containing transition metal oxide material.

[0110] Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and one or more of their respective modified compounds.

[0111] In some alternative implementations, as examples, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 0.5 Mn1.5 O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, and one or more of their respective modified compounds.

[0112] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0113] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell. The molar content of Li varies depending on the discharge state of the cell. In the above list of specific cathode active materials, the molar content of Li represents the initial state, i.e., the state before material addition. After charge-discharge cycles, the molar content of Li may change when the cathode active material is applied to the battery cell. Similarly, the molar content of oxygen (O) in the above list of specific cathode active materials is only a theoretical value. Oxygen release from the crystal lattice can cause changes in the molar content of O, which may fluctuate.

[0114] In some alternative embodiments, the positive electrode active material film layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some alternative embodiments, the positive electrode active material film layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0116] In some alternative embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0117] The positive electrode active material film layer can be formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0118] [Electrolytes]

[0119] In some embodiments, the battery cell includes an electrolyte. The electrolyte acts as a conductor of active ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. In some optional embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and carbonate solvents.

[0120] In some optional embodiments, the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, and methyl acetate.

[0121] In this embodiment, the negative electrode composite electrode exhibits better specific capacity in carbonate-based electrolytes including those described above, and the polarization of the battery single-layer charge-discharge curve is lower. That is, the solid electrolyte membrane in the negative electrode composite electrode has good stability. Furthermore, the solid electrolyte membrane in this negative electrode composite electrode hardly decomposes under high voltage, improving the specific capacity and cycle life of the battery cell.

[0122] There are no specific restrictions on the types of electrolyte salts; they can be selected according to actual needs.

[0123] For example, the electrolyte salt includes one or more selected from lithium salts for lithium-ion batteries and sodium salts for sodium-ion batteries. As an example, the lithium salt includes one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0124] In some alternative embodiments, the electrolyte may also optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0125] [Isolation membrane]

[0126] The separator is positioned between the positive and negative electrodes, primarily serving to prevent internal short circuits. This application does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected. In some optional embodiments, the separator material may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0127] In some alternative embodiments, the separator may further include a heat-resistant coating to improve its heat resistance. Optionally, the heat-resistant coating may include, but is not limited to, one or more of alumina, boehmite, silicon dioxide, zirconium dioxide, magnesium oxide, titanium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, and magnesium nitride.

[0128] This application also provides a method for preparing a battery cell, which can prepare the battery cell provided in this application.

[0129] [Preparation methods for battery cells]

[0130] This application provides a method for preparing a single battery cell, including:

[0131] A negative electrode is processed in an environment including a second electrolyte to obtain a negative electrode composite electrode, wherein the negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, and the second electrolyte includes one or more of ether solvents and sulfone solvents.

[0132] The first electrolyte and the negative electrode composite sheet are assembled to obtain a battery cell, wherein the first electrolyte includes a carbonate solvent.

[0133] In the embodiments of this application, the negative electrode sheet is treated with a first electrolyte system including ether solvents and / or sulfone solvents to obtain a solid electrolyte membrane. This solid electrolyte membrane has better stability and elasticity than the solid electrolyte membrane obtained in carbonate solvents, and has a good affinity for active ions. As a result, the battery cell containing the negative electrode sheet, the solid electrolyte membrane and the first electrolyte has improved kinetic performance.

[0134] Furthermore, performing a film-forming treatment in the second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode can overcome the problem that battery cells are prone to decomposition at high voltages (e.g., >4.0V) when using ether-based electrolytes. This solid electrolyte membrane can achieve higher rate performance in carbonate solvents.

[0135] In summary, the battery cell includes the first electrolyte and the solid electrolyte membrane described above, and the battery cell has good cycle capacity stability and kinetic performance.

[0136] In some optional embodiments, the thickness of the solid electrolyte membrane is ≤2 nm. Therefore, the ionic conductivity of the solid electrolyte membrane is improved, thereby enhancing the kinetic performance of the battery cell.

[0137] The aforementioned thickness of the solid electrolyte membrane can be understood as the thickness obtained after membrane treatment of the negative electrode, i.e., the thickness during the initial electrochemical cycle or the initial thickness. The thickness of the solid electrolyte membrane can be confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing that the SEI film formed on the graphite electrode surface in ether-based electrolytes is smoother and thinner (≤2 nm). A thinner SEI film is beneficial for Li… + It enables rapid transmission and achieves high-rate characteristics.

[0138] The preparation method of a battery cell includes the following steps: providing a positive electrode sheet, a separator, and a negative electrode composite sheet to assemble a battery cell to be injected with electrolyte, and injecting a second electrolyte into the battery cell to be injected with electrolyte to obtain a battery cell.

[0139] The preparation method of the battery cell to be injected with electrolyte is well known. In some alternative embodiments, the positive electrode sheet, the separator, and the negative electrode composite sheet with a solid electrolyte film can be formed into an electrode assembly by a winding process and / or a stacking process, and the electrode assembly is placed in an outer package to obtain the battery cell to be injected with electrolyte.

[0140] This application provides an electrical device, including a battery cell of the first aspect or a battery cell prepared by the second aspect.

[0141] Battery devices can be used as the power source for electrical devices or as energy storage units for electrical devices. Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0142] Electrical devices can choose the type of battery according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0143] Figure 5 is a schematic diagram of an example electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0144] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0145] Example

[0146] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0147] Example 1

[0148] Positive electrode plate: Positive electrode active material LiNi0.5 Co 0.3 Mn 0.2 O2, Superconducting Carbon Black (Super-P), and polyvinylidene fluoride powder were mixed in a mass ratio of 90:5:5 and added to N-methylpyrrolidone (NMP) solvent. The mixture was stirred until the system was uniformly dispersed, resulting in a positive electrode slurry with a solid solution content of 45%. Subsequently, the slurry was coated onto one side of aluminum foil using a coating machine and then rolled. Finally, the prepared positive electrode sheet was dried in a 70℃ vacuum drying oven for later use. The areal density of the positive electrode sheet film was 0.25 g / 1540.25 mm². 2 The compaction density of the positive electrode active material film is 3.2 g / cm³. 3 ;

[0149] Preparation of negative electrode composite sheet:

[0150] Preparation of the initial negative electrode sheet: A mixture of natural graphite and artificial graphite (mass ratio 1:1), conductive agent CNT, and binder CMC powder were prepared at a mass ratio of 96:2:2 to obtain a negative electrode slurry with a solid solution content of 69%. Subsequently, the slurry was coated onto one side of copper foil using a coating machine and then rolled. Finally, the prepared initial negative electrode sheet was dried in a 70℃ vacuum drying oven for later use. The areal density of the negative electrode active material film layer was 0.2 g / 1540.25 mm². 2 The compaction density of the negative electrode active material film is 1.5 g / cm³. 3 ;

[0151] Preparation of the second electrolyte: LiFSI and LiNO3 were dispersed in a solvent, 1,2-dimethoxypropane (DMP), with a LiFSI concentration of 1 mol / L and a LiNO3 concentration of 0.3 mol / L.

[0152] Film formation treatment: The initial negative electrode sheet is subjected to film treatment in the second electrolyte. Specifically, in a super-clean glove box, using the initial negative electrode sheet as the research electrode, 97% LiNi is loaded onto aluminum foil. 0.5 Co 0.3 Mn 0.2 O2 material is used as the counter electrode, and the copper foil diameter is 14 mm. 100 μL of fresh first electrolyte is injected to assemble a 2032 coin cell. The cell is then treated at 0.01-3V to obtain a negative electrode composite sheet containing a solid electrolyte membrane.

[0153] Preparation of lithium battery cells:

[0154] Separating membrane: 7μm thick polyethylene membrane with a porosity of 40%.

[0155] First electrolyte: LiPF6 is dispersed in a solvent, which is obtained by mixing dimethyl carbonate (DMC), ethylene carbonate (EC), and ethylene dimethyl carbonate (EMC) in a volume ratio of 1:2:7, and the concentration of LiPF6 is 1 mol / L.

[0156] Assembly: The positive electrode sheet, separator, and negative composite electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. They are then wound to obtain a bare cell. The bare cell is placed in an outer package, injected with the first electrolyte, and sealed to assemble a lithium-ion battery. After assembly, the battery is allowed to stand for 24 hours before testing.

[0157] Example 2

[0158] The preparation method and performance testing method of the battery cell are the same as those in Example 1, except that the composition of the second electrolyte is different. The solvent of the second electrolyte is different; it is dimethyl sulfoxide.

[0159] Example 3

[0160] The preparation method and performance testing method of the battery cell are the same as those in Example 1, except that the composition of the second electrolyte is different. The solvent of the second electrolyte is different; it is sulfolane.

[0161] Example 4

[0162] The preparation method and performance testing method of the battery cell are the same as those in Example 1, except that the composition of the second electrolyte is different. The solvent of the second electrolyte is different; it is tetrahydrofuran.

[0163] Example 5

[0164] The preparation method and performance testing method of the battery cell are the same as those in Example 1, except that the composition of the second electrolyte is different. The solvent of the second electrolyte is different; it is 1,2-dimethoxyethylene.

[0165] Example 6

[0166] The preparation method and performance testing method of the battery cell are the same as those in Example 1, except that the composition of the second electrolyte is different. The solvent of the second electrolyte is different; it is dipentyl ether.

[0167] Example 7

[0168] The preparation method and performance testing method of the battery cell are the same as those of Example 2, except that the composition of the first electrolyte is different.

[0169] The first electrolyte has a different solvent, consisting of diethyl carbonate (DEC), ethylene carbonate (EC), and ethylene dimethyl carbonate (EMC) in a volume ratio of 1:2:7.

[0170] Example 8

[0171] The preparation method and performance testing method of the battery cell are the same as those of Example 1, except that the composition of the second electrolyte is different.

[0172] The second electrolyte uses a different solvent, which is a mixture of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethylene dimethyl carbonate (EMC) in a volume ratio of 1:2:7. The first electrolyte also uses a different solvent; the second electrolyte uses 1,2-dimethoxypropane.

[0173] Example 9

[0174] The preparation method and performance testing method of the battery cell are the same as those of Example 1, except that the composition of the first electrolyte and the second electrolyte are different.

[0175] The first electrolyte has a different solvent, which is 1,3-dioxolane; the second electrolyte has a different solvent, which is obtained by mixing ethylene carbonate (EC) and ethylene dimethyl carbonate (EMC) in a volume ratio of 3:7.

[0176] Example 10

[0177] The preparation method and performance testing method of the battery cell are the same as those of Example 1, except that the composition of the first electrolyte and the second electrolyte are different.

[0178] The first electrolyte has a different solvent, namely 1,3-dioxolane; the second electrolyte has a different solvent, namely propylene carbonate (PC), diethyl carbonate (DEC), and ethylene dimethyl carbonate (EMC) in a volume ratio of 1:2:7.

[0179] Comparative Example 1

[0180] The difference between this comparative example and Example 1 lies in the preparation of the negative electrode sheet. In this example, no film-forming treatment is performed during the preparation of the negative electrode sheet for the lithium battery cell. The negative electrode sheet was prepared by mixing a mixture of natural graphite and artificial graphite (mass ratio 1:1), conductive agent CNT, and binder CMC powder in a mass ratio of 96:2:2 to obtain a negative electrode slurry with a solid solution content of 69%. Subsequently, the slurry was coated onto one side of a copper foil using a coating machine and then rolled. Finally, the prepared negative electrode sheet was dried in a 70°C vacuum drying oven for later use. The areal density of the negative electrode active material film layer was 0.2 g / 1540.25 mm². 2The compaction density of the negative electrode active material film is 1.5 g / cm³. 3 The first electrolyte is still used when preparing lithium battery cells.

[0181] Comparative Example 2

[0182] The difference between this comparative example and Example 1 is that the compositions of the first and second electrolytes are different. The preparation method and performance testing method of the battery cells are the same as in Example 1.

[0183] The second electrolyte uses a different solvent, which is a mixture of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethylene dimethyl carbonate (EMC) in a volume ratio of 1:2:7. The first electrolyte uses a different solvent, which is a mixture of ethylene carbonate (EC) and ethylene dimethyl carbonate (EMC) in a volume ratio of 3:7.

[0184] Comparative Example 3

[0185] The difference between this comparative example and Example 1 is that the composition of the second electrolyte is different. The type and amount of solvent in the second electrolyte are the same as those in the first electrolyte.

[0186] Comparative Example 4

[0187] The difference between this comparative example and Example 2 is that the composition of the second electrolyte is different. The type and amount of solvent in the second electrolyte are the same as those in the first electrolyte.

[0188] Test section

[0189] 1) Solid electrolyte membrane thickness measurement: Scanning electron microscopy (SEM) was used to measure the solid electrolyte membrane thickness at multiple sites in the composite negative electrode sheets of the examples and comparative examples after film formation. The thickness of the solid electrolyte membrane at 20 points was measured, and the average value was taken. In Comparative Example 1, after the battery cell was formed, the negative electrode sheet was removed from the rechargeable battery cell, and the thickness of the solid electrolyte membrane in the negative electrode sheet was measured.

[0190] 2) Detection of solid electrolyte membrane internal resistance: The battery cells of the parallel group of examples and comparative examples were subjected to electrochemical cycling. After 500 electrochemical cycles, the battery cells were disassembled, and the solid electrolyte membrane was removed. The differences in the solid electrolyte membrane in each battery cell were compared using a BER1300 multifunctional electrode resistance meter and in-situ electrochemical impedance spectroscopy (In-situ EIS). The results are shown in Table 1.

[0191] Table 1 compares the initial thickness of the solid electrolyte membranes in the examples and comparative examples, as well as the impedance of the solid electrolyte membranes after 500 cycles.

[0192] As shown in Table 1, the thickness of solid electrolyte membranes formed by ether solvents and sulfone solvents is smaller than that formed by carbonate solvents.

[0193] Table 1 shows that, after film formation treatment, the solid electrolyte membrane treated with sulfone solvents is slightly thinner than that treated with ether solvents. After 500 cycles of the battery cell, the impedance of the solid electrolyte membrane treated with sulfone solvents is lower than that of the solid electrolyte membrane treated with ether solvents, indicating that the solid electrolyte membrane formed by sulfone solvents is more beneficial to the kinetic performance of the battery cell.

[0194] Table 1 shows that after film formation, the solid electrolyte membrane treated with ether solvents is slightly thinner than that treated with carbonate solvents. After 500 cycles, the impedance of the solid electrolyte membrane treated with ether solvents is lower than that of the solid electrolyte membrane treated with carbonate solvents, indicating that the solid electrolyte membrane formed by ether solvents is more beneficial to the kinetic performance of the battery cell.

[0195] 3) Battery cell dynamic performance (3C rate performance) test: At 25℃, the battery is charged at a constant current of 1C to the charging cutoff voltage of 4.4V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. The actual capacity is recorded as C0. Then the battery is charged sequentially at constant currents of 0.1C0, 0.5C0, 1C0, 2C0, and 3C0 to the full battery charging cutoff voltage of 4.4V or the 0V negative terminal cutoff potential (whichever comes first). After each charging, the battery is discharged at 0.33C0 to the full battery discharge cutoff voltage of 2.5V. The cycle is repeated five times at each rate, and the capacity after 15 cycles is recorded as C1. C1 / C0 is recorded as the 3C rate performance.

[0196] 4) Battery cell cycle capacity retention rate test: At 25℃, the battery is charged at a constant current of 1C to the charging cutoff voltage of 4.4V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. The actual capacity is recorded as C0. Then, the battery cell is charged at a constant current and constant voltage, and discharged at a constant current for 500cls. The capacity after 500cls is recorded as C2. C2 / C0 is recorded as the 500cls capacity retention rate.

[0197] 5) Battery cell specific capacity test: At 25℃, charge the battery cell at a constant current of 0.33C to the charging cutoff voltage of 4.4V, then charge at a constant voltage to a current of 0.05C, let it stand for 5 minutes, and then discharge it at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. Record its actual capacity as C0. C0 / battery cell mass is the specific capacity.

[0198] As can be seen from the test results of Examples 1 to 10 and Comparative Examples 1 to 2, using ether-based or sulfone-based solvents to perform film formation treatment on the initial negative electrode sheet to obtain a negative electrode composite sheet containing a solid electrolyte membrane, the lithium metal battery of the examples has a thinner solid electrolyte membrane and lower resistance after the first formation. The reason for this is that the solid electrolyte membrane formed by ether-based or sulfone-based solvents has a larger mass ratio of organic to inorganic matter, which improves the stability of the solid electrolyte membrane formed by ether-based or sulfone-based solvents. The solid electrolyte membrane formed by ether-based or sulfone-based solvents also has better elasticity and good affinity for active ions, so that the battery cell containing the negative electrode sheet, solid electrolyte membrane and first electrolyte has improved kinetic performance, cycle life and specific capacity.

[0199] The test results from Examples 1 to 8 and Comparative Example 1 show that using ether-based or sulfone-based solvents to form a solid electrolyte membrane on the initial negative electrode exhibits better kinetic performance, cycle life, and specific capacity compared to solid electrolyte membranes formed with carbonate-based solvents. This is because the thickness and composition of the solid electrolyte membrane formed with ether-based or sulfone-based solvents change, thus affecting the kinetic and cycle performance of the battery cell.

[0200] The test results of Example 9 and Comparative Example 2 show that when 1,3-dioxolane is used to form a film on the initial negative electrode sheet, a solid electrolyte membrane formed by 1,3-dioxolane is obtained. Compared with the solid electrolyte membrane formed by carbonate solvent in Comparative Example 2, the battery cell obtains better kinetic performance, cycle life and specific capacity. The reason is that the solid electrolyte membrane of Example 9 has better stability and elasticity.

[0201] Compared to Comparative Example 3, Example 1 used 1,3-dioxolane to form a film on the initial negative electrode, resulting in a solid electrolyte membrane formed with 1,3-dioxolane. However, Example 1 used a carbonate solvent, while Comparative Example 3 used a 1,3-dioxolane solvent. After 500 cycles, the impedance of the solid electrolyte membrane in Comparative Example 3 was greater than that in Example 1, and the 3C capacity retention of Example 1 was also significantly better than that of Comparative Example 3. This demonstrates that using carbonate solvents, compared to ether solvents like 1,3-dioxolane, can improve the kinetic performance of the battery cell. The 500cls capacity retention and specific capacity of Example 1 were also superior to those of Comparative Example 3, indicating that ether solvents have a certain degree of oxidation intolerance in battery cells, leading to some side reactions that affect the cycle life and specific capacity of the battery cell.

[0202] Compared to Comparative Example 4, Example 2 used dimethyl sulfoxide (DMSO) to form a film on the initial negative electrode, resulting in a solid electrolyte membrane formed with DMSO. However, Example 2 used carbonate solvents for its battery cells, while Comparative Example 4 used DMSO. After 500 cycles, the impedance of the solid electrolyte membrane in Comparative Example 4 was greater than that in Example 2, and the 3C capacity retention of Example 2 was also significantly better than that of Comparative Example 4. This indicates that using carbonate solvents, compared to sulfone solvents like DMSO, can improve the kinetic performance of the battery cells. The 500cls capacity retention and specific capacity of Example 2 were also superior to those of Comparative Example 4, suggesting that sulfone solvents caused some side reactions in the battery cells, affecting the cycle life and specific capacity.

[0203] The above example, using a lithium battery cell, verifies that battery cells with a composite negative electrode containing a solid electrolyte membrane obtained by using ether-based or sulfone-based solvents to form a film on the initial negative electrode have good kinetic and cycle performance. Other battery cells using the electrolyte provided in this application, such as lithium metal battery cells, can also achieve the same effect.

[0204] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, wherein, include: The first electrolyte includes a carbonate solvent; A negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, wherein the solid electrolyte membrane is located on the surface of the negative electrode. The negative electrode composite electrode is formed by performing a film-forming treatment on the negative electrode in a second electrolyte to composite the solid electrolyte membrane on the surface of the negative electrode. The second electrolyte includes one or more of ether solvents and sulfone solvents.

2. The battery cell according to claim 1, wherein, The ether solvents include one or more of 1,2-dimethoxypropane, 1,2-dimethoxyethylene, tetrahydrofuran, 1,3-dioxocyclopentane, dipentyl ether, dimethyl ethyl ether, di(2-methoxyethyl) ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

3. The battery cell according to claim 1 or 2, wherein, The sulfone solvents include one or more of dimethyl sulfoxide, sulfolane, ethyl methyl sulfone, diphenyl sulfone, methanesulfonylmethane, and dimethyl sulfone.

4. The battery cell according to any one of claims 1 to 3, wherein, The conductivity of the first electrolyte is 5 to 12 mS / cm.

5. The battery cell according to claim 4, wherein, The conductivity of the first electrolyte is 7 ms / cm to 10 ms / cm.

6. The battery cell according to any one of claims 1 to 5, wherein, The negative electrode composite electrode includes a negative electrode active material film layer, and the negative electrode active material film layer satisfies one or more of the following conditions: 1) The areal density of the negative electrode active material film layer is 150 to 300 g / 1540.25 mm. 2 ; 2) The compaction density of the negative electrode active material film is 1.3 g / cm³. 3 Up to 1.7 g / cm 3 .

7. The battery cell according to claim 6, wherein, The negative electrode active material film layer satisfies one or more of the following conditions: 1) The areal density of the negative electrode active material film is 250 g / mm². 2 Up to 280g / mm 2 ; 2) The compaction density of the negative electrode active material film is 1.6 g / cm³. 3 Up to 1.65 g / cm 3 .

8. The battery cell according to any one of claims 1 to 7, wherein, The solid electrolyte membrane satisfies one or more of the following conditions: 1) The thickness of the solid electrolyte membrane is from 2 nm to 90 nm; 2) The membrane impedance of the solid electrolyte membrane is 0.01 to 15 Ω.

9. The battery cell according to any one of claims 1 to 8, wherein, The carbonate solvents include one or more of dimethyl carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, and methyl acetate.

10. The battery cell according to any one of claims 1 to 9, wherein, The operating voltage of the battery cell is 2.5 to 4.4V.

11. The battery cell according to any one of claims 1 to 10, wherein, The battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive active material film layer, the positive active material film layer includes a positive active material, and the positive active material includes a lithium-containing transition metal oxide material.

12. A method for preparing a single battery cell, wherein, include: A negative electrode is processed in an environment including a second electrolyte to obtain a negative electrode composite electrode, wherein the negative electrode composite electrode includes a negative electrode and a solid electrolyte membrane, and the second electrolyte includes one or more of ether solvents and sulfone solvents. The first electrolyte and the negative electrode composite sheet are assembled to obtain a battery cell, wherein the first electrolyte includes a carbonate solvent.

13. The preparation method according to claim 12, wherein, The thickness of the solid electrolyte membrane is ≤2nm.

14. A battery device, wherein, Includes the battery cell described in any one of claims 1 to 11 or the battery cell prepared by the preparation method described in claim 12 or 13.

15. An electrical appliance, wherein, Includes the battery device as described in claim 14.

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