Battery cell, preparation method therefor, and electrical apparatus

Abstract

The present application discloses a battery cell, a preparation method therefor, and an electrical apparatus. The battery cell comprises a positive electrode plate, a negative electrode plate, and a separator, the separator being located between the positive electrode plate and the negative electrode plate. The negative electrode plate comprises a main body portion, and a negative electrode tab extending from one end or both ends of the main body portion in a first direction X. The main body portion comprises a negative electrode current collector, and a metal layer located on one or two surfaces of the negative electrode current collector in a third direction Z. The negative electrode tab comprises a metal substrate and an insulating layer located on the metal substrate, the metal substrate having a first surface and a second surface opposite to each other in the third direction Z and a side surface connecting the first surface and the second surface, the insulating layer being located on the first surface and / or the second surface of the metal substrate. In the first direction X, a gap between the insulating layer and the metal layer is 0-1 mm, and the size D2 of the insulating layer is 50% to 100% of a maximum size D1 of the negative electrode tab. The battery cell has a long cycle life.

Description

Battery cells and their preparation methods, and electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410797392.2, filed on June 19, 2024, entitled “Battery Cell and Method for Preparation Thereof, Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] The cycle life and reliability of a battery cell are crucial to its performance. Currently, metal battery cells suffer from poor cycle life and low reliability, mainly because metal deposition inevitably occurs at the negative electrode during the cycle process. Summary of the Invention

[0005] This application provides a battery cell, its preparation method, and an electrical device thereof, wherein the battery cell has a long cycle life.

[0006] In a first aspect, this application provides a battery cell including a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, the negative electrode including a main body and a negative electrode tab extending from one or both ends of the main body along a first direction X; the main body including a negative current collector and a metal layer on one or two surfaces of the negative current collector along a third direction Z; the negative electrode tab including a metal substrate and an insulating layer on the metal substrate, the metal substrate having a first surface and a second surface opposite each other along the third direction Z and a side surface connecting the first surface and the second surface, the insulating layer being located on the first surface and / or the second surface of the metal substrate; the gap between the insulating layer and the metal layer along the first direction X is 0-1 mm; along the first direction X, the size D2 of the insulating layer is 50% to 100% of the maximum size D1 of the negative electrode tab.

[0007] The metal substrate of the negative electrode tab has an insulating layer covering more than 50% of the first surface and / or second surface along the first direction X. This allows the surface of the negative electrode tab to have low electronic conductivity, thereby reducing the reduction of ions in the electrolyte to metal at the negative electrode tab location, lowering the risk of short circuit in the battery cell, and improving the cycle life of the battery cell.

[0008] In some embodiments, along the first direction X, the size D2 of the insulating layer is 80% to 100% of the maximum size D1 of the negative electrode tab. This can further reduce the risk of short circuit in the battery cell and improve the cycle life of the battery cell.

[0009] In some embodiments, the maximum size D1 of the negative electrode tab along the first direction X is 40mm-50mm.

[0010] In some embodiments, the size of the insulating layer along the third direction Z is 1μm-50μm, optionally 5μm-30μm. This allows for insulation of the negative electrode tab position without affecting subsequent welding of the negative electrode tab.

[0011] In some embodiments, the insulating layer is also located on a portion or all of the side of the metal substrate. This can further reduce the risk of short circuits in individual battery cells and improve the cycle life of the battery cells.

[0012] In some embodiments, the shape of the negative electrode tab includes one or more of the following: rectangle, square, trapezoid, semicircle, and triangle.

[0013] In some embodiments, the shape of the negative electrode tab includes one or more of a rectangle, a square, and a trapezoid, and one end of the negative electrode tab is connected to the edge of the main body by an arc, while the other end is chamfered.

[0014] In some embodiments, the insulating layer comprises one or more of insulating inorganic particles and insulating polymers.

[0015] In some embodiments, the insulating layer comprises an insulating polymer, wherein the insulating polymer content in the insulating layer is 70%-100% by mass, based on the mass of the insulating layer.

[0016] In some embodiments, the insulating polymer may be meltable or softenable at a processing temperature of 200°C.

[0017] In some embodiments, the insulating polymer in 10s -1 The apparent shear rate and viscosity at 200℃ are less than or equal to 600 Pa·s.

[0018] In some embodiments, the degree of swelling of the insulating polymer after being immersed in ethylene glycol dimethyl ether at a constant temperature of 60°C for 7 days is less than or equal to 32%.

[0019] In some embodiments, the insulating polymer includes one or more of polyvinylidene fluoride and its copolymers, polyamide, polyurethane, polyacrylate and its copolymers, styrene-butadiene rubber, polyethylene, polypropylene, polyacrylonitrile and its copolymers, acrylamide copolymers, and their respective derivatives.

[0020] In some embodiments, the weight-average molecular weight of the insulating polymer is 100,000 to 500,000.

[0021] In some embodiments, the negative current collector is integrally formed with the metal substrate.

[0022] In some embodiments, the metal layer comprises one or more of lithium, lithium alloy, sodium, and sodium alloy.

[0023] Secondly, this application provides a method for preparing a battery cell, comprising the following steps for preparing a negative electrode sheet: providing a negative electrode sheet and an insulating slurry, the negative electrode sheet comprising a main body portion and a negative electrode tab forming region extending from one or both ends of the main body portion along a first direction X, the main body portion comprising a negative electrode current collector and a metal layer located on one or two surfaces of the negative electrode current collector along a third direction Z, the negative electrode tab forming region being made of metal; applying the insulating slurry onto the negative electrode tab forming region, drying it to form an insulating layer, the gap between the insulating layer and the metal layer along the first direction X being 0-1 mm; cutting the negative electrode tab forming region to form a negative electrode tab and making the dimension D2 of the insulating layer in the first direction X 50% to 100% of the maximum dimension D1 of the negative electrode tab, thereby obtaining a negative electrode sheet.

[0024] In some embodiments, the negative electrode tab is formed by cutting the negative electrode tab forming area using laser die cutting.

[0025] In some embodiments, the laser cutting parameters are adjusted and the insulating layer is allowed to flow to the side of the negative electrode tab.

[0026] Thirdly, this application provides an electrical device that includes a battery cell according to the first aspect of this application, the battery cell being used to provide electrical energy. Attached Figure Description

[0027] 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.

[0028] Figure 1 is a schematic diagram of the structure of the negative electrode sheet provided in some embodiments of this application.

[0029] Figure 2 is a schematic diagram of the structure of a metal substrate provided in some embodiments of this application.

[0030] Figure 3 is a schematic diagram of the negative electrode tab provided in some embodiments of this application.

[0031] Figures 4 and 5 are schematic diagrams of the negative electrode sheet provided in other embodiments of this application.

[0032] Figure 6 shows a schematic diagram of the negative electrode preparation process provided in some embodiments of this application.

[0033] Figure 7 shows the negative electrode tab obtained after disassembling the lithium metal battery cell prepared in Example 1 after 100 cycles.

[0034] Figure 8 shows the negative electrode tab obtained after disassembling the lithium metal battery cell prepared in Example 9 after 82 cycles.

[0035] Figure 9 shows the negative electrode tab obtained after disassembling the lithium metal battery cell prepared in Comparative Example 1 after 60 cycles.

[0036] The accompanying drawings are not necessarily drawn to scale.

[0037] The reference numerals in the attached drawings are explained as follows: 10, negative electrode sheet; 11, main body; 110, negative current collector; 111, metal layer; 12, negative electrode tab; 120, metal substrate; 1201, first surface; 1202, second surface; 121, insulating layer; X, first direction; Y, second direction; Z, third direction. Detailed Implementation

[0038] The following detailed description, with appropriate reference to the accompanying drawings, discloses the battery cell, its preparation method, and embodiments of the electrical device of this application. However, unnecessary details 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 method may also include step (c), indicating 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.

[0043] In this application, the terms "multiple" or "various" refer to two or more kinds of things.

[0044] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0045] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0046] 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.

[0047] Unless otherwise stated, the testing instruments mentioned in this application shall be used in accordance with the requirements of the product specification sheet.

[0048] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0049] A battery cell is the smallest unit that makes up a battery, 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.

[0050] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0051] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0052] The battery cells provided in the embodiments of this application can be metal battery cells, such as lithium metal battery cells, sodium metal battery cells, etc.

[0053] A single battery cell includes electrode components, electrolyte, and outer packaging. The outer packaging is used to encapsulate the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be aluminum-plastic film or plastic, such as one or more of polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0054] The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0055] Short circuits are common in metal battery cells during cycling. Taking lithium metal battery cells as an example, during cycling, the reversible active lithium gradually decreases while lithium-containing byproducts accumulate. As the cell expands and contracts during charging and discharging, powdery lithium-containing byproducts drift with the electrolyte throughout the cell, inevitably leading to lithium metal deposition in the negative electrode region and increasing large-area polarization. In particular, lithium metal deposition on the conductive negative electrode tab can easily cause the negative and positive electrodes to connect, resulting in short circuits and, in severe cases, thermal runaway of the battery cell.

[0056] In view of this, this application starts from the negative electrode structure and reduces the risk of short circuit in the battery cell by setting an insulating layer on the negative electrode tab, thereby improving the cycle life of the battery cell.

[0057] As shown in Figures 1 to 3, the negative electrode 10 of the battery cell provided in this application embodiment includes a main body 11 and a negative electrode tab 12 extending from one or both ends of the main body 11 along a first direction X. The main body 11 includes a negative current collector 110 and a metal layer 111 located on one or both surfaces of the negative current collector 110 along a third direction Z. The negative electrode tab 12 includes a metal substrate 120 and an insulating layer 121 located on the metal substrate 120. The metal substrate 120 has a first surface 1201 and a second surface 1202 opposite to each other along the third direction Z, and a side surface connecting the first surface 1201 and the second surface 1202. The insulating layer 121 is located on the first surface 1201 and / or the second surface 1202 of the metal substrate 120. Along the first direction X, the gap between the insulating layer 121 and the metal layer 111 is 0-1 mm. Along the first direction X, the size D2 of the insulating layer 121 is 50% to 100% of the maximum size D1 of the negative electrode tab 12.

[0058] The metal layer 111 is located on one or two surfaces of the negative electrode current collector 110 along the third direction Z. For example, if the metal layer 111 is located on one of the surfaces of the negative electrode current collector 110 along the third direction Z, then the insulating layer 121 is located on the first surface 1201 or the second surface 1202, and the gap between the insulating layer 121 and the metal layer 111 along the first direction X is 0-1mm; or, if the metal layer 111 is located on two surfaces of the negative electrode current collector 110 along the third direction Z, then the insulating layer 121 is located on both the first surface 1201 and the second surface 1202, and the gap between the insulating layer 121 and the metal layer 111 along the first direction X is 0-1mm.

[0059] The metal substrate of the negative electrode tab has an insulating layer covering more than 50% of the first surface and / or second surface along the first direction X. This allows the surface of the negative electrode tab to have low electronic conductivity, thereby reducing the reduction of ions in the electrolyte to metal at the negative electrode tab location, lowering the risk of short circuit in the battery cell, and improving the cycle life of the battery cell.

[0060] The first direction X, the second direction Y, and the third direction Z intersect each other, with the third direction Z being the thickness direction of the negative electrode sheet 10.

[0061] The negative electrode 10 has no insulating layer at the edge of the metal layer 111 in the non-tab region, that is, along the first direction X, the metal layer 111 in the non-tab region has no insulating layer.

[0062] The number of negative electrode tabs 12 can be one or more. When there are multiple negative electrode tabs 12, the multiple negative electrode tabs 12 are distributed at intervals along the second direction Y.

[0063] Along the first direction X, the gap between the insulating layer 121 and the metal layer 111 is 0-1mm. Optionally, along the first direction X, the gap between the insulating layer 121 and the metal layer 111 can be 0mm, that is, the insulating layer 121 and the metal layer 111 are in contact without any gap.

[0064] Along the first direction X, the size D2 of the insulating layer 121 is 50% to 100% of the maximum size D1 of the negative electrode tab 12, for example, it can be 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 100%, or any range of the above values.

[0065] Optionally, along the first direction X, the size D2 of the insulating layer 121 can be 80% to 100%, 85% to 100%, 90% to 100%, 95% to 100%, 80% to 98%, 85% to 98%, 90% to 98%, or 95% to 98% of the maximum size D1 of the negative electrode tab 12.

[0066] This can further reduce the risk of short circuits in individual battery cells and improve the cycle life of individual battery cells.

[0067] The dimension D2 of the insulating layer 121 refers to the maximum value of the dimension of the insulating layer in the first direction X.

[0068] The maximum dimension D1 of the negative electrode tab 12 refers to the maximum value of the dimension of the negative electrode tab in the first direction X.

[0069] In some embodiments, the shape of the negative electrode tab 12 may include, but is not limited to, one or more of the following: rectangle, square, trapezoid, semicircle, and triangle. As shown in Figures 4 and 5, rectangular, trapezoidal, triangular, and semicircular negative electrode tabs 12 are shown respectively.

[0070] Optionally, in some embodiments, the shape of the negative electrode tab 12 may include one or more of the following: rectangle, square, trapezoid.

[0071] Alternatively, the shape of the negative electrode tab 12 may include one or more of a rectangle, a square, and a trapezoid, and one end of the negative electrode tab 12 in the first direction X transitions to the edge of the main body 11 by an arc, while the other end is chamfered. Optionally, the chamfer can be a rounded corner or an obtuse angle.

[0072] In some embodiments, along the first direction X, the maximum size D1 of the negative electrode tab 12 can be 40mm-50mm, for example, it can be 40mm, 41mm, 42mm, 43mm, 44mm, 45mm, 46mm, 47mm, 48mm, 49mm, 50mm, or any range of the above values.

[0073] In some embodiments, the size, i.e. the thickness, of the insulating layer 121 along the third direction Z can be 1μm-50μm, for example, it can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 15μm, 17.5μm, 20μm, 22.5μm, 25μm, 27.5μm, 30μm, 32.5μm, 35μm, 37.5μm, 40μm, 42.5μm, 45μm, 47.5μm, 50μm, or any range of the above values.

[0074] If the thickness of the insulation layer is within the above range, it can insulate the negative electrode tab position without affecting the subsequent welding of the negative electrode tab.

[0075] Optionally, along the third direction Z, the dimensions of the insulating layer 121 can be 2μm-50μm, 2μm-45μm, 2μm-40μm, 2μm-35μm, 2μm-30μm, 2μm-25μm, 5μm-50μm, 5μm-45μm, 5μm-40μm, 5μm-35μm, 5μm-30μm, 5μm-25μm, 8μm-50μm, 8μm-45μm, 8μm-40μm. 8μm-35μm, 8μm-30μm, 8μm-25μm, 10μm-50μm, 10μm-45μm, 10μm-40μm, 10μm-35μm, 10μm-30μm, 10 μm-25μm, 12.5μm-50μm, 12.5μm-45μm, 12.5μm-40μm, 12.5μm-35μm, 12.5μm-30μm, 12.5μm-25μm.

[0076] Within the above-mentioned range, the thickness of the insulating layer can further reduce the risk of lithium metal deposition on the negative electrode tab and also enable the battery cell to have a better cycle life.

[0077] In some embodiments, the insulating layer 121 may also be located on part or all of the side surface of the metal substrate 120. Taking the negative electrode tab 12 as an example where the shape is rectangular, square, or trapezoidal, the insulating layer 121 may also be located on part or all of one or more of the two side surfaces of the metal substrate 120 along the second direction Y and the free side surfaces of the metal substrate 120 along the first direction X.

[0078] The insulating layer located on the side of the metal substrate, either partially or entirely, can insulate the negative electrode tab cutting position, thereby further reducing the risk of short circuit in the battery cell and improving the cycle life of the battery cell.

[0079] Optionally, the insulating layer 121 may also be located on all sides of the metal substrate 120. That is, the insulating layer 121 covers all positions on all sides of the metal substrate 120.

[0080] In some embodiments, the insulating layer 121 may include one or more of insulating inorganic particles and insulating polymers.

[0081] Optionally, the insulating inorganic particles may include, but are not limited to, one or more of the following: alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, spinel, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, zirconium carbide, mica powder, fluorophlogopite powder, talc powder, hydrotalcite, hydrotalcite-like material, mullite, montmorillonite, mullite, orthoclase, calcium carbonate, magnesium carbonate, calcite, magnesite, dolomite, siderite, rhodochrosite, zirconia, cerussite, strontium carbonate, and barium carbonate.

[0082] Optionally, in some embodiments, at least some or all of the insulating inorganic particles may be plate-shaped particles. Compared with insulating inorganic particles of other morphologies, plate-shaped insulating inorganic particles can provide better insulation at the negative electrode tab, thereby further reducing the risk of short circuit in the battery cell and improving the cycle life of the battery cell.

[0083] Optionally, in some embodiments, the volume distribution particle size Dv50 of the insulating inorganic particles can be 0.05μm-5μm, for example, it can be 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or any range of the above values.

[0084] The volume distribution of insulating inorganic particles with a particle size Dv50 within the above range can improve the insulation of the negative electrode tab, reduce the electronic conductivity of the negative electrode tab, and increase the uniformity of the insulation layer, making it less prone to "powder shedding".

[0085] Alternatively, the volume distribution particle size Dv50 of the insulating inorganic particles can be 0.1μm-3μm, 0.1μm-2μm, 0.1μm-1μm, 0.1μm-0.8μm, or 0.1μm-0.5μm.

[0086] Optionally, in some embodiments, the insulating polymer is molten or softenable at a processing temperature of 200°C. The statement that the insulating polymer is molten or softenable at a processing temperature of 200°C means that when the insulating polymer is heated to 200°C, it exhibits the property of melting or softening.

[0087] Optionally, in some embodiments, the insulating polymer is in 10s -1The apparent shear rate and viscosity at 200°C can be less than or equal to 600 Pa·s. The viscosity of the insulating polymer has a well-known meaning in the art and can be tested using thermal analysis instruments, such as a flow meter, at a test temperature of 200°C and an apparent shear rate of 10 s⁻¹. -1 .

[0088] The insulating polymer has thermal melting properties, so when the negative electrode tab is laser-cut, the insulating polymer can flow to the cutting position (i.e., the side) of the negative electrode tab after being heated. This can reduce the problem of metal deposition at the cutting position of the negative electrode tab, and further reduce the risk of short circuit in the battery cell and improve the cycle life of the battery cell.

[0089] By adjusting parameters such as the molecular weight, crystallinity, and particle size of the insulating polymer, its melting / softening properties and viscosity characteristics can be modified.

[0090] Optionally, in some embodiments, the volume distribution particle size Dv50 of the insulating polymer can be 0.05μm-5μm, for example, it can be 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or any range of the above values.

[0091] When the volume distribution particle size Dv50 of the insulating polymer is within the above range, it can better insulate the negative electrode tab, reduce the electronic conductivity of the negative electrode tab, and increase the uniformity of the insulating layer, making it less prone to "powdering" phenomenon.

[0092] Alternatively, the volumetric particle size Dv50 of the insulating polymer can be 0.1μm-3μm, 0.1μm-2μm, 0.1μm-1μm, 0.1μm-0.8μm, or 0.1μm-0.5μm.

[0093] The volumetric distribution particle size Dv50 of a material is a well-known concept in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 50%. It can be determined using instruments and methods known in the art. For example, it can be tested using a laser particle size analyzer (e.g., Master Sizer 2000) according to GB / T19077-2016. During testing, take an appropriate amount of the sample to be tested (ensuring 8%-12% light-blocking), add 20 ml of deionized water, and simultaneously microwave for 5 minutes (e.g., 53 kHz / 120 W) to ensure complete dispersion of the sample.

[0094] Optionally, in some embodiments, the swelling degree of the insulating polymer after being immersed in ethylene glycol dimethyl ether at a constant temperature of 60°C for 7 days can be less than or equal to 32%.

[0095] Insulating polymers have low swelling in electrolytes and can remain stable during long-term cycling of battery cells, thus enabling battery cells to have a longer cycle life.

[0096] Optionally, the swelling degree of the insulating polymer after being immersed in ethylene glycol dimethyl ether at a constant temperature of 60°C for 7 days can be less than or equal to 28%, less than or equal to 25%, less than or equal to 23%, less than or equal to 21%, less than or equal to 18%, less than or equal to 15%, less than or equal to 12%, or less than or equal to 10%.

[0097] The swelling degree of insulating polymers can be tested as follows: Take an appropriate sample with a mass of m1 and completely immerse it in dimethyl ethylene glycol (DME), and soak it at a constant temperature of 60℃ for 7 days (i.e., 7*24h). Remove the sample, wipe off the residual solvent on the surface with filter paper, and then immediately weigh the mass m2 of the swollen sample. The swelling degree of the insulating polymer = (m2-m1 / m1)×100%.

[0098] The swelling degree of the insulating polymer can be adjusted by regulating parameters such as molecular weight, crystallinity, and particle size.

[0099] Optionally, in some embodiments, the insulating polymer may include one or more of polyvinylidene fluoride and its copolymers, polyamide, polyurethane, polyacrylate and its copolymers, styrene-butadiene rubber, polyethylene, polypropylene, polyacrylonitrile and its copolymers, acrylamide copolymers, and their respective derivatives.

[0100] Polyvinylidene fluoride copolymers refer to polymers obtained by copolymerizing vinylidene fluoride (VDF) monomers with other monomers. Optionally, the other monomers may include one or more of hexafluoropropylene, pentafluoropropylene, tetrafluoroethylene, trifluorochloroethylene, and ethylene. Optionally, polyvinylidene fluoride copolymers may include one or more of vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-pentafluoropropylene copolymers, vinylidene fluoride-tetrafluoroethylene copolymers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers, and vinylidene fluoride-trifluorochloroethylene copolymers.

[0101] Polyacrylate copolymers refer to polymers obtained by copolymerizing acrylate monomers with other monomers, or polymers obtained by copolymerizing two or more acrylate monomers.

[0102] Alternatively, the polyacrylate may include polymethyl methacrylate (PMMA).

[0103] Optionally, a polyacrylonitrile copolymer refers to a polymer obtained by copolymerizing acrylonitrile monomer with other monomers. Optionally, a polyacrylonitrile copolymer may include acrylonitrile-acrylate copolymer and acrylonitrile-acrylate-acrylamide copolymer.

[0104] Optionally, an acrylamide copolymer refers to a polymer obtained by copolymerizing acrylamide monomer with other monomers. Optionally, an acrylamide copolymer includes an acrylamide-acrylate copolymer.

[0105] Derivatives of insulating polymers refer to polymers obtained by replacing one or more hydrogen atoms in an insulating polymer with other atoms or groups of atoms.

[0106] Optionally, in some embodiments, the weight-average molecular weight of the insulating polymer can be 100,000 to 500,000, for example, it can be 100,000, 120,000, 140,000, 160,000, 180,000, 200,000, 220,000, 240,000, 260,000, 280,000, 300,000, 320,000, 340,000, 360,000, 380,000, 400,000, 420,000, 440,000, 460,000, 480,000, 500,000, or any combination of the above values.

[0107] The weight-average molecular weight of insulating polymers can be tested by gel permeation chromatography.

[0108] Optionally, in some embodiments, the electronic conductivity of the insulating polymer may be less than 10. -9 S / cm has good electronic insulation properties. Therefore, when used in insulating layers, its low electronic conductivity can reduce the problem of metal deposition on the large surface of the negative electrode tab and at the cutting position of the negative electrode tab.

[0109] In some embodiments, the insulating layer 121 may include an insulating polymer, or may include both insulating inorganic particles and an insulating polymer.

[0110] In some embodiments, the insulating layer 121 may include an insulating polymer, and the mass content of the insulating polymer in the insulating layer may be 70%-100%, based on the mass of the insulating layer, for example, it may be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any range of the above values.

[0111] The insulating polymer has a certain degree of elasticity, which can also improve the problem of negative electrode tab breakage caused by the cyclic expansion of battery cells.

[0112] Optionally, the mass content of the insulating polymer in the insulating layer can be 80%-100%, 85%-100%, 90%-100%, 92%-100%, 94%-100%, 96%-100%, 80%-99%, 85%-99%, 90%-99%, 92%-99%, 94%-99%, 80%-97%, 85%-97%, 90%-97%, 92%-97%, or 94%-97%. In some embodiments, the mass content of the insulating polymer in the insulating layer can be 100%, meaning the insulating layer contains no components other than the insulating polymer.

[0113] In some embodiments, the insulating layer may further include an adhesive, the mass content of which may be 0-30% based on the mass of the insulating layer, for example, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any combination of the above values.

[0114] Optionally, the mass content of the adhesive in the insulation layer can be 1%-20%, 1%-15%, 1%-10%, 1%-8%, 1%-6%, 3%-20%, 3%-15%, 3%-10%, 3%-8%, or 3%-6%. In some embodiments, the mass content of the adhesive in the insulation layer can be 0%, i.e., the insulation layer contains no adhesive.

[0115] Optionally, the adhesive in the insulation layer may be one or more of poly(meth)acrylate, poly(meth)acrylic acid, poly(meth)acrylate salt, and sodium carboxymethyl cellulose.

[0116] In some embodiments, the insulating layer 121 may include insulating inorganic particles, an insulating polymer, and optionally a binder. The mass content of the insulating inorganic particles in the insulating layer 121 may be 0.5%-28%, the mass content of the insulating polymer may be 70%-99%, and the mass content of the binder may be 0%-28%, based on the mass of the insulating layer. Optionally, the mass content of the insulating inorganic particles may be 0.5%-28%, the mass content of the insulating polymer may be 70%-99%, and the mass content of the binder may be 0.5%-28%. More preferably, the mass content of the insulating inorganic particles may be 0.5%-18%, the mass content of the insulating polymer may be 80%-99%, and the mass content of the binder may be 0.5%-18%.

[0117] The main body 11 includes a negative electrode current collector 110 and a metal layer 111 located on one or two surfaces of the negative electrode current collector 110 along the third direction Z. The composition of the metal layer 111 can be adjusted according to the type of battery cell.

[0118] In some embodiments, the material in the metal layer 111 may be one or more of lithium, lithium alloy, sodium, and sodium alloy.

[0119] Lithium alloys can be alloys formed from metallic lithium with other metallic or non-metallic elements. For example, other metallic elements in lithium alloys may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0120] Sodium alloys can be alloys formed from metallic sodium with other metallic or non-metallic elements. For example, other metallic elements in a sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0121] In some embodiments, the negative current collector 110 and the metal substrate 120 can be integrally formed.

[0122] In some embodiments, the negative electrode current collector 110 may be a metal foil or a composite current collector. Optionally, the negative electrode current collector 110 may be a metal foil.

[0123] Examples of metal foils include, but are not limited to, copper foil, nickel foil, titanium foil, nickel-plated copper foil, copper alloy foil, nickel alloy foil, and titanium alloy foil. 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 examples, the metal material may include, but is not limited to, one or more of copper, nickel, titanium, silver, copper alloys, nickel alloys, titanium alloys, and silver alloys. As examples, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0124] In some embodiments, the metal substrate 120 may be a metal foil or a composite current collector. Optionally, the metal substrate 120 may be a metal foil.

[0125] Examples of metal foils include, but are not limited to, copper foil, nickel foil, titanium foil, nickel-plated copper foil, copper alloy foil, nickel alloy foil, and titanium alloy foil. 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 examples, the metal material may include, but is not limited to, one or more of copper, nickel, titanium, silver, copper alloys, nickel alloys, titanium alloys, and silver alloys. As examples, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0126] [Positive electrode plate]

[0127] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0128] In some embodiments, the positive electrode active material may include a material capable of extracting and inserting lithium.

[0129] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, 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. The modified compounds of the above-mentioned positive electrode active materials may be for doping modification and / or surface coating modification of the positive electrode active materials.

[0130] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D fOne or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0131] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining a battery that balances high capacity and high reliability.

[0132] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2 O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0133] In some embodiments, the positive electrode active material may include a material capable of desorbing and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0134] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0135] 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.

[0136] In some embodiments, the positive electrode 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.

[0137] In some embodiments, the positive electrode 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 the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, 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).

[0138] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. 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, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0139] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0140] [Isolation membrane]

[0141] The separator is placed between the positive and negative electrodes, mainly to prevent internal short circuits.

[0142] This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected. In some embodiments, the material of the separator membrane may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane may be a single-layer film or a multi-layer composite film. When the separator membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0143] [Electrolytes]

[0144] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0145] In some embodiments, the electrolyte includes anion, which may include bis(fluorosulfonyl)imide anion (FSI). - ), bis(trifluoromethanesulfonyl)imide anion (TFSI) - ), dioxaborate anion (BOB) - ), difluorooxalate borate anion (DFOB) - ), difluorodioxanol phosphate anion (DFOP) - ), tetrafluorooxalate phosphate anion (TFOP) - ), difluorophosphate anion (PO2F2) - ), hexafluorophosphate anion (PF6) - ), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO3) - One or more of the following.

[0146] In some embodiments, the electrolyte includes cations, which may include one or both of lithium ions and sodium ions.

[0147] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or higher, optionally 0.7 mol / L or higher, and further optionally 4 mol / L or lower, optionally 2.5 mol / L or lower, or 1.7 mol / L or lower. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0148] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, and nitriles. Esters may include, but are not limited to, one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, and sulfonates. Carbonates may include cyclic carbonates and / or chain carbonates; optionally, carbonates may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0149] As an example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), and propionic acid. Methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropionate 2-Trifluoromethylhexafluoropropyl methyl ether, 2-Trifluoromethylhexafluoropropyl ethyl ether, 2-Trifluoromethylhexafluoropropyl propyl ether, 3-Trifluoromethyloctafluorobutyl methyl ether, 3-Trifluoromethyloctafluorobutyl ethyl ether, 3-Trifluoromethyloctafluorobutyl propyl ether, 4- One or more of the following: trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0150] In some embodiments, the electrolyte may also include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve overcharge performance, additives that improve high-temperature performance, additives that improve low-temperature power performance, etc.

[0151] This application also provides a method for preparing a battery cell, which can prepare the above-mentioned battery cell. The method for preparing the battery cell includes the following steps for preparing a negative electrode sheet.

[0152] As shown in Figure 6, the preparation method of the negative electrode sheet includes the following steps: providing a negative electrode sheet 10 and an insulating slurry. The negative electrode sheet 10 includes a main body 11 and a negative electrode tab forming area extending from one or both ends of the main body 11 along a first direction X. The main body 11 includes a negative electrode current collector 110 and a metal layer 111 located on one or two surfaces of the negative electrode current collector 110 along a third direction Z. The negative electrode tab forming area is made of metal. The insulating slurry is applied to the negative electrode tab forming area and dried to form an insulating layer. Along the first direction X, the gap between the insulating layer 121 and the metal layer 111 is 0-1 mm. The negative electrode tab forming area is cut to form a negative electrode tab 12 and the size D2 of the insulating layer 121 in the first direction X is 50% to 100% of the maximum size D1 of the negative electrode tab 12, thereby obtaining the negative electrode sheet 10.

[0153] In some embodiments, the negative electrode tab 12 can be formed by cutting the negative electrode tab forming area using laser die cutting.

[0154] The high temperature of laser die-cutting of the negative electrode tab allows the insulating polymer on the first and / or second surfaces to flow to the cut site, thereby reducing metal deposition at the cut site of the negative electrode tab. This further reduces the risk of short circuit in the battery cell and improves the cycle life of the battery cell.

[0155] In some embodiments, the laser cutting parameters are adjusted and the insulating layer 121 is allowed to flow to the side of the negative electrode tab 12.

[0156] In some embodiments, the volumetric particle size Dv50 of the insulating polymer can be 0.05 μm-5 μm, for example, it can be 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any combination of the above values. Having a volumetric particle size Dv50 of the insulating polymer within the above range can improve the insulation of the negative electrode tab, reduce the electronic conductivity of the negative electrode tab, and increase the uniformity of the insulating layer, making it less prone to "powder shedding". Alternatively, the volumetric particle size Dv50 of the insulating polymer can be 0.1μm-3μm, 0.1μm-2μm, 0.1μm-1μm, 0.1μm-0.8μm, or 0.1μm-0.5μm.

[0157] In some embodiments, the solvent for the insulating paste may include, but is not limited to, one or more of N-methylpyrrolidone, triethyl phosphate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and diethylene glycol.

[0158] The preparation method of the insulating paste is not limited, and coating methods known in the art can be used, such as including but not limited to microgravure coating.

[0159] Methods for preparing battery cells using negative electrode sheets are well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, a positive electrode sheet, a separator, and a negative electrode sheet can be assembled to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with the aforementioned electrolyte. After processes such as encapsulation and settling, a battery cell is obtained.

[0160] This application also provides an electrical device, which includes the battery provided in this application embodiment. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is 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.

[0161] Electrical devices can choose the type of battery according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0162] An example electrical device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0163] 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.

[0164] Example

[0165] 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.

[0166] Example 1

[0167] (1) Preparation of negative electrode sheet

[0168] Polyvinylidene fluoride (PVDF) particles are dissolved in N-methylpyrrolidone (NMP) to prepare a 40% (w / w) solution, which is an insulating slurry. The insulating slurry is then coated along the edge of the copper foil and dried for later use.

[0169] Lithium metal is rolled onto release film No. 1, with a lithium metal layer thickness of 10 μm. Two films No. 1 with lithium metal layers are placed on both sides of a copper foil and rolled onto the surface of the copper foil, with the lithium metal layer and the insulating layer in close proximity, i.e., the gap is 0. A rectangular negative electrode tab is formed by laser die-cutting to obtain the negative electrode sheet. The thickness of the insulating layer on the large surface of the negative electrode tab, i.e., the first surface and the second surface, is 15 μm, the width of the insulating layer (i.e., dimension D2 in the first direction) is 50 mm, the width of the negative electrode tab (i.e., dimension D1 in the first direction) is 50 mm, and the sides of the negative electrode tab are also covered with an insulating layer.

[0170] (2) Preparation of positive electrode sheet

[0171] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 98:1:1 and added to the solvent N-methylpyrrolidone (NMP). The mixture is stirred until the system is homogeneous, resulting in a positive electrode slurry with a solid content of approximately 70%. The positive electrode slurry is then uniformly coated onto both surfaces of the positive electrode current collector aluminum foil, dried, and transferred to an oven for further drying. Finally, the foil is cut to obtain the positive electrode sheet.

[0172] (3) Preparation of electrolyte

[0173] LiFSI was dissolved in dimethyl ethylene glycol (DME). After complete dissolution, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) was added and mixed thoroughly to obtain the electrolyte. The molar ratio of LiFSI, DME, and TTE was 1:1.2:3.

[0174] (4) Preparation of the separating membrane

[0175] Polyethylene porous membrane is used as the separation membrane.

[0176] (5) Preparation of battery cells

[0177] The cut positive electrode sheet and the cut negative electrode sheet are stacked together, and the positive electrode sheet and the negative electrode sheet are separated by a separator to obtain a stacked electrode assembly. The stacked electrode assembly is placed in an aluminum-plastic film bag, and the prepared electrolyte is injected. After encapsulation and standing, a lithium metal battery cell is obtained.

[0178] Examples 2 to 9

[0179] Except for the difference in the thickness of the insulating layer on the first and second surfaces of the negative electrode tab, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0180] Comparative Example 1

[0181] Except that no insulating layer is provided on the two surfaces of the negative electrode tab, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0182] Cyclic performance test

[0183] Take the prepared lithium metal battery cell, set the ambient temperature to 25℃, and charge it at a constant current of 0.2C until the cutoff voltage of 4.3V is reached. Then, continue charging at a constant voltage of 4.3V until the current decays to 0.1C. Next, discharge it at a constant current of 1C to 2.8V to obtain the first discharge capacity. Repeat the above charge-discharge cycle and record the discharge capacity after each cycle. When the discharge capacity decays to 80% of the first discharge capacity, the lithium metal battery cell is considered to have reached the end of its lifespan, and the number of cycles the lithium metal battery cell has undergone at this point is recorded.

[0184] Lithium metal deposition test

[0185] Take the prepared lithium metal battery cell, set the ambient temperature to 25℃, and charge it with a constant current of 0.2C until the cutoff voltage of 4.3V is reached. Then, continue charging with a constant voltage of 4.3V until the current decays to 0.1C. Then, discharge it with a constant current of 1C to 2.8V to obtain the first discharge capacity. Repeat the above charge-discharge cycle for 100 cycles (the cycle life of a lithium metal battery cell is less than 100 cycles, so the actual number of cycles experienced is used here. For example, Comparative Example 1 uses 60 cycles, and Example 9 uses 82 cycles). Then, charge the lithium metal battery cell with a constant current of 0.2C until the cutoff voltage of 4.3V is reached. Then, continue charging with a constant voltage of 4.3V until the current decays to 0.1C. Finally, disassemble the lithium metal battery cell and observe the lithium metal deposition at the negative electrode tab.

[0186] First, observe whether there is lithium metal deposition on the side of the negative electrode tab. Then, collect all the deposited lithium metal from the large surface and sides of the negative electrode tab. The total mass of lithium metal is recorded as m0 mg, and the area of ​​the negative electrode tab is recorded as S0 mm. 2 m0 / S0 is greater than 0 and less than 2 mg / mm 2 This is defined as a small amount of lithium metal deposition. m0 / S0 ≥ 2 mg / mm 2 And less than 5mg / mm 2 Defined as moderate lithium metal deposition. m0 / S0 ≥ 5 mg / mm 2 , defined as the large-scale deposition of lithium metal.

[0187] Table 1

[0188] Figure 7 shows the negative electrode obtained after disassembling the lithium metal battery cell prepared in Example 1 after 100 cycles. Figure 8 shows the negative electrode obtained after disassembling the lithium metal battery cell prepared in Example 9 after 82 cycles. Figure 9 shows the negative electrode obtained after disassembling the lithium metal battery cell prepared in Comparative Example 1 after 60 cycles.

[0189] As shown in Figures 7 to 9, when the insulation layer is thicker, there is no lithium metal deposition on the large surface of the negative electrode tab and the cutting position, and the battery cell can have a longer cycle life.

[0190] In Comparative Example 1, no insulating layer was set on the negative electrode sheet. As can be seen from Figure 9, a large amount of lithium metal deposition occurred on the large surface and the cut position of the negative electrode sheet. Short circuits were easy to occur at the negative electrode tab, and the capacity of the lithium metal battery cell would drop sharply at the beginning of the cycle.

[0191] Examples 2-1 to 2-3

[0192] Except for adjusting the coating method of the insulating slurry to make the dimension D2 of the insulating layer on the negative electrode tab different along the first direction X, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0193] Comparative Example 2

[0194] Except for adjusting the coating method of the insulating slurry to make the dimension D2 of the insulating layer on the negative electrode tab different along the first direction X, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0195] Table 2

[0196] The test results above show that along the first direction X, the larger the insulation layer size D2, the better the insulation effect and the longer the cycle life of the lithium metal battery cell.

[0197] Example 3-1

[0198] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with polyacrylonitrile (PAN), the preparation method of the lithium metal battery cell is the same as in Example 1.

[0199] Example 3-2

[0200] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with polyurethane, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0201] Example 3-3

[0202] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with polymethyl methacrylate (PMMA), the preparation method of the lithium metal battery cell is the same as in Example 1.

[0203] Examples 3-4

[0204] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with styrene-butadiene rubber, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0205] Examples 3-5

[0206] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with polyethylene, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0207] Examples 3-6

[0208] Except for replacing polyvinylidene fluoride (PVDF) in the insulating slurry with polypropylene, the preparation method of the lithium metal battery cell is the same as in Example 1.

[0209] Swelling test of insulating polymers

[0210] Take an appropriate amount of sample with a mass of m1 and completely immerse it in dimethyl ethylene glycol (DME). Soak the sample at a constant temperature of 60℃ for 7 days (7*24h). Remove the sample and gently wipe off any residual solvent with filter paper. Immediately weigh the swollen sample mass m2. The degree of swelling of the insulating polymer = (m2 - m1 / m1) × 100%.

[0211] Table 3

[0212] The test results above show that the smaller the swelling degree of the insulating polymer, the longer the cycle life of the lithium metal battery cell.

[0213] Example 4-1

[0214] Except for the addition of spherical alumina to the insulating slurry, the preparation method of the lithium metal battery cell is the same as in Example 1. In the insulating layer, the mass ratio of polyvinylidene fluoride to spherical alumina is 90:10.

[0215] Example 4-2

[0216] Except for the addition of lamellar boehmite to the insulating slurry, the preparation method of the lithium metal battery cell is the same as in Example 1. In the insulating layer, the mass ratio of polyvinylidene fluoride to lamellar boehmite is 90:10.

[0217] Table 4

[0218] The test results above show that lithium metal battery cells with a small amount of insulating inorganic particles or no insulating inorganic particles in the insulating layer can have a longer cycle life.

[0219] 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, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, wherein, The negative electrode plate includes a main body and a negative electrode tab extending from one or both ends of the main body along a first direction X; The main body includes a negative electrode current collector and a metal layer located on one or both surfaces of the negative electrode current collector along the third direction Z. The negative electrode tab includes a metal substrate and an insulating layer located on the metal substrate. The metal substrate has a first surface and a second surface opposite each other in a third direction Z and a side surface connecting the first surface and the second surface. The insulating layer is located on the first surface and / or the second surface of the metal substrate. Along the first direction X, the gap between the insulating layer and the metal layer is 0-1 mm; Along the first direction X, the dimension D2 of the insulating layer is 50% to 100% of the maximum dimension D1 of the negative electrode tab.

2. The battery cell according to claim 1, wherein, Along the first direction X, the dimension D2 of the insulating layer is 80% to 100% of the maximum dimension D1 of the negative electrode tab.

3. The battery cell according to any one of claims 1-2, wherein, Along the first direction X, the maximum size D1 of the negative electrode tab is 40mm-50mm.

4. The battery cell according to any one of claims 1-3, wherein, Along the third direction Z, the size of the insulating layer is 1μm-50μm.

5. The battery cell according to claim 4, wherein, Along the third direction Z, the size of the insulating layer is 5μm-30μm.

6. The battery cell according to any one of claims 1-5, wherein, The insulating layer is also located on part or all of the side of the metal substrate.

7. The battery cell according to any one of claims 1-6, wherein, The shape of the negative electrode tab includes one or more of the following: rectangle, square, trapezoid, semicircle, and triangle.

8. The battery cell according to claim 7, wherein, The negative electrode tab has a shape including one or more of rectangle, square, and trapezoid, and one end of the negative electrode tab is connected to the edge of the main body by an arc, while the other end is chamfered.

9. The battery cell according to any one of claims 1-8, wherein, The insulating layer includes one or more of insulating inorganic particles and insulating polymers.

10. The battery cell according to any one of claims 1-9, wherein, The insulating layer comprises an insulating polymer, and the insulating polymer content in the insulating layer is 70%-100% by mass, based on the mass of the insulating layer.

11. The battery cell according to any one of claims 9-10, wherein, The insulating polymer satisfies at least one of the following conditions (1) to (3): (1) The insulating polymer can be melted or softened at a processing temperature of 200°C; (2) the insulating polymer has a viscosity of less than or equal to 600 Pa-s at 10 s -1 apparent shear rate and 200°C. (3) The degree of swelling of the insulating polymer after being immersed in ethylene glycol dimethyl ether at a constant temperature of 60°C for 7 days is less than or equal to 32%.

12. The battery cell according to any one of claims 9-11, wherein, The insulating polymer includes one or more of polyvinylidene fluoride and its copolymers, polyamide, polyurethane, polyacrylate and its copolymers, styrene-butadiene rubber, polyethylene, polypropylene, polyacrylonitrile and its copolymers, acrylamide copolymers, and their respective derivatives; and / or, The weight-average molecular weight of the insulating polymer is 100,000 to 500,000.

13. The battery cell according to any one of claims 1-12, wherein, The negative electrode current collector is integrally formed with the metal substrate.

14. The battery cell according to any one of claims 1-13, wherein, The metal layer includes one or more of lithium, lithium alloy, sodium, and sodium alloy.

15. A method for preparing a single battery cell, comprising the following steps for preparing a negative electrode sheet: A negative electrode sheet and an insulating paste are provided. The negative electrode sheet includes a main body and a negative electrode tab forming area extending from one or both ends of the main body along a first direction X. The main body includes a negative electrode current collector and a metal layer located on one or two surfaces of the negative electrode current collector along a third direction Z. The negative electrode tab forming area is made of metal. The insulating slurry is applied to the negative electrode tab forming area and dried to form an insulating layer. Along the first direction X, the gap between the insulating layer and the metal layer is 0-1 mm. The negative electrode tab is formed by cutting the negative electrode tab forming area and making the size D2 of the insulating layer in the first direction X 50% to 100% of the maximum size D1 of the negative electrode tab to obtain the negative electrode sheet.

16. The preparation method according to claim 15, wherein, The negative electrode tab is formed by cutting the negative electrode tab forming area using laser die cutting.

17. The preparation method according to claim 16, wherein, Adjust the laser cutting parameters and allow the insulating layer to flow to the side of the negative electrode tab.

18. An electrical device comprising a battery cell according to any one of claims 1-14, the battery cell being used to provide electrical energy.

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