Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a pole piece, the pole piece comprises a current collector and a film layer arranged on at least one side of the current collector, and an absolute value of a difference between a room temperature fracture elongation of the current collector and a room temperature fracture elongation of the pole piece is less than or equal to 3%. The current collector comprises at least one first metal foil layer, an average grain size of the first metal foil layer is 5 nm-50 nm, and a proportion of grains with a grain size less than 80 nm in the first metal foil layer is greater than or equal to 90%.

Description

Technical Field

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

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] Current collectors are an important component of batteries. With increasing market demands for battery energy density and cycle life, there is an urgent need to develop a new generation of current collectors to meet the needs of individual battery cells. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell that has both high energy density and good cycle life.

[0005] A first aspect of this application provides a battery cell comprising an electrode, the electrode comprising a current collector and a film layer disposed on at least one side of the current collector, wherein the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is less than or equal to 3%; the current collector comprises at least one first metal foil layer, the average grain size of the first metal foil layer being 5nm-50nm, and the proportion of grains with a grain size less than 80nm in the first metal foil layer being greater than or equal to 90%.

[0006] The proportion of grains with a size smaller than 80 nm in the first metal foil layer falls within the aforementioned range, indicating a high grain boundary density in the current collector. This effectively hinders dislocation movement, improves the tensile strength of the current collector, and better withstands the expansion forces of the battery cells during long cycles. Simultaneously, the high proportion of grains with a size smaller than 80 nm helps reduce the difference in fracture elongation between the current collector and the film layer, ensuring synchronized changes in their cumulative strains during battery cycle expansion. This reduces the time of electrode wrinkling and improves the battery's cycle life.

[0007] In any embodiment, the proportion of grains with a grain size of less than 30 nm in the first metal foil layer is greater than or equal to 90%.

[0008] The proportion of grains with a size of less than 30nm in the first metal foil layer is within the above range, which further improves the tensile strength of the current collector, reduces the difference in fracture elongation between the current collector and the film layer, delays the time of electrode wrinkling, and improves the cycle life of the battery.

[0009] In any embodiment, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is greater than 0% and less than 1%, and can be greater than 0 and less than or equal to 0.7%.

[0010] The absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is within the above range, which can further reduce the phenomenon of inconsistent expansion between the current collector and the film during battery cycle expansion, reduce the risk of electrode wrinkling, and improve the cycle life of the battery.

[0011] In any embodiment, the elastic deformation range of the electrode is greater than or equal to 1%, wherein the elastic deformation range refers to the strain range corresponding to the reduction of the tangential modulus to 30 GPa.

[0012] In the embodiments of this application, the first metal foil layer has a small grain size and a large proportion of grains with a grain size of less than 80nm. The grain boundary density in the first metal foil layer is high, and the grain boundaries strongly hinder the movement of dislocations. This makes it necessary to generate higher energy for the deformation of the current collector, which is beneficial to improve the tensile strength of the current collector, increase the elastic deformation range of the electrode, delay the time when the electrode wrinkles, and improve the cycle life of the battery.

[0013] In any embodiment, under test conditions of room temperature and a tensile speed of 50±0.5 mm / min, the tensile strength of the electrode is 650 MPa-2250 MPa.

[0014] The aforementioned electrode has high tensile strength, which helps improve the cell's resistance to expansion and enhances the cycle life of individual battery cells.

[0015] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the electrode is 1%-8%.

[0016] The aforementioned electrode has a high elongation at break, indicating that the electrode has good deformation ability, which is beneficial to improving the cycle life of the battery cell.

[0017] In any embodiment, under room temperature testing conditions, the current collector has a bending resistance of 1 to 10 times.

[0018] The aforementioned current collector exhibits a high number of bending cycles, indicating that it has good bending resistance, which helps improve the bending resistance of the electrode in the battery cell and improve the cycle life of the battery cell.

[0019] In any embodiment, the electrode is a negative electrode, and the film layer of the negative electrode includes a negative electrode active material, which includes at least one of carbon-based material or silicon-based material.

[0020] In any embodiment, the battery cell includes one or more wound cells, the thickness of which is 10mm-50mm.

[0021] Wound cells with thicknesses within the aforementioned range exhibit high energy density, but they also require high expansion forces during cycling, making the current collector prone to cracking and ultimately leading to cell failure. The battery cell provided in this application embodiment achieves both high energy density and reduces the probability of current collector cracking, while also delaying crack initiation time, thus balancing battery energy density and cycle life.

[0022] In any embodiment, the battery cell includes one or more wound cells, the wound cells including corner areas and straight areas, the ratio of the length of the straight area to the length of the corner area of ​​the wound cell being 1-10.

[0023] The battery cells in this application embodiment are suitable for this cell design, and can balance the high energy density and cycle life of the battery cells.

[0024] In any embodiment, the density of one side of the electrode is 20 mg / 1540.25 mm. 2 -200mg / 1540.25mm 2 The option is 50mg / 1540.25mm. 2 -200mg / 1540.25mm 2 .

[0025] The electrode in this embodiment has high tensile strength and can withstand the large expansion force of high areal density electrode (i.e., thick coated electrode), which is beneficial to further improve the energy density of the battery.

[0026] In any embodiment, the compaction density of the electrode is 0.9 g / cm³. 3 -1.8g / cm 3 1.3g / cm³ is an optional value. 3 -1.8g / cm 3 .

[0027] The electrode sheets in this application have both high compaction density and good fracture resistance, which is beneficial to improving the energy density and cycle life of the battery cell.

[0028] In any embodiment, the thickness of the film layer on one side of the electrode is 20μm-150μm, and can be selected as 40μm-80μm.

[0029] The electrode in this embodiment has high tensile strength and can withstand the large cyclic expansion force of the thick-coated electrode, which is beneficial to further improve the energy density of the battery.

[0030] In any implementation, the full discharge margin of the battery cell is 70%-105%.

[0031] The battery cells in the embodiments of this application are particularly suitable for high group margin designs, which improve battery life while increasing battery energy density.

[0032] In any embodiment, the elastic deformation range of the electrode is greater than 1% and less than or equal to 2%, wherein the elastic deformation range refers to the strain range corresponding to the reduction of the tangential modulus to 30 GPa.

[0033] In any embodiment, under test conditions of room temperature and a tensile speed of 50±0.5 mm / min, the tensile strength of the electrode is 917 MPa-1950 MPa.

[0034] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the electrode is 2%-6%.

[0035] In any embodiment, the average grain size of the first metal foil layer is 8 nm-16 nm.

[0036] In the embodiments of this application, the average grain size of the first metal foil layer is within the above-mentioned range, which is beneficial for the current collector to achieve plastic deformation through grain boundary slip and dislocation movement. The high density of grain boundaries can effectively disperse stress, so that the fracture elongation between the current collector and the film layer is matched, delaying the time of electrode wrinkling and improving the cycle life of the battery.

[0037] In any embodiment, the first metal foil layer includes a first element, which includes one or more of W, Mo, Cr, Ag, Au, Pt, Zr, Nb, Mn, Co, Ni, Fe, and Cu.

[0038] The aforementioned metallic elements possess both high strength and plasticity, which helps to reduce irreversible deformation of the electrode sheet during long cycles and improve the cycle life of the battery cell.

[0039] In any implementation, the total thickness of the first metal foil layer accounts for 30%-100% based on the total thickness of the current collector.

[0040] In the embodiments of this application, the first metal foil layer with a certain thickness ratio has a small grain size, which is beneficial to increase the energy threshold for deformation of the current collector, thereby increasing the elastic deformation range of the current collector, reducing the difference in fracture elongation between the current collector and the film layer, which is beneficial for the two to maintain synchronous changes during battery cycle expansion, delaying the time of electrode wrinkling, and improving the cycle life of the battery.

[0041] In any embodiment, the first metal foil layer comprises a face-centered cubic structure, wherein the texture coefficient of the (111) crystal plane in the first metal foil layer accounts for 30%-80%.

[0042] Based on the sum of the intensities of the diffraction peaks in the X-ray diffraction spectrum of the first metal foil layer, a high proportion of the texture coefficient of the (111) crystal plane means that the (111) crystal plane accounts for a high proportion of the grains in the first metal foil layer. This is beneficial for the current collector to withstand high tensile stress while sliding with the help of the (111) crystal plane, giving the current collector high resistance to ductility, reducing irreversible deformation of the electrode during long cycles, and improving the cycle life of the battery cell.

[0043] In any embodiment, the texture factor of the (200) crystal plane in the first metal foil layer accounts for 10%-50%.

[0044] The proportion of the texture coefficient of the (200) crystal plane in the first metal foil layer within the above range often means that the first metal foil layer includes new phases. Through the coordinated deformation between multiple phases, the current collector’s resistance to ductility is improved, and the current collector’s resistance to tensile deformation is enhanced.

[0045] In any embodiment, the first metal foil layer comprises an iron-nickel-based alloy, wherein the mass content of iron in the first metal foil layer is less than 65%.

[0046] The iron content in the first metal foil layer within the above range can balance the strength and bending resistance of the current collector, reduce irreversible deformation of the electrode during long cycles, and improve the cycle life of the battery cell.

[0047] In any embodiment, the first metal foil layer comprises an iron-nickel-based alloy, wherein the mass content of iron in the first metal foil layer is 10%-60% and the mass content of nickel in the first metal foil layer is 40%-90%.

[0048] In any embodiment, the first metal foil layer includes Ni, NiFe3, FeNi3, Fe3Ni2, and Ni. 0.64 Fe 0.36 One or more of the Ni1Fe1 phase.

[0049] The presence of the aforementioned phases in the first metal foil layer is beneficial to further improve the compressive strength and ductility of the current collector, increase the elastic deformation range of the current collector, reduce the difference in fracture elongation between the current collector and the film layer, reduce the phenomenon of inconsistent expansion between the current collector and the film layer during battery cycle expansion, reduce the risk of electrode wrinkling, and improve the cycle life of the battery.

[0050] In any implementation, the total thickness of the first metal foil layer accounts for 30%-85% based on the total thickness of the current collector.

[0051] In any embodiment, the first metal foil layer comprises a face-centered cubic structure, wherein the texture coefficient of the (111) crystal plane in the first metal foil layer accounts for 30%-80%.

[0052] In any embodiment, the texture factor of the (200) crystal plane in the first metal foil layer accounts for 25%-40%.

[0053] In any embodiment, the second metal foil layer includes a second element, which includes one or more of Cu, Ag, and Au, and the mass content of the second element in the second metal foil layer is greater than or equal to 90%.

[0054] The second element is a highly ductile metallic element that can effectively improve the current collector's resistance to ductility and enhance the cycle life of the battery cell without significantly sacrificing the current collector's strength.

[0055] In any embodiment, the average grain size of the second metal foil layer is greater than or equal to 40 nm.

[0056] The second metal foil layer, with its relatively large grains, exhibits higher degree of grain boundary tortuosity. This necessitates overcoming greater resistance during crack propagation, resulting in more crystal plane slip. This reduces the probability of brittle fracture of the current collector during cycling, effectively improving its elongation at break and lowering the likelihood of battery failure due to current collector breakage within the inner winding of the cell. Maintaining the thickness of the second metal foil layer within the aforementioned range helps balance the current collector's compressive strength and ductility, reducing irreversible deformation of the electrode containing the current collector during long-term cycling and improving the battery's cycle life.

[0057] In any embodiment, the second metal foil layer includes copper, the mass content of Cu in the second metal foil layer is greater than or equal to 90%, and the average grain size of the second metal foil layer is 40nm-150nm.

[0058] Using pure copper in the second metal foil layer is beneficial for further improving the ductility of the second metal foil layer and improving the plasticity of the current collector.

[0059] In any embodiment, the total thickness of the second metal foil layer is 15%-70% based on the total thickness of the current collector.

[0060] The thickness ratio of the second metal foil layer within the above range is beneficial to balance the compressive strength and ductility resistance of the current collector, reduce the irreversible deformation of the electrode including the current collector during long cycles, and improve the cycle life of the battery.

[0061] In any embodiment, the average grain size of the second metal foil layer is 40nm-100nm.

[0062] In any embodiment, based on the total mass of the current collector, the mass percentage of Ni is 25%-70%, the mass percentage of Fe is 1%-40%, and the mass percentage of Cu is 15%-65%.

[0063] In any implementation, the coefficient of variation of the current collector thickness is less than or equal to 0.5%.

[0064] In any implementation, the coefficient of variation of the surface density of the current collector is less than or equal to 0.5%.

[0065] When the coefficient of variation of the current collector thickness or areal density is within the above range, the non-uniformity of the current collector thickness or areal density can be reduced, the possibility of current collector fracture caused by stress concentration can be reduced, the fracture elongation of the current collector can be improved, the cumulative strain that the battery can withstand can be increased, and the cycle life of the battery can be improved.

[0066] In any implementation, the range of nickel content in the current collector is less than 5%.

[0067] The range of nickel content in the current collector being within the above range means that the composition of different regions in the current collector is uniform and there is no obvious component segregation. This is beneficial to reducing the probability of local stress and strain concentration or accumulation, improving the consistency of current collector performance, and improving the cycle life of the battery cell.

[0068] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the tensile strength of the current collector is 700 MPa-2200 MPa.

[0069] The aforementioned current collector has high tensile strength, which helps improve the cell's resistance to expansion and enhances the cycle life of individual battery cells.

[0070] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 1%-8%.

[0071] The aforementioned current collector has a high elongation at break, indicating that the current collector has good plasticity, which helps to improve the cycle life of the battery cell.

[0072] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the tensile strength of the current collector is 967 MPa-1900 MPa.

[0073] In any embodiment, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 2%-6%.

[0074] In any embodiment, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

[0075] The battery cells in this application are particularly suitable for battery systems including silicon-based materials, which is beneficial for wound cells to have good cycle life at high energy density.

[0076] In any embodiment, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material is a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

[0077] The embodiments of this application are beneficial to extending the cycle life of wound cells containing carbon-based materials while maintaining a certain energy density.

[0078] In any embodiment, the battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

[0079] The battery cells in this application are particularly suitable for battery systems including silicon-based materials, which is beneficial for stacked cells to have good cycle life at high energy density.

[0080] In any embodiment, the battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material is a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

[0081] The embodiments of this application are beneficial to extending the cycle life of stacked cells containing carbon-based materials while maintaining a certain energy density.

[0082] The second aspect of this application provides a battery device including the battery cell provided in the first aspect of this application, wherein the battery device includes at least one of a battery module, a battery pack, and an energy storage device.

[0083] A third aspect of this application also provides an electrical device, which includes a single battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application. Attached Figure Description

[0084] 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.

[0085] Figure 1 This is a tensile stress-strain curve diagram of (a) the current collector and (b) the electrode in one embodiment of this application;

[0086] Figure 2 These are tensile stress-strain curves of (a) the current collector and (b) the electrode in the prior art;

[0087] Figure 3 This is a schematic diagram of a current collector according to one embodiment of this application;

[0088] Figure 4 This is an X-ray diffraction pattern of the first metal foil layer according to an embodiment of this application;

[0089] Figure 5 This is a schematic diagram of a wound battery cell according to one embodiment of this application;

[0090] Figure 6 This is a schematic diagram of one embodiment of the battery cell of this application;

[0091] Figure 7 This is an exploded view of one embodiment of the battery cell of this application;

[0092] Figure 8 This is a schematic diagram of one embodiment of the battery module of this application;

[0093] Figure 9 This is a schematic diagram of one embodiment of the battery pack of this application;

[0094] Figure 10 yes Figure 9 An exploded view of an embodiment of the battery pack shown;

[0095] Figure 11This is a schematic diagram of one embodiment of an electrical device that uses the battery cell of this application as a power source.

[0096] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate, 6 Winded cell, 61 Electrode sheet, 10 Current collector, 101 First metal foil layer, 102 Second metal foil layer, 103 Passivation layer. Detailed Implementation

[0097] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0103] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0104] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0105] Unless otherwise specified, 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 this application.

[0106] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a battery cell, including but not limited to lithium ions.

[0107] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0108] As battery usage time increases, some batteries exhibit lithium plating during long-term cycling. Disassembly studies reveal that this phenomenon is related to the wrinkling of the electrodes during long-term cycling, leading to an increased ion diffusion path and increased electrode polarization. This wrinkling of the electrodes during cycling is associated with irreversible deformation during long-term cycling, negatively impacting the battery's cycle life and safety performance.

[0109] Based on this, this application provides a battery cell, the battery cell including an electrode, the electrode including a current collector and a film layer disposed on at least one side of the current collector, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is less than or equal to 3%; the current collector includes at least one first metal foil layer, the average grain size of the first metal foil layer is 5nm-50nm, and the proportion of grains with a grain size of less than 80nm in the first metal foil layer is greater than or equal to 90%.

[0110] In this application, room temperature refers to 25±5℃.

[0111] The elongation at break of the electrode and current collector can be obtained by testing the tensile fracture curve of the specimens at room temperature. Specific testing methods can be found in GB / T5230-1995 "Electrolytic Copper Foil". As an example, at least four specimens with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm should be obtained. The specimens should be continuously loaded at a tensile speed of 50±0.5 mm / min at room temperature until fracture. Please refer to [reference needed]. Figure 1 A tensile stress-strain curve of the specimen is plotted with the tensile strain of the specimen as the horizontal axis (x-axis) and the tensile stress of the specimen as the vertical axis (y-axis, unit: MPa). The strain corresponding to the specimen at tensile fracture is taken as the elongation at break of the specimen, and the highest stress during the tensile process is taken as the tensile strength of the specimen. The electrode specimen is obtained from the film layer region of the electrode, while the current collector specimen is obtained by removing the film layer from the electrode. It can be understood that the electrode specimen can be obtained from a freshly prepared electrode or from an electrode disassembled from a battery. The tensile strength of the electrode depends on the tensile strength of the current collector. To maintain comparability between electrode specimens, the tensile stress of the electrode specimen is calculated by dividing the tensile load borne by the specimen by the cross-sectional area of ​​the current collector. The cross-sectional area of ​​the current collector is calculated by multiplying the current collector width by the thickness, and the thickness of the current collector is measured using a micrometer.

[0112] In some embodiments, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode can be selected as 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any value range between the two.

[0113] The difference between the room temperature elongation at break of the electrode and the current collector is within the above range, indicating that the deformation behavior of the electrode and the current collector is highly consistent under stress. The deformation of the two can proceed synchronously during battery cycling, which helps to reduce stress concentration and interface delamination caused by asynchronous deformation, reduce the risk of electrode wrinkling and breakage, and improve the cycle life of the battery.

[0114] In some embodiments, the current collector is a single-layer structure comprising only a first metal foil layer. That is, based on the total thickness of the current collector, the total thickness of the first metal foil layer accounts for 100%, and no obvious delamination occurs along the thickness direction of the current collector.

[0115] In some implementations, such as Figure 3 As shown, the current collector has a multilayer structure. That is, the current collector is composed of two, three, four or more foil layers. In multilayer current collectors, one or more of the following characteristics—components, component ratios, crystal structure, and grain morphology—exhibit significant differences in different regions along the thickness direction, causing the current collector to exhibit layered characteristics under at least some specific characterization. It is understood that the multilayer structure of the current collector is not limited to the morphological layering shown under a microscope or scanning electron microscope, but may also be revealed through component characterization (such as energy dispersive spectroscopy combined with scanning electron microscopy), phase characterization (metallography), or grain characterization (backscattered electron diffraction).

[0116] In some embodiments, the average grain size of the foil layer can be tested using any method known in the art. For example, X-ray diffraction (XRD) tests can be performed on different foil layers in the current collector to analyze the average grain size of the foil layer. As an example, at room temperature, using CuKα rays as the X-ray source, a scanning speed of 2° / min, and a scanning range of 10°-90°, an X-ray diffraction pattern is measured using an X-ray diffractometer. The peak with the highest diffraction intensity in the X-ray diffraction pattern is used as a reference, and the average grain size is calculated using the Scherrer formula D = Kλ / (βcosθ), where D is the average grain size, K is the Scherrer constant (0.89), λ is the X-ray wavelength (selectably 0.154 nm), β is the full width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle. Figure 4Taking the foil layer shown as an example, Figure 4 The peak with the highest diffraction intensity is located between 43.5° and 44.8° at a diffraction angle 2θ. Therefore, this peak is used to calculate the average grain size of the foil layer. It is understandable that X-ray diffraction (XRD) tests on different foil layers in the current collector can be achieved by selectively testing different foil layers in the current collector, or by etching other foil layers in the current collector to obtain the corresponding foil layer for XRD testing.

[0117] In some embodiments, the average grain size of the first metal foil layer is 5nm, 6nm, 7nm, 8nm, 8.6nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 15.8nm, 16nm, 17nm, 18nm, 19nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, or any value between the two.

[0118] Studies have shown that the average grain size of the first metal foil layer in the current collector is 5nm-50nm, which increases the grain boundary area. This hinders the deformation of the current collector, requiring higher loads to induce corresponding deformation. This increases the energy threshold for deformation in the current collector, reduces the difference in fracture elongation between the current collector and the film layer, and helps them maintain synchronous changes during battery cycle expansion. It also reduces the difference in accumulated strain between the two, delays the occurrence of electrode wrinkling, and improves the cycle life of the battery.

[0119] In some embodiments, the proportion of grains with a grain size of less than 80 nm in the first metal foil layer is greater than or equal to 90%.

[0120] The proportion of grains with a size less than 80 nm in the first metal foil layer can be tested using any method known in the art. For example, a transmission electron microscope (TEM) can be used to characterize the grain size of the first metal foil layer in the current collector. Ten points are randomly selected within the scanning area, and ten adjacent grains are randomly selected from each point. The maximum diameter of each grain is measured as the size of that grain, and the maximum diameter is the longest distance through the centroid of the grain. A total of no less than 100 grains are identified. The proportion of grains with a size less than 80 nm in the first metal foil layer is calculated by dividing the number of grains with a size less than 80 nm by the total number of counted grains.

[0121] In some embodiments, the percentage of grains with a grain size of less than 80 nm in the first metal foil layer can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any value range between the two.

[0122] The proportion of grains with a size smaller than 80 nm in the first metal foil layer falls within the aforementioned range, indicating a high grain boundary density in the current collector. This effectively hinders dislocation movement, improves the tensile strength of the current collector, and better withstands the expansion forces of the battery cells during long cycles. Simultaneously, the high proportion of grains with a size smaller than 80 nm helps reduce the difference in fracture elongation between the current collector and the film layer, ensuring synchronized changes in their cumulative strains during battery cycle expansion. This reduces the time of electrode wrinkling and improves the battery's cycle life.

[0123] In some embodiments, the proportion of grains with a grain size of less than 30 nm in the first metal foil layer is greater than or equal to 90%.

[0124] In some embodiments, the percentage of grains with a grain size of less than 30 nm in the first metal foil layer can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any value range between the two.

[0125] The proportion of grains with a size of less than 30nm in the first metal foil layer is within the above range, which further improves the tensile strength of the current collector, reduces the difference in fracture elongation between the current collector and the film layer, delays the time of electrode wrinkling, and improves the cycle life of the battery.

[0126] In some embodiments, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is greater than 0% and less than 1%, and may be greater than 0 and less than or equal to 0.7%.

[0127] The absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is within the above range, which can further reduce the phenomenon of inconsistent expansion between the current collector and the film during battery cycle expansion, reduce the risk of electrode wrinkling, and improve the cycle life of the battery.

[0128] In some embodiments, the elastic deformation range of the electrode is greater than or equal to 1%.

[0129] The elastic deformation range of the electrode can be obtained from the electrode's tensile stress-strain curve. Calculate the slope of each point on the tensile stress-strain curve, i.e., calculate the first derivative of the tensile stress with respect to the strain, as the tangent modulus of the electrode at different strains. Plot the tangent modulus-strain curve of the sample with the tensile strain of the specimen as the horizontal axis (x-axis) and the first derivative of the tensile stress with respect to the strain as the vertical axis (y-axis, unit: GPa), as shown below. Figure 1 and Figure 2The curve plotted at the "-" point is shown. The elastic deformation range refers to the strain range corresponding to the decrease of the tangent modulus to 30 GPa. Figure 1 (b) For example, the strain A corresponding to the decrease of the tangent modulus to 30 GPa in the tangent modulus-strain curve is the elastic deformation range.

[0130] The tangent modulus refers to the slope of the tensile stress-strain curve at each point, i.e., the ratio of the stress change to the strain change. It characterizes the sensitivity of stress to strain changes during electrode stretching. A larger tangent modulus indicates greater sensitivity of stress to strain changes; in other words, the lower the electrode strain caused by the same applied load. When the tangent modulus is essentially zero, the material yields. Under external force, the material strain increases while the stress remains essentially constant, and the material loses its ability to resist deformation. Within the elastic deformation range, the electrode possesses a higher tangent modulus to resist plastic deformation.

[0131] In some embodiments, the elastic deformation range of the electrode can be selected as 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any value range between the two.

[0132] Increasing the elastic deformation range of the electrode is beneficial for improving its resistance to plastic deformation and reducing wrinkling. However, the applicant discovered during the research process that electrode wrinkling is not solely dependent on the elastic deformation range of the electrode. The electrode is a composite material made of a current collector and a film layer. During battery cycling, the current collector in existing technologies undergoes significant irreversible deformation, while the film layer maintains high deformation reversibility. The large difference in cumulative strain between the two during battery cycling leads to wrinkling of the electrode.

[0133] In the embodiments of this application, the first metal foil layer has a small grain size and a large proportion of grains with a grain size of less than 80nm. The grain boundary density in the first metal foil layer is high, and the grain boundaries strongly hinder the movement of dislocations. This makes it necessary to generate higher energy for the deformation of the current collector, which is beneficial to improve the tensile strength of the current collector, increase the elastic deformation range of the electrode, delay the time when the electrode wrinkles, and improve the cycle life of the battery.

[0134] In some embodiments, the elastic deformation range of the electrode is greater than 1% and less than or equal to 2%.

[0135] An excessively high elastic deformation range of the electrode indicates that the electrode can undergo large reversible deformation during cycling. However, the deformation behavior of the current collector may not be completely synchronized, leading to local stress concentration. This adversely affects the bending resistance of the current collector and increases the risk of electrode wrinkling and breakage.

[0136] In some embodiments, under test conditions of room temperature and a tensile speed of 50±0.5 mm / min, the tensile strength of the electrode is 650 MPa-2250 MPa, optionally 917 MPa-1950 MPa.

[0137] The tensile strength of an electrode at room temperature can be obtained through a tensile fracture curve test. The specific test method can be found in GB / T5230-1995 "Electrolytic Copper Foil" standard. As an example, at least four electrode samples with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm are cut. These samples are continuously loaded at a tensile speed of 50±0.5 mm / min at room temperature until fracture. It is understood that the electrode sample is a composite structure including a current collector and a film layer. The tensile strength of the sample is calculated by dividing the tensile stress at fracture by the tensile cross-sectional area of ​​the electrode, expressed in MPa. At least four electrode samples are tested, and the average value is taken as the tensile strength of the electrode. It is understood that the electrode samples can be obtained from freshly prepared electrodes or from electrodes disassembled from batteries.

[0138] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the tensile strength of the electrode can be selected from 650 MPa, 700 MPa, 800 MPa, 900 MPa, 917 MPa, 950 MPa, 967 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa, 1950 MPa, 2000 MPa, 2100 MPa, 2200 MPa, 2250 MPa, or any range between the two.

[0139] The aforementioned electrode has high tensile strength, which helps improve the cell's resistance to expansion and enhances the cycle life of individual battery cells.

[0140] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the electrode is 1%-8%, optionally 2%-6%.

[0141] The elongation at break of the electrode at room temperature can be tested using the tensile strength test method described above.

[0142] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the electrode can be selected as 1%, 1.5%, 2%, 3%, 4%, 4.5%, 5%, 6%, 6.5%, 7%, 8%, or any range between the two.

[0143] The aforementioned electrode has a high elongation at break, indicating that the electrode has good deformation ability, which is beneficial to improving the cycle life of the battery cell.

[0144] In some embodiments, the current collector has a bending resistance of 1 to 10 times under room temperature test conditions.

[0145] The bending resistance of the current collector can be tested using methods known in the art. For example, at room temperature, the current collector sample is folded 180° and then rolled back and forth at the fold with a 1.5kg roller. After unfolding, it is observed whether cracking and light transmission occur at the fold. The number of times the rolling caused cracking and light transmission at the fold is recorded. At least ten samples are tested, and the average value is taken as the bending resistance of the current collector.

[0146] In some implementations, under room temperature testing conditions, the current collector's resistance to bending is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 times or any range between two of these values.

[0147] The aforementioned current collector exhibits a high number of bending cycles, indicating that it has good bending resistance, which helps improve the bending resistance of the electrode in the battery cell and improve the cycle life of the battery cell.

[0148] In some embodiments, the battery cell includes one or more wound cells, the electrode of the wound cell is a negative electrode, and the film layer of the negative electrode includes a negative electrode active material, which includes at least one of carbon-based material or silicon-based material.

[0149] In some embodiments, the battery cell includes one or more wound cells, wherein the thickness H of the wound cell 6 is 10mm-50mm.

[0150] In some implementations, the wound cell is formed by winding a positive electrode, a negative electrode, and a separator.

[0151] In some implementations, the battery cell includes a wound cell.

[0152] In some implementations, a single battery cell includes multiple wound cells connected in a combination of parallel, series, or mixed connections.

[0153] like Figure 5 As shown, the thickness H of the wound cell 6 can be tested using any method known in the art. For example, a wound cell sample is placed on a flat surface, and a micrometer is used to measure the thickness at the center of the sample. At least 10 wound cell samples are tested, and the average value of the test results is taken as the thickness of the wound cell. It is understood that the wound cell sample can be a freshly prepared wound cell or a wound cell obtained from disassembling a battery cell.

[0154] In some embodiments, the thickness of the wound cell can be selected as 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm or any value range between the two.

[0155] Wound cells with thicknesses within the aforementioned range exhibit high energy density, but they also require high expansion forces during cycling, making the current collector prone to cracking and ultimately leading to cell failure. The battery cell provided in this application embodiment achieves both high energy density and reduces the probability of current collector cracking, while also delaying crack initiation time, thus balancing battery energy density and cycle life.

[0156] In some embodiments, the wound cell includes a corner region and a straight region, wherein the ratio of the length of the straight region to the length of the corner region of the wound cell is 1-10.

[0157] A wound battery cell includes a corner area and a straight area. The straight area refers to the straight part formed after the positive and negative electrode plates and the separator are wound into a roll. It is the main working area of ​​the battery cell. The corner area refers to the arc-shaped part formed after the positive and negative electrode plates and the separator are wound into a roll.

[0158] In some embodiments, the ratio of the straight section length L1 to the corner section length L2 of the wound cell can be selected as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any value range between the two.

[0159] Please refer to Figure 5 The length of the straight section refers to the length of the straight section formed after the positive and negative electrode plates and the separator are wound into a coil in the wound cell, i.e., L1; the length of the winding section refers to the normal distance from the intersection of the straight section and the winding section to the tangential plane at the farthest end of the winding section, i.e., L2.

[0160] Battery cells with a straight section length to corner section length ratio within the aforementioned range have smaller corner radii. While this improves the space utilization of the battery casing, it also makes the inner ring of the cell prone to significant bending, leading to cracks in the inner ring electrode sheets. The battery cells in the embodiments of this application are suitable for this cell design, achieving a balance between high energy density and cycle life.

[0161] In some embodiments, the electrode has a single-sided density of 20 mg / 1540.25 mm. 2 -200mg / 1540.25mm 2 The option is 50mg / 1540.25mm. 2 -200mg / 1540.25mm 2 .

[0162] In some embodiments, the electrode has a single-sided density of 20 mg / 1540.25 mm. 2 30mg / 1540.25mm 2 40mg / 1540.25mm 2 50mg / 1540.25mm 2 60mg / 1540.25mm 2 70mg / 1540.25mm 2 80mg / 1540.25mm 2 90mg / 1540.25mm 2 100mg / 1540.25mm 2 110mg / 1540.25mm 2 120mg / 1540.25mm 2 130mg / 1540.25mm 2 140mg / 1540.25mm 2 150mg / 1540.25mm 2 160mg / 1540.25mm 2 170mg / 1540.25mm 2 180mg / 1540.25mm 2 190mg / 1540.25mm 2 200mg / 1540.25mm 2 Or the range of values ​​between any two.

[0163] In this application, the unilateral density of the electrode sheet has a meaning known in the art and can be tested using methods known in the art. For example, the battery is placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.0V. The battery is then disassembled to obtain the electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S1. The mass of these pieces is weighed and recorded as M1. Then, the film layer of the weighed electrode sheet is removed, and the weight of the current collector is weighed and recorded as M0. The unilateral density of a single-sided coated electrode sheet is (M1-M0) / S1, and the unilateral density of a double-sided coated electrode sheet is (M1-M0) / (2×S1). To ensure the accuracy of the test results, multiple sets (e.g., 10 sets) of samples can be tested, and the average value can be calculated as the test result.

[0164] The electrode in this embodiment has high tensile strength and can withstand the large expansion force of high areal density electrode (i.e., thick coated electrode), which is beneficial to further improve the energy density of the battery.

[0165] In some embodiments, the compaction density of the electrode is 0.9 g / cm³. 3 -1.8g / cm 3 1.3g / cm³ is an optional value. 3 -1.8g / cm 3 .

[0166] The compaction density of the electrode can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.0V. The battery is then disassembled to obtain the electrode. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode is dried, and it is cut into small circular pieces with an area of ​​S. The mass of each piece is recorded as W1, and the thickness of the electrode is measured using a micrometer. The film layer of the weighed electrode is then wiped off, and the mass of the current collector is recorded as W2. The thickness of the current collector is measured using a micrometer. The compaction density of the electrode is then PD = (W1 - W2) / [(T1 - T2) × S].

[0167] In some embodiments, the compaction density of the electrode sheet may be selected as 0.9 g / cm³. 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.35g / cm 3 1.4g / cm 3 1.45g / cm 3 1.5g / cm 3 1.55g / cm 31.6g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 Or the range of values ​​between any two.

[0168] The electrode sheets in this application have both high compaction density and good fracture resistance, which is beneficial to improving the energy density and cycle life of the battery cell.

[0169] In some embodiments, the thickness of the film layer on one side of the electrode is 20μm-150μm, and can be selected as 40μm-80μm.

[0170] In some embodiments, the thickness of the single-sided film layer of the electrode can be selected as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm or any value range between the two.

[0171] The thickness of the film on one side of the electrode can be tested using methods known in the art. As an example, the film thickness in the cross-section of the electrode is measured using a scanning electron microscope.

[0172] The electrode in this embodiment has high tensile strength and can withstand the large cyclic expansion force of the thick-coated electrode, which is beneficial to further improve the energy density of the battery.

[0173] In some embodiments, the full discharge margin of the battery cell is 70%-105%.

[0174] Group margin refers to the ratio of the actual internal cross-sectional area occupied by the battery cell to the maximum internal cross-sectional area of ​​the battery cell. In battery design, group margin is used to characterize the space filling degree within the battery cell, that is, the degree to which the cell is packed within the battery casing. In this application, full discharge refers to the state of the battery cell discharged to the cutoff voltage (usually the minimum allowable voltage of the battery). Full discharge group margin is calculated by dividing the total thickness of the wound cells in the battery cell by the inner width of the battery cell casing in the direction of the wound cell thickness. Because the cell will rebound during cycling, causing the casing to expand, the full discharge group margin of the battery cell may be greater than or equal to 100%.

[0175] In some implementations, the full discharge margin of a single battery cell can be selected as 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, or any value range between the two.

[0176] A cell's full-discharge margin within the aforementioned range indicates high space filling within the cell, which, while beneficial for increasing energy density, also makes it prone to crack failure. The cell designs in this application are particularly suitable for high-margin cell designs, improving both energy density and battery life.

[0177] In some embodiments, the average grain size of the first metal foil layer is 8nm-16nm.

[0178] In the embodiments of this application, the average grain size of the first metal foil layer is within the above-mentioned range, which is beneficial for the current collector to achieve plastic deformation through grain boundary slip and dislocation movement. The high density of grain boundaries can effectively disperse stress, so that the fracture elongation between the current collector and the film layer is matched, delaying the time of electrode wrinkling and improving the cycle life of the battery.

[0179] In some embodiments, the first metal foil layer includes a first element, which includes one or more of W, Mo, Cr, Ag, Au, Pt, Zr, Nb, Mn, Co, Ni, Fe, and Cu.

[0180] The elemental composition of the first metal foil layer can be obtained by energy dispersive spectroscopy (EDS) or plasma atomic emission spectrometry (PISA). The mass percentage of the first element in the first metal foil layer can be obtained by separating the first metal foil layer from the current collector and analyzing it using PISA.

[0181] The aforementioned metallic elements possess both high strength and plasticity, which helps to reduce irreversible deformation of the electrode sheet during long cycles and improve the cycle life of the battery cell.

[0182] In some embodiments, the first metal foil layer mainly includes any one of the first elements, that is, the first metal foil layer is a pure metal foil layer.

[0183] In some embodiments, the first metal foil layer primarily comprises at least two of the first elements, i.e., the first metal foil layer is an alloy layer. It is understood that the alloy layer may include any one of a solid solution, eutectoid, eutectic, or compound (intermetallic compound), or these may coexist.

[0184] The elemental composition of the first metal foil layer can be obtained by energy dispersive spectroscopy (EDS) or plasma atomic emission spectrometry (PISA). The mass percentage of the first element in the first metal foil layer can be obtained by separating the first metal foil layer from the current collector and analyzing it using PISA.

[0185] In some embodiments, the total thickness of the first metal foil layer accounts for 30%-100% based on the total thickness of the current collector.

[0186] In some implementations, the percentage of the total thickness of the first metal foil layer, based on the total thickness of the current collector, can be tested using any method known in the art. The percentage of the total thickness of the first metal foil layer is the ratio of the total thickness of the first metal foil layer to the thickness of the current collector. The total thickness of the first metal foil layer can be measured when observing the layered structure of the current collector.

[0187] In some implementations, based on the total thickness of the current collector, the percentage of the total thickness of the first metal foil layer can be selected as 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90%, 100%, or any value between the two.

[0188] In the embodiments of this application, the first metal foil layer with a certain thickness ratio has a small grain size, which is beneficial to increase the energy threshold for deformation of the current collector, thereby increasing the elastic deformation range of the current collector, reducing the difference in fracture elongation between the current collector and the film layer, which is beneficial for the two to maintain synchronous changes during battery cycle expansion, delaying the time of electrode wrinkling, and improving the cycle life of the battery.

[0189] In some embodiments, the total thickness of the first metal foil layer accounts for 30%-85% based on the total thickness of the current collector.

[0190] Within the above-mentioned range, the total thickness of the first metal foil layer can increase the elastic deformation range of the current collector through the coordinated effect of different structures or components in different foil layers, reduce the difference in fracture elongation between the current collector and the film layer, reduce the phenomenon of inconsistent expansion between the current collector and the film layer during battery cycle expansion, reduce the risk of electrode wrinkling, and improve the cycle life of the battery.

[0191] In some embodiments, the first metal foil layer includes a face-centered cubic structure, and the texture coefficient of the (111) crystal plane in the first metal foil layer accounts for 30%-80%.

[0192] (111) The proportion of the texture coefficient of the crystal plane can be obtained by X-ray diffraction test of the first metal foil layer.

[0193] The X-ray diffraction pattern of the first metal foil layer was compared with the standard pattern. The phase and crystal plane corresponding to the diffraction peak of the first metal foil layer were analyzed. The texture coefficient M of the (111) crystal plane was calculated with reference to Equation I.

[0194] M(111)=I(111) / IR(111) (Equation I)

[0195] Where I(111) is the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum obtained by actual testing, and IR(111) is the standard intensity of the (111) crystal plane in the standard XRD spectrum of the main phase.

[0196] (111) The proportion of the texture coefficient P of the crystal plane is calculated by Equation II.

[0197] P(111)=M(111) / ∑M(hkl) (Equation II)

[0198] Where M(hkl) is the texture coefficient of each crystal plane of the main phase in the X-ray diffraction spectrum obtained by actual testing.

[0199] The following is for reference Figure 4 The texture coefficient ratio P(111) of the (111) crystal plane is explained. In some embodiments, the X-ray diffraction pattern of the first metal foil layer of the current collector is as follows: Figure 4 As shown, the diffraction peaks mainly include those located at 44.0°±0.8°, 51.2°±0.8°, 76.0°±0.5°, and 92.0°±1.0°, respectively. Phase analysis shows that these diffraction peaks correspond to Ni. 4.00 The (111), (200), (220), and (311) crystal planes are shown in the XRD standard card (reference code: 96-901-3035). Therefore, the texture factor P(111) of the (111) crystal plane can be calculated by the following formula.

[0200] P(111)=M(111) / [M(111)+M(200)+M(220)+M(311)]=[I(111) / IR(111)] /

[0201]

[I(111) / IR(111)]+[I(200) / IR(200)]+[I(220) / IR(220)]+[I(311) / IR(311)]

[0202] IRP(hkl) is the ratio of the intensity of the diffraction peak of the (hkl) crystal plane to the intensity of the highest diffraction peak in the XRD standard pattern, which can be found in the XRD standard pattern.

[0203] It is understandable that a texture factor ratio of 25% or greater on a crystal plane means that the crystal plane has a high degree of orientation.

[0204] In some implementations, the texture factor of the (111) crystal plane can be selected as 30%, 40%, 50%, 60%, 70%, 80%, or any value between the two.

[0205] Face-centered cubic (FCC) is a typical metallic crystal structure. In its unit cell, each vertex has one atom, and each face center has one atom. Compared to body-centered cubic (BCC), FCC has more slip planes and slip directions, and the atomic arrangement in FCC is more compact. This compact arrangement helps the material deform under stress through a greater number of slip systems, preventing fracture.

[0206] In a face-centered cubic cell structure, the (111) plane is both its close-packed plane and its slip plane. This means that during the plastic deformation of the foil layer, dislocations are more likely to move on the (111) plane; at the same time, the atomic density on the (111) plane is high and the bonding strength between atoms is high, which enables the foil layer to withstand higher stress during the plastic deformation process.

[0207] Based on the sum of the intensities of the diffraction peaks in the X-ray diffraction spectrum of the first metal foil layer, a high proportion of the texture coefficient of the (111) crystal plane means that the (111) crystal plane accounts for a high proportion of the grains in the first metal foil layer. This is beneficial for the current collector to withstand high tensile stress while sliding with the help of the (111) crystal plane, giving the current collector high resistance to ductility, reducing irreversible deformation of the electrode during long cycles, and improving the cycle life of the battery cell.

[0208] In some embodiments, the texture factor of the (200) crystal plane in the first metal foil layer accounts for 10%-50%, and can be selected as 25%-40%.

[0209] The proportion of texture coefficient of (200) crystal plane can be obtained by referring to the (111) texture coefficient proportion test above.

[0210] It is understandable that if the texture coefficient of a crystal face in this crystal structure is close to or greater than 25%, it means that the orientation degree of the crystal face is high.

[0211] In some embodiments, the texture factor percentage of the (200) crystal plane can be selected as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value range between the two.

[0212] Studies have shown that when the proportion of the texture factor of the (200) crystal plane in the first metal foil layer is within the above-mentioned range, the current collector exhibits good resistance to stretching. The reason for this is likely related to the formation of new phases in the foil layer. The proportion of the texture factor of the (200) crystal plane in a pure metal foil layer is usually low. When the proportion of the texture factor of the (200) crystal plane in the first metal foil layer is within the above-mentioned range, it often means that the first metal foil layer includes new phases. Through the coordinated deformation between multiple phases, the resistance to stretching of the current collector is improved, and the tensile deformation resistance of the current collector is enhanced.

[0213] In some embodiments, the first metal foil layer comprises an iron-nickel-based alloy, wherein the mass content of iron in the first metal foil layer is less than 65%.

[0214] In this application, iron-nickel based alloy refers to an alloy whose main constituent elements include nickel and iron.

[0215] In some embodiments, the iron-nickel-based alloy also contains impurity elements or dopants such as Cr, Si, S, P, and C.

[0216] In some embodiments, the mass content of iron in the first metal foil layer can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 62%, or any value range between the two.

[0217] Iron-nickel-based alloys exhibit high stability in electrochemical environments and are not prone to corrosion. However, studies have shown that when the mass content of iron in the first metal foil layer is within the aforementioned range, the iron-nickel-based alloy in the first metal foil layer primarily comprises a face-centered cubic (FCC) cell structure. With further increases in iron content, the cell structure of the first metal foil layer transforms into a body-centered cubic (BCC) cell structure, negatively impacting the current collector's ductility, film-forming properties, and deformability. Maintaining the iron mass content within the aforementioned range in the first metal foil layer balances the current collector's strength and bending resistance, reduces irreversible deformation of the electrode during long-cycle operation, and improves the cycle life of the battery cell.

[0218] In some embodiments, the first metal foil layer comprises an iron-nickel-based alloy, wherein the mass content of iron in the first metal foil layer is 10%-60%, and the mass content of nickel in the first metal foil layer is 40%-90%.

[0219] In some embodiments, the mass content of nickel in the first metal foil layer can be selected as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value range between the two.

[0220] Experimental results show that increasing the iron content in the face-centered cubic cell structure is beneficial to increasing the diffraction peak intensity of the (200) crystal plane, improving the bending resistance of the current collector, giving the current collector high resistance to stretching, and improving the cycle life of the battery cell.

[0221] In some embodiments, the first metal foil layer includes Ni, NiFe3, FeNi3, Fe3Ni2, and Ni. 0.64 Fe 0.36 One or more of the Ni1Fe1 phase.

[0222] The identification of the aforementioned phases can be obtained by comparing the X-ray diffraction pattern of the first metal foil layer sample with the standard pattern of the Joint Committee on Powder Diffraction Standards (JCPDS).

[0223] The presence of the aforementioned phases in the first metal foil layer is beneficial to further improve the compressive strength and ductility of the current collector, increase the elastic deformation range of the current collector, reduce the difference in fracture elongation between the current collector and the film layer, reduce the phenomenon of inconsistent expansion between the current collector and the film layer during battery cycle expansion, reduce the risk of electrode wrinkling, and improve the cycle life of the battery.

[0224] In some embodiments, the current collector has a multilayer structure, and at least one layer of the current collector is a second metal foil layer with an average grain size greater than or equal to 40 nm. The second metal foil layer includes a second element, which includes one or more of Cu, Ag, and Au. Based on the total thickness of the current collector, the total thickness of the second metal foil layer accounts for 15%-70%.

[0225] The element types of the second metal foil layer can be the same as or different from those of the first metal foil layer, but the average grain size of the second metal foil layer differs from that of the first metal foil layer. The average grain size of the second metal foil layer can be tested with reference to the average grain size of the first metal foil layer described above.

[0226] In some embodiments, the average grain size of the second metal foil layer can be selected as 40nm, 45nm, 47nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 91nm, 92nm, 93nm, 94nm, 95nm, 96nm, 97nm, 98nm, 99nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, or any value range between the two.

[0227] The second metal foil layer, with its relatively large grains, exhibits higher degree of grain boundary tortuosity. This necessitates overcoming greater resistance during crack propagation, resulting in more crystal plane slip. This reduces the probability of brittle fracture of the current collector during cycling, effectively improving its elongation at break and lowering the likelihood of battery failure due to current collector breakage within the inner winding of the cell. Maintaining the thickness of the second metal foil layer within the aforementioned range helps balance the current collector's compressive strength and ductility, reducing irreversible deformation of the electrode containing the current collector during long-term cycling and improving the battery's cycle life.

[0228] The elemental composition of the second metal foil layer can be obtained by energy dispersive spectroscopy (EDS) or plasma atomic emission spectrometry (PISA). The mass percentage of the second element in the second metal foil layer can be obtained by separating the second metal foil layer from the current collector and analyzing it using PISA.

[0229] The second element is a highly ductile metallic element that can effectively improve the current collector's resistance to ductility and enhance the cycle life of the battery cell without significantly sacrificing the current collector's strength.

[0230] In some implementations, the total thickness of the second metal foil layer accounts for 15%-70% based on the total thickness of the current collector.

[0231] In some implementations, based on the total thickness of the current collector, the total thickness percentage of the second metal foil layer can be selected as 15%, 20%, 30%, 40%, 50%, 60%, 70%, or any value range between the two.

[0232] The thickness ratio of the second metal foil layer within the above range is beneficial to balance the compressive strength and ductility resistance of the current collector, reduce the irreversible deformation of the electrode including the current collector during long cycles, and improve the cycle life of the battery.

[0233] In some embodiments, the current collector includes a first metal foil layer and a second metal foil layer that are stacked and interleaved in the thickness direction.

[0234] In some embodiments, the average grain size of the second metal foil layer is 40nm-150nm, and optionally 40nm-100nm.

[0235] In some embodiments, the average grain size of the second metal foil layer is 40 nm to 80 nm.

[0236] The average grain size of the second metal foil layer is within the above range, which makes the current collector more uniform in thickness while taking into account both strength and plasticity. This is beneficial to improving the thickness consistency of the current collector, improving the processing performance of the electrode and the cycle life of the battery.

[0237] In some embodiments, the average grain size of the second metal foil layer is 80 nm to 120 nm.

[0238] The average grain size of the second metal foil layer is within the above range, which allows the current collector to have both strength and plasticity while also giving the second metal foil layer a high surface roughness. This is beneficial to improving the bonding strength between the second metal foil layer and its adjacent layer (the first metal foil layer or film layer), and further improving the cycle stability of the battery.

[0239] In some embodiments, the mass content of copper in the second metal foil layer is greater than or equal to 90%.

[0240] In some embodiments, the mass content of copper in the second metal foil layer can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or any value range between the two.

[0241] Using pure copper in the second metal foil layer is beneficial for further improving the ductility of the second metal foil layer and improving the plasticity of the current collector.

[0242] In some embodiments, the second metal foil layer includes copper, with Cu accounting for more than or equal to 90% of the mass content in the second metal foil layer, and the average grain size of the second metal foil layer is 40nm-150nm.

[0243] In some embodiments, at least a portion of the second metal foil layer is close to the surface of the current collector.

[0244] The surface of the current collector is where the deformation is greatest during the winding and bending process, and it is also where the stress is most concentrated. Placing at least part of the second metal foil layer close to the surface of the current collector can minimize the probability of cracks forming during winding and bending, which is beneficial to improving the cycle life of the battery cell.

[0245] In some implementations, such as Figure 3 As shown, the current collector 10 includes two second metal foil layers 102 close to the surface of the current collector in the thickness direction and a first metal foil layer 101 disposed between the two second metal foil layers 102 in the thickness direction.

[0246] In some implementations, please refer to [the documentation / reference]. Figure 3 A passivation layer 103 is provided on the surface of the current collector 10.

[0247] In some embodiments, the passivation layer includes any component capable of reducing metal oxidation on the current collector surface, including but not limited to chromides and oxides.

[0248] In some embodiments, the second metal foil layer near the current collector surface mainly comprises copper, and the first metal foil layer disposed between the two second metal foil layers mainly comprises an iron-nickel alloy.

[0249] In some embodiments, based on the total mass of the current collector, the mass percentage of Ni is 25%-70%, the mass percentage of Fe is 1%-40%, and the mass percentage of Cu is 15%-65%.

[0250] In some embodiments, based on the total mass of the current collector, the mass percentage of Ni can be selected as 25%, 30%, 40%, 50%, 60%, 70%, or any value between two of these; the mass percentage of Fe can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value between two of these; and the mass percentage of Cu can be selected as 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or any value between two of these.

[0251] Current collectors with a composition within the above range have both good tensile strength and elongation at break. Electrodes prepared using this current collector have a small difference in elongation at break between the current collector and the film layer, which helps to reduce the risk of electrode wrinkling and improve the cycle life of the battery.

[0252] In some embodiments, the coefficient of variation of the current collector thickness is less than or equal to 0.5%; and / or the coefficient of variation of the current collector areal density is less than or equal to 0.5%.

[0253] In some embodiments, the coefficient of variation of the current collector thickness can be selected as 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value range between the two.

[0254] The coefficient of variation of the current collector thickness can be tested using methods known in the art. As an example, cross-sections of the current collector are collected in different regions using argon ion polishing technology. For wound cells, the minimum distance between different regions on the unfolded current collector is 1 m; for stacked cells, samples are taken every five layers for testing. The thickness of the current collector cross-section in different regions is measured under an electron microscope, obtaining no fewer than 10 data points. The coefficient of variation of the current collector thickness is calculated using the following formula, where x... i The thickness of the current collector is represented by n, and the number of samples is represented by n. This represents the average thickness of the current collector.

[0255]

[0256] In some embodiments, the coefficient of variation of the current collector surface density can be selected as 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value range between the two.

[0257] Sampling and calculation were performed using the same method as described above for the coefficient of variation of thickness. The specific method for measuring the areal density of each sample is as follows: For example, the battery was placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature was maintained at 25°C, the battery was discharged at a constant current of 1 / 3C to 2.0V. The battery was then disassembled to obtain the electrode, the film layer on it was wiped off, and it was cut into small circular pieces with an area of ​​S0. The mass of these pieces was weighed and recorded as M0. The areal density of the current collector was M0 / S0.

[0258] When the coefficient of variation of the current collector thickness or areal density is within the above range, the non-uniformity of the current collector thickness or areal density can be reduced, the possibility of current collector fracture caused by stress concentration can be reduced, the fracture elongation of the current collector can be improved, the cumulative strain that the battery can withstand can be increased, and the cycle life of the battery can be improved.

[0259] In some embodiments, the range of nickel content in the current collector is less than 5%.

[0260] The range of nickel content in the current collector can be tested using any method known in the art. As an example, the battery is disassembled, the negative electrode is obtained, the film layer on the negative electrode is removed, and the current collector is obtained. At least 10 different regions are selected on the current collector. For wound cells, the minimum distance between different regions on the unfolded current collector is 1 meter; for stacked cells, samples are taken every five layers for testing, and an area of ​​at least 0.25 dm² is obtained in each region. 2 The mass content of nickel in the current collector samples was analyzed at different collection points using inductively coupled plasma spectrometry (ICP). The range of nickel mass content in the current collector was obtained by subtracting the minimum mass content from the maximum mass content.

[0261] In some embodiments, the range of nickel content in the current collector can be selected as 0, 1%, 2%, 3%, 4%, 4.5%, or any value between the two.

[0262] The range of nickel content in the current collector being within the above range means that the composition of different regions in the current collector is uniform and there is no obvious component segregation. This is beneficial to reducing the probability of local stress and strain concentration or accumulation, improving the consistency of current collector performance, and improving the cycle life of the battery cell.

[0263] In some embodiments, under test conditions of room temperature and a tensile speed of 50±0.5 mm / min, the tensile strength of the current collector is 700 MPa-2200 MPa, optionally 967 MPa-1900 MPa.

[0264] The tensile strength of the current collector at room temperature can be obtained by testing its tensile fracture curve. The specific test method can be found in GB / T5230-1995 "Electrolytic Copper Foil" standard. As an example, at least four current collector samples with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm should be cut. The samples should be continuously loaded at a tensile speed of 50±0.5 mm / min at room temperature until fracture. The tensile strength of the sample is calculated by dividing the tensile stress at fracture by the tensile cross-sectional area of ​​the current collector, expressed in MPa. At least four current collector samples should be tested, and the average value should be taken as the tensile strength of the current collector. It is understood that the current collector samples can be obtained from freshly prepared current collectors or from current collectors disassembled from batteries.

[0265] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the tensile strength of the current collector can be selected as 700 MPa, 800 MPa, 900 MPa, 950 MPa, 967 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa, 2000 MPa, 2100 MPa, 2200 MPa, or any value range between the two.

[0266] The aforementioned current collector has high tensile strength, which helps improve the cell's resistance to expansion and enhances the cycle life of individual battery cells.

[0267] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 1%-8%, optionally 2%-6%.

[0268] The elongation at break of the current collector at room temperature can be tested using the tensile strength test method described above.

[0269] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector can be selected as 1%, 1.5%, 2%, 3%, 4%, 4.5%, 5%, 6%, 6.5%, 7%, 8%, or any value range between the two.

[0270] The aforementioned current collector has a high elongation at break, indicating that the current collector has good deformation capacity, which helps to improve the cycle life of the battery cell.

[0271] In some embodiments, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

[0272] Silicon-based materials are beneficial for improving the energy density of individual battery cells. However, silicon-based materials exhibit significant lattice expansion during battery cell cycling, leading to a high expansion rate of the electrode sheets. This high expansion rate can easily cause cracks or even breakage in the current collector. The battery cells described in this application are particularly suitable for battery systems incorporating silicon-based materials, which are beneficial for achieving both high energy density and good cycle life.

[0273] In some implementations, the mass percentage of silicon is greater than or equal to 10% based on the total mass of the negative electrode film.

[0274] Based on the total mass of the negative electrode film, the mass content of silicon can be measured using any method known in the art. As an example, inductively coupled plasma optical emission spectrometry (ICP) is used to measure the elemental composition of the negative electrode film.

[0275] In some implementations, based on the total mass of the negative electrode film, the mass content of silicon can be selected as 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any value between the two.

[0276] The battery cells in this application embodiment are applicable to high-silicon systems, which helps to further improve the energy density per unit mass of the battery cells.

[0277] In some embodiments, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material is a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

[0278] In some embodiments, based on the total mass of the negative electrode film, the mass percentage of carbon-based material can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any value range between two of these. Carbon-based materials have a smaller specific capacity than silicon-based materials, but exhibit better cycle stability, enabling their application in energy storage batteries to achieve long cycle life. The wound battery cells containing carbon-based materials with thicknesses within the above-mentioned ranges provided in this application embodiment can further extend cycle life while maintaining a certain energy density.

[0279] In some embodiments, the battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

[0280] In some embodiments, the battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material is a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

[0281] In some embodiments, the electrode is a negative electrode, the film is a negative electrode film, and the negative electrode film includes a negative electrode active material. The negative electrode active material includes one or more of silicon-based materials and metal materials. The silicon-based material includes one or more of nano-silicon, silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, and silicon alloys. The metal material includes one or more of lithium, tin, and zinc.

[0282] Silicon-based materials are beneficial for improving the energy density of individual battery cells. However, silicon-based materials exhibit significant lattice expansion during battery cell cycling, leading to a high expansion rate of the electrode sheets. This high expansion rate can easily cause cracks or even breakage in the current collector. The battery cells described in this application are particularly suitable for battery systems incorporating silicon-based materials, which are beneficial for achieving both high energy density and good cycle life.

[0283] In some embodiments, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film is a negative electrode film, the negative electrode active material includes silicon-based materials, and the thickness of the wound cell is 10mm-25mm.

[0284] Silicon-based materials possess high specific capacity, and their inclusion enables thin-walled wound cells to achieve high energy density. However, silicon-based materials exhibit significant lattice expansion during cell cycling, leading to a high expansion rate of the electrode sheets. This high expansion rate increases the risk of cracks or even breakage in the current collector during cycling. The silicon-based wound cell with a thickness within the aforementioned range provided in this application combines high energy density with excellent cycle life.

[0285] In some embodiments, the battery cell includes one or more wound cells, the electrode is a negative electrode, the film is a negative electrode film, the negative electrode film includes a negative electrode active material, the negative electrode active material includes a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the thickness of the wound cell is 20mm-50mm.

[0286] Carbon-based materials have a smaller specific capacity compared to silicon-based materials, but they offer better cycle stability and can be used in energy storage batteries to achieve long cycle life. The carbon-based wound battery cells with thicknesses within the aforementioned range provided in this application can further extend cycle life while maintaining a certain energy density.

[0287] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0288] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: 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).

[0289] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0290] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0291] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoating layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0292] [Positive electrode plate]

[0293] 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. 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.

[0294] The positive electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0295] The positive electrode film typically comprises a positive electrode active material, an optional binder, and an optional conductive agent. The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this. As an example, the binder used for the positive electrode film may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. As an example, the conductive agent used for the positive electrode film includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0296] The positive electrode active material may be a positive electrode active material known in the art for use in battery cells.

[0297] When the battery cell of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium 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 their respective modified compounds. Examples of the lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, composite materials of lithium iron phosphate and carbon, lithium manganese phosphate, composite materials of lithium manganese phosphate and carbon, lithium manganese iron phosphate, composite materials of lithium manganese iron phosphate and carbon, and their respective modified compounds.

[0298] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material for the lithium-ion battery may include a lithium transition metal oxide having the general formula Li a Ni b Co c M d O e A f and one or more of its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0299] In some embodiments, by way of example, the positive electrode active material for the lithium-ion battery may include one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, 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 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0300] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0301] [Electrolytes]

[0302] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0303] The type of electrolyte salt is not specifically limited and can be selected according to actual needs.

[0304] When the battery cell of this application is a lithium-ion battery, as an example, the electrolyte salt may include one or more of 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).

[0305] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), 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), and diethyl sulfone (ESE).

[0306] In some embodiments, the electrolyte may optionally 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 the overcharge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature power performance of the battery cell.

[0307] [Isolation membrane]

[0308] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0309] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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.

[0310] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0311] In some embodiments, the battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0312] In some embodiments, the outer packaging may be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging may also be a flexible package, such as a pouch. The material of the flexible package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0313] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 6 The example shown is a square-structured battery cell 5.

[0314] In some embodiments, such as Figure 7 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0315] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0316] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0317] In some embodiments of this application, the battery cells according to this application can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0318] Figure 8 This is a schematic diagram of battery module 4 as an example. Figure 8 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0319] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0320] In some embodiments, 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.

[0321] Figure 9 and Figure 10 This is a schematic diagram of battery pack 1 as an example. Figure 9 and Figure 10 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0322] Electrical appliances

[0323] This application also provides an electrical device, which includes a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., 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.

[0324] The electrical device can be equipped with individual battery cells, battery modules, or battery packs according to its usage requirements.

[0325] Figure 11 This is a schematic diagram of an example electrical device. The 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.

[0326] 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.

[0327] Example

[0328] 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 mass, 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.

[0329] Example 1

[0330] (1) Preparation of current collector

[0331] First, a first metal foil layer is prepared in a foil-making machine. Then, a second metal foil layer is electroplated on both sides of the first metal foil layer. After anti-oxidation treatment and drying, the composite foil is obtained by winding.

[0332] The fabrication process of the first metal foil layer is as follows:

[0333] The electroplating temperature is 50℃~60℃, and the current density is 10A / dm². 2 The pH value is 2-4. The electroplating solution formulation for preparing the first metal foil layer includes:

[0334] The ingredients are FeSO4·7H2O, NiSO4·6H2O, sodium chloride, boric acid, and additives, including iron complexing agents, antioxidants, primary brighteners, secondary brighteners, stress relievers, and wetting agents.

[0335] The fabrication process of the second metal foil layer is as follows:

[0336] The electroplating temperature is 25℃ and the current density is 5A / dm². 2 The pH value is less than 1; the electroplating solution for preparing the second metal foil layer is a special plating solution for composite copper foil, which is commercially available.

[0337] The composite foil has a thickness of 6 μm. Based on the total mass of the current collector, the mass percentages of Ni are 56.2%, Fe is 9.8%, and Cu is 34%. The first metal foil layer contains 15% iron and 84% nickel, with the remainder being unavoidable impurities. The second metal foil layer is a copper foil with a purity of over 99%, and its average grain size is 47 nm. The thickness of the current collector and the concentration of the plating solution are monitored, controlling the coefficient of variation of the current collector surface density to be 0.4%, the coefficient of variation of the current collector thickness to be 0.2%, and the range of nickel mass content to be 2.4%.

[0338] (2) Battery manufacturing

[0339] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0340] A negative electrode slurry was prepared by dissolving silicon-carbon material (negative electrode active material), graphite, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) in deionized water at a weight ratio of 48:40:2:8:2. The slurry was then uniformly mixed and coated onto a prepared composite foil one or more times. After drying, a negative electrode film was obtained, which was then cold-pressed and slit to obtain the negative electrode sheet. The compacted density of the negative electrode sheet was 1.4 g / cm³. 3 The density of a single side surface is 88 mg / 1540.25 mm. 2 The tensile strength of the negative electrode sheet is 1.27 GPa.

[0341] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed uniformly at a mass ratio of 1:2:7. Then, 12.5 wt% of lithium LiPF6 salt was dissolved in the organic solvent. Next, 0.5 wt% of 1,3-propanesulfonate lactone and 0.5 wt% of succinic anhydride were added as additives to the above organic solvent, and the mixture was stirred until homogeneous to obtain the electrolyte.

[0342] Polypropylene film is used as the separator.

[0343] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting cells are then wound to form a wound battery cell. This wound cell is placed in a battery casing, dried, and then injected with electrolyte. Following formation and settling processes, a lithium-ion battery is produced. The wound cell has a thickness of 11.2 mm, a straight section length to corner section length ratio of 6.2, and a full discharge margin of 88%.

[0344] Example 2

[0345] The preparation method of Example 2 is basically the same as that of Example 1, except that the concentrations of NiSO4·6H2O and FeSO4·7H2O in the electroplating solution are changed so that the iron content in the first metal foil layer is 40%, the nickel content is 59%, and the remainder is unavoidable impurities.

[0346] Example 3

[0347] The preparation method of Example 3 is basically the same as that of Example 1, except that the electroplating solution formula of the first metal foil layer is adjusted to: NiSO4·6H2O, sodium chloride, boric acid and additives, so that the iron content in the first metal foil layer is 0%, the nickel content is 99%, and the rest are unavoidable impurities.

[0348] Example 4

[0349] The preparation method of Example 4 is basically the same as that of Example 1, except that a second metal foil layer is not deposited on the surface of the first metal foil layer.

[0350] Examples 5-6

[0351] The preparation methods of Examples 5-6 are basically the same as those of Example 1. The difference is that the current density and sample travel speed during the electroplating of the first and second metal foil layers are changed, which changes the thickness ratio of the first and second metal foil layers, as shown in Table 1.

[0352] Example 7

[0353] The preparation method of Example 7 is basically the same as that of Example 1, except that chromium salt is added to the plating solution used in the foil making machine, so that the iron content in the first metal foil layer is 14.5%, the chromium content is 0.5%, the nickel content is 84%, and the rest are unavoidable impurities.

[0354] Example 8

[0355] The preparation method of Example 10 is basically the same as that of Example 1, except that the temperature, current density and type of additives during electroplating are changed, which causes the grain size in the first metal foil layer to change, as shown in Table 1.

[0356] At the same time, the preparation process of the second metal foil layer was changed.

[0357] The plating solution for the second metal foil layer is a commercially available copper foil-specific plating solution, with an electroplating temperature of 55℃ and a current density of 70A / dm³. 2 The pH value is less than 1.

[0358] The average grain size of the second metal foil layer is 110 nm.

[0359] Example 9

[0360] The preparation method of Example 11 is basically the same as that of Example 1, except that the change in plating solution concentration is not monitored and adjusted, and the coefficient of variation of the surface density of the current collector is 1.8%.

[0361] Comparative Example 1

[0362] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the negative electrode current collector uses a common copper foil with a tensile strength of 358 MPa, which has an average grain size of 110 nm and a thickness of 6 μm.

[0363] Performance testing

[0364] 1. Average grain size of the first metal foil layer and the second metal foil layer

[0365] At room temperature, using CuKα rays as the X-ray source, a scanning speed of 2° / min was employed, with a scanning range of 10°–100°. X-ray diffraction patterns were measured using an X-ray diffractometer. The peak with the highest diffraction intensity in the X-ray diffraction pattern of the first metal foil layer was used as a reference. The average grain size was calculated using the Scherrer formula D = Kλ / (βcosθ), where D is the average grain size, K is the Scherrer constant (0.89), λ is the X-ray wavelength (0.154 nm was selected for the test), β is the full width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle.

[0366] The average grain size of the second metal foil layer can be obtained by referring to the average grain size test of the first metal foil layer.

[0367] 2. The percentage of grains with a size smaller than 80nm in the first metal foil layer

[0368] The grain size of the first metal foil layer in the current collector was characterized by transmission electron microscopy (TEM). Ten points were randomly selected in the scanning area, and ten grains were selected from each point for size measurement. A total of no less than 100 grains were identified. The proportion of grains with a grain size of less than 80 nm in the first metal foil layer was calculated by dividing the number of grains with a grain size of less than 80 nm by the total number of grains counted.

[0369] 3. Elastic deformation range of the electrode

[0370] Calculate the slope of the electrode's tensile stress-strain curve at each point, i.e., calculate the first derivative of the tensile stress with respect to the strain. Use this as the tangent modulus of the electrode at different strains. Plot the tangent modulus-strain curve of the sample with the tensile strain of the specimen as the horizontal axis (x-axis) and the first derivative of the tensile stress with respect to the strain as the vertical axis (y-axis, unit: GPa). Figure 1 and Figure 2 The curve plotted at the "-" point is shown. The elastic deformation range refers to the strain range corresponding to the decrease of the tangent modulus to 30 GPa. Figure 1 (b) For example, the strain A corresponding to the decrease of the tangent modulus to 30 GPa in the tangent modulus-strain curve is the elastic deformation range.

[0371] 4. The proportion of texture coefficients of (111) and (200) crystal planes

[0372] The X-ray diffraction pattern of the first metal foil layer was compared with the standard pattern. The phase and crystal plane corresponding to the diffraction peak of the first metal foil layer were analyzed. The texture coefficient M(111) of the crystal plane was calculated with reference to Equation I.

[0373] M(111)=I(111) / IR(111) (Equation I)

[0374] Where I(111) is the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum obtained by actual testing, and IR(111) is the standard intensity of the (111) crystal plane in the standard XRD spectrum of the main phase.

[0375] (111) The proportion of the texture coefficient P of the crystal plane is calculated by Equation II.

[0376] P(111)=M(111) / ∑M(hkl) (Equation II)

[0377] Where M(hkl) is the texture coefficient of each crystal plane of the main phase in the X-ray diffraction spectrum obtained by actual testing.

[0378] The proportion of texture coefficient of (200) crystal plane can be obtained by referring to the texture coefficient proportion test of (111).

[0379] 5. Tensile strength and elongation at break of the current collector at room temperature

[0380] At least four current collector specimens with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm were cut. The specimens were continuously loaded at a tensile speed of 50±0.5 mm / min at room temperature until fracture. The maximum tensile stress of the specimen during tensile fracture was taken as the tensile strength of the specimen, in MPa. The elongation at break was calculated by dividing the difference between the gauge length at fracture and the original gauge length by the original gauge length and then multiplying by 100%. The maximum tensile stress of the specimen was calculated by dividing the maximum load borne by the specimen during tensile fracture by the cross-sectional area of ​​the current collector. The cross-sectional area of ​​the current collector was calculated by multiplying the width by the thickness. The thickness of the current collector was measured using a micrometer, and the width of the current collector was the standard specimen width of 15 mm. At least four current collector specimens were tested, and the average value was taken as the tensile strength and elongation at break of the current collector. The tensile strength and elongation at break of the electrode at room temperature were obtained similarly.

[0381] 6. Bending resistance of the current collector

[0382] At room temperature, the current collector sample is folded 180° and then rolled back and forth at the fold with a 1.5kg roller. After unfolding, it is observed whether cracking and light transmission occur at the fold. The number of times the rolling action causes cracking and light transmission at the fold is recorded. At least ten samples are tested, and the average value is taken as the bending resistance of the current collector.

[0383] 7. Degree of wrinkling of the electrode sheet

[0384] At 25°C, the prepared battery was left to stand for 30 minutes, then discharged to 2.8V with a constant current of 1 / 3C. Afterwards, charge-discharge cycles were performed as follows: left to stand for 5 minutes, charged to 4.15V with a constant current of 1 / 2C, then charged at a constant voltage until the current dropped to 0.05C; left to stand for 5 minutes, then discharged to 2.8V with a constant current of 1 / 2C. One charge-discharge cycle was completed. After 50 cycles, the battery was disassembled at full charge (100% SOC). Five electrodes were randomly selected, and the presence of penetrating wrinkles was observed on the surface of each electrode. The number of penetrating wrinkles on each electrode was recorded, and the maximum value among the five electrodes was taken as the number of wrinkles, A, for the battery. The degree of wrinkling of the electrode is determined based on the value of A: when A = 0, that is, no through wrinkles appear in any of the 5 electrodes, the degree of wrinkling of the electrode is low; when 1 ≤ A ≤ 3, the degree of wrinkling of the electrode is medium; when A > 3, the degree of wrinkling of the electrode is high.

[0385] 8 Residual elongation at break of negative electrode current collector at 80% SOH

[0386] At 25°C, the prepared battery was left to stand for 30 minutes, then discharged to 2.8V with a constant current of 1 / 3C. The following charge-discharge cycles were then performed: after standing for 5 minutes, the battery was charged to 4.15V with a constant current of 1 / 2C, followed by constant voltage charging until the current dropped to 0.05C, and the charging capacity at this point was recorded as C0; after standing for 5 minutes, the battery was discharged to 2.8V with a constant current of 1 / 2C, and the discharge capacity at this point was recorded as C0'. This cycle was repeated until the discharge capacity reached 80% of C0', and the number of cycles was recorded. The battery was disassembled, the negative electrode film was removed, and the residual elongation at break of the negative electrode current collector was measured. A higher residual elongation at break indicates that the current collector has more room to stretch and withstand later cycles, meaning the expected time of cycle failure of the current collector is later, and the battery's cycle life is higher.

[0387] Test Results

[0388] Table 1

[0389]

[0390]

[0391] Table 2

[0392]

[0393]

[0394] As can be seen from the comparison between the examples and the comparative examples, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is less than or equal to 3%. The current collector includes at least one first metal foil layer, the average grain size of the first metal foil layer is 5nm-50nm, and the proportion of grains with a grain size of less than 80nm in the first metal foil layer is greater than or equal to 90%. This is beneficial for the current collector and the film layer to maintain synchronous changes during the battery cycle expansion process, reduce the degree of wrinkling of the electrode during long cycle process, and improve the cycle life of the battery.

[0395] As can be seen from the comparison between Example 3 and Examples 1 and 2, when the texture coefficient of the (200) crystal plane in the first metal foil layer is 25%-40%, the texture coefficient of the (200) crystal plane in the first metal foil layer within the above range means that the first metal foil layer may include new phases or coordinated deformation between multiple phases, which is beneficial to improve the plasticity of the current collector, reduce the irreversible deformation of the electrode during long cycle, improve the fracture elongation rate of the current collector when the battery reaches 80% SOH, and improve the cycle life of the battery cell.

[0396] As can be seen from the comparison between Example 1 and Examples 4-6, the absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is greater than 0 and less than or equal to 0.6%, indicating that the current collector can effectively withstand the reciprocating expansion of the battery cell during the cycle, reduce the irreversible deformation of the electrode during the long cycle, and further improve the wrinkling degree of the electrode during the long cycle.

[0397] As can be seen from the comparison of Examples 1 and 9, the coefficient of variation of the current collector surface density in Example 1 is 0.4%, while the coefficient of variation of the current collector surface density in Example 9 is 1.8%. Controlling the coefficient of variation of the current collector surface density to be less than or equal to 0.5% helps to improve the tensile strength and elongation at break of the current collector, reduce the irreversible deformation of the electrode during long cycles, and improve the cycle life of the battery cell.

[0398] 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, characterized in that, The battery cell includes an electrode, and the electrode includes a current collector and a film layer disposed on at least one side of the current collector. The absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is less than or equal to 3%. The current collector includes at least one first metal foil layer, the average grain size of the first metal foil layer is 5nm-50nm, and the proportion of grains with a grain size of less than 80nm in the first metal foil layer is greater than or equal to 90%.

2. The battery cell according to claim 1, characterized in that, The proportion of grains with a grain size of less than 30 nm in the first metal foil layer is greater than or equal to 90%.

3. The battery cell according to claim 1, characterized in that, The absolute value of the difference between the room temperature elongation at break of the current collector and the room temperature elongation at break of the electrode is greater than 0% and less than 1%, and can be selected as greater than 0 and less than or equal to 0.7%.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The battery cell satisfies one or more of the following conditions: (1) The elastic deformation range of the electrode is greater than or equal to 1%, wherein the elastic deformation range refers to the strain range corresponding to the reduction of the tangential modulus to 30 GPa; (2) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the tensile strength of the electrode is 650MPa-2250MPa; (3) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the elongation at break of the electrode is 1%-8%; (4) Under room temperature test conditions, the current collector has a bending resistance of 1 to 10 times; (5) The electrode is a negative electrode, and the film layer of the negative electrode includes a negative electrode active material, which includes at least one of carbon-based material or silicon-based material; (6) The battery cell includes one or more wound cells, the thickness of which is 10mm-50mm; (7) The battery cell includes one or more wound cells, the wound cells include corner areas and straight areas, and the ratio of the length of the straight area to the length of the corner area of ​​the wound cells is 1-10. (8) the single-sided face density of the pole piece is 20 mg / 1540.25 mm 2 - 200 mg / 1540.25 mm 2 ; (9) the compaction density of the pole piece is 0.9 g / cm 3 -1.8 g / cm 3 ; (10) The thickness of the film layer on one side of the electrode is 20μm-150μm; (11) The full discharge margin of the battery cell is 70%-105%.

5. The battery cell according to any one of claims 1 to 3, characterized in that, The battery cell satisfies one or more of the following conditions: (1) The elastic deformation range of the electrode is greater than 1% and less than or equal to 2%, wherein the elastic deformation range refers to the strain range corresponding to the reduction of the tangential modulus to 30 GPa; (2) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the tensile strength of the electrode is 917MPa-1950MPa; (3) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the elongation at break of the electrode is 2%-6%; (4) the monolateral surface density of the pole piece is 50 mg / 1540.25 mm 2 - 200 mg / 1540.25 mm 2 ; (5) the compaction density of the pole piece is 1.3 g / cm 3 -1.8 g / cm 3 ; (6) The thickness of the single-sided film layer of the electrode is 40μm-80μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The battery cell satisfies one or more of the following conditions: (1) The average grain size of the first metal foil layer is 8nm-16nm; (2) The first metal foil layer includes a first element, which includes one or more of W, Mo, Cr, Ag, Au, Pt, Zr, Nb, Mn, Co, Ni, Fe, and Cu; (3) Based on the total thickness of the current collector, the total thickness of the first metal foil layer accounts for 30%-100%; (4) The first metal foil layer includes a face-centered cubic structure, and the texture coefficient of the (111) crystal plane in the first metal foil layer accounts for 30%-80%; (5) The texture coefficient of the (200) crystal plane in the first metal foil layer accounts for 10%-50%; (6) The first metal foil layer includes an iron-nickel-based alloy, and the mass content of iron in the first metal foil layer is less than 65%. (7) The first metal foil layer includes an iron-nickel-based alloy, wherein the mass content of iron in the first metal foil layer is 10%-60% and the mass content of nickel in the first metal foil layer is 40%-90%. (8) one or more of Ni, NiFe3, FeNi3, Fe3Ni2, Ni 0.64 Fe 0.36 , Ni1Fe1 phases.

7. The battery cell according to any one of claims 1 to 5, characterized in that, The battery cell satisfies one or more of the following conditions: (1) Based on the total thickness of the current collector, the total thickness of the first metal foil layer accounts for 30%-85%; (2) The first metal foil layer includes a face-centered cubic structure, and the texture coefficient of the (111) crystal plane in the first metal foil layer accounts for 30%-80%; (3) The texture coefficient of the (200) crystal plane in the first metal foil layer accounts for 25%-40%.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The current collector further includes at least one second metal foil layer, and the battery cell satisfies one or more of the following conditions: (1) The second metal foil layer includes a second element, which includes one or more of Cu, Ag, and Au, and the mass content of the second element in the second metal foil layer is greater than or equal to 90%. (2) The average grain size of the second metal foil layer is greater than or equal to 40 nm; (3) The second metal foil layer includes copper, the mass content of Cu in the second metal foil layer is greater than or equal to 90%, and the average grain size of the second metal foil layer is 40nm-150nm. (4) Based on the total thickness of the current collector, the total thickness of the second metal foil layer accounts for 15%-70%.

9. The battery cell according to claim 8, characterized in that, The average grain size of the second metal foil layer is 40nm-100nm.

10. The battery cell according to claim 8 or 9, characterized in that, Based on the total mass of the current collector, the mass percentage of Ni is 25%-70%, the mass percentage of Fe is 1%-40%, and the mass percentage of Cu is 15%-65%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The battery cell satisfies one or more of the following conditions: (1) The coefficient of variation of the thickness of the current collector is less than or equal to 0.5%; (2) The coefficient of variation of the surface density of the current collector is less than or equal to 0.5%; (3) The range of nickel content in the current collector is less than 5%; (4) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the tensile strength of the current collector is 700MPa-2200MPa; (5) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the elongation at break of the current collector is 1%-8%.

12. The battery cell according to any one of claims 1 to 10, characterized in that, The battery cell satisfies one or more of the following conditions: (1) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the tensile strength of the current collector is 967MPa-1900MPa; (2) Under test conditions of room temperature and tensile speed of 50±0.5mm / min, the elongation at break of the current collector is 2%-6%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

14. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes one or more wound cells, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

15. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and the mass content of silicon element is greater than or equal to 10% based on the total mass of the negative electrode film layer.

16. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes a stacked cell, the electrode is a negative electrode, the film layer of the negative electrode includes a negative electrode active material, the negative electrode active material is a carbon-based material, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene, and the mass content of carbon element is greater than or equal to 90% based on the total mass of the negative electrode film layer.

17. A battery device, characterized in that, The battery device includes any one of the battery cells according to claims 1 to 16, and the battery device is at least one of a battery module, a battery pack, and an energy storage battery.

18. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1 to 16 or the battery device according to claim 17.

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