Pole piece, electrode assembly, battery cell and preparation method therefor, battery, electric device

Abstract

A kind of pole piece, electrode assembly, battery cell and preparation method thereof, battery, electric device belong to battery technical field.The at least end surface of pole piece is provided with protective layer, and the protective layer includes silicon oxide, and the shear strength G of protective layer satisfies: G≥110MPa.The technical scheme of the present application is beneficial to improve the reliability of battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode sheet, electrode assembly, battery cell and its preparation method, battery, and electrical device. Background Technology

[0002] In the new energy industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, and reliability. The design of the electrodes in a battery cell is crucial to the cell's reliability and cycle performance. Therefore, how to provide an electrode that improves the reliability of a battery cell is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrode to improve the reliability of a single battery cell.

[0005] To achieve the above objectives, this application provides an electrode sheet, an electrode assembly, a battery cell and its preparation method, a battery, and an electrical device.

[0006] In a first aspect, an electrode is provided, wherein at least one end surface of the electrode is provided with a protective layer comprising silicon oxide, and the shear strength G of the protective layer satisfies: G≥110MPa.

[0007] In this embodiment, the protective layer reduces the risk of short circuits caused by the contact between the end surface of the electrode and an electrode of opposite polarity, thus improving the reliability of the battery cell. The shear strength G of the protective layer is ≥110 MPa, ensuring that the protective layer is less likely to detach during long-term use of the battery cell, further enhancing its reliability.

[0008] In one possible implementation, the shear strength G of the protective layer satisfies: 110 MPa ≤ G ≤ 1300 MPa. This ensures a strong bond between the protective layer and the electrode assembly, reducing the risk of the protective layer detaching from the electrode assembly, and also helps to reduce the time and temperature required to prepare the protective layer. Optionally, 300 MPa ≤ G ≤ 1000 MPa. This provides both a suitable bond strength between the protective layer and the electrode assembly, and further reduces the time and temperature required to prepare a protective layer with higher shear strength.

[0009] In one possible implementation, the thickness d1 of the protective layer satisfies: 20nm ≤ d1 ≤ 200nm. This allows the protective layer to possess sufficient shear strength while mitigating other adverse effects caused by excessive thickness.

[0010] In one possible implementation, the thickness d1 of the protective layer satisfies: 100nm ≤ d1 ≤ 170nm. When d1 is greater than or equal to 100nm, the protective layer has a suitable thickness, which can effectively reduce the risk of short circuits; when d1 is less than or equal to 170nm, the protective layer thickness is small, which can reduce the adverse effects of excessive protective layer thickness on the performance of the battery cells.

[0011] In one possible implementation, based on the total mass of all elements at a first position on the electrode, the mass content A of Si element satisfies: A ≤ 2 wt%, where the first position is 5 mm from the end surface. This results in a lower Si element content at a position 5 mm from the end surface, thereby reducing the adverse effects of Si element on the cycle performance of the battery cell. Optionally, A < 0.01 wt%. This results in a very small or even negligible Si element content, further reducing its impact on the cycle performance of the battery cell.

[0012] In one possible implementation, the electrode includes a main body and a tab, the tab protruding from the main body in a first direction, and the protective layer is disposed on at least a portion of the end surface of the main body in the first direction and at at least a portion of the tab. This reduces the risk of short circuits caused by the end surface and tab colliding with electrodes of opposite polarity.

[0013] In one possible implementation, the protective layer is provided on the end surface of the main body along a second direction, which is perpendicular to the first direction and parallel to the surface where the electrode is located. In this way, having a protective layer on both the end surfaces of the main body along the first and second directions further reduces the risk of short circuits caused by the electrode overlapping with an electrode of opposite polarity.

[0014] In one possible implementation, the electrode is a positive electrode, which includes a positive active material comprising a layered transition metal oxide.

[0015] In the above technical solution, the battery prepared using the above positive electrode active material has a higher energy density, so the battery can balance high energy density and high reliability.

[0016] In one possible implementation, the layered transition metal oxide includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.6 Co 0.2 Mn 0.2 At least one of O2. The above-mentioned positive electrode active materials have high nickel content and high specific capacity, which is beneficial for preparing batteries with high energy density.

[0017] In a second aspect, an electrode assembly is provided, including the electrode in the first aspect and any possible implementation thereof.

[0018] Thirdly, a battery cell is provided, comprising: the electrode assembly described in the second aspect; and a housing for accommodating the electrode assembly. During long-term use, the protective layer of this battery cell is less prone to peeling off, which helps to further improve the reliability of the battery cell.

[0019] Fourthly, a method for preparing a battery cell is provided, comprising: placing an electrode assembly in a container; introducing gaseous silane and water vapor into the container to obtain an electrode assembly with a protective layer, the protective layer comprising silicon oxide, and the silane having the general formula: R'-Si(OR). n Wherein, R' includes organic or inorganic functional groups, R includes alkyl groups, n is an integer and 2≤n≤4; the electrode assembly with the protective layer is removed from the container and placed into the housing to obtain the battery cell.

[0020] In this embodiment, gaseous silane and water vapor react on the exposed metal surface of the electrode assembly, thereby forming a protective layer on the exposed metal surface of the electrode assembly. This protective layer includes silicon oxide. This reduces the risk of short circuits caused by the exposed metal of the electrode assembly contacting electrodes of opposite polarity, thus improving the reliability of the battery cell. The electrode assembly with the protective layer is then removed from the container and placed into the housing, facilitating the assembly of the battery cell. Furthermore, since the housing is not placed inside the container, no protective layer is formed inside the housing, thereby reducing the adverse effects of the protective layer on the battery cell. Therefore, the battery cell obtained by this technical solution has better overall performance.

[0021] In one possible implementation, placing the electrode assembly in the container includes: connecting the electrode assembly to the end cap assembly, and placing the electrode assembly connected to the end cap assembly into the container. This allows for the processing of the electrode assembly and end cap assembly as a single unit, which facilitates the fabrication of a protective layer at the connection point between the electrode assembly and the end cap assembly.

[0022] In one possible implementation, the silane has a boiling point of less than or equal to 200°C. This facilitates the reaction of the silane and water molecules at a lower temperature within the container.

[0023] In one possible implementation, the silane comprises at least one of (H5C2O)3Si-CH2CH2-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-S4-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-CO-NH2, CH2OCHCH2-O-(CH2)3-Si(OCH3)3, or CH3-Si(OCH3)3. The use of the above-mentioned substances facilitates hydrolysis; and the silanes have suitable boiling points, facilitating the yield of gaseous silanes.

[0024] In one possible implementation, the temperature T inside the container satisfies: 60℃≤T≤150℃; alternatively, 80℃≤T≤100℃. In the above technical solution, by reasonably setting the temperature T, the reaction of gaseous silane and water vapor on the metal surface is facilitated, while the adverse effects of excessively high temperatures on the diaphragm in the electrode assembly are reduced.

[0025] In one possible implementation, the reaction time t1 between the gaseous silane and the water vapor satisfies: 4h ≤ t1 ≤ 12h. This allows for the formation of a protective layer in a shorter time, reducing the risk of a protective layer forming on the active material layer of the electrode assembly due to excessively long reaction times.

[0026] In one possible implementation, the inflow rate Q of the gaseous silane and / or the water vapor satisfies: 0.1 L / min ≤ Q ≤ 2 L / min. This allows the gaseous silane and water vapor to enter the container at a suitable rate, facilitating their reaction on the metal surface and promoting the formation of a protective layer. It also helps reduce the risk of silane seeping into exposed metal areas of the electrode assembly.

[0027] In one possible implementation, the pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows the protective layer to be generated at atmospheric pressure, reducing the complexity of the fabrication process; it also helps to reduce the risk of silane infiltrating the active material layer in the electrode assembly.

[0028] In one possible implementation, placing the electrode assembly in the container includes: placing multiple electrode assemblies in a support, the support covering the largest surface area of ​​the electrode assembly; and placing the support in the container. This allows multiple electrode assemblies to be processed within the container, improving production efficiency. Furthermore, the support covering the largest surface area of ​​the electrode assembly helps reduce the risk of silanes or similar substances entering the electrode assembly.

[0029] In one possible implementation, the preparation method further includes performing a plasma surface treatment on the electrode assembly before placing it in the container. This improves the surface activity of the exposed metal in the electrode assembly, facilitating the deposition and reaction of silane on the metal surface and aiding in the preparation of the protective layer.

[0030] In one possible implementation, the power S of the plasma surface treatment satisfies: 100W ≤ S ≤ 200W; and / or, the time t2 of the plasma surface treatment satisfies: 50s ≤ t2 ≤ 100s; and / or, the gas flow rate V1 introduced during the plasma surface treatment satisfies: 0.2L / min ≤ V1 ≤ 0.4L / min. By selecting treatment parameters within the above ranges, a better plasma treatment effect can be achieved on the electrode assembly.

[0031] In one possible implementation, the preparation method further includes: purging the container with an inert gas before introducing the gaseous silane and water vapor into the container to purge the air inside. This reduces the adverse effects of air on the reaction between the silane and water vapor.

[0032] In one possible implementation, the container is connected to the external environment. This allows for the maintenance of a relatively constant pressure inside the container.

[0033] Fifthly, a battery is provided, comprising a battery cell according to the third aspect, and / or a battery cell obtained according to the preparation method of the fourth aspect and any possible implementation thereof.

[0034] In a sixth aspect, an electrical device is provided, comprising the battery described in the fifth aspect. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced 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.

[0036] Figure 1 A schematic diagram of the structure of an electrode sheet before cutting the electrode tab according to an embodiment of this application;

[0037] Figure 2 This is a schematic diagram of the structure of an electrode sheet after the tabs have been cut according to an embodiment of this application;

[0038] Figure 3 for Figure 2 Cross-sectional view along the AA direction;

[0039] Figure 4 for Figure 2 Cross-sectional view along the BB direction;

[0040] Figure 5 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0041] Figure 6 This is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application;

[0042] Figure 7 This is a schematic diagram of an electrode assembly connected to an end cap assembly according to an embodiment of this application;

[0043] Figure 8 A schematic diagram of a support frame with electrode assemblies;

[0044] Figure 9 A schematic diagram of silane and water vapor deposition according to an embodiment of this application;

[0045] Figure 10 This is a schematic diagram of a battery according to an embodiment of this application;

[0046] Figure 11 This is a schematic diagram of an electrical device according to an embodiment of this application. Detailed Implementation

[0047] The embodiments of the electrodes, electrode assemblies, battery cells, their preparation methods, batteries, and electrical devices described herein are disclosed in detail with appropriate reference to the accompanying drawings. 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0048] 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.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] 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.

[0052] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, and reliability. After cutting, the exposed metal of the electrodes in a battery cell poses a risk of short circuits due to contact with electrodes of opposite polarity or other components of the cell. Some methods incorporate protective layers at the exposed metal locations of the electrode assemblies to reduce the risk of short circuits and improve the reliability of the battery cell. However, the bonding strength between the protective layer and the electrode assembly is often weak, and it is prone to detachment over prolonged use, offering limited improvement to the overall reliability of the battery cell.

[0053] In view of this, this application provides an electrode sheet, wherein at least the end surface of the electrode sheet is provided with a protective layer, the protective layer comprising silicon oxide, and the shear strength G of the protective layer satisfies: G≥110MPa. The protective layer has a large shear strength, making it less likely to detach from the electrode sheet, which is beneficial to improving the reliability of the battery cell.

[0054] [Extreme Film]

[0055] Figure 1 This is a schematic diagram of the structure of an electrode sheet before the tabs are cut, according to an embodiment of this application. Figure 2 This is a schematic diagram of the structure of an electrode sheet after the tabs have been cut according to an embodiment of this application. Figure 3 for Figure 2 Cross-sectional view along the AA direction. Figure 4 for Figure 2 Cross-sectional view along the BB direction.

[0056] In one embodiment of this application, for example, in combination with Figures 1 to 4 As shown, at least the end surface of the electrode 1 is provided with a protective layer 35, the protective layer 35 includes silicon oxide, and the shear strength G of the protective layer 35 satisfies: G≥110MPa.

[0057] The end surface of the electrode 1 may include either an opposing end surface along a first direction of the electrode 1 (e.g., the y direction in the figure) or an opposing end surface along a second direction (e.g., the x direction in the figure).

[0058] The surfaces of the two opposite ends along the first direction of the electrode 1 may include a first end surface 3301a and a second end surface 3301b.

[0059] The surfaces of the two opposite ends along the second direction of the electrode 1 may include a third end surface 3302a and a fourth end surface 3302b.

[0060] The end surface of electrode 1 can be a surface formed by cutting, after which the metal of the end surface is exposed. For example, combined with Figures 1 to 3As shown, the end surface of the main body 330 along the first direction may include a first end surface 3301a and a second end surface 3301b. The first end surface 3301a may be a surface formed during the process of cutting the electrode sheet along the cutting line 124 to prepare the electrode tab 331, and the second end surface 3301b may be a surface generated during the process of slitting the electrode sheet 1. Slitting can refer to the process of cutting a large electrode sheet into multiple small electrode sheets 1 by cutting.

[0061] As an example, a protective layer 35 is provided on both the end surface along the first direction and the end surface along the second direction.

[0062] As another example, such as Figures 1 to 4 As shown, a protective layer 35 is provided on the end surface of the electrode 1 in the first direction, and no protective layer 35 is provided on the end surface of the electrode 1 in the second direction.

[0063] As another example, the end surface (first end surface 3301a) of the electrode 1 near the tab along the first direction is provided with a protective layer 35, while the end surface (second end surface 3301b) away from the tab is not provided with a protective layer 35; and the end surface along the second direction of the electrode 1 is not provided with a protective layer 35.

[0064] The protective layer 35 includes silicon oxide, which may have the following structure: -Si-O-Si-. Silicon oxide is not easily swollen during electrolyte immersion and is not easily detached during long-term use of the battery cell 3.

[0065] The protective layer 35 has certain insulation properties, which can reduce the risk of short circuit caused by the overlap of electrodes with opposite polarity on the end surface, and help improve the reliability of the battery cell.

[0066] The shear strength G of the protective layer 35 satisfies: G≥110MPa. In this way, the protective layer 35 is not easy to detach from the electrode 1, and it is also not easy to detach from the electrode 1 after long-term immersion in electrolyte, which helps to further improve the reliability of the battery cell.

[0067] In this embodiment, at least the end surface of the electrode 1 is provided with a protective layer 35, which includes silicon oxide. The shear strength G of the protective layer 35 satisfies: G≥110MPa. The provision of the protective layer 35 can reduce the short-circuit risk of the battery cell, and the protective layer 35 is not easy to fall off, which is beneficial to improving the reliability of the battery cell 3.

[0068] In some embodiments, the shear strength G of the protective layer 35 satisfies: 110MPa≤G≤1300MPa. G can be 110MPa, 200MPa, 500MPa, 1000MPa, 1300MPa, or any value within the above range.

[0069] The shear strength of the protective layer 35 is related to the thickness of the protective layer 35. In the embodiments of this application, the greater the thickness of the protective layer 35, the greater the shear strength of the protective layer 35.

[0070] The shear strength of the protective layer 35 reflects the bonding strength between the protective layer 35 and the electrode 1. The greater the shear strength of the protective layer 35, the stronger the bond between it and the electrode 1, and the lower the risk of the protective layer 35 detaching from the electrode 1. Furthermore, during the long-term use of the battery cell 3, the risk of the protective layer 35 swelling due to electrolyte immersion is lower, and the protective layer 35 is less prone to detachment, which helps improve the reliability of the battery cell 3.

[0071] The test method for the shear strength of the protective layer 35 can be found in the test method section below.

[0072] When the shear strength of the protective layer 35 is greater than or equal to 110 MPa, the risk of the protective layer 35 falling off the electrode 1 is low; when the shear strength of the protective layer 35 is less than or equal to 1300 MPa, it is easier to prepare the protective layer 35, which helps to reduce the time required to prepare the protective layer 35 and the temperature required to prepare the protective layer 35.

[0073] In some embodiments, 300MPa≤G≤1000MPa. G can be 300MPa, 400MPa, 500MPa, 800MPa, 1000MPa or any value within the above range.

[0074] In this embodiment, 300MPa≤G≤1000MPa, the protective layer 35 and the electrode 1 have a suitable bonding strength, which is also conducive to further reducing the time and temperature required to prepare the protective layer 35 with higher shear strength.

[0075] In some embodiments, the thickness d1 of the protective layer 35 satisfies: 20nm ≤ d1 ≤ 200nm.

[0076] The thickness d1 of the protective layer 35 can be 190nm, 160nm, 100nm, 50nm, 20nm, or any value within the above range. The thickness d1 of the protective layer 35 can be the average thickness of the protective layer 35. For example, measurements can be taken at multiple locations on the end surface, and the average of the multiple data points can be taken as the thickness at the end surface.

[0077] At different locations, such as at the first end surface 3301a and the second end surface 3301b, the protective layer 35 has the same or substantially the same thickness.

[0078] When d1 is greater than or equal to 20nm, the protective layer 35 has a suitable thickness, which can effectively reduce the risk of short circuit. Furthermore, the protective layer 35 has a certain shear strength, so the risk of detachment is low. When d1 is less than or equal to 200nm, the adverse effects of excessive thickness of the protective layer 35 on the performance of the battery cell 3 can be reduced.

[0079] In some embodiments, the thickness d1 of the protective layer 35 satisfies: 100nm ≤ d1 ≤ 170nm. d1 can be 100nm, 120nm, 160nm, 170nm, or any value within the above range.

[0080] When d1 is greater than or equal to 100nm, the protective layer 35 has a suitable thickness, which can effectively reduce the risk of short circuit; when d1 is less than or equal to 170nm, the protective layer 35 has a smaller thickness, which can reduce the adverse effects of excessive thickness of the protective layer 35 on the performance of the battery cell 3.

[0081] In some embodiments, based on the total mass of all elements at the first position of electrode 1, the mass content A of Si element satisfies: A≤2wt%, and the first position is a position 5mm away from the end surface.

[0082] The first position can be a position 5mm away from the end surface in any direction in electrode 1.

[0083] As an example, the first position is a position 5 mm away from the second end surface 3301b along the first direction (y direction in the figure).

[0084] As another example, the first position is a position 5 mm away from the third end surface 3302a along the second direction (x direction in the figure).

[0085] At the first position of the electrode, multiple elements constituting the material of electrode 1 are included. For example, for the positive electrode, the first position of the positive electrode includes elements constituting the positive current collector, such as Al; elements constituting the positive electrode film layer; and Si elements that may penetrate into the positive electrode film layer. For the negative electrode, the first position of the negative electrode includes elements constituting the negative current collector, such as Cu; elements constituting the negative electrode film layer; and Si elements that may penetrate into the negative electrode film layer.

[0086] During the preparation of protective layer 35, the raw materials for preparing protective layer 35, such as silane and water, are deposited on electrode 1 and react. The mass content of Si element can reflect the degree of silane penetration or adhesion to electrode 1, or it can reflect the content of silicon oxide on electrode 1.

[0087] Silicon oxide or silicon affects the conductivity of the electrodes, thus affecting the electrical performance of the individual battery cells. For example, it affects the capacity retention, power, and resistance of the battery cells.

[0088] When the mass content of Si element at the first position is less than or equal to 2 wt%, the content of silicon oxide is low or the infiltration of silane is minimal. This reduces the risk of silicon oxide or silane being present in the area outside the end surface 3301 of the electrode assembly 33, thus minimizing the impact on the performance of the battery cell and helping to reduce the impact on the cycle performance of the battery cell.

[0089] In some embodiments, A < 0.01 wt%. This results in a lower Si content at the first position of the electrode, thereby reducing the adverse effects of silicon oxide containing Si on the cycle performance of the battery cell.

[0090] In this embodiment, the Si content at the first location of the electrode is low, and the shear strength of the protective layer 35 in the battery cell is high. This results in a battery cell with high capacity and high long-term reliability, significantly reducing the risk of the protective layer 35 detaching during prolonged use. This battery cell is suitable for long-term use scenarios, such as energy storage.

[0091] In some embodiments, the metal on the end surface is bonded to the silicon oxide in the protective layer 35 by chemical bonds. Specifically, the metal and silicon oxide are bonded by covalent bonds.

[0092] As an example, the combination of metal and silicon oxide is represented by the following: Me-Si-O-Si, where Me represents the metal.

[0093] As one example, Me represents aluminum. As another example, Me represents copper.

[0094] The shear strength of the protective layer 35 is related to the connection method between the protective layer 35 and the exposed metal of the electrode 1. Furthermore, performing plasma surface treatment on the electrode 1 before preparing the protective layer 35 is beneficial for further enhancing the shear strength of the protective layer 35.

[0095] In this embodiment, the protective layer 35 has a strong bond with the end surface 3301, and the protective layer 35 is not easy to fall off.

[0096] In some embodiments, the electrode 1 includes a main body portion 330 and an electrode tab 331. The electrode tab 331 protrudes from the main body portion 330 along a first direction, and a protective layer 35 is provided on the end surface of the main body portion 330 along the first direction and at least a portion of the electrode tab 331.

[0097] The first direction is the direction in which the tab 331 protrudes from the main body 330, for example, as Figure 2 As shown, the first direction is the y-direction.

[0098] A protective layer 35 is provided at least partially on the tab 331. It is understood that the protective layer 35 may be provided at partial or complete locations of the tab 331. "At least partially on the tab 331" may refer to the location of the exposed metal of the tab 331.

[0099] As an example, such as Figure 2 As shown, the tab 331 may include a first part 3311 and a second part 3312, the first part 3311 is connected to the second part 3312 and the first part 3311 is closer to the main body 330 relative to the second part 3312; the main body 330 includes a first region 3302 and a second region 3303 connected, the second region 3303 is closer to the tab 331 relative to the first region 3302; the first part 3311 of the tab 331 and the second region 3303 of the main body 330 are coated with an insulating material, the second part 3312 of the tab 331 is an exposed aluminum foil, and the first region 3302 of the main body 330 is coated with an active material; the first part 3311 is not provided with a protective layer 35, and the second part 3312 is provided with a protective layer 35.

[0100] As another example, the entire area of ​​the main body 330 is coated with an active material, the entire area of ​​the tab 331 is bare aluminum foil, and the entire area of ​​the tab 331 is provided with a protective layer 35.

[0101] In some embodiments, the exposed metal in the tab 331 is bonded to the silicon oxide in the protective layer 35 by chemical bonds. This reduces the risk of a short circuit caused by the tab 331 colliding with an electrode of opposite polarity.

[0102] In some embodiments, a protective layer 35 is provided on the end surface of the main body 330 along a second direction, the second direction being perpendicular to the first direction and parallel to the surface where the electrode 1 is located. For example, the second direction is... Figure 1 The x-direction in the middle.

[0103] In this embodiment, a protective layer 35 is provided on the end surface of the main body 330 along the second direction and the end surface along the first direction, which helps to further reduce the risk of short circuit caused by the electrode 1 overlapping with an electrode of opposite polarity.

[0104] In some embodiments, the electrode is a positive electrode, which includes a positive active material comprising a layered transition metal oxide. Batteries prepared using the aforementioned positive active material exhibit higher energy density, thus achieving a balance between high energy density and high reliability.

[0105] Layered transition metal oxides can include ternary materials, lithium cobalt oxide, lithium-rich manganese-based materials, etc.

[0106] As an example, the chemical formula of layered transition metal oxides includes: Li x (Ni a Co b Mn c ) 1-d M d O 2-y N y M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La; N includes at least one of F, S, and P; 0.6 ≤ a < 1; 0 <b<0.4,0<c<0.4,a+b+c=1,0≤d<1,0.2≤x≤1.2,0≤y<2。

[0107] a can be 0.6, 0.7, 0.8, 0.9 or any value within the above range; b can be 0.1, 0.2, 0.3 or any value within the above range; c can be 0.1, 0.2, 0.3 or any value within the above range; d can be 0, 0.1, 0.6, 0.6, 0.8 or any value within the above range; x can be 0.2, 0.5, 1, 1.2 or any value within the above range; and y can be 0, 0.5, 1, 1.5, 2 or any value within the above range.

[0108] When d is greater than 0, the layered transition metal oxide includes the M element, which can result in higher stability; when d is 0, the layered transition metal oxide does not include the M element.

[0109] It is understandable that the position of the M ion in the layered transition metal oxide structure can be the replacement of some of the transition metal sites. For example, in the case of a nickel-cobalt-manganese-based ternary material, the M ion can replace some of the manganese, nickel, or cobalt sites.

[0110] When y = 0, layered transition metal oxides do not contain nitrogen (N). It is understandable that the position of N ions in the layered transition metal oxide structure could be the position where some O ions have been replaced.

[0111] During the charging and discharging process, Li will be extracted and consumed. The molar content of Li will be different when the battery is discharged to different states. The above limitation on x includes the molar content of Li in different charging and discharging states of the battery (usually the battery voltage is between 2-5V).

[0112] In the above technical solution, the positive electrode active material that meets the above chemical formula has a high nickel content, a high specific capacity, and the battery has a high energy density and high reliability.

[0113] In some embodiments, layered transition metal oxides include LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.6 Co 0.2 Mn 0.2 At least one of O2. The above-mentioned positive electrode active materials have high specific capacity, which is beneficial for preparing batteries with high energy density.

[0114] Electrode 1 can be either a positive electrode or a negative electrode. As an example, both the positive and negative electrode have the structure described in electrode 1.

[0115] [Positive electrode plate]

[0116] The positive electrode includes a positive current collector and a positive electrode film layer disposed on the positive current collector.

[0117] The positive electrode current collector can be a metal foil or a composite current collector. For example, the positive electrode current collector can be an aluminum foil.

[0118] Composite current collectors may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] The positive electrode film includes a positive electrode active material. This positive electrode active material can be any known battery-grade positive electrode active material. For example, it could be lithium iron phosphate, ternary materials, or lithium-rich manganese-based materials.

[0120] The positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0121] The positive electrode film may optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] [Negative electrode plate]

[0123] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0124] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. Composite current collectors can be formed by depositing metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0126] The negative electrode film may optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] [Electrolytes]

[0128] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0129] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0130] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0131] Solvents may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0132] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0133] [Isolation Component]

[0134] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0135] The material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0136] [Electrode Assembly]

[0137] This application provides an electrode assembly, which includes the electrode 1 in any of the above embodiments.

[0138] The positive electrode, negative electrode, and separator can be manufactured into an electrode assembly by a winding process or a stacking process, wherein the positive electrode and negative electrode can have the structure described in electrode 1.

[0139] [Battery cell]

[0140] Figure 4 This is a schematic diagram of the structure of a battery cell according to an embodiment of this application. For example, as shown... Figure 4 As shown, the battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33.

[0141] The housing 31 is used to house the electrode assembly 33, and the shape of the housing 31 can be set according to the shape of the electrode assembly 33. The housing 31 can accommodate one or more electrode assemblies. For example, Figure 4 As shown, the housing 31 contains four electrode assemblies 33. The housing 31 can be made of metal, such as copper or aluminum.

[0142] End cap assembly 32 is used to cover housing 31 to seal electrode assembly 33. End cap assembly 32 is connected to electrode assembly 33, wherein end cap assembly 32 can be directly connected to electrode assembly 33 or indirectly connected to electrode assembly 33.

[0143] As an example, such as Figure 4 As shown, the electrode assembly 33 is made by winding a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0144] The end cap assembly 32 is connected to the electrode assembly 33. As an example, the end cap assembly 32 is welded to the tab 33a of the electrode assembly 33 via a current collector 34. The tab 33a in the electrode assembly 33 can be formed by stacking multiple tabs 331 of the electrode plates 1, and the current collector 34 can be made of metal, such as copper or aluminum.

[0145] End cap assembly 32 includes electrode terminals 322, for example, such as Figure 4 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal. A current collector 34 is used to connect the positive electrode tab and the positive electrode terminal, and another current collector 34 is used to connect the negative electrode tab and the negative electrode terminal.

[0146] In some embodiments, the battery cell 3 can be cylindrical, square, or any other arbitrary shape. The battery cell 3 can be a lithium-ion battery, lithium-sulfur battery, sodium-ion battery, magnesium-ion battery, etc. The battery cell 3 can serve as the smallest structural unit of a battery.

[0147] In some embodiments, the battery cells 3 can be assembled into a battery module, and the number of battery cells 3 contained in the battery module can be one or more, the specific number of which can be selected according to the application and capacity of the battery module.

[0148] The above combination Figures 1 to 5 The implementation methods of electrode sheets and battery cells have been introduced. The following section combines... Figure 6 The preparation method of the battery cell is introduced. Similar descriptions can be found in the descriptions of the implementation methods of the electrode and the battery cell, and will not be repeated here.

[0149] [Preparation methods for battery cells]

[0150] Figure 6 This is a schematic diagram illustrating a method for preparing a battery cell according to an embodiment of this application. For example, such as... Figure 6 As shown, the method 200 for preparing a single battery cell includes the following steps.

[0151] Step 210: Place the electrode assembly 33 in the container.

[0152] Optionally, the electrode assembly 33 includes a main body 330 and a tab 331, the tab 331 protruding from the main body 330 along a first direction.

[0153] The electrode assembly 33 can be prepared by winding the positive electrode sheet, the separator, and the negative electrode sheet, or by stacking them.

[0154] In step 210, the electrode assembly 33 can be placed in the container alone, or the electrode tab 33a of the electrode assembly 33 can be welded to the end cap assembly 32 through the current collector 34, so that the electrode assembly 33 and the end cap assembly 32 form a component, and then the component is placed in the container.

[0155] The container can be connected to the external environment. For example, the container can be connected to a first connecting part, so that gas can be introduced into the container through the first connecting part; as another example, the container can also discharge gas from the container through a second connecting part.

[0156] As an example, the container discharges gas from inside the container through a second connecting component. The second connecting component may be equipped with special elements so that the gas inside the container can be discharged to the external environment through the second connecting component, but the gas in the external environment will not enter the container through the second connecting component.

[0157] Step 220: Gaseous silane and water vapor are introduced into the container to obtain an electrode assembly with a protective layer 35, the protective layer 35 comprising silicon oxide; the general formula of the silane satisfies: R'-Si(OR) n , where R' includes organic or inorganic functional groups, R includes alkyl groups, and n is an integer and 2≤n≤4.

[0158] Gaseous silane and water vapor can be easily introduced into the container, thus facilitating the reaction between silane and water molecules.

[0159] n can be 2, 3, or 4; R includes alkyl groups, for example, R can be methyl or ethyl; R' includes organic or inorganic functional groups, for example, R' can include amino or methyl groups. As an example, n is 3.

[0160] In silanes, the -(OR) group is a hydrolyzable group, facilitating the hydrolysis of silanes to produce -Si-OH groups. The end surface of electrode 1 and at least a portion of the surface of tab 331 have exposed metal. The -Si-OH groups can combine with the metal, and the -Si-OH groups can cross-link on the metal surface to form a protective layer 35. The reaction of silane and water vapor on the metal surface can be roughly divided into the following three steps.

[0161] (1) Silane hydrolysis: -Si-OR + H2O → -Si-OH + ROH;

[0162] (2) Adsorption on metal surface: -Si-OH+Me-OH→Me-O-Si-+H2O, where Me represents metal;

[0163] (3) Cross-linking to form a protective layer: -Si-OH+HO-Si-→-Si-O-Si-+H2O.

[0164] On the one hand, after hydrolysis, silanes are adsorbed onto the metal surface through the reaction of their -Si-OH groups with the Me-OH groups on the metal surface. Silanes form Si-O-Me at the metal interface, and the covalent bond between Si-O and Me is relatively strong, resulting in a relatively firm bond between silanes and the metal. On the other hand, the remaining silane molecules form a protective layer with a three-dimensional network structure on the metal surface through the condensation reaction between the -Si-OH groups.

[0165] Before introducing gaseous silane into a container, the silane can be vaporized outside the container (e.g., in an additional storage tank); similarly, before introducing water vapor into a container, the water can be vaporized outside the container.

[0166] By introducing gaseous silane and water vapor into the container, the silane and water vapor can be mixed, thus facilitating the reaction.

[0167] In step 220, gaseous silane can be introduced first, followed by water vapor; water vapor can be introduced first, followed by gaseous silane; or gaseous silane and water vapor can be introduced simultaneously.

[0168] As an example, silane and water vapor are stored in separate storage tanks, with valves between the storage tanks and the container. The valve of the storage tank containing silane is opened first to introduce gaseous silane into the container, and then the valve of the storage tank containing water vapor is opened to introduce water vapor into the container.

[0169] After a reaction period, a protective layer 35 can be formed on the exposed metal surface. In step 220, the protective layer 35 can be formed on the end surface and the exposed metal surface of the tab 331. Specifically, for the electrode assembly 33 formed by winding, the protective layer 35 can be formed on the first end surface 3301a and the second end surface 3301b of the electrode 1; for the electrode assembly 33 formed by stacking, the protective layer 35 can be formed on the first end surface 3301a, the second end surface 3301b, the third end surface 3302a, and the fourth end surface 3302b of the electrode 1. For the electrode assembly 33 connected to the end cap assembly 32, the protective layer 35 can also be formed on the exposed metal surface of the end cap assembly 32 and the exposed metal surface at the connection between the end cap assembly 32 and the electrode assembly 33.

[0170] Step 230: Remove the electrode assembly 33 with the protective layer 35 from the container and place it into the housing 31 to obtain the battery cell 3.

[0171] After generating a protective layer 35 of a certain thickness, the container can be cooled down, and the electrode assembly 33 with the protective layer 35 can be taken out. Then, the electrode assembly 33 is placed into the housing 31, and the end cap assembly 32 is connected to the housing 31 to obtain the battery cell 3.

[0172] In this embodiment, gaseous silane and water vapor react on the exposed metal surface of the electrode assembly 33, thereby generating a protective layer 35 on the exposed metal surface of the electrode 1. The protective layer 35 includes silicon oxide. This reduces the risk of short circuits caused by the exposed metal in the electrode 1 contacting an electrode of opposite polarity, thus improving the reliability of the battery cell 3. The electrode assembly 33 with the protective layer 35 is removed from the container and placed into the housing 31, facilitating the assembly of the battery cell 3. Furthermore, since the housing 31 is not placed inside the container, the protective layer 35 is not generated inside the housing, thereby reducing the adverse effects of the protective layer 35 on the battery cell. Therefore, the battery cell 3 obtained by this technical solution has better overall performance.

[0173] Furthermore, the battery cell preparation method in this application embodiment does not employ a vacuuming process for the container. This reduces the complexity of the operation and also helps to reduce the risk of silane or other substances penetrating or adsorbing onto the active material layer of the electrode 1, thereby reducing the adverse effects on the electrical performance (e.g., cycle performance, power, resistance) of the battery cell.

[0174] Silanes have high reliability and a very low risk of explosion in containers. By adding silanes into containers, the reliability of the battery cell preparation method is improved; moreover, the requirements for the conditions inside the container are lower, which helps to reduce the complexity of the preparation method.

[0175] In some embodiments, step 210 includes connecting the electrode assembly 33 to the end cap assembly 32 and placing the electrode assembly 33 connected to the end cap assembly 32 in a container. This allows for the processing of the electrode assembly 33 and the end cap assembly 32 as a single unit, which facilitates the preparation of a protective layer 35 at the connection point between the electrode assembly 33 and the end cap assembly 32.

[0176] As an example, in the case where a protective layer 35 is prepared after the tab 33a is connected to the end cap assembly 32 via the current collector 34, the metal in the area where the tab 33a is connected to the current collector 34 is not exposed, and the protective layer 35 is not provided in this area.

[0177] In some embodiments, the boiling point of the silane is less than or equal to 200°C.

[0178] This allows silane to be converted into gaseous silane at temperatures of 200°C or below, which helps save energy. Furthermore, the container temperature can be set at 200°C or below, which facilitates the reaction between silane and water molecules at lower temperatures.

[0179] In some embodiments, the silane includes at least one selected from (H5C2O)3Si-CH2CH2-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-S4-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-CO-NH2, CH2OCHCH2-O-(CH2)3-Si(OCH3)3, or CH3-Si(OCH3)3. The silanes using these substances are readily hydrolyzed; and the silanes described above have suitable boiling points, facilitating the yield of gaseous silanes.

[0180] As an example, the silane is CH3-Si(OCH3)3. This helps to reduce steric hindrance, facilitates cross-linking between -Si-OH groups, thereby facilitating the preparation of the protective layer 35, reducing the temperature or time required to prepare the protective layer 35, and thus reducing the risk of excessive silane penetration into the electrode.

[0181] In some embodiments, the inlet flow rate Q of gaseous silane and / or water vapor satisfies: 0.1 L / min ≤ Q ≤ 2 L / min.

[0182] The inflow rate can refer to the rate at which gaseous silane or water vapor is introduced into the container. The inflow rates of gaseous silane and water vapor can be the same or different. As an example, the inflow rates of gaseous silane and water vapor are the same.

[0183] Q can be 0.1 L / min, 1 L / min, 2 L / min or any value within the above range.

[0184] As another example, the flow rate of water vapor is greater than that of silane. This excess water vapor promotes the hydrolysis of silane and also helps reduce waste of silane.

[0185] By setting Q to meet the above range, gaseous silane and water vapor enter the container at a more suitable rate, which facilitates the reaction of gaseous silane and water vapor on the metal surface and facilitates the formation of the protective layer 35; at the same time, it also helps to reduce the risk of silane penetrating into the exposed metal of the electrode assembly.

[0186] In some embodiments, the reaction time t1 between gaseous silane and water vapor satisfies: 4h ≤ t1 ≤ 12h.

[0187] t1 can be 4h, 8h, 10h, 12h or any value within the above range.

[0188] The reaction time t1 can refer to the duration of gaseous silane and water vapor being introduced into the container.

[0189] By setting t1 to meet the above range, a protective layer 35 of a certain thickness can be generated in a shorter time, while reducing the risk of excessive deposition of silane in non-exposed metal locations of the electrode assembly (e.g., locations where active material layers are provided) due to excessively long reaction times.

[0190] In some embodiments, the temperature T inside the container satisfies: 60℃≤T≤150℃; optionally, 80℃≤T≤100℃.

[0191] The temperature T inside the container can be 60℃, 80℃, 100℃, 130℃, 140℃, 150℃ or any value within the above range.

[0192] As an example, after the electrode assembly 33 connected to the end cap assembly 32 is placed into the container, the container is heated to temperature T.

[0193] In the above embodiments, by reasonably setting the temperature T, it is not only convenient for the reaction of gaseous silane and water vapor on the metal surface, but also to reduce the adverse effects of excessively high temperature on the isolation membrane in the electrode assembly 33.

[0194] The preparation conditions of the protective layer 35 are related to its thickness and shear strength. For example, a shorter preparation time and lower temperature allow for the preparation of the protective layer 35 at locations where the exposed metal of the electrode has a suitable thickness and shear strength. Furthermore, a shorter preparation time and lower temperature reduce the risk of silane infiltration into non-exposed metal locations on the electrode, resulting in a lower probability of the protective layer 35 forming at these locations, thus minimizing its impact on the electrical performance of the battery cell (e.g., cycle performance, power). By appropriately setting the reaction time t1 and temperature T, it is beneficial to prepare a protective layer 35 with suitable thickness and shear strength while maintaining good electrical performance of the battery.

[0195] In some embodiments, the pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows the protective layer 35 to be generated under normal pressure, reducing the complexity of the fabrication process. Furthermore, compared to a vacuum environment inside the container, this reduces the risk of silane or other substances penetrating into the active material layer of the electrode assembly 33.

[0196] In some embodiments, the container is in communication with the external environment. That is, during the reaction of silane and water molecules, the container is in communication with the external environment, thus maintaining a relatively stable pressure inside the container.

[0197] Figure 7 This is a schematic diagram of an electrode assembly connected with an end cap assembly according to an embodiment of this application. Figure 8 This is a schematic diagram of a support structure with electrode assemblies. Figure 7 In the middle, the end cap assembly 32 is located below the electrode assembly 33. Figure 7 (Not shown in the image), the tabs 331 of the electrode assembly 33 are connected to the end cap assembly 32 via the current collector 34.

[0198] In some embodiments, such as Figure 7 and Figure 8 As shown, step 210 includes: placing multiple electrode assemblies 33 in a support 2, the support 2 covering the largest surface area of ​​the electrode assembly 33; and placing the support 2 in a container. This allows multiple electrode assemblies 33 to be processed within the container, which improves production efficiency. Furthermore, the support 2 covering the largest surface area of ​​the electrode assembly 33 helps reduce the risk of silanes or other contaminants entering the interior of the electrode assembly 33.

[0199] Figure 9 This is a schematic diagram of silane and water vapor deposition according to an embodiment of this application. (In conjunction with...) Figure 8 and Figure 9 As shown, after gaseous silane and water vapor enter the container, the silane and water vapor can move along the first direction (the direction in which the tab 331 protrudes from the main body 330), for example... Figure 8 and Figure 9 The arrow in the CC direction indicates deposition on the surfaces of electrode assembly 33 and end cap assembly 32. By controlling the conditions of the cell fabrication method, the risk of silane deposition at locations where the metal is not exposed on electrode assembly 33 (e.g., where an active material layer is provided) can be reduced, thereby mitigating the adverse effects on the cycle performance of the cell.

[0200] In some embodiments, the preparation method 200 further includes: performing a plasma surface treatment (PLASMA) on the electrode assembly 33 before placing the electrode assembly 33 in the container.

[0201] The electrode assembly 33 can be treated by plasma surface treatment. Specifically, the exposed metal locations of the electrode assembly (e.g., the first end surface 3301a, the second end surface 3301b, and the exposed metal locations of the tabs 331) are treated to clean the exposed metal, improve the surface activity of the metal, and thus facilitate the deposition and reaction of silane on the metal surface.

[0202] As an example, the exposed metal parts of the electrode assembly 33 are subjected to plasma surface treatment using an argon-oxygen mixture as a cleaning gas; then, the electrode assembly 33 is connected to the end cap assembly 23.

[0203] As an example, only the positive electrode in electrode assembly 33 undergoes plasma surface treatment. This helps reduce fabrication complexity. Furthermore, exposed metal (e.g., aluminum foil) in the positive electrode poses a greater risk of short circuits, making treatment of the positive electrode more necessary.

[0204] In the above embodiments, plasma surface treatment can improve the surface activity of the exposed metal in the electrode, which facilitates the deposition and reaction of silane on the metal surface and facilitates the preparation of the protective layer 35; and, through the above treatment, it is beneficial to obtain a protective layer 35 with high shear strength.

[0205] In some embodiments, the power S of the plasma surface treatment satisfies: 100W ≤ S ≤ 200W; and / or, the plasma surface treatment time t2 satisfies: 50s ≤ t2 ≤ 100s; and / or, the gas flow rate V1 introduced during the plasma surface treatment satisfies: 0.2L / min ≤ V1 ≤ 0.4L / min. By selecting the treatment parameters within the above range, a better plasma treatment effect can be achieved on the electrode assembly.

[0206] S can be 100W, 150W, 200W or any value within the above range, t2 can be 50s, 80s, 100s or any value within the above range, and V1 can be 0.2L / min, 0.3L / min, 0.4L / min or any value within the above range.

[0207] In some embodiments, the preparation method 200 further includes: purging the container with an inert gas before introducing the gaseous silane and water vapor into the container to purge the air inside the container. This reduces the adverse effects of air on the reaction between the silane and water vapor.

[0208] In some embodiments, the inert gas introduction time t3 satisfies: 5 min ≤ t3 ≤ 30 min; and / or, the inert gas introduction flow rate V2 satisfies: 0.1 L / min ≤ V2 ≤ 2 L / min. This allows for the rapid and efficient removal of air from the container.

[0209] The gas introduced can be nitrogen, helium, argon, or other gases.

[0210] The time t3 can be 5 min, 10 min, 30 min or any value within the above range, and the flow rate V2 can be 0.1 L / min, 1 L / min, 2 L / min or any value within the above range.

[0211] The time and flow rate of the inert gas can be set according to actual needs, as long as the air inside the container is expelled.

[0212] As an example, a protective layer is prepared using an apparatus. The apparatus may include a container, a first storage tank, a second storage tank, and a third storage tank, each equipped with a flow regulating valve and connected to the container. The container is used to house an electrode assembly connected to an end cap assembly; the first storage tank stores water; the second storage tank stores silane; and the third storage tank stores nitrogen.

[0213] In the process of preparing the protective layer, inert nitrogen gas from the third storage tank can be introduced into the container to expel the air from the container; the first and second storage tanks are heated to obtain water vapor and gaseous silane; the gaseous silane and water vapor are introduced into the container, and the silane and water molecules react on the metal surface to generate the protective layer.

[0214] In the preparation method of this application embodiment, by performing plasma surface treatment on the electrode assembly 33 before placing it in the container, it is beneficial for silane to deposit and react on the exposed metal surface of the electrode assembly 33, thereby facilitating the preparation of a protective layer with high shear strength. By reasonably setting the reaction time t1 and temperature T, it is beneficial to prepare a protective layer 35 with suitable thickness and shear strength, and the battery still has good electrical performance. By conducting the reaction of silane and water molecules on the metal surface under normal pressure, it is beneficial to reduce the risk of silane penetrating into the non-exposed metal of the electrode assembly 33, thereby reducing the adverse effect on the electrical performance of the battery. By reasonably setting the reaction flow rate of gaseous silane and water vapor, it is beneficial to the reaction between silane and water molecules, reducing the risk of silane penetrating into the non-exposed metal of the electrode assembly, and also helps to reduce the waste of silane.

[0215] [Battery]

[0216] This application provides a battery, including the battery cell 3 in any of the above embodiments, and / or the battery cell obtained by the preparation method of any of the above embodiments. Figure 10 This is a schematic diagram of a battery according to an embodiment of this application. Figure 10 As shown, battery 5 may include multiple battery cells (not shown in the figure).

[0217] Battery cells 3 can be directly assembled into battery 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 5.

[0218] [Electrical appliances]

[0219] This application provides an electrical device, including the battery described in the above embodiments.

[0220] Figure 11 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 11 As shown, this application provides an electrical device 6, which includes the battery in the above embodiment.

[0221] Alternatively, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., as is the case in the embodiments of this application.

[0222] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0223] [Examples of methods for preparing battery cells]

[0224] Example 1

[0225] (1) The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 93:2:5 to form a uniform positive electrode slurry. The positive electrode slurry is coated onto a 12μm thick aluminum foil, and after drying, rolling, slitting, and die-cutting, a positive electrode sheet is obtained.

[0226] (2) The exposed aluminum foil of the positive electrode sheet was subjected to PLASMA plasma treatment. During the treatment, an argon-oxygen mixture was used as the cleaning gas, the cleaning power S was 100W, the cleaning time t2 was 100s, and the gas flow rate V1 was 0.2L / min.

[0227] (3) The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber emulsion (SBR) are thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry; the negative electrode slurry is coated on an 8μm thick copper foil, and after drying and other processes, a negative electrode sheet is obtained.

[0228] (4) The positive electrode, the separator (9μm thick PE film) and the negative electrode are stacked in sequence and then wound to obtain an electrode assembly. The electrode assembly itself has aluminum positive electrode tabs and copper negative electrode tabs. The positive and negative electrode tabs are welded to the aluminum positive electrode adapter and the copper negative electrode adapter respectively. Then the positive and negative electrode adapters are welded to the positive and negative electrode posts of the end cap assembly respectively to obtain a battery component including the electrode assembly and the end cap assembly.

[0229] (5) Place the above battery components in a container, heat the container to temperature T, which is 80°C, and simultaneously introduce nitrogen gas into the container as a protective gas at a flow rate of 1L / min for 10min to purge the air from the container.

[0230] (6) Propyltrimethoxysilane CH3CH2CH2-Si(OCH3)3 is heated to 142℃ to vaporize the silane. Gaseous silane is introduced into the container at a flow rate Q of 0.1 L / min. Water vapor is introduced into the container at a flow rate Q of 0.1 L / min. The total reaction time t1 is controlled at 10 h.

[0231] (7) After the reaction time is reached, stop the introduction of gaseous silane and water vapor and cool the container. Then, remove the components consisting of the electrode assembly and end cap assembly from the container and weld them to the shell to assemble the battery cell.

[0232] Examples 2-6

[0233] The difference between Examples 2-6 and Example 1 is that the container temperature T is different.

[0234] Examples 7-9

[0235] The difference between Examples 7-9 and Example 1 is that the reaction time t1 of gaseous silane and water vapor is different.

[0236] Examples 10-12

[0237] The difference between Examples 10-12 and Example 1 is that the flow rates Q of gaseous silane and water vapor introduced into the container are different.

[0238] Example 13

[0239] The difference between Example 13 and Example 1 is that the type of silane is different.

[0240] Example 14

[0241] The difference between Example 14 and Example 1 is that the exposed aluminum foil of the positive electrode was not subjected to PLASMA plasma treatment.

[0242] Comparative Example 1

[0243] The main difference between Comparative Example 1 and Example 1 is that: in Comparative Example 1, trimethylaluminum and water vapor are used for the reaction, and vacuum treatment is required during the reaction process, as follows.

[0244] (1) The positive electrode sheet, the negative electrode sheet and the separator are wound into an electrode assembly, and the electrode assembly and the end cap assembly are welded together to obtain a battery component including the electrode assembly and the end cap assembly.

[0245] (2) Place the battery components in the cavity, control the temperature of the cavity at 70°C, and evacuate the cavity to 50Pa.

[0246] (3) Introduce gaseous trimethylaluminum into the cavity until the pressure rises to 50 Pa, and maintain this pressure for 10 s;

[0247] (4) Evacuate the cavity to 50 Pa;

[0248] (5) Introduce water vapor into the cavity until the pressure rises to 50 Pa, and maintain this pressure for 5 seconds;

[0249] (6) Repeat steps (2)-(5) a total of 500 times to form an aluminum oxide protective layer on the surface of the battery component.

[0250] [Example of a single battery cell]

[0251] Examples 1-14 of the battery cells can be prepared by the preparation methods of the battery cells described in Examples 1-14.

[0252] Table 1. Parameters of Examples and Comparative Examples of Battery Cell Preparation Methods

[0253]

[0254] Table 2 Comparative Examples and Embodiments of Individual Battery Cells

[0255]

[0256]

[0257] [Testing the thickness of the protective layer]

[0258] The electrode assembly was disassembled, and the thickness of the protective layer at the first end surface 3301a, the second end surface 3301b, and the tab 331 of the positive electrode were observed using a scanning electron microscope (e.g., ZEISS sigma 300).

[0259] [Composition of the protective layer]

[0260] Elemental analysis of the relevant surface region was performed using energy-dispersive X-ray spectroscopy (EDS) on the ZEISS sigma 300 instrument. Based on the instrument data, the distribution of each element was obtained, thus determining the mass percentage of Si.

[0261] As an example, a sample is taken at the second end surface 3301b in the direction in which the active material layer is disposed (e.g., combined with...). Figure 2As shown, a sample is taken along the y-direction at the second end surface 3301b, and a 10mm × 10mm area is cut out to obtain the sample. The sample is placed in the testing equipment for elemental analysis. Referring to GB-T17359-2012 microbeam analysis energy dispersive spectroscopy for quantitative analysis, the proportions of C, Ni, Co, Mn, O, and Si can be measured (when the active material in the electrode is a ternary material), or the proportions of C, Fe, O, and Si (when the active material in the electrode is lithium iron phosphate). Specifically, the Si content at a position 5mm from the second end surface 3301b can be measured using a scale on the equipment to locate the point 5mm from the second end surface 3301b and then measure the Si content at that point.

[0262] It should be noted that when an insulating layer is provided on the surface of the main body of the electrode, sampling should be performed in areas that avoid the insulating layer.

[0263] [Shear strength test]

[0264] A tab with a protective layer is used as the test sample. The test sample is adhered to a stainless steel plate using double-sided tape, with the length of the test sample extending beyond the stainless steel plate by a certain distance. A tensile testing machine clamps the end of the test sample extending beyond the stainless steel plate and pulls it upwards until the test sample detaches from the stainless steel plate. As an example, the test sample is adhered to the stainless steel plate using 15mm long double-sided tape. At the end of the test, the area of ​​the test sample corresponding to the 9mm × 9mm area of ​​the double-sided tape detaches from the stainless steel plate.

[0265] The shear strength is calculated based on the tensile testing results: Shear strength = Shear force / Bonded area. In the example above, the bonded area is 9mm × 9mm.

[0266] It should be noted that in this embodiment, the bonding strength between the protective layer and the electrode assembly is relatively large. Therefore, the test is conducted on the strength of a specific area of ​​the sample being tested when it is separated from the stainless steel plate (i.e., the strength of the entire 9mm×9mm area being separated from the stainless steel plate), rather than the strength of any area of ​​the sample being tested when it is separated from the stainless steel plate (i.e., not the strength of any position within the 15mm length being separated from the stainless steel plate).

[0267] After immersing the electrode assembly in the electrolyte at 60°C for 7 days, the electrode assembly was disassembled, and the shear strength of the tab with the protective layer on the positive electrode was tested again. It should be noted that during the immersion of the electrode assembly in the electrolyte at 60°C, the shear strength was tested every other day. The shear strength obtained on the 7th day showed a gradually flattening trend (i.e., the shear strength did not decrease significantly or decreased only slightly after the 7th day). The shear strength on the 7th day was used to reflect the durability of the protective layer.

[0268] [Vibration Test]

[0269] The electrode assembly was subjected to vibration testing to detect the change in silicon content on the end surface after vibration compared to before vibration. As an example, vibration tests were performed in three mutually perpendicular directions, repeated 12 times in each direction, maintaining an amplitude of 8 mm and a frequency of 200 Hz.

[0270] The change in silicon content before and after vibration testing reflects the bonding strength between the protective layer and the electrode. The smaller decrease in silicon content after vibration testing indicates a higher bonding strength between the protective layer and the electrode.

[0271] [Cyclic Performance Testing]

[0272] The battery cells were charged and discharged at 25°C. One charge-discharge cycle was as follows: constant current charging at 1C to 4.25V, then constant voltage charging continued until the charging current was less than 0.05C and then stopped; paused for 30 minutes; constant current discharging at 1C to 2.5V; paused for 30 minutes.

[0273] After one charge-discharge cycle, the discharge capacity of the battery cell is recorded; this is the initial discharge capacity.

[0274] After 500 charge-discharge cycles, the discharge capacity after 500 cycles is recorded. The capacity retention rate after 500 cycles = discharge capacity after 500 cycles / initial discharge capacity.

[0275] In the embodiments of the battery cell preparation method, combined with Examples 1-14 and Comparative Example 1, the preparation method of this application is simpler, and an electrode assembly with a protective layer can be obtained without vacuuming. Furthermore, compared to methods that involve vacuuming during the preparation of the protective layer, not performing vacuuming helps reduce the risk of excessive silane penetration into the non-exposed metal areas of the electrode assembly (the non-exposed metal areas of the electrode sheet). Since silicon oxide or silicon is non-conductive, the deposition of silane or the formation of silicon oxide at non-exposed metal areas will affect conductivity, thereby affecting the electrical performance of the battery cell (e.g., capacity retention). Therefore, the electrode sheet prepared by the method of this application has a very low Si content at a position 5 mm from the end surface, and the battery cell has a high capacity retention rate.

[0276] As shown in Examples 1-14, the protective layer exhibits high shear strength, and retains this strength even after immersion in the electrolyte. The risk of the protective layer detaching is low, allowing the battery cell to be used in long-term applications such as energy storage devices. Furthermore, the end surface retains a certain amount of the protective layer even after being subjected to vibration or other factors, thus providing a degree of protection. As shown in Examples 1 and 14, plasma cleaning of the electrode assembly (or positive electrode sheet) before preparing the protective layer is beneficial for obtaining a protective layer with even higher shear strength.

[0277] As shown in Examples 1-6, increasing the temperature inside the container promotes the reaction between silane and water molecules, resulting in a thicker protective layer with greater shear strength. As shown in Examples 5-6, when the container temperature T exceeds 130°C, although the protective layer thickness increases, the reaction between silane and water molecules intensifies due to the higher temperature, increasing the risk of silicon oxide formation at a position 5mm from the end surface. The Si content exceeds 0.01%, resulting in a lower improvement in battery capacity retention. As shown in Examples 1-4, by setting the container temperature T within the range of 60°C to 130°C, a protective layer of suitable thickness can be produced, with the Si content at a position 5mm from the end face approaching zero. The battery cell capacity retention is around 90%, thus achieving a balance between high shear strength and cycle performance. Furthermore, in conjunction with Examples 1-3, for the same type of silane, setting the temperature T inside the container within the range of 80°C to 100°C is beneficial for generating a thicker protective layer, and the temperature not exceeding 100°C is also beneficial for reducing the adverse effects of excessively high temperatures on the diaphragm.

[0278] As shown in Examples 7-9, the reaction time of silane and water vapor is related to the thickness of the protective layer. By setting the reaction time t1 to between 4h and 12h, a protective layer of suitable thickness can be generated.

[0279] As shown in Examples 10-12, controlling the flow rate of gaseous silane and water vapor into the container facilitates thorough mixing and reaction of the silane and water vapor; increasing the flow rate allows for the formation of a thicker protective layer within the same time frame. Setting the flow rate between 0.1 L / min and 2 L / min not only helps obtain a protective layer of suitable thickness but also reduces waste of raw materials such as silane caused by excessively high flow rates.

[0280] As shown in Example 13, the preparation method of this application is also applicable to various hydrolyzable silanes. In this application, different container temperatures can be selected depending on the type of silane.

[0281] It should be noted that the above embodiments and comparative examples use aluminum foil as the current collector for the positive electrode sheet. The embodiments of this application can also be applied to positive electrode sheets and negative electrode sheets with current collectors made of other materials.

[0282] 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. An electrode sheet, characterized in that, The electrode includes a main body and an electrode tab. The electrode tab protrudes from the main body in a first direction. A protective layer is provided on the end surface of the main body in the first direction. The protective layer includes silicon oxide. The shear strength G of the protective layer satisfies: G≥110MPa. The shear strength of the protective layer is the ratio of the shear force required to detach the protective layer from the stainless steel plate when it is adhered to the stainless steel plate with double-sided tape to the adhesive area of ​​the protective layer and the double-sided tape.

2. The electrode sheet according to claim 1, characterized in that, 110MPa≤G≤1300MPa.

3. The electrode sheet according to claim 2, characterized in that, 300MPa≤G≤1000MPa.

4. The electrode sheet according to any one of claims 1-3, characterized in that, The thickness d1 of the protective layer satisfies: 20nm≤d1≤220nm.

5. The electrode sheet according to claim 4, characterized in that, 100nm≤d1≤170nm.

6. The electrode sheet according to any one of claims 1-3, characterized in that, Based on the total mass of all elements at the first position of the electrode, the mass content A of Si element satisfies: A≤2wt%, and the first position is a position 5mm away from the end surface.

7. The electrode sheet according to claim 6, characterized in that, A < 0.01wt%.

8. The electrode sheet according to any one of claims 1-3, characterized in that, The protective layer is provided at least a portion of the electrode tab.

9. The electrode sheet according to claim 8, characterized in that, The protective layer is provided on the end surface of the main body along the second direction, which is perpendicular to the first direction and parallel to the surface where the electrode is located.

10. The electrode sheet according to any one of claims 1-3, characterized in that, The electrode is a positive electrode, and the positive electrode includes a positive active material, which includes a layered transition metal oxide.

11. The electrode according to claim 10, characterized in that, The layered transition metal oxide includes LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.6 Co 0.2 Mn 0.2 At least one of O2.

12. An electrode assembly, characterized in that, include: The electrode as described in any one of claims 1-11.

13. A single battery cell, characterized in that, include: The electrode assembly as described in claim 12; A housing for accommodating the electrode assembly.

14. A method for preparing a battery cell as described in claim 13, characterized in that, include: Place the electrode assembly in the container; Gaseous silane and water vapor are introduced into the container to obtain an electrode assembly with a protective layer comprising silicon oxide, wherein the silane has the general formula: R'-Si(OR). n Wherein, R' includes organic or inorganic functional groups, R includes alkyl groups, and n is an integer and 2≤n≤4; The electrode assembly with the protective layer is removed from the container and placed into the housing to obtain the battery cell.

15. The preparation method according to claim 14, characterized in that, The step of placing the electrode assembly in the container includes: The electrode assembly is connected to the end cap assembly, and the electrode assembly with the end cap assembly connected is placed in the container.

16. The preparation method according to claim 14, characterized in that, The boiling point of the silane is less than or equal to 200°C.

17. The preparation method according to any one of claims 14-16, characterized in that, The silane includes at least one of (H5C2O)3Si-CH2CH2-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-S4-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-CO-NH2, CH2OCHCH2-O-(CH2)3-Si(OCH3)3, or CH3-Si(OCH3)3.

18. The preparation method according to any one of claims 14-16, characterized in that, The temperature T inside the container satisfies: 60℃≤T≤150℃.

19. The preparation method according to claim 18, characterized in that, The temperature T inside the container satisfies: 80℃≤T≤100℃.

20. The preparation method according to any one of claims 14-16, characterized in that, The reaction time t1 between the gaseous silane and the water vapor satisfies: 4h ≤ t1 ≤ 12h.

21. The preparation method according to any one of claims 14-16, characterized in that, The flow rate Q of the gaseous silane and / or the water vapor satisfies: 0.1 L / min ≤ Q ≤ 2 L / min.

22. The preparation method according to any one of claims 14-16, characterized in that, The pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa.

23. The preparation method according to any one of claims 14-16, characterized in that, The preparation method further includes: Before placing the electrode assembly in the container, the electrode assembly undergoes a plasma surface treatment.

24. The preparation method according to claim 23, characterized in that, The power S of the plasma surface treatment satisfies: 100W≤S≤200W; and / or the time t2 of the plasma surface treatment satisfies: 50s≤t2≤100s; and / or the gas flow rate V1 introduced in the plasma surface treatment satisfies: 0.2L / min≤V1≤0.4L / min.

25. The preparation method according to any one of claims 14-16, characterized in that, The preparation method further includes: Before introducing gaseous silane and water vapor into the container, an inert gas is introduced into the container to purge the air inside.

26. The preparation method according to any one of claims 14-16, characterized in that, The step of placing the electrode assembly in the container includes: Multiple electrode assemblies are placed in a support, the support covering the largest surface area of ​​the electrode assemblies; Place the support in the container.

27. The preparation method according to any one of claims 14-16, characterized in that, The container is connected to the external environment.

28. A battery, characterized in that, Includes the battery cell according to claim 13; and / or the battery cell obtained by the preparation method according to any one of claims 14-27.

29. An electrical appliance, characterized in that, Includes the battery according to claim 28.

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