Electrode sheet, electrode assembly, battery cell and preparation method therefor, battery, and electric device

Abstract

An electrode sheet, an electrode assembly, a battery cell and a preparation method therefor, a battery, and an electric device, relating to the technical field of batteries. At least an end surface of the electrode sheet is provided with a protective layer, the protective layer comprises silicon oxide, and the shear strength G of the protective layer satisfies the condition: G≥110 MPa. The technical solution of the present application is beneficial to improving the reliability of the battery cell.

Description

Pole piece, electrode assembly, battery cell and preparation method thereof, battery, and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent document claims priority to and the benefit of Chinese patent application No. 202410269761.0, filed on March 8, 2024, entitled "Pole Sheet, Electrode Assembly, Battery Cell, Method for Making Same, Battery, and Electric Device." The entire contents of the aforementioned patent application are incorporated by reference into this patent document. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a pole piece, an electrode assembly, a battery cell and a preparation method thereof, a battery, and an electrical device. Background Art

[0004] With the increasing severity of environmental pollution, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0005] The development of battery technology requires consideration of multiple design factors, such as energy density, cycle life, and reliability. The design of the pole piece in a battery cell is crucial to the reliability and cycle performance of the battery cell. Therefore, how to provide a pole piece to improve the reliability of the battery cell is a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide a pole piece to improve the reliability of a battery cell.

[0008] In order to achieve the above-mentioned objectives, the present application provides a pole piece, an electrode assembly, a battery cell and a preparation method thereof, a battery, and an electrical device.

[0009] In a first aspect, a pole piece is provided, wherein at least an end surface of the pole piece is provided with a protective layer, the protective layer comprises silicon oxide, and the shear strength G of the protective layer satisfies: G ≥ 110 MPa.

[0010] In the embodiments of the present application, the provision of a protective layer can reduce the risk of short circuits caused by the end surface of the electrode piece overlapping with an electrode of opposite polarity, thereby improving the reliability of the battery cell. The shear strength G of the protective layer is ≥ 110 MPa. This ensures that the protective layer is not easily detached during long-term use of the battery cell, further improving the reliability of the battery cell.

[0011] In one possible implementation, the shear strength G of the protective layer satisfies the following conditions: 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 helping to reduce the time and temperature required to prepare the protective layer. Alternatively, 300 MPa ≤ G ≤ 1000 MPa. This ensures a relatively suitable bond between the protective layer and the electrode assembly while further reducing the time and temperature required to prepare the protective layer, which has a higher shear strength.

[0012] In a possible implementation, the thickness d1 of the protective layer satisfies: 20 nm ≤ d1 ≤ 200 nm. In this way, the protective layer can have a certain shear strength and can reduce other adverse effects caused by excessive thickness of the protective layer.

[0013] In one possible implementation, the thickness d1 of the protective layer satisfies the following conditions: 100 nm ≤ d1 ≤ 170 nm. When d1 is greater than or equal to 100 nm, the protective layer has a relatively suitable thickness, which can effectively reduce the risk of short circuits. When d1 is less than or equal to 170 nm, the protective layer has a relatively low thickness, which can reduce the adverse effects of excessive protective layer thickness on the performance of the battery cell.

[0014] In one possible implementation, the Si mass content A, based on the total mass of all elements at the first position of the electrode, satisfies the following: A ≤ 2 wt %. The first position is 5 mm from the end surface. Thus, the Si content is low at 5 mm from the end surface, thereby reducing the adverse effects of Si on the cycling performance of the battery cell. Alternatively, A < 0.01 wt %. This results in a very low or even almost non-existent Si content, further reducing its impact on the cycling performance of the battery cell.

[0015] In one possible implementation, the electrode piece includes a main body and a tab, the tab protruding from the main body along a first direction, and the protective layer is provided on an end surface of the main body along the first direction and at least a portion of the tab. This reduces the risk of short circuits caused by the end surface and the tab overlapping with electrodes of opposite polarity.

[0016] In one possible implementation, the protective layer is provided on the end surface of the main body along a second direction, where the second direction is perpendicular to the first direction and parallel to the surface on which the pole piece is located. Thus, the protective layer is provided on both the end surface of the main body along the first direction and the end surface along the second direction, further reducing the risk of short circuits caused by the pole piece overlapping an electrode of opposite polarity.

[0017] In a possible implementation, the electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide.

[0018] In the above technical solution, the battery prepared by using the above positive electrode active material has a higher energy density, so that the battery can have both higher energy density and higher reliability.

[0019] 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 The positive electrode active material has a high nickel content and a high gram capacity, which is conducive to preparing a battery with a high energy density.

[0020] In a second aspect, an electrode assembly is provided, comprising the electrode piece in the first aspect and any possible implementation thereof.

[0021] In a third aspect, 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 of the battery cell, the protective layer is unlikely to fall off, thereby further improving the reliability of the battery cell.

[0022] In a fourth aspect, 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 provided with a protective layer, wherein the protective layer comprises silicon oxide, and the silane has a general formula of: R'-Si(OR) n , wherein R' includes an organic or inorganic functional group, R includes an alkyl group, n is an integer and 2≤n≤4; the electrode assembly provided with the protective layer is taken out from the container and placed in a shell to obtain the battery cell.

[0023] In the embodiments of the present application, gaseous silane and water vapor react on the exposed metal surfaces of the electrode assembly, forming a protective layer on the exposed metal surfaces. This protective layer comprises silicon oxide. This reduces the risk of short circuits caused by the exposed metal in the electrode assembly lapped with electrodes of opposite polarity, thereby improving the reliability of the battery cells. The electrode assembly with the protective layer is removed from the container and placed within the housing, facilitating assembly of the battery cells. Furthermore, since the housing is not placed within the container, the protective layer is not formed within the housing, thereby reducing the adverse effects of the protective layer on the battery cells. Therefore, the battery cells obtained by this technical solution have excellent overall performance.

[0024] In one possible implementation, placing the electrode assembly in the container includes connecting the electrode assembly to an end cap assembly, and placing the electrode assembly with the end cap assembly connected thereto in the container. Thus, processing after the electrode assembly and the end cap assembly are connected as a whole facilitates forming a protective layer at the connection between the electrode assembly and the end cap assembly.

[0025] In a possible implementation, the boiling point of the silane is less than or equal to 200° C. This is conducive to the reaction between the silane and water molecules at a lower temperature in the container.

[0026] In one possible implementation, 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, CHOCHCH2-O-(CH2)3-Si(OCH3)3, or CH3-Si(OCH3)3. Using the above-mentioned silane facilitates hydrolysis; and the above-mentioned silane has a suitable boiling point, which facilitates obtaining gaseous silane.

[0027] In one possible implementation, the temperature T within the container satisfies the following conditions: 60°C ≤ T ≤ 150°C; alternatively, 80°C ≤ T ≤ 100°C. In the above technical solution, by properly setting the temperature T, the reaction of gaseous silane and water vapor on the metal surface is facilitated while also reducing the adverse effects of excessively high temperatures on the separator in the electrode assembly.

[0028] In one possible implementation, the reaction time t1 of the gaseous silane and the water vapor satisfies: 4h≤t1≤12h. In this way, the protective layer can be formed in a shorter time, reducing the risk of forming a protective layer on the active material layer of the electrode assembly due to excessively long reaction time.

[0029] In one possible implementation, the inlet flow rate Q of the gaseous silane and / or water vapor satisfies the following: 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 forming a protective layer. This also helps reduce the risk of silane penetrating into exposed metal areas of the electrode assembly.

[0030] In one possible implementation, the pressure P in the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows the protective layer to be formed at normal pressure, reducing the complexity of the preparation and also reducing the risk of silane penetrating into the active material layer in the electrode assembly.

[0031] In one possible implementation, placing the electrode assemblies in the container includes placing multiple electrode assemblies in a holder, the holder covering the largest surface area of ​​the electrode assemblies; and placing the holder in the container. This allows multiple electrode assemblies to be processed in the container, improving production efficiency. Furthermore, the holder covering the largest surface area of ​​the electrode assemblies also reduces the risk of silane and other substances entering the interior of the electrode assemblies.

[0032] In one possible implementation, the preparation method further includes: performing a plasma surface treatment on the electrode assembly before placing the electrode assembly in the container. This can increase the surface activity of the exposed metal in the electrode assembly, facilitate the deposition and reaction of silane on the metal surface, and facilitate the preparation of the protective layer.

[0033] In one possible implementation, the power S of the plasma surface treatment satisfies the following: 100 W ≤ S ≤ 200 W; and / or the time t2 of the plasma surface treatment satisfies the following: 50 s ≤ t2 ≤ 100 s; and / or the gas flow rate V1 during the plasma surface treatment satisfies the following: 0.2 L / min ≤ V1 ≤ 0.4 L / min. By selecting treatment parameters within the above ranges, a better plasma treatment effect can be achieved on the electrode assembly.

[0034] In one possible implementation, the preparation method further includes: before introducing the gaseous silane and water vapor into the container, introducing an inert gas into the container to evacuate the air from the container. This can reduce the adverse effects of air on the reaction between the silane and water vapor.

[0035] In one possible implementation, the container is in communication with the external environment, so that a relatively constant pressure can be maintained in the container.

[0036] In a fifth aspect, a battery is provided, comprising the battery cell of the third aspect, and / or a battery cell obtained according to the preparation method of the fourth aspect and any possible implementation thereof.

[0037] In a sixth aspect, an electrical device is provided, comprising the battery described in the fifth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0039] FIG1 is a schematic structural diagram of a pole piece before cutting the pole lugs according to an embodiment of the present application;

[0040] FIG2 is a schematic structural diagram of a pole piece after cutting the pole lugs according to an embodiment of the present application;

[0041] FIG3 is a cross-sectional view along the AA direction in FIG2 ;

[0042] FIG4 is a cross-sectional view along the BB direction in FIG2 ;

[0043] FIG5 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0044] FIG6 is a schematic diagram of a method for preparing a battery cell according to an embodiment of the present application;

[0045] FIG7 is a schematic diagram of an electrode assembly connected to an end cap assembly according to an embodiment of the present application;

[0046] FIG8 is a schematic diagram of a bracket provided with an electrode assembly;

[0047] FIG9 is a schematic diagram of silane and water vapor deposition according to an embodiment of the present application;

[0048] FIG10 is a schematic diagram of a battery according to an embodiment of the present application;

[0049] FIG11 is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0050] The embodiments of the electrode sheet, electrode assembly, battery cell and its preparation method, battery, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0051] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0055] The development of battery technology must simultaneously consider multiple design factors, such as energy density, cycle life, discharge capacity, charge and discharge rate, reliability, etc. After cutting, the exposed metal of the electrode in the battery cell is at risk of short circuiting by overlapping with electrodes of opposite polarity or other components of the battery cell. In some processing methods, a corresponding protective layer is provided at the exposed metal position of the electrode assembly to reduce the risk of short circuit and improve the reliability of the battery cell. However, the bonding strength between the protective layer and the electrode assembly is low, and it is easy to fall off after long-term use, which has limited improvement in the reliability of the battery cell.

[0056] In light of this, the present application provides a pole piece having a protective layer disposed on at least one end surface of the pole piece. The protective layer comprises silicon oxide and has a shear strength G satisfying the requirement of G ≥ 110 MPa. This protective layer exhibits high shear strength and is less likely to fall off the pole piece, thereby improving the reliability of the battery cell.

[0057] [Pole piece]

[0058] Figure 1 is a schematic structural diagram of the pole piece of an embodiment of the present application before the pole lug is cut, Figure 2 is a schematic structural diagram of the pole piece of an embodiment of the present application after the pole lug is cut, Figure 3 is a cross-sectional view along the AA direction in Figure 2, and Figure 4 is a cross-sectional view along the BB direction in Figure 2.

[0059] In one embodiment of the present application, for example, as shown in FIG. 1 to FIG. 4 , a protective layer 35 is provided on at least the end surface of the pole piece 1 . The protective layer 35 includes silicon oxide, and the shear strength G of the protective layer 35 satisfies: G ≥ 110 MPa.

[0060] The end surface of the pole piece 1 may include any one of opposite end surfaces along a first direction (eg, y direction in the figure) of the pole piece 1 and opposite end surfaces along a second direction (eg, x direction in the figure).

[0061] The surfaces of the two opposite ends along the first direction of the pole piece 1 may include a first end surface 3301 a and a second end surface 3301 b .

[0062] The surfaces of the two opposite ends along the second direction of the pole piece 1 may include a third end surface 3302a and a fourth end surface 3302b.

[0063] The end surface of the electrode 1 may be a surface formed by cutting, and after cutting, the metal on the end surface is exposed. For example, as shown in Figures 1 to 3, 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 along the cutting line 124 to prepare the electrode ear 331, and the second end surface 3301b may be a surface generated by cutting during the process of striping the electrode 1. Striping may refer to the process of cutting a large electrode into multiple small electrode pieces 1 by cutting.

[0064] As an example, the end surface along the first direction and the end surface along the second direction are both provided with the protection layer 35 .

[0065] As another example, as shown in FIG. 1 to FIG. 4 , the end surface of the pole piece 1 along the first direction is provided with a protective layer 35 , and the end surface of the pole piece 1 along the second direction is not provided with a protective layer 35 .

[0066] As another example, the end surface of the pole piece 1 along the first direction close to the pole ear (the first end surface 3301a) is provided with a protective layer 35, and the end surface of the end away from the pole ear (the second end surface 3301b) is not provided with a protective layer 35; and the end surface along the second direction of the pole piece 1 is not provided with a protective layer 35.

[0067] The protective layer 35 includes silicon oxide, wherein the silicon oxide may have the following structure: -Si-O-Si-. The silicon oxide is not likely to swell when immersed in the electrolyte and is not likely to fall off during long-term use of the battery cell 3.

[0068] The protective layer 35 has certain insulating properties, which can reduce the risk of short circuit caused by the end surface overlapping with the electrode with opposite polarity, and is beneficial to improving the reliability of the battery cell.

[0069] The shear strength G of the protective layer 35 satisfies: G≥110 MPa. In this way, the protective layer 35 is not easy to fall off from the electrode sheet 1, and is not easy to fall off from the electrode sheet 1 after long-term immersion in electrolyte, which is conducive to further improving the reliability of the battery cell.

[0070] In the embodiment of the present application, a protective layer 35 is provided on at least the end surface of the electrode 1. The protective layer 35 comprises silicon oxide and has a shear strength G that satisfies the requirement of G ≥ 110 MPa. The provision of the protective layer 35 can reduce the risk of short circuits in the battery cell and is not easily detached, thereby improving the reliability of the battery cell 3.

[0071] In some embodiments, the shear strength G of the protective layer 35 satisfies: 110 MPa≤G≤1300 MPa. G can be 110 MPa, 200 MPa, 500 MPa, 1000 MPa, 1300 MPa, or any value within the above range.

[0072] The shear strength of the protective layer 35 is related to the thickness of the protective layer 35. In the embodiment of the present application, the greater the thickness of the protective layer 35, the greater the shear strength of the protective layer 35.

[0073] The shear strength of the protective layer 35 reflects the bond 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 the protective layer 35 and the electrode 1, and the lower the risk of the protective layer 35 falling off 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 low, making the protective layer 35 less likely to fall off, thereby improving the reliability of the battery cell 3.

[0074] The test method for the shear strength of the protective layer 35 can be found in the test method section below.

[0075] 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 pole piece 1 is low; when the shear strength of the protective layer 35 is less than or equal to 1300 MPa, it is convenient to prepare the protective layer 35, which is beneficial to reduce the time required for preparing the protective layer 35 and the temperature required for preparing the protective layer 35.

[0076] In some embodiments, 300 MPa≤G≤1000 MPa. G can be 300 MPa, 400 MPa, 500 MPa, 800 MPa, 1000 MPa, or any value within the above range.

[0077] In this embodiment, 300 MPa≤G≤1000 MPa, the protective layer 35 and the electrode 1 have a relatively suitable bonding strength, and are conducive to further reducing the time and temperature required for preparing the protective layer 35 with higher shear strength.

[0078] In some embodiments, the thickness d1 of the protection layer 35 satisfies: 20 nm≤d1≤200 nm.

[0079] The thickness d1 of the protective layer 35 can be 190 nm, 160 nm, 100 nm, 50 nm, 20 nm, or any value within the foregoing range. The thickness d1 of the protective layer 35 can be the average thickness of the protective layer 35. For example, the thickness d1 can be measured at multiple locations on the end surface, and the average of the multiple data points can be used as the thickness at the end surface.

[0080] At different locations, for example, at the first end surface 3301 a and the second end surface 3301 b , the protective layer 35 has the same or substantially the same thickness.

[0081] When d1 is greater than or equal to 20 nm, the protective layer 35 has a relatively suitable thickness, which can effectively reduce the risk of short circuit, and the protective layer 35 has a certain shear strength, and the risk of falling off is low; when d1 is less than or equal to 200 nm, the adverse effect of the excessive thickness of the protective layer 35 on the performance of the battery cell 3 can be reduced.

[0082] In some embodiments, the thickness d1 of the protective layer 35 satisfies: 100 nm≤d1≤170 nm. d1 can be 100 nm, 120 nm, 160 nm, 170 nm, or any value within the above range.

[0083] When d1 is greater than or equal to 100 nm, the protective layer 35 has a relatively suitable thickness, which can effectively reduce the risk of short circuit; when d1 is less than or equal to 170 nm, the thickness of the protective layer 35 is relatively small, which can reduce the adverse effects of excessive thickness of the protective layer 35 on the performance of the battery cell 3.

[0084] In some embodiments, based on the total mass of all elements at the first position of the pole piece 1 , the mass content A of the Si element satisfies: A≤2 wt %, and the first position is 5 mm away from the end surface.

[0085] The first position may be a position in the pole piece 1 that is 5 mm away from the end surface along any direction.

[0086] As an example, the first position is a position that is 5 mm away from the second end surface 3301 b along the first direction (y direction in the figure).

[0087] As another example, the first position is a position that is 5 mm away from the third end surface 3302 a along the second direction (x direction in the figure).

[0088] The first location of the electrode sheet contains multiple elements of the material that makes up the electrode sheet 1. For example, for a positive electrode sheet, the first location of the positive electrode sheet includes elements of the material that makes up the positive electrode current collector, such as Al; elements of the material that makes up the positive electrode film layer, and Si that may penetrate into the positive electrode film layer. For a negative electrode sheet, the first location of the negative electrode sheet includes elements of the material that makes up the negative electrode current collector, such as Cu; elements of the material that makes up the negative electrode film layer, and Si that may penetrate into the negative electrode film layer.

[0089] During the preparation of the protective layer 35, the raw materials for preparing the protective layer 35, such as silane and water, are deposited and reacted on the electrode 1. The mass content of the Si element can reflect the degree of silane penetration or adhesion to the electrode 1, or can reflect the content of silicon oxide on the electrode 1.

[0090] Silicon oxide or silicon affects the conductivity of the electrode, thereby affecting the electrical performance of the battery cell, such as the capacity retention rate, power, and resistance of the battery cell.

[0091] When the mass content of Si at the first position is less than or equal to 2 wt%, the silicon oxide content or silane infiltration is low. Thus, the risk of silicon oxide or silane being present in areas other than the end surface 3301 of the electrode assembly 33 is low, thereby minimizing the impact on the performance of the battery cell and reducing the impact on the cycle performance of the battery cell.

[0092] In some embodiments, A<0.01 wt %. In this way, the Si content at the first position of the electrode is relatively low, thereby reducing the adverse effects of silicon oxide containing Si on the cycle performance of the battery cell.

[0093] In this embodiment, the Si content at the first position 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. The risk of the protective layer 35 falling off during extended use of the battery cell is significantly reduced. This battery cell is suitable for long-term use scenarios, such as in the energy storage field.

[0094] In some embodiments, the metal on the end surface is chemically bonded to the silicon oxide in the protection layer 35. Specifically, the metal and the silicon oxide are bonded to each other through a covalent bond.

[0095] As an example, the combination of metal and silicon oxide is represented by: Me-Si-O-Si, where Me represents metal.

[0096] As an example, Me is aluminum. As another example, Me is copper.

[0097] The shear strength of the protective layer 35 is related to the connection between the protective layer 35 and the exposed metal of the pole piece 1. In addition, before preparing the protective layer 35, plasma surface treatment is performed on the pole piece 1 to further enhance the shear strength of the protective layer 35.

[0098] In this embodiment, the bonding force between the protective layer 35 and the end surface 3301 is relatively strong, and the protective layer 35 is not easy to fall off.

[0099] In some embodiments, the pole piece 1 includes a main body 330 and a tab 331 . The tab 331 protrudes from the main body 330 along a first direction. A protective layer 35 is provided on the end surface of the main body 330 along the first direction and at least a portion of the tab 331 .

[0100] The first direction is the direction in which the tab 331 protrudes from the main body 330 . For example, as shown in FIG. 2 , the first direction is the y direction.

[0101] At least part of the tab 331 is provided with a protective layer 35. It is understandable that the protective layer 35 is provided on part of the tab 331 or on the entire tab 331. At least part of the tab 331 may refer to the exposed metal portion of the tab 331.

[0102] As an example, as shown in Figure 2, 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 close to the main body 330 relative to the second part 3312; the main body 330 includes a first area 3302 and a second area 3303 connected, and the second area 3303 is close to the tab 331 relative to the first area 3302; the first part 3311 of the tab 331 and the second area 3303 of the main body 330 are coated with an insulating material, the second part 3312 of the tab 331 is a bare aluminum foil, and the first area 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.

[0103] As another example, the entire area of ​​the main body 330 is coated with active material, the entire area of ​​the tab 331 is exposed aluminum foil, and the entire area of ​​the tab 331 is provided with a protective layer 35 .

[0104] In some embodiments, the exposed metal in the tab 331 is chemically bonded to the silicon oxide in the protective layer 35. This reduces the risk of short circuits caused by the tab 331 overlapping with electrodes of opposite polarity.

[0105] In some embodiments, a protective layer 35 is provided on the end surface of the main body 330 along a second direction, and the second direction is perpendicular to the first direction and parallel to the surface where the pole piece 1 is located. For example, the second direction is the x direction in FIG1 .

[0106] In this embodiment, the end surface of the main body 330 along the second direction and the end surface along the first direction are both provided with a protective layer 35, which is beneficial to further reduce the risk of short circuit caused by the pole piece 1 overlapping with the electrode of opposite polarity.

[0107] In some embodiments, the electrode sheet is a positive electrode sheet, which includes a positive electrode active material, which includes a layered transition metal oxide. Batteries fabricated using this positive electrode active material have a higher energy density, thereby achieving both high energy density and high reliability.

[0108] Layered transition metal oxides may include ternary materials, lithium cobalt oxide, lithium-rich manganese-based materials, and the like.

[0109] As an example, the chemical formula of a layered transition metal oxide 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。

[0110] a may be 0.6, 0.7, 0.8, 0.9 or any value within the above ranges, b may be 0.1, 0.2, 0.3 or any value within the above ranges, c may be 0.1, 0.2, 0.3 or any value within the above ranges, d may be 0, 0.1, 0.6, 0.6, 0.8 or any value within the above ranges, x may be 0.2, 0.5, 1, 1.2 or any value within the above ranges, and y may be 0, 0.5, 1, 1.5, 2 or any value within the above ranges.

[0111] When d is greater than 0, the layered transition metal oxide includes the M element, and the layered transition metal oxide may have higher stability; when d is 0, the layered transition metal oxide does not include the M element.

[0112] It is understood that the position of the M ion in the layered transition metal oxide structure can be to replace a portion of the transition metal. For example, in the case where the layered transition metal oxide is a nickel-cobalt-manganese-based ternary material, the M ion can replace a portion of the manganese site, the nickel site, or the cobalt site.

[0113] In the case of y=0, the layered transition metal oxide does not include N. It is understood that the position of N ions in the layered transition metal oxide structure may be a position that replaces a portion of O.

[0114] The battery is accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above limitation on x includes the molar content of Li in different charge and discharge states of the battery (usually the battery voltage is between 2-5V).

[0115] In the above technical solution, the positive electrode active material satisfying the above chemical formula has a higher nickel content, the positive electrode active material has a higher gram capacity, and the battery has a higher energy density and higher reliability.

[0116] In some embodiments, the layered transition metal oxide comprises LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.6 Co 0.2 Mn 0.2 The positive electrode active material has a high gram capacity, which is conducive to preparing a battery with a high energy density.

[0117] The electrode piece 1 can be a positive electrode piece or a negative electrode piece. As an example, both the positive electrode piece and the negative electrode piece have the structure described above for the electrode piece 1.

[0118] [Positive electrode]

[0119] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on the positive electrode current collector.

[0120] The positive electrode current collector may be a metal foil or a composite current collector. For example, the positive electrode current collector may be an aluminum foil.

[0121] The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0122] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be any positive electrode active material known in the art for use in batteries. For example, the positive electrode active material is lithium iron phosphate, a ternary material, or a lithium-rich manganese-based material.

[0123] The positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0124] The positive electrode film layer may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0125] [Negative electrode]

[0126] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.

[0127] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0128] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for batteries that is well known in the art. 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, 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, the present application is not limited to these materials, and other traditional 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.

[0129] The negative electrode film layer may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0130] [Electrolytes]

[0131] The electrolyte conducts ions between the positive and negative electrodes. The present invention does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0132] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0133] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0134] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0135] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high or low temperature performance, etc.

[0136] [Isolator]

[0137] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The embodiment of the present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical and mechanical stability can be selected.

[0138] The separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. In the case of a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0139] [Electrode assembly]

[0140] An embodiment of the present application provides an electrode assembly, which includes the electrode piece 1 in any of the above embodiments.

[0141] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process, wherein the positive electrode sheet and the negative electrode sheet can have the structure described in the electrode sheet 1.

[0142] [Battery Cell]

[0143] FIG4 is a schematic diagram of the structure of a battery cell according to an embodiment of the present application. For example, as shown in FIG4 , a battery cell 3 includes a housing 31 , an end cap assembly 32 and an electrode assembly 33 .

[0144] The housing 31 is used to accommodate the electrode assembly 33. The shape of the housing 31 can be determined based on the shape of the electrode assembly 33. The housing 31 can accommodate one or more electrode assemblies. For example, as shown in FIG4 , the housing 31 accommodates four electrode assemblies 33. The housing 31 can be made of metal, such as copper or aluminum.

[0145] The end cap assembly 32 is used to cover the housing 31 to seal the electrode assembly 33. The end cap assembly 32 is connected to the electrode assembly 33, wherein the end cap assembly 32 can be directly connected to the electrode assembly 33 or indirectly connected to the electrode assembly 33.

[0146] As an example, as shown in FIG4 , the electrode assembly 33 is made by winding a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet.

[0147] The end cap assembly 32 is connected to the electrode assembly 33. As an example, the end cap assembly 32 is welded to the electrode lug 33a of the electrode assembly 33 via a current collecting member 34. The electrode lug 33a of the electrode assembly 33 may be formed by stacking the lugs 331 of multiple electrode sheets 1. The current collecting member 34 may be made of metal, such as copper or aluminum.

[0148] The end cap assembly 32 includes an electrode terminal 322. For example, as shown in FIG4 , 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. One current collecting member 34 is used to connect the positive electrode tab to the positive electrode terminal, and the other current collecting member 34 is used to connect the negative electrode tab to the negative electrode terminal.

[0149] In some embodiments, the shape of the battery cell 3 can be cylindrical, square, or any other shape. The battery cell 3 can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc. The battery cell 3 can serve as the smallest structural unit of the battery.

[0150] In some embodiments, the battery cells 3 can be assembled into a battery module. The number of battery cells 3 contained in the battery module can be one or more, and the specific number can be selected according to the application and capacity of the battery module.

[0151] 1 to 5 , the embodiments of the pole piece and the battery cell are described above. The preparation method of the battery cell is described below in conjunction with FIG. 6 . Similar descriptions can be found in the description of the embodiments of the pole piece and the battery cell, which will not be repeated here.

[0152] [Method for preparing battery cells]

[0153] FIG6 is a schematic diagram of a method for preparing a battery cell according to an embodiment of the present application. For example, as shown in FIG6 , the method 200 for preparing a battery cell includes the following steps.

[0154] Step 210: Place the electrode assembly 33 in a container.

[0155] Optionally, the electrode assembly 33 includes a main body 330 and a tab 331 , and the tab 331 protrudes from the main body 330 along a first direction.

[0156] The electrode assembly 33 may be prepared by winding the positive electrode sheet, the separator, and the negative electrode sheet, or by laminating the sheets.

[0157] In step 210, only the electrode assembly 33 can be placed in the container, or the ear portion 33a of the electrode assembly 33 can be welded to the end cover assembly 32 through the current collecting component 34, so that the electrode assembly 33 and the end cover assembly 32 form a component, and then the component is placed in the container.

[0158] The container can be connected to the external environment. For example, the container is connected to the first connecting component, so that gas can be introduced into the container through the first connecting component; for another example, the container can also discharge gas from the container through the second connecting component.

[0159] As an example, the container discharges the gas inside the container through the second connecting component. The second connecting component can be provided 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.

[0160] Step 220: Gaseous silane and water vapor are introduced into the container to obtain an electrode assembly provided with a protective layer 35, wherein the protective layer 35 comprises silicon oxide; the general formula of silane satisfies: R'-Si(OR) n , wherein R' includes an organic or inorganic functional group, R includes an alkyl group, and n is an integer and 2≤n≤4.

[0161] Gaseous silane and water vapor are easily introduced into the container, thereby facilitating the reaction between silane and water molecules.

[0162] n may be 2, 3 or 4; R includes an alkyl group, for example, R may be a methyl group or an ethyl group; R' includes an organic or inorganic functional group, for example, R' may include an amino group or a methyl group. As an example, n is 3.

[0163] In silane, the -(OR) group is a hydrolyzable group, which facilitates the hydrolysis of silane to produce -Si-OH groups. The end surface of the electrode 1 and at least part of the surface of the electrode tab 331 have exposed metal. The -Si-OH groups can combine with the metal and the -Si-OH groups and -Si-OH groups can cross-link on the metal surface to form a protective layer 35. The reaction between silane and water vapor on the metal surface can be roughly divided into the following three steps.

[0164] (1) Silane hydrolysis: -Si-OR + H2O → -Si-OH + ROH;

[0165] (2) Adsorption on metal surface: -Si-OH+Me-OH→Me-O-Si-+H2O, where Me represents metal;

[0166] (3) Cross-linking to form a protective layer: -Si-OH+HO-Si-→-Si-O-Si-+H2O.

[0167] On the one hand, after hydrolysis, silane is adsorbed on the metal surface through the reaction between its -Si-OH group and the Me-OH group on the metal surface. Silane forms Si-O-Me on the metal interface. The covalent bond between Si-O and Me is strong, and the bond between silane and metal is relatively firm. 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.

[0168] Before introducing gaseous silane into the container, the silane may be vaporized outside the container (eg, in an additional storage tank); similarly, before introducing water vapor into the container, the water may be vaporized outside the container.

[0169] By introducing gaseous silane and water vapor into the container, the mixing of silane and water vapor is facilitated, thereby facilitating the reaction.

[0170] In step 220, gaseous silane may be introduced first, and then water vapor; water vapor may be introduced first, and then gaseous silane; or gaseous silane and water vapor may be introduced simultaneously.

[0171] As an example, silane and water vapor are stored in different storage tanks, and valves are provided between the storage tanks and the container. The valve of the storage tank storing silane is first opened to introduce gaseous silane into the container, and then the valve of the storage tank storing water vapor is opened to introduce water vapor into the container.

[0172] After a period of reaction, a protective layer 35 can be formed on the exposed metal surface. In step 220, a protective layer 35 can be formed on the end surface and the exposed metal surface of the tab 331. 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 piece 1; for the electrode assembly 33 formed by lamination, 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 piece 1. For the electrode assembly 33 to be 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.

[0173] In step 230 , the electrode assembly 33 provided with the protective layer 35 is taken out from the container and placed into the housing 31 to obtain a battery cell 3 .

[0174] After the protective layer 35 having a certain thickness is generated, the container can be cooled, and the electrode assembly 33 provided with the protective layer 35 can be taken out. Then, the electrode assembly 33 is placed in the shell 31, and the end cover assembly 32 is connected to the shell 31 to obtain the battery cell 3.

[0175] In the embodiment of the present application, gaseous silane and water vapor react on the exposed metal surfaces of the electrode assembly 33, thereby forming a protective layer 35 on the exposed metal surface of the electrode piece 1. This protective layer 35 comprises silicon oxide. This reduces the risk of short circuits caused by the exposed metal in the electrode piece 1 overlapping with electrodes of opposite polarity, thereby improving the reliability of the battery cell 3. The electrode assembly 33 provided with the protective layer 35 is removed from the container and placed within the housing 31, thereby facilitating the assembly of the battery cell 3. Furthermore, since the housing 31 is not placed within the container, the protective layer 35 is not formed within 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 excellent overall performance.

[0176] In addition, the preparation method of the battery cell of the embodiment of the present application does not use the vacuum treatment of the container, which can reduce the complexity of the operation and is also beneficial to reduce the risk of silane and the like penetrating or adsorbing on the active material layer of the electrode 1, thereby reducing the adverse effects on the electrical properties of the battery cell (such as cycle performance, power, resistance).

[0177] Silane has high reliability and the risk of explosion in the container is very low. By adding silane to the container, the reliability of the battery cell preparation method is higher; and the requirements for the conditions in the container are lower, which is conducive to reducing the complexity of the preparation method.

[0178] 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. Thus, the electrode assembly 33 and the end cap assembly 32 are connected as a whole and then processed, which facilitates the preparation of the protective layer 35 at the connection between the electrode assembly 33 and the end cap assembly 32.

[0179] As an example, in the case where the protective layer 35 is prepared after the pole lug 33a is connected to the end cover assembly 32 through the current collecting member 34, the metal in the area where the pole lug 33a is connected to the current collecting member 34 is not exposed, and the protective layer 35 is not provided in this area.

[0180] In some embodiments, the silane has a boiling point less than or equal to 200°C.

[0181] In this way, silane can be converted into gaseous silane at a temperature of 200°C or below, which is beneficial for saving energy. In addition, the temperature of the container can also be set at a temperature of 200°C or below, which is beneficial for the reaction between silane and water molecules to proceed at a lower temperature.

[0182] In some embodiments, 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, CHOCHCH2-O-(CH2)3-Si(OCH3)3, or CH3-Si(OCH3)3. Using the above-mentioned silane facilitates hydrolysis; and the above-mentioned silane has a suitable boiling point, which facilitates obtaining gaseous silane.

[0183] As an example, the silane is CH3-Si(OCH3)3. This helps reduce steric hindrance and facilitates cross-linking between -Si-OH groups, thereby facilitating the preparation of the protective layer 35 and reducing the temperature or time required for preparing the protective layer 35, thereby reducing the risk of excessive silane penetration into the electrode.

[0184] In some embodiments, the flow rate Q of the gaseous silane and / or water vapor satisfies: 0.1 L / min≤Q≤2 L / min.

[0185] The flow rate of the gaseous silane and water vapor may be the same or different. As an example, the flow rates of the gaseous silane and water vapor are the same.

[0186] Q can be 0.1 L / min, 1 L / min, 2 L / min, or any value within the above range.

[0187] As another example, the flow rate of water vapor is greater than the flow rate of silane. In this way, the excess water vapor is beneficial to the hydrolysis of silane and is also beneficial to reducing the waste of silane.

[0188] By setting Q to meet the above range, gaseous silane and water vapor enter the container at a more appropriate rate, which facilitates the reaction of gaseous silane and water vapor on the metal surface and the formation of the protective layer 35; at the same time, it is also beneficial to reduce the risk of silane penetrating into the exposed metal position of the electrode assembly.

[0189] In some embodiments, the reaction time t1 of the gaseous silane and water vapor satisfies: 4h≤t1≤12h.

[0190] t1 can be 4h, 8h, 10h, 12h or any value within the above range.

[0191] The reaction time t1 may refer to the duration of the passage of gaseous silane and water vapor into the container.

[0192] By setting t1 to meet the above range, a protective layer 35 with a certain thickness can be generated in a shorter time, and the risk of excessive deposition of silane at non-exposed metal locations of the electrode assembly (for example, locations where the active material layer is provided) due to excessive reaction time can be reduced.

[0193] In some embodiments, the temperature T in the container satisfies: 60°C≤T≤150°C; optionally, 80°C≤T≤100°C.

[0194] The temperature T in the container may be 60° C., 80° C., 100° C., 130° C., 140° C., 150° C., or any value within the above range.

[0195] As an example, after the electrode assembly 33 connected to the end cap assembly 32 is placed in a container, the container is heated to a temperature T.

[0196] In the above embodiment, by properly setting the temperature T, the reaction between the gaseous silane and the water vapor on the metal surface is facilitated, and the adverse effect of excessive temperature on the isolation membrane in the electrode assembly 33 can be reduced.

[0197] The preparation conditions of the protective layer 35 are related to the thickness and shear strength of the protective layer 35. For example, the time and temperature for preparing the protective layer 35 are relatively low. In a shorter time and at a lower temperature, a protective layer 35 with a relatively suitable thickness and shear strength can be prepared at the exposed metal position of the electrode. Moreover, in a shorter time and at a lower temperature, the risk of silane penetrating into the non-exposed metal position of the electrode is lower, and the probability of the protective layer 35 being generated at the non-exposed metal position is lower, thereby reducing the impact on the electrical performance of the battery cell (such as cycle performance and power). By reasonably setting the reaction time t1 and temperature T, it is beneficial to prepare a protective layer 35 with a relatively suitable thickness and shear strength, and the battery still has good electrical performance.

[0198] In some embodiments, the pressure P within the container satisfies the following: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows the protective layer 35 to be formed at atmospheric pressure, reducing fabrication complexity. Furthermore, compared to vacuum conditions within the container, this reduces the risk of silane, etc., penetrating into the active material layer of the electrode assembly 33 and other locations.

[0199] 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, so that a relatively stable pressure is maintained in the container.

[0200] Figure 7 is a schematic diagram of an electrode assembly connected to an end cap assembly according to one embodiment of the present application, and Figure 8 is a schematic diagram of a bracket provided with the electrode assembly. In Figure 7 , the end cap assembly 32 is located below the electrode assembly 33 (not shown in Figure 7 ), and the tab 331 of the electrode assembly 33 is connected to the end cap assembly 32 via a current collecting member 34.

[0201] In some embodiments, for example, as shown in Figures 7 and 8, step 210 includes: placing multiple electrode assemblies 33 in a holder 2, with the holder 2 covering the largest surface area of ​​the electrode assemblies 33; and placing the holder 2 in a container. This allows the multiple electrode assemblies 33 to be processed in the container, which improves production efficiency. Furthermore, the holder 2 covering the largest surface area of ​​the electrode assemblies 33 also helps reduce the risk of silane and other substances entering the interior of the electrode assemblies 33.

[0202] FIG9 is a schematic diagram of silane and water vapor deposition according to an embodiment of the present application. As shown in FIG8 and FIG9 , after the gaseous silane and water vapor enter the container, they can be deposited on the surfaces of the electrode assembly 33 and the end cap assembly 32 along a first direction (the direction in which the tab 331 protrudes from the main body 330), such as the direction indicated by arrows CC in FIG8 and FIG9 . By controlling the conditions of the battery cell preparation method, the risk of silane deposition on non-exposed metal portions of the electrode assembly 33 (e.g., portions where the active material layer is disposed) can be reduced, thereby reducing the adverse effects on the cycling performance of the battery cell.

[0203] In some embodiments, the preparation method 200 further includes: performing plasma surface treatment (PLASMA) on the electrode assembly 33 before placing the electrode assembly 33 in the container.

[0204] The electrode assembly 33 may be treated by plasma surface treatment. Specifically, the exposed metal portions of the electrode assembly (e.g., the first end surface 3301a, the second end surface 3301b, and the exposed metal portions of the tab 331) are treated to clean the exposed metal and increase the surface activity of the metal, thereby facilitating the deposition and reaction of silane on the metal surface.

[0205] As an example, plasma surface treatment is performed on the exposed metal portion of the electrode assembly 33 using an argon-oxygen mixture as a cleaning gas; thereafter, the electrode assembly 33 is connected to the end cap assembly 23 .

[0206] As an example, only the positive electrode plate in electrode assembly 33 is plasma surface treated. This helps reduce manufacturing complexity. Furthermore, exposed metal (e.g., aluminum foil) in the positive electrode plate poses a greater risk of short circuits, making treatment of the positive electrode plate even more necessary.

[0207] In the above embodiment, plasma surface treatment can improve the surface activity of the exposed metal in the electrode, facilitate the deposition and reaction of silane on the metal surface, and facilitate the preparation of the protective layer 35; and through the above treatment, it is beneficial to obtain a protective layer 35 with higher shear strength.

[0208] In some embodiments, the power S of the plasma surface treatment satisfies the following: 100 W ≤ S ≤ 200 W; and / or the time t2 of the plasma surface treatment satisfies the following: 50 s ≤ t2 ≤ 100 s; and / or the gas flow rate V1 during the plasma surface treatment satisfies the following: 0.2 L / min ≤ V1 ≤ 0.4 L / min. By selecting treatment parameters within the above ranges, a better plasma treatment effect can be achieved on the electrode assembly.

[0209] 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.

[0210] In some embodiments, the preparation method 200 further includes: before introducing the gaseous silane and water vapor into the container, introducing an inert gas into the container to evacuate the air from the container, thereby reducing the adverse effects of air on the reaction between the silane and water vapor.

[0211] In some embodiments, the time t3 for introducing the inert gas satisfies the following conditions: 5 min ≤ t3 ≤ 30 min; and / or the inert gas introduction flow rate V2 satisfies the following conditions: 0.1 L / min ≤ V2 ≤ 2 L / min. This allows the air in the container to be discharged more quickly and efficiently.

[0212] The gas introduced can be nitrogen, helium, argon and other gases.

[0213] 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.

[0214] The time and flow rate of the inert gas can be set according to actual needs, as long as the air in the container can be discharged.

[0215] 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. The first storage tank, the second storage tank, and the third storage tank are each provided with a flow control valve and connected to the container. The container is used to accommodate an electrode assembly connected to an end cap assembly. The first storage tank is used to store water, the second storage tank is used to store silane, and the third storage tank is used to store nitrogen.

[0216] During the preparation of the protective layer, the inert gas nitrogen in the third storage tank can be first introduced into the container to expel the air in the container; the first storage tank and the second storage tank are heated to obtain water vapor and gaseous silane, and the gaseous silane and water vapor are introduced into the container. The silane and water molecules react on the metal surface to form a protective layer.

[0217] In the preparation method of the embodiment of the present application, by performing plasma surface treatment on the electrode assembly 33 before placing the electrode assembly 33 in the container, it is beneficial for silane to be deposited and reacted on the exposed metal surface of the electrode assembly 33, thereby facilitating the preparation of a protective layer with higher shear strength; by reasonably setting the reaction time t1 and the temperature T, it is beneficial to prepare a protective layer 35 with a relatively suitable thickness and shear strength, and the battery still has good electrical performance; by reacting 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 effects 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 and reduce the risk of silane penetrating into the non-exposed metal position of the electrode assembly; and it is also beneficial to reduce the waste of silane.

[0218] [Battery]

[0219] The present application provides a battery comprising a battery cell 3 according to any of the above embodiments, and / or a battery cell obtained by the preparation method according to any of the above embodiments. FIG10 is a schematic diagram of a battery according to one embodiment of the present application. As shown in FIG10 , the battery 5 may comprise multiple battery cells (not shown).

[0220] The battery cells 3 can be directly assembled into the battery 5 , or they can be assembled into battery modules first, and then multiple battery modules can be assembled into the battery 5 .

[0221] [Electrical devices]

[0222] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0223] Figure 11 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in Figure 11 , the present application provides an electric device 6 including the battery according to the above embodiment.

[0224] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above.

[0225] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0226] [Example of a method for producing a battery cell]

[0227] Example 1

[0228] (1) LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent in a weight ratio of 93:2:5 to form a uniform positive electrode slurry; the positive electrode slurry is coated on a 12μm thick aluminum foil, and after drying, rolling, slitting, die-cutting and other processes, the positive electrode sheet is obtained.

[0229] (2) Plasma treatment was performed on the exposed portion of the aluminum foil of the positive electrode. Argon and oxygen mixture was used as the cleaning gas, the cleaning power S was 100 W, the cleaning time t2 was 100 s, and the gas flow rate V1 was 0.2 L / min.

[0230] (3) The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber latex (SBR) are fully stirred and 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 8 μm thick copper foil, and after drying and other processes, a negative electrode sheet is obtained.

[0231] (4) The positive electrode sheet, the separator (9 μm thick PE film), and the negative electrode sheet are stacked in sequence and then wound to obtain an electrode assembly. The electrode assembly itself has an aluminum positive electrode tab and a copper negative electrode tab. 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 cover assembly, respectively, to obtain a battery component including the electrode assembly and the end cover assembly.

[0232] (5) Place the battery components in a container, heat the container to a temperature T of 80°C, and introduce nitrogen as a protective gas into the container at a flow rate of 1 L / min for 10 minutes to exhaust the air in the container.

[0233] (6) Propyltrimethoxysilane CH3CH2CH2-Si(OCH3)3 was heated to 142°C to vaporize the silane, and gaseous silane was introduced into the container at a flow rate Q of 0.1 L / min; water vapor was introduced into the container at a flow rate Q of 0.1 L / min; and the total reaction time t1 was controlled at 10 h.

[0234] (7) After the reaction time is reached, the introduction of gaseous silane and water vapor is stopped and the container is cooled; thereafter, the components consisting of the electrode assembly and the end cap assembly are removed from the container and welded to the shell to assemble the battery cell.

[0235] Examples 2-6

[0236] The difference between Examples 2-6 and Example 1 is that the temperature T of the container is different.

[0237] Examples 7-9

[0238] The difference between Examples 7-9 and Example 1 is that the reaction time t1 of gaseous silane and water vapor is different.

[0239] Examples 10-12

[0240] 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.

[0241] Example 13

[0242] The difference between Example 13 and Example 1 is that the type of silane is different.

[0243] Example 14

[0244] The difference between Example 14 and Example 1 is that the exposed portion of the aluminum foil of the positive electrode plate is not subjected to PLASMA plasma treatment.

[0245] Comparative Example 1

[0246] 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. The specific conditions are as follows.

[0247] (1) Winding the positive electrode sheet, the negative electrode sheet, and the separator into an electrode assembly, and welding the electrode assembly and the end cap assembly to obtain a battery component including the electrode assembly and the end cap assembly;

[0248] (2) placing the battery components in the cavity, controlling the temperature of the cavity at 70°C, and evacuating the cavity to 50 Pa;

[0249] (3) Gaseous trimethylaluminum was introduced into the chamber until the pressure rose to 50 Pa and maintained for 10 s;

[0250] (4) Evacuate the cavity to 50 Pa;

[0251] (5) Water vapor is introduced into the cavity until the pressure rises to 50 Pa and maintained for 5 seconds;

[0252] (6) Steps (2) to (5) were repeated 500 times to form an aluminum oxide protective layer on the surface of the battery member.

[0253] [Example of battery cell]

[0254] Examples 1-14 of the battery cell can be prepared by examples 1-14 of the method for preparing the battery cell, respectively.

[0255] Table 1 Parameters of Examples and Comparative Examples of the Preparation Method of Battery Cells

[0256] Table 2 Comparative Examples and Examples of Battery Cells

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

[0258] The electrode assembly is 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 is observed using a scanning electron microscope (eg, ZEISS sigma 300).

[0259] [Composition of protective layer]

[0260] Energy-dispersive X-ray spectroscopy (EDS) on a ZEISS sigma 300 was used to analyze the surface of the relevant area. The instrument's data revealed the distribution of each element, and thus the mass percentage of Si.

[0261] As an example, a sample is taken in the direction where the active material layer is provided at the second end surface 3301b (for example, as shown in FIG2 , a sample is taken along the y direction at the second end surface 3301b), and an area of ​​10 mm × 10 mm is cut out to obtain a sample. The sample is placed in a testing device for elemental testing, and the quantitative analysis is performed by microbeam analysis energy spectrum method according to GB-T17359-2012. The proportions of C, Ni, Co, Mn, O, and Si elements (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) can be measured. Among them, to test the Si content at a position 5 mm away from the second end surface 3301b, the ruler in the equipment can be used to locate the point 5 mm away from the second end surface 3301b, and the Si content at this point can be tested.

[0262] It should be noted that, when an insulating layer is provided on the surface of the main body of the electrode piece, it is necessary to avoid the area of ​​the insulating layer during sampling.

[0263] [Shear strength test]

[0264] A tab with a protective layer is used as a test sample. Double-sided tape is used to adhere the sample to a stainless steel plate. The sample's length extends beyond the plate by a certain distance. The tensile testing machine clamps the end of the sample that extends beyond the plate and pulls upward until the sample detaches from the plate. For example, a 15mm-long strip of double-sided tape is used to adhere the sample to the plate. At the end of the test, a 9mm x 9mm area of ​​the sample corresponding to the tape detaches from the plate.

[0265] Shear strength is calculated based on the tensile testing machine's measurement results: Shear strength = shear force / bond area. In the example above, the bond area is 9 mm x 9 mm.

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

[0267] After soaking the electrode assembly in the electrolyte at 60°C for 7 days, the electrode assembly was disassembled and the shear strength of the positive electrode tab with the protective layer was tested again. It should be noted that during the soaking 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 gradual trend (i.e., the shear strength did not decrease or decreased slightly after the 7th day). The shear strength on the 7th day reflects the durability of the protective layer.

[0268] [Vibration test]

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

[0270] The change in silicon content before and after the vibration test can reflect the bonding strength between the protective layer and the electrode. After the vibration test, the silicon content decreased less, indicating that the bonding strength between the protective layer and the electrode was higher.

[0271] [Cycling performance test]

[0272] Battery cells were charged and discharged at 25°C. A single charge / discharge cycle involved the following steps: 1C constant-current charging to 4.25V, followed by constant-voltage charging until the current fell below 0.05C, followed by a 30-minute pause, followed by 1C constant-current discharge to 2.5V, followed by a 30-minute pause.

[0273] After one charge and discharge cycle, the discharge capacity of the battery cell is recorded. This is the first discharge capacity.

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

[0275] In the embodiment of the method for preparing a battery cell, in combination with Examples 1-14 and Comparative Example 1, the preparation method of the embodiment of the present application is simpler, and an electrode assembly provided with a protective layer can be obtained without vacuuming. In addition, compared with the method of performing vacuuming during the preparation of the protective layer, not performing vacuuming is conducive to reducing the risk of excessive infiltration of silane at the non-exposed metal position of the electrode assembly (the non-exposed metal position of the pole piece). Since silicon oxide or silicon element is not conductive, the deposition of silane or the generation of silicon oxide at the non-exposed metal position will affect the conductive performance, thereby affecting the electrical performance of the battery cell (such as the capacity retention rate). Therefore, the pole piece prepared by the method of the embodiment of the present application has a very low Si element content at a position 5 mm away from the end surface, and the battery cell has a high capacity retention rate.

[0276] As shown in Examples 1-14, the protective layer has high shear strength, and the protective layer still has high shear strength after being soaked in electrolyte. The risk of the protective layer falling off is low, and the battery cell can be used in long-term use fields such as energy storage devices; and the end surface can still retain a certain protective layer after being affected by factors such as vibration, thereby providing a certain degree of protection. As shown in Examples 1 and 14, before preparing the protective layer, plasma cleaning the electrode assembly (or positive electrode sheet) is beneficial for preparing a protective layer with higher shear strength.

[0277] As shown in Examples 1-6, as the temperature inside the container increases, it is conducive to promoting the reaction between silane and water molecules, thereby facilitating the formation of a thicker protective layer with greater shear strength. As shown in Examples 5-6, when the temperature T of the container exceeds 130°C, although the thickness of the protective layer increases, due to the high temperature, the reaction between silane and water molecules intensifies, the risk of generating silicon oxide at a position 5mm from the end surface increases, the mass content of Si element exceeds 0.01%, and the improvement in the capacity retention rate of the battery is low. As shown in Examples 1-4, by setting the temperature T of the container within the range of 60°C to 130°C, a protective layer with a suitable thickness can be generated, and the content of Si element at a position 5mm from the end surface is close to 0, and the capacity retention rate of the battery cell is about 90%, thereby achieving both high shear strength and cycle performance. Furthermore, in combination with Examples 1-3, for the same type of silane, setting the temperature T in the container within the range of 80°C to 100°C is conducive to generating a thicker protective layer, and the temperature does not exceed 100°C, which is also conducive to 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 4 hours to 12 hours, a protective layer of relatively suitable thickness can be formed.

[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 between the silane and water vapor. Increasing the flow rate facilitates the formation of a thicker protective layer within the same timeframe. Setting the flow rate between 0.1 L / min and 2 L / min not only facilitates obtaining a protective layer of appropriate thickness, but also reduces the waste of raw materials such as silane that would otherwise be caused by excessively high flow rates.

[0280] As shown in Example 13, the preparation method of the present invention is also applicable to a variety of hydrolyzable silanes. In the present invention, the temperature in the container can be selected according to the different silanes.

[0281] It should be noted that the above embodiments and comparative examples are described using a positive electrode sheet whose current collector is aluminum foil. The embodiments of the present application can also be applied to positive electrode sheets and negative electrode sheets whose current collectors are made of other materials.

[0282] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A pole piece, characterized in that: A protective layer is provided on at least the end surface of the pole piece, wherein the protective layer comprises silicon oxide, and the shear strength G of the protective layer satisfies: G≥110 MPa.

2. The pole piece according to claim 1, characterized in that: 110MPa≤G≤1300MPa.

3. The pole piece according to claim 2, characterized in that: 300MPa≤G≤1000MPa.

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

5. The pole piece according to claim 4, characterized in that: 100nm≤d1≤170nm.

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

7. The pole piece according to claim 6, characterized in that: A<0.01wt%.

8. The pole piece according to any one of claims 1 to 7, characterized in that: The pole piece includes a main body and a pole tab, wherein the pole tab protrudes from the main body along a first direction, and the protective layer is provided on an end surface of the main body along the first direction and at least a portion of the pole tab.

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

10. The pole piece according to any one of claims 1 to 9, characterized in that: The electrode sheet is a positive electrode sheet, and the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide.

11. The pole piece 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: A pole piece as claimed in any one of claims 1 to 11.

13. A battery cell, characterized in that: include: The electrode assembly according to claim 12; A shell is used to accommodate the electrode assembly.

14. A method for preparing a battery cell, characterized in that: include: placing the electrode assembly in a container; Gaseous silane and water vapor are introduced into the container to obtain an electrode assembly provided with a protective layer, wherein the protective layer comprises silicon oxide, and the general formula of the silane satisfies: R'-Si(OR) n , wherein R' comprises an organic or inorganic functional group, R comprises an alkyl group, and n is an integer and 2≤n≤4; The electrode assembly provided with the protective layer is taken out from the container and placed into a shell to obtain the battery cell.

15. The preparation method according to claim 14, characterized in that Placing the electrode assembly in the container comprises: The electrode assembly is connected to an end cap assembly, and the electrode assembly connected with the end cap assembly is placed in the container.

16. The preparation method according to claim 14 or 15, 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 to 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 to 17, characterized in that: The temperature T in the container satisfies: 60°C≤T≤150°C.

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

20. The preparation method according to any one of claims 14 to 19, characterized in that: The reaction time t1 of the gaseous silane and the water vapor satisfies: 4h≤t1≤12h.

21. The preparation method according to any one of claims 14 to 20, characterized in that: The inlet flow rate Q of the gaseous silane and / or the water vapor satisfies the following: 0.1 L / min≤Q≤2 L / min.

22. The preparation method according to any one of claims 14 to 21, characterized in that: The pressure P in the container satisfies: 0.09 MPa≤P≤0.11 MPa.

23. The preparation method according to any one of claims 14 to 22, characterized in that: The preparation method further comprises: Before placing the electrode assembly in the container, the electrode assembly is subjected to 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 during the plasma surface treatment satisfies: 0.2L / min≤V1≤0.4L / min.

25. The preparation method according to any one of claims 14 to 24, characterized in that The preparation method further comprises: Before introducing gaseous silane and water vapor into the container, an inert gas is introduced into the container to exhaust the air in the container.

26. The preparation method according to any one of claims 14 to 25, characterized in that Placing the electrode assembly in the container comprises: placing a plurality of the electrode assemblies in a bracket, wherein the bracket covers the largest surface of the electrode assembly; The stent is placed in the container.

27. The preparation method according to any one of claims 14 to 26, characterized in that The container is in communication with the external environment.

28. A battery, characterized in that: Including 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 device, characterized in that: Comprising a battery according to claim 28.

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