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

Abstract

The application discloses a pole piece, an electrode assembly, a battery monomer and a preparation method thereof, a battery and a power utilization device, and belongs to the technical field of batteries. At least an end surface of the pole piece is provided with a protective layer, and the protective layer comprises silicon oxide; the mass content A of Si elements satisfies A < 0.01 wt% based on the total mass of all elements at a first position of the pole piece, and the first position is a position 5 mm away from the end surface. The technical scheme has the advantages that the reliability and the cycle performance of the battery monomer are improved.

Description

Technical Field

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

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

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

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

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

[0006] In a first aspect, an electrode is provided, wherein at least one end surface of the electrode is provided with a protective layer comprising silicon oxide; and the mass content A of Si element based on the total mass of all elements at a first position of the electrode satisfies: A < 0.01 wt%, and the first position is a position 5 mm away from the end surface.

[0007] In this embodiment, at least the end surface of the electrode is provided with a protective layer, which includes silicon oxide. This protective layer reduces the risk of short circuits caused by the end surface colliding with an electrode of opposite polarity, thus improving the reliability of the battery cell. Based on the total mass of all elements at the first location of the electrode, the mass content A of Si element satisfies: A < 0.01 wt%. Therefore, the first location of the electrode contains almost no Si element, thereby reducing the adverse effects of Si element on the cycle performance of the battery cell. Therefore, the technical solution of this embodiment is beneficial for improving the reliability and cycle performance of the battery cell.

[0008] In one possible implementation, based on the total mass of all elements at the second position of the electrode, the mass content B of the Si element satisfies: B≤0.05wt%, and the second position is a position 3mm away from the end surface.

[0009] In one possible implementation, based on the total mass of all elements at the third position of the electrode, the mass content C of the Si element satisfies: C≤1.2wt%, and the third position is a position 0.5mm away from the end surface.

[0010] In the above technical solution, the Si content gradually increases as the distance between the element and the end surface decreases. In the above technical solution, the Si content at the second and third positions remains relatively small, which can reduce the impact on the cycle performance of the battery cell.

[0011] In one possible implementation, based on the total mass of all elements on the end surface of the electrode, the mass content D of Si element satisfies: 8wt% ≤ D ≤ 35wt%; alternatively, 15wt% ≤ D ≤ 30wt%. Thus, the end surface has a certain mass content of Si element and a certain amount of silicon oxide, thereby reducing the risk of short circuits caused by the electrode's end surface colliding with an electrode of opposite polarity.

[0012] In one possible implementation, the thickness d1 of the protective layer satisfies: 20nm ≤ d1 ≤ 200nm. This ensures the protective layer possesses sufficient shear strength while mitigating other adverse effects caused by excessive thickness.

[0013] In one possible implementation, the thickness d1 of the protective layer satisfies: 80nm ≤ d1 ≤ 170nm. When d1 is greater than or equal to 80nm, the protective layer has a suitable thickness, which can reduce the risk of short circuits; when d1 is less than or equal to 170nm, the protective layer thickness is smaller, which can reduce the adverse effects of excessive protective layer thickness on the performance of the battery cells.

[0014] In one possible implementation, the shear strength G of the protective layer satisfies: 70 MPa ≤ G ≤ 200 MPa. This ensures a strong bond between the protective layer and the electrode, reducing the risk of the protective layer detaching from the electrode; and also helps reduce the time and temperature required to prepare the protective layer. Optionally, 100 MPa ≤ G ≤ 150 MPa. This provides both a suitable bond strength between the protective layer and the electrode, and also helps reduce the adverse effects on the electrical performance of the battery cell caused by preparing a protective layer with high shear strength.

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

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

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

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

[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 At least one of O2. The above-mentioned positive electrode active materials have high nickel content and high specific capacity, which is beneficial for preparing batteries with high energy density.

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

[0021] Thirdly, a battery cell is provided, comprising: the electrode assembly described in the second aspect; and a housing for accommodating the electrode assembly. This battery cell can achieve both high reliability and good cycle performance.

[0022] Fourthly, a method for preparing a battery cell is provided, comprising: placing an electrode assembly in a container; introducing gaseous silane, water vapor, and a pH adjuster into the container to obtain an electrode assembly with a protective layer, wherein the protective layer comprises silicon oxide, and the silane has the general formula: R'-Si(OR) n Wherein, R' includes organic or inorganic functional groups, R includes alkyl groups, n is an integer and 2≤n≤4; the electrode assembly with the protective layer is removed from the container and placed into the housing to obtain the battery cell.

[0023] In this embodiment, gaseous silane and water vapor react on the exposed metal surface of the electrode assembly, thereby forming a protective layer on the exposed metal surface of the electrode assembly. This protective layer includes silicon oxide. This reduces the risk of short circuits caused by the exposed metal of the electrode assembly contacting electrodes of opposite polarity, thus improving the reliability of the battery cell. By introducing a pH adjuster into the container, the reaction between silane and water molecules can be promoted, improving the reaction efficiency and reducing the time the electrode assembly is placed in the container. This reduces the adverse effects of Si element penetration into the active material region on the cycle performance of the battery cell. Removing the electrode assembly with the protective layer from the container and placing it into the housing facilitates the assembly of the battery cell. Furthermore, since the housing is not placed in the container, no protective layer is formed inside the housing, thus reducing the adverse effects of the protective layer on the battery cell. Therefore, the battery cell obtained by this technical solution has good reliability and cycle performance.

[0024] In one possible implementation, the pH adjuster comprises an alkaline gas. The alkaline gas has a low risk of reacting with the positive electrode active material in the electrode assembly, such as residual alkali on the surface of the positive electrode active material, which helps to reduce the adverse effects on battery capacity.

[0025] In one possible implementation, the alkaline gas includes at least one of ammonia, phosphine, methylamine, dimethylamine, trimethylamine, or ethylamine. The aforementioned pH adjuster, as an alkaline gas, possesses suitable alkalinity, which is beneficial for improving the reaction efficiency between silane and water molecules.

[0026] In one possible implementation, the pH adjuster comprises an acidic gas. The acidic gas can promote the reaction between silane and water molecules, which is beneficial for improving the preparation efficiency of the protective layer.

[0027] In one possible implementation, the acidic gas includes at least one of hydrogen fluoride, hydrogen sulfide, hydrogen chloride, or sulfur dioxide. The aforementioned acidic gas possesses suitable acidity, which is beneficial for improving the reaction efficiency between silane and water molecules.

[0028] In one possible implementation, the temperature T of the container satisfies: 45℃ ≤ T ≤ 120℃. When the temperature T is greater than or equal to 45℃, it is convenient to reduce the temperature difference between the gaseous silane in the container. When T is less than or equal to 120℃, it can reduce the adverse effects of excessively high temperatures inside the container on the insulating membrane of the electrode assembly.

[0029] In one possible implementation, 60℃≤T≤100℃. This facilitates further reducing the temperature difference between the gaseous silanes in the container and promotes the reaction between silanes and water molecules.

[0030] In one possible implementation, the silane has a boiling point of less than or equal to 200°C. This facilitates the reaction of the silane and water molecules at a lower temperature within the container.

[0031] In one possible implementation, the silane comprises at least one of (H5C2O)3Si-CH2CH2-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-S4-(CH2)3-Si(OC2H5)3, (H5C2O)3Si-(CH2)3-NH-CO-NH2, CH2OCHCH2-O-(CH2)3-Si(OCH3)3, (CH3)2-Si(OCH3)2, or CH3-Si(OCH3)3; the silane is of the above-mentioned type, which facilitates hydrolysis.

[0032] In one possible implementation, the silane comprises (CH3)2-Si(OCH3)2, which has a low boiling point, facilitating the conversion of the silane into a gaseous state; at the same time, the silane has low steric hindrance, which is beneficial for the formation of silicon oxide.

[0033] In one possible implementation, the flow rates of the gaseous silane (Q1), the water vapor (Q2), and the pH adjuster (Q3) satisfy: Q2 ≥ Q1 > Q3. This facilitates the reaction between water molecules and silane while also saving on the amount of silane used.

[0034] In one possible implementation, the inlet flow rate Q1 of the gaseous silane satisfies: 0.5 L / min ≤ Q1 ≤ 1.5 L / min; and / or, the inlet flow rate Q2 of the water vapor satisfies: 1 L / min ≤ Q2 ≤ 2 L / min; and / or, the inlet flow rate Q3 of the pH adjuster satisfies: 0.1 L / min ≤ Q3 ≤ 1 L / min.

[0035] By setting the flow rate of gaseous silane, water vapor, and pH adjuster, the gaseous silane, water vapor, and pH adjuster enter the container at a suitable rate, which facilitates the reaction of gaseous silane and water vapor on the metal surface and promotes the formation of a protective layer. In addition, it also helps to reduce the risk of silane penetrating into the non-exposed metal parts of the electrode assembly.

[0036] In one possible implementation, the reaction time t1 between the gaseous silane and the water vapor satisfies: 2h ≤ t1 ≤ 8h; alternatively, 4h ≤ t1 ≤ 6h. This allows for the formation of a protective layer in a shorter time, reducing the risk of a protective layer forming on the active material layer of the electrode assembly due to excessively long reaction times, thereby mitigating adverse effects on the cycle performance and other electrical properties of the battery cells.

[0037] In one possible implementation, the pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows for the formation of a protective layer under normal pressure, reducing the complexity of the fabrication process; it also helps reduce the risk of silane infiltrating into the non-exposed metal areas of the electrode assembly, thereby minimizing the impact on the cycle performance of the battery cells.

[0038] In one possible implementation, the container is connected to the external environment. This allows for the maintenance of a relatively constant pressure inside the container.

[0039] In one possible implementation, the preparation method further includes: introducing a carrier gas into a storage tank containing water to obtain the water vapor. This allows water vapor to be obtained via the carrier gas, facilitating its introduction into the container.

[0040] In one possible implementation, the inflow velocity Q4 of the carrier gas satisfies: 0.9 L / min ≤ Q4 ≤ 2.2 L / min. This facilitates the production of water vapor.

[0041] In one possible implementation, placing the electrode assemblies in the container includes: placing a plurality of the electrode assemblies in a support, the support covering the largest surface area of ​​the electrode assemblies; and placing the support containing the plurality of electrode assemblies in the container. This allows multiple electrode assemblies to be processed within the container, improving production efficiency. Furthermore, the support covering the largest surface area of ​​the electrode assemblies helps reduce the risk of silanes or similar substances entering the electrode assemblies.

[0042] In one possible implementation, the preparation method further includes: purging the container with an inert gas before introducing the gaseous silane and water vapor into the container to purge the air inside. This reduces the adverse effects of air on the reaction between the silane and water vapor.

[0043] In one possible implementation, placing the electrode assembly in the container includes: connecting the electrode assembly to the end cap assembly, and placing the electrode assembly connected to the end cap assembly into the container. This allows for the processing of the electrode assembly and end cap assembly as a single unit, which facilitates the fabrication of a protective layer at the connection point between the electrode assembly and the end cap assembly.

[0044] Fifthly, a battery is provided, comprising a battery cell according to the third aspect, and / or a battery cell obtained according to the preparation method of the fourth aspect and any possible implementation thereof.

[0045] In a sixth aspect, an electrical device is provided, comprising the battery described in the fifth aspect. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0047] Figure 1 A schematic diagram of the structure of an electrode sheet before cutting the electrode tab according to an embodiment of this application;

[0048] Figure 2 This is a schematic diagram of the structure of an electrode sheet after the tabs have been cut according to an embodiment of this application;

[0049] Figure 3 for Figure 2 Cross-sectional view along the AA direction;

[0050] Figure 4 for Figure 2 Cross-sectional view along the BB direction;

[0051] Figure 5 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0052] Figure 6 This is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application;

[0053] Figure 7 This is a schematic diagram of an electrode assembly connected to an end cap assembly according to an embodiment of this application;

[0054] Figure 8 A schematic diagram of a support frame with electrode assemblies;

[0055] Figure 9 A schematic diagram of silane and water vapor deposition according to an embodiment of this application;

[0056] Figure 10 This is a schematic diagram of an apparatus for preparing a protective layer according to an embodiment of this application;

[0057] Figure 11 This is a schematic diagram of a battery according to an embodiment of this application;

[0058] Figure 12This is a schematic diagram of an electrical device according to an embodiment of this application. Detailed Implementation

[0059] The embodiments of the electrodes, electrode assemblies, battery cells, their preparation methods, batteries, and electrical devices described herein are disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0060] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0061] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0062] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0063] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0064] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, and reliability. After cutting, the exposed metal of the electrodes in a battery cell poses a risk of short circuits due to contact with electrodes of opposite polarity or other components of the cell. Some methods incorporate protective layers at the exposed metal locations of the electrode assemblies to reduce the risk of short circuits and improve the reliability of the battery cell. However, these methods offer limited improvement to the cycle performance of the battery cell.

[0065] In view of this, this application provides an electrode with a protective layer disposed at least on its end surface. The protective layer comprises silicon oxide, and the mass content of Si element at a certain distance from the end surface is less than 0.01 wt%. This protective layer reduces the risk of short circuits, while the low Si element content at a certain distance from the end surface reduces the adverse effects of Si element on the cycle performance of the battery cell. Therefore, the battery cell of this application has high reliability and cycle performance.

[0066] [Extreme Film]

[0067] Figure 1 This is a schematic diagram of the structure of an electrode sheet before the tabs are cut, according to an embodiment of this application. Figure 2 This is a schematic diagram of the structure of an electrode sheet after the tabs have been cut according to an embodiment of this application. Figure 3 for Figure 2 Cross-sectional view along the AA direction. Figure 4 for Figure 2 Cross-sectional view along the BB direction.

[0068] In one embodiment of this application, for example, in combination with Figures 1 to 4 As shown, at least the end surface of the electrode 1 is provided with a protective layer 35, which includes silicon oxide.

[0069] The end surface of the electrode 1 may include either an opposing end surface along a first direction of the electrode 1 (e.g., the y direction in the figure) or an opposing end surface along a second direction (e.g., the x direction in the figure).

[0070] The surfaces of the two opposite ends along the first direction of the electrode 1 may include a first end surface 3301a and a second end surface 3301b.

[0071] The surfaces of the two opposite ends along the second direction of the electrode 1 may include a third end surface 3302a and a fourth end surface 3302b.

[0072] The end surface of electrode 1 can be a cut surface, after which the metal of the end surface is exposed. For example, combined with Figures 1 to 3 As shown, the end surface of the main body 330 along the first direction may include a first end surface 3301a and a second end surface 3301b. The first end surface 3301a may be a surface formed during the process of cutting the electrode sheet along the cutting line 124 to prepare the electrode tab 331, and the second end surface 3301b may be a surface generated during the process of slitting the electrode sheet 1. Slitting can refer to the process of cutting a large electrode sheet into multiple small electrode sheets 1 by cutting.

[0073] As an example, a protective layer 35 is provided on both the end surface along the first direction and the end surface along the second direction.

[0074] As another example, such as Figures 1 to 4 As shown, a protective layer 35 is provided on the end surface of the electrode 1 in the first direction, and no protective layer 35 is provided on the end surface of the electrode 1 in the second direction.

[0075] As another example, the end surface (first end surface 3301a) of the electrode 1 near the tab along the first direction is provided with a protective layer 35, while the end surface (second end surface 3301b) away from the tab is not provided with a protective layer 35; and the end surface along the second direction of the electrode 1 is not provided with a protective layer 35.

[0076] The protective layer 35 includes silicon oxide, which may have the following structure: -Si-O-Si-. Silicon oxide is not easily swollen during electrolyte immersion and is not easily detached during long-term use of the battery cell 3.

[0077] The protective layer 35 has certain insulation properties, which can reduce the risk of short circuit caused by the overlap of electrodes with opposite polarity on the end surface, and help improve the reliability of the battery cell.

[0078] Based on the total mass of all elements at the first position of electrode 1, the mass content A of Si element satisfies: A < 0.01 wt%, and the first position is a position 5 mm away from the end surface.

[0079] The first position can be a position 5mm away from the end surface in any direction in electrode 1.

[0080] As an example, the first position is a position where the distance between the electrode 1 and the second end surface 3301b is 5 mm along the first direction (y direction in the figure).

[0081] As another example, the first position is a position where the distance between the electrode 1 and the third end surface 3302a is 5 mm along the second direction (x direction in the figure).

[0082] At the first position of electrode 1, multiple elements constituting the material of electrode 1 are included. For example, for a positive electrode, the first position of the positive electrode includes elements constituting the positive current collector, such as Al; elements constituting the positive electrode film layer; and Si elements that may penetrate into the positive electrode film layer. For a negative electrode, the first position of the negative electrode includes elements constituting the negative current collector, such as Cu; elements constituting the negative electrode film layer; and Si elements that may penetrate into the negative electrode film layer.

[0083] During the preparation of protective layer 35, the raw materials for preparing protective layer 35, such as silane and water, are deposited on electrode 1 and react. The mass content of Si element can reflect the degree of silane penetration or adhesion to electrode 1, or it can reflect the content of silicon oxide on electrode 1.

[0084] Silicon oxide or silicon affects the conductivity of the electrodes, thus affecting the electrical performance of the individual battery cells. For example, it affects the capacity retention, power, and resistance of the battery cells.

[0085] When the Si content is less than 0.01 wt%, it can be approximately assumed that the first position does not contain silicon oxide or that silane has not diffused into the first position. Thus, the risk of silicon oxide or silane being present in the non-exposed metal area of ​​electrode 1 is low, resulting in a smaller impact on the electrical performance of the battery cell and helping to reduce the impact on the cycle performance of the battery cell.

[0086] In this embodiment, at least one end surface of the electrode 1 is provided with a protective layer 35, which includes silicon oxide. The protective layer 35 reduces the short-circuit risk of the battery cell and improves its reliability. At the first position of the electrode 1, the mass content A of Si element satisfies A < 0.01 wt%, thus the battery cell exhibits high cycle performance. Therefore, the technical solution of this embodiment is beneficial for improving the reliability and cycle performance of the battery cell.

[0087] In some embodiments, based on the total mass of all elements at the second position of electrode 1, the mass content B of Si element satisfies: B≤0.05wt%, and the second position is a position 3mm away from the end surface.

[0088] In some embodiments, based on the total mass of all elements at the third position of electrode 1, the mass content C of Si element satisfies: C≤1.2wt%, and the third position is a position 0.5mm away from the end surface.

[0089] B can be 0.05wt%, 0.02wt%, 0.01wt%, 0wt%, or any value within the above range, and C can be 1.2wt%, 1.1wt%, 1wt%, 0.5wt%, 0wt%, or any value within the above range.

[0090] The second position can be a position 3 mm from the end surface of electrode 1 in any direction; the third position can be a position 0.5 mm from the end surface of electrode 1 in any direction.

[0091] As an example, the second position is along the first direction, for example... Figure 1 The position in the y-direction, at a distance of 3mm from the second end surface 3301b.

[0092] As an example, the third position is along the first direction, for example... Figure 1 The position in the y-direction, at a distance of 0.5 mm from the second end surface 3301b.

[0093] In the above technical solution, the Si content gradually increases as the distance between the electrode and the end surface decreases. In the above technical solution, the Si content at the second and third positions remains relatively small, reflecting a lower Si content in the unexposed metal areas of electrode 1, thus reducing the impact on the cycle performance of the battery cell.

[0094] In some embodiments, based on the total mass of all elements on the end surface of the electrode, the mass content D of Si element satisfies: 8wt% ≤ D ≤ 35wt%; optionally, 15wt% ≤ D ≤ 30wt%. In this way, the end surface has a certain mass content of Si element and a certain amount of silicon oxide, thereby reducing the risk of short circuit caused by the end surface of the electrode 1 overlapping with an electrode of opposite polarity.

[0095] D can be 8wt%, 10wt%, 15wt%, 20wt%, 30wt%, 35wt%, or any value within the above range.

[0096] In some embodiments, the thickness d1 of the protective layer 35 satisfies: 20nm ≤ d1 ≤ 200nm.

[0097] The thickness d1 of the protective layer 35 can be 190nm, 160nm, 100nm, 50nm, 20nm, or any value within the above range. The thickness d1 of the protective layer 35 can be the average thickness of the protective layer 35. For example, measurements can be taken at multiple locations on the end surface, and the average of the multiple data points can be taken as the thickness at the end surface.

[0098] At different locations, such as at the first end surface 3301a and the second end surface 3301b, the protective layer 35 has the same or substantially the same thickness.

[0099] When d1 is greater than or equal to 20nm, the protective layer 35 has a suitable thickness, which can reduce the risk of short circuit and the protective layer 35 has a certain shear strength, so the risk of falling off is low. When d1 is less than or equal to 200nm, the adverse effects of excessive thickness of the protective layer 35 on the performance of the battery cell 3 can be reduced.

[0100] In some embodiments, the thickness d1 of the protective layer 35 satisfies: 80nm ≤ d1 ≤ 170nm. d1 can be 80nm, 100nm, 120nm, 160nm, 170nm, or any value within the above range.

[0101] When d1 is greater than or equal to 80nm, the protective layer 35 has a suitable thickness, which can reduce the risk of short circuit; when d1 is less than or equal to 170nm, the protective layer 35 has a smaller thickness, which can reduce the adverse effects of excessive thickness of the protective layer 35 on the performance of the battery cell 3.

[0102] In some embodiments, the shear strength G of the protective layer 35 satisfies: 70MPa≤G≤200MPa.

[0103] G can be 70MPa, 80MPa, 85MPa, 90MPa, 96MPa, 100MPa, 120MPa, 150MPa, 170MPa, 200MPa or any value within the above range.

[0104] The shear strength of the protective layer 35 is related to the thickness of the protective layer 35. In the embodiments of this application, the greater the thickness of the protective layer 35, the greater the shear strength of the protective layer 35.

[0105] The shear strength of the protective layer 35 reflects the bonding strength between the protective layer 35 and the electrode 1. The greater the shear strength of the protective layer 35, the stronger the bond between it and the electrode 1, and the lower the risk of the protective layer 35 detaching from the electrode 1. Furthermore, during the long-term use of the battery cell 3, the risk of the protective layer 35 swelling due to electrolyte immersion is lower, and the protective layer 35 is less prone to detachment, which helps improve the reliability of the battery cell 3.

[0106] When the shear strength of the protective layer 35 is greater than or equal to 70 MPa, the risk of the protective layer 35 falling off the electrode 1 is low; when the shear strength of the protective layer 35 is less than or equal to 200 MPa, it is easier to prepare the protective layer 35, which helps to reduce the time required to prepare the protective layer 35 and the temperature required to prepare the protective layer 35.

[0107] The protective layer 35, having shear strength within the aforementioned range, is not easily detached from the electrode 1, thereby giving the battery cell including the electrode 1 a longer service life, and the battery cell can be used in electric vehicles.

[0108] The test method for the shear strength of the protective layer 35 can be found in the test method section below.

[0109] In some embodiments, 100MPa≤G≤150MPa. G can be 100MPa, 115MPa, 130MPa, 135MPa, 150MPa or any value within the above range.

[0110] In this embodiment, 100MPa≤G≤150MPa, the protective layer 35 and the electrode 1 have a suitable bonding strength, and it is also beneficial to reduce the adverse effects on the electrical performance of the battery cell 3 caused by the preparation of the protective layer 35 with high shear strength.

[0111] In some embodiments, the metal on the end surface is bonded to the silicon oxide in the protective layer 35 by chemical bonds. Specifically, the metal and silicon oxide are bonded by covalent bonds.

[0112] As an example, the combination of metal and silicon oxide is represented by the following: Me-Si-O-Si, where Me represents the metal.

[0113] As one example, Me represents aluminum. As another example, Me represents copper.

[0114] The shear strength of the protective layer 35 is related to the connection between the protective layer 35 and the exposed metal of the electrode 1. In this embodiment, the bonding force between the protective layer 35 and the end surface 3301 is strong, and the protective layer 35 is not easy to fall off.

[0115] In some embodiments, the electrode 1 includes a main body 330 and an electrode tab 331. The electrode tab 331 protrudes from the main body 330 along a first direction. A protective layer 35 is provided at least a portion of the end surface 3301 of the main body 330 along the first direction and at least a portion of the electrode tab 331.

[0116] The first direction is the direction in which the tab 331 protrudes from the main body 330, for example, as Figure 2 As shown, the first direction is the y-direction.

[0117] A protective layer 35 is provided at least partially on the tab 331. It is understood that the protective layer 35 may be provided at partial or complete locations of the tab 331. "At least partially on the tab 331" may refer to the location of the exposed metal of the tab 331.

[0118] As an example, such as Figure 2 As shown, the tab 331 may include a first part 3311 and a second part 3312, the first part 3311 is connected to the second part 3312 and the first part 3311 is closer to the main body 330 relative to the second part 3312; the main body 330 includes a first region 3302 and a second region 3303 connected, the second region 3303 is closer to the tab 331 relative to the first region 3302; the first part 3311 of the tab 331 and the second region 3303 of the main body 330 are coated with an insulating material, the second part 3312 of the tab 331 is an exposed aluminum foil, and the first region 3302 of the main body 330 is coated with an active material; the first part 3311 is not provided with a protective layer 35, and the second part 3312 is provided with a protective layer 35.

[0119] As another example, the entire area of ​​the main body 330 is coated with an active material, the entire area of ​​the tab 331 is bare aluminum foil, and the entire area of ​​the tab 331 is provided with a protective layer 35.

[0120] In some embodiments, the first position is a location 5 mm away from the end surface of the main body portion 330 along the first direction. For example, the first position is a location 5 mm away from the second end surface 3301b along the first direction. The Si content at the first position can easily reflect the changes in the electrical performance of the battery cell when silicon is incorporated.

[0121] In some embodiments, the metal in the tab 331 is chemically bonded to the silicon oxide in the protective layer 35. This reduces the risk of a short circuit caused by the tab 331 coming into contact with an electrode of opposite polarity.

[0122] In some embodiments, a protective layer 35 is provided on the end surface of the main body 330 along a second direction, the second direction being perpendicular to the first direction and parallel to the surface where the electrode 1 is located. For example, the second direction is... Figure 1 The x-direction in the middle.

[0123] In this embodiment, a protective layer 35 is provided on the end surface of the main body 330 along the second direction and the end surface along the first direction, which helps to further reduce the risk of short circuit caused by the electrode 1 overlapping with an electrode of opposite polarity.

[0124] In some embodiments, the electrode is a positive electrode, which includes a positive active material comprising a layered transition metal oxide. Batteries prepared using the aforementioned positive active material exhibit higher energy density, thus achieving a balance between high energy density and high reliability.

[0125] Layered transition metal oxides can include ternary materials, lithium cobalt oxide, lithium-rich manganese-based materials, etc.

[0126] As an example, the chemical formula of layered transition metal oxides includes: Li x (Ni a Co b Mn c ) 1-d M d O 2-y N y M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La; N includes at least one of F, S, and P; 0.6 ≤ a < 1; 0 <b<0.4,0<c<0.4,a+b+c=1,0≤d<1,0.2≤x≤1.2,0≤y<2。

[0127] a can be 0.6, 0.7, 0.8, 0.9 or any value within the above range; b can be 0.1, 0.2, 0.3 or any value within the above range; c can be 0.1, 0.2, 0.3 or any value within the above range; d can be 0, 0.1, 0.6, 0.6, 0.8 or any value within the above range; x can be 0.2, 0.5, 1, 1.2 or any value within the above range; and y can be 0, 0.5, 1, 1.5, 2 or any value within the above range.

[0128] When d is greater than 0, the layered transition metal oxide includes the M element, which can result in higher stability; when d is 0, the layered transition metal oxide does not include the M element.

[0129] It is understandable that the position of the M ion in the layered transition metal oxide structure can be the replacement of some of the transition metal sites. For example, in the case of a nickel-cobalt-manganese-based ternary material, the M ion can replace some of the manganese, nickel, or cobalt sites.

[0130] When y = 0, layered transition metal oxides do not contain nitrogen (N). It is understandable that the position of N ions in the layered transition metal oxide structure could be the position where some O ions have been replaced.

[0131] During the charging and discharging process, Li will be extracted and consumed. The molar content of Li will be different when the battery is discharged to different states. The above limitation on x includes the molar content of Li in different charging and discharging states of the battery (usually the battery voltage is between 2-5V).

[0132] In the above technical solution, the positive electrode active material that meets the above chemical formula has a high nickel content and a high specific capacity.

[0133] In some embodiments, layered transition metal oxides include LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.6 Co 0.2 Mn 0.2 At least one of O2. The above-mentioned positive electrode active materials have high specific capacity, which is beneficial for preparing batteries with high energy density.

[0134] Electrode 1 can be either a positive electrode or a negative electrode. As an example, both the positive and negative electrode have the structure described in electrode 1.

[0135] [Positive electrode plate]

[0136] The positive electrode includes a positive current collector and a positive electrode film layer disposed on the positive current collector.

[0137] The positive electrode current collector can be a metal foil or a composite current collector. For example, the positive electrode current collector can be an aluminum foil.

[0138] Composite current collectors may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0139] The positive electrode film includes a positive electrode active material. This positive electrode active material can be any known battery-grade positive electrode active material. For example, it could be lithium iron phosphate, ternary materials, or lithium-rich manganese-based materials.

[0140] The positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0141] The positive electrode film may optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0142] [Negative electrode plate]

[0143] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0144] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. Composite current collectors can be formed by depositing metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0145] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0146] As an example, the negative electrode active material is a carbon material.

[0147] The negative electrode film may optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0148] [Electrolytes]

[0149] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0150] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0151] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0152] Solvents may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0153] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0154] [Isolation Component]

[0155] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0156] The material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0157] [Electrode Assembly]

[0158] This application provides an electrode assembly, which includes the electrode 1 in any of the above embodiments.

[0159] The positive electrode, negative electrode, and separator can be manufactured into an electrode assembly by a winding process or a stacking process, wherein the positive electrode and negative electrode can have the structure described in electrode 1.

[0160] [Battery cell]

[0161] Figure 4 This is a schematic diagram of the structure of a battery cell according to an embodiment of this application. For example, as shown... Figure 4 As shown, the battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33.

[0162] The housing 31 is used to house the electrode assembly 33, and the shape of the housing 31 can be set according to the shape of the electrode assembly 33. The housing 31 can accommodate one or more electrode assemblies. For example, Figure 4 As shown, the housing 31 contains four electrode assemblies 33. The housing 31 can be made of metal, such as copper or aluminum.

[0163] End cap assembly 32 is used to cover housing 31 to seal electrode assembly 33. End cap assembly 32 is connected to electrode assembly 33, wherein end cap assembly 32 can be directly connected to electrode assembly 33 or indirectly connected to electrode assembly 33.

[0164] As an example, such as Figure 4 As shown, the electrode assembly 33 is made by winding a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0165] The end cap assembly 32 is connected to the electrode assembly 33. As an example, the end cap assembly 32 is welded to the tab 33a of the electrode assembly 33 via a current collector 34. The tab 33a in the electrode assembly 33 can be formed by stacking multiple tabs 331 of the electrode plates 1, and the current collector 34 can be made of metal, such as copper or aluminum.

[0166] End cap assembly 32 includes electrode terminals 322, for example, such as Figure 4 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal. A current collector 34 is used to connect the positive electrode tab and the positive electrode terminal, and another current collector 34 is used to connect the negative electrode tab and the negative electrode terminal.

[0167] In some embodiments, the battery cell 3 can be cylindrical, square, or any other arbitrary shape. The battery cell 3 can be a lithium-ion battery, lithium-sulfur battery, sodium-ion battery, magnesium-ion battery, etc. The battery cell 3 can serve as the smallest structural unit of a battery.

[0168] In some embodiments, the battery cells 3 can be assembled into a battery module, and the number of battery cells 3 contained in the battery module can be one or more, the specific number of which can be selected according to the application and capacity of the battery module.

[0169] The above combination Figures 1 to 5The implementation methods of electrode sheets and battery cells have been introduced. The following section combines... Figure 6 The preparation method of the battery cell is introduced. Similar descriptions can be found in the descriptions of the implementation methods of the electrode and the battery cell, and will not be repeated here.

[0170] [Preparation methods for battery cells]

[0171] Figure 6 This is a schematic diagram illustrating a method for preparing a battery cell according to an embodiment of this application. For example, such as... Figure 6 As shown, the method 200 for preparing a single battery cell includes the following steps.

[0172] Step 210: Place the electrode assembly 33 in the container.

[0173] Optionally, the electrode assembly 33 includes a main body 330 and a tab 331, the tab 331 protruding from the main body 330 along a first direction.

[0174] The electrode assembly 33 can be prepared by winding the positive electrode sheet, the separator, and the negative electrode sheet, or by stacking them.

[0175] In step 210, the electrode assembly 33 can be placed in the container alone, or the electrode tab 33a of the electrode assembly 33 can be welded to the end cap assembly 32 through the current collector 34, so that the electrode assembly 33 and the end cap assembly 32 form a component, and then the component is placed in the container.

[0176] The container can be connected to the external environment. For example, the container can be connected to a first connecting part, so that gas can be introduced into the container through the first connecting part; as another example, the container can also discharge gas from the container through a second connecting part.

[0177] As an example, the container discharges gas from inside the container through a second connecting component. The second connecting component may be equipped with special elements so that the gas inside the container can be discharged to the external environment through the second connecting component, but the gas in the external environment will not enter the container through the second connecting component.

[0178] Step 220: Gaseous silane, water vapor, and pH adjuster are introduced into the container to obtain an electrode assembly with a protective layer 35, wherein the protective layer 35 comprises silicon oxide; the general formula of the silane satisfies: R'-Si(OR) n , where R' includes organic or inorganic functional groups, R includes alkyl groups, and n is an integer and 2≤n≤4.

[0179] Gaseous silane and water vapor can be easily introduced into the container, thus facilitating the reaction between silane and water molecules.

[0180] The pH adjuster can be a gas, which facilitates the reaction between silane and water molecules after it enters the container. By introducing the pH adjuster into the container, the reaction between silane and water molecules can be promoted, which helps to improve the reaction efficiency between silane and water molecules. This, in turn, helps to reduce the time that the electrode assembly 33 is placed in the container, thereby reducing the risk of silane seeping into the non-exposed metal parts of the electrode assembly 33 (e.g., the areas of the electrode where active materials are located), and reducing the risk of silicon oxide formation in the non-exposed metal parts of the electrode assembly 33. This, in turn, reduces the adverse effects on the cycle performance of the battery cell.

[0181] n can be 2, 3, or 4; R includes alkyl groups, for example, R can be methyl or ethyl; R' includes organic or inorganic functional groups, for example, R' can include amino or methyl groups. As an example, n is 3.

[0182] In silanes, the -(OR) group is a hydrolyzable group, facilitating the hydrolysis of silanes to generate -Si-OH groups. At least a portion of the end surface 3301 of the main body 330 and the tab 331 have exposed metal. The -Si-OH groups can bond with the metal, and the -Si-OH groups can cross-link on the metal surface to form a protective layer 35. The reaction of silane and water vapor on the metal surface can be roughly divided into the following three steps.

[0183] (1) Silane hydrolysis: -Si-OR + H2O → -Si-OH + ROH;

[0184] (2) Adsorption on metal surface: -Si-OH+Me-OH→Me-O-Si-+H2O, where Me represents metal;

[0185] (3) Cross-linking to form a protective layer: -Si-OH+HO-Si-→-Si-O-Si-+H2O.

[0186] On the one hand, after hydrolysis, silanes are adsorbed onto the metal surface through the reaction of their -Si-OH groups with the Me-OH groups on the metal surface. Silanes form Si-O-Me at the metal interface, and the covalent bond between Si-O and Me is relatively strong, resulting in a relatively firm bond between silanes and the metal. On the other hand, the remaining silane molecules form a three-dimensional network protective layer on the metal surface through the condensation reaction between the -Si-OH groups.

[0187] Before introducing gaseous silane into a container, the silane can be vaporized outside the container (e.g., in an additional storage tank); similarly, before introducing water vapor into a container, the water can be vaporized outside the container.

[0188] By introducing gaseous silane and water vapor into the container, the silane and water vapor can be mixed, thus facilitating the reaction.

[0189] In step 220, gaseous silane can be introduced first, followed by water vapor, and then the pH adjuster; or water vapor can be introduced first, followed by gaseous silane, and then the pH adjuster; or gaseous silane, water vapor, and the pH adjuster can be introduced simultaneously.

[0190] As an example, silane, water vapor, and pH adjuster are stored in separate storage tanks. Valves are installed between the storage tanks and the container. First, the valve of the storage tank containing silane is opened to introduce gaseous silane into the container. Then, the valve of the storage tank containing water vapor is opened to introduce water vapor into the container. Finally, the valve of the storage tank containing pH adjuster is opened to introduce pH adjuster into the container.

[0191] After a reaction period, a protective layer 35 can be formed on the metal surface. In step 220, a protective layer 35 can be generated on the end surface 3301 of the main body 330, the surface of the exposed metal of the tab 331, the surface of the exposed metal of the end cap assembly 32, and the surface of the exposed metal at the connection between the end cap assembly 32 and the electrode assembly 33.

[0192] Step 230: Remove the electrode assembly 33 with the protective layer 35 from the container and place it into the housing 31 to obtain the battery cell 3.

[0193] After generating a protective layer 35 of a certain thickness, the container can be cooled down, and the electrode assembly 33 with the protective layer 35 can be taken out. Then, the electrode assembly 33 is placed into the housing 31, and the end cap assembly 32 is connected to the housing 31 to obtain the battery cell 3.

[0194] In this embodiment, gaseous silane and water vapor react on the exposed metal surface of the electrode assembly 33, thereby forming a protective layer 35 on the exposed metal surface of the electrode assembly 33. The protective layer 35 includes silicon oxide. This reduces the risk of short circuits caused by the exposed metal of the electrode assembly 33 contacting electrodes of opposite polarity, thus improving the reliability of the battery cell 3. By introducing a pH adjuster into the container, the reaction between silane and water molecules can be promoted, which improves the reaction efficiency between silane and water molecules, reduces the time the electrode assembly is placed in the container, and reduces the risk of silicon oxide formation on the non-exposed metal parts of the electrode assembly, thereby reducing the impact on the cycle performance of the battery cell. The electrode assembly 33 with the protective layer 35 is removed from the container and placed into the housing 31, which facilitates the assembly of the battery cell 3. In addition, since the housing 31 is not placed in the container, the protective layer 35 is not generated inside the housing, thus reducing the adverse effects of the protective layer 35 on the battery cell. Therefore, the battery cell 3 obtained by this technical solution has better reliability and cycle performance.

[0195] The method for preparing the battery cell in this embodiment does not involve vacuuming the container. This reduces the complexity of the operation and also helps to reduce the risk of silane or other substances penetrating or adsorbing onto the active material layer of the electrode assembly 33, thereby reducing the adverse effects on the electrical performance (e.g., cycle performance, power, resistance) of the battery cell 3.

[0196] Silanes have high reliability and a very low risk of explosion in sealed containers. By adding silanes into the container, the reliability of the battery cell preparation method is high; moreover, the requirements for the conditions inside the container are low, which helps to reduce the complexity of the preparation method.

[0197] In some embodiments, the electrode assembly 33 is not subjected to plasma surface treatment (PLASMA) prior to step 210. Because the addition of a pH adjuster enhances the reaction efficiency between silane and water molecules, the protective layer 35 can have a certain thickness, and the protective layer 35 has a certain bonding strength with the metal, making it less prone to detachment after immersion in the electrolyte. Furthermore, skipping the plasma surface treatment step helps reduce process complexity and save costs.

[0198] In some embodiments, the pH adjuster includes an acidic or alkaline gas. The acidic or alkaline gas can promote the hydrolysis of silanes, thereby reducing the reaction time between silanes and water molecules. Using an alkaline gas as the pH adjuster allows silanes to hydrolyze in an alkaline atmosphere, which is beneficial for improving the reaction efficiency between silanes and water molecules.

[0199] In some embodiments, the acidic gas may include gases such as HF, H2S, HCl, and SO2.

[0200] In some embodiments, the pH adjuster includes an alkaline gas. The alkaline gas has a relatively small impact on the electrode assembly 33; for example, it does not react with substances in the electrode, thus reducing its influence on the active material. As a possible example, compared to acidic gases, alkaline gases have a lower risk of reacting with residual alkali (e.g., lithium hydroxide, lithium carbonate) on the surface of the ternary material in the positive electrode, thereby reducing the risk of Li from within the ternary material to its surface, reducing the risk of active lithium loss, and minimizing the impact on battery capacity and initial efficiency.

[0201] In some embodiments, the alkaline gas may include at least one of ammonia, phosphine, methylamine, dimethylamine, trimethylamine, or ethylamine. The aforementioned pH adjuster, as an alkaline gas, possesses suitable alkalinity, which is beneficial for improving the reaction efficiency between silane and water molecules.

[0202] As an example, methylamine is chosen as the alkaline gas.

[0203] In some embodiments, the temperature T of the container satisfies: 45℃≤T≤120℃.

[0204] T can be 45℃, 60℃, 80℃, 100℃, 120℃ or any value within the above range.

[0205] The temperature T of the container can refer to the temperature inside the container. The electrode assembly placed inside the container can have the same temperature as the container. As an example, after the electrode assembly 33 connected to the end cap assembly 32 is placed into the container, the container is heated to temperature T.

[0206] The thickness of the protective layer 35 is related to the temperature of the container. The higher the temperature of the container, the more favorable it is for the hydrolysis of silane, and thus the more favorable it is for the formation of a thicker protective layer 35.

[0207] When the temperature T is greater than or equal to 45°C, it helps to reduce the temperature difference between the gaseous silane in the container. When the temperature T is less than or equal to 120°C, it can reduce the adverse effects of excessively high temperature inside the container on the isolation membrane of the electrode assembly.

[0208] In some embodiments, 60°C ≤ T ≤ 100°C. This temperature range is beneficial for further reducing the temperature difference between the container and the gaseous silane, and for further reducing the temperature of the container, thereby mitigating the adverse effects of excessively high temperatures inside the container on the insulating membrane of the electrode assembly.

[0209] Gaseous silanes, water vapor, pH adjusters, and containers can be at the same temperature or at different temperatures.

[0210] In some embodiments, gaseous silane, water vapor, and pH adjuster can be directly introduced into the container, and the temperature inside the container can be adjusted to the temperature at which the silane vaporizes, thereby reducing the temperature difference between the gaseous silane and water vapor, as well as the temperature difference within the container. For example, a silane with a lower vaporization temperature can be selected.

[0211] In some embodiments, silane can be heated to a first temperature T1 and a carrier gas can be introduced into a storage tank containing silane to obtain gaseous silane; water can be heated to a second temperature T2 and a carrier gas can be introduced into a storage tank containing water to obtain water vapor; a mixture of gaseous silane and water vapor containing carrier gas, as well as an alkaline gas, can be introduced into a container to obtain an electrode assembly with a protective layer.

[0212] The carrier gas configuration facilitates the introduction of gaseous silane and water vapor into the container. Understandably, gaseous silane and carrier gas, as well as water vapor and carrier gas, are introduced into the container together.

[0213] In some embodiments, the carrier gas includes at least one of nitrogen, argon, carbon dioxide, and helium; optionally, the carrier gas includes nitrogen. The carrier gas does not react with silanes and water vapor, thus reducing the adverse effects of reactions with silanes and water vapor.

[0214] In some embodiments, R includes a methyl group. When R is methyl, steric hindrance can be reduced, facilitating crosslinking between -Si-OH and -Si-OH, and promoting the formation of silicon oxide; furthermore, when R is methyl, the silane has a lower boiling point, facilitating the conversion of the silane into a gaseous silane.

[0215] In some embodiments, the boiling point of the silane is less than or equal to 200°C.

[0216] This allows silane to be converted into gaseous silane at temperatures of 200°C or below, which helps save energy. Furthermore, the container temperature can be set at 200°C or below, which facilitates the reaction between silane and water molecules at lower temperatures.

[0217] 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, CH2OCHCH2-O-(CH2)3-Si(OCH3)3, (CH3)2-Si(OCH3)2, or CH3-Si(OCH3)3; the silane uses the above substances, which facilitates hydrolysis.

[0218] In some embodiments, the silane includes (CH3)2-Si(OCH3)2, which has a low boiling point, making it easy to convert the silane into a gaseous state; at the same time, the silane has low steric hindrance, which is conducive to the formation of silicon oxide, thereby facilitating the preparation of the protective layer 35, reducing the temperature or time required to prepare the protective layer 35, and thus reducing the risk of excessive silane penetration into the electrode.

[0219] In some embodiments, the flow rates of gaseous silane (Q1), water vapor (Q2), and pH adjuster (Q3) satisfy the following condition: Q2 ≥ Q1 > Q3. This is beneficial for the reaction between water molecules and silane, and also helps to save on the amount of silane used.

[0220] As an example, the inflow rates of gaseous silane and water vapor are the same.

[0221] As another example, the inlet flow rate of water vapor is greater than that of silane.

[0222] The flow rate Q3 of the pH adjuster can refer to the rate at which the pH adjuster is introduced into the container.

[0223] In the case where both carrier gas and water vapor are introduced into the container simultaneously, the water vapor inlet flow rate Q2 refers to the speed at which the mixture of water vapor and carrier gas is introduced into the container. In the case where only water vapor is introduced into the container, the water vapor inlet flow rate Q2 refers to the speed at which water vapor is introduced into the container.

[0224] When both carrier gas and gaseous silane are introduced into the container simultaneously, the gaseous silane inlet flow rate Q1 refers to the speed at which the mixture of gaseous silane and carrier gas is introduced into the container. When only gaseous silane is introduced into the container, the gaseous silane inlet flow rate Q3 refers to the speed at which water vapor is introduced into the container.

[0225] In some embodiments, the inlet flow rate Q1 of gaseous silane satisfies: 0.5 L / min ≤ Q1 ≤ 1.5 L / min; and / or, the inlet flow rate Q2 of water vapor satisfies: 1 L / min ≤ Q2 ≤ 2 L / min; and / or, the inlet flow rate Q3 of pH adjuster satisfies: 0.1 L / min ≤ Q3 ≤ 1 L / min.

[0226] Q1 can be 0.5L / min, 1L / min, 1.5L / min or any value within the above range; Q2 can be 1L / min, 1.5L / min, 2L / min or any value within the above range; Q3 can be 0.1L / min, 0.5L / min, 1L / min or any value within the above range.

[0227] By setting the flow rate of gaseous silane, water vapor, and pH adjuster, the gaseous silane, water vapor, and pH adjuster enter the container at a suitable rate, which facilitates the reaction of gaseous silane and water vapor on the metal surface and promotes the formation of a protective layer. At the same time, it also helps to reduce the risk of silane penetrating into the exposed metal of the electrode assembly.

[0228] In some embodiments, the reaction time t1 between gaseous silane and water vapor satisfies: 2h ≤ t1 ≤ 8h.

[0229] t1 can be 2h, 4h, 6h, 8h or any value within the above range.

[0230] The reaction time t1 can refer to the duration of gaseous silane and water vapor being introduced into the container.

[0231] By setting t1 to meet the above range, a protective layer 35 of a certain thickness can be generated in a shorter time, while reducing the risk of excessive deposition of silane in non-exposed metal locations of the electrode assembly (e.g., locations where active material layers are provided) due to excessively long reaction times.

[0232] In some embodiments, 4h ≤ t1 ≤ 6h. In this way, a protective layer 35 with a suitable thickness can be obtained in a shorter time.

[0233] The preparation conditions of the protective layer 35 are related to its thickness and shear strength. For example, a shorter preparation time and lower temperature allow for the preparation of the protective layer 35 at locations where the exposed metal of the electrode has a suitable thickness and shear strength. Furthermore, a shorter preparation time and lower temperature reduce the risk of silane infiltration into non-exposed metal locations on the electrode, resulting in a lower probability of the protective layer 35 forming at these locations, thus minimizing its impact on the electrical performance of the battery cell (e.g., cycle performance, power). By appropriately setting the reaction time t1 and temperature T, it is beneficial to prepare a protective layer 35 with suitable thickness and shear strength while maintaining good battery electrical performance.

[0234] In some embodiments, the pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa. This allows the protective layer 35 to be generated under normal pressure, reducing the complexity of the fabrication process. Furthermore, compared to a vacuum environment inside the container, this reduces the risk of silane or other substances penetrating into the active material layer of the electrode assembly 33.

[0235] In some embodiments, the container is in communication with the external environment. That is, during the reaction of silane and water molecules, the container is in communication with the external environment, thus maintaining a relatively stable pressure inside the container.

[0236] In some embodiments, the preparation method further includes: introducing a carrier gas into a storage tank containing water to obtain water vapor. This allows water vapor to be obtained via the carrier gas, facilitating its introduction into the container.

[0237] As an example, silane is heated to turn it into gaseous silane, and then the gaseous silane is introduced into a container; a carrier gas is introduced into a storage tank containing water to turn the water into water vapor, and then the water vapor is introduced into a container; a pH adjuster gas is introduced into a container.

[0238] In one possible implementation, the inflow velocity Q4 of the carrier gas satisfies: 0.9 L / min ≤ Q4 ≤ 2.2 L / min. This facilitates the production of water vapor.

[0239] The inflow velocity of the carrier gas, Q4, and the inflow velocity of the water vapor, Q2, can satisfy the condition 0.9Q2≤Q4≤1.1Q2. This is beneficial for introducing an appropriate amount of water vapor into the container and for maintaining the pressure balance within the container.

[0240] As an example, Q4 is the same as Q2.

[0241] Figure 7 This is a schematic diagram of an electrode assembly connected with an end cap assembly according to an embodiment of this application. Figure 8 This is a schematic diagram of a support structure with electrode assemblies. Figure 7 In the middle, the end cap assembly 32 is located below the electrode assembly 33. Figure 7 (Not shown in the image), the tabs 331 of the electrode assembly 33 are connected to the end cap assembly 32 via the current collector 34.

[0242] In some embodiments, such as Figure 7 and Figure 8 As shown, step 210 includes: placing multiple electrode assemblies 33 connected to the end cap assembly 32 in a support 2, the support 2 covering the largest surface area of ​​the electrode assembly 33; and placing the support 2 containing the multiple electrode assemblies 33 in a container. This allows the components formed by connecting multiple electrode assemblies 33 and the end cap assembly 32 to be processed within the container, which improves production efficiency. Furthermore, the support 2 covering the largest surface area of ​​the electrode assembly 33 helps reduce the risk of silanes or other contaminants entering the interior of the electrode assembly 33.

[0243] Figure 9 This is a schematic diagram of silane and water vapor deposition according to an embodiment of this application. (In conjunction with...) Figure 8 and Figure 9 As shown, after gaseous silane and water vapor enter the container, the silane and water vapor can move along the first direction (the direction in which the tab 331 protrudes from the main body 330), for example... Figure 8 and Figure 9 The arrow in the CC direction indicates deposition on the surfaces of electrode assembly 33 and end cap assembly 32. By controlling the conditions of the cell fabrication method, the risk of silane deposition at non-exposed metal locations (e.g., locations where active materials are present) of electrode assembly 33 can be reduced, thereby mitigating the adverse effects on the cycle performance of the cell.

[0244] The battery cell prepared by preparation method 200 has a Si content of less than 0.01 wt% at a position 5 mm away from the end surface 3301 (e.g., the first end surface 3301a and the second end surface 3301b) of the electrode assembly 33 along the CC direction. This value is basically close to 0.

[0245] In some embodiments, the preparation method 200 further includes: purging the container with an inert gas before introducing the gaseous silane and water vapor into the container to purge the air inside the container. This reduces the adverse effects of air on the reaction between the silane and water vapor.

[0246] As an example, the inert gas introduced into the container has a high temperature, so that the container and electrode assembly can be rapidly heated by the high-temperature inert gas.

[0247] In some embodiments, the inert gas introduction time t3 satisfies: 5 min ≤ t3 ≤ 30 min; and / or, the inert gas introduction flow rate V2 satisfies: 0.1 L / min ≤ V2 ≤ 2 L / min. This allows for the rapid and efficient removal of air from the container.

[0248] The gas introduced can be nitrogen, helium, argon, or other gases.

[0249] 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.

[0250] The time and flow rate of the inert gas can be set according to actual needs, as long as the air inside the container is expelled.

[0251] Figure 10 This is a schematic diagram of an apparatus for preparing a protective layer according to an embodiment of this application. For example, such as... Figure 10As shown, device 1 may include a container 100, a first storage tank 101, a second storage tank 102, a third storage tank 103, and a fourth storage tank 104. Each of the first, second, third, and fourth storage tanks is equipped with a flow regulating valve 110 and is connected to the container 100. The container 100 is used to house the electrode assembly 33 connected to the end cap assembly 32. The first storage tank 101 is used to store water, the second storage tank 102 is used to store silane, the third storage tank 103 is used to store pH adjuster, and the fourth storage tank 104 is used to store nitrogen.

[0252] During the preparation of the protective layer, inert nitrogen gas from the fourth storage tank 104 can be introduced into the container 100 to purge the air from the container 100; carrier nitrogen gas from the fourth storage tank 104 can be introduced into the first storage tank 101 to obtain water vapor, and then the mixture of water vapor and nitrogen gas can be introduced into the container 100; for the second storage tank 102, gaseous silane can be obtained, and the gaseous silane can be introduced into the container 100; pH adjuster from the third storage tank 103 can be introduced into the container 100.

[0253] In the preparation method of this application embodiment, by reasonably setting the reaction time t1 and temperature T, it is beneficial to prepare a protective layer 35 with suitable thickness and shear strength, and the battery still has good electrical performance. By carrying out the reaction of silane and water molecules on the metal surface under normal pressure, it is beneficial to reduce the risk of silane penetrating into the non-exposed metal of the electrode assembly 33, thereby reducing the adverse effect on the electrical performance of the battery. By reasonably setting the flow rate of gaseous silane, water vapor, and pH adjuster, it is beneficial to the reaction between silane and water molecules, reducing the risk of silane penetrating into the non-exposed metal of the electrode assembly, and also reducing the waste of silane. By introducing pH adjuster into the container, it is beneficial to promote the reaction between silane and water, which is beneficial to prepare a protective layer 35 of appropriate thickness at a lower temperature and in a shorter time, and the battery has good electrical performance.

[0254] [Battery]

[0255] This application provides a battery, including the battery cell 3 in the above embodiments. Figure 11 This is a schematic diagram of a battery according to an embodiment of this application. Figure 11 As shown, battery 5 may include multiple battery cells (not shown in the figure).

[0256] Battery cells 3 can be directly assembled into battery 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 5.

[0257] [Electrical appliances]

[0258] This application provides an electrical device, including the battery described in the above embodiments.

[0259] Figure 12 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 12 As shown, this application provides an electrical device 6, which includes the battery in the above embodiment.

[0260] Alternatively, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., as is the case in the embodiments of this application.

[0261] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0262] [Examples of methods for preparing battery cells]

[0263] Example 1

[0264] (1) The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 93:2:5 to form a uniform positive electrode slurry. The positive electrode slurry is coated onto a 12μm thick aluminum foil, and after drying, rolling, slitting, and die-cutting, a positive electrode sheet is obtained.

[0265] (2) The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber emulsion (SBR) are thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry; the negative electrode slurry is coated on an 8μm thick copper foil, and after drying and other processes, a negative electrode sheet is obtained.

[0266] (3) The positive electrode, the separator (9μm thick PE film) and the negative electrode are stacked in sequence and then wound to obtain the electrode assembly. The electrode assembly itself has aluminum positive electrode tabs and copper negative electrode tabs. The positive and negative electrode tabs are welded to the aluminum positive electrode adapter and the copper negative electrode adapter respectively. Then the positive and negative electrode adapters are welded to the positive and negative electrode posts of the end cap assembly respectively to obtain the battery component including the electrode assembly and the end cap assembly.

[0267] (4) Place the above battery components in a container, heat the container to temperature T, which is 82°C, and simultaneously introduce nitrogen gas into the container as a protective gas at a flow rate of 0.01 L / min for 30 min to purge the air from the container.

[0268] (5) Heat silane (CH3)2-Si(OCH3)2 to 82°C (this temperature is close to the boiling point of the silane) to obtain gaseous silane; introduce gaseous silane into the container at a flow rate of Q1.

[0269] (6) Nitrogen gas is introduced into the storage tank containing water to obtain water vapor; a mixture of water vapor and nitrogen gas is introduced into the container at a flow rate of Q2, wherein the flow rate of nitrogen gas introduced into the storage tank containing water is approximately 0.9 to 1.1Q2.

[0270] (7) Introduce a pH adjuster into the container. The pH adjuster is methylamine gas, and the introduce flow rate is Q3. The total reaction time t1 is controlled at 6h.

[0271] (8) After the reaction time is reached, stop the introduction of gaseous silane and water vapor and cool the container; then, remove the components consisting of the electrode assembly and end cap assembly from the container and weld them to the shell to assemble the battery cell.

[0272] Examples 2-4

[0273] The difference between Examples 2-4 and Example 1 is that the types of pH adjusters are different.

[0274] Examples 5-8

[0275] The difference between Examples 5-8 and Example 1 is that the container temperature T is different.

[0276] Examples 9-11

[0277] The difference between Examples 9-11 and Example 1 is that the flow rates Q of gaseous silane, water vapor, and pH adjuster introduced into the container are different.

[0278] Examples 12-13

[0279] The difference between Examples 12-13 and Example 1 is that the flow rate of the pH adjuster into the container is different.

[0280] Examples 14-16

[0281] The difference between Examples 14-16 and Example 1 is that the reaction time is different.

[0282] Examples 17-18

[0283] The difference between Examples 17-18 and Example 1 is that the types of silanes are different.

[0284] Comparative Example 1

[0285] The difference between Comparative Example 1 and Example 1 is that no pH adjuster was introduced into the container.

[0286] [Example of a single battery cell]

[0287] Examples 1-18 of the battery cell can be prepared by methods for preparing battery cells, and Comparative Example 1 of the battery cell can be obtained by methods for preparing battery cells.

[0288] Table 1. Parameters of Examples and Comparative Examples of Battery Cell Preparation Methods

[0289]

[0290] Table 2 Comparative Examples and Embodiments of Individual Battery Cells

[0291]

[0292] Table 3. Experimental results of the examples and comparative examples.

[0293]

[0294]

[0295] It should be noted that in Table 2, " / " indicates that the corresponding tests were not performed. Specifically, in Examples 5-6, 9, 12, and 14-15, the shear strength test and the Si content test of the end surface after electrolyte immersion were not performed.

[0296] [Testing the protective layer]

[0297] (1) Testing the thickness of the protective layer

[0298] The electrode assembly was disassembled, and the thickness of the protective layer at the first end surface 3301a, the second end surface 3301b, and the tab 331 of the positive electrode were observed using a scanning electron microscope (e.g., ZEISS sigma 300).

[0299] (2) Testing of Si element in the protective layer at different locations of the electrode assembly

[0300] Elemental analysis of the relevant surface region was performed using energy-dispersive X-ray spectroscopy (EDS) on the ZEISS sigma 300 instrument to determine the Si content in that region. Based on the instrument data, the distribution of each element was obtained, thus determining the mass percentage of Si.

[0301] The electrode assembly was immersed in electrolyte for 7 days at 60℃, and the Si content on the end surface was measured. The change in Si content on the end surface before and after electrolyte immersion can reflect the bonding strength between the protective layer and the current collector of the electrode.

[0302] As an example, the Si content is tested using the following method: A sample is taken from the second end surface 3301b in the direction where the active material layer is disposed (e.g., combined with...). Figure 2 As shown, a sample is taken along the y-direction at the second end surface 3301b, and a 10mm × 10mm area is cut out to obtain the sample. The sample is placed in the testing equipment for elemental analysis. Referring to GB-T17359-2012 microbeam analysis energy dispersive spectroscopy for quantitative analysis, the proportions of C, Ni, Co, Mn, O, and Si can be measured (when the active material in the electrode is a ternary material), or the proportions of C, Fe, O, and Si (when the active material in the electrode is lithium iron phosphate). Specifically, to test the Si content at a position 5mm from the second end surface 3301b, the scale in the equipment can be used to locate the point 5mm from the second end surface 3301b, and the Si content at that point can be measured. Similarly, to test the Si content at positions 3mm and 0.5mm from the second end surface 3301b, the scale in the equipment can be used to locate the points 3mm and 0.5mm from the second end surface 3301b, and the Si content at those points can be measured.

[0303] It should be noted that when an insulating layer is provided on the surface of the main body of the electrode, sampling should be performed in areas that avoid the insulating layer.

[0304] (3) Short circuit test of batteries with protective layers

[0305] Different locations of the electrode assembly with the protective layer were connected to the anode of a fully charged battery, and the probability of short circuit (or fire) was recorded. Specifically, the electrode assembly with the protective layer was fabricated into a battery and fully charged to 100% SOC. After full charging, the battery was disassembled, and the location with the protective layer was placed in direct contact with the negative electrode active material area, and the occurrence of short circuit (or fire) was recorded. Full charging refers to charging the battery to 100% SOC using a specific current; for example, charging a lithium iron phosphate battery to 3.65V and a ternary lithium battery to 4.3V.

[0306] [Shear strength test]

[0307] A tab with a protective layer is used as the test sample. The test sample is adhered to a stainless steel plate using double-sided tape, with the length of the test sample extending beyond the stainless steel plate by a certain distance. A tensile testing machine clamps the end of the test sample extending beyond the stainless steel plate and pulls it upwards until the test sample detaches from the stainless steel plate. As an example, the test sample is adhered to the stainless steel plate using 15mm long double-sided tape. At the end of the test, the area of ​​the test sample corresponding to the 9mm × 9mm area of ​​the double-sided tape detaches from the stainless steel plate.

[0308] The shear strength is calculated based on the tensile testing results: Shear strength = Shear force / Bonded area. In the example above, the bonded area is 9mm × 9mm.

[0309] It should be noted that in this embodiment, the bonding strength between the protective layer and the electrode assembly is relatively large. Therefore, the test is conducted on the strength of a specific area of ​​the sample being tested when it is separated from the stainless steel plate (i.e., the strength of the entire 9mm×9mm area being separated from the stainless steel plate), rather than the strength of any area of ​​the sample being tested when it is separated from the stainless steel plate (i.e., not the strength of any position within the 15mm length being separated from the stainless steel plate).

[0310] [Performance Testing of Individual Battery Cells]

[0311] The battery cells were charged and discharged at 25°C. One charge-discharge cycle was as follows: constant current charging at 1C to 4.25V, then constant voltage charging continued until the charging current was less than 0.05C and then stopped; paused for 30 minutes; constant current discharging at 1C to 2.5V; paused for 30 minutes.

[0312] After one charge-discharge cycle, the discharge capacity of the battery cell is recorded; this is the initial discharge capacity.

[0313] After 500 charge-discharge cycles, the discharge capacity after 500 cycles is recorded. The capacity retention rate after 500 cycles = discharge capacity after 500 cycles / initial discharge capacity.

[0314] In the embodiments of the battery cell preparation method, in conjunction with Examples 1-18, the preparation method of this application is simpler, and an electrode assembly with a protective layer can be obtained without vacuuming. Furthermore, compared to methods that involve vacuuming during the preparation of the protective layer, not performing vacuuming helps reduce the risk of excessive silane penetration into the non-exposed metal areas of the electrode assembly (the non-exposed metal areas of the electrode sheet). Since silicon oxide or silicon is non-conductive, the deposition of silane or the formation of silicon oxide at non-exposed metal areas will affect conductivity, thereby affecting the electrical performance of the battery cell (e.g., capacity retention). Therefore, the electrode sheet prepared by the method of this application has a very low Si content at a position 5 mm from the end surface, and the battery cell has a high capacity retention rate.

[0315] As shown in Examples 1-18, the Si content gradually increases as the distance from the end surface decreases. This is related to the direction in which the reactants are introduced into the container during the preparation of the protective layer (which can be combined with...). Figure 8 as well as Figure 9 (See the schematic diagram and the description above); and after immersing the electrode assembly for a certain period of time, the end surface of the electrode was tested again. The end surface still retained a certain amount of Si elements, which reflects that the protective layer is not easy to fall off from the electrode.

[0316] In conjunction with Examples 1-18 and Comparative Example 1, the embodiments of this application improve the reaction efficiency of silane and water molecules by adding a pH adjuster, generate a protective layer in a shorter time, and further reduce the risk of silicon oxide or silicon elements in non-exposed metal locations of the electrode assembly.

[0317] In Examples 1-18, no short circuit or fire occurred when the electrode with the protective layer was connected to the electrode with the opposite polarity. Therefore, the protective layer can reduce the risk of short circuit in the battery cell. Furthermore, the battery cells of Examples 1-3 and Examples 5-18 have a capacity retention rate of about 90% after 500 cycles. Therefore, the battery cells of the present application have high reliability and high cycle performance.

[0318] As shown in Examples 1-4, both alkaline and acidic gases can be used as pH adjusters to improve reaction efficiency. As shown in Examples 1-3, compared to the acidic gas used as a pH adjuster in Example 4, the battery cells prepared using an alkaline gas as the pH adjuster have higher capacity and a higher capacity retention rate. In Examples 1-3, the capacity retention rate is approximately 90%; in Example 4, the capacity retention rate is approximately 70.5%.

[0319] As shown in Examples 5-8, increasing the temperature inside the container promotes the hydrolysis of silane, thereby facilitating the formation of a thicker protective layer within the same time frame. Furthermore, setting the container temperature within the range of 60°C to 100°C or 80°C to 100°C helps obtain a protective layer of suitable thickness without causing the temperature inside the container to become excessively high.

[0320] As shown in Examples 9-11, increasing the flow rate of gaseous silane, water vapor, and pH adjuster into the container helps to obtain a thicker protective layer within the same time frame. As shown in Examples 10-11, a flow rate of water vapor greater than that of gaseous silane facilitates the reaction and reduces silane waste. As shown in Examples 12-13, setting the pH adjustment flow rate within the range of 0.1 L / min to 1 L / min reduces pH adjuster waste and promotes the reaction between silane and water molecules.

[0321] As shown in Examples 14-16 and Example 1, a protective layer of appropriate thickness can be generated within 2h to 8h, and the preparation method of this application has high efficiency. Furthermore, as shown in Examples 1, 15 and 16, by setting the reaction time to 4h to 6h, a protective layer of suitable thickness can be prepared in a shorter time, which has high reaction efficiency.

[0322] As shown in Examples 17-18, the preparation method of this application is applicable to a variety of silanes; further, as shown in Example 1, the selection of silanes with methyl R groups is beneficial for obtaining a thicker protective layer at a lower temperature.

[0323] It should be noted that the above embodiments and comparative examples use aluminum foil as the current collector for the positive electrode sheet. The embodiments of this application can also be applied to positive electrode sheets and negative electrode sheets with current collectors made of other materials.

[0324] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode sheet, characterized in that, The electrode includes a main body and an electrode tab. The electrode tab protrudes from the main body in a first direction. A protective layer is provided on the end surface of the main body in the first direction. The protective layer includes silicon oxide. The electrode is a positive electrode, and the main body of the positive electrode is coated with a positive active material, which includes a layered transition metal oxide. Based on the total mass of all elements at the first position of the positive electrode sheet, the mass content A of Si element satisfies: A < 0.01 wt%, and the first position is a position 5 mm away from the end surface.

2. The electrode sheet according to claim 1, characterized in that, Based on the total mass of all elements at the second position of the electrode, the mass content B of Si element satisfies: B≤0.05wt%, and the second position is a position 3mm away from the end surface.

3. The electrode sheet according to claim 1, characterized in that, Based on the total mass of all elements at the third position of the electrode, the mass content C of Si element satisfies: C≤1.2wt%, and the third position is a position 0.5mm away from the end surface.

4. The electrode sheet according to any one of claims 1-3, characterized in that, Based on the total mass of all elements on the end surface of the electrode, the mass content D of Si element satisfies: 8wt%≤D≤35wt%.

5. The electrode sheet according to claim 4, characterized in that, 15wt%≤D≤30wt%.

6. The electrode sheet according to any one of claims 1-3, characterized in that, The thickness d1 of the protective layer satisfies: 20nm≤d1≤200nm.

7. The electrode sheet according to claim 6, characterized in that, 80nm≤d1≤170nm.

8. The electrode sheet according to any one of claims 1-3, characterized in that, The shear strength G of the protective layer satisfies: 70MPa≤G≤200MPa.

9. The electrode sheet according to claim 8, characterized in that, 100MPa≤G≤150MPa.

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

11. The electrode according to claim 10, characterized in that, The protective layer is provided on the end surface of the main body along the second direction, which is perpendicular to the first direction and parallel to the surface where the electrode is located.

12. The electrode sheet according to claim 11, 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.

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

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

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

16. The preparation method according to claim 15, characterized in that, The pH adjuster includes an alkaline gas.

17. The preparation method according to claim 16, characterized in that, The alkaline gas includes at least one of ammonia, phosphine, methylamine, dimethylamine, trimethylamine, or ethylamine.

18. The preparation method according to claim 15, characterized in that, The pH adjuster includes an acidic gas.

19. The preparation method according to claim 18, characterized in that, The acidic gas includes at least one of hydrogen fluoride, hydrogen sulfide, hydrogen chloride, or sulfur dioxide.

20. The preparation method according to any one of claims 15-19, characterized in that, The temperature T of the container satisfies: 45℃≤T≤120℃.

21. The preparation method according to claim 20, characterized in that, The temperature T of the container satisfies: 60℃≤T≤100℃.

22. The preparation method according to any one of claims 15-19, characterized in that, The boiling point of the silane is less than or equal to 200°C.

23. The preparation method according to any one of claims 15-19, 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, (CH3)2-Si(OCH3)2, or CH3-Si(OCH3)3.

24. The preparation method according to claim 23, characterized in that, The silane includes (CH3)2-Si(OCH3)2.

25. The preparation method according to any one of claims 15-19, characterized in that, The flow rates of the gaseous silane (Q1), the water vapor (Q2), and the pH adjuster (Q3) satisfy the following condition: Q2 ≥ Q1 > Q3.

26. The preparation method according to any one of claims 15-19, characterized in that, The flow rate Q1 of the gaseous silane satisfies: 0.5 L / min ≤ Q1 ≤ 1.5 L / min; and / or the flow rate Q2 of the water vapor satisfies: 1 L / min ≤ Q2 ≤ 2 L / min; and / or the flow rate Q3 of the pH adjuster satisfies: 0.1 L / min ≤ Q3 ≤ 1 L / min.

27. The preparation method according to any one of claims 15-19, characterized in that, The reaction time t1 between the gaseous silane and the water vapor satisfies: 2h ≤ t1 ≤ 8h.

28. The preparation method according to claim 27, characterized in that, 4h≤t1≤6h.

29. The preparation method according to any one of claims 15-19, characterized in that, The pressure P inside the container satisfies: 0.09 MPa ≤ P ≤ 0.11 MPa.

30. The preparation method according to any one of claims 15-19, characterized in that, The container is connected to the external environment.

31. The preparation method according to any one of claims 15-19, characterized in that, The preparation method further includes: Carrier gas is introduced into a storage tank containing water to obtain the water vapor.

32. The preparation method according to claim 31, characterized in that, The inlet flow rate Q4 of the carrier gas satisfies: 0.9L / min≤Q4≤2.2L / min.

33. The preparation method according to any one of claims 15-19, characterized in that, The step of placing the electrode assembly in the container includes: Multiple electrode assemblies are placed in a support, the support covering the largest surface area of ​​the electrode assemblies; A support containing multiple of the electrode assemblies is placed in the container.

34. The preparation method according to any one of claims 15-19, characterized in that, The preparation method further includes: Before introducing gaseous silane, water vapor, and pH adjuster into the container, an inert gas is introduced into the container to purge the air inside.

35. The preparation method according to any one of claims 15-19, characterized in that, The step of placing the electrode assembly in the container includes: The electrode assembly is connected to the end cap assembly, and the electrode assembly with the end cap assembly connected is placed in the container.

36. A battery, characterized in that, Includes the battery cell as described in claim 14; and / or, the battery cell obtained by the preparation method according to any one of claims 15-35.

37. An electrical device, characterized in that, Includes the battery according to claim 36.

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