Secondary batteries, battery modules, battery packs, and power consumption devices

Abstract

The present invention provides a secondary battery, a battery module, a battery pack, and a power consumption device. The secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, the positive electrode sheet includes a positive electrode active material, the negative electrode sheet includes a negative electrode active material, the separator is provided between the positive electrode sheet and the negative electrode sheet, the electrolyte includes a first organic solvent and a film-forming additive, the film-forming additive is arranged to form an interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, and the porosity of the separator is ε%, the mass percentage content of the film-forming additive relative to the total mass of the electrolyte is b%, and the viscosity value of the electrolyte at 25°C is c (mPa·s), the secondary battery satisfies 4≦(b*ε) / c≦240. The present invention can improve the rapid charge / discharge performance and cycle life of the secondary battery. Figure 1

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more particularly to secondary batteries, battery modules, battery packs, and power consumption devices. [Background technology]

[0002] Because rechargeable batteries have characteristics such as high capacity and long lifespan, they are widely used in electronic devices such as mobile phones, laptops, electric scooters, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools.

[0003] As the range of battery applications expands, the demands on the performance of secondary batteries become increasingly stringent. For example, they are required to have excellent rapid charge / discharge performance and cycle life. Therefore, improving the rapid charge / discharge performance and cycle life of secondary batteries is an issue that needs to be addressed urgently. [Overview of the project]

[0004] This application has been made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, a battery module, a battery pack, and a power consumption device.

[0005] A first aspect of the present invention provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet contains a positive electrode active material, the negative electrode sheet contains a negative electrode active material, the separator is provided between the positive electrode sheet and the negative electrode sheet, the electrolyte comprises a first organic solvent and a film-forming additive, the film-forming additive is arranged to form an interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, the porosity of the separator is ε%, the mass percentage content of the film-forming additive relative to the total mass of the electrolyte is b%, and the viscosity value of the electrolyte at 25°C is c (mPa·s), the secondary battery satisfies 4≦(b*ε) / c≦240, and optionally satisfies 4≦(b*ε) / c≦180.

[0006] As a result, in this invention, by adjusting the porosity of the separator, the viscosity value of the electrolyte, and the film-forming additive to satisfy the above ranges, and comprehensively adjusting the migration speed of lithium ions in solid-phase and liquid-phase mass transfer, the average migration speed of lithium ions can be improved, thereby improving the rapid charging capability of the secondary battery. Furthermore, the film-forming additive can not only adjust the viscosity of the electrolyte to further adjust the migration speed of lithium ions in the liquid phase, but can also form a protective layer on the surface of the active material, passivating the surface of the active material, reducing the risk of side reactions occurring between the surface of the active material and the electrolyte, improving the structural stability of the active material, and improving the cycle life of the secondary battery. Here, film-forming additives, especially lithium salt-based additives, have a relatively small impedance in the solid electrolyte interface film formed on the surface of the negative electrode active material, which is advantageous for lithium ion insertion and removal.

[0007] In any embodiment, the secondary battery further satisfies at least one of conditions (1) to (3): (1) 25 ≤ ε ≤ 55, and optionally 30 ≤ ε ≤ 50; (2) 0.1 ≤ b ≤ 8, and optionally 0.1 ≤ b ≤ 6; (3) 1 ≤ c ≤ 6, and optionally 2 ≤ c ≤ 5.

[0008] Thus, when the porosity of the separator of the present application is within the above range, the porosity of the separator is not too small, its liquid permeability is good, its lithium ion permeation ability is strong, and it is advantageous for lithium ions to move through the separator to the adjacent active material, and the rapid charging ability of the secondary battery can be further improved. When the mass percentage content of the film-forming additive is within the above range, the film-forming additive can undergo a film-forming reaction with the active material to form a dense and uniform film layer. Thereby, while providing good protection for the active material, the film-forming additive, such as a lithium salt-based additive, can form a SEI film with a small film-forming impedance, and both the lifespan and power can be achieved. When the viscosity value of the electrolytic solution is within the above range, the viscosity of the electrolytic solution is not too high, its ionic conductivity is relatively high, which is advantageous for improving the ion transmission speed, and the rapid charging ability of the secondary battery can be improved. Also, when the viscosity of the electrolytic solution is within the above range, the compatibility between the electrolytic solution and the positive and negative electrode sheets is relatively good, and side reactions with the active material in the positive and negative electrode sheets are unlikely to occur, so the cycle stability of the secondary battery can be improved.

[0009] In any embodiment, when the mass percentage content of the first organic solvent with respect to the total mass of the electrolytic solution is a%, the secondary battery further satisfies 2 ≦ c + 2*a% ≦ 8.

[0010] Thereby, in the present application, by adjusting the mass percentage content of the first organic solvent, it is possible to adjust the viscosity of the electrolytic solution within an appropriate range, and form a stable interfacial film during the film-forming process, and completely cover the surface of the active material.

[0011] In any embodiment, 60 ≦ a ≦ 90, and optionally, 65 ≦ a ≦ 85.

[0012] In any embodiment, the first organic solvent includes one or more of a linear carbonate solvent, a carboxylic acid ester solvent, and a nitrile solvent. Optionally, the linear carbonate solvent includes one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl propyl carbonate (MPC). Optionally, the carboxylic acid ester solvent includes one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), methyl formate (MF), ethyl butyrate (EB), butyl acetate (BA), methyl propionate (MP), methyl butyrate (MB), propyl butyrate (PB), and butyl butyrate (BB). Optionally, the nitrile solvent includes one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN).

[0013] Thereby, since the viscosity of the solvent of the present application is low, the viscosity range of the entire electrolytic solution can be adjusted within an appropriate range. Further, when the first organic solvent includes two or more types, the viscosity and ionic conductivity of the electrolytic solution can be synergistically adjusted, and since a plurality of types of solvents can participate in the film formation reaction, the film layer structure includes a plurality of types of components, and the stability of the interface film can be improved.

[0014] In any embodiment, the additive for film formation is a negative electrode film formation additive arranged to form an interface film on the surface of the negative electrode active material, where the mass percentage content of the negative electrode film formation additive with respect to the total mass of the electrolytic solution is b1%, and a positive electrode film formation additive arranged to form an interface film on the surface of the positive electrode active material, where the mass percentage content of the positive electrode film formation additive with respect to the total mass of the electrolytic solution is b2%. The secondary battery satisfies 1 ≤ b2 / b1 ≤ 60, and optionally satisfies 1 ≤ b2 / b1 ≤ 40.

[0015] As a result, in this invention, by adjusting the content of the negative electrode film-forming additive and the positive electrode film-forming additive to satisfy the above formula, the electrolyte can form an SEI film on the surface of the negative electrode active material and a CEI film on the surface of the positive electrode active material. Furthermore, the interfacial impedance of the two types of film layers is relatively low, the kinetic activity is good, and the charge transfer impedance in the secondary battery is small, which is advantageous for rapid lithium ion transfer and can improve the rapid charging performance of the secondary battery.

[0016] In any embodiment, 0.01 ≤ b1 ≤ 1.5 and / or 0.1 ≤ b2 ≤ 7. When the film-forming additive is within the above range, it is possible to form a dense and stable interfacial film on the surface of the active material, thereby adequately protecting the active material, improving the structural stability of the active material, and ensuring the cycle stability of the secondary battery.

[0017] In any embodiment, the additive for forming the negative electrode film includes, selectively, one or more of the boron-containing lithium salt, phosphorus-containing lithium salt, and sulfur-containing lithium salt; the boron-containing lithium salt includes, selectively, one or more of the lithium tetrafluoroborate LiBF4, lithium borate LiBOB, and lithium difluorooxalate LiDFOB; the phosphorus-containing lithium salt includes, selectively, one or more of the lithium difluorophosphate LiPO2F2, lithium fluorophosphate Li2PO3F, and lithium phosphate Li3PO4; and the sulfur-containing lithium salt includes, selectively, one or more of the lithium fluorosulfonate LiFSO3, lithium sulfate Li2SO4, and lithium sulfamate LiSO3NH2.

[0018] As a result, the boron-containing lithium salt of this invention can form a structurally stable SEI film with a relatively low impedance on the surface of the negative electrode active material, thereby improving the high and low temperature performance of secondary batteries. x PO y F zFurthermore, an SEI film rich in LiF components can be formed. This SEI film has low interfacial impedance and can significantly improve the cycle performance of secondary batteries. Sulfur-containing lithium salts can form a dense and stable SEI film on the surface of the negative electrode active material, further improving the protective performance of the negative electrode active material.

[0019] In any embodiment, the cathode film-forming additive comprises a carbonate-based additive and / or a sulfate ester-based additive, optionally comprising one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, optionally comprising a sulfate ester-based additive and / or a hydrocarbon sulfate ester-based additive, further optionally comprising one or more of 1,3-propanesultone PS, propylenesultone PES, and 3-fluoro-1,3-propanesultone FPS, and one or more of vinyl sulfate ester-based additives.

[0020] As a result, the carbonate-based additive of this application has a strong dielectric constant and dissolves lithium salts more readily, causing lithium salts to dissociate lithium ions more easily, thereby improving the conductivity of the electrolyte. By blending it with the first organic solvent, the dielectric constant and viscosity of the electrolyte can be better adjusted, improving the ionic conductivity of the secondary battery and further improving the electrochemical window of the secondary battery. The sulfate ester-based additive can form a dense and stable film layer and can provide good protection for the active material.

[0021] In any embodiment, the electrolyte further comprises a lithium salt, one or more of lithium hexafluorophosphate LiPF6, lithium bisfluorosulfonylimide LiFSI, and lithium bistrifluoromethylsulfonylimide LiTFSI, where the mass percentage content of the lithium salt relative to the total mass of the electrolyte is optionally d%, such that 5% ≤ d ≤ 25%, and further optionally 10% ≤ d ≤ 20%. The lithium salt is considered to be a composite of lithium ions and anionic groups and has a significant effect on the electrolyte. The lithium salt has thermal stability and high conductivity.

[0022] In any embodiment, the separator comprises a base layer and a coating layer provided on the surface of the base layer, wherein the base material of the base layer comprises one or more types from polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide, and / or the coating layer comprises a ceramic coating layer and / or a polymer coating layer, wherein the ceramic particles in the ceramic coating layer optionally comprise one or more types from SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2, and BaSO4, and the polymer material of the polymer coating layer comprises one or more types from polyethylene PE, polypropylene PP, poly(p-phenylene terephthalamide PPTA), polyethylene terephthalate PET, polytetrafluoroethylene PTFE, polyacrylonitrile PAN, polyimide PI, and polyamide PA.

[0023] As a result, the substrate layer of the present invention has good permeability to lithium ions, which is advantageous for lithium ion movement, and a coating layer is provided on the surface of the substrate layer, which can further improve the mechanical properties of the separator.

[0024] A second aspect of the present application further provides a battery module comprising a secondary battery according to any one embodiment of the first aspect of the present application.

[0025] A third aspect of the present application further provides a battery pack comprising a battery module according to an embodiment of the second aspect of the present application.

[0026] A fourth aspect of the present application further provides a power consumption device comprising a secondary battery according to any one embodiment of the first aspect of the present application, a battery module according to an embodiment of the second aspect of the present application, or a battery pack according to an embodiment of the third aspect of the present application. [Brief explanation of the drawing]

[0027] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that need to be used in the embodiments of the present application will be briefly described below. Obviously, the drawings described below represent only a few embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

[0028] [Figure 1] This is a schematic diagram of one embodiment of the secondary battery of the present invention.

[0029] [Figure 2] Figure 1 is a schematic diagram of an exploded view of an embodiment of a secondary battery.

[0030] [Figure 3] This is a schematic diagram of one embodiment of the battery module of the present invention.

[0031] [Figure 4] This is a schematic diagram of one embodiment of the battery pack of the present invention.

[0032] [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown.

[0033] [Figure 6]This is a schematic diagram of one embodiment of a power consumption device that includes a secondary battery of the present invention as a power source.

[0034] Drawings are not always drawn to actual scale.

[0035] The explanation of the symbols is as follows:

[0036] 1 Battery pack 2 Upper enclosure 3 Lower enclosure 4 Battery Modules

[0037] 5 Secondary battery 51 Housing 52 Electrode Assembly

[0038] 53 Cover Plate

[0039] 6 Power consumption equipment [Modes for carrying out the invention]

[0040] The following describes in detail embodiments specifically disclosing the secondary battery, battery module, battery pack, and power consumption device of the present application. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] The “range” disclosed herein is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which in particular define the boundaries of the range. Ranges limited in this manner may or may not include end values ​​and can be any combination, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Similarly, if the minimum range values ​​1 and 2, and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all expected. In this application, unless otherwise stated, the numerical range “a-b” represents a contracted representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification indicates that all real numbers between "0 to 5" are listed, and "0 to 5" is a contracted representation of combinations of these numbers. Also, when a parameter is described as being an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, and preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if the method may further include step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or further steps (c), (a) and (b), etc.

[0044] Unless otherwise specified, the terms “equipped with” and “included” as used in this application may be open or closed. For example, “equipped with” and “included” may include or include other components not listed, or may include or include only the listed components.

[0045] Unless otherwise specified, the term “or” is inclusive in this application. For example, the phrase “A or B” means “A, B, or both A and B.” More specifically, any of the following conditions satisfy the “A or B” condition: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0046] In this application, the terms "multiple" and "multiple types" refer to two or more types.

[0047] In this application, the secondary battery may include lithium-ion batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, but the embodiments of this application are not limited to these.

[0048] A secondary battery comprises an electrode assembly consisting of a positive electrode sheet, a negative electrode sheet, and a separator, and an electrolyte. The secondary battery operates primarily through the movement of metal ions between the positive electrode sheet and the negative electrode sheet, with the positive electrode sheet containing a positive electrode active material and the negative electrode sheet containing a negative electrode active material. In this specification, the metal ions may be lithium ions, sodium ions, etc., and the charging process will now be described using lithium ions as the metal ions.

[0049] In the charging process of a secondary battery, the electrode dynamics process typically includes: (1) a lithium ion desorption step in which lithium ions desorb from the positive electrode active material and move to the electrolyte phase; (2) a liquid phase mass transfer step in the electrolyte phase in which solvated lithium ions in the electrolyte diffuse and transfer to the surface of the negative electrode active material; (3) a surface transformation step in which solvated lithium ions adsorb and react on the surface of the negative electrode active material during the initial charge to form a solid electrolyte interface (SEI) film, and in subsequent charging processes, solvated lithium ions adsorb on the surface of the SEI film and, after a desolvation process, reach the surface of the negative electrode active material; (4) a charge exchange step in which lithium ions obtain electrons from the surface of the negative electrode active material to form lithium insertion products; and (5) a solid phase mass transfer step of lithium insertion products in which the lithium insertion products solid-phase diffuse from the surface of the negative electrode active material into the interior, completing the charging process.

[0050] As the charge multiplier increases, it is required that lithium ions rapidly detach from the positive electrode active material and be inserted into the negative electrode active material during the charge and discharge process, and that lithium ions rapidly detach from the negative electrode active material and be inserted into the positive electrode active material. In this process, both solid-phase and liquid-phase mass transfer of lithium ions are limiting factors that affect the lithium ion transfer rate, and thus have a significant impact on the rapid charging performance of secondary batteries. Furthermore, during the charge and discharge process, side reactions may occur between the surface of the active material and the electrolyte, destroying the structure of the active material and significantly shortening its lifespan, potentially reducing the cycle life of the secondary battery.

[0051] Therefore, the inventors propose a secondary battery that improves the rapid charging performance of the secondary battery by increasing the transfer rate of lithium ions in solid-phase and liquid-phase mass transfer, and also improves the cycle stability and cycle life of the secondary battery by protecting the surface of the active material, thereby improving the structural stability of the active material. Next, the technical invention of this application will be described in detail.

[0052] secondary battery

[0053] According to the first aspect, the present application provides a secondary battery. A secondary battery, also called a rechargeable battery or storage battery, is a battery that can be used continuously by activating the active material through charging after the battery has been discharged.

[0054] The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet contains a positive electrode active material, the negative electrode sheet contains a negative electrode active material, and the separator is provided between the positive electrode sheet and the negative electrode sheet. The electrolyte comprises a first organic solvent and a film-forming additive. The film-forming additive is arranged to form an interfacial film on the surface of the positive electrode active material and / or the negative electrode active material. If the porosity of the separator is ε%, the mass percentage content of the film-forming additive relative to the total mass of the electrolyte is b%, and the viscosity of the electrolyte at 25°C is c(mPa·s), then the secondary battery satisfies 4≦(b*ε) / c≦240.

[0055] Although the mechanism is not clear, we speculate that the present invention can achieve both improved rapid charging performance and improved cycle life of secondary batteries as follows.

[0056] In the process of lithium ions moving from the positive electrode sheet to the negative electrode sheet, they must first move from the positive electrode sheet to the separator, and then from the separator to the negative electrode sheet. Therefore, since the porosity of the separator has a certain effect on the lithium ion migration rate, the porosity of the separator is treated as one of the variables controlled in this invention.

[0057] In the liquid phase mass transfer process, lithium ions move through the electrolyte, and the viscosity of the electrolyte has a certain influence on the lithium ion movement rate. Since a lower viscosity is more favorable for lithium ion movement, the viscosity of the electrolyte has a certain influence on the lithium ion movement rate, and this is considered another variable controlled in this invention. The first organic solvent, as the main component of the electrolyte, has a significant influence on the viscosity of the electrolyte; therefore, the viscosity of the electrolyte can be adjusted by selecting the first organic solvent. Naturally, film-forming additives also have a certain influence on the viscosity of the electrolyte; therefore, the final viscosity of the electrolyte can be determined by selecting the first organic solvent and controlling the mass percentage content of the film-forming additive. When the viscosity of the electrolyte is within an appropriate range, the separator can be properly permeated. In the charge-discharge process of a secondary battery, this contributes to the rapid reflux of the electrolyte and to the rapid transport of lithium ions.

[0058] In this invention, by adjusting the porosity of the separator, the viscosity of the electrolyte, and the film-forming additive to satisfy the above ranges, and comprehensively adjusting the lithium ion migration rate in solid-phase and liquid-phase mass transfer, the average lithium ion migration rate can be improved, thereby enhancing the rapid charging capability of the secondary battery. Furthermore, the film-forming additive can not only adjust the viscosity of the electrolyte to further adjust the lithium ion migration rate in the liquid phase, but can also form a protective layer on the surface of the active material, passivating the surface of the active material, reducing the risk of side reactions occurring between the surface of the active material and the electrolyte, improving the structural stability of the active material, and extending the cycle life of the secondary battery. Here, film-forming additives, particularly lithium salt-based additives, are advantageous because the solid electrolyte interface (SEI) film formed on the surface of the negative electrode active material has a relatively low impedance, making it easier to insert and remove lithium ions. Of course, other types of additives, such as ester-based additives, may also be used as film-forming additives.

[0059] Selectively, 4 ≤ (b*ε) / c ≤ 180, and exemplary, (b*ε) / c may be 4, 5, 8, 10, 12, 15, 18, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, 160, 170, 180, 190, 200, 210, 220, or 240, or it may be a range consisting of any two of the above numbers.

[0060] In some embodiments, 25 ≤ ε ≤ 55.

[0061] When the porosity of the separator is within the above range, the porosity of the separator is not too small, its liquid permeability is good, its lithium ion permeability is strong, which is advantageous for lithium ions to move to adjacent active materials through the separator, and the rapid charging capability of the secondary battery can be further improved. When the porosity of the separator is not too large, the risk of direct contact between the positive electrode sheet and the negative electrode sheet causing a short circuit is reduced, and the separator has good mechanical properties, so even if dendrites are formed inside the secondary battery, the separator is less likely to break and cause a short circuit, thus ensuring the safety performance of the secondary battery. Preferably, 30 ≤ ε ≤ 50, and exemplary, the porosity ε% of the separator may be 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 46%, 48%, 50%, 52%, 53%, 54%, or 55%, or it may be in a range consisting of any two of the above values.

[0062] In some embodiments, 0.1 ≤ b ≤ 8.

[0063] When the mass percentage content of the film-forming additive is within the above range, the film-forming additive can undergo a film-forming reaction with the active material to form a dense and uniform film layer. This provides good protection for the active material, and the film-forming additive, such as a lithium salt-based additive, can form an SEI film with a low film-forming impedance, thus achieving both longevity and power. Preferably, 0.1 ≤ b ≤ 6, and exemplary, the mass percentage content b% of the film-forming additive may be 0.1%, 0.5%, 0.8%, 1%, 1.5%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%, or it may be within the range of any two of the above values.

[0064] In some embodiments, 1 ≤ c ≤ 6.

[0065] When the viscosity of the electrolyte is within the above range, the viscosity of the electrolyte is not too high, its ionic conductivity is relatively high, which is advantageous for improving the ion transfer rate and can improve the rapid charging capability of the secondary battery. Furthermore, when the viscosity of the electrolyte is within the above range, the compatibility between the electrolyte and the positive and negative electrode sheets is relatively good, and side reactions with the active material in the positive and negative electrode sheets are less likely to occur, thus improving the cycle stability of the secondary battery. Preferably, 2 ≤ c ≤ 5, and exemplary, the viscosity c (mPa·s) of the electrolyte may be 1 mPa·s, 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s, or 6 mPa·s, or it may be within a range consisting of any two of the above values.

[0066] In some embodiments, the mass percentage content of the first organic solvent relative to the total mass of the electrolyte is denoted by a, and the secondary battery further satisfies 2 ≤ c + 2 * a % ≤ 8.

[0067] By adjusting the mass percentage content of the first organic solvent, the viscosity of the electrolyte can be adjusted to an appropriate range, allowing for the formation of a stable interfacial film during the film formation process and complete coating of the active material surface. For example, c+2*a% may be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8, or within a range consisting of any two of the above values.

[0068] In some embodiments, 60 ≤ a ≤ 90, preferably 65 ≤ a ≤ 85. Exemplarily, the mass percentage content a% of the first organic solvent relative to the total mass of the electrolyte may be 60%, 65%, 70%, 75%, 80%, 85%, or 90%, or within a range of any two of the above values.

[0069] In some embodiments, the first organic solvent includes one or more of the following: linear carbonate solvents, carboxylic acid ester solvents, and nitrile solvents. Because the viscosity of the solvent is low, the viscosity range of the entire electrolyte can be adjusted to an appropriate range. Furthermore, if the first organic solvent includes two or more types, the viscosity and ionic conductivity of the electrolyte can be adjusted synergistically, and since multiple types of solvents can participate in the film formation reaction, the film layer structure can contain multiple types of components, thereby improving the stability of the interfacial film.

[0070] As an example of a linear carbonate solvent, the linear carbonate solvent includes one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl propyl carbonate (MPC). The linear carbonate solvent has relatively low viscosity, is favorable for ionic conductivity, has high electrochemical stability, and has a high electrochemical window.

[0071] Examples of carboxylic acid ester solvents include one or more of the following: ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), methyl formate (MF), ethyl butyrate (EB), butyl acetate (BA), methyl propionate (MP), methyl butyrate (MB), propyl butyrate (PB), and butyl butyrate (BB). Carboxylic acid ester solvents have relatively low viscosity, and by using a combination of multiple types of carboxylic acid ester solvents, the electrolyte can be made to have even lower surface tension.

[0072] As an example of a nitrile-based solvent, the nitrile-based solvent includes one or more of acetonitrile AN, glutaronitrile GLN, and adiponitrile ADN. Because the above nitrile-based solvent has a relatively low viscosity and a relatively high dielectric constant, it is advantageous for improving the lithium ion transfer rate, and because the nitrile-based solvent has high stability, it is less likely to side-react with the surface of the active material, thus ensuring the structural stability of the active material and guaranteeing the cycle stability of the secondary battery.

[0073] In some embodiments, the electrolyte may further contain a second organic solvent, which may be an ether-based solvent. Since ether-based solvents also have relatively low viscosity, they are advantageous in further improving the overall viscosity of the electrolyte. Furthermore, the ether-based solvent is advantageous in that lithium in the secondary battery maintains a good morphological structure during the charge-discharge cycle process, thereby improving the cycle stability of the secondary battery and extending its cycle life.

[0074] As an example of an ether-based solvent, the aforementioned ether-based solvent may include ether, etc.

[0075] In some embodiments, the film-forming additive comprises a negative electrode film-forming additive and a positive electrode film-forming additive, wherein the negative electrode film-forming additive is arranged to form an interfacial film on the surface of the negative electrode active material, and the mass percentage content of the negative electrode film-forming additive relative to the total mass of the electrolyte is b1%, and the positive electrode film-forming additive is arranged to form an interfacial film on the surface of the positive electrode active material, and the mass percentage content of the positive electrode film-forming additive relative to the total mass of the electrolyte is b2%, and the secondary battery satisfies 1 ≤ b2 / b1 ≤ 60.

[0076] The negative electrode film-forming additive can form an SEI film on the surface of the negative electrode active material by inducing a film-forming reaction on the surface of the negative electrode active material. Since the SEI film covers the surface of the negative electrode active material in situ, it stabilizes the structure of the negative electrode active material, reduces the risk of persistent side reactions between the negative electrode active material and the electrolyte, and guarantees the electrochemical performance of the negative electrode active material. Furthermore, the negative electrode film-forming additive may also contain lithium salt-based additives, and since the SEI film formed on the negative electrode has a low impedance, it is advantageous for lithium ion insertion and deinsertion.

[0077] Cathode film-forming additives can form a cathode electrolyte interface (CEI film) on the surface of the cathode active material by inducing a film formation reaction on the surface of the cathode active material. Because the CEI film coats the surface of the cathode active material in situ, it not only stabilizes the structure of the cathode active material but also reduces the risk of the electrolyte decomposing and corroding the cathode active material, thereby leaching transition metals from the cathode active material. Furthermore, it protects the cathode active material and guarantees its electrochemical performance.

[0078] In this application, CEI films and SEI films are collectively referred to as interfacial films.

[0079] In this application, by adjusting the content of the negative electrode film-forming additive and the positive electrode film-forming additive to satisfy the above formula, the electrolyte can form an SEI film on the surface of the negative electrode active material and a CEI film on the surface of the positive electrode active material. Furthermore, the interfacial impedance of the two types of film layers is relatively low, the kinetic activity is good, and the charge transfer impedance in the secondary battery is small, which is advantageous for rapid lithium ion transfer and can improve the rapid charging performance of the secondary battery. Preferably, 1 ≤ b2 / b1 ≤ 40, and exemplary, b2 / b1 may be 1, 2, 3, 5, 8, 10, 15, 20, 22, 25, 28, 30, 32, 35, 40, 42, 45, 48, 50, 52, 55, 58 or 60, or it may be within a range consisting of any two of the above values.

[0080] In some embodiments, 0.01 ≤ b1 ≤ 1.5.

[0081] When the negative electrode film-forming additive is within the above range, it is possible to form a dense and stable SEI film on the surface of the negative electrode active material, thereby adequately protecting the negative electrode active material, improving the structural stability of the negative electrode active material, and ensuring the cycle stability of the secondary battery. Preferably, 0.1 ≤ b1 ≤ 1.2. Exemplarily, the mass percentage content b1% of the negative electrode film-forming additive may be 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, or 1.5%, or within a range consisting of any two of the above values.

[0082] In some embodiments, 0.1 ≤ b2 ≤ 7.

[0083] When the positive electrode film-forming additive is within the above range, it is possible to form a dense and stable CEI film on the surface of the positive electrode active material, thereby adequately protecting the positive electrode active material, improving the structural stability of the positive electrode active material, and ensuring the cycle stability of the secondary battery. Preferably, 0.5 ≤ b2 ≤ 5. Exemplarily, the mass percentage content b2% of the positive electrode film-forming additive may be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%, or within a range consisting of any two of the above values.

[0084] Examples of negative electrode film-forming additives include one or more of the following: boron-containing lithium salts, phosphorus-containing lithium salts, and sulfur-containing lithium salts.

[0085] Boron-containing lithium salts, as lithium salts with a boron atom as the central atom, can coordinate with alkoxy groups, o-diphenols, o-hydroxyl groups, carboxylic acids, etc., to form anionic complexes. These anionic complexes mainly have a large π-conjugated structure, with a relatively dispersed negative charge distribution of the central ion, delocalized charge, and a large anionic radius. As a result, the anion is less likely to form a strong ion pair with lithium ions in organic solvents, and its solubility is relatively good. The more electron-withdrawing groups there are in the anionic complex, the more stable the anionic structure becomes, increasing the solubility of lithium ions in the electrolyte and improving the conductivity of the electrolyte. Furthermore, boron-containing lithium salts can form a high-performance SEI film on the surface of the negative electrode active material. Since the SEI film is insoluble in organic solvents and can stably exist in organic electrolytes, it effectively reduces the insertion of solvent molecules from the electrolyte into the negative electrode active material, ensuring the structural stability of the negative electrode active material and further improving the cycle performance of the secondary battery.

[0086] Phosphorus-containing lithium salt additives have relatively large anionic groups and high ionic conductivity, which is advantageous for further improving the kinetic performance of the electrolyte. Furthermore, phosphorus-containing lithium salt additives can form a CEI film on the surface of the positive electrode active material, and since this formed CEI film has high lithium ion conductivity, it can significantly suppress the sustained decomposition of the electrolyte, reduce the elution of transition metal ions in the positive electrode active material, and improve the cycle performance of the secondary battery. In addition, phosphorus-containing lithium salt additives can also form an SEI film on the surface of the negative electrode active material, which has low interfacial impedance, thus significantly improving the cycle performance of the battery.

[0087] Sulfur-containing lithium salt additives exhibit excellent oxidation resistance, high thermal stability, and are not sensitive to water in the electrolyte, thus minimizing the likelihood of side reactions. Furthermore, their relatively high conductivity is advantageous for improving the lithium ion transfer rate, thereby enhancing the kinetic performance of the electrolyte.

[0088] Examples of boron-containing lithium salts include one or more of the following: lithium tetrafluoroborate (LiBF4), lithium disoxalate (LiB(C2O4)2, abbreviated as LiBOB), and lithium difluorooxalate (LiC2O4F2, abbreviated as LiDFOB). Furthermore, boron-containing lithium salts include compositions of lithium tetrafluoroborate (LiBF4), lithium disoxalate (LiB(C2O4)2, abbreviated as LiBOB), and lithium difluorooxalate (LiC2O4F2, abbreviated as LiDFOB).

[0089] When lithium tetrafluoroborate (LiBF4) is used in combination with organic solvents in the electrolyte, such as carbonate-based solvents or additives, the viscosity of the lithium tetrafluoroborate system is relatively low, which is advantageous for the release of lithium ions and improves the conductivity of the electrolyte. SEI films formed from lithium tetrafluoroborate have relatively uniform thickness, relatively good kinetic activity, and relatively low charge transfer impedance in secondary batteries, thus significantly improving the low-temperature performance of secondary batteries. SEI films are resistant to thermal decomposition and have relatively stable performance at high temperatures, thus significantly improving the high-temperature performance of secondary batteries.

[0090] Either lithium borate dioxalate (LiBOB) or lithium borate difluorooxalate (LiDFOB) has a passivation effect on the positive electrode current collector in the positive electrode sheet, thereby reducing the risk of corrosion of the positive electrode current collector due to side reactions with the positive electrode current collector and improving the structural stability of the positive electrode sheet. Furthermore, electrolytes containing either lithium borate dioxalate (LiBOB) or lithium borate difluorooxalate (LiDFOB) are less likely to generate acidic substances, further reducing the risk of corrosion of the positive electrode current collector. Lithium borate dioxalate (LiBOB) and lithium borate difluorooxalate (LiDFOB) have good compatibility with the positive electrode active material, are advantageous for lithium ion movement, and can form an effective SEI film on the surface of the negative electrode active material, improving the protective performance of the negative electrode active material.

[0091] When lithium tetrafluoroborate (LiBF4), lithium dioxalate borate (LiBOB), and lithium difluorooxalate borate (LiDFOB) are used in combination, the SEI film formed by the three has a high concentration of constituent elements, resulting in a more stable SEI film structure. This structural stability is guaranteed, and a relatively low impedance value of the SEI film is ensured, thereby guaranteeing the low-temperature performance of the secondary battery.

[0092] When the secondary battery of this invention contains the above-mentioned boron-containing lithium salt, a structurally stable SEI film with a relatively low impedance value can be formed on the surface of the negative electrode active material, thereby improving the high and low temperature performance of the secondary battery.

[0093] Examples of phosphorus-containing lithium salts include one or more of the following: lithium difluorophosphate (LiPO2F2), lithium fluorophosphate (Li2PO3F), and lithium phosphate (Li3PO4).

[0094] The above phosphorus-containing lithium salt is an inorganic lithium phosphate salt, and Li is present on the surface of the negative electrode active material. x PO y F z This allows for the formation of an SEI film rich in LiF components, and because this SEI film has low interfacial impedance, it can significantly improve the cycle performance of secondary batteries. Furthermore, during the initial charging process of secondary batteries, it can participate in the formation of a positive electrode film, creating a stable and low-impedance CEI film. This CEI film can effectively reduce the oxidative decomposition of the electrolyte, for example, by effectively reducing side reactions between the carbonate ester solvent in the electrolyte and the surface of the positive electrode active material. This ensures the structural stability of the electrolyte, mitigates the destruction of the positive electrode active material, and improves the cycle performance of secondary batteries.

[0095] Examples of sulfur-containing lithium salts include one or more of the following: lithium fluorosulfonate (LiFSO3), lithium sulfate (Li2SO4), and lithium sulfamate (LiSO3NH2).

[0096] The above-mentioned sulfur-containing lithium salt can form a dense and stable SEI film on the surface of the anode active material, further improving the protective performance of the anode active material.

[0097] In some embodiments, the cathode film-forming additive includes a carbonate-based additive and / or a sulfate ester-based additive.

[0098] The carbonate-based additive includes one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinylethylene carbonate (VEC), and dioctyl carbonate (CC). The carbonate-based additive can form a dense and stable film layer and can provide good protection to the active material. Furthermore, the carbonate-based additive has a strong dielectric constant and dissolves lithium salts more readily, causing lithium salts to dissociate lithium ions more easily, improving the conductivity of the electrolyte. By combining it with the first organic solvent, the dielectric constant and viscosity of the electrolyte can be better adjusted, improving the ionic conductivity of the secondary battery and further improving the electrochemical window of the secondary battery.

[0099] The sulfate ester additive comprises a cyclic sulfonic acid ester additive and / or a hydrocarbon sulfate ester additive. The cyclic sulfonic acid ester additive further comprises one or more of 1,3-propanesultone PS, propylenesultone PES, and 3-fluoro-1,3-propanesultone FPS, and the hydrocarbon sulfate ester additive comprises one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS. The sulfate ester additive can form a dense and stable film layer and can provide good protection to the active material.

[0100] In some embodiments, the electrolyte may further contain a lithium salt. The lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), and lithium bistrifluoromethylsulfonylimide (LiTFSI).

[0101] Lithium salts are considered to be complexes of lithium ions and anionic groups, and they have a significant influence on the electrolyte. The above lithium salts have thermal stability and high conductivity.

[0102] In some embodiments, the mass percentage content of the lithium salt relative to the total mass of the electrolyte is expressed as d%, where 5% ≤ d ≤ 25%, and more preferably 10% ≤ d ≤ 20%.

[0103] When the mass percentage content of the lithium salt is within the above range, it is advantageous for the rapid movement of lithium ions, while the lithium salt can form an interfacial film on the surface of the active material together with other substances, thereby stabilizing the active material. Preferably, 10% ≤ d ≤ 20%, and exemplary, the mass percentage content d% of the lithium salt may be 5%, 6%, 7%, 8%, 9%, 10%, 12%, 13%, 15%, 16%, 18%, 20%, 21%, 22%, 24%, or 25%, or within any two of the above numerical ranges.

[0104] The electrolyte of this application can be prepared according to conventional methods in the art. For example, the electrolyte can be obtained by uniformly mixing the additive, the solvent, the electrolyte salt, etc. The order in which the substances are added is not particularly limited; for example, the additive, the electrolyte salt, etc. can be added to the non-aqueous solvent and uniformly mixed to obtain a non-aqueous electrolyte.

[0105] In this application, each component in the electrolyte and its content can be measured according to methods known in the art. For example, they can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0106] Furthermore, when testing the electrolyte of this invention, the electrolyte may be obtained directly from a freshly prepared solution, or it may be obtained from a secondary battery. One exemplary method for obtaining the electrolyte from a secondary battery includes the steps of discharging the secondary battery to its discharge cutoff voltage (generally, completely discharging the battery for safety reasons), centrifuging it, and then extracting an appropriate amount of the liquid obtained by centrifuging as a non-aqueous electrolyte. The non-aqueous electrolyte may also be obtained directly from the filling port of the secondary battery.

[0107] [Positive electrode sheet]

[0108] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0109] The positive electrode film layer contains a positive electrode active material, and the positive electrode active material can employ a positive electrode active material for secondary batteries known in the art. For example, the positive electrode active material may include at least one of lithium transition metal oxides, lithium-containing phosphates having an olivine structure, and modified compounds thereof. The lithium transition metal oxide is, for example, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of the lithium-containing phosphate having an olivine structure include lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and at least one of modified compounds thereof. The present application is not limited to these materials, and conventional known materials used as positive electrode active materials for other secondary batteries can be used. These positive electrode active materials may be used alone or in combination of two or more.

[0110] In some embodiments, the positive electrode active material is LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-cThe material contains O2, where M and N are each independently selected from Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and the following conditions apply: 0≦y≦1, 0≦x<1, 0≦z≦1, x+y+z≦1, 0≦a≦1, 0≦b≦1, 0≦c≦1, a+b+c≦1. When a boron-containing lithium salt is used as the positive electrode active material, the B atoms in the boron-containing lithium salt readily bond with the O atoms in the positive electrode active material, thereby reducing the charge transfer resistance of the positive electrode active material and reducing the diffusion resistance of lithium ions in the positive electrode active material phase. Therefore, when the non-aqueous electrolyte contains appropriate amounts of lithium tetrafluoroborate and lithium difluorooxalate borate, the low-cobalt or cobalt-free cathode active material exhibits a significantly improved lithium ion diffusion rate. As a result, lithium ions within the phase of the low-cobalt or cobalt-free cathode active material are replenished to the surface in a timely manner, avoiding excessive lithium delithiation on the surface of the low-cobalt or cobalt-free cathode active material and stabilizing its crystal structure. Because the crystal structure of the low-cobalt or cobalt-free cathode active material is more stable, the probability of problems such as irreversible strain and increased lattice defects in the cathode active material, which can occur due to excessive lithium delithiation on the surface of the low-cobalt or cobalt cathode active material, can be significantly reduced.

[0111] LiRing x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c O2 can be produced according to conventional methods in this art. An exemplary production method involves mixing a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an N element precursor, followed by sintering. The sintering atmosphere may be an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere. The O2 concentration in the sintering atmosphere is, for example, 70% to 100%. The sintering temperature and sintering time can be adjusted according to the actual conditions.

[0112] For example, a lithium source may include, but is not limited to, at least one of lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), lithium acetate (CH3COOLi), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3). For example, a nickel source may include, but is not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. For example, a cobalt source may include, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. For example, a manganese source may include, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. For example, an aluminum source may include, but is not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. For example, an element M precursor includes, but is not limited to, at least one of the following: an oxide of element M, a nitrate compound, a carbonate compound, a hydroxide, and an acetate compound. For example, an element N precursor includes, but is not limited to, at least one of the following: ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0113] In some examples, based on the total mass of the positive electrode film layer, the molecular formula LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-cThe mass percentage content of O2 in layered materials is 80% to 99%. For example, LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c The mass percentage content of the layered material being O2 may be in the range of 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any of the above values. Preferably, the molecular formula is LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c The mass percentage content of the layered material being O2 is 85%~99%, 90%~99%, 95%~99%, 80%~98%, 85%~98%, 90%~98%, 95%~98%, 80%~97%, 85%~97%, 90%~97%, or 95%~97%.

[0114] In some embodiments, the positive electrode film layer may optionally contain a positive electrode conductive agent. In this application, the type of positive electrode conductive agent is not particularly limited, and as an example, the positive electrode conductive agent includes one or more types selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode film layer.

[0115] In some embodiments, the positive electrode film layer may optionally contain a positive electrode adhesive. In this application, the type of positive electrode adhesive is not particularly limited, and as an example, the positive electrode adhesive may include one or more types selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resins. In some embodiments, the mass percentage content of the positive electrode adhesive is 5% or less based on the total mass of the positive electrode film layer.

[0116] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. Examples of metal foils include aluminum foil and aluminum alloy foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate may include one or more types selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0117] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, a selectable conductive agent, a selectable adhesive, and any other components in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP).

[0118] [Negative electrode sheet]

[0119] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, which contains a negative electrode active material.

[0120] For example, the negative electrode current collector has two opposing surfaces in the direction of its own thickness, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0121] In some embodiments, the negative electrode active material can be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of the following: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium aluminum alloys. The silicon-based material may be at least one selected from elemental silicon, silicon oxide, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0122] In some embodiments, the negative electrode film layer may optionally contain a negative electrode adhesive. The type of negative electrode adhesive is not particularly limited in this application, and as an example, the negative electrode adhesive may include one or more types selected from styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative electrode adhesive is 5% or less based on the total mass of the negative electrode film layer.

[0123] In some embodiments, the negative electrode film layer may optionally contain a negative electrode conductive agent. In this application, the type of negative electrode conductive agent is not particularly limited, and as an example, the negative electrode conductive agent may include one or more types selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the negative electrode conductive agent is 5% or less based on the total mass of the negative electrode film layer.

[0124] In some embodiments, the negative electrode film layer may contain other additives as needed. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na) or PTC thermistor materials. In some embodiments, the mass percentage content of the other additives is 2% or less based on the total mass of the negative electrode film layer.

[0125] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. Examples of metal foils include copper foil and copper alloy foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate may include one or more types selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0126] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable adhesive, and other selectable auxiliary agents in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0127] The negative electrode sheet does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet further includes a protective layer covering the surface of the negative electrode film layer.

[0128] [Separator]

[0129] In some embodiments, the secondary battery further includes a separator. In this application, the type of separator is not particularly limited, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0130] In some embodiments, the separator includes a base layer and a coating layer provided on the surface of the base layer, wherein the base material of the base layer includes one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide, and the coating layer includes a ceramic coating layer and / or a polymer coating layer.

[0131] The substrate layer has good permeability to lithium ions, which is advantageous for lithium ion movement, and a coating layer is provided on the surface of the substrate layer, which can further improve the mechanical properties of the separator.

[0132] Preferably, the ceramic particles in the ceramic coating layer include one or more of the following: SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2, and BaSO4.

[0133] Preferably, the polymer material of the polymer coating layer includes one or more of the following: polyethylene (PE), polypropylene (PP), poly(p-phenylene terephthalamide) (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI), and polyamide (PA). The polymer coating layer can be made of the same or different material as the substrate layer. The thicknesses of the polymer coating layer and the substrate layer may differ, and preferably, the thickness of the polymer coating layer is smaller than the thickness of the substrate layer.

[0134] In other embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, but is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, but is not particularly limited.

[0135] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be manufactured as an electrode assembly by a winding process or a lamination process.

[0136] In some embodiments, the secondary battery may have an outer casing. This casing is used to seal the electrode assembly and electrolyte.

[0137] In some embodiments, the casing of the secondary battery may be a rigid case such as a hard plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft pack, such as a bag-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0138] In this application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. Figure 1 shows a rectangular secondary battery 5 as an example.

[0139] In some embodiments, as shown in Figures 1 and 2, the exterior may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 covers the opening so as to close the housing cavity. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0140] The method for manufacturing the secondary battery of the present invention is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, the electrolyte can be injected after drying, and a secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0141] In some embodiments of the present invention, the secondary battery according to the present invention may be assembled as a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0142] Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed together with fasteners.

[0143] Optionally, the battery module 4 may further comprise a case having a housing space for accommodating multiple secondary batteries 5.

[0144] In some embodiments, the battery modules may be assembled as a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0145] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0146] power consumption equipment

[0147] In a second aspect, the present application provides a power consumption device comprising at least one of the secondary battery, battery module, and battery pack of the present application. The secondary battery, battery module, and battery pack may be used as a power source for the power consumption device or as an energy storage means for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, laptop computers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0148] Power consumption devices can be configured to use secondary batteries, battery modules, or battery packs, depending on their usage needs.

[0149] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the requirements for high output and high energy density of the power consumption device, a battery pack 1 or battery module can be used.

[0150] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are generally required to be thin and can use rechargeable batteries as a power source.

[0151] Examples

[0152] The following examples illustrate the disclosures of this application in more detail, and these examples are used merely for interpretive purposes. It will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the disclosures. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are calculated on a mass basis, and all reagents used in the examples can be obtained by purchase or synthesis according to conventional methods, and are ready for direct use without further processing. The apparatus used in the examples can also be obtained by purchase.

[0153] Example 1

[0154] 1. Preparation of the positive electrode sheet

[0155] A 12 μm thick aluminum foil was used as the positive electrode current collector.

[0156] Positive electrode active material LiNi 0.65 Co 0.07 Mn 0.28Carbon black, a conductive agent, and polyvinylidene fluoride (PVDF), an adhesive, were thoroughly mixed in an appropriate amount of NMP, a solvent, in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. This slurry was then uniformly applied to the surface of aluminum foil, which served as the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained.

[0157] 2. Fabrication of the negative electrode sheet

[0158] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0159] A negative electrode slurry was formed by thoroughly stirring and mixing graphite, an adhesive (styrene-butadiene rubber (SBR)), a thickener (carboxymethylcellulose sodium (CMC-Na)), and a conductive agent (carbon black (SuperP)) in a weight ratio of 96.2:1.8:1.2:0.8 with an appropriate amount of solvent (deionized water) to form a uniform negative electrode slurry. This slurry was then uniformly applied to the surface of a copper foil negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0160] 3. Separator

[0161] A porous polyethylene (PE) film was used as the separator.

[0162] 4. Preparation of the electrolyte

[0163] Under conditions with a water content of less than 10 ppm, ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate, which are non-aqueous organic solvents, were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent. Additives were then dissolved in the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L. For specific substances contained in the electrolyte, please refer to the table below.

[0164] 5. Manufacturing of a secondary battery

[0165] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, with the separator positioned between the positive and negative electrode sheets to provide isolation. The assembly is then wound up to obtain the electrode assembly. The electrode assembly is placed in an outer case, dried, and then injected with electrolyte. After processes such as vacuum sealing, standing, chemical formation, and shaping, a lithium-ion battery is obtained.

[0166]

[0167] Example 2

[0168] Examples 2-1 to 2-8

[0169] The secondary battery was prepared in a similar manner to Example 1, except that the void ratio ε% of the separator was adjusted and 4 ≤ (b*ε) / c ≤ 240. See Tables 1 to 3 for specific parameters.

[0170] Comparative Example

[0171] Comparative Example 1 and Comparative Example 2

[0172] The secondary battery was prepared in a similar manner to Example 1, except that the porosity ε% of the separator was adjusted. See Tables 1 to 3 for specific parameters.

[0173] Example 3

[0174] Examples 3-1 to 3-7

[0175] The secondary battery was prepared in a similar manner to Example 1, except that the mass percentage content b1% of the "negative electrode film forming additive" was adjusted. The specific parameters are shown in Tables 1 to 3.

[0176] Example 4

[0177] Examples 4-1 to 4-7

[0178] The secondary battery was prepared in a similar manner to Example 1, except that the mass percentage content of the "positive electrode film forming additive" (b2%) was adjusted. See Tables 1 to 3 for specific parameters.

[0179] Example 5

[0180] Examples 5-1 to 5-3

[0181] The secondary battery was prepared in a similar manner to Example 1, except that the mass percentage content of the "first organic solvent" (a%) was adjusted. See Tables 1 to 3 for specific parameters.

[0182] [Table 1]

[0183] In Table 1, b1 = b11 + b12 + b13.

[0184] [Table 2]

[0185] In Table 2, b2 = b21 + b22.

[0186] [Table 3]

[0187] In Table 3, b = b1 + b2.

[0188] Test Department

[0189] 1. Method for measuring the porosity ε% of the separator

[0190] The porosity was measured using the gas displacement method according to GB / T24586. The porosity ε = (V1 - V2) / V1 * 100%, where V1 is the apparent volume of the sample and V2 is the true volume of the sample.

[0191] 2. Method for measuring the content of each component in the electrolyte.

[0192] After obtaining the electrolyte from a rechargeable battery using a freshly prepared electrolyte, the components of the electrolyte may be measured using one or more methods such as gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), or nuclear magnetic resonance spectroscopy (NMR).

[0193] Following gas chromatography-mass spectrometry (GC-MS) (GB / T-9722-2006 / GB / T6041-2002), a combination of gas chromatography and mass spectrometry is employed. After separating each component in the sample by gas chromatography, each component is subdivided into fragment ions by mass spectrometry and separated by mass-to-charge ratio (m / z) to form a specific mass spectrum to obtain a qualitative analysis of each organic component in the electrolyte. Subsequently, each organic component in the electrolyte is separated in a chromatography column to generate detection signal spectra for each component, and qualitative analysis of the components is performed by adjusting the retention time. Quantitative analysis is then achieved by calibrating the peak area to match the standard, and a quantitative test analysis of the organic components in the electrolyte is obtained.

[0194] Ion chromatography (IC): According to JY / T-020, the lithium salt and lithium salt additive anions in the electrolyte are detected and quantified by ion chromatography.

[0195] Qualitative and quantitative analyses of the components in the electrolyte will be performed according to nuclear magnetic resonance spectroscopy (NMR): JY / T0578-2020.

[0196] 3. Test method for viscosity c (mPa·s) of electrolyte at 25°C

[0197] At a constant temperature, the shear force exerted on the rotor as it continuously rotates at a constant speed within the sample generates torque in the spring, and the viscosity value is obtained by the torque being proportional to the viscosity. Specifically, the viscosity of the finished electrolyte is tested using a Brookfield (DV-2TLV) viscometer. The ambient temperature is controlled to 25°C and the ambient humidity to less than 80%, 30 mL of electrolyte is taken, and its temperature is kept constant in a 25°C water bath for at least 30 minutes, the rotor is placed in the sample cup, the sample is placed to about 0.3 cm from the opening of the cup, the connected viscometer is started, a rotation speed of 70 RPM is selected and the test is performed, 10 data points are collected, and the average value of multiple points is calculated.

[0198] 4. Cycle performance testing of secondary batteries

[0199] The secondary battery was charged at 45°C with a constant current of 1C to 4.3V, and constant voltage charging was continued until the current dropped to 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded and recorded as the first charge capacity. After the secondary battery was left to stand for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This constituted one charge-discharge cycle, and the discharge capacity at this time was recorded and recorded as the first discharge capacity. The secondary battery was tested for cycle charge-discharge according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 25°C = discharge capacity after 600 cycles / first discharge capacity × 100%.

[0200] 5. Rapid charging performance of rechargeable batteries

[0201] At 25°C, the rechargeable battery prepared as described above was charged with a constant current of 0.33C until the charge cutoff voltage was 4.4V. Then, it was charged at a constant voltage until the current was reduced to 0.05C, left to stand for 5 minutes, and then discharged with a constant current of 0.33C until the discharge cutoff voltage was 2.8V. The actual capacity was recorded as C0.

[0202] Subsequently, the secondary batteries are charged sequentially with constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until the total battery charge cutoff voltage of 4.4V or the negative electrode cutoff potential of 0V (based on whichever was reached first). After each charge is complete, the batteries must be discharged with 1C0 until the total battery discharge cutoff voltage of 2.8V, and different charge multipliers are used to determine the State of Charge (SOC) at 10%, 20%, 30%...80%. The negative electrode potential corresponding to the charge state (SOC) is recorded, multiplier-negative electrode potential curves for different SOC states are drawn, and after linear fitting, the corresponding charge multiplier is obtained when the negative electrode potential for each SOC state is 0V. This charge multiplier is the charge window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC, respectively. The charging time T for the secondary battery to charge from 10%SOC to 80%SOC is calculated based on the formula (60 / C20%SOC+60 / C30%SOC+60 / C40%SOC+60 / C50%SOC+60 / C60%SOC+60 / C70%SOC+60 / C80%SOC)×10%. A shorter charging time T indicates better rapid charging performance of the secondary battery.

[0203] Test results

[0204] Table 4 shows the effects of this invention on improving the cycle performance and rapid charging performance of secondary batteries.

[0205] [Table 4]

[0206] As can be seen from Table 4, if the porosity of the separator in Comparative Example 1 is too small, the movement speed of lithium ions during the process of passing through the separator will decrease, which may worsen the rapid charging capability of the secondary battery. The solid-phase transmission speed of lithium ions can be adjusted by synergistically adjusting the porosity of the separator of the secondary battery and the mass percentage content of the film-forming additive. The liquid-phase transmission speed of lithium ions can be adjusted by adjusting the viscosity of the electrolyte. Compared to Comparative Example 2, in Examples 1 to 2-8, by synergistically adjusting the porosity of the separator, the mass percentage content of the film-forming additive, and the viscosity of the electrolyte so that 4≦(b*ε) / c≦240, and especially 4≦(b*ε) / c≦180, the overall transmission speed of lithium ions in the solid and liquid phases can be significantly improved, thereby improving the rapid charging capability of the secondary battery. Furthermore, by forming a film on the surface of the negative electrode active material with additives in the electrolyte, the protective performance of the negative electrode active material can be improved, thereby improving the cycle performance of the secondary battery.

[0207] In Examples 3-1 to 3-7, by adjusting the mass percentage content b1% of the negative electrode film-forming additive, the protective capacity for the negative electrode active material can be adjusted when 1 ≤ b2 / b1 ≤ 60, and especially when 1 ≤ b2 / b1 ≤ 40, thereby improving the cycle performance of the secondary battery.

[0208] In Examples 4-1 to 4-7, by adjusting the mass percentage content b1% of the positive electrode film-forming additive, the protective capacity for the positive electrode active material can be adjusted when 1 ≤ b2 / b1 ≤ 60, and especially when 1 ≤ b2 / b1 ≤ 40, thereby improving the cycle performance of the secondary battery.

[0209] In Examples 5-1 and 5-3, the overall migration rate of lithium ions can be adjusted by adjusting the mass percentage content a% of the first organic solvent, thereby improving the kinetic performance of the secondary battery when 2 ≤ c + 2 * a% ≤ 8.

[0210] While the present application has been described with reference to preferred embodiments, various improvements are possible, or some components may be replaced with equivalents, without departing from the scope of the application. In particular, the technical features mentioned in each embodiment can be combined in any way, provided that there is no structural inconsistency. The present application is not limited to the specific embodiments disclosed herein, but includes all technical concepts included in the claims.

Claims

1. A secondary battery, A positive electrode sheet containing a positive electrode active material, A negative electrode sheet containing a negative electrode active material, A separator is provided between the positive electrode sheet and the negative electrode sheet, The system comprises an electrolyte containing a first organic solvent and a film-forming additive disposed to form an interfacial film on the surfaces of the positive electrode active material and the negative electrode active material, When the porosity of the separator is ε%, the mass percentage content of the film-forming additive relative to the total mass of the electrolyte is b%, and the viscosity of the electrolyte at 25°C is c (mPa·s), Satisfying 4 ≤ (b * ε) / c ≤ 240, The aforementioned film-forming additive is A negative electrode film forming additive disposed to form an interfacial film on the surface of the negative electrode active material, wherein the negative electrode film forming additive has a mass percentage content of b1% relative to the total mass of the electrolyte, A positive electrode film-forming additive disposed to form an interfacial film on the surface of the positive electrode active material, comprising a positive electrode film-forming additive whose mass percentage content relative to the total mass of the electrolyte is b2%, The positive electrode film-forming additive comprises a carbonate-based additive and a sulfate ester-based additive. The aforementioned secondary battery satisfies 1 ≤ b² / b1 ≤ 60 and 1.40 ≤ b² ≤ 7. Secondary battery.

2. The secondary battery according to claim 1, further satisfying at least one of conditions (1) to (3). (1) 25 ≤ ε ≤ 55. (2) 0.1 ≤ b ≤ 8. (3) 1 ≤ c ≤ 6.

3. When the mass percentage content of the first organic solvent relative to the total mass of the electrolyte is a%, The secondary battery according to claim 1, wherein the secondary battery further satisfies 2 ≤ c + 2 * a / 100 ≤ 8.

4. A secondary battery according to claim 1, wherein 60 ≤ a ≤ 90.

5. The secondary battery according to claim 1, wherein the first organic solvent comprises one or more of the following: a linear carbonate solvent, a carboxylic acid ester solvent, and a nitrile solvent.

6. The secondary battery according to claim 1, wherein the secondary battery satisfies 1 ≤ b2 / b1 ≤ 40.

7. The secondary battery according to claim 1, wherein 0.01 ≤ b1 ≤ 1.

5.

8. The secondary battery according to claim 1, wherein the negative electrode film forming additive includes one or more types selected from boron-containing lithium salt, phosphorus-containing lithium salt, and sulfur-containing lithium salt.

9. The electrolyte further contains a lithium salt, the lithium salt being lithium hexafluorophosphate (LiPF) ６ The secondary battery according to claim 1, comprising one or more types of bisfluorosulfonylimide lithium LiFSI and bistrifluoromethylsulfonylimide lithium LiTFSI.

10. The secondary battery according to claim 1, wherein the separator comprises a base layer and a coating layer provided on the surface of the base layer, the base material of the base layer comprises one or more types selected from polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide, and / or the coating layer comprises a ceramic coating layer and / or a polymer coating layer.

11. A battery module comprising the secondary battery described in claim 1.

12. A battery pack comprising the battery module described in claim 11.

13. A power consumption device comprising a secondary battery according to claim 1, a battery module according to claim 11, or a battery pack according to claim 12.

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