Battery module, secondary battery, and electric device

Abstract

The invention provides a battery assembly which is characterized by comprising a cation supplementing agent, and the decomposition potential of the cation supplementing agent is smaller than or equal to 5V. When the battery assembly is applied to a secondary battery, the cation supplementing agent is decomposed during charging and discharging, so that cations can be provided in a battery system. When the content of cations is increased, the transmission of lithium ions is promoted, so that the attenuation of the battery capacity can be reduced, and the capacity retention ratio of the battery is improved.

Description

Battery assembly, secondary battery, and electrical device Technical Field

[0001] The present application relates to the field of secondary batteries, and in particular to a battery assembly, a secondary battery, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] During the charge and discharge process of secondary batteries, lithium ions are transported back and forth between the positive and negative electrodes. However, due to factors such as the formation of the solid electrolyte interface film (SEI film) and the side reactions inside the battery, the transmission efficiency of lithium ions may be reduced, causing the battery capacity to decay, thereby restricting the improvement of the secondary battery capacity retention rate.

[0004] Summary of the Invention

[0005] Based on the above problems, the present application provides a battery assembly, which includes a cation replenisher, and the decomposition potential of the cation replenisher is ≤5V.

[0006] The battery assembly provided herein includes a cation replenisher with a decomposition potential of 5V or less. When the battery assembly is used in a secondary battery, the cation replenisher decomposes during charge and discharge, thereby providing cations within the battery system. When the cation content increases, it promotes lithium ion transport, thereby reducing battery capacity decay and improving battery capacity retention.

[0007] In some embodiments, the decomposition potential of the cation replenisher is 2V to 5V.

[0008] In some embodiments, the cation replenisher includes at least one of oxides of Group IA elements, peroxides of Group IA elements, oxalates of Group IA elements, oxides of Group IA elements, peroxides of Group IA elements, and oxalates of Group IA elements.

[0009] In some embodiments, the cation replenisher includes at least one of sodium oxide, sodium peroxide, sodium oxalate, potassium oxide, potassium peroxide, potassium oxalate, magnesium oxide, magnesium peroxide, magnesium oxalate, calcium oxide, calcium peroxide, calcium oxalate, strontium oxide, strontium peroxide, and strontium oxalate.

[0010] In some embodiments, the battery assembly includes a positive electrode sheet or a separator.

[0011] In some embodiments, the battery assembly includes a positive electrode sheet; the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the cation replenisher.

[0012] In some embodiments, the mass percentage of the cation-supplementing agent is 0.5% to 15% based on the mass percentage of the positive electrode film layer.

[0013] In some embodiments, the thickness of the positive electrode film layer is 50 μm to 300 μm.

[0014] In some embodiments, the positive electrode film layer includes a positive electrode active layer and a first cation-supplementing layer, the first cation-supplementing layer is located on at least one surface of the positive electrode active layer, and the first cation-supplementing layer includes the cation-supplementing agent.

[0015] In some embodiments, the first cation-supplementing layer is located on a surface of the positive electrode active layer away from the positive electrode current collector.

[0016] In some embodiments, the first cation-compensating layer further includes a first binder. In the first cation-compensating layer, the mass ratio of the cation-compensating agent to the first binder is 99.9:0.1 to 1:99.

[0017] In some embodiments, the mass ratio of the cation supplementing agent to the first binder is 97:3 to 80:20.

[0018] In some embodiments, the first binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0019] In some embodiments, the first cation-supplementing layer is further away from the positive electrode current collector than the positive electrode active layer.

[0020] In some embodiments, the thickness of the first cation-supplementing layer is 1 μm to 30 μm.

[0021] In some embodiments, the battery assembly includes a separator; the separator includes a base film and a second cation-compensating layer located on at least one surface of the base film, wherein the second cation-compensating layer includes the cation-compensating agent.

[0022] In some embodiments, the mass percentage of the cation replenisher is 10% to 90% based on the mass percentage of the isolation membrane.

[0023] In some embodiments, the second cation-compensating layer further includes a second binder. In the second cation-compensating layer, the mass ratio of the cation-compensating agent to the second binder is 99.9:0.1 to 1:99.

[0024] In some embodiments, the mass ratio of the cation supplementing agent to the first binder is 97:3 to 80:20.

[0025] In some embodiments, the second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0026] In some embodiments, the second cation-supplementing layer has a thickness of 1 nm to 10 μm.

[0027] The present application also provides a secondary battery, comprising the battery assembly.

[0028] In some embodiments, the secondary battery includes the battery assembly, and at least one second cation-supplementing layer is present in the separator and is located between the base film and the positive electrode sheet of the secondary battery.

[0029] In some embodiments, the electrolyte of the secondary battery contains the cation replenisher, and the mass percentage of the cation replenisher in the electrolyte is 1% to 50%.

[0030] The present application also provides an electrical device comprising the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. 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 inventive effort.

[0032] FIG1 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0033] FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .

[0034] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0035] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0036] FIG5 is an exploded view of the battery pack shown in FIG4 according to an embodiment of the present application.

[0037] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0038] Explanation of the accompanying symbols: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. secondary battery; 51. casing; 52. electrode assembly; 53. cover plate; 6. electrical device.

[0039] In order to better describe and illustrate the embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed inventions, the presently described embodiments and / or examples, and any of the best modes currently understood for these inventions. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0046] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0047] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true or present, and B is false or absent; A is false or absent, and B is true or present; or both A and B are true, or both A and B are present.

[0048] Unless otherwise indicated, the terms used in this application have the commonly understood meanings generally understood by those skilled in the art. Unless otherwise indicated, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art. For example, the tests can be performed using the methods described in the examples of this application.

[0049] One embodiment of the present application provides a battery assembly. The battery assembly includes a cation replenisher having a decomposition potential of 5V or less. When the battery assembly is used in a secondary battery, the cation replenisher decomposes during charge and discharge, thereby providing cations within the battery system. When the cation content increases, it promotes lithium ion transport, thereby reducing battery capacity decay and improving battery capacity retention.

[0050] During the charge and discharge process of the battery, lithium ions are transported back and forth between the positive electrode and the negative electrode, and then embedded and de-embedded back and forth between the positive electrode and the negative electrode. Among them, during the charge and discharge process, there is a certain amount of lithium ions in the battery system that do not participate in embedding and de-embedding, which will cause a certain bottleneck in the transmission efficiency of lithium ions. In this application, by adding a cation supplement, when the cation content in the battery system increases, based on the principle of kinetics, this part of the lithium ions that do not participate in embedding and de-embedding can be transported to the positive electrode and the negative electrode, promoting the embedding and de-embedding of this part of the lithium ions between the positive electrode and the negative electrode, which can improve the transmission efficiency of lithium ions and improve the capacity retention rate of the battery.

[0051] In this application, the decomposition potential refers to the potential corresponding to the cation replenisher being oxidized and losing electrons in the battery assembly. The decomposition potential can be measured by the following method: prepare an electrode including a cation replenisher, the current collector in the electrode electrode can be a platinum foil, and the electrode can also include a PVDF binder and conductive carbon black. The prepared electrode is used as the working electrode, metallic lithium is used as the counter electrode, and the electrolyte uses a conventional electrolyte for lithium-ion batteries to assemble into a battery. Then a linear sweep cyclic voltammetry test is performed. When the current is ≥0.1mA, it is considered that the cation replenisher begins to decompose, and the potential corresponding to the current of 0.1mA is used as the decomposition potential of the cation replenisher.

[0052] In some embodiments, the decomposition potential of the cation replenisher is 2 V to 5 V. Alternatively, the decomposition potential of the cation replenisher is 2 V, 2.2 V, 2.5 V, 2.8 V, 3 V, 3.2 V, 3.5 V, 3.8 V, 4 V, 4.2 V, 4.5 V, 4.8 V, 4.9 V, 5 V, etc.

[0053] Some optional examples of cation-supplementing agents include at least one of oxides of Group IA elements, peroxides of Group IA elements, oxalates of Group IA elements, oxides of Group IIA elements, peroxides of Group IIA elements, and oxalates of Group IIA elements. These cation-supplementing agents are widely available and easily accessible, facilitating their widespread use in battery components.

[0054] In some embodiments, the cation-supplementing agent includes at least one of sodium oxide, sodium peroxide, sodium oxalate, potassium oxide, potassium peroxide, potassium oxalate, magnesium oxide, magnesium peroxide, magnesium oxalate, calcium oxide, calcium peroxide, calcium oxalate, strontium oxide, strontium peroxide and strontium oxalate. Compared with the traditional method of directly supplementing lithium ions with positive electrode active materials such as lithium iron phosphate as lithium supplement materials, these embodiments promote the transmission of lithium ions in the battery by cations such as sodium ions, potassium ions, magnesium ions, calcium ions and strontium ions, providing a new idea for improving the battery capacity retention rate. In addition, after the cation-supplementing agent decomposes, the anions can provide electrons for the battery system, which is conducive to further improving the performance of the battery. At the same time, compared with adding positive electrode active materials such as lithium iron phosphate to supplement lithium, the cost of the cation-supplementing agent is lower, which is conducive to reducing the raw material cost of the battery.

[0055] As some optional examples of the battery assembly, the battery assembly includes a positive electrode sheet or a separator.

[0056] For example, the battery component is a positive electrode. That is, the present application provides a positive electrode. The positive electrode includes a cation-supplementing agent, and the decomposition potential of the cation-supplementing agent is ≤5V. Optionally, the decomposition potential of the cation-supplementing agent is 2V to 5V. Optionally, the cation-supplementing agent includes at least one of oxides of Group IA elements, peroxides of Group IA elements, oxalates of Group IA elements, oxides of Group IA elements, peroxides of Group IA elements, and oxalates of Group IA elements. Further optionally, the cation-supplementing agent includes at least one of sodium oxide, sodium peroxide, sodium oxalate, potassium oxide, potassium peroxide, potassium oxalate, magnesium oxide, magnesium peroxide, magnesium oxalate, calcium oxide, calcium peroxide, calcium oxalate, strontium oxide, strontium peroxide, and strontium oxalate.

[0057] For another example, the battery component is a separator. That is, the present application provides a separator. The separator includes a cation-replenishing agent, and the decomposition potential of the cation-replenishing agent is ≤5V. Optionally, the decomposition potential of the cation-replenishing agent is 2V to 5V. Optionally, the cation-replenishing agent includes at least one of an oxide of a Group IA element, a peroxide of a Group IA element, an oxalate of a Group IA element, an oxide of a Group IA element, a peroxide of a Group IA element, and an oxalate of a Group IA element. Further optionally, the cation-replenishing agent includes at least one of sodium oxide, sodium peroxide, sodium oxalate, potassium oxide, potassium peroxide, potassium oxalate, magnesium oxide, magnesium peroxide, magnesium oxalate, calcium oxide, calcium peroxide, calcium oxalate, strontium oxide, strontium peroxide, and strontium oxalate.

[0058] In some embodiments, the battery assembly includes a positive electrode sheet; the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, the positive electrode film layer including a cation replenisher. Optionally, the battery assembly is a positive electrode sheet.

[0059] Optionally, the mass percentage of the cation-supplementing agent is 0.5% to 15% based on the mass percentage of the positive electrode film layer. For example, the mass percentage of the cation-supplementing agent is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. If the mass percentage of the cation-supplementing agent is too small, the improvement effect may not be obvious. If the mass percentage of the cation-supplementing agent is too large, the content of the active material may be reduced, resulting in a decrease in the energy density of the battery. In addition, if the mass percentage of the cation-supplementing agent is too large, too many additional cations may be introduced, and the problem of poor performance improvement may also occur.

[0060] Optionally, the thickness of the positive electrode film layer is 50 μm to 300 μm. For example, the thickness of the positive electrode film layer is 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc.

[0061] It is understood that the positive electrode film layer includes a cation-supplementing agent, and the cation-supplementing agent can be distributed in the positive electrode film layer. In this case, when preparing the positive electrode film layer, the cation-supplementing agent is added to the positive electrode slurry, and then coated to obtain a positive electrode film layer including the cation-supplementing agent on the surface of the positive electrode current collector. The preparation method is simple and easy.

[0062] In some embodiments, the positive electrode film layer includes a positive electrode active layer and a first cation-supplementing layer, wherein the first cation-supplementing layer is located on at least one surface of the positive electrode active layer, and the first cation-supplementing layer includes a cation-supplementing agent. In this case, the positive electrode active layer and the first cation-supplementing layer can be prepared separately.

[0063] It is understood that the first cation-replenishing layer being located on at least one surface of the positive electrode active layer means that the first cation-replenishing layer is located between the positive electrode active layer and the positive electrode current collector, and / or the first cation-replenishing layer is located on a surface of the positive electrode active layer that is distal to the positive electrode current collector. Alternatively, the first cation-replenishing layer is further distal to the positive electrode current collector than the positive electrode active layer.

[0064] In some embodiments, the first cation-replenishing layer further includes a first binder. In the first cation-replenishing layer, the mass ratio of the cation-replenishing agent to the first binder is 99.9:0.1 to 1:99. By providing the first binder, the bonding force between the first cation-replenishing layer and the positive electrode current collector and / or the positive electrode active layer can be improved to form a positive electrode sheet with a more stable structure. In addition, in the secondary battery, the provision of the first binder can increase the bonding between the positive electrode sheet and the separator, reducing the risk of deformation such as wrinkling of the sheet. In the first cation-replenishing layer, if the mass ratio of the cation-replenishing agent to the first binder is too large, the bonding may be reduced. If the mass ratio of the cation-replenishing agent to the first binder is too small, the cation-replenishing agent may have a small effect on the improvement of the battery capacity retention rate. Optionally, in the first cation-supplementing layer, the mass ratio of the cation-supplementing agent to the first binder may be, but is not limited to, 99:1, 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60, 35:65, 30:70, 25:75, 20:80, 15:85, 10:90, 5:95, 1:99, etc. Further optionally, the mass ratio of the cation-supplementing agent to the first binder is 97:3 to 80:20.

[0065] As some optional examples of the first binder, the first binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0066] It is understood that the positive electrode active layer also includes a positive electrode binder. Optionally, the positive electrode binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. Further optionally, the first binder and the positive electrode binder in the positive electrode active layer may be the same or different.

[0067] In some embodiments, the thickness of the first cation-compensating layer is 1 μm to 30 μm. Optionally, the thickness of the first cation-compensating layer is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, etc. When the thickness of the first cation-compensating layer is too large, it may cause the overall thickness of the positive electrode plate to increase, thereby increasing the volume of the battery. When the thickness of the positive electrode plate remains unchanged, if the thickness of the first cation-compensating layer is too large, it may cause the thickness of the positive electrode active layer to decrease, thereby reducing the amount of positive electrode active material used, and further causing the capacity of the battery to decrease. When the thickness of the first cation-compensating layer is too small, the degree of improvement in the battery capacity retention rate is small.

[0068] In some embodiments, the battery component includes a separator; the separator includes a base film and a second cation-compensating layer located on at least one surface of the base film, the second cation-compensating layer including a cation-compensating agent. Optionally, the battery component is a separator.

[0069] Optionally, the mass percentage of the cation-supplementing agent is 10% to 90% based on the mass percentage of the separator. Further, optionally, the mass percentage of the cation-supplementing agent is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc. based on the mass percentage of the separator.

[0070] In some embodiments, the second cation-compensating layer further includes a second binder. In the second cation-compensating layer, the mass ratio of the cation-compensating agent to the second binder is 99.9:0.1 to 1:99. By providing the second binder, the bonding force between the second cation-compensating layer and the base film can be improved to form a more structurally stable isolation membrane. In addition, in the secondary battery, the provision of the second binder can increase the bonding between the positive electrode plate and the isolation membrane, reducing the risk of deformation such as wrinkling of the plate. In the second cation-compensating layer, if the mass ratio of the cation-compensating agent to the second binder is too large, it may lead to reduced bonding. If the mass ratio of the cation-compensating agent to the second binder is too small, the cation-compensating agent may have a small effect on improving the battery capacity retention rate. Further optionally, in the second cation-suppressing layer, the mass ratio of the cation-suppressing agent to the second binder can be, but is not limited to, 99:1, 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60, 35:65, 30:70, 25:75, 20:80, 15:85, 10:90, 5:95, 1:99, etc. Further optionally, the mass ratio of the cation-suppressing agent to the second binder is 97:3 to 80:20.

[0071] Alternatively, the second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. Optionally, the second binder may be the same as or different from the positive electrode binder in the positive electrode active layer.

[0072] In some embodiments, the thickness of the second cation-compensating layer is 1 nm to 10 μm. Optionally, the thickness of the second cation-compensating layer is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. When the thickness of the second cation-compensating layer is too large, the overall thickness of the separator may increase, thereby increasing the volume of the battery. When the thickness of the positive electrode sheet remains unchanged, if the thickness of the second cation-compensating layer is too large, the thickness of the base film may decrease, and the strength of the separator may decrease. When the thickness of the second cation-compensating layer is too small, the improvement in the battery capacity retention rate is small.

[0073] It is understood that the base film of the separator can be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can 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 can be the same or different, without particular limitation.

[0074] Another embodiment of the present application provides a secondary battery comprising the above-mentioned battery assembly.

[0075] Optionally, the secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The separator is disposed between the positive and negative electrode sheets, and the electrolyte conducts ions between the positive and negative electrode sheets. The positive electrode sheet can be selected from the aforementioned positive electrode sheets, and / or the separator can be selected from the aforementioned separators.

[0076] In some embodiments, the secondary battery includes at least one second cation-supplementing layer within the separator, positioned between the base film and the secondary battery's positive electrode. In this case, the presence of the first cation-supplementing layer within the separator, facing the positive electrode, further enhances the cation-supplementing agent's effectiveness and improves the battery's capacity retention.

[0077] In some embodiments, the electrolyte of the secondary battery contains a cation-supplementing agent, and the mass percentage of the cation-supplementing agent is 1% to 50% by mass of the electrolyte. If the mass percentage of the cation-supplementing agent in the electrolyte is too small, the performance improvement is poor. If the mass percentage of the cation-supplementing agent in the electrolyte is too large, it may have a certain impact on the balance inside the battery and may also cause the problem of poor performance improvement. Optionally, the mass percentage of the cation-supplementing agent in the electrolyte is 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0078] Another embodiment of the present application provides a battery module, which includes the aforementioned secondary battery.

[0079] Another embodiment of the present application provides a battery pack, which includes the aforementioned secondary battery or the aforementioned battery module.

[0080] Another embodiment of the present application provides an electric device, comprising at least one of the aforementioned secondary battery, the aforementioned battery module, and the aforementioned battery pack. Optionally, the electric device comprises the aforementioned secondary battery.

[0081] The secondary battery, battery module, battery pack, and electric device of the present application are described below with reference to the accompanying drawings as appropriate.

[0082] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0083] Positive electrode

[0084] 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, wherein the positive electrode film layer includes a positive electrode active material.

[0085] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0086] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. Alternatively, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. Alternatively, the polymer material substrate may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0087] As an example, the positive electrode active material may include positive electrode active materials for batteries that are well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to 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 their modified compounds. Optionally, lithium cobalt oxide includes LiCoO2. Lithium nickel oxide includes LiNiO2. Lithium manganese oxide includes at least one of LiMnO2 and LiMn2O4. Lithium nickel cobalt manganese oxide includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 ) and LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ) at least one of. Lithium nickel cobalt aluminum oxide includes LiNi 0.85 Co 0.15 Al 0.05O2. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of 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, and a composite material of lithium manganese iron phosphate and carbon. Optionally, the lithium iron phosphate includes LiFePO4 (LFP). The lithium manganese phosphate includes LiMnPO4. The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight percent, based on the total weight of the positive electrode film layer.

[0088] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20 weight%, based on the total weight of the positive electrode film layer.

[0089] In some embodiments, the positive electrode film layer may also optionally include a conductive agent. For example, 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. The weight ratio of the conductive agent in the positive electrode film layer is 0 to 20% by weight, based on the total weight of the positive electrode film layer.

[0090] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry. Optionally, the solvent includes N-methylpyrrolidone. The positive electrode slurry has a solid content of 40 to 80 wt %, and the viscosity at room temperature is adjusted to 5000 to 25000 mPa·s. The positive electrode slurry is coated on the surface of the positive electrode current collector, dried, and then cold-pressed by a cold rolling mill to form a positive electrode sheet; the positive electrode powder coating unit surface density is 150-350 mg / m 2 The compaction density of the positive electrode is 3.0-3.6g / cm 3 , optional 3.3-3.5g / cm 3 The calculation formula of the compaction density is: compaction density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0091] It is understandable that the positive electrode sheet in the embodiment of the present application can be made by using the above-mentioned positive electrode sheet as the positive electrode sheet body and forming a solid electrolyte interface film on the surface of the positive electrode sheet body.

[0092] Negative electrode

[0093] 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, wherein the negative electrode film layer includes a negative electrode active material.

[0094] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material on a polymer base material. Optionally, the metal material includes at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0096] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100 weight %, based on the total weight of the negative electrode film layer.

[0097] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0 to 30% by weight, based on the total weight of the negative electrode film layer.

[0098] In some embodiments, the negative electrode film layer may further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight, based on the total weight of the negative electrode film layer.

[0099] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener. The weight ratio of the other additives in the negative electrode film layer is 0 to 15% by weight, based on the total weight of the negative electrode film layer. Optionally, the thickener includes sodium carboxymethylcellulose (CMC-Na).

[0100] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a negative electrode slurry. Optionally, the solvent includes deionized water. The solid content of the negative electrode slurry is 30 to 70 wt%, and the viscosity at room temperature is adjusted to 2000 to 10000 mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing, such as rolling, is performed to obtain a negative electrode sheet. The negative electrode powder coating unit area density is 75 to 220 mg / m 2 , the compaction density of the negative electrode is 1.2~2.0g / m 3 .

[0101] It can be understood that the negative electrode sheet in the embodiment of the present application can be made by using the above-mentioned negative electrode sheet as the negative electrode sheet body and forming a solid electrolyte interface film on the surface of the negative electrode sheet body.

[0102] electrolytes

[0103] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0104] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0105] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP). The concentration of the electrolyte salt is typically 0.5 to 5 mol / L.

[0106] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0107] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0108] Isolation film

[0109] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0110] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0111] In some embodiments, the isolation membrane includes a base membrane and a modified layer located on at least one surface of the base membrane. The base membrane can be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the base membrane is a multi-layer composite film, the materials of the layers can be the same or different, without particular limitation. Optionally, the modified layer includes the aforementioned second cation-supplementing layer.

[0112] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0113] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0114] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate. This application does not particularly limit the shape of the secondary battery, which can be cylindrical, square, or any other shape. For example, Figure 1 shows a secondary battery 5 with a square structure as an example.

[0115] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0116] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0117] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0118] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0119] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0120] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0121] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0122] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0123] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0124] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0125] Example

[0126] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0127] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0128] Example 1

[0129] The battery components in Examples 1-1 to 1-13 are positive electrode sheets.

[0130] Example 1-1

[0131] Preparation method of the positive electrode sheet in this embodiment:

[0132] A positive electrode slurry was prepared by adding a cation-supplementing agent, lithium iron phosphate positive electrode active material, Super P conductive agent, and PVDF binder to an NMP solvent in a mass ratio of 5:90:2:3. The solid content of the positive electrode slurry was 50 wt%. The positive electrode slurry was coated onto aluminum foil, dried at 85°C, and then cold-pressed. The foil was then trimmed and cut into pieces, and then dried under vacuum at 85°C for 4 hours to produce positive electrode sheets. The cation-supplementing agent accounted for 5% by mass of the positive electrode film layer. The thickness of the positive electrode film layer was 150 μm.

[0133] Example 1-2 to Example 1-13.

[0134] Compared to Example 1-1, Examples 1-2 to 1-13 differ in the cation-supplementing agent, its mass percentage in the positive electrode film layer, and the thickness of the positive electrode film layer. The details are shown in Table 1. In Table 1, W1 represents the mass percentage of the cation-supplementing agent in the positive electrode film layer.

[0135] Comparative Example 1

[0136] Compared with Example 1-1, the difference in Comparative Example 1 is that potassium oxalate is replaced by calcium fluoride, as shown in Table 1.

[0137] Table 1

[0138] Example 2

[0139] The battery components in Examples 2-1 to 2-10 are positive electrode sheets.

[0140] Example 2-1

[0141] Preparation method of the positive electrode sheet in this embodiment:

[0142] LiFePO4 positive electrode active material, Super P conductive agent, and PVDF binder were added to NMP solvent in a mass ratio of 95:3:2 to obtain a positive electrode slurry, and the solid content of the positive electrode slurry was 50 wt%.

[0143] Potassium oxalate cation-supplementing agent and PVDF binder were added to NMP solvent in a mass ratio of 90:10 to obtain a first cation-supplementing slurry.

[0144] The first cation-supplementing slurry and the positive electrode slurry were sequentially coated on aluminum foil, dried at 85°C, and then cold-pressed. The foil was then trimmed and cut into pieces, and dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet.

[0145] In the positive electrode sheet, the first cation-supplementing layer is located between the positive electrode current collector and the positive electrode active layer. The thickness of the first cation-supplementing layer is 10 μm, the thickness of the positive electrode film layer is 150 μm, and the mass percentage of the cation-supplementing agent in the positive electrode film layer is 5%.

[0146] Example 2-2 to Example 2-5.

[0147] Compared with Example 2-1, Examples 2-2 to 2-5 differ in that the thickness of the first cation-supplementing layer is different, as shown in Table 2.

[0148] Examples 2-6

[0149] Compared with Example 2-1, Example 2-6 differs in that, when preparing the positive electrode sheet, the positive electrode slurry and the first cation-supplementing slurry are sequentially coated on the aluminum foil. In the positive electrode sheet, the positive electrode active layer is located between the positive electrode current collector and the first cation-supplementing layer.

[0150] Example 2-7 to Example 2-10.

[0151] Compared with Example 2-6, Examples 2-7 to 2-10 differ in that the thickness of the first cation-supplementing layer is different, as shown in Table 2.

[0152] Table 2

[0153] Example 3

[0154] The battery components of Examples 3-1 to 3-15 are separators.

[0155] Example 3-1

[0156] The preparation method of the isolation film in this embodiment is as follows:

[0157] Potassium oxalate cation-supplementing agent and PVDF binder were added to NMP solvent in a mass ratio of 50:50 to obtain a second cation-supplementing slurry.

[0158] A 16-μm-thick polyethylene film was used as the base film. A second cation-supplementing slurry was applied to one surface of the base film and dried under vacuum at 60°C to produce a separator. The separator consisted of the base film and a second cation-supplementing layer located on the surface of the base film. The second cation-supplementing layer had a thickness of 2 μm. The cation-supplementing agent accounted for 60% of the separator by weight.

[0159] Example 3-2 to Example 3-15.

[0160] Compared with Example 3-1, Examples 3-2 to 3-15 differ in the cation-supplementing agent, its mass percentage in the separator, and the thickness of the second cation-supplementing layer, as shown in Table 3. In Table 3, W2 represents the mass percentage of the cation-supplementing agent in the separator.

[0161] Table 3

[0162] Example 4

[0163] Examples 4-1 to 4-13 employed different electrolytes. The electrolyte consisted of a 1 mol / L lithium hexafluorophosphate solution containing a mixture of EC and DMC in a 1:1 volume ratio. The electrolyte also contained a cation replenisher. The type and mass percentage of the cation replenisher in the electrolyte are shown in Table 4.

[0164] Table 4

[0165] Test Case

[0166] (1) Preparation method of basic positive electrode sheet:

[0167] Lithium iron phosphate positive electrode active material, Super P conductive agent, and PVDF binder were added to NMP solvent in a mass ratio of 95:3:2 to prepare a positive electrode slurry with a solid content of 50 wt%. The positive electrode slurry was coated on aluminum foil, dried at 85°C, and then cold-pressed. The foil was then trimmed and cut into pieces, and then dried at 85°C under vacuum for 4 hours to produce a basic positive electrode sheet.

[0168] (2) Preparation method of basic negative electrode sheet:

[0169] The graphite anode active material, Super P conductive agent, styrene-butadiene rubber (SBR) binder, and CMC-Na thickener were dispersed in deionized water at a mass ratio of 90:2:3:1.5:1.5 and mixed evenly to produce anode slurry. The anode slurry was coated onto anode current collector copper foil and dried at 85°C. The resulting sheet was then cold-pressed, trimmed, and cut into pieces, and then dried at 120°C under vacuum for 12 hours to form the base anode sheet.

[0170] (3) Basic isolation membrane:

[0171] A polyethylene film with a thickness of 16 μm was selected as the base isolation film.

[0172] (4) Basic electrolyte:

[0173] A 1 mol / L lithium hexafluorophosphate solution, wherein the solvent is a mixed solvent of EC and DMC, and the volume ratio of EC to DMC is 1:1.

[0174] (5) Preparation of batteries:

[0175] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to isolate the positive and negative electrodes. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer package and injected with electrolyte. After packaging and standing, the cell is formed and then shaped to prepare a lithium-ion battery.

[0176] The positive electrode sheet is one of Example 1 and / or Example 2 and / or the basic positive electrode sheet, the isolation membrane is one of Example 3 and / or the basic isolation membrane, the negative electrode sheet is the basic negative electrode sheet, and the electrolyte is the electrolyte and / or the basic electrolyte in Example 4.

[0177] Battery cycling performance was tested at 45°C using a 0.5C / 0.5C constant current charge / discharge method over a voltage range of 2.5V to 3.65V. The battery capacity retention after 200 cycles is shown in Tables 1 to 5.

[0178] Among them, the positive electrode sheets of the corresponding batteries in Table 1 are respectively the positive electrode sheets in Examples 1-1 to 1-13 and Comparative Example 1, the isolation membrane is the basic isolation membrane, the negative electrode sheet is the basic negative electrode sheet, and the electrolyte is the basic electrolyte.

[0179] The positive electrode sheets of the corresponding batteries in Table 2 are respectively the positive electrode sheets in Examples 2-1 to 2-10, the separator is the basic separator, the negative electrode sheet is the basic negative electrode sheet, and the electrolyte is the basic electrolyte.

[0180] The corresponding batteries in Table 3 have the same positive electrode as the base positive electrode, the same separators as in Examples 3-1 to 3-15, the same negative electrode as the base negative electrode, and the same electrolyte as the base electrolyte. "The second cation-supplementing layer faces the positive electrode" indicates that the second cation-supplementing layer of the separator in the battery is positioned toward the positive electrode.

[0181] The positive electrode sheet of the corresponding battery in Table 4 is the basic positive electrode sheet, the isolation membrane is the basic isolation membrane, the negative electrode sheet is the basic negative electrode sheet, and the electrolytes are the electrolytes of Examples 4-1 to 4-13 respectively.

[0182] Comparative Example 2

[0183] In Comparative Example 2, the corresponding battery has a positive electrode sheet that is a basic positive electrode sheet, a separator that is a basic separator, a negative electrode sheet that is a basic negative electrode sheet, and an electrolyte that is a basic electrolyte. The battery has a capacity retention rate of 76%.

[0184] As can be seen from Tables 1 and 4, compared to batteries consisting of a basic positive electrode sheet, a basic separator, and a basic electrolyte, the battery exhibits better capacity retention when at least one of the positive electrode sheet, separator, and electrolyte includes a cation-supplementing agent with a decomposition potential of 5V or less. Furthermore, when the separator includes a second cation-supplementing layer, with the second cation-supplementing layer positioned toward the positive electrode sheet, the battery exhibits even better capacity retention.

[0185] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0186] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A battery assembly, characterized in that: It includes a cation replenisher, wherein the decomposition potential of the cation replenisher is ≤5V; Optionally, the decomposition potential of the cation replenisher is 2V to 5V.

2. The battery assembly according to claim 1, characterized in that: The cation supplement includes at least one of oxides of group IA elements, peroxides of group IA elements, oxalates of group IA elements, oxides of group IA elements, peroxides of group IA elements, and oxalates of group IA elements; Optionally, the cation supplement includes at least one of sodium oxide, sodium peroxide, sodium oxalate, potassium oxide, potassium peroxide, potassium oxalate, magnesium oxide, magnesium peroxide, magnesium oxalate, calcium oxide, calcium peroxide, calcium oxalate, strontium oxide, strontium peroxide and strontium oxalate.

3. The battery pack according to any one of claims 1 to 2, characterized in that: The battery assembly includes a positive electrode sheet or a separator.

4. The battery assembly according to any one of claims 1 to 3, characterized in that: The battery assembly includes a positive electrode plate; the positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the cation replenisher.

5. The battery assembly according to claim 4, characterized in that: Calculated by the mass percentage of the positive electrode film layer, the mass percentage of the cation supplement agent is 0.5% to 15%.

6. The battery assembly according to any one of claims 4 to 5, characterized in that: The thickness of the positive electrode film layer is 50 μm to 300 μm.

7. The battery assembly according to any one of claims 4 to 6, characterized in that: The positive electrode film layer comprises a positive electrode active layer and a first cation-supplementing layer, wherein the first cation-supplementing layer is located on at least one surface of the positive electrode active layer, and the first cation-supplementing layer comprises the cation-supplementing agent; Optionally, the first cation-supplementing layer is located on a surface of the positive electrode active layer away from the positive electrode current collector.

8. The battery assembly according to claim 7, characterized in that: The first cation-supplementing layer further includes a first binder, and in the first cation-supplementing layer, the mass ratio of the cation-supplementing agent to the first binder is 99.9:0.1 to 1:99; Optionally, the mass ratio of the cation supplement agent to the first binder is 97:3 to 80:20; Optionally, the first binder includes polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene - At least one of a propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

9. The battery assembly according to any one of claims 7 to 8, characterized in that: The first cation-supplementing layer satisfies at least one of the following characteristics (1) to (3): (1) The first cation-supplementing layer is further away from the positive electrode current collector than the positive electrode active layer; (2) The thickness of the first cation-supplementing layer is 1 μm to 30 μm.

10. The battery assembly according to any one of claims 1 to 3, characterized in that: The battery assembly includes a separator; the separator includes a base film and a second cation-compensating layer located on at least one surface of the base film, wherein the second cation-compensating layer includes the cation-compensating agent.

11. The battery assembly according to claim 10, characterized in that: Calculated by the mass percentage of the isolation membrane, the mass percentage of the cation replenisher is 10% to 90%.

12. The battery assembly according to any one of claims 10 to 11, characterized in that: The second cation-supplementing layer further comprises a second binder, and in the second cation-supplementing layer, the mass ratio of the cation-supplementing agent to the second binder is 99.9:0.1 to 1:99; Optionally, the mass ratio of the cation supplement agent to the first binder is 97:3 to 80:20; Optionally, the second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

13. The battery assembly according to any one of claims 10 to 12, characterized in that: The thickness of the second cation-supplementing layer is 1 nm to 10 μm.

14. A secondary battery, characterized in that: A battery assembly comprising the battery assembly according to any one of claims 1 to 15.

15. The secondary battery according to claim 14, characterized in that: The secondary battery comprises the battery assembly according to any one of claims 10 to 13, and at least one second cation-supplementing layer is present in the isolation membrane and is located between the base membrane and the positive electrode plate of the secondary battery.

16. The secondary battery according to claim 14 or 15, characterized in that: The electrolyte of the secondary battery contains the cation replenisher, and the mass percentage of the cation replenisher in the electrolyte is 1% to 50%.

17. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 14 to 16.

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