Current collector and preparation method thereof, pole piece, secondary battery and electric device

Abstract

The invention relates to a current collector and a preparation method thereof, a pole piece, a secondary battery and an electric device. The compact fluoride or oxide is formed on the surface of the current collector in situ to serve as the passivation protection layer, the current collector can be effectively prevented from being continuously corroded by electrolyte in the battery circulation process, then the cycle performance of the battery is improved, and the passivation protection layer effectively improves the safety performance of the battery and does not affect the conductivity of the pole piece at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of battery materials, and in particular to a current collector and a preparation method thereof, a pole piece, a secondary battery and an electrical device. Background Art

[0002] In recent years, as the application scope of lithium-ion batteries has become more and more extensive, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As lithium-ion batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.

[0003] The current collector is prone to corrosion reactions in the electrolyte system. Its corrosion products will consume the positive electrode active materials and contaminate the electrolyte, causing obvious battery self-discharge. Solid corrosion products will also increase battery resistance. Problems such as these will lead to a decrease in battery cycle performance and may even cause battery safety issues in severe cases. Summary of the invention

[0004] The present application provides a corrosion-resistant current collector and a preparation method thereof, as well as a pole piece, a secondary battery and an electrical device using the corrosion-resistant current collector.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a current collector, wherein a passivation protective layer is formed in situ on the surface of the current collector, and the passivation protective layer is an oxide or a fluoride.

[0006] Therefore, the present invention can effectively inhibit the continuous corrosion of the current collector by the electrolyte during the battery cycle process by forming a dense fluoride or oxide as a passivation protective layer in situ on the surface of the current collector, thereby improving the cycle performance of the battery. The passivation protective layer effectively improves the safety performance of the battery without affecting the conductivity of the electrode.

[0007] In some embodiments of the present application, the material of the current collector is aluminum or an aluminum alloy.

[0008] In some embodiments of the present application, the thickness of the current collector is 5 μm to 50 μm.

[0009] In some embodiments of the present application, the passivation protective layer is aluminum oxide or aluminum fluoride. Taking oxygen or fluorine as the characteristic element, combined with SEM electron microscope scanning, it can be observed that the characteristic element is distributed on the surface of the current collector and has obvious stratification with the inner layer current collector material. This result can reflect the compactness of the passivation protective layer.

[0010] In some embodiments of the present application, the thickness of the passivation protective layer is 0.2 μm to 50 μm; optionally, the thickness of the passivation protective layer is 0.2 μm to 10 μm; further optionally, the thickness of the passivation protective layer is 0.5 μm to 3 μm.

[0011] In some embodiments of the present application, the ratio of the thickness of the current collector to the thickness of the passivation protection layer is 2.5 to 300:1; optionally, the thickness ratio is 3 to 70:1.

[0012] In some embodiments of the present application, the passivation protective layer is formed by anodizing the surface of the current collector; wherein:

[0013] The electrolyte used in the anodic oxidation treatment includes an acidic, alkaline or neutral electrolyte; under the action of the anode, the surface of the current collector reacts and forms an oxide on the surface;

[0014] In an optional embodiment, the acidic electrolyte includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30 to 300 g / L, optionally 100 to 200 g / L;

[0015] In an optional embodiment, the alkaline electrolyte includes at least one soluble alkali; optionally, includes at least one of sodium hydroxide, ammonium hydroxide, sodium oxalate, sodium phosphate or sodium silicate; the concentration of all soluble alkalis is 5 to 200 g / L, optionally 20 to 100 g / L.

[0016] In an optional embodiment, the anodizing electrolyte is further selected to include an acidic component and an electrolyte additive; wherein:

[0017] The selection of electrolyte additives includes fluorine-containing electrolyte additives. For example, in some specific embodiments, at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride can be selected; the mass content of the electrolyte additive is: 0-100 g / L; optionally, the mass content is 1-50 g / L.

[0018] The acidic components include at least one soluble acid; optionally, at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids in the anodizing electrolyte is 30-300 g / L, optionally 100-200 g / L.

[0019] Neutral electrolyte salt composition: optionally, including at least one of sodium chloride, citrate, borate, phosphate, silicate or chromate, and the salt concentration is 10 to 300 g / L, optionally 100 to 200 g / L.

[0020] In some embodiments of the present application, the current density of the anodizing treatment is 0.3 to 10 A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

[0021] The second aspect of the present application also provides a method for preparing a current collector, comprising the following steps: anodizing the surface of the current collector to form a passivation protective layer of fluoride or oxide.

[0022] In some embodiments of the present application, the anodizing treatment specifically includes placing a current collector as an anode in an electrolyte for anodizing; the current collector may be aluminum foil or aluminum alloy foil; the current density of the anodizing treatment is 0.3 to 10 A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

[0023] In some embodiments of the present application, the electrolyte used in the anodizing treatment includes an acidic, alkaline, or neutral electrolyte; under the action of the anode, the surface of the current collector reacts and forms an oxide on the surface;

[0024] As an optional embodiment, the anodizing electrolyte is selected as an acidic electrolyte, which includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30 to 300 g / L, optionally 100 to 200 g / L;

[0025] As an optional embodiment, the anodizing electrolyte is selected to be an alkaline electrolyte, which includes at least one soluble alkali; optionally, includes at least one of sodium hydroxide, ammonium hydroxide, sodium oxalate, sodium phosphate or sodium silicate; the concentration of all soluble alkalis is 5 to 200 g / L, optionally 20 to 100 g / L.

[0026] As an optional embodiment, the anodizing electrolyte may include: an acidic component and an electrolyte additive; wherein:

[0027] The selection of electrolyte additives includes fluorine-containing electrolyte additives. For example, in some specific embodiments, at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride can be selected; the mass content of the electrolyte additive is: 0-100 g / L; optionally, the mass content is 1-50 g / L.

[0028] The acidic components include at least one soluble acid; optionally, at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids in the anodizing electrolyte is 30-300 g / L, optionally 100-200 g / L.

[0029] In some embodiments of the present application, a sealing step is further included after the anodizing treatment, and the sealing treatment is one of heat sealing, medium temperature sealing, cold sealing or organic sealing.

[0030] A third aspect of the present application provides a pole piece, comprising the current collector of the present application or the current collector prepared by the preparation method of the present application.

[0031] A fourth aspect of the present application provides a secondary battery, comprising the electrode of the present application.

[0032] A fifth aspect of the present application provides an electrical device, comprising one or more of the electrode of the present application and the secondary battery of the present application.

[0033] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to better describe and illustrate the embodiments or examples provided by the present application, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes of these applications currently understood. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0035] Figure 1 A schematic diagram of a battery cell according to an embodiment of the present application;

[0036] Figure 2 for Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0037] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0038] Figure 4 A schematic diagram of a battery pack according to an embodiment of the present application;

[0039] Figure 5 for Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0040] Figure 6 A schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source;

[0041] Figure 7 The SEM cross-sectional morphology and elemental analysis of comparative example 1 of the present application;

[0042] Figure 8 The SEM cross-sectional morphology and elemental analysis of Example 5 of the present application;

[0043] Fig. 9 The SEM cross-sectional morphology and elemental analysis of Example 16 of the present application;

[0044] Fig.10 The corrosion current test results of comparative example 1 of the present application under different voltage conditions;

[0045] Fig.11 The corrosion current test results of Example 9 of the present application under different voltage conditions;

[0046] Fig.12 These are the corrosion current test results of Example 13 of the present application under different voltage conditions.

[0047] Description of reference numerals:

[0048] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 cover plate; 6 electrical device. DETAILED DESCRIPTION

[0049] Below, some embodiments of the silicon composite material and its preparation method, negative electrode plate, secondary battery and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] The "range" disclosed in the present application can be defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0051] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

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

[0053] If not specifically stated, the terms used in this application have the commonly known meanings generally understood by those skilled in the art.

[0054] If not otherwise specified, the values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.

[0055] If not otherwise specified, in the present application, the term "active ions" refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0056] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. The "implementation methods" mentioned herein have a similar understanding.

[0057] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can 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 steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can 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 steps (c), (a) and (b), etc.

[0058] In the present application, in the open technical features or technical solutions described by the words "contain", "include", "comprise", etc., unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2 and a3" and the feature or solution of "A not only includes a1, a2 and a3, but also includes other members". In the present application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0059] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0060] Metal current collectors are prone to corrosion reactions in the electrolyte system, and their corrosion products will cause irreversible losses to the battery. For example, corrosion products consume positive electrode active materials, increase resistance, and pollute the electrolyte to increase the battery self-discharge rate, which will eventually lead to irreversible loss of battery capacity. In severe cases, it may cause battery safety problems. Therefore, the corrosion resistance of the current collector has a significant impact on battery performance and safety.

[0061] In some examples of the present application, a current collector is provided, including a current collector body and a passivation protective layer formed in situ on the surface of the current collector, and the passivation protective layer is an oxide or a fluoride. Combining the SEM cross-sectional morphology and elemental analysis scanning, it can be seen that the oxygen element or the fluorine element, which is the characteristic element characterizing the passivation protective layer, is concentrated on the surface of the current collector to form a dense passivation protective layer. The dense protective layer can effectively inhibit the corrosion of the electrolyte to the current collector during the battery cycle, thereby improving the cycle performance of the battery. At the same time, the passivation protective layer can also effectively improve the safety performance of the battery without affecting the conductivity of the pole piece.

[0062] In some examples of the present application, the passivation protective layer is fluoride. Since fluoride is stable and will no longer react with the acid in the battery electrolyte, it can further effectively inhibit the corrosion of the electrolyte to the current collector during the battery cycle, thereby improving the cycle and safety performance of the battery.

[0063] In some examples, the material of the current collector is aluminum or aluminum alloy. Different materials of current collectors are matched according to different battery systems.

[0064] In some examples, the passivation protective layer is aluminum oxide or aluminum fluoride.

[0065] In some examples, the thickness of the current collector is 5 μm to 50 μm. The appropriate thickness of the current collector is selected according to the electrochemical performance of the battery. Specifically, the thickness of the current collector includes but is not limited to: 5 μm, 7 μm, 10 μm, 13 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm or a range between any two of the foregoing. Further optionally, the thickness of the current collector is 5 μm to 20 μm.

[0066] In some examples, the thickness of the passivation protective layer is 0.2μm to 50μm. Reasonable control of the thickness of the passivation protective layer is conducive to the comprehensive improvement of corrosion resistance and mechanical properties of the substrate. Specifically, the thickness of the current collector includes but is not limited to: 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 4μm, 10μm, 20μm, 30μm, 40μm, 50μm or a range between any two of the foregoing. Optionally, the thickness of the passivation protective layer is 0.2μm to 10μm; further optionally, the thickness of the passivation protective layer is 0.5μm to 3μm.

[0067] In some examples, the ratio of the thickness of the current collector to the thickness of the passivation protective layer is 2.5 to 300:1; optionally, the thickness ratio is 3 to 70:1. According to different battery systems matching current collectors of different thicknesses, the ratio of the thickness of the current collector to the thickness of the passivation protective layer includes but is not limited to: 2.5:1, 6.5:1, 13:1, 26:1, 30:1, 50:1, 65:1, 100:1, 200:1, 300:1; further optionally, the thickness of the passivation protective layer is 0.5μm to 3μm.

[0068] In some examples, the passivation protective layer is formed by anodizing the surface of the current collector.

[0069] In some examples, the passivation protective layer is prepared by direct oxidation on the surface of the current collector to obtain a dense oxide. Taking oxygen as the characteristic element, combined with SEM electron microscope scanning, it can be observed that the characteristic element is distributed on the surface of the current collector and has obvious stratification with the inner current collector material. This result can reflect the compactness of the passivation protective layer. Normal aluminum foil or aluminum alloy foil will have aluminum oxide, but the aluminum oxide is loose and cannot play a passivation protection role.

[0070] As a specific embodiment, the electrolyte used for anodizing to generate oxides includes: acidic, alkaline, or neutral electrolytes, and there is no restriction on the pH of the electrolyte. It mainly utilizes water electrolysis to generate active oxygen atoms [O] that react with the surface of the aluminum-based current collector material to generate a dense oxide layer as a passivation protective film.

[0071] In some examples, the passivation protective layer is prepared by introducing a fluorine-containing electrolyte additive during anodization and oxidizing it on the surface of the current collector to obtain a dense fluoride. Taking fluorine as a characteristic element, combined with SEM electron microscope scanning, it can be observed that the characteristic element is distributed on the surface of the current collector and has a clear stratification with the inner layer current collector material. This result can reflect the density of the passivation protective layer.

[0072] As a specific embodiment, the electrolyte used for anodizing to generate fluoride includes: an acidic component and a fluorine-containing electrolyte additive, water is electrolyzed to generate active oxygen atoms [O], and fluoride ions in the fluorine-containing electrolyte additive react with the surface of the aluminum-based current collector material to form fluoride as a passivation protective layer.

[0073] As a specific embodiment, the electrolyte used for anodizing to generate fluoride includes: an acidic component and a fluorine-containing electrolyte additive, water electrolysis generates active oxygen atoms [O], and the acidic component (H+) introduced by the electrolyte and the fluorine ions in the fluorine-containing electrolyte additive react with the surface of the aluminum-based current collector material to form fluoride as a passivation protective layer; further, the selection of the fluorine-containing electrolyte additive includes: at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride, and the mass content of the fluorine-containing electrolyte additive is: 0-100g / L; optionally, the mass content is 1-50g / L; further, the acidic component includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30-300g / L, optionally 100-200g / L.

[0074] In some of these examples, the current density of the anodizing process is 0.3 to 10 A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

[0075] It can be understood that the essence of anodizing is to react with the surface of the aluminum-based current collector to form a passivation protective layer such as an aluminum oxide layer or aluminum fluoride, which is not easy to react with the electrolyte. Taking the aluminum current collector as the anode as an example, the electrode reaction occurring during the power-on process is:

[0076] H2O-2E→2H + +[O]

[0077] 2Al+3[3O]→Al2O3+1670.5J

[0078] After the above-mentioned electrode reaction occurs at the current collector anode, the aluminum on the surface of the current collector will be oxidized to form an aluminum oxide layer. The dense aluminum oxide can serve as a passivation protective layer to effectively inhibit the corrosion of the electrolyte to the current collector during the battery cycle, thereby improving the cycle and safety performance of the lithium-ion battery.

[0079] Furthermore, the fluorine-containing electrolyte additive added to the anodizing electrolyte will generate hydrofluoric acid (HF) in the acidic or neutral anodizing electrolyte. After the hydrofluoric acid contacts the current collector, it will further react with the aluminum oxide on the surface of the current collector to generate an aluminum fluoride passivation protective layer. Since the generated aluminum fluoride will no longer react with the lithium-ion battery electrolyte, it can effectively inhibit the corrosion of the electrolyte to the current collector during the battery cycle, thereby improving the cycle and safety performance of the lithium-ion battery.

[0080] Specifically, the electrolyte used in the anodizing treatment includes: an acidic component and a fluorine-containing electrolyte additive, the acidic component and the fluorine element react with the current collector to form fluoride on the surface; the selection of the fluorine-containing electrolyte additive includes: at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride, and the mass content of the fluorine-containing electrolyte additive is: 0-100g / L; optionally, the mass content is 1-50g / L.

[0081] Some other examples of the present application provide a method for preparing a current collector, comprising the following steps:

[0082] A passivation protective layer of fluoride or oxide is formed on the surface of the current collector by anodization.

[0083] The method electrolyzes the anodic oxidation electrolyte by applying an external current to generate a passivation protective layer on the current collector surface that can stably exist at a higher voltage and temperature. The preparation method has simple steps and is easy to promote and apply industrially.

[0084] It can be understood that the current collector prepared by the above preparation method has the same or similar scheme and effect as the aforementioned current collector, and will not be described in detail here.

[0085] In some examples, the anodizing treatment specifically includes placing a current collector as an anode in an electrolyte for anodizing; the current collector may be aluminum foil or aluminum alloy foil; the current density of the anodizing treatment is 0.3 to 10 A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

[0086] As a specific embodiment, the electrolyte used for anodizing to generate oxides includes: acidic, alkaline, or neutral electrolytes, and there is no restriction on the pH of the electrolyte. It mainly utilizes water electrolysis to generate active oxygen atoms [O] that react with the surface of the aluminum-based current collector material to generate a dense oxide layer as a passivation protective film.

[0087] As a specific embodiment, the electrolyte used for anodizing to generate fluoride includes: a fluorine-containing electrolyte additive, an acidic component and a fluorine-containing electrolyte additive, water electrolysis to generate active oxygen atoms [O], and fluoride ions in the fluorine-containing electrolyte additive react with the surface of the aluminum-based current collector material to form fluoride as a passivation protective layer.

[0088] As a specific embodiment, the electrolyte used for anodizing to generate fluoride includes: an acidic component and a fluorine-containing electrolyte additive, water electrolysis generates active oxygen atoms [O], and the acidic component (H+) introduced by the electrolyte and the fluorine ions in the fluorine-containing electrolyte additive react with the surface of the aluminum-based current collector material to form fluoride as a passivation protective layer; further, the selection of the fluorine-containing electrolyte additive includes: at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride, and the mass content of the fluorine-containing electrolyte additive is: 0-100g / L; optionally, the mass content is 1-50g / L; further, the acidic component includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30-300g / L, optionally 100-200g / L.

[0089] In some examples, the anodizing treatment further includes a sealing treatment step, wherein the sealing treatment is one of heat sealing, medium temperature sealing, cold sealing or organic sealing. The sealing treatment can further reduce the porosity and adsorption capacity of the passivation protective film, thereby improving the corrosion resistance of the film layer.

[0090] Some other examples of the present application provide a pole piece, which includes the current collector as described above or the current collector prepared by the preparation method as described above.

[0091] Some other examples of the present application provide a secondary battery, including the positive electrode sheet or the negative electrode sheet as described above.

[0092] Some other examples of the present application provide an electrical device, including one or more of the electrode sheet described above and the secondary battery described above.

[0093] The present application has no particular restrictions on the type of secondary battery. For example, the secondary battery can be a lithium-ion battery. In general, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charge and discharge process of the secondary battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The present application has no particular restrictions on the type of the electrolyte, which can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte). Secondary batteries using electrolytes, as well as some secondary batteries using solid electrolytes, may also include a separator, which is disposed between the positive electrode sheet and the negative electrode sheet. The secondary battery and electrical device of the present application will be described below with appropriate reference to the accompanying drawings, taking lithium-ion batteries as an example.

[0094] [Positive electrode]

[0095] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0096] It is understandable that, taking lithium batteries as an example, the battery will be accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. The positive electrode active material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode active material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that the new material obtained by appropriate modification on the basis of the listed positive electrode active materials is also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode active material, and non-limiting examples include coating modification.

[0097] In the list of positive electrode active materials in this application, the content of oxygen (O) is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be measured by molar content, but is not limited to this.

[0098] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0099] In some of the embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a metal current collector foil including the first aspect of the embodiment of the present application or a metal current collector foil prepared by the method described in the second aspect of the embodiment of the present application may be used. 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 obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0100] In some of the embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, 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, one or more of lithium cobalt oxide (such as LiCoO2), 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. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.15 Al 0.05 O2.

[0101] In some of these embodiments, the positive electrode active material layer may also optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0102] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some of the embodiments, the positive electrode sheet can be prepared in the following manner: 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; the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 to 25000mPa·s. When the positive electrode slurry is coated, the coating unit surface density on a dry weight basis (excluding the solvent) can be 15 to 35mg / cm 2 The compaction density of the positive electrode sheet can be 3.0 to 3.6 g / cm 3 , can be selected as 3.3~3.5g / cm 3 .

[0104] [Negative electrode]

[0105] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0106] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0107] In some of the embodiments, the negative electrode current collector may be a metal foil or a composite current collector. 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 substrate. The composite current collector can be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material generally include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In some of the embodiments, the negative electrode current collector can be selected as an aluminum-based current collector. For example, compared with lithium-ion batteries, sodium-ion batteries do not react with aluminum to form an alloy, so the negative electrode can also select an aluminum-based current collector. These embodiments can use a metal current collector foil including the first aspect of the embodiment of the present application or a metal current collector foil prepared by the method described in the second aspect of the embodiment of the present application.

[0108] In some of the embodiments, the negative electrode active material layer may also include other negative electrode active materials for batteries known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0109] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more 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).

[0110] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some of the embodiments, the negative electrode active material layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0112] As a non-limiting example, the negative electrode film layer can be formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0113] In some of the embodiments, the negative electrode sheet can be prepared in the following manner: 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 (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode collector coated with the negative electrode slurry can be on a single surface of the negative electrode collector or on both surfaces of the negative electrode collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 to 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75 to 220g / m 2 The compaction density of the negative electrode sheet can be 1.0g / cm 3 ~1.8g / cm 3 .

[0114] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode collector and the negative electrode film layer and disposed on the surface of the negative electrode collector; in some embodiments, the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0115] [Electrolytes]

[0116] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0117] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0118] In some of the embodiments, the electrolyte salt may include 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 difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0119] The electrolyte contains lithium bis(fluorosulfonyl)imide (LiFSI) under high voltage conditions, especially at high potentials greater than 4.2V. As the number of charge and discharge cycles increases, the LiFSI-containing electrolyte will cause serious corrosion to the aluminum-based current collector, thereby affecting the safety performance of the secondary battery. Therefore, for electrolytes such as LiFSI that are suitable for high voltage systems, the safety performance deterioration exposed by the current collector corrosion problem is more serious.

[0120] The type of the solvent is not specifically limited and can be selected according to actual needs.

[0121] In some embodiments, the solvent may include 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), ethylene carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0122] In some embodiments, the electrolyte may further include additives, such as 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, additives that improve battery high or low temperature performance, etc.

[0123] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0124] [Isolation film]

[0125] 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 stability and mechanical stability can be selected.

[0126] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0127] In some embodiments, the isolation film has a thickness of 6 to 40 μm, and may be 12 to 20 μm.

[0128] In some of the embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly by a winding process or a lamination process.

[0129] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0130] 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, and further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0131] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0132] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0133] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0134] In some of these embodiments, reference Figure 2, the outer packaging may include a shell 51 and a cover plate 53. Among them, 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 form 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 battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0135] The secondary battery may be a battery module 4 or a battery pack 1 .

[0136] The battery module includes at least one battery cell. The number of battery cells contained in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0137] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0138] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0139] In some of the embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select a suitable number according to the application and capacity of the battery pack.

[0140] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0141] In addition, the present application also provides an electrical device, which includes a secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but are not limited thereto.

[0142] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0143] Figure 6 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module can be used.

[0144] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0145] Example

[0146] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If the techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0147] Example 1

[0148] 1) Preparation of current collector

[0149] Prepare anodizing electrolyte: the concentration of ammonium fluoride additive in the electrolyte is 3g / L, the concentration of sulfuric acid is 150g / L, and a 13-micron thick aluminum current collector is used as the anode. The temperature is 10°C, the voltage is 12V, and the current density is 1A·dm -2 Anodizing treatment was carried out under the conditions of , and a 0.2 μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector. Then the current collector was placed in 100°C hot water for sealing treatment for 20 minutes.

[0150] 2) Preparation of batteries

[0151] The positive electrode active material lithium iron phosphate, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone (NMP) solution at a mass ratio of 96%: 2.5%: 2.5% to prepare a positive electrode slurry with a solid content of 63%. Then, an extrusion coater was used to evenly coat the slurry on the surface of the 13 μm thick current collector. The coating weight was 220 g / m 2 After drying the foil at room temperature, transfer it to a 105°C oven and dry it for 20 minutes. Then, use a cold press to cold-press the coated electrode to 160 μm and punch it out to make the positive electrode.

[0152] The negative electrode active material graphite, the conductive agent carbon black, the thickener sodium hydroxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) were fully stirred and mixed in deionized water at a mass ratio of 96%:1%:1%:2% to make a negative electrode slurry with a solid content of 53%; the negative electrode slurry was coated on the surface of a 13μm thick copper foil with a coating weight of 110g / m 2 , dried, and then the coated electrode is cold pressed to 152μm by a cold press and punched into a positive electrode.

[0153] A 9-micron thick polyethylene film (PE separator) was used as the separator.

[0154] Ethylene carbonate, ethyl methyl carbonate and diethyl carbonate are mixed in a volume ratio of 5:3:2 to obtain an organic solvent, and fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0155] The positive electrode sheet, isolation film and negative electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to play an isolating role, and then wound into a square bare battery cell, loaded with aluminum-plastic film, and then baked at 80°C to remove water, and then 10g of the corresponding non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, a finished battery with a capacity of 2mAh is obtained.

[0156] Embodiment 2:

[0157] The method for preparing a secondary battery in Example 2 is similar to that in Example 1, with the main difference being that sodium fluoride is selected as an electrolyte additive during the preparation of the current collector.

[0158] Embodiment 3:

[0159] The preparation method of the secondary battery in Example 3 is similar to that in Example 1, with the main difference being that lithium fluoride is selected as the electrolyte additive during the preparation of the current collector.

[0160] Embodiment 4:

[0161] The method for preparing a secondary battery in Example 4 is similar to that in Example 1, with the main difference being that magnesium fluoride is selected as an electrolyte additive during the preparation of the current collector.

[0162] Embodiment 5:

[0163] The preparation method of the secondary battery in Example 5 is similar to that in Example 1, except that the concentration of ammonium fluoride additive in the electrolyte is 6 g / L and the concentration of sulfuric acid is 180 g / L. The temperature is 15°C, the voltage is 18 V, and the current density is 1 A·dm -2 The anodization treatment was carried out under the conditions of , and a 1μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector. The SEM cross-sectional morphology and elemental analysis are shown in Figure 8 ,From the element analysis, it can be seen that there is a dense aluminum fluoride passivation protective layer on the surface of the current collector.

[0164] Embodiment 6:

[0165] The preparation method of the secondary battery in Example 6 is similar to that in Example 5, with the main difference being that sodium fluoride is selected as the electrolyte additive during the preparation of the current collector.

[0166] Embodiment 7:

[0167] The preparation method of the secondary battery in Example 7 is similar to that in Example 5, the main difference being that lithium fluoride is selected as the electrolyte additive during the preparation of the current collector.

[0168] Embodiment 8:

[0169] The preparation method of the secondary battery in Example 8 is similar to that in Example 5, with the main difference being that magnesium fluoride is selected as the electrolyte additive during the preparation of the current collector.

[0170] Embodiment 9:

[0171] The preparation method of the secondary battery in Example 9 is similar to that in Example 1, except that the concentration of ammonium fluoride additive in the electrolyte is 8 g / L, the concentration of sulfuric acid is 220 g / L, the temperature is 25°C, the voltage is 25 V, and the current density is 2 A·dm -2 Anodization treatment was carried out under conditions of , and a 4μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0172] Embodiment 10:

[0173] The method for preparing a secondary battery in Example 10 is similar to that in Example 9, with the main difference being that sodium fluoride is selected as an electrolyte additive during the preparation of the current collector.

[0174] Embodiment 11:

[0175] The method for preparing a secondary battery in Example 11 is similar to that in Example 9, with the main difference being that lithium fluoride is selected as an electrolyte additive during the preparation of the current collector.

[0176] Embodiment 12:

[0177] The preparation method of the secondary battery in Example 12 is similar to that in Example 9, with the main difference being that magnesium fluoride is selected as the electrolyte additive during the preparation of the current collector.

[0178] Embodiment 13:

[0179] 1) Preparation of current collector

[0180] Prepare anodizing electrolyte: 100 g / L sulfuric acid, with 13 μm thick aluminum current collector as anode, at 14 °C, voltage 10 V, current density 1 A·dm -2 The anodization treatment was carried out under the conditions of , and a 0.5μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector. Then, the current collector was placed in 100℃ hot water for 20 minutes to seal the oxide layer. The SEM cross-sectional morphology and element analysis are shown in Fig. 9 From the elemental analysis, it can be seen that the oxygen element is concentrated on the surface of the current collector to form a dense passivation protective layer.

[0181] 2) Preparation of batteries

[0182] The same as Example 1, no further details will be given here.

[0183] Embodiment 14:

[0184] The preparation method of the secondary battery in Example 14 is similar to that in Example 13, except that the anodic oxidation electrolyte in the preparation of the current collector is 150 g / L sulfuric acid, the temperature is 20°C, the voltage is 15 V, and the current density is 1 A·dm -2 Anodization treatment was carried out under conditions of , and a 1 μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0185] Embodiment 15:

[0186] The preparation method of the secondary battery in Example 15 is similar to that in Example 13, except that the anodic oxidation electrolyte in the preparation of the current collector is 180 g / L sulfuric acid, the temperature is 25°C, the voltage is 18 V, and the current density is 1.5 A·dm -2 Anodization treatment was carried out under conditions of , and a 2μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0187] Embodiment 16:

[0188] The preparation method of the secondary battery in Example 16 is similar to that in Example 13, except that the anodic oxidation electrolyte is 200 g / L sulfuric acid, the temperature is 30°C, the voltage is 20 V, and the current density is 2 A·dm -2 Anodization treatment was carried out under conditions of , and a 4μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0189] Embodiment 17:

[0190] The preparation method of the secondary battery in Example 17 is similar to that in Example 13, except that the anode oxidation electrolyte is 35 g / L oxalic acid, the temperature is 22°C, the voltage is 35 V, and the current density is 1.5 A·dm -2 Anodization treatment was carried out under conditions of , and a 2μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0191] Embodiment 18:

[0192] The preparation method of the secondary battery in Example 18 is similar to that in Example 5, except that no acid is added, 150 g / L sodium citrate is used, the pH is adjusted to neutral, the temperature is 25°C, the voltage is 25 V, and the current density is 1 A·dm -2 Anodization treatment was carried out under conditions of , and a 1 μm thick aluminum fluoride passivation protective layer was formed on both sides of the current collector.

[0193] The preparation method of the secondary battery of Comparative Example 1 is similar to that of the secondary battery of Example 1, the main difference being that the current collector directly uses a 13 μm thick aluminum foil that has not been anodized. The SEM cross-sectional morphology and elemental analysis thereof are shown in FIG. Figure 7 From the element analysis, it can be seen that the oxygen element is distributed relatively loosely and is not concentrated in the outer layer to form a dense passivation protective layer.

[0194] Performance Testing

[0195] (1) Resistance value test

[0196] The surface resistance of the current collector was tested using a resistance tester, and the test results are shown in Table 1.

[0197] (2) Brittleness test

[0198] The brittleness of the current collector is reflected by the number of times it is repeatedly folded at the same crease position until it breaks. The fewer the number of folds, the more brittle the current collector is. The test results are shown in Table 1.

[0199] (3) Constant voltage test

[0200] The current collector prepared in each embodiment is used as the positive electrode, and the lithium sheet is used as the negative electrode to assemble a button cell. The electrolyte uses LiFSI electrolyte. A constant voltage test is performed at different voltages as shown in Table 2. If there is no obvious current increase within 2 hours, it is considered that the current collector has good corrosion resistance at this voltage. In the table, "√" indicates that there is no obvious current increase within 2 hours, and "×" indicates that there is an obvious current increase within 2 hours.

[0201] (4) High temperature cycle performance

[0202] The secondary battery was placed in a 45°C constant temperature box and the cycle life was tested according to the following process; the test results are shown in Table 1:

[0203] 1) 2A constant current charging to 3.65V, 3.65V constant voltage charging to a cut-off current of 250mA;

[0204] 2) Rest for 5 minutes;

[0205] 3) 2A constant current discharge to 2.5V,

[0206] 4) Rest for 5 minutes;

[0207] 5) Repeat steps 1-4) for 500 cycles or until the capacity decays to 80% of the initial value.

[0208] (5) Electrode resistance test

[0209] Cut the electrode into appropriate size, test it using electrode resistance meter BER1100, and record the electrode resistance value.

[0210] Table 1

[0211]

[0212]

[0213] Table 2

[0214] serial number 4.2V 4.3V 4.35V 4.4V 4.5V Comparative Example 1 × × × × × Example 1 √ √ × × × Example 2 √ √ × × × Example 3 √ √ × × × Example 4 √ √ × × × Example 5 √ √ √ √ × Example 6 √ √ √ √ × Example 7 √ √ √ √ × Example 8 √ √ √ √ × Example 9 √ √ √ √ √ Example 10 √ √ √ √ √ Embodiment 11 √ √ √ √ √ Example 12 √ √ √ √ √ Embodiment 13 √ × × × × Embodiment 14 √ √ √ √ × Embodiment 15 √ √ √ √ √ Example 16 √ √ √ × × Embodiment 17 √ √ √ √ √ Embodiment 18 √ √ √ √ ×

[0215] Taking the current collectors of Examples 1-4 treated with anodization as an example, it can be seen from the comparison between Examples 1-4 and Comparative Example 1 in Table 1 above that the surface resistance of the current collector treated with anodization can be increased to a higher value than that of the untreated comparative example. Combined with Table 2, it can be seen that the current collector of Comparative Example 1 without any treatment has poor corrosion resistance at a voltage of 4.2-4.5V and suffers from corrosion damage from the electrolyte. Under the condition of the same thickness of the passivation protective layer, Examples 1-4 can resist corrosion from the electrolyte at a higher voltage than the comparative example, indicating that they have better corrosion resistance. Further combined with the pole sheet resistance data, it can be seen that the current collector resistance of Examples 1-4 increases significantly, but the increase in pole sheet resistance is very small, which basically does not affect the conductivity of the entire pole sheet.

[0216] From the data in Table 2, it can be seen from the comparison between Examples 1-4 and 5-8 that after the thickness of the passivation protective layer is increased from 0.2 microns to 1 micron, it can further resist corrosion from the electrolyte at a higher voltage, and the corrosion resistance is further improved. Taking into account the voltage requirements of the electrolyte in actual use, the thickness of the passivation protective layer should be maintained above 0.2 microns. Combined with the data in Table 1, it can be seen from the comparison between Examples 5-8 and 9-12 that after the thickness of the passivation protective layer is increased from 1 micron to 4 microns, it can further resist corrosion from the electrolyte at a higher voltage, but relatively speaking, the passivation protective layer at this thickness accounts for a relatively large proportion of the substrate thickness. It can be seen from Table 1 that it will cause the substrate to become more brittle, and it is necessary to adopt it according to actual needs to maximize the benefits and select the appropriate thickness.

[0217] The corrosion current test results of Comparative Example 1, Example 9 and Example 13 are as follows: Figure 10-12 As shown, by comparison, the test results intuitively reflect that the 4 micron fluoride generated on the surface of the current collector by anodizing in this embodiment 9 does not show a significant increase in current within 2 hours under the condition of 4.2V-4.5V. Combined with the data in Table 2, it can be seen that the 2 micron fluoride is made under the condition of 4.2V-4.4V without a significant increase in current, which can ensure the application of high-voltage environment. The fluoride passivation protective layer of this thickness will only have obvious corrosion at 4.5V, resulting in an increase in current; the 0.5 micron oxide generated on the surface of the current collector by anodizing in this embodiment 13 will have a significant increase in current under the condition of 4.3V-4.5V. Combined with the data in Table 2, it can be seen that the 1 micron fluoride is made under the condition of 4.2V-4.4V without a significant increase in current, which can ensure the application of high-voltage environment. The fluoride passivation protective layer of this thickness will only have obvious corrosion at 4.5V, resulting in an increase in current. Therefore, the passivation protective layer selects a suitable thickness according to its type and the working voltage of the battery.

[0218] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0219] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A current collector, characterized in that: A passivation protective layer is in-situ formed on the surface of the current collector, and the passivation protective layer is an oxide or a fluoride.

2. The current collector according to claim 1, characterized in that: The material of the current collector includes at least one of aluminum or aluminum alloy; Optionally, the current collector has a thickness of 5 μm to 50 μm.

3. The current collector according to claim 2, characterized in that: The passivation protection layer is aluminum oxide or aluminum fluoride.

4. The current collector according to any one of claims 1 to 3, characterized in that: The thickness of the passivation protective layer is 0.2 μm to 50 μm; optionally, the thickness of the passivation protective layer is 0.2 μm to 10 μm; further optionally, the thickness of the passivation protective layer is 1 μm to 4 μm.

5. The current collector according to any one of claims 1 to 4, characterized in that: The ratio of the thickness of the current collector to the single-sided thickness of the passivation protection layer is 2.5:1 to 300:1; optionally, the thickness ratio is 5:1 to 70:

1.

6. The current collector according to any one of claims 1 to 4, characterized in that: The characteristic element oxygen or fluorine is distributed on the surface of the current collector to form layers.

7. The current collector according to any one of claims 3 to 6, characterized in that: The passivation protection layer is formed by anodizing the surface of the current collector.

8. The current collector according to claim 7, characterized in that: The electrolyte used in the anodizing treatment includes an acidic electrolyte, an alkaline electrolyte or a neutral electrolyte, so that the surface of the current collector reacts and forms an oxide on the surface; The acidic electrolyte includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30 to 300 g / L, optionally 100 to 200 g / L; The alkaline electrolyte includes at least one soluble alkali; optionally, includes at least one of sodium hydroxide, ammonium hydroxide, sodium oxalate, sodium phosphate or sodium silicate; the concentration of all soluble alkalis is 5 to 200 g / L, optionally 20 to 100 g / L.

9. The current collector according to claim 7, characterized in that: The electrolyte used in the anodizing treatment includes: an acidic component and a fluorine-containing electrolyte additive, so that the surface of the current collector reacts and forms fluoride on the surface; the selection of the fluorine-containing electrolyte additive includes: at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride, and the concentration of the fluorine-containing electrolyte additive in the electrolyte is: 0-100g / L; optionally, the concentration of the fluorine-containing electrolyte additive is 1-50g / L.

10. The current collector according to claim 9, characterized in that: The acidic component includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30-300g / L, optionally 100-200g / L.

11. The current collector according to any one of claims 7 to 10, characterized in that: The current density of anodizing treatment is 0.3~10A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

12. A method for preparing a current collector, characterized in that: The method comprises the following steps: performing an anodic oxidation treatment on the surface of the current collector to form a passivation protection layer of fluoride or oxide.

13. The method for preparing a current collector according to claim 12, characterized in that: The anodizing treatment specifically includes placing the current collector as an anode in an electrolyte for anodizing; the current collector can be aluminum foil or aluminum alloy foil; the current density of the anodizing treatment is 0.3 to 10 A / dm 2 The processing voltage is 5-110V, the processing temperature is 5-30℃, and the processing time is 5-300min.

14. The method for preparing a current collector according to claim 12 or 13, characterized in that: The electrolyte used in the anodizing treatment includes an acid electrolyte, an alkaline electrolyte, or a neutral electrolyte; Optionally, the acidic electrolyte includes at least one soluble acid; optionally, includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids is 30 to 300 g / L, optionally 100 to 200 g / L; Optionally, the alkaline electrolyte includes at least one soluble alkali; optionally, includes at least one of sodium hydroxide, ammonium hydroxide, sodium oxalate, sodium phosphate or sodium silicate; the concentration of all soluble alkalis is 50-200 g / L, optionally 20-100 g / L.

15. The method for preparing a current collector according to claim 12 or 13, characterized in that: The electrolyte comprises: an acidic component and a fluorine-containing electrolyte additive, wherein the acidic component and the fluorine element react with the current collector to form fluoride on the surface; the selection of the fluorine-containing electrolyte additive comprises: at least one of ammonium fluoride, sodium fluoride, aluminum fluoride, lithium fluoride, calcium fluoride, potassium fluoride or magnesium fluoride, and the mass content of the fluorine-containing electrolyte additive is: 0-100g / L; optionally, the mass content is 1-50g / L.

16. The method for preparing a current collector according to claim 13 or 15, characterized in that: The electrolyte also includes at least one soluble acid; optionally, it includes at least one of sulfuric acid, chromic acid, phosphoric acid, oxalic acid or nitric acid; the concentration of all soluble acids in the electrolyte is 30 to 300 g / L, optionally 100 to 200 g / L.

17. The method for preparing a current collector according to any one of claims 12 to 16, characterized in that: The anodizing treatment further includes a sealing treatment step, wherein the sealing treatment is one of heat sealing, medium temperature sealing, cold sealing or organic sealing.

18. A pole piece, characterized in that: The pole piece includes the current collector according to any one of claims 1 to 11 or the current collector prepared by the method for preparing the current collector according to any one of claims 12 to 17.

19. A secondary battery, characterized in that: Including the pole piece as claimed in claim 18.

20. An electrical device, characterized in that: Includes one or more of the electrode sheet according to claim 18 and the secondary battery according to claim 19.

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