Positive electrode sheet and battery cell comprising positive electrode sheet, battery, and electric device

Abstract

A positive electrode sheet and a battery cell comprising the positive electrode sheet, a battery, and an electric device. The positive electrode sheet comprises a composite current collector and a positive electrode film layer provided on at least one surface of the composite current collector. The composite current collector comprises a polymer material base layer and a metal composite layer located on at least one surface of the polymer material base layer, and the active material of the positive electrode film layer comprises the Ni element. The metal composite layer comprises a metal matrix layer and a metal oxide layer which are stacked. The resistivity of the metal oxide layer is greater than that of the metal matrix layer. The positive electrode sheet can effectively alleviate DCR deterioration and reduce battery failure.

Description

Positive electrode sheet, battery cell, battery and electrical device containing the same Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode sheet and a battery cell, a battery and an electrical device comprising the positive electrode sheet. Background Art

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

[0003] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion batteries have achieved significant development, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0004] Ternary material is one of the positive active materials of lithium-ion batteries. The "ternary" refers to the transition metal elements nickel, cobalt, and manganese. The chemical formula is Li[Ni x Co y Mn (1-x-y) ]O2, abbreviated as NCM. Currently, ternary materials have become the main factor in lithium-ion batteries reaching an energy density of 300Wh / kg. However, as the nickel content in ternary materials increases, the diaphragm direct current resistance (DCR) will significantly deteriorate, making it more likely to cause battery short circuits and even failure.

[0005] Summary of the Invention

[0006] In order to achieve the above objectives, the first aspect of the present application provides a positive electrode sheet that can effectively improve DCR deterioration and reduce battery failure, as well as a battery cell, a battery and an electrical device containing the positive electrode sheet.

[0007] In a first aspect of the present application, a positive electrode plate is provided, comprising a composite current collector and a positive electrode film layer arranged on at least one surface of the composite current collector, wherein the composite current collector comprises a polymer material base layer and a metal composite layer located on at least one surface of the polymer material base layer, and the active material of the positive electrode film layer contains Ni element; the metal composite layer comprises a stacked metal matrix layer and a metal oxide layer, and the resistivity of the metal oxide layer is greater than the resistivity of the metal matrix layer.

[0008] The above-mentioned positive electrode sheet can better balance the overall membrane resistance of the positive electrode sheet, reduce the short-circuit power of the battery, and thus effectively improve the deterioration of the battery DCR and reduce the failure probability, thereby improving the safety performance of the battery.

[0009] In some embodiments, the molar percentage of Ni in the active material is A, the sheet resistance of the metal composite layer is B, and A and B satisfy one of the following conditions:

[0010] (1) 80% ≤ A < 100%, 30mΩ ≤ B ≤ 45mΩ;

[0011] (2) 33%≤A<80%, 25mΩ≤B≤35mΩ.

[0012] Adopting a certain range of metal composite layer square resistance according to different Ni element contents can further improve the deterioration of battery DCR and reduce the failure probability.

[0013] In some embodiments, the mass percentage of the metal oxide layer to the mass percentage of the metal composite layer is 0.3% to 2.1%.

[0014] In some embodiments, the thickness of the metal oxide layer accounts for 0.2% to 1.4% of the thickness of the metal composite layer.

[0015] In some embodiments, the metal element in the metal matrix layer includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0016] In some embodiments, the metal element in the metal oxide layer includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0017] In some embodiments, the thickness of the metal composite layer is 0.75 μm to 2 μm.

[0018] In some embodiments, the thickness of the positive electrode film layer is 50 μm to 300 μm.

[0019] In a second aspect of the present application, a battery cell is provided, comprising the positive electrode sheet described in the first aspect.

[0020] In some embodiments, the battery cell includes a housing for accommodating an electrode assembly, wherein the electrode assembly includes the positive electrode sheet.

[0021] In some embodiments, the shell is square in shape and includes a shell and at least one end cover, the shell has an opening at only one end, and the end cover covers the opening; or both ends of the shell have openings, and the two end covers respectively cover the two openings.

[0022] In some embodiments, the shell is a soft package structure, and the material of the shell includes aluminum-plastic film.

[0023] In some embodiments, the outer shell is in the shape of a cylinder, and the outer shell includes a shell and at least one end cover, the end cover covers the opening of the shell, and the outer diameter of the cylinder is greater than or equal to 30 mm.

[0024] A third aspect of the present application provides a battery comprising the battery cell described in the second aspect.

[0025] In a fourth aspect of the present application, an electrical device is provided, comprising the positive electrode sheet described in the first aspect, the battery cell described in the second aspect, or the battery described in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0028] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0029] FIG3 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0030] Description of reference numerals:

[0031] 1. Battery; 11. Housing; 12. Electrode assembly; 13. Cover; 2. Electrical device.

[0032] 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

[0033] 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.

[0034] 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.

[0035] The "ranges" disclosed in this application can be defined in the form of lower limits and upper limits. 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 the particular range. Ranges defined in this way can be inclusive or exclusive of the end values, 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 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 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 are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "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 listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0036] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] References to "embodiments" herein mean 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 such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0039] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply 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 inherent logic. 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 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 steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0040] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This 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 includes not only a1, a2, and a3, but also other members."

[0041] In this 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.

[0042] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0043] Ternary materials (Li[Ni x Co y Mn (1-x-y)]O2), when the content of Ni, Co, and Mn elements is different, the advantages of the material are also different, among which Ni shows high capacity and low safety; Co shows high cost and high stability; Mn shows high safety and low cost. The Arrhenius equation shows that the energy of the reacting molecules must exceed the activation energy to participate in the reaction. As the Ni content increases, the energy difference between the valence band and the Li hole decreases, and the activation energy required for hole formation decreases, which can generate more Li holes near the interior of the material, thereby improving the electronic conductivity of the material. However, as the Ni content further increases, the sheet resistance of the ternary material decreases, the current increases when the battery has an internal short circuit, and the corresponding heat generation power increases. At the same time, the increase in Ni content will also make the thermal stability of the ternary material worse, the decomposition temperature becomes lower, and the short-circuit failure time is shorter. Therefore, the safety design of batteries using Ni-containing ternary materials, especially ternary materials with a high Ni content, needs to be further improved.

[0044] Batteries typically have four short-circuit modes: ① The metal layer of the positive current collector overlaps the negative active material; ② The metal layer of the negative current collector overlaps the positive active material; ③ The metal layer of the positive current collector overlaps the metal foil of the negative current collector; and ④ The negative active material overlaps the positive active material. The short-circuit power of the negative current collector overlaps the metal layer of the negative active material. Composite current collectors feature a classic "sandwich" structure, with a polymer middle layer and a metal outer layer. They possess an "internal short fuse mechanism" and are considered to be "free of metal burrs," significantly enhancing the battery's safety margins in situations such as needle puncture, crushing, and dropping. The "internal short fuse mechanism" refers to the fact that when an internal short circuit occurs in a battery cell, heat builds up at the short-circuit point, causing the polymer material in the composite current collector's middle layer to fuse at the short-circuit point, resulting in the metal layer losing support and disconnecting the short circuit. "Free of metal burrs" refers to the fact that the composite current collector is cut without metal burrs, often made from polymer wiredrawing, and the cut ends will not pierce the separator.

[0045] However, as the Ni content of the ternary material increases, the membrane resistance decreases and the short-circuit power also increases, which will cause the composite current collector to worsen the DC internal resistance (DCR) of the battery using the ternary material, and the improvement effect on battery short circuit and failure problems is not obvious.

[0046] One embodiment of the present application provides a positive electrode plate, comprising a composite current collector and a positive electrode film layer arranged on at least one surface of the composite current collector, wherein the composite current collector comprises a polymer material base layer and a metal composite layer located on at least one surface of the polymer material base layer, and the active material of the positive electrode film layer contains Ni element; the metal composite layer comprises a stacked metal matrix layer and a metal oxide layer, and the resistivity of the metal oxide layer is greater than the resistivity of the metal matrix layer.

[0047] The above-mentioned positive electrode plate adopts an active material containing the Ni element in the positive electrode film layer, and at the same time, a metal oxide layer is provided on the basis of the original metal layer (metal matrix layer) of the composite set, and the resistivity of the metal oxide layer is made greater than the resistivity of the metal matrix layer. In this way, the overall resistance of the metal composite layer can be improved, so that it can be adapted to the Ni element content in the active material, thereby balancing the overall membrane resistance of the positive electrode plate, reducing the short-circuit power of the battery, effectively improving the deterioration of the battery DCR and reducing the failure probability, thereby improving the safety performance of the battery.

[0048] It is understood that the resistivity of the metal oxide layer and the resistivity of the metal base layer vary depending on the type of metal element, and the above technical solution is sufficient. In addition, when the metal element in the metal base layer is the same as the metal element in the metal oxide layer, the resistivity of the metal oxide layer is greater than the resistivity of the metal base layer.

[0049] Without limitation, the metal oxide layer in the metal composite layer can have a continuous layered structure or a discretely distributed layered structure, and can be multi-layered or single-layered. In the case of multi-layered layers, the metal oxide layer can be alternately stacked with the metal layer. The preparation method can be to selectively oxidize a prefabricated metal layer to form an unoxidized metal layer and an oxidized metal oxide layer. The prefabricated metal layer can be prepared by evaporation or physical vapor deposition, and the oxidant used for oxidation can be oxygen or ozone.

[0050] Without limitation, the active material is a ternary material, and non-limiting examples of the ternary material 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 0.78 Co 0.11 Mn 0.11 O2、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 ), LiNi0.9 Co 0.05 Mn 0.05 O2、LiNi 0.96 Co 0.02 Mn 0.02 O2, etc.

[0051] In some embodiments, the molar percentage of Ni in the active material is A, the sheet resistance of the metal composite layer is B, and A and B satisfy one of the following conditions:

[0052] (1) 80% ≤ A < 100%, 30mΩ ≤ B ≤ 45mΩ;

[0053] (2) 33%≤A<80%, 25mΩ≤B≤35mΩ.

[0054] Adopting a range of metal composite layer sheet resistances for different Ni content can effectively improve the deterioration of battery DCR and reduce the probability of failure. Understandably, the metal composite layer resistance = metal composite layer sheet resistance × metal composite layer thickness. Since the metal composite layer thickness is generally thin, the metal composite layer sheet resistance can be designed to adjust the resistance of the metal composite layer. Without limitation, the sheet resistance of the metal composite layer can be tested using a sheet resistance tester.

[0055] Specifically, when 80% ≤ A < 100%, B includes, but is not limited to, 25 mΩ, 27 mΩ, 30 mΩ, 33 mΩ, 35 mΩ, or a range therebetween. When 33% ≤ A < 80%, B includes, but is not limited to, 30 mΩ, 33 mΩ, 36 mΩ, 40 mΩ, 43 mΩ, 45 mΩ, or a range therebetween.

[0056] In some embodiments, the percentage of the mass of the metal oxide layer to the mass of the metal composite layer is 0.3% to 2.1%. Specifically, the percentage of the mass of the metal oxide layer to the mass of the metal composite layer includes, but is not limited to, 0.3%, 0.6%, 0.9%, 1.2%, 1.5%, 1.8%, 2.1%, or a range between any two of the foregoing.

[0057] In some embodiments, the thickness of the metal oxide layer accounts for a percentage of the thickness of the metal composite layer of 0.2% to 1.4%. Specifically, the thickness of the metal oxide layer accounts for a percentage of the thickness of the metal composite layer of 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, or a range between any two of the foregoing.

[0058] Without limitation, the metal elements in the metal layer and the metal oxide layer may be the same or different, and may be metal elements conventionally used for positive electrode sheets.

[0059] In some embodiments, the metal element in the metal matrix layer includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0060] In some embodiments, the metal element in the metal oxide layer includes one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0061] In some embodiments, the thickness of the metal composite layer is 0.75 μm to 2 μm. Specifically, the thickness of the metal composite layer includes but is not limited to: 0.75 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or a range between any two of the foregoing.

[0062] In some embodiments, the thickness of the positive electrode film layer is 50 μm to 300 μm. Specifically, the thickness of the positive electrode film layer includes but is not limited to: 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, or a range between any two of the foregoing.

[0063] Another embodiment of the present application provides a battery cell including the above-mentioned positive electrode plate.

[0064] In some embodiments, the battery cell includes a housing for accommodating an electrode assembly, wherein the electrode assembly includes the positive electrode sheet.

[0065] In some embodiments, the shell is square in shape and includes a shell and at least one end cover, the shell has an opening at only one end, and the end cover covers the opening; or both ends of the shell have openings, and the two end covers respectively cover the two openings.

[0066] In some embodiments, the shell is a soft package structure, and the material of the shell includes aluminum-plastic film.

[0067] In some embodiments, the outer shell is in the shape of a cylinder, and the outer shell includes a shell and at least one end cover, the end cover covers the opening of the shell, and the outer diameter of the cylinder is greater than or equal to 30 mm.

[0068] Another embodiment of the present application provides a battery, comprising the above-mentioned battery cell.

[0069] Another embodiment of the present application provides an electrical device, including the above-mentioned positive electrode plate, the above-mentioned battery cell or the above-mentioned battery.

[0070] The battery and the electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0071] Typically, a battery cell 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.

[0072] The positive electrode is as described above.

[0073] As a non-limiting example, the composite current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the composite current collector.

[0074] In some embodiments, 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 can be obtained by forming a metal material on a polymer material substrate. In the composite 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 composite 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.

[0075] In some embodiments, the positive electrode film layer may include other traditional positive electrode active materials while including the ternary material. As non-limiting examples, other traditional positive electrode active materials may include one or more 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 battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. 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 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 manganese iron phosphate, and a composite material of lithium manganese iron 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 aluminum oxides may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0076] In some embodiments, the positive electrode film layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin.

[0077] In some embodiments, the positive electrode film layer may further optionally 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.

[0078] 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 ternary 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 composite current 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 composite current collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the composite current collector. The surface of the composite current collector coated with the positive electrode slurry can be on a single surface of the composite current collector or on both surfaces of the composite current 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 5000mPa·s to 25000mPa·s. When coating the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15mg / cm 2 ~35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0079] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0080] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0081] 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 material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may 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 may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative 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.

[0082] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, 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 oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more 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.

[0083] 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).

[0084] 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.

[0085] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0086] In some 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 current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or on both surfaces of the negative electrode current 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 2000mPa·s to 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 ~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0087] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0088] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0089] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0090] 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), butylene 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0091] In some embodiments, the electrolyte may optionally 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.

[0092] 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.

[0093] In some embodiments, the battery cell further includes a separator. This application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0094] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0095] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0096] 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.

[0097] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0098] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic. Non-limiting examples of the plastic include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0099] A battery includes at least one battery cell. A battery may include one or more battery cells.

[0100] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0101] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 1 having a square structure as an example.

[0102] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 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 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to actual needs.

[0103] The battery may be a battery module or a battery pack.

[0104] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0105] In a battery module, multiple battery cells can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Further, the multiple battery cells can be fixed by fasteners.

[0106] Optionally, the battery module may further include a housing having an accommodation space, wherein the plurality of battery cells are accommodated in the accommodation space.

[0107] In some 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 an appropriate number based on the application and capacity of the battery pack.

[0108] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0109] In addition, the present application also provides an electrical device, which includes the battery provided in the present application. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptop computers, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0110] As an electrical device, a battery can be selected according to its usage requirements.

[0111] Figure 3 shows an example of an electric device 2. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0112] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0113] 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.

[0114] 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.

[0115] Example 1

[0116] 1) Preparation of positive electrode sheet

[0117] 1.1 Preparation of composite current collector (thickness 10 μm):

[0118] By physical vapor deposition (PVD), metal aluminum wire with a purity of ≥99.99% is melted to a saturated vapor state in a high-temperature evaporation boat under vacuum conditions. The saturated vapor is then deposited on both surfaces of an 8μm PET polymer base film to form an aluminum metal layer. The aluminum metal layer is oxidized in an ozone atmosphere at 120°C for 10s to form a metal composite layer (1μm thick) with a metal oxide layer (aluminum oxide) content of 0.3%, thereby obtaining a composite current collector.

[0119] 1.2 Preparation of positive electrode

[0120] The ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), conductive carbon black SP and binder PVDF are dispersed in solvent NMP in a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the composite current collector, and after drying and cold pressing, a positive electrode film layer with a thickness of 100 μm is formed to obtain a positive electrode sheet, wherein the coating amount per unit area on both sides is 0.27 g / 1540.25 mm 2 , compacted density is 3.5g / cm 3 .

[0121] 2) Preparation of negative electrode sheet

[0122] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.17g / 1540.25mm 2 , compacted density is 1.6g / cm 3 .

[0123] 3) Isolation film

[0124] A 12μm thick PP / PE / PP separator is selected.

[0125] 4) Preparation of electrolyte

[0126] The organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), with a volume ratio of 3:7. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte solution. The concentration of the lithium salt is 1 mol / L.

[0127] 5) Battery Preparation

[0128] 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 serve as an isolation. After being wound into a square bare battery cell, an aluminum-plastic film is placed in the cell. After being baked at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, and capacity division, a 180Ah hard-shell lithium-ion battery is obtained.

[0129] The preparation methods of the lithium-ion batteries of Examples 2-12 are similar to those of the lithium-ion battery of Example 1, except that ternary materials with different Ni contents are used or the sheet resistance of the metal composite layer is adjusted by adjusting the content of the metal oxide layer.

[0130] The preparation method of the lithium ion battery of Example 13 is similar to that of the lithium ion battery of Example 1, except that different thicknesses of the metal composite layer are used.

[0131] The preparation method of the lithium-ion battery of Example 14 is similar to that of the lithium-ion battery of Example 1, except that different positive electrode film thicknesses are used.

[0132] The preparation method of the lithium ion battery of Example 15 is similar to that of the lithium ion battery of Example 10, except that different thicknesses of the metal composite layer are used.

[0133] The preparation method of the lithium-ion battery of Example 16 is similar to that of the lithium-ion battery of Example 10, except that different positive electrode film thicknesses are used.

[0134] The preparation method of the lithium ion battery of Comparative Example 1 (D1) is similar to that of the lithium ion battery of Example 1, except that no metal oxide layer is provided, that is, no oxidation treatment step is performed in step 1.1.

[0135] The parameters of Examples 1-16 and Comparative Example 1 are shown in Table 1 below.

[0136] Table 1

[0137] Note: The metal oxide layer content refers to the percentage of the mass of the metal oxide layer to the mass of the metal composite layer.

[0138] Test Case

[0139] (1) DCR test:

[0140] The prepared lithium-ion battery was tested for 10s DC resistance (DCR) at 50% SOC at a rate of 3.6C at 25°C.

[0141] (2) Failure probability test:

[0142] The prepared lithium-ion battery was designed to prevent the diaphragm from breaking. That is, after the battery was broken in the fully charged state (4.25V or 100% SOC), the bare battery was taken out and cut into an area of ​​20*20mm in the center of the large surface. 2 The diaphragm is broken, and the bare battery cell is squeezed with a surface pressure of 5 MPa at room temperature of 25°C. Keep it for 1 hour to observe whether the battery cell fails. Repeat 10 times and record the number of failures.

[0143] The test results of each embodiment and comparative example are shown in Table 2 below:

[0144] Table 2

[0145] Note: "0 / 10" means 0 failures out of 10 failure tests, and so on.

[0146] It can be seen that compared with Comparative Example 1, Examples 1 to 2 (ternary materials are the same as Comparative Example 1) can improve the deterioration of DC internal resistance (DCR) by providing a metal oxide layer, and the failure probability is significantly reduced.

[0147] Furthermore, Examples 3 to 12 demonstrate that for ternary materials with different Ni contents, by rationally controlling the sheet resistance of the metal composite layer, the degradation of the DC internal resistance (DCR) can be effectively improved and the failure probability can be reduced. Examples 13 to 16 demonstrate that, while rationally controlling the sheet resistance of the metal composite layer, designing different metal composite layer thicknesses and positive electrode film thicknesses for ternary materials with different Ni content ranges can effectively improve the degradation of the DC internal resistance (DCR) and reduce the failure probability.

[0148] 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.

[0149] 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 positive electrode plate, characterized in that: The invention comprises a composite current collector and a positive electrode film layer provided on at least one surface of the composite current collector, wherein the composite current collector comprises a polymer material base layer and a metal composite layer provided on at least one surface of the polymer material base layer, and the active material of the positive electrode film layer comprises Ni element; The metal composite layer includes a metal base layer and a metal oxide layer which are stacked together. The resistivity of the metal oxide layer is greater than that of the metal base layer.

2. The positive electrode sheet according to claim 1, characterized in that: The molar percentage of Ni in the active material is A, the sheet resistance of the metal composite layer is B, and A and B satisfy one of the following conditions: (1) 80% ≤ A < 100%, 30mΩ ≤ B ≤ 45mΩ; (2) 33%≤A<80%, 25mΩ≤B≤35mΩ.

3. The positive electrode sheet according to claim 1 or 2, characterized in that: The mass percentage of the metal oxide layer to the mass percentage of the metal composite layer is 0.3% to 2.1%.

4. The positive electrode sheet according to any one of claims 1 to 3, characterized in that: The thickness of the metal oxide layer accounts for 0.2% to 1.4% of the thickness of the metal composite layer.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The metal elements in the metal matrix layer include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The metal elements in the metal oxide layer include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

7. The positive electrode sheet according to any one of claims 1 to 6, characterized in that: The thickness of the metal composite layer is 0.75 μm to 2 μm.

8. The positive electrode sheet according to any one of claims 1 to 7, characterized in that: The thickness of the positive electrode film layer is 50 μm to 300 μm.

9. A battery cell, characterized in that: The positive electrode sheet comprises the positive electrode sheet according to any one of claims 1 to 8.

10. The battery cell according to claim 9, characterized in that The battery cell includes a shell, the shell is used to accommodate an electrode assembly, and the electrode assembly includes the positive electrode sheet.

11. The battery cell according to claim 10, characterized in that The shell is square in shape and includes a shell and at least one end cover. The shell has an opening at only one end, and the end cover covers the opening; or both ends of the shell have openings, and the two end covers cover the two openings respectively.

12. The battery cell according to claim 10 or 11, characterized in that: The shell is a soft package structure, and the material of the shell includes aluminum-plastic film.

13. The battery cell according to claim 10, characterized in that The outer shell is in the shape of a cylinder and comprises a shell and at least one end cover, wherein the end cover covers the opening of the shell, and the outer diameter of the cylinder is greater than or equal to 30 mm.

14. A battery, characterized in that: The battery cell comprises the battery cell according to any one of claims 9 to 13.

15. An electrical device, characterized in that: The invention comprises the pole piece according to any one of claims 1 to 8, the battery cell according to any one of claims 9 to 13, or the battery according to claim 14.