Current collector, electrode plate and battery

Abstract

The utility model relates to a current collector, an electrode plate and a battery, the current collector comprises a flame-retardant filling body, a conductive packaging body and a plurality of grooves arranged in the thickness direction of the current collector, the flame-retardant filling body is arranged in the grooves, the flame-retardant filling body is made of a flame retardant, the packaging body is arranged at the opening end of the groove and used for sealing the groove, and the packaging body is made of a flame retardant. And the current collector has a flame-retardant function due to the flame retardant in the current collector, so that the safety performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a current collector, an electrode plate and a battery. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, no memory effect and low self-discharge rate. They are widely used in electric vehicles, mobile communication equipment, portable electronic products, energy storage systems and other fields.

[0003] The safety of automotive power batteries is an important concern in the field of new energy vehicles such as electric vehicles and hybrid vehicles. The rapid development of the electric vehicle market has put forward higher requirements for the safety and stability of battery systems. How to improve the safety performance of batteries is a technical problem that needs to be solved urgently. Utility Model Content

[0004] Based on this, the present application provides a current collector, an electrode plate and a battery, so that the current collector has a flame retardant function, thereby improving the safety performance of the battery.

[0005] In the first aspect of the present application, a current collector is provided, comprising a flame-retardant filler, a conductive packaging body, and a plurality of grooves arranged in the thickness direction of the current collector, wherein the flame-retardant filler is arranged in each of the grooves, the material of the flame-retardant filler comprises a flame retardant, and the packaging body is arranged at the open end of the groove for closing the groove.

[0006] In some embodiments, the ratio of the thickness of the current collector to the average depth of the groove is (2.2-7.5):1, and can be optionally (3-4.5):1.

[0007] In some embodiments, the average depth of the grooves is 3 μm-9.5 μm.

[0008] In some embodiments, the thickness of the current collector is 10 μm to 25 μm.

[0009] In some embodiments, the material of the current collector includes one or more of copper, aluminum, silver, gold, nickel, and alloys thereof.

[0010] In some embodiments, the ratio of the sum of the areas of the maximum cross sections of the grooves perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is (40-200):1, and can be optionally (50-85):1.

[0011] In some embodiments, in a cross section perpendicular to the thickness direction of the current collector, the shape of the groove includes one or more of a circle, a rectangle, a square, a parallelogram, and a triangle.

[0012] In some embodiments, in the maximum cross section of the groove perpendicular to the thickness direction of the current collector, the shortest distance between the edges of adjacent grooves is 200 μm-1000 μm.

[0013] In some embodiments, the package body has an average thickness of 3 μm-9.5 μm.

[0014] In some embodiments, a surface of the encapsulation body away from the flame-retardant filler is flush with a surface of the current collector on that side.

[0015] In some embodiments, the material of the package body includes an alloy.

[0016] In some embodiments, the alloy has a melting point of 80°C-200°C.

[0017] In some embodiments, the alloy includes one or more of a bismuth-lead-cadmium alloy, a bismuth-lead-tin alloy, a bismuth-lead alloy, a lead-tin alloy, a bismuth-tin alloy, and an indium-bismuth-tin alloy.

[0018] In some embodiments, the flame retardant includes one or more of a phosphorus-based flame retardant, a nitrogen-based flame retardant, a halogen-based flame retardant, a metal compound flame retardant, and an electrolyte curing agent.

[0019] In some embodiments, the flame retardant has a decomposition temperature higher than the melting point of the alloy.

[0020] The second aspect of the present application provides a method for preparing the current collector described in the first aspect of the present application, comprising the following steps:

[0021] forming the flame retardant filler in the groove of the current collector along the thickness direction thereof;

[0022] The surface covering groove of the flame retardant filler is filled with a molten liquid containing an alloy, and the molten liquid is cooled to form the packaging body.

[0023] The third aspect of the present application provides an electrode plate, comprising the current collector described in the first aspect of the present application.

[0024] A fourth aspect of the present application provides a battery, comprising the current collector described in the first aspect of the present application and at least one of the electrode plates described in the third aspect of the present application.

[0025] In some embodiments, the flame retardant accounts for 0.1%-2% by mass in the battery, and can be optionally 0.45%-0.75% by mass.

[0026] The fifth aspect of the present application provides an electrical device, comprising the battery described in the fourth aspect of the present application.

[0027] Compared with the conventional technology, the above-mentioned current collector and its preparation method, electrode sheet and battery have at least the following advantages:

[0028] The flame retardant filler inside the above-mentioned current collector has a certain flame retardancy, and the packaging body is conductive and will not affect the performance of the battery. When the battery has thermal runaway, the packaging body melts and releases the flame retardant filler containing the flame retardant in the groove to intervene in the occurrence and development of thermal runaway, so that the current collector has a flame retardant function, thereby improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the front structural view of a current collector according to one embodiment of the present application.

[0030] Figure 2 for Figure 1 Schematic diagram of the structure of the groove of the current collector in one embodiment.

[0031] Figure 3 for Figure 1 A top view of a current collector according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the main structure of a current collector according to another embodiment of the present application.

[0033] Figure 5 for Figure 4 A schematic structural diagram of a groove of a current collector in another embodiment of the present invention.

[0034] Figure 6 This is a schematic diagram of the main structure of the current collector of Example 1 of the present application.

[0035] Figure 7 This is a schematic diagram of the structure of the groove of the current collector in Example 1 of the present application.

[0036] In the figure: 1-current collector; 11-flame retardant filler; 12-packaging body; 13-groove. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0038] In the description of this application, unless otherwise defined, unspecified professional terms and professional words have the same meaning as those commonly understood by those skilled in the art and are common knowledge of those skilled in the art, and unspecified methods are conventional methods known to those skilled in the art. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In this application, "first aspect", "second aspect", "third aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0040] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0041] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0042] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0043] One embodiment of the present application provides a current collector, including a flame-retardant filler, a conductive packaging body, and a plurality of grooves arranged in the thickness direction of the current collector, the flame-retardant filler is arranged in each groove, the material of the flame-retardant filler includes a flame retardant, and the packaging body is arranged at the open end of the groove for closing the groove.

[0044] In the above embodiment, the flame retardant filler inside the current collector has a certain flame retardancy, and the package is conductive, which will not affect the performance of the battery. When the battery has thermal runaway, the package melts and releases the flame retardant filler containing the flame retardant in the groove to intervene in the occurrence and development of thermal runaway, so that the current collector has flame retardancy, thereby improving the safety performance of the battery. It can be understood that the above current collector can be a positive electrode current collector or a negative electrode current collector, and the groove can be opened on both sides of the current collector thickness direction, or only on one side of the current collector thickness direction.

[0045] In the present application, the flame retardant can be a material that prevents the battery from undergoing a combustion reaction, or it can be a material that can block the battery from burning after the battery burns, thereby achieving the purpose of extinguishing the fire. The flame retardant action mode can be endothermic action, covering action, chain reaction inhibition and non-combustible gas suffocation action. The endothermic action of the flame retardant refers to the fact that the flame retardant can absorb the heat generated in the heat generation stage of thermal runaway and the combustion reaction stage in a short period of time, thereby preventing the further occurrence of the heat generation reaction and the combustion reaction. The covering effect of the flame retardant refers to the fact that the flame retardant can form a barrier layer at the thermal runaway temperature to isolate the battery active material from contact with oxygen, and has the effects of heat insulation, oxygen isolation and preventing the escape of combustible gases, thereby achieving the purpose of flame retardancy. The chain reaction inhibition effect of the flame retardant refers to the fact that the flame retardant can capture free radicals in the reaction process during the heat generation stage of thermal runaway and the combustion stage, thereby interfering with the heat generation and combustion reactions. For example, the flame retardant can react with the active material or solidify the electrolyte, thereby preventing the heat generation reaction from proceeding. The non-combustible gas asphyxiation effect of flame retardants means that flame retardants decompose non-combustible gases when heated, diluting the concentration of combustible gases decomposed from combustibles to below the lower combustion limit. At the same time, it also dilutes the oxygen concentration in the combustion zone, preventing the continuation of combustion and achieving a flame retardant effect.

[0046] In some embodiments, in combination Figure 1-Figure 3 The current collector 1 includes a flame retardant filler 11, a conductive packaging body 12, and a plurality of grooves 13 arranged on both sides of the current collector 1 in the thickness direction. The flame retardant filler 11 is arranged in each groove 13. The material of the flame retardant filler 11 includes a flame retardant. The packaging body 12 is arranged at the open end of the groove 13 to close the groove 13.

[0047] In some embodiments, in combination Figure 4-Figure 5 The current collector 1 includes a flame retardant filler 11, a conductive packaging body 12, and a plurality of grooves 13 arranged on one side of the thickness direction of the current collector 1. The flame retardant filler 11 is arranged in each groove 13. The material of the flame retardant filler 11 includes a flame retardant. The packaging body 12 is arranged at the open end of the groove 13 to close the groove 13.

[0048] In some embodiments, the ratio of the thickness of the current collector to the average depth of the groove is (2.2-7.5):1. Controlling the ratio of the thickness of the current collector to the average depth of the groove within the above range can make the current collector have flame retardant properties, thereby further improving the safety performance of the battery while ensuring the electrochemical performance of the battery. The electrochemical properties of the battery include but are not limited to the cycle performance of the battery or the rate performance of the battery. It is understandable that the ratio of the thickness of the current collector to the average depth of the groove includes but is not limited to: 2.2:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 7.5:1. Further, the ratio of the thickness of the current collector to the average depth of the groove is (3-4.5):1.

[0049] In some embodiments, the average depth of the groove is 3 μm-9.5 μm. It is understood that the average depth of the groove includes but is not limited to: 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm.

[0050] In some embodiments, the material of the current collector includes one or more of copper, aluminum, silver, gold, nickel and alloys thereof. It is understood that their alloys include but are not limited to at least one of copper alloy, aluminum alloy, silver alloy, gold alloy and nickel alloy.

[0051] In some embodiments, the thickness of the current collector is 10 μm-25 μm. It is understood that the thickness of the current collector includes but is not limited to: 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm.

[0052] In some embodiments, the ratio of the sum of the areas of the maximum cross sections of the grooves perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is (40-200):1. Thus, the influence of the grooves on the performance of the current collector can be reduced, thereby further improving the safety performance of the battery while ensuring the electrochemical performance of the battery. The above ratios include but are not limited to: 40:1, 60:1, 80:1, 100:1, 120:1, 140:1, 160:1, 180:1, 200:1.

[0053] In some embodiments, in a cross section perpendicular to the thickness direction of the current collector, the shape of the groove includes one or more of a circle, a rectangle, a square, a parallelogram, and a triangle.

[0054] In some embodiments, in the maximum cross-section of the groove perpendicular to the thickness direction of the current collector, the shortest distance between the edges of adjacent grooves is 200 μm-1000 μm. Thus, the influence of the groove on the performance of the current collector can be reduced, thereby further improving the safety performance of the battery while ensuring the electrochemical performance of the battery. It is understood that the shortest distance between the edges of adjacent grooves includes but is not limited to: 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm.

[0055] In some embodiments, the average thickness of the package is 3 μm-9.5 μm. Controlling the thickness of the package within the above range can allow the flame retardant filler to be encapsulated inside the groove, and further reduce the impact of the groove on the performance of the current collector, thereby further improving the electrochemical performance of the battery. It is understood that the average thickness of the package includes but is not limited to: 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 9.5 μm.

[0056] In some embodiments, the surface of the package away from the flame retardant filler is flush with the surface of the side current collector. It is understood that the surface of the side current collector refers to the surface of the current collector on the same side as the surface of the package away from the flame retardant filler.

[0057] In some embodiments, the material of the encapsulation body includes an alloy, which can encapsulate the flame retardant filler inside the groove of the current collector without affecting the conductivity of the current collector.

[0058] In some embodiments, the melting point of the alloy is 80° C.-200° C. It is understood that the melting point of the alloy includes but is not limited to: 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C.

[0059] In some embodiments, the alloy includes one or more of bismuth-lead-cadmium alloy, bismuth-lead-tin alloy, bismuth-lead alloy, lead-tin alloy, bismuth-tin alloy, and indium-bismuth-tin alloy. For example, when the mass ratio of bismuth-lead-cadmium alloy is 52% Bi, 40Pb, 8% Cd, the melting point of the alloy is 92°C; when the mass ratio of bismuth-lead-tin alloy is 53% Bi, 32% Pb, 15% Sn, the melting point of the alloy is 96°C; when the mass ratio of bismuth-lead alloy is 50% Bi, 50% Pb, the melting point of the alloy is 160°C; when the mass ratio of lead-tin alloy is 38% Pb, 62% Sn, the melting point of the alloy is 183°C; when the mass ratio of bismuth-tin alloy is 20% Bi, 80% Sn, the melting point of the alloy is 200°C.

[0060] In some embodiments, the flame retardant may be an inorganic flame retardant or an organic flame retardant.

[0061] In some embodiments, the flame retardant includes one or more of a phosphorus-based flame retardant, a nitrogen-based flame retardant, a halogen-based flame retardant, a metal compound flame retardant, and an electrolyte curing agent.

[0062] In some embodiments, the phosphorus-based flame retardant includes at least one of the following types: red phosphorus flame retardants, ammonium salt flame retardants, phosphate compounds, phosphaphenanthrene compounds, polyphosphazene compounds, hypophosphorous acid and its salt compounds, triazine or piperazine carbon formers, and specific flame retardants include but are not limited to: red phosphorus, ammonium polyphosphate, melamine phosphate and melamine polyphosphate, melamine cyanurate, bisphenol A bis(diphenyl) phosphate, resorcinol (diphenyl) phosphate, tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB), diethyl aluminum hypophosphite, 2-carboxyethyl phenyl hypophosphite, and aluminum hypophosphite.

[0063] In some embodiments, the nitrogen-based flame retardant includes one or more of nitrogen-containing polyamide, nitrogen-containing polyurethane, phosphamide, melamine, and ammonium polyphosphate.

[0064] In some embodiments, the halogen-based flame retardant includes one or more of a chlorine-based flame retardant and a bromine-based flame retardant.

[0065] Optionally, chlorinated flame retardants include chlorinated polyolefins, chlorinated polyalkanes, chlorinated diphenyl ethers, chlorinated benzenes and the like, specifically including but not limited to the following flame retardants: chlorinated polyethylene (CPE), chlorinated polypropylene (CPP), chlorinated paraffin, decachlorodiphenyl ether, hexachlorobenzene and new high-performance chlorinated flame retardants, such as: tetrachlorophthalic anhydride, tetrachlorobisphenol A, hexachlorocyclopentene, bis(hexachlorocyclopentadiene) cyclooctane, perchlorocyclopentadecane, tetrachlorophthalic anhydride and chlorendic acid, etc.

[0066] Optionally, brominated flame retardants can be divided into polybrominated diphenyl ethers, brominated phenols, brominated bisphenol A, brominated phthalates, brominated polyols, brominated alkanes, etc. according to their structures, including but not limited to the following flame retardants, such as: decabromodiphenyl ethane, decabromodiphenyl ether, tetrabromobisphenol A, brominated polystyrene, tribromophenol and its derivatives, brominated triazines, brominated epoxy resins, hexabromocyclododecane, tetrabromobisphenol A polycarbonate oligomers, dibromoneopentyl glycol, tetrabromophthalic anhydride, tetrabromophthalic anhydride diol, melamine bromide, potassium perfluorobutyl sulfonate, decaprol flame retardants, etc.

[0067] In some embodiments, the metal compound flame retardant includes one or more of magnesium-based flame retardants (magnesium hydroxide), antimony-based flame retardants (antimony oxide, sodium antimonate), aluminum hydroxide, zinc borate, molybdenum oxide, and ammonium molybdate.

[0068] In some embodiments, the electrolyte curing agent refers to an electrolyte that can react with the electrolyte to control the dielectric constant or viscosity of the electrolyte, and is intended to suppress Joule heat by destroying the ionic conductivity to force the internal resistance to increase. The curing agent can increase the viscosity of the electrolyte and can convert the liquid electrolyte into a gel or solid substance that is not easily conductive. Optionally, the electrolyte curing agent includes one or more of diols and amine compounds. For example, amine curing agents include but are not limited to: 1,3-propylenediamine, benzylamine, dibenzylamine (DBA), 1,2-ethylenediamine (1,2-EDA) and trihexylamine (THA); diol curing agents include but are not limited to: 1,2-ethylene glycol, 1,3-propylene glycol, 1,5-pentanediol.

[0069] In some embodiments, the flame retardant may include at least one of ammonium bicarbonate, ammonium chloride, and ammonium sulfate.

[0070] In some embodiments, the flame retardant has a decomposition temperature above the melting point of the alloy.

[0071] In some embodiments, the material of the flame retardant filler further comprises one or more of chitosan, polyamide, polyester, polyvinyl alcohol, polyacrylonitrile, polyether, polyaniline, polythiophene and polyacetylene. At least one of the above materials can be coated on the surface of the flame retardant, thereby forming a flame retardant material with a core-shell structure, wherein the core material comprises the flame retardant, and the material of the shell comprises one or more of chitosan, polyamide, polyester, polyvinyl alcohol, polyacrylonitrile, polyether, polyaniline, polythiophene and polyacetylene.

[0072] Another embodiment of the present application provides a method for preparing the above-mentioned current collector of the present application, comprising the following steps:

[0073] forming a flame retardant filler in the groove of the current collector along the thickness direction thereof;

[0074] The surface of the flame retardant filler is covered with a molten liquid containing an alloy, and the molten liquid is cooled to form a packaging body.

[0075] Thus, the current collector can be simply prepared, which is beneficial to the large-scale production of the current collector.

[0076] Another embodiment of the present application provides an electrode plate, including the above-mentioned current collector of the present application. It is understandable that the above-mentioned electrode plate can be a positive electrode plate or a negative electrode plate. Optionally, the electrode plate can be prepared in the following manner: the positive electrode active material or the negative electrode active material, the conductive agent, and the binder are uniformly dispersed in a solvent (such as N-methylpyrrolidone) to form an electrode slurry; the electrode slurry is coated on the above-mentioned current collector of the present application, and after drying, rolling and other processes, a positive electrode plate or a negative electrode plate is formed. The above-mentioned conductive agent and binder can adopt the conductive agent and binder commonly used in the technical field, and there is no special limitation in the present application.

[0077] Another embodiment of the present application also provides a battery, including the current collector mentioned above and at least one of the electrode plates mentioned above. Exemplarily, the battery can be made into an electrode assembly by a winding process or a lamination process with a positive electrode plate, a negative electrode plate and a separator, and then placed in a battery housing, injected with an electrolyte, and made into a battery through packaging, formation and other processes. At least one of the positive electrode plate and the negative electrode plate can adopt the electrode plate mentioned above in the present application. Optionally, the battery includes but is not limited to: a primary battery or a secondary battery. Primary batteries include but are not limited to lithium primary batteries, and secondary batteries include but are not limited to lithium secondary batteries.

[0078] In some embodiments, the mass proportion of the flame retardant in the battery is 0.1%-2%, and optionally 0.45%-0.75%.

[0079] Another embodiment of the present application further provides an electric device, including the battery described above. The battery described above can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device includes, but is not limited to, a mobile phone, a laptop computer, an electric tool, a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0080] In order to further illustrate the present application, the technical scheme of the present application is described in detail below in conjunction with specific examples. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in the field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0081] Example 1

[0082] The preparation method of the current collector of this embodiment is as follows:

[0083] (1) Setting grooves on the copper foil

[0084] Copper foil is used as the current collector substrate, and a plurality of strip-shaped grooves are opened along the length direction of the copper foil. The cross-section of the groove perpendicular to the length direction of the copper foil is semicircular. The length of the copper foil is 58 cm, the width is 46 cm, the thickness is 25 μm, the groove range (the distance between the outermost edges of the grooves at both ends of the width direction of the copper foil) is 40 cm, the average depth of the grooves is 3.5 μm, and the ratio of the thickness of the copper foil to the average depth of the grooves is 7.14:1; in the maximum cross-section perpendicular to the thickness direction of the copper foil, the average length of the groove is 50 cm, the average width of the groove is 7 μm, the shortest distance between the edges of adjacent grooves is 150 μm, and the ratio of the sum of the areas of the maximum cross-sections of the grooves perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross-section is 155:1.

[0085] (2) Preparation of flame retardant

[0086] Ammonium polyphosphate (manufacturer: Aladdin, model: A189185) was used as a flame retardant.

[0087] (3) Filling with flame retardants and alloys

[0088] The inside of the groove is filled with flame retardant ammonium polyphosphate, and the filling depth of the flame retardant is 3.5μm. Then a certain mass of bismuth-lead-cadmium alloy is laid on the surface of the flame retardant, and the copper foil is placed in a tubular furnace and calcined at 100°C in an argon atmosphere for 3 hours, followed by natural cooling and polishing to obtain a current collector, wherein the average thickness of the package formed by the indium-bismuth-tin alloy is 0.6μm-1μm.

[0089] Figure 6 The schematic diagram of the main structure of the current collector of Example 1 is shown. Figure 7 The schematic diagram of the structure of the groove of the current collector of Example 1 shows that the strip groove 13 provided in the current collector 1 in Example 1 is as shown in FIG. Figure 6 and Figure 7 shown.

[0090] (4) Preparation of batteries

[0091] (4.1) Preparation of negative electrode sheet

[0092] Graphite, thickener sodium carboxymethyl cellulose, binder styrene butadiene rubber, and conductive agent acetylene black are mixed in a mass ratio of 97:1:1:1, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum mixer; the negative electrode slurry is evenly coated on the double-side surfaces of the prepared current collector, and a negative electrode sheet is formed after drying.

[0093] (4.2) Preparation of positive electrode sheet

[0094] The positive electrode material LiNi 0.8 Co 0.1 Mn0.1 O2, conductive carbon black SP and binder PVDF are dispersed in a solvent N-methylpyrrolidone (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 the double-side surfaces of the positive electrode current collector aluminum foil, and dried to form a positive electrode sheet.

[0095] (4.3) Assembling the battery

[0096] The prepared 11 positive electrode sheets, 12 negative electrode sheets, a separator and an electrolyte were assembled into a 1Ah soft-pack battery. The separator was located between the positive electrode sheets and the negative electrode sheets. A polyethylene separator with a thickness of 25 μm was used as the separator. The electrolyte model was KLD-LP11, which consisted of 1.2 mol / L LiPF6 and EC (ethylene carbonate):EMC (ethyl methyl carbonate) in a volume ratio of 1:1:1.

[0097] Example 2

[0098] The preparation method of the current collector is basically the same as that of Example 1, except that: in step (1), the average depth of the groove is 6 μm, the average width of the groove is 12 μm, and the ratio of the thickness of the copper foil to the average depth of the groove is 4.17:1; in step (3), the filling depth of the flame retardant is 6 μm, and the ratio of the sum of the areas of the maximum cross sections of the groove perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is 85:1.

[0099] Example 3

[0100] The preparation method of the current collector is basically the same as that of Example 1, except that: in step (1), the average depth of the groove is 8 μm, the average width of the groove is 16 μm, and the ratio of the thickness of the copper foil to the average depth of the groove is 3.125:1; in step (3), the filling depth of the flame retardant is 8 μm, and the ratio of the sum of the areas of the maximum cross sections of the groove perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is 70:1.

[0101] Example 4

[0102] The preparation method of the current collector is basically the same as that of Example 1, except that: in step (1), the average depth of the groove is 9.5 μm, the average width of the groove is 19 μm, and the ratio of the thickness of the copper foil to the average depth of the groove is 2.63:1; in step (3), the filling depth of the flame retardant is 9.5 μm, and the ratio of the sum of the areas of the maximum cross sections of the groove perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is 50:1.

[0103] Example 5

[0104] The preparation method of the current collector is basically the same as that of Example 4, except that: in step (1), the number of grooves is changed so that the ratio of the sum of the areas of the maximum cross sections of the grooves perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is 40:1.

[0105] Comparative Example 1

[0106] A copper foil with a thickness of 25 μm was directly used as the current collector.

[0107] The preparation methods of the batteries of Examples 2-5 and Comparative Example 1 are substantially the same as the preparation method of the battery of Example 1, except that in step (4.1) the current collector of Example 1 is replaced by the current collector of the corresponding example or comparative example.

[0108] Product parameters and performance testing

[0109] (1) Test of average depth, average length and average width of grooves

[0110] The cross section of the current collector is photographed using a scanning electron microscope or a transmission electron microscope. The two ends and the middle of the cross section of the current collector are selected respectively. The depth of 30-50 grooves is randomly measured in each area, and the average value is taken to obtain the average depth of the grooves.

[0111] The test methods for the average length and average width of the grooves are similar to the test method for the average depth of the grooves.

[0112] (2) Test on the ratio of the current collector area to the total area of ​​the groove

[0113] The cross section of the current collector is photographed using a scanning electron microscope or a transmission electron microscope, the sum of the areas of the maximum cross sections of the grooves perpendicular to the thickness direction of the current collector is measured, and the area of ​​the current collector on the cross section is measured to obtain the ratio of the two.

[0114] (3) Cyclic performance test

[0115] The prepared battery was placed in a constant temperature environment of 25°C for cycle performance testing. The process was as follows: discharge it to 2.75V at a constant current of 0.5C, let it stand for 10 minutes, charge it to 4.2V at a constant current of 0.5C, let it stand for 10 minutes, and then discharge it to 2.75V at a constant current of 0.5C. The discharge specific capacity at this time was the initial discharge specific capacity, recorded as D1. Subsequently, according to the above process, a cycle test was performed in the range of 2.75V to 4.2V for 400 cycles. The discharge specific capacity of the 400th cycle was recorded as D2. The capacity retention rate (%) of the battery after 400 cycles = D2 / D1*100%. Repeat the test for 400 cycles.

[0116] (4) Maximum thermal runaway temperature test

[0117] The thermal abuse test method includes: thermal abuse test is carried out in an explosion-proof box. First, the soft-pack battery is placed in a fixture with adjustable nuts on four corners, and the soft-pack battery is separated from the fixture with two mica sheets, and a ceramic heating sheet is placed between the mica sheet and the soft-pack battery on one side, and a K-type thermocouple is fixed between the center of the side of the soft-pack battery away from the ceramic heating sheet and the other mica sheet with high-temperature tape. Adjust the fixture nut to tighten it. During the thermal abuse process, the ceramic heating sheet quickly heats up from room temperature to 200°C and then remains unchanged at 200°C. A K-type thermocouple is used to record the temperature changes during the thermal abuse of the battery. The highest temperature recorded by the K-type thermocouple is the highest thermal runaway temperature.

[0118] The results of the capacity retention rate of the batteries of each embodiment and comparative example 1 and the maximum thermal runaway temperature of the batteries are shown in Table 1.

[0119] Table 1

[0120]

[0121] From Table 1, we can see the following:

[0122] By observing Comparative Example 1 and Examples 1-5, it can be seen that the maximum thermal runaway temperature of the battery of Examples 1-5 is lower than that of Comparative Example 1, and the battery of Examples 1-5 does not catch fire during the thermal runaway process, indicating that the current collector of Examples 1-5 can effectively improve the safety performance of the battery. From the capacity retention rate data of the batteries of Comparative Example 1 and Examples 1-5, it can be seen that the current collector prepared in Examples 1-5 can take into account the cycle performance of the battery.

[0123] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0124] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims, and the description may be used to interpret the content of the claims.

Claims

1. A current collector, characterized in that: It includes a flame retardant filler, a conductive packaging body, and a plurality of grooves arranged in the thickness direction of the current collector, wherein the flame retardant filler is arranged in each of the grooves, the material of the flame retardant filler includes a flame retardant, and the packaging body is arranged at the open end of the groove for closing the groove.

2. The current collector according to claim 1, characterized in that: The ratio of the thickness of the current collector to the average depth of the groove is (2.2-7.5):1; and / or, The average depth of the grooves is 3 μm-9.5 μm.

3. The current collector according to claim 1 or 2, characterized in that: The thickness of the current collector is 10 μm-25 μm.

4. The current collector according to claim 1 or 2, characterized in that: The ratio of the sum of the areas of the maximum cross sections of the grooves perpendicular to the thickness direction of the current collector to the area of ​​the current collector on the cross section is (40-200):1; and / or, In a cross section perpendicular to the thickness direction of the current collector, the shape of the groove includes one or more of a circle, a rectangle, a square, a parallelogram and a triangle; and / or, In a maximum cross section of the groove perpendicular to a thickness direction of the current collector, a shortest distance between edges of adjacent grooves is 200 μm to 1000 μm.

5. The current collector according to claim 1 or 2, characterized in that: The average thickness of the package body is 3 μm-9.5 μm; and / or, The material of the package body includes alloy.

6. The current collector according to claim 5, characterized in that: The melting point of the alloy is 80°C-200°C.

7. The current collector according to claim 6, characterized in that: The decomposition temperature of the flame retardant is higher than the melting point of the alloy.

8. An electrode plate, characterized in that: A current collector comprising any one of claims 1 to 7.

9. A battery, characterized in that: It comprises at least one of the current collector according to any one of claims 1 to 7 and the electrode plate according to claim 8.

10. The battery according to claim 9, characterized in that The flame retardant accounts for 0.1%-2% by mass in the battery.

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