CN115172650A - Composite pole piece, preparation method thereof and secondary battery - Google Patents

Composite pole piece, preparation method thereof and secondary battery Download PDF

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Publication number
CN115172650A
CN115172650A CN202210786636.8A CN202210786636A CN115172650A CN 115172650 A CN115172650 A CN 115172650A CN 202210786636 A CN202210786636 A CN 202210786636A CN 115172650 A CN115172650 A CN 115172650A
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Prior art keywords
layer
metal
polymer layer
metal film
pole piece
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冯玉川
韩波
李峥
陈凯
何泓材
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Suzhou Qingtao New Energy S&T Co Ltd
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Suzhou Qingtao New Energy S&T Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)

Abstract

The invention discloses a composite pole piece, a preparation method thereof and a secondary battery. The composite current collector comprises a polymer layer, wherein metal switching layers are arranged on the surfaces of two sides of the polymer layer and are used for welding lugs; the metal transfer layer is partially overlapped with the polymer layer on the inner side of the edge of the polymer layer and extends out of the outer side of the edge of the polymer layer; the composite current collector further comprises a metal film layer, the metal film layer covers the polymer layer and the metal switching layer in the overlapped area, and an electrode material coating is further arranged on one side of the metal film layer, which is far away from the overlapped area of the metal switching layer and the polymer layer. The invention effectively solves the technical problems of reduced diversion area, increased internal resistance of the battery, poor overcurrent capacity and welding quality and unstable welding line connection state caused by welding in the prior art.

Description

Composite pole piece, preparation method thereof and secondary battery
Technical Field
The invention relates to the field of secondary batteries, in particular to a composite pole piece, a preparation method thereof and a secondary battery.
Background
With the large-scale commercial use of lithium ion batteries, frequent safety accidents attract great attention, and the problem of thermal runaway ignition and explosion caused by short circuit and the like is a difficult problem which is urgently needed to be solved by vast battery manufacturers. At present, researchers try to use a composite foil current collector to replace a traditional metal foil as a current collector of a positive electrode and a negative electrode, the composite foil is usually formed by adding a polymer layer in metal film layers on two sides, the current collector adopting the metal-high polymer-metal structure can effectively improve the performance of preventing the battery from being punctured, extruded and impacted by heavy objects, and meanwhile, the polymer material is lighter, so that the weight of the current collector can be reduced, and the energy density of the battery can be improved.
However, in order to enable the battery to have excellent electrochemical performance, the metal film layers on both sides of the composite foil are often relatively thin, and due to the existence of the intermediate polymer layer, the tab cannot be directly welded with the battery pole piece, so that the metal switching sheet needs to be spliced for welding, the polymer layer avoids under the pressure of the welding head, a welding seam with a cavity in the middle is easily formed, the current conduction area is reduced, the overcurrent capacity is poor, the internal resistance of the pole piece is increased, the welding pressure is not easy to control, the welding pressure is small, the front and back welding states are unstable, the front and back welding states are easy to fall off in the subsequent transportation and use process, the battery is not used well, the welding pressure is large, the welding head is easy to damage, and the production cost is increased.
Disclosure of Invention
In view of the above problems in the prior art, the present invention provides a composite electrode sheet, a method for manufacturing the same, and a secondary battery. The technical problems that the internal resistance of a battery is increased and the overcurrent capacity is poor due to the fact that a polymer layer avoids to form a cavity and the current conduction area is reduced when the tab welding is carried out in the prior art can be effectively solved, the quality of a welding seam can be enhanced, and the improvement of the connection strength of the welding seam is facilitated.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite electrode sheet, including a composite current collector, an electrode material layer and a tab formed on the composite current collector;
the composite current collector comprises a polymer layer, a metal transfer layer and a metal film layer, wherein the metal transfer layer is stacked with the polymer layer in a partially overlapped mode;
the pole lug is connected with the metal adapter layer.
In some embodiments of the present application, the metal film layer is formed on the polymer layer, the first region where the polymer layer overlaps the metal via layer.
Preferably, the thickness of the metal transfer layer is 12-16 μm.
In one embodiment, the metal film layer may extend to the metal via layer.
Preferably, the thickness of the polymer layer is 2-10 μm, preferably 3-5 μm.
Preferably, the width of the overlapping area of the polymer layer and the metal transfer layer is 3mm-6mm.
As a preferred technical scheme of the composite pole piece, the thickness of the metal film layer is 100nm-5 mu m.
Preferably, the metal film layer is a metal film layer coated with a carbon coating on the surface.
Preferably, the distance between the electrode material coating and the metal transfer layer is 5mm-40mm.
In the invention, the electrode material coating is positioned on at least one side of the composite current collector;
preferably, when only one side of the metal transition layer is connected with the tab, the electrode material coating and the tab are positioned on one side surface of the composite current collector.
Preferably, the electrode material coating and the tab are positioned on one side surface of the composite current collector.
In order to facilitate the welding of the electrode lug, the two side surfaces of the polymer layer are respectively provided with a metal switching layer which is a first metal switching layer and a second metal switching layer.
The thicknesses of the first metal transfer layer and the second metal transfer layer can be the same or different;
preferably, the metal film layer includes a first metal film layer and a second metal film layer.
In a second aspect, the present invention provides a method for preparing a composite electrode sheet according to the first aspect, the method comprising the following steps:
s1: splicing metal switching layers on the surfaces of the two sides of the polymer layer;
s2: forming a metal film layer on the surfaces of the polymer layer and the metal transfer layer;
s3: welding the splicing area;
s4: forming a coating of electrode material on a side remote from the splice region;
it is understood that any method that can form a metal film layer on the surface of the polymer layer and the metal transfer layer can be used in the present invention.
Illustratively, in step S2, the metal film layer is formed by evaporation, deposition or sputtering.
Alternatively, step S5 is performed after step S4: and after drying, carrying out tab welding on the metal switching layer.
The method for forming the electrode material coating layer in the present invention is not limited, and for example, an electrode slurry coating method may be employed.
In a third aspect, the present invention provides a secondary battery, wherein the secondary battery comprises the composite pole piece of the first aspect.
The preparation method of the secondary battery is not limited in the invention, and for example, the composite pole piece can be wound or laminated to form a battery core.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, through improving the structure of the composite pole piece, especially changing the position of the metal film layer in the composite pole piece, the conducting area of the current is increased, and the problems of resistance increase and poor overcurrent capacity caused by welding are effectively avoided. The structure through using the composite pole piece of this application also can effectively improve welding quality, can effectively prevent droing of in-process sheetmetal and utmost point ear such as transport, leads to the use of battery bad.
Drawings
Fig. 1 and 2 are schematic structural diagrams of a composite pole piece in an embodiment of the invention, wherein fig. 1 is a front view and fig. 2 is a top view.
Wherein, 110-polymer layer, 121-first metal transition layer, 1222-second metal transition layer, 130-metal film layer, 140-welding structure, 200-electrode material coating, 300-tab.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
In an embodiment of the present invention, a composite electrode sheet, as shown in fig. 1 and 2, for a secondary battery, includes a composite current collector 100, an electrode material layer 200 formed on the composite current collector, and a tab 300.
The composite current collector comprises a polymer layer 110, a metal transition layer 120 spliced together with the polymer layer in a partially overlapped mode, and a metal film layer 130 formed on the polymer layer and the metal transition layer;
the metal interposer partially overlaps the polymer layer 110 inside the edges of the polymer layer and extends outside the edges of the polymer layer 110.
In some embodiments of the present application, the metal film layer is formed on the polymer layer, the first region where the polymer layer overlaps the metal via layer.
In one embodiment, the thickness of the metal interposer layer is 12-16 μm, such as 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm, etc.
As a preferred embodiment of the present invention, the electrode material coating and the tab are located on the same side of the composite pole piece.
The composite pole piece provided by the embodiment of the invention is provided with the electrode pole piece in a layered structure, so that the current conduction area is increased, and the internal resistance of the battery is effectively reduced. The problems of increased internal resistance and poor overcurrent capacity of the battery caused by reduction of the diversion area due to avoidance of a welding polymer layer are effectively solved.
In the present invention, the polymer layer 110 mainly has the following functions: on one hand, when the internal temperature of the battery core is sharply increased, the battery core is melted, so that the current is cut off, and the safety problem of the battery is improved; on the other hand, when a needle stick occurs, the sharp portion is prevented from piercing the septum or other portion to cause a short circuit by virtue of its own extensibility. If the polymer base material is too thin, the polymer base material is easily punctured when subjected to needling or impact, the problem of short circuit of the battery caused by needling and the like cannot be effectively solved, and if the polymer base material is too thick, the internal resistance of the battery is increased, and the performance of the battery is deteriorated.
The tab 300 is connected to the metal transition layer 120.
In one embodiment, the polymer layer 110 has a thickness of 2-10 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and the like, preferably 3-5 μm.
In some embodiments, the material of the polymer layer 110 may be one or more of polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, polypropylene, polyamide, polyimide, polyethylene oxide, polyvinyl chloride, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl alcohol, styrene butadiene rubber, fluorinated rubber, and the like.
In one embodiment, the width of the metal transfer layer overlapping the polymer layer 110 is 3mm-6mm, such as 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, or 6mm.
In one embodiment, the metal transition layer is made of one or more of aluminum, copper, stainless steel, nickel, titanium, and the like.
In order to realize the welding of the tab and the composite pole piece, as shown in fig. 1 and 2, the polymer layer 110 is provided with metal transition layers 120 on both side surfaces, which are a first metal transition layer 121 and a second metal transition layer 122, respectively. The materials of the first metal via layer 121 and the second metal via layer 122 may be the same or different.
In one embodiment, the first metal via layer 121 and the second metal via layer 122 have the same thickness.
In one embodiment, the thickness of the metal film layer 130 is 100nm-15 μm, such as 100nm, 500nm, 1 μm, 3 μm, or 5 μm. Although the thickening of the metal film layer is beneficial to increasing the conduction area of current and improving the overcurrent capacity and reducing the resistance, the thickening of the metal layer is not beneficial to improving the energy density of the battery.
In one embodiment, the metal film 130 is made of one or more of aluminum, copper, stainless steel, nickel, titanium, and the like.
In one embodiment, the material of the metal film 130 is the same as or different from that of the metal via layer.
In one embodiment, the metal film layer 130 is a metal film layer coated with a carbon coating on the surface.
In one embodiment, the metal film layer 130 may be divided into a first metal film layer and a second metal film layer on both sides of the polymer layer.
In one embodiment, the electrode material coating 200 is located at a distance of 5mm to 40mm, such as 5mm, 8mm, 10mm, 12.5mm, 15mm, 20mm, 25mm, 28mm, 30mm, 35mm, 37mm, or 40mm, etc., from the metal relay layer. The distance here is the distance between the electrode material coating and the metal transition layer on the same side, and specifically is the minimum distance from the edge of the electrode coating to the edge of the metal transition layer.
The specific type of the electrode material coating 200 is not limited in the present invention, and may be divided into a positive electrode active material layer and a negative electrode active material layer according to actual needs.
In one embodiment, the positive electrode active material layer includes a positive electrode active material. The positive electrode active material is a compound capable of reversibly intercalating and deintercalating lithium, and specifically, may include a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of nickel, cobalt, manganese, and aluminum; preferably, lithium and transition metals such as nickel, cobalt or manganese may be included.
In some embodiments, the positive electrode material may also be elemental sulfur and sulfur-containing compounds.
In one embodiment, the amount of the cathode active material contained in the cathode active material layer may be 80wt% to 99wt%, for example, 80wt%, 82.5wt%, 85wt%, 87wt%, 90wt%, 92wt%, 94wt%, 95wt%, 97wt%, or 99wt%, etc., preferably 92wt% to 98.5wt%.
In one embodiment, the positive electrode active material layer may include a positive electrode binder and/or a positive electrode conductive material in addition to the positive electrode active material.
The positive electrode binder is used to bind components such as a positive electrode active material, a positive electrode conductive material, and a current collector together, and specifically, may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber, and preferably polyvinylidene fluoride.
In one embodiment, the amount of the cathode binder included in the cathode active material layer may be 1wt% to 20wt%, for example, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%, 12.5wt%, 15wt%, 16wt%, 18wt%, or 20wt%, etc., preferably 1.2wt% to 10wt%.
The positive electrode conductive material is mainly used to assist and improve conductivity in the secondary battery, and is not particularly limited as long as it has conductivity without causing chemical changes. Specifically, the positive electrode conductive material may include graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders such as fluorocarbon powders, aluminum powders, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and a polyphenylene derivative, and preferably contains carbon black from the viewpoint of improving conductivity.
In one embodiment, the specific surface area of the positive electrode conductive material may be 80m 2 G to 200m 2 In g, e.g. 80m 2 /g、90m 2 /g、100m 2 /g、110m 2 /g、125m 2 /g、150m 2 /g、160m 2 /g、170m 2 /g、180m 2 /g、190m 2 (ii)/g or 200m 2 G, etc., preferably 100m 2 G to 150m 2 /g。
In one embodiment, the amount of the cathode conductive material included in the cathode active material layer may be 1wt% to 20wt%, for example, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%, 12.5wt%, 15wt%, 16wt%, 18wt%, or 20wt%, etc., preferably 1.2wt% to 10wt%.
In one embodiment, the thickness of the positive electrode active material layer may be 30 μm to 400 μm, for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 110 μm, 120 μm, 130 μm, 150 μm, 160 μm, 170 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 300 μm, 325 μm, 350 μm, 370 μm, 400 μm, or the like, preferably 50 μm to 110 μm.
In one embodiment, the positive electrode active material layer is obtained by coating a positive electrode slurry containing a positive electrode active material and optionally a positive electrode binder, a positive electrode conductive material, and a solvent, followed by drying and roll-pressing.
In one embodiment, the solvent used to form the cathode slurry may include an organic solvent, such as N-methyl-2-pyrrolidone (NMP), in an amount such that a preferred viscosity is obtained when the cathode active material is included and the cathode binder, the cathode conductive material, and the like are optionally included. For example, the amount of the positive electrode slurry forming solvent contained in the positive electrode slurry may be such that the concentration of solids containing the positive electrode active material, and optionally the positive electrode binder and the positive electrode conductive material, is 50wt% to 95wt%, for example, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%, and the like, preferably 70wt% to 90wt%.
In one embodiment, the negative active material layer includes a negative active material. The negative electrode active material is not particularly limited as long as it can electrochemically absorb and release a metal ion in the s region such as a lithium ion, a sodium ion, a potassium ion, or a magnesium ion. Specific examples thereof include: carbonaceous materials, metallic compound-based materials, or oxides, carbides, nitrides, silicides, sulfides, phosphides, etc. thereof. These may be used alone or in combination of two or more. The negative active material in the embodiment of the invention is not particularly limited.
In some embodiments, a carbon material may be selected as the negative active material, and specifically one or more of the following may be selected, such as: graphite, needle coke, amorphous carbon, a carbon-containing mesophase, carbon fiber, and a carbon material having a small graphitization degree. The graphite may include natural graphite, artificial graphite, and the like. Further, a material obtained by coating these with a carbon material, for example, amorphous carbon or a graphite material, may be used. Examples of the amorphous carbon include: particles obtained by firing the entire mesophase and particles obtained by firing the carbon precursor without melting. Examples of the carbonaceous particles having a small graphitization degree include particles obtained by firing an organic material at a temperature of usually less than 2500 ℃.
In addition, the non-metallic material which can be used as the anode active material also comprises silicon simple substance and compound thereof, such as Si and SiO x (x is more than or equal to 0 and less than 2), because the silicon-containing material is easy to expand and fall off from the negative current collector and has poor conductivity, the silicon-containing material is often mixed with a carbon material for use, such as a core-shell structure containing a carbon coating layer.
In some embodiments, the metal element and the metal compound may be selected as the negative active material, and specific examples are as follows: and compounds containing metals or metalloids such as Li, ag, al, bi, cu, ga, ge, in, ni, pb, sb, si, sn, sr, zn, etc.
In one embodiment, the amount of the negative active material contained in the negative active material layer may be 80wt% to 99wt%, for example, 80wt%, 82wt%, 83wt%, 85wt%, 88wt%, 90wt%, 92.5wt%, 95wt%, 96wt%, or 98wt%, etc., preferably 95wt% to 97wt%.
In one embodiment, the anode active material layer may include an anode binder in addition to the anode active material.
In one embodiment, the negative electrode active material is a non-metal material such as a carbon material, and one or more of an aqueous binder such as sodium carboxymethylcellulose, styrene-butadiene latex, polyacrylic acid, acrylic copolymer, cyclodextrin and the like is used. When an aqueous solvent is used as the liquid medium for forming the slurry, it is preferable to form the slurry using a thickener. Tackifiers are generally used to adjust the viscosity of the slurry.
In one embodiment, the tackifier may be one or more of the following: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof.
In one embodiment, the amount of the adhesion promoter in the negative electrode active material layer is 0.1wt% to 5wt%, such as 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%, etc., preferably 0.5wt% to 3wt%, more preferably 0.6wt% to 2wt%.
The invention provides a preparation method of the composite pole piece, which comprises the following steps:
s1: splicing metal switching layers on the surfaces of the two sides of the polymer layer;
s2: forming a metal film layer on the surfaces of the polymer layer and the metal transfer layer;
s3: welding the splicing area;
s4: a coating of electrode material is formed on the side remote from the splicing region.
It is understood that any method that can form a metal film layer on the surface of the polymer layer and the metal transfer layer can be used in the present application.
Illustratively, in step S2, the metal film layer is formed by evaporation, deposition or sputtering.
In an embodiment of the present invention, a secondary battery is provided, which includes the composite electrode sheet described above.
The method for manufacturing the secondary battery according to the present invention is not particularly limited, and those skilled in the art may manufacture the secondary battery by referring to the methods disclosed in the prior art.
In one embodiment, the secondary battery includes an electrolyte. The present invention is not particularly limited in the kind of electrolyte, and any known electrolyte material can be used in the present application without departing from the inventive concept of the present application. By way of illustrative example, the electrolyte may be a liquid electrolyte, a solid electrolyte, or a mixture of a solid electrolyte and a liquid electrolyte.
When the electrolyte adopts liquid electrolyte, a diaphragm is also arranged in the battery system.
The separator mainly functions to separate the negative electrode and the positive electrode and to provide a moving path for lithium ions. Any separator may be used without particular limitation so long as it is a separator commonly used in secondary batteries. In particular, a separator having excellent wettability with an electrolytic solution and low resistance to ion movement in an electrolyte is preferable. Specifically, a porous polymer film, for example, a porous polymer film made using a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or having a laminated structure of two or more layers thereof may be used. Also, typical porous nonwoven fabrics, for example, nonwoven fabrics formed of glass fibers having a high melting point, polyethylene terephthalate fibers, and the like, may be used. In addition, a coating separator including a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may be selectively used in a single layer or a multi-layer structure.
In one embodiment, the electrolyte used in the present invention may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a melt-type inorganic electrolyte, etc., which may be used in the manufacture of a secondary battery, but is not limited thereto.
Specifically, the electrolyte may include an organic solvent and a lithium salt. Any organic solvent may be used without particular limitation so long as it can serve as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ -butyrolactone, and ∈ -caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), ethyl Methyl Carbonate (EMC), ethylene Carbonate (EC), and Propylene Carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a linear, branched or cyclic C2-C20 hydrocarbon group and may contain double-bonded aromatic rings or ether linkages); amides such as dimethylformamide; dioxolanes, such as 1, 3-dioxolane; or sulfolane. Among the above solvents, carbonate-based solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ion conductivity and high dielectric constant, which can increase the charge/discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1 to about 1.
Any compound may be used as the lithium salt without particular limitation so long as it can provide lithium ions used in a lithium secondary battery. In particular, liPF 6 、LiClO 4 、LiAsF 6 、LiBF 4 、LiSbF 6 、LiAlO 4 、LiAlCl 4 、LiCF 3 SO 3 、LiC 4 F 9 SO 3 、LiN(C 2 F 5 SO 3 ) 2 、LiN(C 2 F 5 SO 2 ) 2 、LiN(CF 3 SO 2 ) 2 、LiCl、LiI、LiB(C 2 O 4 ) 2 Etc. may be used as the lithium salt. The lithium salt may be used in a concentration range of 0.1-2.0M, such as 0.1M, 0.3M, 0.5M, 0.7M, 0.8M, 1M, 1.2M, 1.3M, 1.5M, 1.6M, 1.8M, or 2.0M, and the like. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity to exhibit excellent properties, and lithium ions can be efficiently moved.
In one embodiment, the electrolyte may be a solid electrolyte, and the solid electrolyte particles may comprise one or more components of a polymer, an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, or a combination thereofA electrolyte, a borate solid electrolyte, a nitride solid electrolyte, or a hydride solid electrolyte. When polymer particles are used, the lithium salt should be used for the recheck. As an embodiment, the polymer-based component may comprise one or more polymeric materials selected from the group comprising: polyethylene glycol, polyethylene oxide (PEO), poly (p-phenylene oxide) (PPO), poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof. It will be appreciated that the high ionic conductivity of the polymeric material is advantageous for the performance of the bulk solid state electrolyte material, preferably the polymeric material should have a value of greater than or equal to 10 -4 Ion conductivity of S/cm.
Example 1
In this embodiment, as shown in fig. 1 and fig. 2, based on the composite pole piece provided in the above-mentioned one embodiment, metal via layers are disposed on both the front and back surfaces of the polymer layer 110, and are specifically divided into a first metal via layer 121 and a second metal via layer 122, and the tab 300 is disposed on the first metal via layer 121;
the overlapping width of the first metal transition layer 121 and the polymer layer 110 is 4mm, the overlapping width of the second metal transition layer 122 and the polymer layer 110 is 4mm, the thickness of the polymer layer 110 is 4 μm, and the thicknesses of the transition layers of the first metal transition layer 121 and the second metal transition layer 122 are equal and are both 12 μm; the thickness of the metal film layer is 800 nm;
the electrode material coating 200 is positioned on one side of the composite pole piece, is positioned on the same side as the pole lug, and is 20mm away from the metal switching layer;
the metal film layer 130, the first metal transfer layer 121 and the second metal transfer layer 122 are all made of aluminum metal, the positive active material is NCM523, and the negative electrode is graphite;
in this embodiment, the metal film layer 130, the first metal transition layer 121, the polymer layer 110, and the second metal transition layer 122 form the welding structure 140 by welding.
The embodiment also provides a preparation method of the composite pole piece structure, which comprises the following steps:
s1: splicing metal switching layers on the surfaces of the two sides of the polymer layer;
s2: forming a metal film layer on the surfaces of the polymer layer and the metal transfer layer, wherein the metal film layer is formed by evaporation;
s3: welding the splicing area;
s4: coating electrode slurry on one side far away from the splicing area, drying to obtain an electrode material coating, and rolling to obtain a composite pole piece;
and welding a tab 2 on the first metal switching layer 121 by using the composite pole piece, and winding or laminating the pole pieces to form the battery cell.
Example 2
This example differs from example 1 in that the thickness of the metal film layer is 1 μm;
example 3
This example differs from example 1 in that the thickness of the metal film layer was 3 μm;
example 4
This example differs from example 1 in that the thickness of the metal film layer is 5 μm;
comparative example 1
The comparative example is different from example 1 in that a composite foil (i.e., a metal film layer formed by vapor deposition directly on a polymer layer) is used, and a metal relay layer is joined to the front and back sides of the same side as in example 1 (the material, joining position, and size of the metal relay layer are the same as in example 1) and welded, and the remaining characteristics are the same as in example 1. .
Comparative example 2
The comparative example is different from example 1 in that a metal current collector having the same thickness as the composite current collector of example 1 is used, and the remaining characteristics are the same as example 1.
And (3) needle punching test:
the cell was fully charged, and at 25 ℃ a 3-8mm steel needle was used to penetrate the cell at 25mm/s for 10min. See table 1 for the results of the fire and explosion.
And (3) resistance testing:
the prepared cell can be used for measuring the internal resistance by a voltage internal resistance instrument, and the result is shown in table 1.
And (3) current conduction test:
fixing the battery core by using an adhesive tape, pulling the tabs by using pull force of 600N/mm, connecting the pulled battery with an ammeter, and testing the current conduction condition, wherein the results are shown in table 1.
Overcurrent capability test
Carrying out a charging test at room temperature by using a high-rate current 5C, and testing the surface temperature of a pole piece empty foil area and a pole lug; if the temperature is higher than 60 ℃, the overcurrent capacity is not good, and the result is shown in table 1.
TABLE 1
Figure 472173DEST_PATH_IMAGE001
From the above, the composite pole piece of the embodiment 1-4 can effectively reduce the internal resistance of the battery, and meanwhile, the overcurrent capacity is greatly improved, compared with the comparative example 1, the embodiment 1-4 can still pass current after being pulled by large tensile force, and probably because the existence of the metal film layer increases the connection strength of the welding line, the tab is not easy to separate.
Although the thickening of the metal film layer is beneficial to increasing the conduction area of current and improving the overcurrent capacity and reducing the resistance, the thickening of the metal layer is not beneficial to improving the energy density of the battery.
Examples 1 to 4 slightly generate heat on the surface of the battery when charging and discharging with a large current, and the battery in reference 1 generates heat seriously, which may be because the current in reference 1 is conducted only by the contact area of the welding seam, the overcurrent capability is poor, and the heat generation is serious when charging and discharging with a large current, and in fact, the battery core needs to operate in a proper temperature range (generally 20 to 45 ℃), and an irreversible chemical side reaction occurs inside the battery core due to an excessively high temperature, thereby reducing the service life.
Therefore, the structure of the composite pole piece is improved, the position of the metal film layer in the composite pole piece is changed, the current conduction area from the electrode material coating to the pole lug is effectively increased, the internal resistance of the battery is reduced, the connection quality of the conductive structure can be effectively improved, and the stable process flow and the stable production are facilitated.
The applicant states that the present invention is illustrated by the above examples to show the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be carried out. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. A composite pole piece comprises a composite current collector, and an electrode material layer and a pole lug which are formed on the composite current collector, and is characterized in that the composite current collector comprises a polymer layer, a metal switching layer and a metal film layer, wherein the metal switching layer is used for welding the pole lug;
the metal transfer layer is partially overlapped with the polymer layer on the inner side of the edge of the polymer layer and extends out of the outer side of the edge of the polymer layer;
the metal film layer is formed on the polymer layer and a first area where the polymer layer is overlapped with the metal switching layer;
and an electrode material coating is further arranged on one side of the metal film layer, which is far away from the overlapping area of the metal switching layer and the polymer layer.
2. The composite pole piece of claim 1, wherein the metal film layer, the metal tie layer, and the polymer layer are joined by welding.
3. Composite pole piece according to claim 2, characterized in that the thickness of the polymer layer is 2-10 μm, preferably 3-5 μm.
4. The composite pole piece of claim 3, wherein the metal transfer layer overlaps the polymer layer by a width of 3mm to 6mm.
5. The composite pole piece according to claim 4, wherein the polymer layer is provided with metal transition layers on the front surface and the back surface, wherein the metal transition layers are a first metal transition layer and a second metal transition layer;
preferably, the thickness of one side of the metal transfer layer is 12-16 μm;
preferably, the lengths of the first metal transition layer and the second metal transition layer may be the same or different.
6. The composite pole piece of claim 5, wherein the electrode material coating and the tab are located on one surface of the composite current collector when only one side of the metal transition layer is attached to the tab.
7. The composite pole piece of claim 6, wherein the metal film layer has a thickness of 100nm to 5 μm;
preferably, the metal film layer is a metal film layer coated with a carbon coating on the surface;
preferably, the metal film layer may be divided into a first metal film layer and a second metal film layer on both sides of the polymer layer.
8. The composite pole piece of claim 7, wherein the electrode coating is located a distance of 5mm to 40mm from the metal interposer.
9. A method of making a composite pole piece according to claim 1, comprising the steps of:
s1: splicing metal switching layers on the surfaces of the two sides of the polymer layer;
s2: forming a metal film layer on the surfaces of the polymer layer and the metal transfer layer;
s3: welding the splicing area;
s4: a coating of electrode material is formed on the side remote from the splicing region.
10. A secondary battery comprising the composite pole piece of claim 1.
CN202210786636.8A 2022-07-06 2022-07-06 Composite pole piece, preparation method thereof and secondary battery Pending CN115172650A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115692723A (en) * 2022-11-08 2023-02-03 厦门海辰储能科技股份有限公司 Composite current collector, battery core, battery and preparation method of composite current collector

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115692723A (en) * 2022-11-08 2023-02-03 厦门海辰储能科技股份有限公司 Composite current collector, battery core, battery and preparation method of composite current collector
CN115692723B (en) * 2022-11-08 2024-01-23 厦门海辰储能科技股份有限公司 Composite current collector, battery cell, battery and preparation method of composite current collector

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