CN113206327B - Steel-plastic film for lithium battery and preparation method and application thereof - Google Patents

Steel-plastic film for lithium battery and preparation method and application thereof Download PDF

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CN113206327B
CN113206327B CN202110290103.6A CN202110290103A CN113206327B CN 113206327 B CN113206327 B CN 113206327B CN 202110290103 A CN202110290103 A CN 202110290103A CN 113206327 B CN113206327 B CN 113206327B
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stainless steel
layer
steel foil
binder
nylon
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CN113206327A (en
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赵金保
金建涛
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Xiamen University
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
    • 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
    • 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

Abstract

The invention discloses a steel-plastic film for a lithium battery and a preparation method thereof.A pretreated stainless steel foil is subjected to anodic oxidation on at least the inner side to form an anodic oxidation layer, then a first binder layer is coated on the outer side to compound a nylon layer, a second binder layer is coated on the inner side to compound an innermost layer, and the obtained semi-finished product is cured and molded; the obtained anodic oxide layer is provided with a plurality of holes, so that the peeling strength and electrolyte resistance strength between the inner side and the outer side are further effectively improved on the basis of keeping the advantages of the aluminum-plastic composite film packaging material; the steel-plastic film prepared from the anodized stainless steel foil has excellent corrosion resistance, can effectively improve the electrolytic hydraulic resistance, and improves the safety performance of the battery.

Description

Steel-plastic film for lithium battery and preparation method and application thereof
Technical Field
The invention relates to the technical field of battery preparation, in particular to a steel-plastic film for a lithium battery and a preparation method and application thereof.
Background
The lithium battery mainly comprises four parts of a positive electrode, a negative electrode, a diaphragm and electrolyte. The energy-saving self-discharge intelligent electronic hand ring has the advantages of high energy density, long cycle life, small self-discharge, no memory effect, environmental friendliness and the like, is widely applied to the consumer electronics fields such as smart phones, intelligent hand rings, digital cameras, notebook computers and the like, and has great consumer demand. Meanwhile, the electric vehicle is gradually popularized in the fields of pure electric vehicles, hybrid electric vehicles and extended-range electric vehicles, and the market share is the largest in increasing trend.
The packaging process of the lithium battery in China mainly adopts three structures, namely a cylindrical structure, a square structure and a soft package battery, the aluminum plastic film is a core material of the soft package battery, and the soft package material is required to resist swelling, dissolution and absorption of an organic solvent due to the existence of electrolyte in the battery, and meanwhile, strict separation of oxygen and moisture is also required to be ensured. Therefore, the aluminum plastic film is not only an outer package of the soft package battery, but also one of important components for forming the soft package lithium battery.
From the development trend of the future, with the increasing of the white and hot competition of 3C digital products, the increase of the energy density of the battery is also a choice of the digital enterprises, which leads to the thinner and thinner requirement of the aluminum plastic film. Meanwhile, for the aluminum foil, when the ductility, the puncture resistance and the rigidity are considered comprehensively, the thickness of the aluminum foil must be more than 30 μm, and the thickness cannot be further reduced, so that the application of the aluminum foil to a thinner lithium battery flexible packaging film is limited. Besides the advantage of thinner steel-plastic film, the hardness of the steel-plastic film is higher. With the gradual promotion of the demand of future digital high-end products, novel composite membranes such as steel-plastic membranes become the next generation of key layout route of membrane manufacturers. However, the peeling force between the steel-plastic film layers and the electrolyte resistance still need to be improved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a steel-plastic film for a lithium battery and a preparation method and application thereof.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a preparation method of a steel-plastic film for a lithium battery comprises the following steps:
a) taking a stainless steel foil with the thickness of 20-60 mu m, and carrying out oil removal and acid pickling treatment on the stainless steel foil;
b) the treated stainless steel foil is put into anodic oxidation electrolyte for direct current anodic oxidation, the direct current voltage is 15-50V, and the current density is 1A-10A/dm2Oxidizing for 15-30 min to form an anodic oxidation layer with the thickness of 1 nm-1 mu m on at least the inner side surface of the stainless steel foil, and drying after oxidation;
c) coating a first adhesive layer on the outer side surface of the stainless steel foil in the protective atmosphere of nitrogen, and compounding a nylon layer on the outer side of the stainless steel foil through the first adhesive layer; coating a second adhesive layer on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, and compounding the innermost layer on the inner side of the stainless steel foil through the second adhesive layer;
d) and d) placing the semi-finished product formed in the step c) at a constant temperature of 60-95 ℃ for 4320-7200 minutes, taking out the semi-finished product, cooling to room temperature, and then performing drawing at a drawing pressure of 0.2-0.5 Mpa to obtain the steel-plastic film for the lithium battery.
Optionally, the electrolyte is an aqueous solution of 0.1-0.5M oxoacid and 0.5-2 g/L sodium fluoride, or an aqueous solution of 0.1-0.5M oxoacid and 0.5-4 g/L ethylene glycol, wherein the oxoacid is at least one of sulfuric acid, nitric acid, perchloric acid and phosphoric acid.
Optionally, the thicknesses of the first adhesive layer and the second adhesive layer are respectively 3-12 μm.
Optionally, in the step a), the stainless steel foil is placed in degreasing liquid with the concentration of 100-200 g/L at the temperature of 60-80 ℃ for degreasing, then is soaked in acidic treatment liquid, and then is dried.
Optionally, the degreasing fluid comprises at least one of sodium hydroxide, sodium carbonate, sodium silicate and trisodium phosphate; the acidic treatment liquid comprises at least one of nitric acid, hydrofluoric acid, phosphoric acid and sulfuric acid.
Optionally, the thickness of the nylon layer is 20-100 μm; the nylon layer adopts polyamide resin, including nylon 6, nylon 66, copolymer of nylon 6 and nylon 66, nylon 6,10 and poly-m-xylene adipamide.
Optionally, the innermost layer is made of cast polypropylene and has a thickness of 40-80 μm.
The steel-plastic film for the lithium battery prepared by the preparation method comprises a nylon layer, a first binder layer, a stainless steel foil layer, a second binder layer and an innermost layer from outside to inside, wherein the inner side surface of the stainless steel foil layer is provided with an anodic oxidation layer, the anodic oxidation layer is of a honeycomb-shaped porous structure, and the size of the holes is from nanometer to micrometer.
The steel-plastic film is applied to lithium battery packaging.
The beneficial effects of the invention are as follows:
1) by carrying out anodic oxidation treatment on the stainless steel foil, an oxide film grows on the surface of the stainless steel foil, and the oxide film is provided with a plurality of holes, so that the peeling strength and the electrolyte resistance strength between the inner side and the outer side are further effectively improved on the basis of keeping the advantages of the aluminum-plastic composite film packaging material.
2) Degreasing and deoiling in the step a, removing grease on the surface of the stainless steel foil and loosening an oxide skin on the surface of the stainless steel foil; the pickling removes oxide skin on the surface of the stainless steel foil, so that the stainless steel foil forms a chromium-rich area and the surface of the stainless steel is activated; b, generating an oxide film on the stainless steel foil treated in the step b, wherein the oxide film is provided with a plurality of honeycomb pores; more adhesive can permeate and immerse in the stainless steel foil, and the stripping force between the innermost layer and the stainless steel foil, especially the electrolyte resistance, is improved.
Drawings
FIG. 1 is a schematic view of an anodization process;
FIG. 2 is a sectional view of a steel-plastic film for lithium batteries according to examples 1 to 6;
FIG. 3 is a surface porous SEM image of a stainless steel foil of example 1.
Detailed Description
The invention is further explained below with reference to the figures and the specific embodiments. The drawings are only schematic and can be easily understood, and the specific proportion can be adjusted according to design requirements.
Example 1
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. referring to fig. 1, the pretreated stainless steel foil is put into the anodic oxidation electrolyte solution for direct current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 20V, and the current density is 0.8A/dm2The temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 20 min. The electrolyte is 0.1M phosphoric acid, 1g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 800nm is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of a stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP (polypropylene) layer (namely the innermost layer) on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
d. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Example 2
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. placing the pretreated stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 30V, and the current density is 1.5A/dm2The temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 20 min. The electrolyte is 0.2M phosphoric acid, 1g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 1 mu M is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
d. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Example 3
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. placing the pretreated stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 40V, the current density is 3A/dm2, the temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 20 min. The electrolyte is 0.5M phosphoric acid, 2g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 150nm is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
d. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Example 4
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. placing the pretreated stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 40V, the current density is 2A/dm2, the temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 20 min. The electrolyte is 0.4M perchloric acid, 3g/L glycol and deionized water, an anodic oxide film with the thickness of about 1000nm is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
f. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Example 5
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. placing the pretreated stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; during direct-current anodic oxidation, the direct-current voltage is 40V, the current density is 3A/dm2, the temperature of an anodic oxidation solution is 25 ℃, and the oxidation time is 10 min. The electrolyte is 0.5M phosphoric acid, 2g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 1000nm is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
d. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Example 6
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. placing the pretreated stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 40V, the current density is 3A/dm2, the temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 30 min. The electrolyte is 0.5M phosphoric acid, 2g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 2 mu M is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
c. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
d. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Comparative example 1
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. directly placing the stainless steel foil into the anodic oxidation electrolyte solution for direct-current anodic oxidation; in the direct current anodic oxidation, the direct current voltage is 40V, the current density is 2A/dm2, the temperature of the anodic oxidation solution is 25 ℃, and the oxidation time is 20 min. The electrolyte is 0.5M phosphoric acid, 2g/L sodium fluoride and deionized water, an anodic oxide film with the thickness of about 800nm is formed on the inner side surface of the stainless steel foil, and the stainless steel foil after anodic oxidation is dried;
b. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
c. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Comparative example 2
A preparation method of a lithium battery steel-plastic film comprises the following steps:
a. taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃, degreasing the stainless steel foil, soaking the stainless steel foil in an acidic treatment solution, and drying the treated stainless steel foil;
b. uniformly coating a binder on the outer side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a first binder layer on the outer side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the first binder layer to be 3-12 mu m, and compounding a nylon layer with the thickness of 25 mu m on the outer side of the stainless steel foil; uniformly coating a binder on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, forming a second binder layer on the inner side of the stainless steel foil by the binder, controlling the use amount of the binder to enable the thickness of the second binder layer to be 3-12 mu m, and compounding a PP layer on the inner side of the stainless steel foil to form a semi-finished lithium battery plastic-steel film;
c. and (3) placing the semi-finished product into a constant-temperature oven at 75 ℃, standing at the constant temperature for 5760 minutes, taking out, cooling to room temperature, and then performing deep drawing at the deep drawing pressure of 0.4Mpa to obtain a final product, namely the steel-plastic film for the lithium battery.
Referring to fig. 2, the steel-plastic film of embodiments 1 to 6 sequentially includes, from outside to inside, a nylon layer 1, a first adhesive layer 2, a stainless steel foil layer 3, a second adhesive layer 4, and an innermost layer 5, wherein an anodic oxidation layer 31 is provided on an inner side surface of the stainless steel foil layer 3. Referring to fig. 3, the formation of the anodic oxidation layer enables the surface of the stainless steel foil to have a plurality of honeycomb-shaped holes, the size of the holes is in the nanometer to micrometer level, the specific surface area of the surface of the stainless steel foil is increased, more adhesive can permeate into the stainless steel foil, the adhesion with the adhesive is stronger, the combination of the stainless steel foil and the inner and outer layer materials is firmer, and the electrolytic hydraulic resistance of the steel-plastic film is effectively improved.
The manufacturing steps of the embodiments 1 to 6 are respectively used for the steel plastic film for lithium battery packaging, specifically, the nylon/stainless steel foil semi-finished product composite film and the cast polypropylene film are subjected to dry compounding and curing molding by adopting a binder; the obtained finished film was subjected to an initial state SUS/PP peel strength test and an electrolyte-corroded SUS/PP peel strength test.
The peel strength of SUS/PP was measured in accordance with the specification of GB/T8808-1988 at a drawing speed of (300. + -.50) mm/min in a T-shape in the drawing direction with respect to the non-peeled portion.
The finished films prepared in examples 1-6 and comparative examples 1-2 were tested separately. One part is directly tested for the peeling strength, and the other part is put into the electrolyte to be corroded for a period of time and then is tested for the peeling strength.
Preparing 1mol/L LiPF6 electrolyte (solute is 1mol/L LiPF6, solvent dimethyl carbonate: ethylene carbonate: diethyl carbonate is 1:1:1), and taking a membrane with a flat and clean surface, no wrinkles, a width of 15mm and a length of 100mm for testing. And completely immersing the finished film into the electrolyte, placing the finished film into a constant-temperature water bath at 85 ℃, and testing for 24 hours at constant temperature. The resulting film was taken out and washed with tap water, and tested for SUS/PP peel strength.
The test data are as follows:
Figure BDA0002978960240000091
the above embodiments are only used to further illustrate the steel plastic film for lithium battery of the present invention, and the preparation method and application thereof, but the present invention is not limited to the embodiments, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention fall within the protection scope of the technical scheme of the present invention.

Claims (6)

1. A preparation method of a steel-plastic film for a lithium battery is characterized by comprising the following steps:
a) taking a stainless steel foil with the thickness of 20 mu m, placing the stainless steel foil in a mixed solution of 40g/L sodium hydroxide, 25g/L sodium carbonate, 5g/L sodium silicate and 40g/L trisodium phosphate degreasing solution at the temperature of 70 ℃ for degreasing, then soaking the stainless steel foil in an acidic treatment solution, and then drying the treated stainless steel foil;
b) the treated stainless steel foil is put into anodic oxidation electrolyte for direct current anodic oxidation, the direct current voltage is 15-50V, and the current density is 1A-10A/dm2Oxidizing for 15-30 min to form an anodic oxide layer with the thickness of 1 nm-2 microns on at least the inner side surface of the stainless steel foil, and drying after oxidation; the anodic oxidation layer has a honeycomb porous structure; the electrolyte is an aqueous solution of 0.1-0.5M of oxyacid and 0.5-2 g/L of sodium fluoride, wherein the oxyacid is phosphoric acid;
c) coating a first adhesive layer on the outer side surface of the stainless steel foil in the protective atmosphere of nitrogen, and compounding a nylon layer on the outer side of the stainless steel foil through the first adhesive layer; coating a second adhesive layer on the inner side surface of the stainless steel foil under the protection atmosphere of nitrogen, and compounding the innermost layer on the inner side of the stainless steel foil through the second adhesive layer;
d) and d) placing the semi-finished product formed in the step c) at a constant temperature of 60-95 ℃ for 4320-7200 minutes, taking out the semi-finished product, cooling to room temperature, and then performing drawing at a drawing pressure of 0.2-0.5 Mpa to obtain the steel-plastic film for the lithium battery.
2. The method of claim 1, wherein: the thicknesses of the first binder layer and the second binder layer are respectively 3-12 mu m.
3. The production method according to claim 1, characterized in that: the thickness of the nylon layer is 20-100 mu m; the nylon layer adopts polyamide resin, including nylon 6, nylon 66, copolymer of nylon 6 and nylon 66, nylon 6,10 and poly-m-xylene adipamide.
4. The method of claim 1, wherein: the innermost layer is made of cast polypropylene and has a thickness of 40-80 mu m.
5. A steel-plastic film for a lithium battery prepared by the preparation method of any one of claims 1 to 4, characterized in that: the steel plastic film sequentially comprises a nylon layer, a first binder layer, a stainless steel foil layer, a second binder layer and an innermost layer from outside to inside, wherein an anodic oxidation layer is arranged on the inner side surface of the stainless steel foil layer, and the anodic oxidation layer has a honeycomb-shaped porous structure.
6. Use of the steel-plastic film according to claim 5 in the encapsulation of lithium batteries.
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