An outer packaging material for a lithium-ion battery device resistant to electrolyte corrosion

Abstract

The present invention discloses an outer packaging material for a lithium-ion battery device resistant to electrolyte corrosion, comprising an outer substrate resin layer, an intermediate metal layer, an inner adhesive layer and a heat-melting resin layer; the outer substrate resin layer is arranged on the intermediate metal layer, the intermediate metal layer is arranged on the inner adhesive layer, and the inner adhesive layer is arranged on the heat-melting resin layer; wherein the intermediate metal layer is subjected to corrosion resistance treatment to form an anti-corrosion layer. By subjecting the intermediate metal layer to corrosion resistance treatment, the shortcomings of the existing metal-plastic composite film, such as poor corrosion resistance and low peeling force between the metal layer and the heat-melting resin layer, are solved, and at the same time, the corrosion resistance and electrolyte resistance peeling strength of the metal-plastic composite film are improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to lithium-ion batteries, and particularly to an outer packaging material for a device for a lithium battery resistant to electrolyte corrosion. Background Art

[0002] At present, lithium-ion batteries are mainly divided into three categories: square, cylindrical, and soft-pack. Among them, the outer shells of square and cylindrical batteries mainly use hard shells such as aluminum alloy and stainless steel. The aluminum alloy outer shell can be made of aluminum, while the soft-pack outer shell made of laminated metal and resin uses a metal-plastic composite film, which greatly improves the problem of inflexible external shape design of hard-pack batteries.

[0003] The metal-plastic composite film is composed of an outer substrate resin layer, an outer adhesive layer, a middle metal layer, an inner adhesive layer, and a heat-sealing resin layer from the outside to the inside. As a battery outer packaging material, the metal-plastic composite film is required to have the performance of being resistant to electrolyte corrosion, so as to prevent problems such as liquid leakage from the battery shell and ensure the service life of the battery.

[0004] Generally, the metal in the metal-plastic composite film for lithium-ion battery outer packaging needs to be subjected to anti-corrosion treatment. In the case where the anti-corrosion treatment effect is not ideal, if moisture is mixed in the battery manufacturing process, it will react with the lithium salt in the electrolyte to generate corrosive hydrogen fluoride (HF). The hydrogen fluoride will pass through the heat-sealing resin layer and the inner adhesive layer to reach the surface of the middle metal layer, thereby corroding the metal and causing detachment between the metal and the heat-sealing resin layer. This increases the possibility of electrolyte leakage from the battery. Therefore, the anti-corrosion treatment of the metal has a great impact on the metal-plastic composite film.

[0005] Currently, the main components of the anti-corrosion treatment solution for the metal-plastic composite film are trivalent chromium compounds, fluorides, amino-phenolic resins, and phosphoric acid. After the metal is subjected to anti-corrosion treatment with this anti-corrosion solution, the corrosion resistance of the metal-plastic composite film can be improved in some ordinary electrolyte environments. However, during the long-term use of the battery, moisture may penetrate through the battery outer packaging, causing hydrogen fluoride (HF) to be generated in the electrolyte, and the anti-corrosion treatment effect of this anti-corrosion solution will be unsatisfactory, easily resulting in delamination of the metal-plastic composite film for lithium-ion batteries, affecting the popularization and use of the metal-plastic composite film in the field of lithium-ion batteries. Summary of the Invention

[0006] In view of this, the present invention expects to provide a metal-plastic composite film to solve the disadvantages of the existing metal-plastic composite film with poor corrosion resistance and low peel strength between the metal layer and the heat-sealing resin layer, and at the same time improve the corrosion resistance performance and electrolyte peel strength of the metal-plastic composite film.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] The present invention provides an outer packaging material for a lithium-ion battery device resistant to electrolyte corrosion, characterized in that: it includes an intermediate metal layer and an anti-corrosion layer formed by subjecting the intermediate metal layer to anti-corrosion treatment.

[0009] Characteristically, it further comprises an outer substrate resin layer, an inner adhesive layer and a heat-sealing resin layer; the outer substrate resin layer is disposed on the intermediate metal layer, the intermediate metal layer is disposed on the inner adhesive layer, and the inner adhesive layer is disposed on the heat-sealing resin layer; wherein the anti-corrosion layer is disposed between the intermediate metal layer and the inner adhesive layer.

[0010] Characteristically, it further comprises an outer adhesive layer, the outer substrate resin layer is disposed on the outer adhesive layer, and the outer adhesive layer is disposed on the intermediate metal layer; wherein the intermediate metal layer is disposed between the outer adhesive layer and the inner adhesive layer.

[0011] Characteristically, the metal of the intermediate metal layer is a nickel-plated steel sheet, and the thickness of the nickel plating layer of the nickel-plated steel sheet is 0.5 μm to 20 μm.

[0012] Characteristically, the carbon component and the metal component of the anti-corrosion layer are distributed in a gradient manner.

[0013] Characteristically, on the anti-corrosion layer on the side of the heat-sealing resin layer, the components of each element are distributed in a gradient manner. The carbon (C) content ratio on the outermost surface layer of the anti-corrosion layer on the side of the heat-sealing resin layer is greater than or equal to 40% and less than or equal to 100%, the nickel (Ni) content ratio is less than or equal to 10%, and the fluorine (F) content ratio is less than or equal to 10%; in the 40 nm layer below the surface layer of the anti-corrosion layer, the carbon (C) content ratio is less than or equal to 10%, the nickel (Ni) content ratio is greater than or equal to 30% and less than or equal to 100%, and the fluorine (F) content ratio is less than or equal to 20%.

[0014] Characteristically, after being subjected to liquid resistance treatment, in the 40 nm layer below the outermost surface layer of the anti-corrosion layer on the side of the heat-sealing resin layer, the carbon (C) content ratio is less than or equal to 10%, the nickel (Ni) content ratio is greater than or equal to 30%, and the fluorine element (F) content ratio is less than or equal to 25%.

[0015] Characteristically, the anti-corrosion layer is formed by drying an anti-corrosion liquid, and the anti-corrosion liquid mainly comprises a trivalent chromium compound, an inorganic acid, an organic resin, a cross-linking agent, and a solvent composed of water or an organic solvent, or a mixture thereof.

[0016] Characteristically, the cross-linking agent contains at least one of an amino resin, a melamine resin, a phenolic resin, an epoxy compound, a blocked isocyanate compound, an oxazoline compound, a carbodiimide compound, a condensate of formaldehyde and a C1-C4 alkyl monohydric alcohol, a condensate of phenol and formaldehyde, and derivatives of the above substances.

[0017] Characterized in that, the corrosion - resistant liquid for forming the corrosion - resistant layer is at least composed of one of chromium(III) compounds and cross - linking agents selected from chromium nitrate and chromium fluoride: the corrosion - resistant liquid for forming the corrosion - resistant layer contains titanium (Ti) compounds or zirconium (Zr) compounds, and their contents are 0 to 0.6% and 0 to 2.8% respectively.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1) The present invention provides an outer packaging material for a lithium - ion battery device resistant to electrolyte corrosion. By subjecting the intermediate metal layer to corrosion - resistant treatment, the disadvantages of poor corrosion resistance of the existing metal - plastic composite film and low peel strength between the metal layer and the hot - melt bonding resin layer are solved. At the same time, the corrosion resistance performance and the electrolyte - resistant peel strength of the metal - plastic composite film are improved.

[0020] 2) The present invention provides a manufacturing method for forming a corrosion - resistant layer by treating and drying the intermediate metal layer with a corrosion - resistant liquid. Through the configuration of the corrosion - resistant layer, the corrosion resistance of the outer packaging material for the lithium - ion battery device is significantly improved, showing excellent corrosion - resistant performance.

[0021] 3) The present invention provides a battery with high corrosion resistance. By using the above - mentioned outer packaging material for the corrosion - resistant battery device, the poor corrosion resistance of the battery device is reduced, and the disadvantage of low peel strength between the metal layer and the hot - melt bonding resin layer is improved, showing excellent corrosion - resistant performance.

[0022] 4) The present invention first proposes using a nickel - plated steel sheet material for the intermediate metal layer, and the elements in the surface corrosion - resistant layer are distributed in a gradient. By controlling the content of carbon (C) in the outermost layer, the content of intermediate metal elements and fluorine (F) elements at the inner layer (40 nm) of the corrosion - resistant layer, the initial peel strength between the intermediate metal layer and the hot - melt bonding resin layer of the metal - plastic composite film and the corrosion resistance in an electrolyte environment with a large amount of added water can be improved. Description of the Drawings

[0023] Figure 1 The structure of the outer packaging material for a lithium - ion battery device resistant to electrolyte corrosion provided by the present invention.

[0024] Component Label Explanation

[0025] 1…Outer substrate resin layer

[0026] 2…Intermediate metal layer

[0027] 3…Inner adhesive layer

[0028] 4…Hot - melt bonding resin layer

[0029] 5…Outer adhesive layer

[0030] 6…Corrosion - resistant layer Detailed Embodiments

[0031] The following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] The specific embodiments of the present invention provide an outer packaging material and a battery for a battery device with high corrosion resistance.

[0034] The present invention provides an outer packaging material (or a metal-plastic composite film) for a lithium-ion battery device resistant to electrolyte corrosion. The outer packaging material for the lithium-ion battery device resistant to electrolyte corrosion mainly consists of an outer substrate resin layer 1, an intermediate metal layer 2, an inner adhesive layer 3, and a heat-sealing resin layer 4; the outer substrate resin layer 1 is disposed on the intermediate metal layer 2, the intermediate metal layer 2 is disposed on the inner adhesive layer 3, and the inner adhesive layer 3 is disposed on the heat-sealing resin layer 4; wherein an anti-corrosion layer 6 formed by subjecting the intermediate metal layer 2 to corrosion-resistant treatment is disposed between the intermediate metal layer 2 and the inner adhesive layer 3.

[0035] Specifically, it further includes an outer adhesive layer 5. The outer substrate resin layer 1 is disposed on the outer adhesive layer 5, and the outer adhesive layer 5 is disposed on the intermediate metal layer 2, wherein the intermediate metal layer 2 is disposed between the outer adhesive layer 5 and the inner adhesive layer 3.

[0036] Specifically, the metal of the intermediate metal layer 2 is a nickel-plated steel sheet.

[0037] Specifically, the thickness of the nickel plating layer of the nickel-plated steel sheet is from 0.5 μm to 20 μm.

[0038] Specifically, the intermediate metal layer 2 is at least corrosion-resistant treated on the side of the heat-fusible resin layer 4 to form a corrosion-resistant layer 6. The special corrosion-resistant liquid used for the corrosion-resistant treatment mainly contains a trivalent chromium compound, an inorganic acid, an organic resin, a cross-linking agent, and a solvent composed of water or an organic solvent, or a mixture thereof. Among them, the proportions of the trivalent chromium compound, the inorganic acid, the organic resin, water or an organic solvent, or a mixture thereof as the solvent are 1.9 to 6%, 0.3 to 6%, 0.6 to 6%, and 78.6 to 97.2% respectively. The cross-linking agent is 0.01 to 30% by mass ratio in the solid components of the corrosion-resistant layer 6, or 0.05 to 15% by mass ratio calculated based on the solid components in the solution for forming the corrosion-resistant layer 6.

[0039] The corrosion-resistant liquid is dried to form the corrosion-resistant layer 6. The elemental components on the intermediate metal corrosion-resistant layer on the side of the heat-fusible resin layer 4 are distributed in a gradient. The carbon (C) content ratio in the outermost layer of the corrosion-resistant layer 6 on the side of the heat-fusible resin layer 4 is greater than or equal to 40%, while the nickel (Ni) content ratio is less than or equal to 10%, and the fluorine (F) content ratio is less than or equal to 10%. In the 40-nm layer below the surface layer of the corrosion-resistant layer 6, the carbon (C) content ratio is less than or equal to 10%, while the nickel (Ni) content ratio is greater than or equal to 30%, and the fluorine (F) content ratio is less than or equal to 20%.

[0040] Specifically, after the intermediate metal layer 2 forming the corrosion-resistant layer 6 is compounded with the heat-fusible resin layer 4 using an internal adhesive, it is soaked in an electrolyte solution with 1000 PPM of water (containing a mixed solvent of EC, DEC, and DMC with 1 mol / L LiPF 6 where the mass ratio of EC:DEC:DMC is 1:1:1) for 5 days. In the 40-nm layer below the outermost layer of the corrosion-resistant layer 6 on the side of the heat-fusible resin layer 4, the carbon (C) content ratio is less than or equal to 10%, while the nickel (Ni) content ratio is greater than or equal to 30%, and the fluorine element (F) content ratio is less than or equal to 25%.

[0041] Specifically, at least one of chromium nitrate and chromium fluoride is included in the trivalent chromium compound and the cross-linking agent used for forming the corrosion-resistant layer 6.

[0042] Specifically, the trivalent chromium compound is preferably at least one of chromium nitrate and chromium fluoride. Its function is to form a coordination cross-linked structure centered on chromium (Cr) atoms on the surface of the intermediate metal. The trivalent chromium compound plays a role in increasing the cross-linking degree of the anti-corrosion film on the surface of the intermediate metal.

[0043] Specifically, the cross-linking agent contains at least one of an amino resin, a melamine resin, a phenolic resin, an epoxy compound, a blocked isocyanate compound, an oxazoline compound, a carbodiimide compound, a condensate of formaldehyde and a C1-C4 alkyl monohydric alcohol, a condensate of phenol and formaldehyde, and derivatives of the above substances.

[0044] Specifically, the bridging agent contains at least one of inorganic bridging substances such as silicon compounds like silica, zirconium compounds like ammonium zirconium fluoride or ammonium zirconium carbonate, metal chelates like titanium chelates, and metal salts such as Ca, Al, Mg, Fe, Zn salts.

[0045] Specifically, the corrosion prevention liquid used to form the corrosion prevention layer 6 contains titanium (Ti) compounds or zirconium (Zr) compounds, with their contents being 0 to 0.6% and 0 to 2.8% respectively.

[0046] Specifically, the inorganic acid in the corrosion prevention liquid used to form the corrosion prevention layer 6 is at least composed of one of phosphoric acid, nitric acid, and hydrofluoric acid; the organic resin is at least composed of one of acrylic resins, methacrylic resins, hydroxy acrylic resins, polyvinyl alcohol resins, and phenolic resins; the Ti compound is at least composed of one of titanium fluoride and titanium nitrate, and the Zr compound is at least composed of one of zirconium fluoride and zirconium nitrate; the organic solvent is at least composed of one of isopropyl alcohol, ethanol, and ethylene glycol monobutyl ether.

[0047] Specifically, the organic resin is at least composed of one of acrylic resins, methacrylic resins, hydroxy acrylic resins, polyvinyl alcohol resins, olefin resins, and phenolic resins; the organic resin plays a role in improving the film-forming property of the corrosion prevention layer on the surface of the intermediate metal and bonding with the inner adhesive layer 3.

[0048] Specifically, the inorganic acid is at least composed of one of phosphoric acid, nitric acid, and hydrofluoric acid, and the inorganic acid plays a role in removing the oxide film on the surface of the intermediate metal.

[0049] Specifically, the titanium (Ti) compound or zirconium (Zr) compound acts as a sub-center crosslinking point and plays a role in enhancing the corrosion prevention of the surface of the intermediate metal.

[0050] Specifically, the organic solvent is at least composed of one of isopropyl alcohol, ethanol, and ethylene glycol monobutyl ether, and the organic solvent plays a role in reducing the surface tension of the corrosion prevention liquid and increasing the leveling property of the corrosion prevention liquid on the surface of the intermediate metal.

[0051] Specifically, if the content of the intermediate metal element in the surface layer of the corrosion prevention layer 6 with a gradient distribution of elements is more than 10%, it indicates that the thickness of the corrosion prevention layer 6 is too thin, and the effect of resisting hydrofluoric acid is not good.

[0052] Specifically, if the content of fluorine element (F) in the 40 nm layer below the surface layer of the corrosion prevention layer 6 after being resistant to the electrolyte is more than 25%, the effect of inhibiting the corrosion of hydrogen fluoride generated by the electrolyte is relatively low. During the long-term storage of the composite film, the peel strength between the inner adhesive layer 3 and the intermediate metal layer 2 may be significantly reduced.

[0053] The present invention provides a highly corrosion-resistant battery, which specifically includes an outer packaging material for a corrosion-resistant battery device as described above.

[0054] The corrosion protection layer 6 of the outer packaging material has the following characteristics:

[0055] In the packaging material for lithium-ion batteries, the corrosion protection layer prevents hydrogen fluoride generated by the reaction of the electrolyte with moisture from corroding the surface of the intermediate metal layer, prevents the separation between the intermediate metal layer and the heat-sealing resin layer, and at the same time maintains the uniformity of the surface of the intermediate metal layer, resulting in little change in adhesiveness (wettability), and has the effect of preventing delamination between the intermediate metal layer and the heat-sealing resin layer in the metal-plastic composite film. It is preferred to coat the corrosion protection liquid on at least the intermediate metal layer surface on the side opposite to the outer substrate resin side to form the corrosion protection layer, and it is more preferred to form the corrosion protection layer on both sides of the intermediate metal layer. Forming the corrosion protection layer on the intermediate metal layer surface in contact with the outer substrate resin layer can stabilize the uniformity of the surface of the intermediate metal layer, reduce the change in adhesiveness (wettability), and has the effect of preventing delamination between the outer substrate resin layer and the intermediate metal layer of the metal-plastic composite film during long-term storage in a high-temperature and high-humidity environment.

[0056] In this patent, the corrosion protection layer is characterized in that between the heat-sealing resin layer and the intermediate metal layer, the carbon component from the corrosion protection layer and the metal component from the intermediate metal layer are distributed in a gradient. That is, since the carbon component of the corrosion protection layer from the heat-sealing resin layer side increases the carbon component of the heat-sealing resin layer in contact with the corrosion protection layer, the stability of the composite of the heat-sealing resin layer and the intermediate metal can be ensured. If the adhesiveness of the inner adhesive layer is unstable, when the electrolyte penetrates, the adhesive force will decrease and the peel strength will be unstable. In addition, the measured intermediate metal component in the corrosion protection layer increases with the depth, indicating an increase in the adhesive force between the corrosion protection layer and the intermediate metal layer. When the soft-packaged lithium battery is used for a long time, the infiltrated moisture will react with the electrolyte to generate hydrogen fluoride, which will inhibit the dissolution of the corrosion protection layer on the intermediate metal layer and ensure the long-term stability of the peel strength between the inner adhesive layer and the intermediate metal layer. And this effect is improved with the increase of the fluoride component in the corrosion protection layer. It can be speculated that this is because the fluoride component improves the blocking property of hydrogen fluoride.

[0057] In addition, since the composition of the corrosion protection layer shows an inclined gradient distribution, it can be speculated that the effective components in the corrosion protection liquid will generate reaction products between the resin components of the corrosion protection layer on the heat-sealing resin layer side, such as reaction products of the resin and chromium (Cr), titanium (Ti), zirconium (Zr) in the corrosion protection layer, reaction products of inorganic acid and chromium (Cr), and reaction products of fluoride or inorganic acid in the intermediate metal layer and the corrosion protection layer.

[0058] On the basis described above, it is further defined that an anti-corrosion layer is formed by drying the anti-corrosion liquid. The carbon (C) content ratio on the outermost surface of the anti-corrosion layer on the side of the hot-melt bonding resin layer is greater than or equal to 40% and less than or equal to 100%, while the nickel (Ni) content ratio is less than or equal to 10%, and the fluorine (F) content ratio is less than or equal to 10%. In the 40-nm layer from the surface of the anti-corrosion layer, the carbon (C) content ratio is less than or equal to 10%, while the nickel (Ni) content ratio is greater than or equal to 30% and less than or equal to 100%, and the fluorine (F) content ratio is less than or equal to 20%. If the carbon (C) content ratio on the outermost surface of the anti-corrosion layer on the side of the hot-melt bonding resin layer is less than 40% or the content of the intermediate metal element is greater than 10%, as described above, the bonding strength between the anti-corrosion layer and the inner adhesive layer will be unstable. Affected by the electrolyte, the peel strength will decrease during storage. Or due to the increase in the content of metal elements, the internal insulation will be reduced. The reduction of the internal insulation will lead to a decrease in the battery life, or problems such as electrolyte leakage caused by electrical short circuits between the outer packaging material and the inside of the battery.

[0059] On the basis described above, it is further defined that after the intermediate metal layer forming the anti-corrosion layer is compounded with the hot-melt bonding resin layer using an inner adhesive, an electrolyte with 1000 PPM of water added (containing 1 mol / L LiPF 6Soak it in a mixed solvent of EC, DEC, and DMC (where the mass ratio of EC:DEC:DMC is 1:1:1) for 5 days. In the 40-nm layer from the outermost surface of the anti-corrosion layer on the side of the hot melt bonding resin layer, the carbon (C) content ratio is less than or equal to 10%, the nickel (Ni) content ratio is greater than or equal to 30%, and the fluorine (F) content ratio is less than or equal to 25%. If the fluorine (F) content in the 40-nm layer from the surface exceeds 25%, since the reaction products of the above anti-corrosion layer and the intermediate metal layer become less, the peel strength between the inner adhesive layer and the intermediate metal layer may be significantly reduced during long-term storage. As described above, the anti-corrosion layer formed by the reaction of the resin, acid, chromium forming the anti-corrosion layer and the elements of the intermediate metal layer has a high carbon (C) content on the side of the hot melt bonding layer, but as it approaches the side of the intermediate metal layer, it forms a compositional gradient inclined structure with more intermediate metal elements. Thus, while maintaining the adhesion to the hot melt bonding layer, even when it comes into contact with the electrolyte and electrolyte penetration or the reaction between the electrolyte and water occurs, it can still inhibit the penetration of hydrogen fluoride that can corrode the intermediate metal. Moreover, in order to inhibit the penetration of hydrogen fluoride and the electrolyte, the inclined structure is a cross-linked structure. An important factor in forming the cross-linked structure is the cooperation between the anti-corrosion layer and the intermediate metal layer and the heat treatment process for the cross-linking reaction. It should be particularly noted that under inappropriate heat treatment conditions, sufficient adaptability to the battery contents cannot be obtained. The ratio of the fluorine (F) element relative to the elements of the intermediate metal layer refers to the ratio of the detected fluorine (F) element content when the element content from the intermediate metal layer detected by the following method (XPS-ESCA method) is set to 1.

[0060] In this patent, the elements or components of the intermediate metal layer refer to the component elements constituting the intermediate metal layer and the intermediate metal layer elements detected in the reaction products formed by the reaction of the above anti-corrosion layer constituent materials or electrolytes, etc. with the intermediate metal layer. When the intermediate metal layer is a steel plate treated by nickel plating, although it is a component from nickel, it also includes other added alloy components.

[0061] When measuring elements by the method described below, the elements detected in this patent, in addition to the components from the intermediate metal layer, also include the constituent elements of the anti-corrosion layer and the electrolyte. For example, carbon (C), oxygen (O), nitrogen (N), chromium (Cr), phosphorus (P), silicon (Si), fluorine (F), titanium (Ti), zirconium (Zr), cerium (Ce), etc.

[0062] Sometimes metal elements are added in trace amounts to the material for forming the anti-corrosion layer. During measurement, in cases where they cannot be distinguished from the elements from the intermediate metal layer, they can all be measured as metal elements from the intermediate metal layer, or it can also be assumed that the metal elements added to the anti-corrosion layer are evenly dispersed in the anti-corrosion layer, and the amount of metal elements added to the anti-corrosion layer is subtracted from the detected amount of metal elements.

[0063] When the anti-corrosion layer is multi-layered, it can be judged by a single layer in contact with the intermediate metal layer, or by the whole of the multi-layer part.

[0064] As an example of the anti-corrosion layer, the anti-corrosion layer of the present invention may mainly include a film obtained by a coating-type anti-corrosion treatment, and the coating-type anti-corrosion treatment contains at least one component selected from oxide sols of rare earth elements, anionic polymers, and cationic polymers. The coating agent may also contain phosphoric acid, phosphates, and a cross-linking agent for cross-linking the polymer. In the rare earth element oxide sol, fine particles of rare earth element oxides (for example, particles with an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. As the rare earth element oxide, it mainly contains cerium oxide, yttrium oxide, neodymium oxide, lanthanum oxide, etc. From the viewpoint of further improving the adhesion, cerium oxide is preferred. The rare earth element oxides contained in the anti-corrosion layer may be used alone or in combination of two or more. As the liquid dispersion medium of the rare earth element oxide sol, various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester compound-based solvents, and ether-based solvents can be used, and water is preferred. As the cationic polymer, it mainly includes polyethyleneimine, a complex ion polymer complex formed by a polymer having polyethyleneimine and a carboxylic acid, a primary amine graft copolymerized acrylic resin grafted with a primary amine on an acrylic main chain, polyacetic acid or its derivatives, and amino-phenol. In addition, as the anionic polymer, a copolymer mainly composed of poly(meth)acrylic acid or its salt, or (meth)acrylic acid and its salt is preferred. The cross-linking agent is preferably at least one of a compound having any functional chemical group such as an isocyanate chemical group, a glycidyl chemical group, a carboxyl chemical group, and an oxazoline chemical group, and a silane coupling agent.

[0065] More specifically, as an example of the anti-corrosion layer, the anti-corrosion liquid of the present invention is mainly an aqueous solution composed of a trivalent chromium compound, an inorganic acid, an organic resin, a cross-linking agent, a titanium (Ti) compound or a zirconium (Zr) compound, and an organic solvent. Among them, the proportions of the trivalent chromium compound, the inorganic acid, the organic resin, the titanium (Ti) compound or the zirconium (Zr) compound, the organic solvent, and water are 1.9 to 6%, 0.3 to 6%, 0.6 to 6%, 0 to 0.6%, 0 to 2.8%, and 78.6 to 97.2% respectively. The cross-linking agent is 0.01 to 30% by mass ratio in the solid components of the anti-corrosion layer, or 0.05 to 15% by mass ratio calculated based on the solid components in the solution for forming the anti-corrosion layer.

[0066] The trivalent chromium compound and the crosslinking agent are at least composed of one of chromium nitrate and chromium fluoride; the inorganic acid is at least composed of one of phosphoric acid, nitric acid, and hydrofluoric acid; the organic resin is at least composed of one of acrylic resin, methacrylic resin, hydroxy acrylic resin, polyvinyl alcohol resin, olefin resin, and phenolic resin; the titanium (Ti) compound is at least composed of one of titanium fluoride and titanium nitrate; the zirconium (Zr) compound is composed of one of zirconium fluoride and zirconium nitrate; the organic solvent is at least composed of one of isopropyl alcohol, ethanol, and ethylene glycol monobutyl ether.

[0067] By adding a crosslinking agent, the crosslinking density of the anti-corrosion layer can be increased, and the tolerance of the anti-corrosion layer to the electrolyte as the content and hydrogen fluoride generated by the reaction of the electrolyte with water can be stabilized. More preferably, a crosslinking agent can be added to the anti-corrosion liquid for forming the anti-corrosion layer.

[0068] The crosslinking agent can use an organic crosslinking agent and an inorganic crosslinking agent. The inorganic crosslinking agent includes at least one of silicon compounds such as silica, zirconium compounds such as ammonium zirconium fluoride and ammonium zirconium carbonate, metal chelates such as titanium chelate, and inorganic crosslinking substances of metal salts such as Ca, Al, Mg, Fe, and Zn. The organic crosslinking agent can preferably be at least one of amino resin, melamine resin, phenolic resin, epoxy compound, blocked isocyanate compound, oxazoline compound, carbodiimide compound, condensate of formaldehyde and a C1-C4 alkyl monohydric alcohol, condensate of phenol and formaldehyde, and derivatives of the above substances.

[0069] The content of the crosslinking agent in the solid component of the anti-corrosion layer is 0.01 to 30% by mass ratio, or calculated based on the solid component in the solution for forming the anti-corrosion layer, the content is 0.05 to 15% by mass ratio. When the content of the crosslinking agent is less than 0.05%, the degree of improving the corrosion resistance by adding the crosslinking agent is very low. When the content exceeds 15%, the crosslinking density of the anti-corrosion layer becomes large, the anti-corrosion layer is too hard, and the anti-corrosion layer is prone to cracking and peeling during the molding process, resulting in a decrease in corrosion resistance.

[0070] In addition, as the anti-corrosion layer formed by chemical conversion treatment, there are now known various anti-corrosion liquids, mainly containing phosphates, nitric acid, chromates, fluorides, and rare earth oxides, etc.

[0071] As a chemical conversion treatment using phosphates and chromates, it mainly includes, for example, chromic acid chromium treatment, chromium phosphate treatment, phosphoric acid-chromate treatment, chromate treatment, etc. As the chromium compounds used in these treatments, chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium metaphosphate, chromium acetate, chromium chlorinated, chromium sulfate can be cited. The chromate treatment methods mainly include etched chromate treatment, electrolytic chromate treatment, coated chromate treatment, etc., but coated chromate treatment is preferred. In this coated chromate treatment, on the degreased treatment surface, a treatment liquid mainly composed of metal phosphates such as chromium phosphate (Cr) salt, titanium phosphate (Ti) salt, zirconium phosphate (Zr) salt, lead (Zn) phosphite salt, etc. and mixtures of these metal salts, or a treatment liquid mainly composed of non-metal phosphates and mixtures of these non-metal salts is mixed with a synthetic resin as the treatment liquid, and is coated and dried by a known coating method such as roll coating method, gravure printing method, dipping method, etc. The treatment liquid can use various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester compound-based solvents, ether-based solvents, etc., but water is preferred. In addition, as the resin component used therein, a water-soluble polymer such as aminoated phenol or polyacrylic acid-based resin can be selected.

[0072] As an example of the anti-corrosion layer, a particulate substance in which metal oxides such as alumina, titanium oxide, cerium oxide, tin oxide and precipitated barium sulfate are dispersed in phosphoric acid is coated on the surface of the intermediate metal layer and sintered at 150 °C or higher to form an anti-corrosion layer.

[0073] As a method for coating the anti-corrosion liquid, first, at least the inner heat-bonding resin layer of the intermediate metal layer is degreased by treatment methods such as alkali dipping method, electrolytic cleaning method, acid cleaning method, electrolytic acid cleaning method, oxygen activation method, heat treatment (annealing treatment) during rolling, etc. Secondly, using the anti-corrosion liquid of the present invention, it is coated on the surface of the intermediate metal layer by means of bar coating method, roll coating method, gravure coating method, dipping method, etc., and a high-temperature chemical reaction acts on it. The wet film amount of the anti-corrosion liquid coated on the intermediate metal layer ranges from 1.6 to 3.2 g / m 2 , and after coating the anti-corrosion liquid, it is heat-treated at a high temperature of 130 to 200 °C for 0.5 to 5 min to form an anti-corrosion layer.

[0074] The thickness of the anti-corrosion layer is not particularly limited, but from the perspective of the adhesion between the intermediate metal layer and the hot-melt resin layer, it is preferably 1 nm to 3.0 μm, and more preferably 1 nm to 1.5 μm.

[0075] Among the trivalent chromium compounds and crosslinking agents in the anti-corrosion liquid for forming the anti-corrosion treatment layer, one of chromium nitrate and chromium fluoride is preferred. Chromium nitrate and chromium fluoride will react with the resin, intermediate metal layer, and inorganic acid in the anti-corrosion layer. Chromium fluoride can improve the ability of the anti-corrosion layer to resist hydrogen fluoride, and can ensure the stability of the peel strength between the inner hot-melt bonding resin layer and the intermediate metal layer during long-term storage.

[0076] Titanium (Ti) compounds or zirconium (Zr) compounds can improve the stable uniformity of the reaction of chromium with resin, metal, and inorganic acid. The titanium (Ti) compound is preferably titanium fluoride or titanium nitrate. The zirconium (Zr) compound is preferably zirconium fluoride or zirconium nitrate.

[0077] The inorganic acid can remove the surface oxide film of the intermediate metal layer, enabling the metal to react quickly with the components in the anti-corrosion layer to form a firm chromium reaction product. Thereby, the stability of the peel strength between the hot-melt bonding resin layer and the intermediate metal layer during long-term storage of the composite film can be ensured. As the inorganic acid, one of phosphoric acid, nitric acid, and hydrofluoric acid is preferred.

[0078] As mentioned above, the organic resin can improve the bonding stability between the intermediate metal layer and the inner adhesive layer. In addition, in the anti-corrosion layer, the reaction products of chromium (Cr), titanium (Ti), and zirconium (Zr) are resistant to the electrolyte and hydrogen fluoride generated by the electrolyte, so the stability of the peel strength between the hot-melt bonding resin layer and the intermediate metal layer can be improved. As the organic resin, one containing acrylic resin, methacrylic resin, hydroxy acrylic resin, polyvinyl alcohol resin, olefin resin, or phenolic resin is preferred.

[0079] The organic solvent can be used alone as a solvent or added to water. It can improve the wettability of the anti-corrosion liquid and the reaction stability between the anti-corrosion layer and the intermediate metal layer. In addition, it can reduce the surface tension of the anti-corrosion liquid and improve the uniformity of the coating film. As the organic solvent, one can be selected from isopropyl alcohol, ethanol, and ethylene glycol monobutyl ether.

[0080] The characteristics of the outer substrate resin layer 1 of the outer packaging material are as follows:

[0081] In the present invention, the outer substrate resin layer is provided for the purpose of functioning as a substrate for the packaging material of the lithium-ion battery. The outer substrate resin layer is located on the outer layer side of the packaging material for the lithium-ion battery.

[0082] Regarding the raw materials for forming the outer substrate resin layer, as the function of the substrate, there is no particular limitation as long as it has at least insulation properties.

[0083] There are various methods for manufacturing the outer substrate resin layer. For example, it can be directly formed into a resin film product from resin, or it can be a coated resin product. As the resin film, it can be an un-stretched film or a stretched film. As the stretched film, it can be a uniaxially stretched film or a biaxially stretched film, preferably a biaxially stretched film. As the manufacturing method of the biaxially stretched film, for example, the stepwise biaxial stretching method, the blown film method, the synchronous stretching method. As the resin coating method, for example, the roll coating method, the microgravure coating method, the extrusion coating method, etc.

[0084] As the resin for forming the outer substrate resin layer, for example, polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenolic resin and other resins or modified products of these resins. In addition, the resin for forming the outer substrate resin layer can be a copolymer of these resins, or a modified product of the copolymer, or a mixture of these resins.

[0085] Single layer or multiple layers are preferred

[0086] As the resin for forming the outer substrate resin layer, among them, polyester and polyamide are preferably listed.

[0087] As polyester, specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, copolyester, etc. can be cited. In addition, as the copolyester, copolyesters mainly composed of ethylene terephthalate repeating units can be cited. Specifically, a copolymer polyester formed by polymerizing ethylene terephthalate as the main body of the repeating unit with ethylene isophthalate (hereinafter simply referred to as copolyester (terephthalate / isophthalate)), copolyester (terephthalate / adipate), copolyester (terephthalate / sodium isophthalate), copolyester (terephthalate / phenyl-dicarboxylate), copolyester (terephthalate / decane dicarboxylate), etc. These polyesters can be used alone, or two or more of them can be used in combination.

[0088] In addition, as polyamide, specifically, aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66 can be cited; hexamethylenediamine-isophthalic acid-terephthalic acid copolyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (I represents isophthalic acid, t represents terephthalic acid) containing structural units from terephthalic acid and / or isophthalic acid, and aromatic polyamides such as polyamide MXD6 (polyamide PACM6 (poly-bis(4-aminocyclohexyl)methane azide amide)). These polyamides can be used alone, or two or more of them can be used in combination.

[0089] The outer substrate resin layer preferably contains at least one of a polyester film, a polyamide film, and a polyolefin film; preferably contains at least one of a stretched polyester film, a stretched polyamide film, and a stretched polyolefin film; more preferably contains at least one of a stretched polyethylene terephthalate film, a stretched polybutylene terephthalate film, a stretched nylon film, and a stretched polypropylene film; still more preferably contains at least one of a biaxially stretched polyethylene terephthalate film, a biaxially stretched polybutylene terephthalate film, a biaxially stretched nylon film, and a biaxially stretched polypropylene film.

[0090] The outer substrate resin layer can be a single layer or composed of two or more layers. When the outer substrate resin layer is composed of two or more layers, the outer substrate resin layer can be a composite film formed by the action of an adhesive, or a resin composite film formed by co-extruding resins to form two or more layers. In addition, the resin composite film formed by co-extruding resins to form two or more layers can be used as the outer substrate resin layer in an unstretched state, or can be used as the outer substrate resin layer after uniaxial stretching or biaxial stretching.

[0091] In the outer substrate resin layer, specific examples of the laminate of two or more resin films can include a composite film of a polyester film and a nylon film, a nylon composite film of two or more layers, a polyester composite film of two or more layers, etc. A stretched nylon film and a stretched polyester film laminate, a nylon composite film of two or more layers, and a polyester composite film of two or more layers are preferred. For example, when the outer substrate resin layer is a two-layer resin composite film, a composite film of a polyester resin film and a polyester resin film, a composite film of a polyamide resin film and a polyamide resin film, or a composite film of a polyester resin film and a polyamide resin film is preferred, and a composite film of a polyethylene terephthalate film and a polyethylene terephthalate film, a composite film of a polybutylene terephthalate film and a polybutylene terephthalate film, a composite film of a nylon film and a nylon film, or a composite film of a polyethylene terephthalate film and a nylon film is more preferred. In addition, since polyester resin is difficult to change color when the electrolyte adheres to the surface, when the outer substrate resin layer is a resin composite film of two or more layers, a polyester resin film is preferably located on the outermost layer of the outer substrate resin layer.

[0092] When the outer substrate resin layer is a resin composite film of two or more layers, the two or more resin films can also be laminated with an adhesive. As a preferred adhesive, a glue solution having the same composition as the outer layer adhesive can be used. In addition, as a method for laminating two or more resin films, there is no particular limitation, and dry lamination, sandwich lamination, extrusion lamination, thermal lamination, etc. can be adopted, with dry lamination being preferred. When performing lamination by dry lamination, a reactive polyurethane adhesive is preferably used as the reactive adhesive for the outer layer. At this time, the thickness of the adhesive layer can be about 2 to 5 μm. When forming the outer substrate resin layer by resin coating, the resin can be first dissolved in an organic solvent, and the outer substrate resin layer can be formed by coating. The resins for coating can be phenolic resins such as polyamide resin, polyimide resin, polyurethane resin, epoxy resin, acrylic resin, polyester resin, polyamide resin, polyimide resin, fluorine-based copolymer resin, polyester resin, amino resins such as polyester resin, polycarbonate resin, urea resin, and melamine resin.

[0093] In addition, one or more additives such as lubricants, flame retardants, anti-blocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents can be added to the surface and inside of the outer substrate resin layer.

[0094] From the perspective of improving the formability of packaging materials for lithium-ion batteries, it is preferable to coat a lubricant on the surface of the outer substrate resin layer. As the lubricant, there is no particular limitation, and amide-based lubricants are preferred. Amide lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, hydroxymethyl amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides, etc. Taking saturated fatty acid amides as an example, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, etc. can be used. Taking unsaturated fatty acid amides as an example, oleic acid amide, erucic acid amide, etc. can be cited. Substituted amides include N-oleopalmitic acid amide, N-stearamide, N-stearamide, N-oleostearamide, and N-stearamide. In addition, hydroxymethyl amides include hydroxymethyl stearic acid amide, etc. Saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene bisoctanoic acid amide, ethylene dilauric acid amide, ethylene bisstearic acid amide, ethylene bis-hydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, n,n'-distearyl adipic acid amide, n,n'-distearyl sebacic acid amide, etc. Unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, n,n'-dioleyl adipic acid amide, and n,n'-dioleyl sebacic acid amide. Fatty acid ester amides include stearamide ethyl stearate, etc. In addition, aromatic bisamides include m-xylene bisstearic acid amide, m-xylene bis-hydroxystearic acid amide, n,n'-distearyl isophthalic acid amide, etc. The lubricant can be used alone as one kind, or two or more kinds can be used in combination.

[0095] When there is a lubricant on the surface of the outer substrate resin layer, there is no particular limitation on the coating amount, and it is preferably coated about 3 mg / m 2 or more, and more preferably coated 4 to 30 mg / m 2 or so.

[0096] The lubricant present on the surface of the outer substrate resin layer can be the lubricant exuded from the substrate resin layer containing the lubricant, or can be a lubricant coated on the surface of the outer substrate resin layer.

[0097] Regarding the thickness of the outer substrate resin layer, as long as it can perform the function of a substrate, there is no particular limitation. When the outer substrate resin layer is a resin composite film of two or more layers, the thickness of the resin films constituting each layer is preferably about 2 to 30 μm respectively.

[0098] In the present invention, the outer substrate resin layer may be a single-layer or multi-layer composite film formed of one or more polymer materials such as blown film nylon, synchronous or asynchronous biaxially stretched nylon, synchronous or asynchronous biaxially stretched polyethylene terephthalate (PET), synchronous or asynchronous biaxially stretched polybutylene terephthalate (PBT), and polyimide (PI). The outer substrate resin can be adhered to the intermediate metal layer by one or a combination of co-extrusion, coating, lamination, and heat lamination. The total thickness of the outer substrate resin layer is 5 to 35 μm. When the thickness is less than 5 μm, the formability and insulation are relatively poor. In addition, if it exceeds 35 μm, the total thickness of the metal-plastic composite film is too thick, and the advantage of the metal-plastic composite film, i.e., flexibility, will deteriorate.

[0099] The characteristics of the outer adhesive layer 5 of the outer packaging material are as follows:

[0100] In the packaging material for a lithium-ion battery of the present invention, when the outer substrate resin layer and the intermediate metal layer are laminated, it can be determined whether to provide an outer adhesive layer as needed. The outer adhesive layer is a layer formed for the purpose of improving the adhesiveness between the outer substrate resin layer and the intermediate metal layer, etc.

[0101] The outer adhesive layer is formed of an adhesive that can bond the outer substrate resin layer and the intermediate metal layer. The adhesive used to form the outer adhesive layer is not limited. For example, it can be a two-component curable adhesive (two-component adhesive), and it can also be a one-component curable adhesive (one-component adhesive). Moreover, the adhesive used when forming the outer adhesive layer can be any one of chemical reaction type, solvent evaporation type, heat melting type, heat pressing type, etc. In addition, the outer adhesive layer can be a single layer or multiple layers.

[0102] The outer adhesive layer is a two-component polyurethane adhesive formed with polyester polyol and polyurethane-modified polyol as the main diol component, and aromatic or aliphatic isocyanate as the curing agent. The curing agent can be selected according to the functional groups of the bonding components, such as appropriately selected from polyfunctional epoxy resins, polymers containing methanesulfonic acid, polyamine resins, inorganic acids, etc. In addition, the main components used in the outer adhesive layer include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, copolyester, etc.; polyether resins; polyurethane resins; epoxy resins; phenolic resins; polyamide resins such as nylon 6, nylon 66, nylon 12, copolyamide; polyolefin resins such as polyolefin, cyclic polyolefin, acid-modified polyolefin, acid-modified cyclic polyolefin; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimide resins; polycarbonate; amino resins such as urea resin, melamine resin; rubbers such as chloroprene rubber, nitrile rubber, styrene-butadiene rubber; silicone resins, etc. These bonding components can be used alone, or two or more of them can be used in combination.

[0103] In the present invention, a more preferred combination for the outer adhesive layer is one or two of binary or polyvalent polyester and polyurethane-modified polyester and isocyanate. The isocyanate is not particularly limited to a compound having two or more isocyanate groups in the molecule. For example, a mixture of one or more of polymers such as isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), 1,6-hexamethylene diisocyanate (HDI), etc.

[0104] In addition, as long as the adhesiveness is not impaired, other components are allowed to be added to the outer adhesive layer, and it can contain colorants, thermoplastic elastomers, tackifiers, fillers, etc. By containing a colorant in the outer adhesive layer, the packaging material for lithium-ion batteries can be colored. As the colorant, colorants such as pigments and dyes can be used. In addition, one kind of colorant can be used, or two or more kinds can be mixed and used.

[0105] The type of pigment is not particularly limited as long as it is within the range that does not damage the adhesiveness of the outer adhesive layer. As organic pigments, for example, azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indanthrene-based, perylene-based, isoindoline-based pigments, etc. can be used; as inorganic pigments, carbon black-based, titanium oxide-based, cadmium-based, lead-based, isoindoline-based pigments, etc. can be used.

[0106] Among the colorants, for example, in order to make the appearance of the packaging material for lithium-ion batteries black, carbon black is preferred.

[0107] As the average particle diameter of the pigment, there is no particular limitation, and those around 0.05 to 5 μm, preferably around 0.08 to 2 μm can be selected. In addition, the average particle diameter of the pigment is the median particle diameter measured by a laser diffraction / scattering particle size distribution measuring device.

[0108] As the pigment content in the outer adhesive layer, there is no particular limitation as long as the packaging material for lithium ion batteries is colored, and preferably around 5 to 60%, more preferably around 10 to 40%.

[0109] The thickness of the outer adhesive layer is not particularly limited as long as it can bond the outer base resin layer 1 and the intermediate metal layer 2. As a preferred range, those around 1 to 10 μm can be cited, and more preferably around 2 to 5 μm.

[0110] The coloring layer is a layer provided between the outer base resin layer and the intermediate metal layer as needed. The colored metal-plastic composite film can be directly formed by adding a pigment to the outer adhesive layer, or a coloring layer can be formed between the outer base resin layer and the outer adhesive layer. In addition, a coloring layer can also be provided on the outer side of the outer base resin layer.

[0111] The coloring layer can be formed, for example, by coating an ink containing a colorant on the surface of the outer base resin layer 1, the surface of the outer adhesive layer A, or the surface of the intermediate metal layer. As the colorant, colorants such as pigments and dyes can be used. In addition, only 1 type of colorant can be used, or 2 or more types can be mixed and used.

[0112] As a specific example of the colorant contained in the coloring layer, the examples described for the outer adhesive layer can be referred to.

[0113] The characteristics of the intermediate metal layer 2 of the outer packaging material are as follows:

[0114] In the outer packaging material for lithium ion batteries, the intermediate metal layer is a barrier layer that can at least inhibit the intrusion of moisture.

[0115] In this patent, as the metal material used for the intermediate metal layer, a steel plate treated with nickel plating is adopted.

[0116] When the intermediate metal layer is a nickel-plated steel plate, the nickel plating layer has an anti-corrosion effect such as rust prevention, and also has an effect of improving the surface cleanliness. By forming the anti-corrosion layer described below on the nickel-plated surface, the electrolyte resistance is dramatically improved through the anti-corrosion property of the nickel plating layer and the synergistic effect with the anti-corrosion layer. The thickness of the nickel plating layer can be 20 μm or less. It is preferably 1 μm or more and 5 μm or less. When it exceeds 20 μm, although the anti-corrosion performance is improved, cracks are likely to occur due to external pressure loads such as molding.

[0117] In addition, the surface cleanliness of the intermediate metal layer has a great influence on the anti-corrosion effect, so the management of the surface cleanliness of the intermediate metal layer becomes very important. The surface cleanliness can be managed by a method using the wettability test with a wetting reagent as an index or a method using the contact angle as an index. As an index of wettability, it is D grade or above, preferably B grade. In addition, as an index of the contact angle, when tested with pure water, the contact angle is 25° or less, preferably 20° or less, more preferably 15° or less. When the wettability is lower than D grade or the contact angle exceeds 25°, the reactivity with the anti-corrosion layer described later or the initial adhesion will deteriorate. If the reactivity deteriorates, the reaction between the anti-corrosion layer and the intermediate metal layer becomes insufficient, and the penetration resistance to the electrolyte as the battery content and the resistance to hydrogen fluoride generated in the reaction of the electrolyte and water will decrease. Over time, the adhesion of the anti-corrosion layer to the intermediate metal layer decreases, the anti-corrosion layer dissolves, and the intermediate metal layer and the anti-corrosion layer may peel off, thus shortening the battery life. The same situation also occurs when the initial adhesion between the anti-corrosion layer and the intermediate metal layer deteriorates.

[0118] The test method for the surface wettability of the intermediate metal layer can adopt "National Standard of the People's Republic of China GB / T225638.5-2016, Metallic materials - Methods of test - Part 5: Detection of wettability". The test method for the contact angle of the intermediate metal layer can adopt "National Standard of the People's Republic of China GB / T22638.9-2008, Metallic materials - Methods of test - Part 9: Determination of hydrophilicity".

[0119] The inner adhesive layer 3 of the outer packaging material has the following characteristics:

[0120] In the packaging material for lithium-ion batteries of the present invention, the inner adhesive layer is an intermediate layer provided to firmly bond the intermediate metal layer and the heat-sealable resin layer.

[0121] The inner adhesive layer is formed of a resin capable of bonding the intermediate metal layer and the heat-sealable resin layer. For the above-mentioned heat-sealable resin layer, polyolefins, cyclic polyolefins, etc. can be used, and modified polyolefin resins such as carboxylic acid-modified polyolefins, carboxylic acid-modified cyclic polyolefins, methacrylic acid-modified polyolefins, acrylic acid-modified polyolefins, crotonic acid-modified polyolefins, and imide-modified polyolefins can also be used. From the viewpoint of improving the adhesion between the intermediate metal layer and the heat-sealable resin layer, as the modified polyolefin, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, polyamide, etc. modified polyolefin resins are preferred. The resin constituting the inner adhesive layer may or may not contain a polyolefin main chain, and it is preferably a resin containing a polyolefin main chain. Whether the resin constituting the inner adhesive layer contains a polyolefin main chain can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc., and no particular limitation is imposed on the analysis method. The polyolefin and its modified resin used in the inner adhesive are the same as the resin used in the heat-sealable resin layer, and it is a polypropylene resin or a copolymer of propylene and ethylene.

[0122] From the perspective of the long-term use stability of the packaging material for lithium-ion batteries, the inner adhesive layer can also be a resin combination containing an acid-modified polyolefin and a curing agent. As the acid-modified polyolefin, maleic anhydride or acrylic acid-modified polyolefin is particularly preferred.

[0123] As the curing agent, there is no particular limitation as long as it is a curing agent that cures the acid-modified polyolefin. Epoxy-based curing agents, polyfunctional isocyanate-based curing agents, carbodiimide-based curing agents, oxazoline-based curing agents, etc. can be used.

[0124] As the epoxy-based curing agent, any compound having at least one epoxy group can be used without particular limitation. For example, epoxy resins such as bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerol polyglycidyl ether, and polyglycerol polyglycidyl ether are used.

[0125] As the polyfunctional isocyanate-based curing agent, there is no particular limitation as long as it is a compound having two or more isocyanate groups in the molecule. For example, isophorone diisocyanate (PDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), components after polymerization or addition of the above substances, or reactants of such mixtures with other polymers are used.

[0126] As the carbodiimide-based curing agent, there is no particular limitation as long as it is a compound having at least one carbodiimide group (-N = C = N-) in the molecule. A polycarbodiimide compound having at least two or more carbodiimide groups is preferred.

[0127] As the oxazoline-based curing agent, there is no particular limitation as long as it is a compound having an oxazoline skeleton.

[0128] From the viewpoint of improving the adhesiveness between the inner adhesive layer and the heat-fusible resin layer, etc., the curing agent may also be composed of two or more compounds.

[0129] Regarding the thickness of the inner adhesive layer, as long as it has the function of an adhesive layer, there is no particular limitation, and it is preferably about 1 to 80 μm, more preferably about 1 to 50 μm.

[0130] The main component of the inner adhesive layer in the present invention is a single-layer or two-layer or more film layer formed by a modified polyolefin resin, a polyolefin resin, a block copolymerized polypropylene resin (B-PP) with a polypropylene (PP) content exceeding 50%, a random copolymerized polypropylene resin (R-PP), a homopolypropylene resin (H-PP), or a mixture of two or more of them.

[0131] When laminating the intermediate metal layer and the heat-fusible resin layer, a solution-type inner adhesive layer method or a hot-melt type inner adhesive resin layer method can be used for the inner adhesive layer.

[0132] The solution-type inner adhesive layer uses an acid-modified polyolefin resin as the main agent and one or two or more of isocyanates, epoxy resins, or oxazoline-based compounds, etc. as the curing agent, or amine compounds such as triethylamine and N,N-dimethylethanolamine as the curing agent. After being dissolved in at least one or two or more solvents such as water, ethanol, isopropanol, ethyl acetate, methyl ethyl ketone, toluene, and methyl cyclohexane, it is uniformly coated on the surface of the metal that has been subjected to anti-corrosion treatment, and the solvent is volatilized by heating to make the thickness of the inner adhesive layer reach the desired effect, preferably about 1 to 10 μm, more preferably 1 to 5 μm. When the thickness is less than 1 μm, the thickness becomes thinner, which will reduce the adhesive force between the intermediate metal layer and the heat-fusible resin layer, and the adhesiveness becomes a problem. When the thickness exceeds 10 μm, the adhesiveness is not a problem, but in the case of curing agent reaction, a hard resin layer will be formed, the bending resistance will become poor, the flexibility of the metal-plastic composite film will decrease, and there is a risk of cracks occurring during bending and peeling of the intermediate metal layer and the heat-fusible resin layer. The melting point of the acid-modified polyolefin resin in the solution-type inner adhesive is in the range of 60 to 155 °C, the weight-average molecular weight is in the range of 10,000 to 150,000, and the acid value of the solution-type inner adhesive is in the range of 0.5 to 200 mgKOH / g. Under the condition of no curing agent, the solution-type inner adhesive is mainly composed of an acid-modified polyolefin and an amine compound as the curing agent, and the ratio of the acid-modified polyolefin to the amine compound is 10:1 to 125:1, preferably 15:1 to 50:1. The acid used for the modified polyolefin is maleic acid, fumaric acid, methacrylic acid, etc., and the amine compound is at least one of triethylamine or N,N-2-methylethanolamine. The acid-modified polyolefin is polypropylene with a melting point of 110 °C or higher, and the content of polypropylene is 50% or more.

[0133] If the melting point is below 60°C, the heat resistance is relatively low, and the intermediate metal layer and the hot-melt bonding resin layer may peel off at high temperatures. Additionally, if it exceeds 155°C, the heat resistance is good, but during the reaction with the curing agent, a hard resin layer is formed, resulting in poor flexibility. Consequently, the flexibility of the metal-plastic composite film decreases, or cracks occur during bending, and there is a situation where the intermediate metal layer and the hot-melt bonding resin layer peel off. If the weight-average molecular weight is below 10,000, the resin has high fluidity during heating, and during heat sealing, the thickness severely thins, and the adhesion strength between the intermediate metal layer and the hot-melt bonding resin layer (in the case of reacting with the curing agent) becomes low, leading to sealing problems. If the weight-average molecular weight exceeds 150,000, then for the intermediate metal layer and the hot-melt bonding resin layer (in the case of reacting with the curing agent), a hard resin layer is formed, the flexural resistance deteriorates, the flexibility of the metal-plastic composite film decreases, or cracks occur during bending, and there is a situation where the intermediate metal layer and the hot-melt bonding resin layer peel off. If the acid value of the acid-modified polyolefin resin is less than 0.5 mgKOH / g, the number of curing reaction points with the curing agent is small, and the adhesion between the intermediate metal layer and the hot-melt bonding resin layer is unstable. If the acid value exceeds 200 mgKOH / g, the curing reaction between the curing agent and the acid-modified polyolefin resin is too intense, a hard resin layer is formed, the flexural resistance deteriorates, the flexibility of the metal-plastic composite film decreases, or cracks occur during bending, and there is a situation where the intermediate metal layer and the hot-melt bonding resin layer peel off.

[0134] The inner adhesive layer used for the intermediate metal layer and the heat-fusible resin layer is a heat-meltable inner adhesive, and the resin used for the heat-meltable inner adhesive layer is an acid-modified polyolefin resin with a melting point of 135 to 165 °C and an MFR (230 °C) of 3 to 15 g / 10 min. The thickness of the formed inner adhesive layer is 2 to 80 μm, preferably 5 to 50 μm. The degree of modification of the acid-modified polyolefin resin used for the heat-meltable inner adhesive is 1% to 15%, preferably 3% to 12%. When the melting point of the acid-modified polyolefin resin is below 135 °C, heating will cause the resin fluidity to increase. During pressure heat sealing, the thickness will decrease significantly, and the adhesion strength between the intermediate metal layer and the heat-fusible resin layer will become low, resulting in sealing problems. When the melting point is above 165 °C, the fluidity is relatively low during pressure heat sealing, and the heat resistance is improved. However, when compounding with the intermediate metal layer, the heat shrinkage amount increases, resulting in an increase in internal stress and a decrease in the adhesion ability between the heat-meltable inner adhesive and the intermediate metal layer. Therefore, during long-term storage, it is possible to peel off from the intermediate metal layer. In addition, due to the heating during heat sealing, further heat shrinkage will occur, the adhesion force with the intermediate metal layer will decrease, and the sealing strength will become low, making the sealing a major problem. If the MFR (230 °C) of the acid-modified polyolefin resin is less than 3 g / 10 min, when extruded onto the intermediate metal layer after heat melting for compounding, the film-forming property during extrusion is likely to be unstable. If the MFR (230 °C) of the acid-modified polyolefin resin is higher than 15 g / 10 min, heating will cause the resin fluidity to increase. During pressure heat sealing, the thickness will decrease significantly, and the adhesion strength between the intermediate metal layer and the heat-fusible resin layer will become low, resulting in sealing problems. When the thickness of the heat-meltable inner adhesive layer is less than 2 μm, during compounding with the intermediate metal layer, due to excessive heat shrinkage, the heat shrinkage cannot be absorbed. Therefore, due to the increase in internal stress, the bonding force with the intermediate metal layer decreases. During long-term storage, it is possible to peel off from the intermediate metal layer. When the thickness of the heat-meltable inner adhesive layer exceeds 80 μm, there will be no physical property problems, but it will lead to an increase in production cost. Therefore, it is best to avoid using it. When the degree of modification of the heat-meltable inner adhesive layer is less than 1%, the adhesion with the intermediate metal layer will be unstable. If the degree of modification exceeds 15%, although there will be no physical property problems, it will lead to an increase in production cost. Therefore, it is best to avoid this phenomenon.

[0135] The characteristics of the heat-fusible resin layer 4 of the outer packaging material are as follows:

[0136] In the outer packaging material for a lithium-ion battery of the present invention, the heat-fusible resin layer is equivalent to the innermost layer and is a layer (heat-sealing layer) that functions to heat-seal the heat-fusible resin layers with each other to seal the battery components during battery assembly.

[0137] For the resin constituting the heat-sealable resin layer, heat-sealability is the main requirement, and there are no particular restrictions. Resins containing a polyolefin main chain such as polyolefins and acid-modified polyolefins are preferred.

[0138] Specific examples of polyolefins include polyethylene vinyl-α-olefin copolymers such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and terpolymers of ethylene-butene-propylene. Among them, polypropylene is preferred. The polyolefin resin as a copolymer can be a block copolymer or a random copolymer. These polyolefin-based resins can be used alone or in combination of two or more.

[0139] Acid-modified polyolefins are polymers modified by block polymerization or graft polymerization of an acid component with a polyolefin. As the acid-modified polyolefin, copolymers formed by copolymerizing polar molecules such as the above-mentioned polyacrylic acid or methacrylic acid with the above-mentioned polyolefin can also be used. In addition, as the acid component used in the acid modification, carboxylic acids or sulfonic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride, and their acid anhydrides can be used, and acrylic acid or maleic acid and their acid anhydrides are preferably used.

[0140] The heat-sealable resin layer can be composed of a single resin or a combination of two or more resins. And the heat-sealable resin layer can have only one layer or be composed of two or more layers of the same or different resins.

[0141] The heat-sealable resin layer can also contain a slip agent as needed. When the heat-sealable resin layer contains a slip agent, the formability of the outer packaging material for lithium-ion batteries can be improved. The type of the slip agent is not particularly limited and can be selected and used within a known range. The slip agent can be used alone or in combination of two or more.

[0142] There are no particular restrictions on the slip agent, and an amide-based slip agent is preferably used. The slip agent can be used alone or in combination of two or more. As the amide-based slip agent, it is preferably used on the surface of the above-mentioned outer substrate resin layer.

[0143] When there is a slip agent on the surface of the heat-sealable resin layer, its content is not particularly limited, but from the viewpoint of improving the formability of the material for electronic packaging, it is preferably in the range of 10 to 50 mg / m 2 and more preferably in the range of 15 to 40 mg / m 2 .

[0144] The slip agent present on the surface of the hot-melt bonding resin layer may be a slip agent that oozes out from the resin constituting the hot-melt bonding resin layer, or a slip agent coated on the surface of the hot-melt bonding resin layer.

[0145] There is no particular limitation on the thickness of the hot-melt bonding resin layer, as long as it can perform the function of sealing battery components after the hot-melt bonding resin layers are hot-melt bonded to each other. It can be selected to be about 100 μm or less, more preferably about 25 to 80 μm.

[0146] The hot-melt bonding resin layer may also contain components such as antioxidants as needed. The hot-melt bonding resin layer containing an antioxidant can inhibit thermal deterioration during the manufacturing process. The type of antioxidant is not particularly limited and can be selected and used within a known range. The antioxidant can be used alone as one type, or two or more types can be used in combination.

[0147] The hot-melt bonding resin in the present invention is a single layer or composite layer composed of one or a mixture of two or more of acid-modified polyolefin resin, homopolypropylene resin, block copolymerized polypropylene resin, random copolymerized polypropylene resin, and polyethylene resin.

[0148] The resin used for the hot melt bonding resin layer is a single layer or a composite layer composed of one or more mixtures with a melting point of 120 to 162 °C, more preferably 130 to 162 °C, and an MFR (230 °C) of 2 to 15 g / 10 min, more preferably an MFR (230 °C) of 3 to 12 g / 10 min, and the thickness is 20 to 120 μm, more preferably 25 to 80 μm. In addition, when the inner melt bonding resin layer is a composite layer, the thickness of the resin on the reverse side in contact with the intermediate metal layer is 2 μm or more, and the melting point is 130 to 152 °C. When the melting point is below 120 °C, the fluidity during heating is high. When pressure heat sealing is performed, the thickness becomes thinner, and the adhesion to the intermediate metal layer decreases. In addition, when pressure is applied, the resin in the squeezed part inside the battery flows to the non-squeezed edge part. External forces such as the expansion, contraction, and bending process of the battery cause cracks, and the electrolyte will penetrate to the intermediate metal layer through the cracks, resulting in a decrease in the insulation resistance of the hot melt bonding resin layer, leakage, and a shortened battery life. When the melting point exceeds 162 °C, the crystallinity of the resin increases, resulting in a relatively low fluidity during pressure heat sealing and an increase in heat resistance. However, when high-crystalline resin is heat sealed, a hard and brittle resin layer is formed. Therefore, under external forces such as the expansion, contraction, and bending process of the battery, the resin layer is prone to cracking, and long-term stable sealing cannot be obtained. When the MFR (230 °C) of the resin is less than 2 g / 10 min, the fluidity of the resin during pressure heat sealing is low, and it is difficult to obtain stable sealing. When the MFR (230 °C) of the resin exceeds 15 g / 10 min, during pressure heat sealing, the fluidity of the resin is too high, the resin thickness becomes too thin, and stable sealing is also difficult to obtain. In addition, when pressure is applied, the resin in the squeezed part inside the battery flows to the non-squeezed edge part. External forces such as the expansion, contraction, and bending process of the battery cause cracks, and the electrolyte will penetrate to the intermediate metal layer through the cracks, resulting in a decrease in the insulation resistance of the hot melt bonding resin layer, leakage, and a shortened battery life. When the thickness of the hot melt bonding resin layer is less than 20 μm, it is difficult to obtain a uniform hot melt bonding part and even more difficult to obtain stable sealing because the thickness cannot fully cover the deviations in mechanical processing dimensions such as the hot sealing device and the deviations in conditions. In addition, when pressure is applied, the resin in the squeezed part inside the battery flows to the non-squeezed edge part, the thickness of the hot melt bonding resin layer becomes thinner, and external forces such as the expansion, contraction, and bending process of the battery are prone to cause cracks, and the electrolyte will penetrate to the intermediate metal layer through the cracks, resulting in a decrease in the insulation resistance of the hot melt bonding resin layer, leakage, and a shortened battery life. When the thickness of the hot melt bonding resin layer exceeds 120 μm, the water vapor transmission rate will increase, the moisture inside the battery will increase, react with the electrolyte to generate gas, and there is a risk of expansion, rupture, and liquid leakage. The battery life is reduced, and excessive hydrogen fluoride corrodes the anti-corrosion treated metal layer, resulting in a decrease in the adhesion strength between the intermediate metal layer and the hot melt bonding resin layer, and problems such as electrolyte leakage are likely to occur.

[0149] The process of laminating the metal-plastic composite film is as follows:

[0150] 1. Degreasing treatment of the intermediate metal layer: The surface wettability of the intermediate metal layer is 65 dyn / cm, preferably 70 dyn / cm or more, or the titration contact angle of distilled water is 15 degrees or less, preferably 10 degrees or less. If the wettability or surface water contact angle of the intermediate metal layer exceeds the given range, it indicates that there is a possibility that the rolling oil in the manufacturing stage still remains on the metal. Therefore, the interfacial adhesion ability formed between the anti-corrosion layer, the intermediate metal layer and the hot-melt resin layer becomes poor. During long-term storage of the battery, there is a risk of peeling between the intermediate metal layer and the hot-melt resin layer, and battery leakage is likely to occur. As a preventive measure, annealing treatment at 150 °C or higher can be carried out, or degreasing can be carried out by plasma, corona method, or alkali solution. The method of alkali degreasing is to immerse the metal in an alkali solution at 50 to 65 °C. After a certain period of treatment, it is washed twice with deionized water and then dried to obtain the degreased metal.

[0151] 2. Formation of the anti-corrosion layer on the intermediate metal layer: After applying the anti-corrosion liquid on the surface of the intermediate metal layer on the side in contact with the hot-melt resin layer, it is heat-treated at a high temperature for a certain period of time;

[0152] 3. Formation and lamination of the outer adhesive layer: A polyurethane-based adhesive dissolved in an organic solvent is applied between the intermediate metal layer and the outer substrate resin layer, heated at a certain temperature for a certain period of time to volatilize the organic solvent, forming the outer adhesive layer. Further, at a certain temperature and pressure, the outer substrate resin layer, the outer adhesive layer and the intermediate metal layer are laminated, and after being stored at a certain temperature for a certain period of time, the outer adhesive layer undergoes a curing reaction to obtain a composite resin layer composed of the outer substrate resin layer, the outer adhesive layer and the intermediate metal layer. When the outer substrate resin layer and the intermediate metal layer are laminated without using the outer adhesive layer, the intermediate metal layer and the outer substrate resin layer are laminated by heating and pressing. By heat treatment, ultraviolet treatment, or electron beam treatment of the outer substrate resin layer to make it film-forming, a composite resin layer composed of the outer substrate resin layer and the intermediate metal layer can be obtained;

[0153] 4. Lamination of the hot-melt bonding resin layer: The composite film composed of the outer substrate resin layer and the intermediate metal layer can be laminated with the hot-melt bonding resin layer by appropriate selection according to different lamination methods, which are exemplified as follows: a. Dry lamination method: A solution-type inner adhesive composed of a main agent, a curing agent, and an organic solvent is coated on the anti-corrosion surface of the intermediate metal layer of the composite film composed of the outer substrate resin layer and the intermediate metal layer. The solution-type inner adhesive is dried to form an inner adhesive layer, and then thermally laminated with the bonding surface of the hot-melt bonding resin layer under certain temperature and pressure, and then subjected to curing treatment to form a composite product of outer substrate resin layer / intermediate metal layer / inner adhesive layer / hot-melt bonding resin layer. Preferably, the bonding surface of the hot-melt bonding resin layer in contact with the inner adhesive layer is pre-treated by corona treatment. In addition, the curing treatment can be carried out at a temperature not exceeding 60°C of the melting point temperature of the inner adhesive layer; b. Melt extrusion method: The resin of the hot-melt type inner adhesive is formed into a hot-melt type inner adhesive layer with a certain thickness on the anti-corrosion surface of the intermediate metal layer by melt extrusion. In addition, thermal lamination is carried out between the surface of the inner adhesive layer and the bonding surface of the hot-melt bonding resin layer to form a composite product of outer substrate resin layer / intermediate metal layer / inner adhesive layer / hot-melt bonding resin layer. To improve the peel strength between the intermediate metal layer and the hot-melt bonding resin layer, heat treatment can be carried out at a temperature not exceeding 60°C of the melting point temperature of the inner adhesive layer; c. Co-extrusion method: The hot-melt type inner adhesive layer and the hot-melt bonding resin layer are formed into a composite product of outer substrate resin layer / intermediate metal layer / inner adhesive layer / hot-melt bonding resin layer by co-extrusion. After the surface of the intermediate metal layer in contact with the inner adhesive layer is subjected to anti-corrosion treatment, to improve the peel strength between the intermediate metal layer and the hot-melt bonding resin layer, heat treatment can be carried out at a temperature not exceeding 60°C of the melting point temperature of the inner adhesive layer; d. Heat lamination method: The resin main agent with a melting point above 100°C and the curing agent are dissolved in water or an organic solvent to form an aqueous solution-type inner adhesive. It is coated on the anti-corrosion treatment surface of the metal layer of the composite layer composed of the outer substrate resin layer and the intermediate metal layer, and the solution-type inner adhesive is dried to form an inner adhesive layer. Under certain temperature and pressure, thermal lamination is carried out with the bonding surface of the hot-melt bonding resin layer to form a composite product of outer substrate resin layer / intermediate metal layer / inner adhesive layer / hot-melt bonding resin layer. To improve the peel strength between the intermediate metal layer and the hot-melt bonding resin layer, heat treatment can be carried out at a temperature not exceeding 60°C of the melting point temperature of the inner adhesive layer. The hot-melt bonding resin layer can also be formed by extrusion, or a film can be used. When using a film, preferably, the bonding surface of the hot-melt bonding resin layer in contact with the inner adhesive layer is pre-treated by corona treatment;

[0154] The peel strength test between the intermediate metal layer and the hot-melt bonding resin layer of the finished metal-plastic composite film is as follows.

[0155] Initial peel strength test:

[0156] Prepare the finished metal-plastic composite film into a straight strip with a sample size of 100*15 mm. Use a tensile test device to conduct a peel test between the intermediate metal layer and the hot-melt resin layer. Place the peeled hot-melt resin layer film in the upper clamping plate of the telescopic test device and the intermediate metal layer in the lower clamping plate. Then, at a telescopic speed of 50 mm / min, conduct a T-peel with a peel angle of 180° and start measuring the peel strength between the intermediate metal layer and the hot-melt resin layer. The peel strength is read as follows: when the moving distance of the hot-melt resin layer and the intermediate metal layer is 50 mm, select the average value of the peel strength between 10 mm and 40 mm of the moving distance. Conduct parallel tests in groups of 5.

[0157] Anhydrous electrolyte resistance test of the finished metal-plastic composite film:

[0158] Directly immerse the sample strip of the finished metal-plastic composite film in a mixed solvent of dimethyl carbonate (DMC): diethyl carbonate (DEC): ethylene carbonate (EC) with a molar ratio of 1:1:1 containing 1 mol / L LiPF 6 . After soaking at 85 °C for 3 days, take it out, wash it with water for 15 min, dry the water on the surface of the sample strip, and measure the peel strength between the intermediate metal layer and the hot-melt resin layer according to the initial peel strength test method of the finished product.

[0159] Hydrous electrolyte resistance test of the finished metal-plastic composite film:

[0160] Cut the metal-plastic composite film into sample strips 15 mm wide and 100 mm long. After peeling 20 mm between the intermediate metal layer and the hot-melt resin layer, immerse it in a solvent of dimethyl carbonate (DMC): diethyl carbonate (DEC): ethylene carbonate (EC) with a ratio of 1:1:1 containing 1 mol / L LiPF 6 . Then add 1000 PPM of water based on the total mass of the electrolyte. After soaking at 85 °C for 3 days, take it out, wash it with water for 15 min, without drying the water. In the state of residual water between the pre-peeled metal layer and the hot-melt resin layer, start measuring the peel strength between the intermediate metal layer and the hot-melt resin layer from the pre-peeled position according to the initial peel strength test method of the finished product.

[0161] Regarding the preparation method of the outer packaging material, there is no special limitation as long as the anti-corrosion layer defined above in this case can be obtained, and known preparation methods of outer packaging materials can be used.

[0162] The following describes the preparation methods of the outer packaging material for high-corrosion-resistant devices and batteries, which is not a limitation to this case.

[0163] 1. Lamination

[0164] The metal-plastic composite film is composed of an outer substrate resin layer / outer adhesive layer A (3μm) / intermediate metal layer / inner adhesive layer B / hot melt resin layer. The thicknesses of the outer substrate resin layer and the intermediate metal layer can be changed according to individual embodiments.

[0165] The lamination method is as follows: The outer substrate resin layer film in contact with the outer adhesive layer A is subjected to corona treatment. Specifically, an amorphous polyester polyol with a weight average molecular weight of 5000, a Tg of 50 °C, and a hydroxyl value of 25 mg KOH / g and an amorphous polyester polyol with a weight average molecular weight of 20000, a Tg of -17 °C, and a hydroxyl value of 8 mg KOH / g are mixed in a weight ratio of 3:2, and toluene diisocyanate (TDI) is added to form an outer bonding liquid with an NCO / OH ratio of 6.2, which is coated on the intermediate metal to form an adhesive layer A (3μm) on the intermediate metal. After the outer adhesive layer A on the intermediate metal and the outer substrate resin layer film are thermally laminated, a curing treatment is carried out at a temperature of 80 °C for 3 days to form the outer substrate resin layer / outer adhesive layer A (3μm) / intermediate metal layer. Anti-corrosion treatments are carried out on both sides of the intermediate metal layer in advance.

[0166] Anti-corrosion treatments are carried out on both sides of the metal layer in advance.

[0167] In Examples 1 to 9 and Comparative Example 1, the anti-corrosion liquid is evenly coated on both sides of the intermediate metal through a coating roller, and then heat-baked at 190 °C for 2 min. The wet film amount of the anti-corrosion layer treatment liquid is 5 g / m2.

[0168] In Comparative Example 2 and Comparative Example 3, the heating condition is set to 100 °C for 2 minutes. The wet film amount of the anti-corrosion layer treatment liquid is 5 g / m 2 .

[0169] Finally, in one method, the semi-finished product: the outer substrate resin layer / outer adhesive layer A (3μm) / intermediate metal layer is laminated with an inner adhesive layer B-1 and a hot melt resin layer on the metal surface.

[0170] Melt - type inner adhesive layer B - 1 composite method: The melt - type resin used in the inner adhesive layer is maleic anhydride - modified polypropylene without water. On the corrosion - resistant treatment surface of the intermediate metal layer in contact with the hot - melt bonding resin layer, a bonding layer with a thickness of 15 μm is formed. Further, it is compounded with a hot - melt bonding resin with a thickness of 30 μm. The inner adhesive layer and the hot - melt bonding resin layer are compounded onto the corrosion - resistant treatment surface of the intermediate metal layer in contact with the hot - melt bonding resin layer by means of melt co - extrusion. The inner adhesive layer used is 60% (by weight) of maleic anhydride - modified random copolymer polypropylene with a melting point of 140 °C and MFR (230 °C) of 5 g / 10 min. The modification degree of maleic anhydride to random copolymer polypropylene is 10%. It is composed of 24% (by weight) of a copolymer elastomer of propylene and butene with a melting point of 160 °C, MFR (230 °C) of 2.6 g / 10 min, and a density of 0.87 g / cm 3 8% (by weight) of an ethylene - propylene crystalline copolymer elastomer with a melting point of 130 °C, MFR (230 °C) of 9.5 g / 10 min, and a density of 0.91 g / cm 3 and 8% (by weight) of a low - density polyethylene with a melting point of 105 °C and MFR (230 °C) of 12 g / 10 min.

[0171] The hot - melt bonding resin layer consists of two layers, and its structure is:

[0172] The resin layer in contact with the inner adhesive layer: A mixture layer formed by 62% (by weight) of random copolymer polypropylene with a melting point of 155 °C and MFR (230 °C) of 4 g / 10 min, 33% of non - crystalline propylene - based elastomer, and 5% of low - density polyethylene with a melting point of 110 °C and MFR (230 °C) of 7.5 g / 10 min;

[0173] The innermost resin layer: A layer composed of random copolymer polypropylene with a melting point of 155 °C and MFR (230 °C) of 15 g / 10 min;

[0174] The thickness ratio of the resin layer in contact with the inner adhesive layer to the innermost resin layer is 8:2.

[0175] After the intermediate metal layer is compounded with the inner adhesive layer and the hot - melt bonding resin layer, heat treatment is carried out at a temperature of 180 °C for 2 seconds. In this way, a composite product of outer substrate resin layer / outer adhesive layer A (3 μm) / intermediate metal layer / inner adhesive layer B - 1 (15 μm) / hot - melt bonding resin layer (30 μm) is formed.

[0176] Another method is to compound the inner adhesive layer B - 2 and the hot - melt bonding resin layer on the metal surface of the semi - finished product: outer substrate resin layer / outer adhesive layer A (3 μm) / intermediate metal layer.

[0177] Solution - type inner adhesive layer B - 2 compounding method: An anhydrous maleic anhydride - modified polypropylene solution with a weight - average molecular weight of 80,000, a melting point of 80 °C, and an acid value of 2 mgKOH / g and an aromatic isocyanate (HDI - based, hexamethylene diisocyanate) solution are formed into a solution - type mixture at a solid ratio of 20:1 and coated onto the corrosion - protected intermediate metal surface in contact with the hot - melt resin layer of a composite film with a composite outer substrate resin layer. After drying, a bonding layer B with a thickness of 4 μm is formed. Then, at a temperature of 80 °C, it is thermally compounded with the bonding surface of a 25 - μm hot - melt resin, and then cured at a temperature of 60 °C for 7 days, forming a composite product of outer substrate resin layer / outer adhesive layer A (3 μm) / intermediate metal layer / inner adhesive layer B - 2 / hot - melt resin layer (25 μm). The bonding surface of the three - layer hot - melt resin layer in contact with the inner adhesive layer B has been pre - corona - treated.

[0178] The three - layer structure of the hot - melt resin is as follows:

[0179] The resin layer in contact with the inner adhesive layer: A layer composed of random copolymer polypropylene with a melting point of 145 °C and an MFR (230 °C) of 7.5 g / 10 min;

[0180] The intermediate resin layer: A mixture layer formed by, by weight, 40% of block copolymer polypropylene with a melting point of 162 °C and an MFR (230 °C) of 2 g / 10 min, 40% of block copolymer polypropylene with a melting point of 160 °C and an MFR (230 °C) of 5 g / 10 min, and 20% of a crystalline polymer elastomer composed of ethylene - propylene with a melting point of 130 °C, an MFR (230 °C) of 9.5 g / 10 min, and a density of 0.91 g / cm3;

[0181] The innermost resin layer: A layer composed of random copolymer polypropylene with a melting point of 145 °C and an MFR (230 °C) of 7.5 g / 10 min;

[0182] The thickness ratio of the three - layer resins in the hot - melt resin layer from the layer in contact with the inner adhesive layer to the innermost layer is 1:8:1.

[0183] 2. The peel strength test between the intermediate metal layer and the hot - melt resin layer of the metal - plastic composite film product is as follows.

[0184] (1) Initial peel strength test

[0185] Prepare the finished metal-plastic composite film into a straight strip with a sample size of 100*15 mm. Use a tensile test device to conduct a peel test between the middle metal layer and the hot melt bonding resin layer. Place the peeled hot melt bonding resin layer film in the upper clamping plate of the telescopic test device, and place the middle metal layer in the lower clamping plate. Then, at a telescopic speed of 50 mm / min, conduct a T-shaped peel with a peel angle of 180°, and start measuring the peel strength between the middle metal layer and the hot melt bonding resin layer. The peel strength is read as follows: when the moving distance of the hot melt bonding resin layer and the middle metal layer is 50 mm, select the average value of the peel strength between 10 mm and 40 mm of the moving distance. Conduct parallel tests in groups of 5.

[0186] (2) Anhydrous electrolyte resistance test of the finished metal-plastic composite film (the results are shown in the anhydrous electrolyte resistance test in Table 1)

[0187] Directly immerse the sample strip of the finished metal-plastic composite film in a mixed solvent of dimethyl carbonate (DMC): diethyl carbonate (DEC): ethylene carbonate (EC) with a molar ratio of 1:1:1 containing 1 mol / L LiPF 6 . After soaking at a temperature of 85°C for 7 days, take it out, wash it with water for 15 min, dry the moisture on the surface of the sample strip, and measure the peel strength between the middle metal layer and the hot melt bonding resin layer according to the method of the initial peel strength test.

[0188] (3) Hydrous electrolyte resistance test of the finished metal-plastic composite film (the results are shown in the anhydrous electrolyte resistance test in Table 1)

[0189] After peeling 20 mm of the metal / hot melt bonding resin composite layer of the sample strip of the finished metal-plastic composite film, immerse it in a mixed solution of dimethyl carbonate (DMC): diethyl carbonate (DEC): ethylene carbonate (EC) with a molar ratio of 1:1:1 containing 1 mol / L LiPF 6 . Then add 1000 PPM water based on the total mass of the electrolyte to the mixed solvent. After soaking at a temperature of 85°C for 7 days, take it out, wash it with water for 15 min, do not dry the moisture, and measure the peel strength between the middle metal layer and the hot melt bonding resin layer according to the method of the initial peel strength test. This test method is to peel under the state of residual moisture between the metal layer and the hot melt bonding resin layer, and measure the peel strength between the middle metal layer and the hot melt bonding resin layer from the pre-peeled part.

[0190] 3. Measurement method

[0191] (1) Water contact angle measurement

[0192] The water contact angle of the metal surface was measured using a German KRUSS DSA25 contact angle measuring instrument. The metal was placed flat on the instrument workbench, and the water output per injection of the syringe was controlled at 2 μl, with a liquid addition speed of 2.67 μL / s. The contact angle value when the water droplet just dropped onto the metal surface was recorded;

[0193] (2) Dyn value measurement

[0194] Use a German Arcotest dyn pen to continuously draw 2 straight lines with a length of 10 cm on the metal surface. If the straight line shrinks by more than 10% within 3 seconds, it indicates that the dyn value of the metal surface does not reach the dyn value of the dyn pen at this time. Select a dyn pen with a lower dyn value for re-measurement;

[0195] (3) Determination of anti-corrosion layer elements

[0196] Use XPS (produced by Shimadzu, Japan, AXIS supra) to measure the element distribution on the surface, at a depth of 20 nm and 40 nm of the anti-corrosion layer on the metal surface by the ESCA method. The metal surface of the sample was sputtered with Ar ions. The ion beam diameter was 800 μm, the voltage was 15 KV, the ion beam sputtering depth was 5 nm, the sputtering rate was 3 nm / min, the number of sputtering times was 7 times, the signal source detection depth was 5 nm, the detection limit was 1‰, and the number of detection times was 8 times.

[0197] Method for making liquid-resistant treatment sample: Cut the metal with an anti-corrosion layer formed into strips with a width of 20 mm and a length of 100 mm, and immerse the strips in a solvent of dimethyl carbonate (DMC): diethyl carbonate (DEC): ethylene carbonate (EC) at a ratio of 1:1:1 containing 1 mol / L LiPF 6 Add 1000 PPM water based on the total mass of the electrolyte, soak at 85 °C for 5 days, take out, wash with water for 15 min, and dry the moisture.

[0198] Example 1

[0199] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The dyn value is 68 dyn / cm. Both sides of the metal have been subjected to anti-corrosion treatment. The proportion of each element in each layer of the anti-corrosion layer on both sides of the metal is as shown in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, polyvinyl alcohol resin, and zirconium fluoride on the surface of the intermediate metal is 15:1:3:2, and the chromium (Cr) content on the metal surface is coated at 15 mg / m 2 .

[0200] The inner adhesive layer is compounded with the hot melt resin layer in the B-1 manner.

[0201] Example 2

[0202] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The water contact angle is 10°. Both sides of the metal are subjected to anti-corrosion treatment. The proportion of each element in each anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium nitrate, phosphoric acid, and acrylic resin on the surface of the intermediate metal is 3:3:1, and the chromium (Cr) content coated on the metal surface is 12 mg / m 2 .

[0203] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-1 manner.

[0204] Example 3

[0205] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The dyne value is 75 dyn / cm. Both sides of the metal are subjected to anti-corrosion treatment. The proportion of each element in each anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium nitrate, phosphoric acid, and acrylic resin on the surface of the intermediate metal is 3:3:1, and the chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0206] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0207] Example 4

[0208] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The water contact angle is 15°. Both sides of the metal are subjected to anti-corrosion treatment. The proportion of each element in each anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, polyvinyl alcohol resin, and zirconium fluoride on the surface of the intermediate metal is 15:1:3:2, and the chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0209] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-1 manner.

[0210] Example 5

[0211] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 12 μm. The water contact angle is 20°. Both sides of the metal are subjected to anti-corrosion treatment. The proportion of each element in each anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, polyvinyl alcohol resin, and zirconium fluoride on the surface of the intermediate metal is 15:1:3:2, and the chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0212] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0213] Example 6

[0214] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 17 μm. The water contact angle is 20°. Both sides of the metal are corrosion-proof treated. The proportion of each element in each layer of the corrosion-proof layer on both sides of the metal is as described in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, polyvinyl alcohol resin, and zirconium fluoride on the surface of the intermediate metal is 15:1:3:2. The chromium (Cr) content coated on the metal surface is 20 mg / m 2 .

[0215] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0216] Example 7

[0217] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The water contact angle is 15°. Both sides of the metal are corrosion-proof treated. The content of the bridging agent in the used corrosion-proof liquid is 0.06%. The proportion of each element in each layer of the corrosion-proof layer on both sides of the metal is as described in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, polyvinyl alcohol resin, and zirconium fluoride on the surface of the intermediate metal is 15:1:3:2. The chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0218] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0219] Example 8

[0220] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 2 μm. The water contact angle is 15°. Both sides of the metal are corrosion-proof treated. The content of the bridging agent in the used corrosion-proof liquid is 8.3%. The proportion of each element in each layer of the corrosion-proof layer on both sides of the metal is as described in Table 1. The content ratio of chromium nitrate, phosphoric acid, and acrylic resin on the surface of the intermediate metal is 2:2:1. The chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0221] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0222] Example 9

[0223] The thickness of the intermediate metal layer is 50 μm, and the thickness of the nickel plating layer is 5 μm. The water contact angle is 15°. Both sides of the metal are corrosion-proof treated. The content of the bridging agent in the used corrosion-proof liquid is 14.93%. The proportion of each element in each layer of the corrosion-proof layer on both sides of the metal is as described in Table 1. The content ratio of chromium nitrate, phosphoric acid, and acrylic resin on the surface of the intermediate metal is 2:2:1. The chromium (Cr) content coated on the metal surface is 15 mg / m 2 .

[0224] The inner adhesive layer is compounded with the hot melt bonding resin layer in the B-2 manner.

[0225] Comparative Example 1

[0226] The thickness of the intermediate metal used was 50 μm, and the thickness of the nickel plating layer was 2 μm. The water contact angle was 15°. Both sides of the metal were subjected to anti-corrosion treatment. The elemental composition of each layer in the anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, and polyvinyl alcohol resin on the metal surface was 2:1:5. The chromium (Cr) content on the metal surface was 5 mg / m 2 .

[0227] The inner adhesive layer was laminated with the heat-sealing resin layer in the manner of B-1.

[0228] In Examples 1 to 9, the initial peel strength of the metal-plastic composite film was above 10.0 N / 15 mm, and the peel strength retention rates after being placed in the electrolyte environment with and without water for 7 days reached 50% and 40% or more, respectively. However, the content of trivalent chromium compounds in the anti-corrosion liquid used in this comparative example was relatively low.

[0229] The carbon (C) content on the surface was 67%, and the elemental content from the intermediate metal layer was 5.5%. At a depth of 40 nm from the surface of the anti-corrosion layer towards the inside, the carbon (C) content was 0.1%, the elemental content from the intermediate metal layer was 25% (relatively low), and the fluorine (F) content was 6.7%. Moreover, after being immersed in the electrolyte for 5 days, the fluorine (F) content at 40 nm was as high as 27.3%.

[0230] At this time, the initial strength was 13.85 N / 15 mm, and the retention rates of the electrolyte resistance test were 58% under the condition of not adding water and 26% under the condition of adding water, both showing low values compared with the examples.

[0231] Comparative Example 2

[0232] The thickness of the intermediate metal used was 50 μm, and the thickness of the nickel plating layer was 2 μm. The dyne value was 75 dyn / cm. Both sides of the metal were subjected to anti-corrosion treatment. The elemental composition of each layer in the anti-corrosion layer on both sides of the metal is as described in Table 1. The content ratio of chromium nitrate, phosphoric acid, and acrylic resin on the intermediate metal surface was 1:2:1. The chromium (Cr) content on the metal surface was 15 mg / m 2 .

[0233] The inner adhesive layer was laminated with the heat-sealing resin layer in the manner of B-2.

[0234] Comparing with Examples 1 to 9, the heating condition for forming the anti-corrosion layer in this comparative example was 100 °C for 2 minutes.

[0235] The carbon (C) content on the surface is 38%, and the element content from the intermediate metal layer is 5.2%. At a depth of 40 nm from the surface of the anti-corrosion layer towards the inside, the element content of the intermediate metal layer is 22%, which is relatively low. Moreover, after 5 days of electrolyte immersion, at 40 nm, the fluorine (F) content is as high as 28.72%.

[0236] At this time, the initial strength is 14.68 N / 15 mm, and the retention rate of the electrolyte resistance test is: 60% under the condition of not adding water and 32% under the condition of adding water, both showing low values compared with the examples.

[0237] Comparative Example 3

[0238] The thickness of the intermediate metal used is 50 μm, and the thickness of the nickel plating layer is 0.2 μm. The dyne value is 75 dyn / cm. Anti-corrosion treatment is carried out on both sides of the metal. The content of the cross-linking agent in the anti-corrosion liquid used is 25.00%. The element proportion of each layer in the anti-corrosion layer on both sides of the metal is as shown in Table 1. The content ratio of chromium fluoride, hydrofluoric acid, and polyvinyl alcohol resin on the metal surface is 2:1:5. The chromium (Cr) content on the metal surface is coated at 15 mg / m 2 。

[0239] The inner adhesive layer is compounded with the hot-melt resin layer in the manner of B-2.

[0240] Comparing Examples 1 to 9, the heating condition for forming the anti-corrosion layer in this comparative example is 100 °C for 2 minutes.

[0241] The carbon (C) content on the surface is 66%, and the element content from the intermediate metal layer is 12.4%, which is relatively high. The fluorine (F) element content is 11.7%, which is relatively high. At a depth of 40 nm from the surface of the anti-corrosion layer towards the inside, the element content of the intermediate metal layer is 89%, and the fluorine (F) content is 22.4%, which is relatively high.

[0242]

[0243] Moreover, after 5 days of electrolyte immersion, at 40 nm, the fluorine (F) content is 26.9%. At this time, the initial strength is 15.11 N / 15 mm, and the retention rate of the electrolyte resistance test is: 66% under the condition of not adding water and 38% under the condition of adding water, both showing low values compared with the examples.

[0244] Although the initial adhesion is fully exerted, due to the extremely high content of the cross-linking agent in the anti-corrosion liquid, the cross-linking density inside the anti-corrosion layer is too large, the hardness of the anti-corrosion layer is extremely high, and the bending during the liquid resistance treatment operation is likely to cause cracks in the anti-corrosion layer, exacerbating the penetration of the electrolyte and resulting in a low retention rate.

[0245] Compared with the prior art, the positive effects of the present invention are:

[0246] It is first proposed that the intermediate metal layer uses a nickel-plated steel sheet material, and the elements in the surface anti-corrosion layer are distributed in a gradient. By controlling the content of the outermost carbon (C) in the anti-corrosion layer, the content of the intermediate metal element and fluorine (F) at the inner layer (40 nm), the initial peel strength between the intermediate metal layer and the hot melt resin layer of the metal-plastic composite film can be improved, as well as the corrosion resistance in an electrolyte environment with a large amount of added water. Therefore, the present invention has excellent corrosion resistance and extremely high industrial utilization value.

[0247] The above content related to well-known common knowledge will not be described in detail, and those skilled in the art can understand it.

[0248] The above are only some specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An outer packaging material for a lithium-ion battery device resistant to electrolyte corrosion, characterized in that: It includes an intermediate metal layer and an anti-corrosion layer formed by the intermediate metal layer undergoing corrosion resistance treatment; The anti-corrosion layer is formed by applying an anti-corrosion liquid and then heat treating at 130 to 200° C. The anti-corrosion liquid mainly comprises a trivalent chromium compound, an inorganic acid, an organic resin, a bridging agent, and a solvent consisting of water or an organic solvent, or a mixture thereof; The trivalent chromium compound is at least one of chromium nitrate and chromium fluoride, the inorganic acid is at least one of phosphoric acid, nitric acid and hydrofluoric acid, the organic resin is at least one of acrylic resin, methacrylic resin, polyvinyl alcohol resin, olefin resin and phenolic resin, the bridging agent contains at least one of amino resin, phenolic resin, epoxy compound, blocked isocyanate compound, oxazoline compound, carbodiimide compound, formaldehyde and condensation product of alkyl monoalcohol with carbon number of 1 to 4, and the organic solvent is at least one of isopropanol, ethanol and ethylene glycol butyl ether; Wherein, the outer packaging material further comprises an inner adhesive layer and a hot-melt resin layer, the intermediate metal layer is arranged on the inner adhesive layer, the inner adhesive layer is arranged on the hot-melt resin layer, and the anti-corrosion layer is arranged between the intermediate metal layer and the inner adhesive layer; Wherein, the carbon (C) element component, the nickel (Ni) element component and the fluorine (F) element component on the anti-corrosion layer on the side of the heat-welding resin layer are distributed in a gradient manner; Among them, the carbon (C) content ratio of the outermost layer of the anti-corrosion layer on the side of the hot-melt resin layer is greater than or equal to 40% and less than or equal to 100%, the nickel (Ni) content ratio is less than or equal to 10%, and the fluorine (F) content ratio is less than or equal to 10%; in the 40nm layer below the surface of the anti-corrosion layer, the carbon (C) content ratio is less than or equal to 10%, the nickel (Ni) content ratio is greater than or equal to 30% and less than or equal to 100%, and the fluorine (F) content ratio is less than or equal to 20%.

2. The outer packaging material according to claim 1, characterized in that: It further comprises an outer base resin layer; the outer base resin layer is arranged on the intermediate metal layer.

3. The outer packaging material according to claim 2, characterized in that: It further comprises an outer adhesive layer, the outer base resin layer is arranged on the outer adhesive layer, and the outer adhesive layer is arranged on the intermediate metal layer; wherein the intermediate metal layer is arranged between the outer adhesive layer and the inner adhesive layer.

4. The outer packaging material according to claim 1, characterized in that: The intermediate metal layer is a nickel-plated steel plate, and the thickness of the nickel-plated layer of the nickel-plated steel plate is 0.5 μm to 20 μm.

5. The outer packaging material according to claim 1, characterized in that: The anti-corrosion liquid contains titanium (Ti) compound or zirconium (Zr) compound, and the contents thereof are 0 to 0.6% and 0 to 2.8% respectively.

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