Modified current collector base film, preparation method therefor, and use thereof

Abstract

A modified current collector base film, a preparation method therefor, and a use thereof. The modified current collector base film comprises a polymer film and a modified polyurea coating provided on the surface of at least one side of the polymer film. The polymer film is modified using the modified polyurea coating, thereby improving the polarity of the polymer film, enabling the polymer film to be in closer contact with a conductive layer, and increasing adhesion. In addition, the modified polyurea coating has excellent stiffness, strength, and high strain rate sensitivity, thereby enabling the polymer film to have improved mechanical properties. Moreover, the modified polyurea coating helps the polymer film resist erosion by electrolytes and high-temperature environments. In summary, the provided modified current collector base film has excellent mechanical properties, thermal stability, and adhesion, is not easily damaged during the subsequent preparation process of composite current collectors, and can facilitate the promotion and use of composite current collectors. Batteries prepared on this basis have excellent physical and chemical properties and safety performance.

Description

Modified current collector base film and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, for example, a modified current collector base film and preparation method and application thereof. BACKGROUND

[0002] At present, the composite current collector based on the high polymer film has been widely concerned and applied in the new energy industry. The preparation of the composite current collector usually adopts the method of physical vapor deposition (PVD) to deposit a layer of metal on the high polymer film (such as polyester, polyolefin, etc.), so as to prepare a composite current collector with good conductivity. Compared with the traditional current collector, the composite current collector based on the high polymer film has the characteristics of low cost, light weight, good internal insulation, etc. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when applied in the battery.

[0003] However, the high polymer film will suffer certain damage in the preparation process of the current collector, especially at high temperature. Due to the instability of the high polymer layer, it is more prone to low performance or defects when suffering from stress or chemical reagents, thereby affecting the physical and chemical properties of the composite current collector.

[0004] Therefore, it is necessary to develop a high polymer film with excellent mechanical properties, so as to further improve the performance of the composite current collector prepared therefrom and enhance the physical and chemical properties and safety performance of the battery. SUMMARY

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] The present application provides a modified current collector base film and preparation method and application thereof. The present application modifies the polymer film by using a modified polyurea coating layer, which can improve the polarity of the polymer film, make the contact between the polymer film and the conductive layer more closely, increase the adhesion, and the modified polyurea coating layer has high strain rate sensitivity and excellent mechanical properties; secondly, since the modified polyurea coating layer has good corrosion resistance, barrier property, high thermal decomposition temperature and excellent thermal stability, it is helpful for the polymer film to resist the corrosion of the electrolyte and the high temperature environment. In summary, the modified current collector base film provided by the present application has excellent mechanical properties, thermal stability and adhesion, and is not easy to be damaged in the subsequent preparation process of the composite current collector, which can promote the popularization and application of the composite current collector, and the battery prepared therefrom has excellent physical and chemical properties and safety performance.

[0007] In a first aspect, the present application provides a modified current collector base film, which comprises a polymer film and a modified polyurea coating layer arranged on at least one side surface of the polymer film.

[0008] Due to the thermodynamic incompatibility between soft and hard segments and the hydrogen bonding between hard segments, the polyurea structure presents a unique morphology of microphase separation, which exhibits excellent comprehensive mechanical properties on the macroscopic level: under static and quasi-static loading, the polyurea exhibits super-elastic material characteristics and has excellent mechanical properties; under dynamic loading, the mechanical behavior of the polyurea becomes complex, showing high strain rate sensitivity and nonlinear stress-strain relationship, and with the continuous increase of the strain rate, the polyurea changes from a soft rubber state to a hard plastic state, and in this process, it absorbs and dissipates energy through deformation.

[0009] Therefore, the modified polyurea coating is used for the polymer film in the application, which can improve the polarity of the polymer film, make the contact with the conductive layer more closely, increase the adhesion, and the modified polyurea coating has high strain rate sensitivity and excellent mechanical properties, especially the elongation is significantly improved; secondly, due to the good corrosion resistance, barrier property, high thermal decomposition temperature and excellent thermal stability of the modified polyurea coating, when it is subjected to local heat and sudden mechanical impact, the polyurea will change into a glass state and absorb part of the energy, so it helps the polymer film to resist the corrosion of electrolyte and high temperature environment. In summary, the modified current collector base film provided by the application has excellent mechanical properties, thermal stability and adhesion, and is not easy to be damaged in the subsequent preparation process of the composite current collector, which can promote the popularization and application of the composite current collector, and the battery prepared based on this has excellent physicochemical properties and safety performance.

[0010] As an optional technical solution of the application, the preparation method of the modified polyurea coating comprises the following steps:

[0011] (a) mixing isocyanate, polyether polyol and active agent, and obtaining component A after reaction, wherein the component A comprises a pre-polymer containing -NCO;

[0012] (b) mixing amino-terminated polyether, amine chain extender, functional filler and auxiliary agent to obtain component B;

[0013] (c) mixing the component A and the component B, and then spraying on the polymer film to form a modified polyurea coating.

[0014] As an optional technical solution of the application, the single-sided thickness of the modified polyurea coating is 50-500 nm, for example, it can be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm or 500 nm, etc., and optionally 50-200 nm.

[0015] In the application, if the single-sided thickness of the modified polyurea coating is too thin, the effect is not obvious; if the single-sided thickness of the modified polyurea coating is too thick, it is easy to cause uneven thickness and hinder the electrochemical performance.

[0016] In one embodiment, the material of the polymer film comprises any one of or a combination of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), or polyimide (PI).

[0017] In one embodiment, the thickness of the polymer film is 1-10 μm, for example, 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, or 10 μm, etc.

[0018] In the present application, the thickness of the polymer film can be 1-10 μm, taking into account the application requirements of the composite current collector, and considering the difficulty and cost of the preparation process.

[0019] In a second aspect, the present application provides a preparation method of the modified current collector base film according to the first aspect, which comprises the following steps:

[0020] The modified polyurea material is coated on at least one side surface of the polymer film to obtain the modified current collector base film.

[0021] As an optional technical solution of the present application, the coating method comprises any one of or a combination of spray coating, brush coating, or roll coating.

[0022] As an optional technical solution of the present application, the preparation method of the modified polyurea material comprises the following steps:

[0023] (a) mixing isocyanate, polyether polyol, and active agent, and obtaining component A after reaction, wherein the component A comprises a pre-polymer containing -NCO;

[0024] (b) mixing amino-terminated polyether, amine chain extender, functional filler, and auxiliary agent to obtain component B;

[0025] (c) mixing the component A and the component B to obtain the modified polyurea material.

[0026] In the present application, the amine chain extender composed of long carbon chain diamine and alicyclic diamine in a certain mass ratio is used to replace the aromatic chain extender, which can effectively improve the mechanical properties of the polyurea material. Therefore, with the increase of the rigidity and strength of the modified polyurea material, the failure strain is reduced, the modified polyurea material has high strain rate sensitivity, and at the same time, it can exhibit glass state under high strain rate, etc., and can absorb energy under high strain rate, thus having better mechanical properties, so as to avoid defects in the preparation process of the current collector.

[0027] As an optional technical solution of the present application, the isocyanate in step (a) includes any one or a combination of at least two of 2,4-dimethyl decane diisocyanate, 2,2-dimethyl decane diisocyanate, 2,2,4-trimethyl decane diisocyanate or 2,4,6-trimethyl decane diisocyanate monomer.

[0028] In an embodiment, the polyether polyol in step (a) includes any one or a combination of at least two of propylene glycol polyether, butanediol polyether, hexanediol polyether, polyoxypropylene glycol, polyoxypropylene triol or polytetrahydrofuran ether glycol.

[0029] In an embodiment, the active agent in step (a) includes any one or a combination of at least two of polyether carbonate, allyl glycidyl ether or alkylene carbonate.

[0030] In an embodiment, the mass ratio of the isocyanate, polyether polyol and active agent in step (a) is (40-55):(44-55):(1-5), wherein the selected range "40-55" of the isocyanate may be 40, 45, 50 or 55, etc., the selected range "44-55" of the polyether polyol may be 44, 50 or 55, etc., and the selected range "1-5" of the active agent may be 1, 2, 3, 4 or 5, etc.

[0031] As an optional technical solution of the present application, the terminal amino polyether in step (b) is an amino-terminated polyalkylene oxide compound.

[0032] In an embodiment, the amino-terminated polyalkylene oxide compound includes any one or a combination of at least two of D-230 (CAS No.: 9046-10-0), D-2000 (CAS: 9046-10-0), T-403 (CAS: 39423-51-3), T-5000 (CAS: 64852-22-8), ZD-1200 (CAS: 100-1000-11), ZD-140 (CAS: 9040-10-0), ZD-123 (CAS: 9046-10-0), ZT-143 (CAS: 39423-51-3) or ZT-1500 (CAS: 64852-22-8).

[0033] In an embodiment, the amine chain extender in step (b) includes long carbon chain diamine and alicyclic diamine.

[0034] In one embodiment, the long carbon chain diamine is a linear diamine having a carbon atom number of 10 or more, such as 10, 11, 12, 13, 14, 15, 18, 20, 22, 25, 28, 30, 33, 35, 38, or 40, or a linear diamine having a carbon atom number in the range of C12-C30.

[0035] In one embodiment, the long carbon chain diamine includes any one of decanediamine, undecanediamine, dodecanediamine, tridecanediamine, or tetradecanediamine, or a combination of at least two thereof.

[0036] In one embodiment, the alicyclic diamine includes an alicyclic diamine having a molecular weight of less than 300.

[0037] In the present application, using an alicyclic diamine having a molecular weight of less than 300 instead of a small amount of aromatic chain extender can effectively improve the mechanical properties of the polyurea material.

[0038] In one embodiment, the alicyclic diamine having a molecular weight of less than 300 includes any one of 3,3 dimethyl-4,4-dicyclohexylmethane diamine, isophorone diamine, or 4,4'-diaminodicyclohexylmethane, or a combination of at least two thereof.

[0039] In one embodiment, the mass ratio of the long carbon chain diamine to the alicyclic diamine is 1:(0.2-2.5), such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:2, 1:4, 1:6, 1:8, 1:2, or 1:2.5, or the like.

[0040] In the present application, if the mass ratio of the long carbon chain diamine to the alicyclic diamine is too small or too large, the improvement in the mechanical properties of the polyurea material will not reach the best effect.

[0041] In one embodiment, the functional filler in step (b) includes any one of a flame retardant, a hydrophilic compound, a plasticizer, an adhesion enhancer, or an adhesive, or a combination of at least two thereof.

[0042] In the present application, using a flame retardant for modification can improve the thermal decomposition temperature of the polyurea coating, and obtain excellent thermal stability, and when attacked by external fire, can effectively prevent, delay, or terminate the spread of fire; using a hydrophilic compound for modification can improve the polarity of the polymer film, and make it hydrophilic, thereby contacting the conductive layer more closely and increasing the adhesion; using a plasticizer, an adhesion enhancer, or an adhesive for modification can improve the mechanical properties, and make the combination between different compounds more closely.

[0043] In one embodiment, the flame retardant includes any one or a combination of at least two of polyvinylsilsesquioxane, aluminum hypophosphite, or graphite.

[0044] In one embodiment, the hydrophilic group in the hydrophilic compound includes any one or a combination of at least two of carboxyl, sulfonic acid, amino, amine, hydroxyl, amide, or ether bond. Exemplarily, it can be a combination of, for example, aminated polypropylene PP-g-NH2 and 2,2-dimethylol propionic acid, etc.

[0045] In one embodiment, the plasticizer includes any one or a combination of at least two of dioctyl phthalate, isooctyl epoxy octadecanoate, dimethyl maleate, diisooctyl adipate, tricresyl phosphate, or tris(2-ethyl)hexyl trimellitate.

[0046] In one embodiment, the tackifier includes any one or a combination of at least two of terpene resin, special grade rosin, hydrogenated C5 petroleum resin, or copolymerized petroleum resin.

[0047] In one embodiment, the adhesive includes any one or a combination of at least two of silane coupling agent, acrylic, epoxy resin, chlorinated polypropylene, or aminated polypropylene.

[0048] It should be noted that the type of the auxiliary agent is not limited in the present application, and exemplarily, it can be a compatibilizer, dispersant, or catalyst, etc., wherein the compatibilizer can be, for example, SBS (styrene-butadiene-styrene triblock copolymer), SEBS (linear triblock copolymer with polystyrene as terminal segment, and ethylene-butene copolymer obtained by hydrogenation of polybutadiene as intermediate elastic segment), or SIS (styrene-isoprene-styrene triblock copolymer), etc., the dispersant can be, for example, acetone, methyl ethyl ketone, or toluene, etc., and the catalyst can be, for example, dibutyl tin dilaurate, etc.

[0049] In one embodiment, the mass ratio of the terminal amino polyether, amine chain extender, functional filler, and auxiliary agent in step (b) is (40-60):(20-35):(0-20):(0-5), wherein the selection range “40-60” of the terminal amino polyether can be, for example, 40, 45, 50, 55, or 60, etc., the selection range “20-35” of the amine chain extender can be, for example, 20, 25, 30, or 35, etc., the selection range “0-20” of the functional filler can be, for example, 5, 10, 15, or 20, etc., and the selection range “0-5” of the auxiliary agent can be, for example, 0, 1, 2, 3, 4, or 5, etc.

[0050] In the present application, if the amount of amine chain extender is too small, the chain extension is insufficient, the hard segment content of polyurethane molecules decreases, and the strength, heat resistance, and solvent resistance are reduced, and if the amount of amine chain extender is too much, the prepolymer and the chain extender are agglomerated, and the product is not uniform.

[0051] In the present application, if the amount of functional filler is too much, the performance cannot be further improved and agglomeration occurs.

[0052] As an optional technical solution of the present application, the preparation method comprises the following steps:

[0053] (1) polyether polyol is added to the reaction kettle, dehydrated at 90-120℃ (for example, it can be 90℃, 100℃, 110℃ or 120℃, etc.) under negative pressure (for example, it can be-0.05MPa, etc.) for 0.5-2h (for example, it can be 0.5h, 1h, 1.5h or 2h, etc.), then active agent is added to continue dehydration until the water content of polyether polyol is ≤0.05%, then the temperature is lowered to 40-60℃ (for example, it can be 40℃, 50℃ or 60℃, etc.) and isocyanate is added, then the temperature is raised to 80-90℃ (for example, it can be 80℃, 85℃ or 90℃, etc.), and the temperature is kept constant for 2-3h (for example, it can be 2h, 2.5h or 3h, etc.), to obtain a prepolymer with a mass fraction of-NCO of 13-16% (for example, it can be 13%, 14%, 15% or 16%, etc.), then vacuum dehydration is performed to prepare the A component;

[0054] The mass ratio of isocyanate, polyether polyol and active agent is (40-55):(44-55):(1-5);

[0055] The terminal amino polyether, amine chain extender, functional filler and auxiliary agent are sequentially added and dispersed in a high-speed disperser for 30-60min (for example, it can be 30min, 40min, 50min or 60min, etc.), and then dried at 40-60℃ to obtain the B component;

[0056] The mass ratio of terminal amino polyether, amine chain extender, functional filler and auxiliary agent is (40-60):(20-35):(0-20):(0-5);

[0057] (2) the A component and the B component are mixed in a volume ratio of 1:1 to obtain a modified polyurea material;

[0058] (3) the modified polyurea material is sprayed on at least one side surface of the polymer film to obtain a modified current collector base film.

[0059] In a third aspect, the application provides a composite current collector, comprising the modified current collector base film according to the first aspect or the modified current collector base film prepared by the method according to the second aspect, and an electrically conductive layer arranged on at least one side surface of the modified current collector base film.

[0060] As an optional technical solution of the application, the thickness of the electrically conductive layer is 500-2000 nm, for example, 500 nm, 1000 nm, 1500 nm or 2000 nm, or optionally 800-1200 nm.

[0061] In the application, the electrically conductive layer is too thin and has poor conductivity, and is too thick, and the prepared composite current collector is too thick and heavy, which is not conducive to improving the energy density of the battery. Considering the conductivity and the improvement of the energy density, the optional thickness is 800-1200 nm.

[0062] In an embodiment, the preparation method of the electrically conductive layer comprises any one or a combination of at least two of physical vapor deposition, electroplating or chemical plating.

[0063] In an embodiment, the physical vapor deposition comprises evaporation and / or magnetron sputtering.

[0064] In an embodiment, in the electroplating, the specific parameters for preparing the electrically conductive layer include: the current intensity is 20000-50000 A, for example, 20000 A, 30000 A, 40000 A or 50000 A, the current density is 5000-10000 A / m 2 , for example, 5000 A / m 2 , 6000 A / m 2 , 7000 A / m 2 , 8000 A / m 2 , 9000 A / m 2 or 10000 A / m 2 , the concentration of copper ions is 65-100 g / L, for example, 65 g / L, 75 g / L, 85 g / L, 95 g / L or 100 g / L, and the concentration of hydrogen ions in the electrolyte is 90-110 g / L, for example, 90 g / L, 95 g / L, 100 g / L, 105 g / L or 110 g / L.

[0065] In an embodiment, the specific parameters for preparing the conductive layer in the magnetron sputtering method include: a power of 2-20 KW, for example, 2 KW, 5 KW, 10 KW, 15 KW or 20 KW, etc.; a vacuum degree of the vacuum chamber of ≤0.1 Pa, for example, 0.1 Pa, 0.05 Pa or 0.01 Pa, etc.; a flow rate of the gas source of 20-500 mL / min, for example, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min or 500 mL / min, etc.; and a time for each coating of 0.1-120 s, for example, 0.1 s, 1 s, 10 s, 50 s, 100 s or 120 s, etc.

[0066] In an embodiment, a bonding layer is further arranged between the conductive layer and the modified current collector base film, and the material of the bonding layer includes any one or a combination of at least two of aluminum oxide, silicon oxide, titanium oxide, elemental nickel, elemental chromium, elemental titanium, nickel-chromium alloy, nickel-chromium-copper alloy or silicon-aluminum alloy.

[0067] In an embodiment, the bonding force between the adjacent conductive layer and bonding layer is 100-900 N / m, for example, 100 N / m, 300 N / m, 500 N / m, 700 N / m or 900 N / m, etc.

[0068] In the present application, the bonding force between the bonding layer and the conductive layer affects the relative movement between the conductive layer and the polymer film during the deformation of the composite current collector, thereby affecting the deformation fission behavior of the conductive layer and further affecting the effect of improving the safety performance of the battery.

[0069] In an embodiment, a protective layer is arranged on the side surface of the conductive layer away from the modified current collector base film, and the material of the protective layer includes any one or a combination of at least two of elemental nickel, elemental chromium, nickel-based alloy, copper-based alloy, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper chromate, copper chromite, graphite, carbon black, carbon nanometer quantum dot, carbon nanotube, carbon nanofiber or graphene.

[0070] It should be noted that when the protective layer is arranged on both side surfaces of the polymer film, the materials of the two protective layers can be consistent or inconsistent, and the thicknesses can be consistent or inconsistent.

[0071] In the present application, the protective layer is arranged to prevent the conductive layer from being chemically corroded or physically damaged.

[0072] In an embodiment, the thickness of the protective layer is 10-100 nm, for example, 10 nm, 30 nm, 50 nm, 70 nm or 90 nm, etc., and can be optionally 20-80 nm.

[0073] In one embodiment, the thickness of the protective layer is ≤ 1 / 10 of the thickness of the conductive layer.

[0074] In one embodiment, the method for preparing the protective layer comprises any one or a combination of at least two of physical vapor deposition, chemical vapor deposition, in-situ forming, or coating.

[0075] In a fourth aspect, the application provides a lithium ion battery, wherein the electrode tab of the lithium ion battery comprises the composite current collector as described in the third aspect, or comprises a composite current collector made based on the modified current collector base film as described in the first aspect.

[0076] The numerical ranges recited herein are inclusive of the endpoints and also include any intervening ranges not expressly specified. For the sake of brevity, the numerous details of construction and operation of the application as described herein are not necessarily included in the accompanying figures.

[0077] Compared with the related art, the application has the following beneficial effects:

[0078] The modified polyurea coating layer can improve the polarity of the polymer film, make the contact between the polymer film and the conductive layer more closely, increase the adhesion, and the modified polyurea coating layer has excellent rigidity, strength, high strain rate sensitivity, and excellent mechanical properties, avoiding defects in the preparation process of the current collector. In addition, the modified polyurea coating layer has good corrosion resistance and barrier properties, thus helping the polymer film resist the corrosion of the electrolyte. Finally, the modified polyurea coating layer has high thermal decomposition temperature and excellent thermal stability, and can resist high temperature environment. In summary, the modified current collector base film provided by the application has excellent mechanical properties, thermal stability, and adhesion, and is not easy to be damaged in the subsequent preparation process of the composite current collector, which can promote the popularization and application of the composite current collector, and the battery prepared based on the same has excellent physicochemical properties and safety performance.

[0079] Other aspects can become apparent from the following detailed description. DETAILED DESCRIPTION

[0080] The technical solutions of the application are further illustrated by the specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application, and should not be regarded as specific limitations of the application.

[0081] Example 1

[0082] The embodiment provides a modified current collector base film, which comprises a polymer film and a modified polyurea coating layer arranged on both sides of the polymer film.

[0083] The single-sided thickness of the modified polyurea coating layer is 100 nm.

[0084] The material of the polymer film is PP, and the thickness is 4.5 μm.

[0085] The embodiment also provides a preparation method of the modified current collector base film.

[0086] (1) Propylene glycol polyether PPG2000 is added into a reaction kettle, and is dehydrated at 100°C and -0.05 MPa for 1 h, then alkylene carbonate is added to continue dehydration until the water content of the propylene glycol polyether PPG2000 is less than or equal to 0.05%, then the temperature is lowered to 50°C, 2,4-dimethyl decane diisocyanate is added, then the temperature is raised to 80°C, and the temperature is kept for 2 h to obtain a prepolymer with a mass fraction of -CO of 15%, and then vacuum dehydration is performed to obtain the A component;

[0087] The mass ratio of the 2,4-dimethyl decane diisocyanate, the propylene glycol polyether PPG2000 and the alkylene carbonate is 50:46:4.

[0088] The 55% polyetheramine D-2000, the 20% dodecanediamine, the 5% isophorone diamine, the 15% aluminum hypophosphite, the 1% SBS and the 4% acetone are sequentially added into a high-speed dispersion machine, and are dispersed for 45 min, and then are dried at 60°C to obtain the B component;

[0089] The mass ratio of the polyetheramine D-2000, the amine chain extender (including the dodecanediamine and the isophorone diamine), the aluminum hypophosphite and the auxiliary agent (the SBS and the acetone) is 55:25:15:5.

[0090] (2) The A component and the B component are loaded into a spraying machine, and are sprayed on two side surfaces of the polymer film according to a volume ratio of 1:1 to obtain the modified current collector base film.

[0091] The embodiment also provides a composite current collector, which comprises the modified current collector base film as described above.

[0092] The adhesive layer is arranged on the two side surfaces of the modified current collector base film, and is made of nickel-chromium alloy with a single-side thickness of 5 nm.

[0093] The copper layer is arranged on the surface of the adhesive layer in a direction away from the modified current collector base film, and has a single-side thickness of 900 nm.

[0094] The protective layer is arranged on the surface of the copper layer in a direction away from the modified current collector base film, and is made of chromium oxide with a single-side thickness of 20 nm.

[0095] The embodiment also provides a preparation method of the composite current collector, which comprises the following steps:

[0096] (I) Put the modified current collector base film into a magnetron sputtering machine, and deposit a 5 nm adhesive layer on both sides of the film with a nickel-chromium alloy target as the target material. The specific process conditions are as follows: the nickel-chromium target (purity: 99.99%) is used as the target material, the power is 4.0 KW, the argon flow rate is 50 mL / min, the film plating vacuum degree is 0.08 Pa, the film plating time is 1 s, and the temperature of the main roller during film plating is 10°C;

[0097] (II) Put the composite film prepared above containing the adhesive layer on the surface into a magnetron sputtering machine, and deposit a copper layer with a thickness of 900 nm on both sides of the film. The preparation conditions are as follows: the copper target (purity: 99.99%) is used as the target material, the power is 12.0 KW, the argon flow rate is 70 mL / min, the film plating vacuum degree is 0.1 Pa, the film plating time is 100 s, and the cooling temperature of the main roller during film plating is -5°C;

[0098] (III) Put the composite film prepared above containing the adhesive layer and the copper layer into a 0.5 g / L chromic acid aqueous solution (25°C) for immersion treatment for 20 s. After treatment, clean it through a pure water tank. After cleaning, place it in a 60°C oven for drying, and the composite current collector is prepared.

[0099] Example 2

[0100] The difference between this example and Example 1 is that the amine chain extender is replaced by a combination of 17% dodecanediamine and 8% isophorone diamine.

[0101] The rest of the preparation method and parameters remain the same as in Example 1.

[0102] Example 3

[0103] The difference between this example and Example 1 is that the amine chain extender is replaced by a combination of 15% dodecanediamine and 10% isophorone diamine.

[0104] The rest of the preparation method and parameters remain the same as in Example 1.

[0105] Example 4

[0106] The difference between this example and Example 1 is that the amine chain extender is replaced by a combination of 8% dodecanediamine and 17% isophorone diamine.

[0107] The rest of the preparation method and parameters remain the same as in Example 1.

[0108] Example 5

[0109] The difference between this example and Example 1 is that the amine chain extender is replaced by a combination of 22% dodecanediamine and 3% isophorone diamine.

[0110] The rest of the preparation method and parameters are consistent with Example 1.

[0111] Example 6

[0112] The difference between this example and Example 1 is that the amine chain extender is replaced by a combination of 5% dodecanediamine and 20% isophorone diamine.

[0113] The rest of the preparation method and parameters are consistent with Example 1.

[0114] Example 7

[0115] The difference between this example and Example 3 is that the aluminum hypophosphite is replaced by dimethyl maleate.

[0116] The rest of the preparation method and parameters are consistent with Example 3.

[0117] Example 8

[0118] The difference between this example and Example 3 is that the aluminum hypophosphite is replaced by a combination of 5% silane coupling agent KH-570 and 15% special grade rosin.

[0119] The rest of the preparation method and parameters are consistent with Example 3.

[0120] Example 9

[0121] The difference between this example and Example 3 is that the combination of aluminum hypophosphite and auxiliary agent is replaced by a combination of 3% aminated polypropylene PP-g-NH2, 16% 2,2-dimethylol propionic acid and 1% dibutyl tin dilaurate.

[0122] The rest of the preparation method and parameters are consistent with Example 3.

[0123] Example 10

[0124] The difference between this example and Example 3 is that the amine chain extender in step (1) is replaced by 3,3'-dichloro-4,4'-diaminodiphenyl methane.

[0125] The rest of the preparation method and parameters are consistent with Example 3.

[0126] Example 11

[0127] The difference between this example and Example 3 is that the single-sided thickness of the modified polyurea coating is 30 nm.

[0128] The rest of the preparation method and parameters are consistent with Example 3.

[0129] Example 12

[0130] The difference between this example and Example 3 is that the single-sided thickness of the modified polyurea coating is 200 nm.

[0131] The remaining preparation methods and parameters remain consistent with Example 3.

[0132] Comparative Example 1

[0133] The difference between this comparative example and Example 1 is that the modified current collector base film is replaced by a pure PP film, i.e., the PP film is not modified.

[0134] The remaining preparation methods and parameters remain consistent with Example 1.

[0135] Comparative Example 2

[0136] The difference between this comparative example and Example 1 is that no aluminum hypophosphite is added in step (1), i.e., the polyurea coating is not modified.

[0137] The remaining preparation methods and parameters remain consistent with Example 1.

[0138] Performance testing

[0139] I. Adhesion, tensile strength, and elongation at break of the composite current collectors prepared in the above examples and comparative examples are tested:

[0140] 1) Adhesion: The composite current collector sample is cut into a test piece with a width of 24 mm and a length of 300 mm, one end of the cut test piece is folded with the adhesive side facing out to form a folded layer about 12 mm long; the other end of the test piece is pasted to one end of a steel plate, and a tape roller is rolled twice at a speed of 600 mm / min; placed in an electronic peeling tester, set the test speed to 300 mm / min and the test piece width to 24 mm; the device automatically records the force value during peeling, and the peeling strength of the test piece is reported accordingly.

[0141] 2) Tensile strength: The tensile strength of the composite current collector prepared above is tested according to standard GB / T 1040.3-2006.

[0142] 3) Elongation at break: The elongation at break of the composite current collector prepared above is tested according to standard GB / T 1040.3-2006.

[0143] II. Lithium ion batteries are prepared based on the above composite current collectors, and then safety performance tests are performed.

[0144] 1) Battery preparation: For the positive electrode, the positive electrode current collector uses a conventional aluminum foil (thickness of 13 μm), and the positive electrode material uses LiNi 0.6 Mn 0.2 Co 0.2O2 (NCM622); for the negative electrode: the negative electrode current collector is the composite current collector prepared in the application, and the negative electrode material is artificial graphite; for the separator, an aluminum oxide ceramic coated polyethylene separator (25 pm in thickness) is used; for the electrolyte, 1 mol·L -1 LiPF6 carbonate solution, the carbonate including propylene carbonate, vinyl carbonate and methyl ethyl carbonate in a mass ratio of 1:1:1; using the above materials, a lithium ion battery is assembled according to a related process;

[0145] 2) Safety performance test: the safety performance of the battery is verified by a needle puncture experiment, and the specific process is as follows: the battery prepared above is placed in a needle puncture experiment device, wherein the diameter of the needle is 3 mm, the needle puncture speed is 10 mm / s, the sampling interval is 100 ms, and the sampling time is 15 min. If the safety performance is qualified, the battery should not explode, catch fire or smoke, and 100 batteries are taken as test samples.

[0146] The test results are shown in Table 1.

[0147] Table 1

[0148] Analysis:

[0149] From the above table, it can be seen that the polymer film is modified by the modified polyurea coating in the application, the modified polyurea coating has excellent rigidity, strength, high strain rate sensitivity and excellent mechanical properties, so the modified current collector base film prepared has excellent mechanical properties, thermal stability and adhesion, and is not easy to be damaged in the subsequent preparation process of the composite current collector. The battery prepared based on this has excellent physicochemical properties and safety performance.

[0150] From Example 1 and Examples 5-6, it can be seen that the mass ratio of the long carbon chain diamine and the alicyclic diamine is too large or too large, which will cause the improvement of the mechanical properties of the polyurea material to not reach the best effect, and the safety performance of the battery is weakened.

[0151] From Example 1 and Example 10, it can be seen that if the amine chain extender in step (1) is replaced by the aromatic chain extender 3,3'-dichloro-4,4'-diaminophenyl methane, the mechanical properties of the polyurea material cannot be significantly improved, and defects are easy to occur in the preparation process of the current collector.

[0152] From Example 1 and Examples 11-12, it can be seen that if the single-sided thickness of the modified polyurea coating is too small, the modification effect on the current collector base film is not obvious; if the single-sided thickness of the modified polyurea coating is large, although the performance of the current collector is improved, the improvement amplitude is small, and thickness unevenness is easy to occur, and the cost is increased.

[0153] From Example 1 and Comparative Example 1, if the PP film is not modified, the mechanical properties of the current collector base film cannot be improved, and the stability is poor. When subjected to stress or chemical reagents, etc., low performance or defects are more likely to occur, thereby affecting the physical and chemical properties of the composite current collector.

[0154] From Example 1 and Comparative Example 2, if the polyurea coating is not modified, the strain rate sensitivity and mechanical properties thereof are not as good as those of the modified polyurea coating, and thus the performance improvement of the current collector base film is small, and the optimal effect cannot be achieved.

[0155] The applicant declares that the technical solutions of the present application are illustrated by the above examples, but the present application is not limited to the above examples, i.e., it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A modified current collector base film, comprising a polymer film, and a modified polyurea coating disposed on at least one side surface of the polymer film.

2. The modified current collector base film of claim 1, wherein, The method for preparing the modified polyurea coating comprises the following steps: (a) mixing isocyanate, polyether polyol and active agent, and obtaining A component after reaction, the A component comprising -NCO containing prepolymer; (b) mixing terminal amino polyether, amine chain extender, functional filler and auxiliary agent, and obtaining B component; (c) mixing the A component and B component, and then spraying on the polymer film to form the modified polyurea coating.

3. The modified current collector base film of claim 1, wherein, The single-sided thickness of the modified polyurea coating is 50-500 nm, which can be 50-200 nm.

4. The modified current collector base film of claim 1, wherein, The material of the polymer film comprises any one or combination of at least two of polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenyl ether, polystyrene or polyimide; Optionally, the thickness of the polymer film is 1-10 μm.

5. A method for preparing the modified current collector base film of claim 1, comprising the following steps: coating a modified polyurea material on at least one side surface of a polymer film to obtain the modified current collector base film.

6. The production method according to claim 5, wherein The method for preparing the modified polyurea material comprises the following steps: (a) mixing isocyanate, polyether polyol and active agent, and obtaining A component after reaction, the A component comprising -NCO containing prepolymer; (b) mixing terminal amino polyether, amine chain extender, functional filler and auxiliary agent, and obtaining B component; (c) mixing the A component and B component to obtain the modified polyurea material.

7. The production method according to claim 6, wherein The isocyanate of step (a) comprises any one or combination of at least two of 2,4-dimethyl decane diisocyanate, 2,2-dimethyl decane diisocyanate, 2,2,4-trimethyl decane diisocyanate or 2,4,6-trimethyl decane diisocyanate monomer.

8. The production method according to claim 6, wherein The polyether polyol of step (a) comprises any one or combination of at least two of propylene glycol polyether, butanediol polyether, hexanediol polyether, polyoxypropylene glycol, polyoxypropylene triol or polytetrahydrofuran ether diol.

9. The production method according to claim 6, wherein The active agent of step (a) comprises any one or combination of at least two of polyether carbonate, allyl glycidyl ether or alkylene carbonate.

10. The production method according to claim 6, wherein The mass ratio of the isocyanate, polyether polyol and active agent of step (a) is (40-55):(44-55):(1-5).

11. The production method according to claim 6, wherein The terminal amino polyether of step (b) is an amino-terminated polyalkylene oxide compound; Optionally, the amino-terminated polyalkylene oxide compound comprises any one or combination of at least two of D-230, D-2000, T-403, T-5000, ZD-1200, ZD-140, ZD-123, ZT-143 or ZT-1500; Optionally, the amine chain extender of step (b) comprises long carbon chain diamine and alicyclic diamine; Optionally, the long carbon chain diamine is a linear diamine with a carbon atom number greater than or equal to 10, and optionally a linear diamine with a carbon atom number in the range of C12-C30; Optionally, the long carbon chain diamine includes any one or a combination of at least two of decanediamine, undecanediamine, dodecanediamine, tridecanediamine, or tetradecanediamine; Optionally, the alicyclic diamine includes an alicyclic diamine with a molecular weight less than 300; Optionally, the alicyclic diamine with a molecular weight less than 300 includes any one or a combination of at least two of 3,3-dimethyl-4,4-dicyclohexylmethane diamine, isophorone diamine, or 4,4'-diaminodicyclohexylmethane; Optionally, the mass ratio of the long carbon chain diamine and the alicyclic diamine is 1:(0.2-2.5); Optionally, the functional filler in step (b) includes any one or a combination of at least two of a flame retardant, a hydrophilic compound, a plasticizer, an adhesion promoter, or an adhesive; Optionally, the flame retardant includes any one or a combination of at least two of polyvinyl silesquioxane, aluminum hypophosphite, or graphite; Optionally, the hydrophilic group in the hydrophilic compound includes any one or a combination of at least two of a carboxyl group, a sulfonic acid group, an amino group, an amine group, a hydroxyl group, an amide group, or an ether bond; Optionally, the plasticizer includes any one or a combination of at least two of dioctyl phthalate, isooctyl epoxy octadecanoate, dimethyl maleate, diisooctyl adipate, tricresyl phosphate, or tris(2-ethyl)hexyl trimellitate; Optionally, the adhesion promoter includes any one or a combination of at least two of a terpene resin, a special grade of pine rosin, a hydrogenated C5 petroleum resin, or a copolymerized petroleum resin; Optionally, the adhesive includes any one or a combination of at least two of a silane coupling agent, an acrylic acid, an epoxy resin, chlorinated polypropylene, or aminated polypropylene; Optionally, the mass ratio of the terminal amino polyether, the amine chain extender, the functional filler, and the auxiliary agent in step (b) is (40-60):(20-35):(0-20):(0-5).

12. The preparation method of claim 5, comprising the following steps: (1) adding polyether polyol into a reaction kettle, dehydrating at 90-120°C under negative pressure for 0.5-2h, then adding an active agent to continue dehydrating until the water content of the polyether polyol is ≤0.05%, then cooling to 40-60°C to add isocyanate, then heating to 80-90°C, and keeping the temperature for 2-3h to obtain a prepolymer with a mass fraction of -NCO of 13-16%, and then vacuum dehydrating to prepare the A component; wherein the mass ratio of isocyanate, polyether polyol, and active agent is (40-55):(44-55):(1-5); sequentially adding the terminal amino polyether, the amine chain extender, the functional filler, and the auxiliary agent into a high-speed disperser and dispersing for 30-60min, and then drying at 40-60°C to obtain the B component; wherein the mass ratio of the terminal amino polyether, the amine chain extender, the functional filler, and the auxiliary agent is (40-60):(20-35):(0-20):(0-5). (2) mixing the A component and the B component according to a volume ratio of 1:1 to obtain a modified polyurea material; (3) spraying the modified polyurea material on at least one side surface of the polymer film to obtain a modified current collector base film.

13. A composite current collector, wherein, The composite current collector comprises the modified current collector base film according to claim 1 or the modified current collector base film prepared by the preparation method according to claim 5, and an electrically conductive layer arranged on at least one side surface of the modified current collector base film.

14. The composite current collector of claim 13, wherein, The thickness of the electrically conductive layer is 500-2000 nm, and optionally 800-1200 nm; Optionally, an adhesive layer is further arranged between the electrically conductive layer and the modified current collector base film, and the material of the adhesive layer comprises any one or a combination of at least two of aluminum oxide, silicon oxide, titanium oxide, elemental nickel, elemental chromium, elemental titanium, nickel-chromium alloy, nickel-chromium-copper alloy, or silicon-aluminum alloy; Optionally, the adhesive force between the electrically conductive layer and the adhesive layer is 100-900 N / m; Optionally, a protective layer is arranged on the side surface of the electrically conductive layer away from the modified current collector base film, and the material of the protective layer comprises any one or a combination of at least two of elemental nickel, elemental chromium, nickel-based alloy, copper-based alloy, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper chromate, copper chromite, graphite, carbon black, carbon nanometer quantum dot, carbon nanotube, carbon nanofiber, or graphene; Optionally, the thickness of the protective layer is 10-100 nm, and optionally 20-80 nm.

15. A lithium-ion battery, wherein, The electrode tab of the lithium ion battery comprises the composite current collector according to claim 13 or the composite current collector prepared based on the modified current collector base film according to claim 1.

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