CN115960378A - Polymer-based membrane for composite current collector, preparation method and application - Google Patents

Abstract

The invention relates to a polymer base film for a composite current collector, a composite current collector, a preparation method and an application thereof, and belongs to the technical field of current collectors. The material of the polymer base film is an n-type conductive polymer, and the repeating unit of the n-type conductive polymer structure is shown in formula (1):

R is the same or different, each independently selected from hydrogen, halogen, nitro, cyano, C1-C10 halogen-substituted alkyl, C2-C10 alkenyl, C2-C10 alkynyl and silicon-protected vinyl. The n-type conductive polymer has high conductivity, so there is no need to add a conductive layer or add a conductive agent, and it can be used as a minimalist high-performance composite current collector base film material; and it can avoid the swelling problem of the composite current collector while satisfying the adhesion of the coating Force demands.

Description

Polymer base film for composite current collector, composite current collector, preparation method and application

technical field

The invention relates to the technical field of current collectors, in particular to polymer base films for composite current collectors, composite current collectors, preparation methods and applications.

Background technique

The composite current collector includes a base film layer and metal layers on both sides of the base film. The material of the metal layer is metal such as copper and aluminum, and its thickness requirement is generally about 1 μm. A metal layer is formed on both sides of the base film by vacuum evaporation or magnetron sputtering + water electroplating process to prepare a composite current collector, which is suitable for lithium battery current collectors.

However, since the base film layer mostly uses polymer materials such as polyethylene terephthalate (PET), and these polymer materials are almost insulators, the conductivity is extremely poor, resulting in a sharp increase in the resistance of the current collector, which affects the internal battery life. resistance and power performance. In order to solve the above problems caused by the extremely poor conductivity polymer base film such as PET, the following two methods are mainly used at present: one is to add inorganic or organic polymer conductive agents to the substrate; the other is to increase the conductivity of the substrate on the substrate. layer. However, the above methods will greatly increase the number of preparation steps and difficulty of preparation of the composite current collector, increase the preparation cost, and reduce the production efficiency, which is not conducive to large-scale mass production and introduction of battery applications.

In addition to the problem of internal resistance, PET and other oxygen-containing group-based film materials contain a large number of ester groups, which is prone to swelling. After the electrolyte in the battery is in contact with the oxygen-containing base film material such as PET, the ester group in the PET and other oxygen-containing base film materials meets the ester group in the electrolyte and dissolves, causing the battery to During long-term use, the base film layer is prone to swelling, which destroys the chemical bond between the metal layer and the base film customer case number layer, resulting in the continuous deterioration of the peeling force between the metal layer and the base film layer of the composite current collector. , it is easy for the metal layer and the base film layer to fall off, which will affect the positive and negative interface inside the battery, resulting in the deterioration of the electrical performance of the battery and also affecting the safety of the battery. After the polymer material dissolves and enters the electrolyte, it will also increase the viscosity of the electrolyte, which will increase the resistance to ion transmission and lead to an increase in the internal resistance of the battery in the later stage of the battery. The use of polypropylene (PP) as the base film can alleviate the swelling problem to a certain extent, but the molecular structure of PP material has almost no oxygen-containing groups and other non-CH groups, so it is prone to insufficient bonding force with the metal layer. In some cases, the metal layer/metal coating on both sides of the base film has problems such as peeling of the metal coating, wrinkles of the metal coating when coating and stretching, and the separation of the active material by the separator after lamination with the lithium electroactive material, resulting in a significant drop in battery yield. Therefore, it is not conducive to the large-scale promotion and use of industrialization.

Contents of the invention

Therefore, the technical problem to be solved by the present invention is to overcome the extremely poor conductivity of the existing PET base film layer, the high cost of adding a conductive agent or the addition of a conductive layer, the reduction of production efficiency, and the swelling problem of the PET base film, resulting in battery The cycle performance is poor, and although the PP base film can relieve swelling, it has the problem of insufficient bonding force with the metal layer, thereby providing a polymer base film for a composite current collector, a composite current collector, a preparation method, and an application.

Technical scheme of the present invention:

A polymer base film for a composite current collector, characterized in that the material of the polymer base film is an n-type conductive polymer, and the repeating unit of the n-type conductive polymer structure is shown in formula (1);

Wherein, R is the same or different, each independently selected from hydrogen, halogen, nitro, cyano, C1-C10 halogen-substituted alkyl, C2-C10 alkenyl, C2-C10 alkynyl and silicon-protected vinyl .

R is the same or different, each independently selected from hydrogen, halogen, nitro, cyano, C1-C5 halogen-substituted alkyl, C2-C5 alkenyl, C2-C5 alkynyl and silicon-protected vinyl; preferably Yes, R is the same or different, each independently selected from one of hydrogen, halogen, nitro, cyano; more preferably, R is selected from hydrogen.

The structure of the n-type conductive polymer is shown in formula (2);

Where n is selected from an integer of 1-1,000,000, preferably an integer of 1-10,000, more preferably an integer of 1-1,000.

A composite current collector comprises a polymer base film layer formed by using a polymer base film for the composite current collector and metal layers located on both sides of the polymer base film layer.

The thickness of the metal layer on each side is 0.3 μm-1.0 μm, preferably 0.5 μm;

The material of the metal layer is any one of copper, aluminum or tin; preferably copper or aluminum.

The composite current collector is a composite positive current collector, the material of the metal layer is aluminum, the thickness of the polymer base film layer is 2.7-12 μm; preferably 6 μm; the thickness of the composite positive current collector is 3.7 μm- 14 μm, preferably 6-8 μm.

The composite current collector is a composite negative current collector, the material of the metal layer is copper, the thickness of the polymer base film layer is 2.7-12 μm; preferably 4 μm; the thickness of the composite negative current collector is 3.7 μm- 14 μm, preferably 5-7 μm.

A method for preparing a composite current collector, using a vacuum evaporation method to coat metal layers on both sides of the polymer base film, comprising the following steps: loading a metal target and a polymer base film to be plated into a vacuum evaporation inside the equipment, and vacuumize the vacuum evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the inside of the vacuum evaporation equipment to the evaporation temperature of the metal target, and The metal layer is plated on both sides of the polymer base film to obtain the composite current collector;

The composite current collector is a composite positive current collector, and the metal target is an aluminum target; the transfer rate of the polymer base film is 50-150m/min, preferably 100m/min;

Or, the composite current collector is a composite negative current collector, the metal target is a copper target, and the metal layer is a copper layer; the transmission rate of the polymer base film is 30-120m/min, preferably 90m/min.

The purity of the metal target is 99.9%; and/or, the evaporation temperature of the metal target is 600-1600°C, preferably 1100°C.

A pole piece, including a pole piece material and the composite current collector or the composite current collector obtained by the preparation method;

Preferably, the electrode sheet material is a positive electrode material, and the composite current collector is a composite positive electrode current collector with a compression retention of 3.0-3.8 g/cm ³ , preferably 3.65 g/cm ³ .

Preferably, the electrode sheet material is a negative electrode material, and the composite current collector is a composite negative electrode current collector with a compaction retention of 1.5-1.8 g/cm ³ , preferably 1.65 g/cm ³ .

The application of the pole piece in the preparation of lithium-ion batteries.

The technical solution of the present invention has the following advantages:

1. A polymer base film for a composite current collector of the present invention adopts an n-type high-conductivity polymer base film material, and the n-type high-conductivity polymer is benzodifurandione and its derivatives, and its structure repeats The unit has the formula (1). Large and rigid conjugated frameworks with n-type highly conductive polymers such as poly(benzodifurandiones) represented by formula (1), allowing easy delocalization of (bi)polarons and intrachain carriers , high conductivity and thermal conductivity, so it is used in the process of preparing composite current collectors, without adding an additional conductive layer on the base film, without adding a conductive agent to the base film material, and can be used as a minimalist high-performance Composite current collector base film material; at the same time, n-type highly conductive polymers such as poly(benzodifurandione) contain ketone groups on cyclic lactones, which have low compatibility with conventional carbonate electrolytes and can be easily It is good to avoid the problem of swelling of the composite current collector prepared by the base film during the long-term lithium battery cycle, and ensure that the cycle can reach the target value of the lithium battery design cycle; and n-type high-conductivity polymers such as poly(benzodifurandione) have A certain number of oxygen-containing groups, in a high-energy state, can be well combined with metal atoms such as Cu/Al sputtered on the base film to form a metal oxide seed transition layer, thereby improving the base film and metal coating/metal Layer adhesion, to meet the coating adhesion requirements.

2. Poly(benzodifurandione) (PBFDO) is a highly conductive polymer molecule with a conductivity of 2000S cm ^-1 , which is 10 times more conductive than the conventional n-type polymer shown in non-structure (1) , can alleviate the problem of increasing the internal resistance of the current collector caused by the polymer base film, reduce the internal resistance of the pole piece and the battery, and reduce the heat generated by the battery cell.

3. Using n-type highly conductive polymers such as poly(benzodifurandione) as the current collector of the base film can reduce the thickness of the metal coating/metal layer of the composite current collector while ensuring that the electrical resistance is basically unchanged. Reduce from the conventional 0.6-1.2um (preferably 0.8um) to 0.3-1.0um (preferably 0.5um), save plating time and material costs, and improve product competitiveness.

4. Using n-type highly conductive polymer base film materials such as poly(benzodifurandione), the thermal conductivity is improved, resulting in an increase in the heat-resistant temperature of the base film during evaporation or electromagnetic sputtering, which can further accelerate the base film. The coating transmission speed of the film, the transmission moving speed of the aluminum-plated polymer base film (composite positive current collector) is 50-150m/min, preferably 100m/min; the transmission of the copper-plated polymer base film (composite negative current collector) The moving speed is 30-120 m/min, preferably 90 m/min.

5. Due to the improved adhesion between n-type highly conductive polymer base film materials such as poly(benzodifurandione) and the metal coating/metal layer, the positive and negative electrodes can be coated by evaporation; and the metal coating and The base material is not easy to peel off under high pressure in real time. After the aluminized polymer base film (composite positive current collector) is made into a pole piece, the composite positive current collector is compacted and maintained at 3.0-3.8g/cm ³ , preferably 3.65g/cm ³ , greater than The conventional 3.4g/cm ³ , thereby improving the quality and volumetric energy density of the cell. Increased foil compaction limit.

6. Using n-type high-conductivity polymers such as poly(benzodifurandione) as the composite current collector of the base film, the battery pole pieces are obtained, and when entering the welding process, there is no need to add welding transfer sheets, and they can be directly connected by ultrasonic welding. On-chip, reduce welding process materials, reduce the number of electrode connections, reduce the volume of tabs in the cell shell, and increase the volumetric energy density of the cell.

7. The composite current collector using n-type high-conductivity polymer such as poly(benzodifurandione) as the base film can help the composite current collector to be quickly introduced into the battery cell, and can pass through the 5mm steel needle, 150-degree heat box and Safety performance verification such as heat spread greatly expands the application range of batteries and promotes the development of new energy industries.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

Fig. 1 is the capacity retention curve graph of the battery cycle 40 weeks of embodiment 1 and comparative example 1;

2 is an EIS internal resistance test curve of the composite positive current collectors of Example 1 and Comparative Example 1.

Detailed ways

Example 1

A composite positive current collector, which is a composite foil, includes a conductive polymer base film layer and metal layers located on both sides of the conductive polymer base film layer; the conductive polymer base layer that forms the conductive polymer base film layer The material of the membrane is poly(benzodifurandione) (PBFDO), and its structural formula is shown in formula (2), wherein n is 500. The thickness of the base film layer was 6 μm. The material of the metal layer is aluminum, and the thickness of each side of the aluminum layer is 0.5 μm.

The preparation method of the above-mentioned composite positive electrode current collector adopts the vacuum evaporation method to plate a metal layer, comprising the following steps: loading a 6 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and applying the vacuum Vacuumize the evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the vacuum evaporation equipment to 1100°C to evaporate the aluminum target, and keep the transmission moving speed of the base film at 100m/min , plate a metal aluminum layer with a thickness of 0.5 μm on both sides of the base film layer to obtain a composite aluminum current collector/composite positive electrode current collector/composite foil with a thickness of 7 μm. After the aluminum-coated composite current collector is prepared, the surface oxide layer is treated for inert protection, and then slitting, winding and vacuum packaging operations are performed.

Battery preparation process: The composite foil obtained above is used as the positive electrode current collector for homogenate coating of soft pack batteries, and the homogenate coating is based on active material (NCM811): conductive agent SP (conductive carbon black): binder PVDF (polyvinylidene fluoride) = 96.8:1.2:2 mass ratio ratio, after drying to obtain the corresponding active material coated positive electrode sheet. The positive pole pieces are compacted, and the compaction is maintained at 3.65g/cm ³ due to the strong bonding force of the coating. After slitting and laminating the positive pole piece, the composite positive current collector lug is directly welded to the connecting piece, and then liquid injection, packaging, pre-charging and other processes are performed to obtain a pouch battery.

Example 2

A composite negative current collector, which is a composite foil, includes a conductive polymer base film layer and metal layers located on both sides of the conductive polymer base film layer; the conductive polymer base layer that forms the conductive polymer base film layer The material of the membrane is poly(benzodifurandione) (PBFDO), and its structural formula is shown in formula (2), wherein n is 500. The thickness of the base film layer was 4 μm. The metal layer is made of copper, and the thickness of the copper layer on each side is 0.5 μm.

The preparation method of the above-mentioned composite negative electrode current collector adopts the vacuum evaporation method to plate a metal layer, comprising the following steps: loading a 4 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and applying the vacuum Vacuumize the evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the inside of the vacuum evaporation equipment to 1100°C to evaporate the copper target, and keep the transfer rate of the base film at 90m/min , plate a metal copper layer with a thickness of 0.5 μm on both sides of the base film layer to obtain a composite copper current collector/composite negative electrode current collector/composite foil with a thickness of 5 μm. After the composite copper current collector is prepared, the surface oxide layer is treated for inert protection, and then slitting, winding and vacuum packaging are performed.

Battery preparation process: The composite foil obtained above is used as the positive electrode current collector for homogenate coating of soft-pack batteries, and the proportion of homogenate coating is active material (graphite): conductive agent SP (conductive carbon black): binder SBR (styrene-butadiene rubber): binder CMC (sodium carboxymethyl cellulose) = 97.3:1.2:0.5:1.0, after drying, a negative electrode sheet coated with a corresponding active material is obtained. The negative pole piece is subjected to compaction treatment, and due to the strong bonding force of the coating, the compaction is maintained at 1.65g/cm ³ . After slitting and stacking the negative pole pieces, the composite foil tabs are directly welded to the connection piece, followed by liquid injection, packaging, pre-filling and other processes to obtain a pouch battery.

Example 3

A composite positive current collector, which is a composite foil, includes a conductive polymer base film layer and metal layers located on both sides of the conductive polymer base film layer; the conductive polymer base layer that forms the conductive polymer base film layer The material of the membrane is poly(dinitrobenzodifurandione), and its structural formula is shown in formula (4), wherein n is 500. The thickness of the base film layer was 2.7 μm. The metal layer is made of aluminum, and the thickness of the aluminum layer on each side is 1.0 μm.

The preparation method of the above-mentioned composite positive current collector adopts the vacuum evaporation method to plate a metal layer, comprising the following steps: loading a 2.7 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and depositing the The vacuum evaporation equipment is evacuated until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; the vacuum evaporation equipment is heated to 1100°C to evaporate the aluminum target, and the transmission movement rate of the base film is kept at 50m/ min, a metal aluminum layer with a thickness of 1.0 μm is plated on both sides of the base film layer to obtain a composite aluminum current collector/composite positive electrode current collector with a thickness of 4.7 μm. After the composite aluminum current collector is prepared, the surface oxide layer is treated for inert protection, and then slitting, winding and vacuum packaging are performed.

Battery preparation process: The composite foil obtained above is used as the positive electrode current collector for soft pack battery homogenate coating, according to the active material (NCM811): conductive agent SP (conductive carbon black): binder PVDF (poly Vinyl fluoride)=96.8:1.2:2 mass ratio proportioning, after drying, obtain the positive electrode sheet coated with the corresponding active material. The positive pole pieces are compacted, and the compaction is maintained at 3.65g/cm ³ due to the strong bonding force of the coating. After slitting and stacking the positive pole piece, the composite foil tab is directly welded to the connecting piece, followed by liquid injection, packaging, pre-filling and other processes to obtain a pouch battery.

Example 4

A composite positive current collector, which is a composite foil, includes a conductive polymer base film layer and metal layers located on both sides of the conductive polymer base film layer; the conductive polymer base layer that forms the conductive polymer base film layer The material of the membrane is poly(benzodifurandione), and its structural formula is shown in formula (2), wherein n is 500. The thickness of the base film layer was 12 μm. The material of the metal layer is aluminum, and the thickness of each side of the aluminum layer is 0.3 μm.

The preparation method of the above-mentioned composite positive current collector adopts the vacuum evaporation method to deposit a metal layer, comprising the following steps: loading a 12 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and applying the vacuum Vacuumize the evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the vacuum evaporation equipment to 1100°C to evaporate the aluminum target, and keep the transmission moving speed of the base film at 150m/min , plate a metal aluminum layer with a thickness of 0.3um on both sides of the base film layer to obtain a composite aluminum current collector/composite positive electrode current collector with a thickness of 12.6μm. After the composite aluminum current collector is prepared, the surface oxide layer is treated for inert protection, and then slitting, winding and vacuum packaging are performed.

Battery preparation process: The composite foil obtained above is used as the positive electrode current collector for soft pack battery homogenate coating, according to the active material (NCM811): conductive agent SP (conductive carbon black): binder PVDF (poly Vinyl fluoride)=96.8:1.2:2 mass ratio proportioning, after drying, obtain the positive electrode sheet coated with the corresponding active material. The positive pole piece is subjected to compaction treatment, because of the strong bonding force of the coating, the compaction maintains 3.65g/cm ³ . After slitting and stacking the positive pole piece, the composite foil tab is directly welded to the connecting piece, followed by liquid injection, packaging, pre-filling and other processes to obtain a pouch battery.

Comparative example 1

A composite positive current collector is a composite foil, including a PET base film layer and metal layers located on both sides of the base film layer; the thickness of the base film layer is 6 μm. The metal layer is made of aluminum, and the thickness of each side of the aluminum layer is 0.8 μm.

The preparation method of the above-mentioned composite positive electrode current collector adopts the vacuum evaporation method to plate a metal layer, comprising the following steps: loading a 6 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and applying the vacuum Vacuumize the evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the vacuum evaporation equipment to 1100°C to evaporate the aluminum target, and keep the transmission moving speed of the base film at 50m/min , plate a metal aluminum layer with a thickness of 0.8um on both sides of the base film layer to obtain a composite aluminum current collector/composite positive electrode current collector with a thickness of 7.6um. After the composite aluminum current collector is prepared, the surface oxide layer is treated for inert protection, and then slitting, winding and vacuum packaging are performed.

Battery preparation process: The composite foil obtained above is used as the positive current collector for soft pack battery homogenate coating, according to the active material (NCM811): conductive agent SP (conductive carbon black): binder PVDF (polyylidene difluoride Ethylene)=96.8:1.2:2 mass ratio proportioning is carried out, obtains the positive pole sheet that corresponding active material coats after drying. The positive pole piece is subjected to compaction treatment, and the compaction is maintained at 3.4g/cm ³ . After slitting and laminating the positive pole piece, the composite positive current collector is transferred to the lug and then welded to the connecting piece during welding. Then, liquid injection, encapsulation, pre-filling and formation are performed to obtain a pouch battery.

Comparative example 2

A composite positive current collector is a composite foil, including a PP base film layer and metal layers located on both sides of the base film layer; the thickness of the base film layer is 6 μm. The metal layer is made of aluminum, and the thickness of each side of the aluminum layer is 0.8 μm.

The preparation method of the above-mentioned composite positive electrode current collector adopts the vacuum evaporation method to plate a metal layer, comprising the following steps: loading a 6 μm base film and a metal target with a purity of 99.9% into a vacuum evaporation equipment, and applying the vacuum Vacuumize the evaporation equipment until the vacuum degree in the equipment is less than 1×10 ^-2 Pa; heat the vacuum evaporation equipment to 1100°C to evaporate the aluminum target, and keep the transmission moving speed of the base film at 50m/min , plate a metal aluminum layer with a thickness of 0.8um on both sides of the base film layer to obtain a composite aluminum current collector/composite positive electrode current collector with a thickness of 7.6um. After the aluminum-coated composite current collector is prepared, the surface oxide layer of the composite current collector is treated for inert protection, and then slitting, winding and vacuum packaging operations are performed.

Battery preparation process: The composite foil obtained above is used as the positive current collector for soft pack battery homogenate coating, according to the active material (NCM811): conductive agent SP (conductive carbon black): binder PVDF (polyylidene difluoride Ethylene)=96.8:1.2:2 mass ratio proportioning is carried out, obtains the positive pole sheet that corresponding active material coats after drying. The positive pole piece is subjected to compaction treatment, and the compaction is maintained at 3.4g/cm ³ . After slitting and laminating the positive pole piece, the composite positive current collector is transferred to the lug and then welded to the connecting piece during welding. Then, liquid injection, encapsulation, pre-filling and formation are performed to obtain a pouch battery.

test case

Cycle performance test: Cycle test was carried out on the pouch batteries obtained in the examples and comparative examples respectively, the charge and discharge conditions were 0.33C/1C, the temperature was 25°C, and the capacity retention data during the test cycle was tested. The results are shown in Table 1 and As shown in Figure 1, at the same time, the cell was disassembled after cycling to obtain the corresponding pole piece, and the degree of swelling of the pole piece was tested. The results are shown in Table 1.

Table 1. Test data

Remarks: pole piece swelling degree = (W2-W1)/W1×100%, W2 is the mass after immersion, W1 is the mass before immersion.

As shown in Figure 1 and Table 1, the PBFDO base film of embodiment 1-4 and poly (dinitrobenzodifurandione) base film current collector circulation performance, is better than the composite collection of the PET base film of comparative example 1 Fluid and the composite current collector of the PP base film of Comparative Example 2, this is because PBFDO contains ketone groups on the cyclic lactone, which is less compatible with conventional carbonate electrolytes, and can well avoid the preparation of the base film The problem of swelling of the composite current collector during the long-term lithium battery cycle ensures that the cycle can reach the target value of the lithium battery design cycle.

EIS (Electrochemical Impedance Spectroscopy) internal resistance test: EIS internal resistance test was performed on the button cells obtained in Example 1 and Comparative Example 1 respectively. Impedance measurement was performed immediately after cycling with a potential amplitude of 5 mV in the frequency range from 100 KHz to 10 mHz at 50% SOC (battery remaining capacity) on the 3rd cycle after the coin cell was formed. As shown in FIG. 2 , the internal resistance test of the PBFDO base film of Example 1 is better than that of the PET base film of Comparative Example 1.

Peeling force test: The peeling force test was carried out on the composite positive current collector/composite foil obtained in Example 1 and Comparative Examples 1 and 2 respectively. The peel force test method and process are as follows: 1. Cut the composite foil, and use a die to cut the composite foil to be tested to a size of 300mm×30mm. 2. Paste and fix the composite foil, take a flat thin steel plate with a size of 400mm×40mm, first paste a double-sided adhesive tape on the center of the steel plate (the length should be greater than the test length of the composite foil, and the same width as the composite foil) ), and smooth it with force to ensure that the double-sided adhesive sticks tightly to the center of the steel plate. Uncover the double-sided adhesive tape, and attach the lower surface of the metal coating on one side of the composite foil to be tested to the adhesive strip. It is necessary to ensure that the composite foil on the glued part is matched with the adhesive paper. 3. Installation test. There are two upper and lower clips on the tensile machine. Insert the steel plate pasted and fixed with the composite foil into the lower clip and fix it vertically. The composite foil of the glued part is on the bottom and the composite foil of the unglued part is on the top. Insert the composite foil of the unglued part into the upper clip to fix it, and keep the composite foil vertically, even if the composite foil of the glued part is 180° from the composite foil of the unglued part. After fixing the test sample, first calibrate and clear, set the test width to 23mm, the stripping length of the pole piece to 75mm, and the stripping speed to 150mm/min, and then start the test. The results are shown in Table 2.

Table 2. Peel force test data

As shown in Table 2, the peel strength of the PBFDO base film of Example 1 is better than that of the PP base film of Comparative Example 2, close to that of the PET base film of Comparative Example 1, and can meet the adhesion requirements of the coating.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. The polymer-based film for the composite current collector is characterized in that the material of the polymer-based film is an n-type conductive polymer, and the repeating unit of the n-type conductive polymer structure is shown in a formula (1);

wherein R is the same or different and is independently selected from hydrogen, halogen, nitro, cyano, C1-C10 halogen substituted alkyl, C2-C10 alkenyl, C2-C10 alkynyl and silicon protected vinyl.

2. The polymer-based film for the composite current collector as claimed in claim 1, wherein R is the same or different and is independently selected from hydrogen, halogen, nitro, cyano, C1-C5 halogen substituted alkyl, C2-C5 alkenyl, C2-C5 alkynyl and silicon protected vinyl;

preferably, R is the same or different and is independently selected from one of hydrogen, halogen, nitro and cyano;

more preferably, R is selected from hydrogen.

3. The polymer-based film for a composite current collector as claimed in claim 1 or 2, wherein the structure of the n-type conductive polymer is represented by formula (2);

wherein n is selected from the group consisting of integers from 1 to 1000000, preferably from 1 to 10000, more preferably from 1 to 1000.

4. A composite current collector comprising a polymer-based film layer formed from the polymer-based film for a composite current collector according to any one of claims 1 to 3, and metal layers on both side surfaces of the polymer-based film layer.

5. The composite current collector of claim 4, wherein the thickness of the metal layer on each side is between 0.3 μm and 1.0 μm, preferably 0.5 μm;

the metal layer is made of any one of copper, aluminum or tin; preferably copper or aluminium.

6. The composite current collector of claim 5, wherein the composite current collector is a composite positive electrode current collector, the metal layer is made of aluminum, and the polymer-based film layer has a thickness of 2.7-12 μm; preferably 6 μm.

Or the composite current collector is a composite negative current collector, the metal layer is made of copper, and the thickness of the polymer-based film layer is 2.7-12 mu m; preferably 4 μm.

7. The method of any one of claims 4 to 6, wherein the metal layers are plated on both surfaces of the polymer-based film by vacuum evaporation;

preferably, the method comprises the following steps: metal target material and metal target materialLoading the plated polymer base film into a vacuum evaporation device, and vacuumizing the vacuum evaporation device until the vacuum degree in the device is less than 1 multiplied by 10 ^-2 Pa; heating the interior of the vacuum evaporation equipment to the evaporation temperature of the metal target, and plating the metal layers on the two side surfaces of the polymer base film to obtain the composite current collector;

the composite current collector is a composite positive current collector, and the metal target is an aluminum target; the transmission moving speed of the polymer base film is 50-150m/min, preferably 100m/min;

or the composite current collector is a composite negative current collector, and the metal target is a copper target; the transport rate of the polymer-based film is 30-120m/min, preferably 90m/min.

8. The method according to claim 7, wherein the purity of the metal target material is 99.9%;

and/or the evaporation temperature of the metal target material is 600-1600 ℃, preferably 1100 ℃.

9. A pole piece, which is characterized by comprising a pole piece material and the composite current collector of any one of claims 3 to 6 or the composite current collector obtained by the preparation method of claim 7 or 8;

preferably, the pole piece material is a positive pole material, the composite current collector is a composite positive pole current collector, and the compaction and maintenance of the composite positive pole current collector are 3.0-3.8g/cm ³ Preferably 3.65g/cm ³ ；

Or the pole piece material is a negative electrode material, and the composite current collector is a composite negative electrode current collector which is compacted and kept at 1.5-1.8g/cm ³ Preferably 1.65g/cm ³ 。

10. Use of the pole piece of claim 9 in the manufacture of a lithium ion battery.

Images