Composite current collector and preparation method thereof, electrode plate and battery

Abstract

The invention discloses a composite current collector and a preparation method thereof, an electrode plate and a battery, and belongs to the technical field of batteries. Three different coupling agents, PTA, Sb2O3, high-conductivity nano metal powder and a carbon-based conductive agent are added into EG (ethylene glycol), a composite PET conductive interlayer is prepared through a microwave esterification reaction, the front face and the back face of a composite PET conductive interlayer film serve as a substrate, a metal thin layer is obtained through magnetron sputtering of copper atoms, and then the target composite current collector is obtained after hot pressing and rolling. Compared with a conventional composite current collector, the composite current collector has higher conductivity and stronger mechanical performance, and meanwhile, due to optimization of the overall structure of the interlayer and the metal layer, the composite current collector is thinner, more space can be reserved for active substances, and the energy density of the battery is indirectly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a composite current collector and a preparation method thereof, an electrode sheet and a battery. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Lithium-ion battery is the most widely used and most mature secondary battery system, mainly composed of positive electrode material, negative electrode material, separator, current collector and electrolyte. The current collector is an indispensable part for connecting lithium-ion battery and external circuit. At present, metal foil is usually used as the current collector. This current collector has a heavy weight per unit area, a high amount of metal copper material, and a relatively high cost; and when it is used on battery materials, the safety is also relatively poor. Based on the characteristics of traditional current collectors, a composite current collector is proposed. For example, CN117936798A discloses a composite current collector and its preparation method and a negative electrode sheet. A composite current collector includes a PET film; a composite conductive layer, the composite conductive layer is arranged on both sides of the PET film; a metal plating layer, the metal plating layer is arranged on the composite conductive layer away from the PET film The side of the pole ear connection; wherein the composite conductive layer includes at least two of graphene, carbon nanotubes, and conductive carbon black.

[0004] The above patent document forms a composite structure layer by conductive layer + PET film + conductive layer and closely adheres to the copper / aluminum base foil. Although the conductive performance is improved, the performance improvement is very limited, and the mechanical properties of the entire negative / positive current collector cannot be guaranteed. At the same time, the excessive number of layers of the entire current collector structure leads to the instability of the entire current collector structure. After a long period of charge and discharge cycle of the lithium-ion battery cell, the resistivity increases, and the effect is not as good as the performance of pure metal Cu / Al foil. Therefore, how to effectively improve the mechanical properties of the current collector while ensuring stable conductivity during the entire current collector cycle is a technical problem that needs to be solved in this field. Summary of the invention

[0005] In order to improve the electrical conductivity and mechanical properties of the current collector itself, the object of the present invention is to provide a composite current collector and a preparation method thereof. By adding different coupling agents, terephthalic acid (PTA), Sb2O3, highly conductive nano-metal powder, and carbon-based conductive agent into EG (ethylene glycol), a composite PET conductive interlayer is prepared through microwave esterification reaction (PET refers to polyethylene terephthalate). Using the front and back sides of the composite PET conductive interlayer film as the substrate, a metal thin layer is obtained by magnetron sputtering of copper atoms, and then the target composite current collector is obtained after hot pressing and rolling. Compared with the conventional composite current collector, the composite current collector has higher electrical conductivity, stronger mechanical properties, and more excellent flame retardancy. At the same time, due to the optimization of the overall structure of the interlayer and the metal layer, the composite current collector is thinner, which can leave more space for the active material and indirectly improve the energy density of the battery.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] In the first aspect, the present invention provides a composite current collector, including a composite conductive layer and a metal conductive layer disposed on at least one surface of the composite conductive layer;

[0008] The composite conductive layer includes a polymer material and fillers doped in the polymer material;

[0009] The fillers include coupling agents and conductive fillers; the coupling agents are any three of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and complex coupling agents; the conductive fillers are highly conductive nano-metal powder and / or carbon-based conductive agents;

[0010] The polymer material is polyethylene terephthalate, which is polymerized from polymer monomers and polyols under the catalysis of a catalyst.

[0011] In one or more embodiments, the polymer monomer is terephthalic acid (PTA); the polyol is ethylene glycol (EG).

[0012] In one or more embodiments, the silane coupling agent is KH550; the titanate coupling agent is HY201; the aluminate coupling agent is HYA1; the phosphate coupling agent is 2-hydroxyethyl methacrylate phosphate; the complex coupling agent is methacryloyl chromium complex or chlorinated hydroxy stearic acid chromium complex, and the methacryloyl chromium complex is methacryloyl chromium chloride.

[0013] The mass ratios of the three coupling agents are added in a gradient distribution. The mass ratios of the three coupling agents in the alcohol solvent are 4% - 6%: 2% - 3%: 0.5% - 1.5%. The function of the coupling agent is to change the in-situ dispersion effect. For example, silane coupling agent (KH550), titanate coupling agent (HY201) and complex coupling agent are added according to the mass ratio of 4% - 6%: 2% - 3%: 0.5% - 1.5%. These three coupling agents are the combination with the best tested and verified effects and the least side effects. Excessive use will affect the physical, electrical, thermal and optical properties of the product, etc.

[0014] In one or more embodiments, the conductive filler is a highly conductive nano metal powder and a carbon-based conductive agent. The performance is best improved by using them in combination. At the same time, compared with using a single conductive agent, it has advantages in cost saving and weight reduction.

[0015] The highly conductive nano metal powder is nano copper powder or nano silver powder. The D50 of the nano metal powder is 10 - 100 nm, preferably 20 - 60 nm. The conductivity ≥ 5.96×10 7 S / m. For example, these two materials, nano nickel powder and nano iron powder, have limited improvement in the conductive performance of the composite material and no obvious advantage in weight reduction. The conductivity of the nano metal powder needs to be above 5.96×10 7 S / m to have an obvious improvement effect.

[0016] In one or more embodiments, the carbon-based conductive agent includes one or more of carbon nanotubes (CNT), nano carbon fibers (VGCF), graphene, conductive carbon black (SP), graphite and carbon nanowires.

[0017] In one or more embodiments, the catalyst is Sb2O3 or Sn2O3, which is used to catalyze the polymerization reaction.

[0018] In one or more embodiments, the metal conductive layer includes copper or aluminum.

[0019] In one or more embodiments, the mass ratio of the polymer material monomer, catalyst, nano metal powder, and carbon-based conductive agent is 2:1:0.1 - 0.2:0.1 - 0.2.

[0020] The molar ratio of the polymer material monomer and ethylene glycol is 1.1 - 1.3:1.

[0021] In one or more embodiments, the composite conductive layer is a composite PET conductive interlayer, and the composite conductive layer is prepared by microwave radiation esterification. The thickness of the composite conductive layer is a 4 - 5 μm thin film; the thickness of the metal conductive layer is 0.5 - 1 μm. The thickness of the composite current collector is 5 - 7 μm.

[0022] Second aspect, the present invention provides a method for preparing the above composite current collector, comprising the following steps:

[0023] (1) Dissolve three different coupling agents in a polyol solvent to obtain a mixed solution;

[0024] (2) Add a polymer material monomer, a catalyst, nano metal powder, and a carbon-based conductive agent to the mixed solution in proportion. Place the mixed reactant solution in a sealed container, remove oxygen with nitrogen, and then perform microwave radiation esterification. At the same time, use magnetic stirring to assist the reaction. Let the reaction product release heat and solidify, wash and dry to obtain a composite conductive layer;

[0025] (3) Make the composite conductive layer into a film. Using this as a substrate, perform magnetron sputtering on at least one surface thereof to obtain a current collector semi-finished product containing a magnetron sputtered metal conductive layer, and then thermally press and roll it to obtain a composite current collector.

[0026] In one or more embodiments, in step (1), disperse for 2 - 3 hours at 30 - 40 °C.

[0027] In one or more embodiments, in step (2), the microwave irradiation power is 1300 - 1800 W.

[0028] The magnetic stirring speed is 800 - 1200 rpm; the reaction time is 30 - 60 min, preferably 35 - 45 min;

[0029] In one or more embodiments, in step (3), the thickness of the magnetron sputtered metal conductive layer is 0.5 - 1 μm, the pressure of thermal pressing is 8 - 20 MPa, the temperature is 100 - 200 °C, and the treatment time is 8 - 12 h.

[0030] In a specific embodiment, the preparation of the composite conductive layer, namely the composite PET conductive interlayer:

[0031] 1. Dissolve three different coupling agents in EG according to the mass fraction ratio of 4% - 6%: 2% - 3%: 0.5% - 1.5%, and then disperse at 30 - 40 °C for 2 - 3 hours. The coupling agents are any three of silane coupling agent (KH550), titanate coupling agent (HY201), aluminate coupling agent (HYA1), phosphate coupling agent, and complex coupling agent;

[0032] 2. Add terephthalic acid (PTA), Sb2O3, highly conductive nano-metal powder, and carbon-based conductive agent to the solution in step 1 according to a mass ratio of 2:1:0.1 - 0.2:0.1 - 0.2. Transfer the mixed reactants into a sealed borosilicate glass bottle (closed system). After blowing away the excess oxygen with nitrogen, place it in a microwave reactor for microwave radiation esterification. At the same time, use a magnetic stirrer to assist the reaction. After reacting for 35 - 45 minutes, let the reaction product release heat and solidify, then wash and dry to obtain a composite PET conductive interlayer.

[0033] 3. Preparation of composite current collector:

[0034] Hot melt press the composite PET conductive interlayer in step 2 into a 4 - 5 μm thin film. Then, use the obtained thin film as a substrate and perform copper atom magnetron sputtering on its upper and lower surfaces to obtain a semi-finished current collector with copper foil layers deposited on the upper and lower surfaces. Place the semi-finished current collector in a hot press equipment for hot pressing and rolling to obtain a target composite current collector with a thickness of 5 - 7 μm.

[0035] Thirdly, the present invention provides an electrode tab, which includes the above-mentioned composite current collector.

[0036] Fourthly, the present invention provides a battery, which includes the above-mentioned composite current collector and / or the above-mentioned electrode tab.

[0037] One or some of the above technical solutions have the following advantages or beneficial effects:

[0038] (1) The present invention prepares a composite current collector, which includes a composite-structured PET conductive interlayer. Among them, the conductive filler can be filled into PET by in-situ polymerization to achieve efficient distribution, significant improvement in electrical properties, and improvement in other physical properties.

[0039] (2) The present invention uses a conductive layer + PET film + conductive layer to form a composite structure layer and closely adheres to the copper matrix foil. Compared with the traditional single copper matrix foil, an additional PET film is added. The alternating ester groups and aryl groups in the PET molecular chain form a rigid structure, endowing it with high tensile strength (>200 MPa) and anti-deformation ability, and can effectively maintain the structural integrity of the current collector during charge and discharge cycles. Therefore, the composite current collector prepared by the present invention has higher conductivity, stronger mechanical properties, and more excellent flame retardancy compared with the conventional composite current collector. At the same time, due to the optimization of the overall structure of the interlayer and the metal layer, the thickness of this composite current collector is thinner (the thickness of the conventional copper foil is 8 μm), which can leave more space for the active material and indirectly improve the energy density of the battery.

[0040] (3) The composite current collector prepared by the present invention uses a polymer material as the intermediate layer. This material has flame retardant properties and can fuse like a fuse during a short circuit to prevent thermal runaway, thereby improving the safety of the battery.

[0041] (4) The composite current collector uses a lightweight polymer material to replace part of the metal material, which can effectively reduce the mass of the non-active substances in the battery, reduce the weight of the battery, and increase the energy density of the battery by more than 5%.

[0042] (5) The polymer material forms a layered annular sponge structure around the active material layer in the battery (when a liquid phase substance touches the surface of a cold polymer solution, it will undergo a process of nucleation, growth, and self-assembly to form an ordered and closely packed array of water droplets. Eventually, the water droplets and the solvent in the polymer solution evaporate, leaving honeycomb-like pores. The porous structure prepared based on this principle generally has neatly arranged honeycomb-like pores. In addition, since the water vapor only contacts the surface of the polymer solution, the thickness of the porous structure is generally very thin and there is no multi-layer structure. See the gray area in Figure 1 ), which can absorb the stress generated during charge and discharge, maintain the integrity of the electrode interface, and thus extend the cycle life of the battery by more than about 5%.

[0043] (6) Compared with the prior art in which PET (polyethylene terephthalate) is combined with a conductive agent when preparing the composite current collector, in this application, a conductive agent is added during the preparation of PET to achieve in-situ combination of the conductive agent and PET, thereby forming a PET containing a conductive agent as a conductive interlayer. Its advantages are better conductivity, and the conductive filler is more uniform in PET and more closely combined with PET. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The schematic diagrams of the present invention, which are part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0045] Figure 1 It is a structural diagram of the composite current collector prepared in Example 1 of the present invention; wherein, 1 is the thickness of the copper foil layer, and 2 is the composite PET conductive interlayer. DETAILED DESCRIPTION OF THE INVENTION

[0046] In view of the deficiencies in the conductivity, mechanical properties, and flame retardancy of the current collector in the prior art, the present invention provides a composite current collector and a preparation method thereof.

[0047] The first typical embodiment of the present invention provides a composite current collector, including a composite conductive layer and a metal conductive layer disposed on at least one surface of the composite conductive layer;

[0048] The composite conductive layer includes a polymer material and fillers doped in the polymer material;

[0049] The fillers include coupling agents and conductive fillers; the coupling agents are any three of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and complex coupling agents; the conductive fillers are highly conductive nano metal powders and / or carbon-based conductive agents;

[0050] The polymer material is polyethylene terephthalate, which is polymerized from polymer material monomers and polyols under the catalysis of a catalyst.

[0051] The composite conductive layer is formed by the esterification reaction of PTA and EG to produce PET. Among them, the conductive fillers achieve in-situ polymerization, and conductive fillers are introduced in-situ in the conductive PET interlayer, thereby improving the performance.

[0052] In one or more of the embodiments of this implementation manner, the polymer material monomer is terephthalic acid (PTA); the polyol is ethylene glycol (EG). Ethylene glycol (EG) is a polymerization reactant that reacts with PTA to produce PET. PTA and EG undergo an esterification reaction to produce PET.

[0053] In one or more of the embodiments of this implementation manner, the silane coupling agent is KH550; the titanate coupling agent is HY201; the aluminate coupling agent is HYA1; the phosphate coupling agent is 2-hydroxyethyl methacrylate phosphate; the complex coupling agent is chromium chloro-hydroxy stearate complex or chromium methacryloyl complex.

[0054] Any three coupling agents are added according to a gradient mass fraction ratio. The mass fraction ratio of the three coupling agents in the alcohol solvent is 4% - 6%: 2% - 3%: 0.5% - 1.5%. The three coupling agents are a combination of coupling agents with the best tested and verified effects and the least side effects. Excessive use will affect the physical properties, electrical properties, thermal properties, optical properties, etc. of the product.

[0055] In one or more of the embodiments of this implementation manner, the conductive fillers are highly conductive nano metal powders and carbon-based conductive agents. When the highly conductive nano metal powders and carbon-based conductive agents are used in combination as conductive fillers, the performance is improved best. At the same time, compared with using a single conductive agent, it has advantages in cost savings and weight reduction.

[0056] In one or more of the embodiments of this implementation manner, the highly conductive nano metal powder is nano copper powder or nano silver powder. The D50 of the nano metal powder is 10 - 100 nm, preferably 20 - 60 nm. The conductivity ≥ 5.96×10 7S / m. Materials such as nano-nickel powder and nano-iron powder have limited improvement in the electrical conductivity of the composite material and no obvious advantage in weight reduction. The electrical conductivity of nano-metal powder needs to be above 5.96×10 7 S / m to have an obvious improvement effect.

[0057] In one or more embodiments of this implementation manner, the carbon-based conductive agent includes one or more of carbon nanotubes (CNT), vapor-grown carbon nanofibers (VGCF), graphene, conductive carbon black (SP), graphite, and carbon nanowires.

[0058] In one or more embodiments of this implementation manner, the catalyst is Sb2O3 or Sn2O3, which is used to catalyze the polymerization reaction.

[0059] In one or more embodiments of this implementation manner, the metal conductive layer includes copper or aluminum.

[0060] In one or more embodiments of this implementation manner, the mass ratio of the polymer material monomer, catalyst, nano-metal powder, and carbon-based conductive agent is 2:1:0.1 - 0.2:0.1 - 0.2.

[0061] In this implementation manner, the molar ratio of the polymer material monomer to the polyol is 1.1 - 1.3:1.

[0062] In one or more embodiments of this implementation manner, the composite conductive layer is a composite PET conductive interlayer with a thickness of 4 - 5 μm thin film; the thickness of the metal conductive layer is 0.5 - 1 μm. The thickness of the composite current collector is 5 - 7 μm.

[0063] In the second implementation manner, the present invention provides a method for preparing the above composite current collector, including the following steps:

[0064] (1) Dissolve three different coupling agents in polyol to obtain a mixed solution;

[0065] (2) Add the polymer material monomer, catalyst, nano-metal powder, and carbon-based conductive agent to the mixed solution in proportion. Place the mixed reactant solution in a closed container, remove oxygen with nitrogen, and then carry out microwave radiation esterification while using stirring to assist the reaction. Let the reaction product release heat and solidify, wash and dry to obtain the composite conductive layer;

[0066] (3) Make the composite conductive layer into a thin film. Using this as a substrate, carry out magnetron sputtering on at least one of its surfaces to obtain a current collector semi-finished product containing a magnetron sputtered metal conductive layer, and then hot press and roll it to obtain the composite current collector.

[0067] In one or more embodiments of this implementation manner, in step (1), disperse for 2 - 3 hours at 30 - 40 °C.

[0068] In one or more embodiments of this embodiment, in step (2), the microwave irradiation power is 1300-1800 W. Microwave irradiation is a low-cost and high-efficiency synthesis method. The catalytic reaction efficiency of far-infrared radiation and ultraviolet radiation is too low, and ion beam radiation has high equipment requirements and high costs.

[0069] In one or more embodiments of this embodiment, in step (2), the magnetic stirring speed is 800-1200 rpm; the reaction time is 30-60 min, preferably 35-45 min;

[0070] In one or more embodiments of this embodiment, in step (3), the thickness of the magnetron sputtered metal conductive layer is 0.5-1 μm, the pressure of hot pressing is 8-20 MPa, preferably 10-15 MPa, the temperature is 100-200 °C, and the treatment time is 8-12 h.

[0071] In a specific embodiment, the preparation of the composite conductive layer, i.e., the composite PET conductive interlayer:

[0072] 1. Dissolve three different coupling agents in EG according to the mass fraction ratio of 4%-6%: 2%-3%: 0.5%-1.5%, and then disperse at 30-40 °C for 2-3 hours. The coupling agents are any three of silane coupling agent (KH550), titanate coupling agent (HY201), aluminate coupling agent (HYA1), phosphate ester coupling agent, and complex coupling agent;

[0073] 2. Add terephthalic acid (PTA), Sb2O3, highly conductive nano metal powder, and carbon-based conductive agent to the solution in step 1 according to the mass ratio of 2:1: 0.1-0.2: 0.1-0.2, and transfer the mixed reactants into a sealed borosilicate glass bottle (closed system). After blowing off the excess oxygen with nitrogen, put it into a microwave reaction furnace for microwave radiation esterification, and use a magnetic stirrer to assist the reaction. After reacting for 35-45 min, let the reaction product release heat and solidify, wash and dry to obtain the composite PET conductive interlayer.

[0074] 3. Preparation of the composite current collector:

[0075] Hot melt press the composite PET conductive interlayer in step 2 into a 4-5 μm thin film, and then use the obtained thin film as a substrate to perform copper atom magnetron sputtering on its upper and lower surfaces to obtain a semi-finished current collector with copper foil layers deposited on the upper and lower surfaces, and put the semi-finished current collector into a hot pressing device for hot pressing and winding to obtain a target composite current collector with a thickness of 5-7 μm.

[0076] In the third embodiment, the present invention provides an electrode tab, including the above-mentioned composite current collector.

[0077] Fourth Embodiment, the present invention provides a battery, comprising the above-mentioned composite current collector and / or the above-mentioned electrode tab.

[0078] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0079] Example 1

[0080] 1. Dissolve silane coupling agent (KH550), titanate coupling agent (HY201) and complex coupling agent (chloro-hydroxy stearic acid chromium complex) in EG according to the mass fraction ratio of 5%:2.5:1.5% (the mass ratio is the mass ratio of the entire mixed solution), and then disperse at 35°C for 2.5 hours.

[0081] 2. Add PTA, Sb2O3, silver nanoparticles with a D50 of 40nm, and graphene to the solution in step 1 according to the mass ratio of 2:1:0.15:0.15, where the molar ratio of PTA to EG in step 1 is 1.2:1. Transfer the mixed reactants into a sealed borosilicate glass bottle, remove excess oxygen with nitrogen, and then put it into a microwave reactor for microwave radiation esterification. The irradiation power is 1500W, and at the same time, use a magnetic stirrer to assist the reaction. The stirring speed is 1000rpm. After reacting for 40 minutes, let the reaction product release heat and solidify, wash and dry to obtain a composite PET conductive interlayer.

[0082] 3. Hot melt press the composite PET conductive interlayer in step 2 into a 4.5um film. Then, use the obtained film as a substrate and perform copper atom magnetron sputtering on both its upper and lower surfaces. The thickness of the copper foil layers sputtered on both upper and lower surfaces is 1μm, to obtain a current collector semi-finished product with a thickness of 6.5μm. Put the current collector semi-finished product into a hot press device and hot press and roll it for 10 hours under the hot press conditions of 12MPa and 150°C to obtain a target composite current collector with a thickness of 6μm.

[0083] Figure 1 Structural diagram of the composite current collector prepared for Example 1; where 1 is the copper foil layer with a thickness of 1μm, and 2 is the composite PET conductive interlayer with a thickness of 4μm.

[0084] Example 2

[0085] 1. Dissolve silane coupling agent (KH550), titanate coupling agent (HY201) and complex coupling agent (chloro-hydroxy stearic acid chromium complex) in EG according to the mass fraction ratio of 5%:2.5:1.5%, and then disperse at 35°C for 2.5 hours.

[0086] 2. Add PTA, Sb2O3, silver nanoparticles with a D50 of 40 nm, and graphene to the solution in Step 1 at a mass ratio of 2:1:0.2:0.2. The molar ratio of PTA to EG in Step 1 is 1.3:1. Transfer the mixed reactants into a sealed borosilicate glass bottle, remove the excess oxygen with nitrogen, and then place it in a microwave reactor for microwave radiation esterification. The irradiation power is 1500 W. At the same time, use a magnetic stirrer to assist the reaction, with a stirring speed of 1000 rpm. After reacting for 40 min, let the reaction product solidify by releasing heat, wash, and dry to obtain a composite PET conductive interlayer.

[0087] 3. Hot melt press the composite PET conductive interlayer in Step 2 into a 4.5-μm film. Then, use the obtained film as a substrate and perform copper atom magnetron sputtering on both its upper and lower surfaces. The thickness of the copper foil layers sputtered on both upper and lower surfaces is 1 μm, obtaining a current collector semi-finished product with a thickness of 6.5 μm. Place the current collector semi-finished product in a hot pressing device and hot press and roll it for 10 h under the hot pressing conditions of 12 MPa and 150 °C to obtain a target composite current collector with a thickness of 6 μm.

[0088] Example 3

[0089] 1. Dissolve silane coupling agent (KH550), phosphate ester coupling agent, and aluminate coupling agent (HYA1) in EG at a mass fraction ratio of 5%:2.5:1.5%, and then disperse for 2 hours at a temperature of 35 °C.

[0090] 2. Add PTA, Sb2O3, copper nanoparticles with a D50 of 40 nm, and VGCF to the solution in Step 1 at a mass ratio of 2:1:1.5:1.5. The molar ratio of PTA to EG in Step 1 is 1.2:1. Transfer the mixed reactants into a sealed borosilicate glass bottle, remove the excess oxygen with nitrogen, and then place it in a microwave reactor for microwave radiation esterification. The irradiation power is 1500 W. At the same time, use a magnetic stirrer to assist the reaction, with a stirring speed of 1000 rpm. After reacting for 40 min, let the reaction product solidify by releasing heat, wash, and dry to obtain a composite PET conductive interlayer.

[0091] 3. Hot melt press the composite PET conductive interlayer in Step 2 into a 4.5-μm film. Then, use the obtained film as a substrate and perform copper atom magnetron sputtering on both its upper and lower surfaces. The thickness of the copper foil layers sputtered on both upper and lower surfaces is 1 μm, obtaining a current collector semi-finished product with a thickness of 6.5 μm. Place the current collector semi-finished product in a hot pressing device and hot press and roll it for 10 h under the hot pressing conditions of 12 MPa and 150 °C to obtain a target composite current collector with a thickness of 6 μm.

[0092] Example 4

[0093] 1. Silane coupling agent (KH550), titanate coupling agent (HY201) and complex coupling agent (chromium chloro-hydroxy stearate complex) are dissolved in EG according to the mass fraction ratio of 6%: 3%: 1.5%, and then dispersed at 35 °C for 2.5 hours.

[0094] 2. PTA, Sb2O3, nano-copper powder with D50 of 40 nm, and CNT are added to the solution in step 1 according to the mass ratio of 2:1:0.15:0.15. The molar ratio of PTA to EG in step 1 is 1.2:1. The mixed reactants are transferred into a sealed borosilicate glass bottle. After removing the excess oxygen with nitrogen, it is put into a microwave reactor for microwave radiation esterification. The irradiation power is 1500 W. At the same time, a magnetic stirrer is used to assist the reaction, and the stirring speed is 1000 rpm. After reacting for 40 min, the reaction product is exothermically solidified, washed and dried to obtain a composite PET conductive interlayer.

[0095] 3. The composite PET conductive interlayer in step 2 is hot melt pressed into a 4.5 μm thin film. Then, the obtained thin film is used as a substrate, and copper atoms are magnetron sputtered on both its upper and lower surfaces. The thickness of the copper foil layers magnetron sputtered on both upper and lower surfaces is 1 μm, obtaining a current collector semi-finished product with a thickness of 6.5 μm. The current collector semi-finished product is put into a hot pressing device and hot pressed and wound for 10 h under the hot pressing conditions of 12 MPa and 150 °C to obtain a target composite current collector with a thickness of 6 μm.

[0096] Comparative Example 1:

[0097] 1. PTA and Sb2O3 are added to the EG solution according to the mass ratio of 2:1. The molar ratio of PTA to EG is 1.2:1. The mixed reactants are transferred into a sealed borosilicate glass bottle. After removing the excess oxygen with nitrogen, it is put into a microwave reactor for microwave radiation esterification. The irradiation power is 1500 W. At the same time, a magnetic stirrer is used to assist the reaction, and the stirring speed is 1000 rpm. After reacting for 40 min, the reaction product is exothermically solidified, washed and dried to obtain a PET conductive interlayer.

[0098] 2. The PET conductive interlayer in step 1 is hot melt pressed into a 4.5 μm thin film. Then, the obtained thin film is used as a substrate, and copper atoms are magnetron sputtered on both its upper and lower surfaces. The thickness of the copper foil layers magnetron sputtered on both upper and lower surfaces is 1 μm, obtaining a current collector semi-finished product with a thickness of 6.5 μm. The current collector semi-finished product is put into a hot pressing device and hot pressed and wound for 10 h under the hot pressing conditions of 12 MPa and 150 °C to obtain a target composite current collector with a thickness of 6 μm.

[0099] Comparative Example 2:

[0100] Comparative Example 2 is a 6 μm copper foil for lithium batteries that can be purchased through conventional market channels.

[0101] Comparative Example 3

[0102] Different from Example 1, the conductive agent was added after preparing PET. The specific steps are as follows:

[0103] 1. Dissolve the finished PET powder in NMP to prepare a colloidal solution with a solid content of 10%. Mix nano-silver powder with a D50 of 40 nm and graphene into the above colloidal solution, and mechanically stir at 600 rpm for 8 h to obtain a homogeneous mixture. The nano-silver powder with a D50 of 40 nm and graphene each account for 5.5% of the PET mass in the colloidal solution. Then transfer the mixture into an oven and bake at 105 °C for 4 h to obtain composite PET.

[0104] 2. Hot melt press the composite PET in step 1 into a 4.5-μm-thick film. Then use the obtained film as the substrate, and perform copper atom magnetron sputtering on its upper and lower surfaces. The thickness of the copper foil layers sputtered on the upper and lower surfaces is 1 μm each, to obtain a current collector semi-finished product with a thickness of 6.5 μm. Then put the current collector semi-finished product into a hot press equipment and hot press and roll it for 10 h under the hot press conditions of 12 MPa and 150 °C to obtain a target composite current collector with a thickness of 6 μm.

[0105] Button battery preparation: Stir the graphite main material, 5% PVDF colloidal solution, and SP evenly in a certain proportion, and evenly coat the slurry on the current collectors prepared in the comparative examples and examples on a coater to make electrode sheets. Dry, roll, and punch the electrode sheets into round pieces with a diameter of 13 mm and weigh them for standby. Assemble the battery in a glove box. The electrolyte is 1 M LiPF6 + EC:DEC:DMC = 1:1:1 (volume ratio), and the metal lithium sheet is used as the counter electrode. The capacity test is carried out on an American Arbin BT2000 battery tester, and the charge-discharge voltage range is 0.005 - 2.0 V, and the charge-discharge rate is 0.1C and 1C.

[0106] Table 1 Comparison of the button battery performance of the examples and comparative examples

[0107]

[0108] As can be seen from Table 1, compared with Comparative Example 2, there is no obvious difference in the 0.1C charge specific capacity, 0.1C discharge specific capacity, and initial efficiency of the button battery test data composed of the composite current collectors in Examples 1 - 4; the 1C & 50-cycle capacity retention rate is significantly improved due to the improvement effect of the composite current collector on the stress during the charge-discharge process.

[0109] The 0.1C & 50-cycle capacity retention rate is the performance of the cycle performance, which ensures stable conductivity during the entire cycle of the current collector.

[0110] Table 2 Comparison of the physical and chemical properties of the examples and comparative examples

[0111]

[0112] As can be seen from Table 2, compared with Comparative Example 1 and Comparative Example 2, the resistivity of the composite current collectors in Examples 1-4 is smaller and is similar to that of the current collector in Comparative Example 2, and there is a significant decrease compared with the resistivity of the current collector in Comparative Example 1. Compared with Comparative Example 3, the in-situ polymerization of the present application can significantly improve the conductivity.

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite current collector, characterized in that, Comprising: A composite conductive layer and a metal conductive layer provided on at least one surface of the composite conductive layer; The composite conductive layer comprises a polymer material and fillers doped in the polymer material; The fillers include a coupling agent and a conductive filler; the coupling agent is any three of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a phosphate coupling agent, and a complex coupling agent; the conductive filler is a highly conductive nano metal powder and / or a carbon-based conductive agent; The polymer material is polyethylene terephthalate, which is polymerized from a polymer material monomer and a polyol under the catalytic action of a catalyst.

2. The composite current collector according to claim 1, wherein The polymer material monomer is terephthalic acid; Preferably, the polyol is ethylene glycol.

3. The composite current collector according to claim 1, wherein The silane coupling agent is KH550; Preferably, the titanate coupling agent is HY201; Preferably, the aluminate coupling agent is HYA1; Preferably, the phosphate coupling agent is 2-hydroxyethyl methacrylate phosphate; Preferably, the complex coupling agent is methacryloyl chromium complex or chlorohydroxy stearic acid chromium complex; Preferably, the mass ratio of the three coupling agents is added in a gradient distribution, and the mass ratio is 4-6:2-3:0.5-1.

5.

4. The composite current collector according to claim 1, wherein The conductive filler is a highly conductive nano metal powder and a carbon-based conductive agent; Preferably, the highly conductive nano metal powder is nano copper powder or nano silver powder; Preferably, the D50 of the nano metal powder is 10-100nm, preferably 20-60nm; Preferably, the conductivity of the nano metal powder ≥ 5.96×10 7 S / m; Preferably, the carbon-based conductive agent includes one or more of carbon nanotubes, nano carbon fibers, graphene, conductive carbon black, graphite, and carbon nanowires; Preferably, the catalyst is Sb2O3 or Sn2O3; Preferably, the metal conductive layer comprises copper or aluminum.

5. The composite current collector according to claim 1, wherein The mass ratio of the polymer material monomer, the catalyst, the nano metal powder, and the carbon-based conductive agent is 2:1:0.1-0.2:0.1-0.2; Preferably, the molar ratio of the polymer material monomer and the polyol is 1.1-1.3:

1.

6. The composite current collector according to claim 1, wherein, The thickness of the composite conductive layer is a 4-5μm thin film; Preferably, the thickness of the metal conductive layer is 0.5-1μm; Preferably, the thickness of the composite current collector is 5-7μm.

7. A method for preparing the composite current collector according to any one of claims 1-6, characterized in that, Comprising the following steps: (1) Dissolve three different coupling agents in a polyol solvent to obtain a mixed solution; (2) Add the polymer material monomer, the catalyst, the nano metal powder, and the carbon-based conductive agent to the mixed solution in proportion. Place the mixed reactant solution in a closed container, remove oxygen with nitrogen, and then carry out microwave radiation esterification. At the same time, use magnetic stirring to assist the reaction. Let the reaction product release heat and solidify, wash and dry to obtain the composite conductive layer; (3) Make the composite conductive layer into a thin film. Using this as a substrate, carry out magnetron sputtering on at least one surface thereof to obtain a current collector semi-finished product containing a magnetron sputtered metal conductive layer, and then hot press and roll it to obtain a composite current collector.

8. The preparation method according to claim 7, characterized in that, In step (1), disperse at 30-40°C for 2-3 hours; Preferably, in step (2), the microwave irradiation power is 1300-1800W; the magnetic stirring speed is 800-1200rpm; the reaction time is 30-60min; Preferably, in step (3), the thickness of the magnetron sputtered metal conductive layer is 0.5-1 μm, the pressure of hot pressing is 8-20 MPa, the temperature is 100-200 °C, and the treatment time is 8-12 h.

9. An electrode sheet, characterized in that, Comprising the composite current collector according to any one of claims 1-6 or the composite current collector obtained by the preparation method according to claim 7 or 8.

10. A battery, characterized in that, Comprising the composite current collector according to any one of claims 1-6 or the composite current collector obtained by the preparation method according to claim 7 or 8 and / or the electrode tab according to claim 9.

Images