Preparation Method of Secondary Battery Composite Current Collector

Abstract

The invention discloses a method for preparing a composite current collector for a secondary battery, the method comprising the following steps: step 1, preparing conductive paste A and conductive paste B; step 2, using NMP to adjust the viscosity of conductive paste A and conductive paste B; step 3, placing a surface-treated polymer on a transmission system, sequentially inkjet printing conductive paste A and conductive paste B on the upper surface of the polymer, and then entering a drying and condensing system C for drying, condensing, and recovering NMP treatment; step 4, sequentially inkjet printing conductive paste A and conductive paste B on the lower surface of the polymer treated in step 3, and then entering a drying and condensing system D for drying, condensing, and recovering NMP treatment; step 5, the polymer treated in step 4 is subjected to tail end rolling treatment to form a double-sided dense and stable composite current collector. The composite current collector can reduce the weight of the current collector, improve the energy density of the battery, and can also reduce the cost of the battery and improve the safety of the battery.

Description

Technical Field

[0001] The present invention belongs to the fields of sodium and lithium ion batteries, power batteries / electrochemical energy storage, and relates to a preparation method of a composite current collector, specifically a preparation method of a composite current collector for secondary batteries. Background Art

[0002] With the rapid development of electric vehicles, the requirements for the energy density of lithium ion batteries are continuously increasing. Without changing the weight of the positive and negative electrode materials, reducing the weight of other battery components is an effective means to improve the energy density. Copper foil is the carrier and current collector of the negative electrode material of lithium batteries and cannot be replaced by other materials in the short term. In the sodium ion battery system, aluminum foil can be used as the negative electrode current collector.

[0003] Currently, the thickness of aluminum foil is usually 10 μm, and the lowest can reach 8 μm; the thickness of copper foil is usually 6 μm, and the lowest can reach 4.5 μm; in terms of mass ratio, copper foil accounts for about 9%, and aluminum foil accounts for about 7%. The thinning of the current collector mainly brings: 1. Reducing the material cost of the battery; 2. Improving the energy density of the battery by thinning and weight reduction. Compared with 8 μm lithium battery copper foil, using 6 μm / 4.5 μm lithium battery copper foil can increase the energy density of lithium batteries by 5% / 9% respectively.

[0004] The composite current collector is a new technical route. By plating a certain thickness of copper layer on both sides of the polymer material layer, a "sandwich" - type composite structure is formed. The composite current collector can significantly reduce the material cost and weight of the current collector by replacing part of the metal material with a polymer material.

[0005] The preparation process of the composite current collector can currently be divided into a two - step method (magnetron sputtering - electroplating in water) and a three - step method (magnetron sputtering - evaporation - electroplating in water). The vacuum magnetron sputtering process has high requirements for equipment and is the key to affecting the product yield and performance. The main problems currently are that during magnetron sputtering, the base film such as PET is relatively thin, and it is easy to wrinkle and deform during winding and unwinding. During the coating process, the temperature rises, and it is easy to be pulled and deformed. The magnetron sputtering process requires high - voltage discharge, and there may be film perforation phenomena, affecting the consistency of the film and resulting in a low finished product rate. Based on this, it is necessary to provide a preparation method for high - quality composite current collectors.

[0006] Inkjet printing technology is a non - contact, mask - less patterning printing technology that can be achieved by directly spraying nano - sized solutions on flexible or rigid substrates. Summary of the Invention

[0007] The object of the present invention is to provide a preparation method of a composite current collector for secondary batteries. By using inkjet technology, a designed spraying device can obtain a composite current collector with consistency and high quality. This composite current collector can reduce the weight of the current collector, improve the energy density of the battery, reduce the cost of the battery, and improve the battery safety. In addition, this spraying system can recover the volatile organic solvents, achieving green environmental protection performance.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A preparation method of a composite current collector for secondary batteries includes the following steps:

[0010] Step 1: Prepare conductive paste A and conductive paste B

[0011] The conductive paste A is composed of 84-97% of conductive metal powder, 2-15% of binder, 0.1-1% of surfactant, and 0.1-0.5% of defoamer by mass percentage;

[0012] The conductive paste B is composed of 90-97% of conductive metal powder, 2-9% of binder, 0.1-1% of surfactant, and 0.1-0.5% of defoamer by mass percentage;

[0013] The content of conductive metal powder in the conductive paste B is greater than that in the conductive paste A, and the content of binder in the conductive paste A is greater than that in the conductive paste B;

[0014] The components of conductive metal powder, binder, surfactant, and defoamer in the conductive paste A and the conductive paste B can be the same or different;

[0015] The conductive metal powder is one or more of copper powder, aluminum powder, tin powder, zinc powder, silver powder, etc., with a particle size of 1-500 nm;

[0016] The binder is one or more of polyurethane, polyvinylidene fluoride, sodium carboxymethyl cellulose, etc.;

[0017] The surfactant is one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide (CTAB), triethylene glycol, polyoxyethylene octylphenyl ether, polyethylene oxide, etc.;

[0018] The defoamer is one or more of Tween 88, TritonX-100, etc.;

[0019] Step 2: Use N-methylpyrrolidone (NMP) to adjust the viscosities of the conductive paste A and the conductive paste B to 5-7 mPas;

[0020] Step 3: Place the surface-treated polymer on the transmission system. After inkjet printing conductive paste A and conductive paste B on the upper surface of the polymer in sequence, it enters the drying and condensation system C for drying (at 120°C), condensation, and NMP recovery treatment;

[0021] Step 4: After inkjet printing conductive paste A and conductive paste B on the lower surface of the polymer processed in Step 3 in sequence, it enters the drying and condensation system D for drying, condensation, and NMP recovery treatment;

[0022] Step 5: The polymer processed in Step 4 undergoes end rolling treatment to form a double-sided dense and stable composite current collector, and the composite current collector can be applied in sodium (lithium) ion batteries.

[0023] A continuous preparation device for implementing the above method includes a transmission system, an inkjet system, a drying and condensation system, and a rolling system, where:

[0024] The inkjet system is a dual-head inkjet printer, including a first inkjet printer, a second inkjet printer, a third inkjet printer, and a fourth inkjet printer. The ink cartridges of the first inkjet printer and the third inkjet printer are filled with conductive paste A, and the ink cartridges of the second inkjet printer and the fourth inkjet printer are filled with conductive paste B;

[0025] The drying and condensation system includes a drying and condensation system C and a drying and condensation system D. During the drying process, NMP volatilizes, and NMP is condensed and recovered;

[0026] The first inkjet printer, the second inkjet printer, the drying and condensation system C, the third inkjet printer, the fourth inkjet printer, the drying and condensation system D, and the rolling system are arranged in sequence along the transmission direction of the transmission system. According to the required thickness of the product, more print heads can be equipped to adjust the thickness.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. A non-contact conductive film is formed without expensive equipment and high temperature, and it will not cause any damage to the polymer substrate, maintaining the strength and toughness of the composite current collector.

[0029] 2. The continuous preparation device uses dual heads. Since the binder content in conductive paste A is slightly greater than that in conductive paste B, a gradient bonding layer is formed, enhancing the bonding strength with the substrate and improving the conductivity of the outer surface. In addition, the thickness of the conductive layer can be adjusted from 0.1 to 15 microns.

[0030] 3. The addition of the drying and condensation system can recover NMP, which is green and environmentally friendly. The equipment and steps are simple, the efficiency of the composite current collector can be improved, and large-scale mass production can be carried out.

[0031] 4. There is no need for high-purity target materials. At the same time, composite current collectors with different conductive materials can be flexibly produced according to needs, improving the energy density of the battery and reducing the cost of the battery.

[0032] 5. In a continuous preparation device, conductive paste A and conductive paste B are successively inkjet-printed on the polymer surface to form a metal gradient layer, which forms a stable metal current collector with the polymer. After end-rolling treatment, a double-sided dense and stable composite current collector is formed. The dense and high-quality composite current collector can reduce the weight and cost of the battery, and improve the energy density and safety of the battery.

[0033] 6. The inkjet printing technology is used to prepare a high-quality composite current collector. This composite current collector uses a polymer film to replace part of the metal foil in the traditional current collector. The lighter and lower-cost polymer can effectively improve the energy density of the battery and reduce the cost of the battery. Moreover, this composite current collector can balance a relatively thin thickness and high strength. The sandwich structure inhibits internal short circuits in the battery, improves the safety of the battery, and is not easily wrinkled during use. In addition, the device has a simple structure, low price cost, and is environmentally friendly. Description of the Drawings

[0034] Figure 1 It is a process flow chart for the preparation of the composite current collector. In the figure, 1. Conductive paste A, 2. Conductive paste B, 3. Polymer, 4. Transmission shaft, 5. Condensation system + drying system, 6. Composite conductive current collector, 7. Rolling;

[0035] Figure 2 It is a cross-sectional scanning electron microscope image of a single-layer composite current collector. Detailed Embodiments

[0036] The technical solutions of the present invention will be further described below in conjunction with embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0037] Example 1

[0038] This example takes the composite copper conductive current collector as an example and uses Figure 1The device shown is used for the preparation of a secondary battery composite current collector, where: Conductive paste A is made of 95% nano copper powder, 4% PVDF binder, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoamer, and NMP is used for viscosity adjustment. Conductive paste B is made of 97% nano copper powder, 2% PVDF binder, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoamer, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 50 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 1.2 microns, as Figure 2 shown.

[0039] Example 2

[0040] In this example, taking the composite copper current collector as an example, the Figure 1 device shown is used for the preparation of a secondary battery composite current collector, where: Conductive paste A is made of 85% nano copper powder, 14% PVDF binder, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoamer, and NMP is used for viscosity adjustment. Conductive paste B is made of 92% nano copper powder, 7% PVDF binder, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoamer, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 100 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 1.5 microns.

[0041] Example 3

[0042] In this example, taking the composite copper current collector as an example, the Figure 1 device shown is used for the preparation of a secondary battery composite current collector, where: Conductive paste A is made of 96% nano copper powder, 3% polyurethane, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoamer, and NMP is used for viscosity adjustment. Conductive paste B is made of 97% nano copper powder, 1.8% PVDF binder, 0.7% polyethylene glycol octyl phenyl ether, and 0.5% TritonX-100 defoamer, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 150 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 1.2 microns.

[0043] Example 4

[0044] In this example, taking the composite copper current collector as an example, the Figure 1The device shown is used for the preparation of a secondary battery composite current collector. Among them: Conductive paste A is made of 95% nano copper powder, 4% PVDF binder, 0.5% CTAB, and 0.5% TritonX-100 defoaming agent, and NMP is used for viscosity adjustment. Conductive paste B is made of 96% nano copper powder, 3% polyurethane, 0.5% CTAB surfactant, and 0.5% Triton X-100 defoaming agent, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 50 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 2 microns.

[0045] Example 5

[0046] In this example, taking the composite copper current collector as an example, Figure 1 The device shown is used for the preparation of a secondary battery composite current collector. Among them: Conductive paste A is made of 95% nano copper powder, 4% sodium carboxymethyl cellulose binder, 0.5% CTAB surfactant, and 0.5% TritonX-100 defoaming agent, and NMP is used for viscosity adjustment. Conductive paste B is made of 97% nano copper powder, 2% PVDF binder, 0.5% sodium dodecylbenzenesulfonate, and 0.5% TritonX-100 defoaming agent, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 50 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 10 microns.

[0047] Example 6

[0048] In this example, taking the composite copper current collector as an example, Figure 1 The device shown is used for the preparation of a secondary battery composite current collector. Among them: Conductive paste A is made of 85% nano copper powder, 14% PVDF binder, 0.5% triethylene glycol, and 0.5% TritonX-100, and NMP is used for viscosity adjustment. Conductive paste B is made of 92% nano copper powder, 7% PVDF binder, 0.5% CTAB surfactant, and 0.5% Tween 88, and the viscosity is adjusted to 6 mPas using NMP. The copper nano metal powder particles are 300 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 1.2 microns.

[0049] Example 7

[0050] In this example, taking the composite copper current collector as an example, Figure 1The device shown is used for the preparation of a secondary battery composite current collector, where: Conductive paste A is made of 85% nano copper powder, 14% PVDF binder, 0.5% triethylene glycol, and 0.5% Triton X-100, and NMP is used for viscosity adjustment. Conductive paste B is made of 92% nano copper powder, 7% polyurethane, 0.5% polyethylene oxide, and 0.5% Tween 88, and the viscosity is adjusted to 6 mPas using NMP, and the copper nano metal powder particles are 500 nm. During the preparation process, NMP is recovered through a drying and condensation system, and the thickness of the single-layer surface layer is about 50 microns.

Claims

1. A preparation method of a secondary battery composite current collector, characterized in that the method comprises the following steps: Step 1: Prepare conductive paste A and conductive paste B The conductive paste A is composed of 84 - 97% conductive metal powder, 2 - 15% binder, 0.1 - 1% surfactant, and 0.1 - 0.5% defoamer by mass percentage; The conductive paste B is composed of 90 - 97% conductive metal powder, 2 - 9% binder, 0.1 - 1% surfactant, and 0.1 - 0.5% defoamer by mass percentage; The content of the conductive metal powder in the conductive paste B is greater than that in the conductive paste A, and the content of the binder in the conductive paste A is greater than that in the conductive paste B; Step 2: Use NMP to adjust the viscosities of the conductive paste A and the conductive paste B to 5 - 7 mPa·s; Step 3: Place the surface - treated polymer on the transmission system, ink - jet print the conductive paste A and the conductive paste B on the upper surface of the polymer in sequence, and then enter the drying and condensation system C for drying, condensation, and NMP recovery treatment; Step 4: Ink - jet print the conductive paste A and the conductive paste B on the lower surface of the polymer treated in Step 3 in sequence, and then enter the drying and condensation system D for drying, condensation, and NMP recovery treatment; Step 5: The polymer treated in Step 4 undergoes end - point rolling treatment to form a double - sided dense and stable composite current collector.

2. The preparation method of the secondary battery composite current collector according to claim 1, characterized in that the conductive metal powder is one or more of copper powder, aluminum powder, tin powder, zinc powder, and silver powder.

3. The preparation method of the secondary battery composite current collector according to claim 1, characterized in that the particle size of the conductive metal powder is 1 - 500 nm.

4. The preparation method of the secondary battery composite current collector according to claim 1, characterized in that the binder is one or more of polyurethane, polyvinylidene fluoride, and sodium carboxymethyl cellulose.

5. The preparation method of the secondary battery composite current collector according to claim 1, characterized in that the surfactant is one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, triethylene glycol, octylphenol polyoxyethylene ether, and polyoxyethylene.

6. The preparation method of the secondary battery composite current collector according to claim 1, characterized in that the defoamer is one or two of Tween 88 and Triton X - 100.

7. The application of the composite current collector prepared by the method according to any one of claims 1 - 6 in sodium - ion batteries and lithium - ion batteries.

8. A continuous preparation device for implementing the method according to any one of claims 1 - 6, characterized in that the device comprises a transmission system, an ink - jet system, a drying and condensation system, and a rolling system, wherein: The ink - jet system is a double - nozzle ink - jet printer, including a first ink - jet printer, a second ink - jet printer, a third ink - jet printer, and a fourth ink - jet printer. The ink cartridges of the first ink - jet printer and the third ink - jet printer are filled with the conductive paste A, and the ink cartridges of the second ink - jet printer and the fourth ink - jet printer are filled with the conductive paste B; The drying and condensation system includes a drying and condensation system C and a drying and condensation system D. During the drying process, NMP volatilizes and is recovered by condensation. The first inkjet printer, the second inkjet printer, the drying and condensation system C, the third inkjet printer, the fourth inkjet printer, the drying and condensation system D, and the rolling system are arranged in sequence along the transmission direction of the transmission system.

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