Two-dimensional material-modified lithium battery cathode current collector surface coating, preparation and application

Abstract

The embodiment of the present application relates to a kind of two-dimensional material modified lithium battery positive pole current collector surface coating, preparation and application.The coating is formed by the conductive paste coating on the surface of positive pole current collector;The conductive paste includes by mass ratio: 57-88 parts of water, 5-12 parts of conductive carbon material, 1-5 parts of black phosphorus, 5-25 parts of hyperdispersant and 0.1-1 parts of pH regulator;The conductive carbon material in the coating is combined with two-dimensional sheet black phosphorus by C-P bond;The black phosphorus has two-dimensional wrinkle channel structure.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, and in particular to a two-dimensional material modified lithium battery cathode current collector surface coating, its preparation and application. Background Technology

[0002] Lithium-ion batteries are a type of chemical battery that relies on lithium ions shuttling between the positive and negative electrodes to achieve discharge. Due to their advantages such as high energy density, high operating voltage, long cycle life, and high charge / discharge rate, they are widely used in new energy vehicles, 3C products, and energy storage batteries. The main materials of a lithium-ion battery include positive electrode materials, negative electrode materials, electrolyte, and separator. However, in addition to these four main components, the current collector used to store the positive and negative electrode materials is also an important part of a lithium-ion battery. For lithium-ion batteries, aluminum foil is commonly used as the positive electrode current collector, and copper foil as the negative electrode current collector.

[0003] In the lithium battery field, aluminum foil is used as a current collector in lithium-ion batteries. Typically, the lithium-ion battery industry uses rolled aluminum foil as the positive electrode current collector, and the current collector plays a crucial role in improving the charge and discharge efficiency of lithium batteries. Coating the surface of the aluminum foil with a conductive paste can suppress battery polarization, reduce thermal effects, and improve the battery's rate performance. Simultaneously, it can improve the adhesion between the active material and the aluminum foil, reducing the amount of binder required. Lithium batteries using the aforementioned carbon-coated aluminum foil exhibit superior conductivity, rate performance, and heat dissipation compared to conventional plain foil lithium batteries. Existing carbon-coated aluminum foil for lithium batteries suffers from problems such as poor adhesion of the carbon coating, easy peeling, and low conductivity, severely impacting the long-cycle performance and energy density of lithium batteries in practical applications.

[0004] To address the aforementioned issues, Chinese invention patent CN 105895822 B discloses a method for preparing conductive coated aluminum foil, comprising cleaning and high-temperature annealing of the aluminum foil; applying an adhesive coating with a thickness of 1-2 μm to one side; applying a conductive carbon coating with a thickness of 1-4 μm to the surface of the adhesive coating; drying the foil in an oven to allow the conductive carbon coating and the adhesive coating to undergo a curing and cross-linking reaction; repeating steps (2)-(4) to sequentially apply the adhesive coating and the conductive carbon coating to the other side of the aluminum foil; and curing the foil in an oven to obtain a conductive coated aluminum foil with carbon coatings on both sides. The conductive coated aluminum foil prepared by this invention has high surface tension and good conductivity, and can effectively improve the electrical performance and consistency of the finished battery. However, the double-layer coating method used in this invention increases the adhesion between the carbon coating layer and the aluminum foil, which easily leads to uneven adhesion between the coatings, causing the coating to peel off during battery use; moreover, the double-layer coating is relatively thick, increasing costs and hindering the lightweighting of lithium batteries.

[0005] In conclusion, developing a positive electrode current collector surface coating with strong adhesion, high conductivity, and good mechanical properties is of positive significance for improving the cycle life of lithium batteries, increasing the energy density of lithium batteries, and improving the rate performance of lithium batteries. Summary of the Invention

[0006] The purpose of this invention is to provide a two-dimensional material modified lithium battery cathode current collector surface coating, its preparation and application, and to provide a cathode current collector surface coating with strong adhesion, high conductivity and good mechanical properties.

[0007] To this end, in a first aspect, embodiments of the present invention provide a two-dimensional material modified lithium battery positive electrode current collector surface coating, the coating being formed by coating a conductive paste onto the surface of the positive electrode current collector;

[0008] The conductive paste comprises, by mass ratio of each component: 57-88 parts water, 5-12 parts conductive carbon material, 1-5 parts black phosphorus, 5-25 parts superdispersant and 0.1-1 parts pH adjuster.

[0009] The conductive carbon material in the coating is bonded to the two-dimensional sheet-like black phosphorus through CP bonds; the black phosphorus has a two-dimensional pleated channel structure.

[0010] Preferably, the conductive carbon material includes at least one of carbon black, graphite, graphene, and carbon nanotubes;

[0011] The black phosphorus is orthorhombic and has a particle size of 10-900 nm.

[0012] The superdispersant is a block copolymer acrylic acid with multiple anchoring groups in its molecule, including -NR2 and -NR3. + -COOH, -COO - -SO3H - -SO3 - -PO4 -2 -OH, -SH, polyamines, polyols or polyethers;

[0013] The pH adjuster includes: hydroxides, ammonia, or organic amine compounds containing hydroxyl groups.

[0014] Secondly, embodiments of the present invention provide a method for preparing a two-dimensional material-modified coating on the surface of a lithium battery cathode current collector, the preparation method comprising:

[0015] Mix 57-88 parts of water, 5-12 parts of conductive carbon material, 1-5 parts of black phosphorus, 5-25 parts of superdispersant and 0.1-1 parts of pH adjuster, and mechanically disperse to obtain a mixed slurry.

[0016] The mixed slurry was ultrasonically dispersed.

[0017] The mixed slurry was dispersed using ball milling to obtain the coating slurry;

[0018] The coating slurry is applied to the surface of the positive electrode current collector aluminum foil and dried to obtain a two-dimensional material modified lithium battery positive electrode current collector surface coating.

[0019] Preferably, the specific method of mechanical dispersion includes dispersion using an emulsifier or dispersion using a high-speed disperser; the dispersion speed is 2000-12000 rpm, and the dispersion time is 30-120 min.

[0020] Preferably, the duration of ultrasonic dispersion is 10-60 min.

[0021] Preferably, the diameter of the zirconium beads used in the ball milling dispersion is 0.1-1 mm, and the ball milling dispersion time is 30-120 min.

[0022] Preferably, the coating method is one of the following: blade coating, spin coating, gravure coating, microgravure coating, and slot extrusion coating; the wet film thickness of the coating is 1-10 μm.

[0023] Preferably, the drying method is hot air drying, with a drying temperature of 70-150℃ and a drying time of 15-30 minutes.

[0024] Thirdly, embodiments of the present invention provide a positive electrode comprising a two-dimensional material modified surface coating for a lithium battery positive electrode current collector as described in the first aspect above.

[0025] Fourthly, embodiments of the present invention provide a lithium battery comprising a two-dimensional material modified surface coating for the positive electrode current collector of a lithium battery as described in the first aspect above.

[0026] The two-dimensional material-modified lithium battery cathode current collector surface coating provided in this invention has the following advantages compared with the prior art:

[0027] 1. The formation of CP bonds between black phosphorus and conductive carbon materials increases the bonding force between coating materials. The two-dimensional layered structure of black phosphorus has stronger structural integrity. Its two-dimensional pleated channel structure forms a stable bond with small-sized conductive materials. The interpenetration of the layers makes the wettability of the coating surface better and the bonding force with the positive electrode material stronger.

[0028] 2. As a semiconductor material, black phosphorus has a certain degree of conductivity. During the use of lithium batteries, it interacts with lithium ions in the positive electrode material, causing black phosphorus to transform from a semiconductor to a conductor, further improving its conductivity.

[0029] 3. The superdispersant in the material is a block copolymer acrylic acid with multiple anchoring groups, which can generate a strong affinity with the surface of nanoparticles, has excellent wetting, dispersion and stabilization effects, and acts as a binder in the system. During the drying process, the polymer chains firmly bind the components together, providing the coating with excellent stability. Attached Figure Description

[0030] Figure 1 A flowchart illustrating the preparation method of a two-dimensional material-modified lithium battery cathode current collector surface coating provided in this embodiment of the invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] This invention provides a two-dimensional material modified lithium battery positive electrode current collector surface coating, the coating being formed by coating a conductive paste onto the surface of the positive electrode current collector;

[0033] The conductive paste comprises, by mass ratio of each component: 57-88 parts water, 5-12 parts conductive carbon material, 1-5 parts black phosphorus, 5-25 parts superdispersant, and 0.1-1 parts pH adjuster.

[0034] The conductive carbon material in the coating is bonded to the two-dimensional sheet-like black phosphorus through CP bonds; the black phosphorus has a two-dimensional pleated channel structure.

[0035] The aforementioned conductive carbon materials include at least one of carbon black, graphite, graphene, and carbon nanotubes;

[0036] Black phosphorus has an orthorhombic crystal system and a particle size of 10-900 nm.

[0037] The superdispersant is a block copolymer acrylic acid with multiple anchoring groups in its molecule, including -NR2 and -NR3. + -COOH, -COO - -SO3H - -SO3 - -PO4 -2 -OH, -SH, polyamines, polyols or polyethers;

[0038] pH adjusters include hydroxides, ammonia, or organic amine compounds containing hydroxyl groups.

[0039] The above materials can be obtained through Figure 1 The preparation method shown in the steps outlined is as follows. The process includes:

[0040] Step 110: Mix 57-88 parts of water, 5-12 parts of conductive carbon material, 1-5 parts of black phosphorus, 5-25 parts of superdispersant and 0.1-1 parts of pH adjuster, and mechanically disperse to obtain a mixed slurry.

[0041] Specific methods of mechanical dispersion include dispersion using an emulsifier or a high-speed disperser; the dispersion speed is 2000-12000 rpm, and the dispersion time is 30-120 min.

[0042] Step 120: The mixed slurry is ultrasonically dispersed;

[0043] The duration of ultrasonic dispersion is 10-60 minutes.

[0044] Step 130: Disperse the mixed slurry using ball milling to obtain a coating slurry;

[0045] The diameter of the zirconium beads used for ball milling dispersion is 0.1-1 mm, and the ball milling dispersion time is 30-120 min.

[0046] Step 140: Apply the coating slurry to the surface of the positive electrode current collector aluminum foil and dry it to obtain a two-dimensional material modified lithium battery positive electrode current collector surface coating.

[0047] The coating method is one of the following: blade coating, spin coating, gravure coating, micro-gravure coating, or slot extrusion coating; the wet film thickness of the coating is 1-10 μm.

[0048] The drying method is hot air drying, with a drying temperature of 70-150℃ and a drying time of 15-30 minutes.

[0049] The two-dimensional material-modified lithium battery cathode current collector surface coating of the present invention can be used as a cathode in lithium batteries.

[0050] This coating increases the bonding force between coating materials by forming CP bonds between black phosphorus and conductive carbon materials. The two-dimensional layered structure of black phosphorus has stronger structural integrity, and its two-dimensional pleated channel structure forms a stable bond with small-sized conductive materials. The interpenetration of the layers improves the wettability of the coating surface and strengthens the bonding force with the cathode material. As a semiconductor material, black phosphorus itself has a certain degree of conductivity. During the use of lithium batteries, it interacts with lithium ions in the cathode material, causing black phosphorus to transform from a semiconductor to a conductor, further improving conductivity. The superdispersant in the coating material is a block copolymer acrylic acid with multiple anchoring groups, which can generate a strong affinity with the surface of nanoparticles, has excellent wetting, dispersion and stabilization effects, and acts as a binder in the system. During the drying process, the polymer chains firmly bind the components together, providing the coating with excellent stability.

[0051] Therefore, the two-dimensional material modified lithium battery cathode current collector surface coating is a cathode current collector surface coating with strong adhesion, high conductivity and good mechanical properties, which has a positive and beneficial effect on improving the cycle life of lithium batteries, increasing the energy density of lithium batteries and improving the rate performance of lithium batteries.

[0052] To better understand the technical solution of this invention, some specific embodiments are described below. However, the scope of protection of this invention is not limited thereto.

[0053] Example 1

[0054] This example provides a two-dimensional material-modified coating for the surface of a lithium-ion battery positive electrode current collector. The coating is formed by applying a conductive slurry to the surface of the positive electrode current collector aluminum foil. The mass ratio of each component in the conductive slurry is as follows: water: 67.7 parts; conductive carbon material: 10 parts; black phosphorus: 2 parts; superdispersant: 20 parts; pH adjuster: 0.3 parts. The conductive carbon material used is carbon black:graphite = 10:1; the black phosphorus particle size is 500 nm; the superdispersant is polyether-grafted modified block copolymer acrylic acid; and the pH adjuster is alkanolamine.

[0055] The specific preparation steps are as follows:

[0056] Step 1: Mix all the above components and disperse them using an emulsifier at high speed (7000 rpm) for 60 minutes.

[0057] Step 2: Disperse the slurry obtained in Step 1 using ultrasound for 30 minutes.

[0058] Step 3: Disperse the slurry obtained in Step 2 using ball milling to obtain the final slurry. The diameter of the zirconia beads used for ball milling is 0.5 mm, and the dispersion time is 30 min.

[0059] Step 4: Apply the final slurry to the surface of the positive current collector aluminum foil using a scraping method and dry it to obtain the desired coating thickness of 10µm.

[0060] Example 2

[0061] This example provides a two-dimensional material-modified coating for the surface of a lithium-ion battery positive electrode current collector. The coating is formed by applying a conductive slurry to the surface of the positive electrode current collector aluminum foil. The mass ratio of each component in the conductive slurry is as follows: water: 79.8 parts; conductive carbon material: 9 parts; black phosphorus: 1 part; superdispersant: 10 parts; pH adjuster: 0.2 parts. The conductive carbon material used is carbon black; the black phosphorus particle size is 500 nm; the superdispersant is polyether-grafted modified block copolymer acrylic acid; and the pH adjuster is alkanolamine.

[0062] The specific preparation steps are as follows:

[0063] Step 1: Mix all the above components and disperse them using an emulsifier at high speed (7000 rpm) for 60 minutes.

[0064] Step 2: Disperse the slurry obtained in Step 1 using ultrasound for 30 minutes.

[0065] Step 3: Disperse the slurry obtained in Step 2 using ball milling to obtain the final slurry. The diameter of the zirconia beads used for ball milling is 0.5 mm, and the dispersion time is 30 min.

[0066] Step 4: Apply the final slurry to the surface of the positive current collector aluminum foil using a scraping method and dry it to obtain the desired coating thickness of 10µm.

[0067] Example 3

[0068] This example provides a two-dimensional material-modified coating for the surface of a lithium-ion battery positive electrode current collector. The coating is formed by applying a conductive slurry to the surface of the positive electrode current collector aluminum foil. The composition of the conductive slurry is as follows: water: 67.7 parts; conductive carbon material: 10 parts; black phosphorus: 2 parts; superdispersant: 20 parts; pH adjuster: 0.3 parts. The conductive carbon material used is carbon black: CNT = 10:1; the black phosphorus particle size is 500 nm; the superdispersant is polyether-grafted modified block copolymer acrylic acid; and the pH adjuster is ammonia.

[0069] The specific preparation steps are as follows:

[0070] Step 1: Mix all the above components and disperse them using an emulsifier at high speed (8000 rpm) for 70 minutes.

[0071] Step 2: Disperse the slurry obtained in Step 1 using ultrasound for 30 minutes.

[0072] Step 3: Disperse the slurry obtained in Step 2 above using ball milling to obtain the final slurry. The diameter of the zirconia beads used for ball milling is 0.3 mm, and the dispersion time is 30 min.

[0073] Step 4: Apply the final slurry to the surface of the positive current collector aluminum foil using a blade coating method and dry it to obtain the coating with a thickness of 10 μm.

[0074] Comparative Example 1

[0075] This example provides a two-dimensional material modified surface coating for the positive electrode current collector of a lithium battery, which is basically the same as that in Example 1, except that black phosphorus is not added.

[0076] Comparative Example 2

[0077] This example provides a two-dimensional material modified surface coating for lithium battery cathode current collectors, which is basically the same as that in Example 1, except that black phosphorus is replaced with red phosphorus in equal amounts.

[0078] Comparative Example 3

[0079] Blank aluminum foil.

[0080] Lithium iron phosphate solid electrolyte, polyvinylidene fluoride, and conductive additive acetylene black were mixed evenly in a ratio of 6:2:1:1 to prepare a slurry. This slurry was then uniformly coated onto aluminum foil prepared in the comparative examples above using a doctor blade. After drying, a lithium iron phosphate positive electrode sheet was prepared. A coin-type CR2032 half-cell was fabricated using the lithium iron phosphate positive electrode sheet as the positive electrode and the lithium sheet as the negative electrode. The charging current was 1 mA, the charging cut-off voltage was ≥4.3 V, and the discharging cut-off voltage was ≤2.5 V. The electrical performance at room temperature was tested using a Blue Electric testing device, and the results are shown in Table 1.

[0081]

[0082] Table 1

[0083] The CR2032 coin cells were fabricated by coating lithium iron phosphate cathode slurry in the above embodiments and tested using Blue Electric testing equipment to obtain the long-cycle performance at room temperature, as shown in Table 2.

[0084]

[0085] Table 2

[0086] Based on the comparison of data in Tables 1 and 2, it can be seen that the battery with the coating of two-dimensional black phosphorus exhibits superior performance. Compared with the coating without black phosphorus, the specific capacity of the battery is significantly increased, and it also has a high capacity retention rate at different rates.

[0087] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-dimensional material-modified surface coating for a lithium battery positive electrode current collector, characterized in that, The two-dimensional material-modified lithium battery positive electrode current collector surface coating is formed by coating a conductive paste onto the surface of the positive electrode current collector; The conductive paste comprises, by weight ratio, 57-88 parts water, 5-12 parts conductive carbon material, 1-5 parts black phosphorus, 5-25 parts superdispersant, and 0.1-1 parts pH adjuster. The superdispersant is a block copolymer acrylic acid with multiple anchoring groups in its molecule, which has an affinity for the surfaces of the components in the conductive paste and binds the components together during the coating drying process. The anchoring groups include -NR2 and -NR3. + -COOH, -COO - -SO3 - -PO4 2- -OH, -SH, polyamines, polyols or polyethers; The conductive carbon material in the coating is bonded to the two-dimensional sheet-like black phosphorus through CP bonds; the black phosphorus has a two-dimensional pleated channel structure.

2. The two-dimensional material-modified lithium battery cathode current collector surface coating according to claim 1, characterized in that, The conductive carbon material includes at least one of carbon black, graphite, graphene, and carbon nanotubes. The black phosphorus is orthorhombic and has a particle size of 10-900 nm. The pH adjuster includes: hydroxides, ammonia, or organic amine compounds containing hydroxyl groups.

3. A method for preparing a two-dimensional material-modified surface coating for a lithium battery positive electrode current collector as described in claim 1 or 2, characterized in that, The preparation method includes: Mix 57-88 parts of water, 5-12 parts of conductive carbon material, 1-5 parts of black phosphorus, 5-25 parts of superdispersant and 0.1-1 parts of pH adjuster, and mechanically disperse to obtain a mixed slurry; the conductive carbon material is bonded to the two-dimensional sheet-like black phosphorus through CP bonds; the black phosphorus has a two-dimensional pleated channel structure. The mixed slurry was ultrasonically dispersed. The mixed slurry was dispersed using ball milling to obtain the coating slurry; A coating slurry is applied to the surface of the positive electrode current collector aluminum foil and dried to obtain a two-dimensional material-modified lithium battery positive electrode current collector surface coating. The superdispersant is a block copolymer acrylic acid with multiple anchoring groups in its molecule, which generates affinity with the surfaces of each component in the mixed slurry and binds the components together during the coating drying process. The anchoring groups include -NR2 and -NR3. + -COOH, -COO - -SO3 - -PO4 2- -OH, -SH, polyamines, polyols or polyethers.

4. The preparation method according to claim 3, characterized in that, The specific methods of mechanical dispersion include dispersion using an emulsifier or dispersion using a high-speed disperser; the dispersion speed is 2000-12000 rpm, and the dispersion time is 30-120 min.

5. The preparation method according to claim 3, characterized in that, The duration of ultrasonic dispersion is 10-60 minutes.

6. The preparation method according to claim 3, characterized in that, The zirconium beads used for ball milling dispersion have a diameter of 0.1-1 mm, and the ball milling dispersion time is 30-120 min.

7. The preparation method according to claim 3, characterized in that, The coating method is one of the following: blade coating, spin coating, gravure coating, micro-gravure coating, and slot extrusion coating; the wet film thickness of the coating is 1-10 μm.

8. The preparation method according to claim 3, characterized in that, The drying method is hot air drying, with a drying temperature of 70-150℃ and a drying time of 15-30 minutes.

9. A positive electrode comprising a surface coating of a two-dimensional material modified according to claim 1 or 2 for a lithium battery positive electrode current collector.

10. A lithium battery comprising a two-dimensional material modified surface coating for the positive electrode current collector of a lithium battery according to claim 1 or 2.

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