Carbon-coated foamed aluminum, preparation method thereof and positive plate of lithium ion power battery

Abstract

The invention discloses carbon-coated foamed aluminum, a preparation method thereof and a lithium ion power battery positive plate, and relates to the technical field of power battery materials. The three-dimensional through-hole foamed aluminum is composed of three-dimensional through-hole foamed aluminum and a conductive layer wrapping the surface of the three-dimensional through-hole foamed aluminum, the conductive layer comprises a conductive agent and a binder, and the conductive agent is selected from one or a combination of at least two of acetylene black, Super P, graphene and CNT. The surface of the three-dimensional through-hole foamed aluminum is pretreated; coating the surface with a coating liquid containing a conductive agent, and finally drying to form a conductive layer on the surface of the three-dimensional through-hole foamed aluminum. The composite material can be applied to a positive plate of a lithium ion power battery, and the cycling stability and consistency of the battery can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery materials, and in particular to a carbon-coated foamed aluminum and a preparation method thereof, and a positive electrode sheet for a lithium-ion power battery. Background Art

[0002] Carbon coating technology on the surface of current collector is a process commonly used to improve the surface properties of metal materials. It forms a carbon film on the metal surface to enhance its wear resistance, corrosion resistance and conductivity. The metal surface after carbon coating forms a dense carbon layer with high wear resistance, which can effectively reduce friction and wear. The coating layer can also provide a certain chemical stability and has good resistance to corrosive media such as oxidation, acid and alkali. Because carbon has good conductivity, the metal surface after carbon coating can improve conductivity and have lower impedance to current transmission.

[0003] Aluminum foil is a common material used for current collectors, but it also has some disadvantages. Aluminum foil is relatively sealed, has a low through-porosity, and has poor air permeability, which means that the liquid accumulated in it may be difficult to evaporate or volatilize. Aluminum foil is relatively fragile and easily damaged, scratched or torn. Once damaged, its effect of collecting liquid will be greatly reduced; the melting point of aluminum foil is relatively low, and its high temperature resistance is limited. Using aluminum foil in a high temperature environment may cause deformation, melting or burning, and thus cannot effectively collect liquid; the surface of aluminum foil is smooth and does not absorb water, which makes it difficult to clean. During use, if liquid adheres to the aluminum foil, it is troublesome to clean; aluminum foil is easily affected by oxidation and reacts with oxygen in the air to form an aluminum oxide layer. Such an oxide layer will reduce the conductive properties of the aluminum foil, making the interface contact with the active material poor, increasing internal resistance, and causing energy loss. As the number of charge and discharge times increases, the active material is easy to fall off, affecting the battery performance; aluminum foil is relatively heavy and thick, which will increase the overall weight and volume of the battery. For some applications, such as mobile devices and electric vehicles, weight and volume need to be as light and small as possible. Although aluminum foil has certain conductive properties, its conductivity is relatively weak compared to other materials (such as copper). This means that in some high-power and high-current applications, aluminum foil may not provide sufficient current transmission capabilities.

[0004] Chinese patent document CN109786757A "Carbon-coated aluminum foam composite and its preparation method, current collector and filter material" (published on May 1, 2019) discloses a carbon-coated aluminum foam composite, which forms a uniform and dense carbon layer on the surface of the aluminum wire skeleton after the aluminum foam is treated with a gas containing a carbon source under high temperature conditions; then a weak oxidant is introduced and treated at high temperature to form pores in the carbon layer, thereby obtaining a composite in which a microporous carbon layer is coated on the surface of the aluminum foam. The microporous carbon layer can increase conductivity and improve the interface contact effect, and also has the function of storing energy and fixing active substances, thereby improving the stability of electrochemical energy storage devices. However, this method has a complicated process, and in the process of depositing the carbon source, the thickness of the carbon coating layer cannot be accurately controlled; in addition, the introduction of a weak oxidant is easy to react with metal aluminum, resulting in a certain degree of corrosion of the aluminum foam. Summary of the invention

[0005] In order to solve the problems of low porosity of existing current collectors, large internal resistance in contact with positive electrode active materials, easy shedding and corrosion of active materials, the present invention proposes a carbon-coated foamed aluminum and a preparation method thereof, and a positive electrode sheet for a lithium-ion power battery.

[0006] The technical solution of the present invention is as follows: A carbon-coated aluminum foam consists of a three-dimensional through-hole aluminum foam and a conductive layer coated on the surface of the three-dimensional through-hole aluminum foam, wherein the conductive layer comprises a conductive agent and a binder, and the conductive agent is selected from one or a combination of at least two of acetylene black, Super P, graphene, and CNT.

[0007] Preferably, the thickness of the three-dimensional through-hole aluminum foam is 5 μm to 200 μm, the pore size of the three-dimensional through hole is within 1 mm, the pore density is 100 PPI to 110 PPI, and the width of the aluminum wire skeleton of the three-dimensional aluminum foam is 30 μm to 100 μm.

[0008] Preferably, the thickness of the conductive layer is 0.1 μm to 3 μm.

[0009] Preferably, the mass ratio of the conductive agent to the binder is 1-20:1-10.

[0010] Preferably, the binder is selected from one or a combination of at least two of PTFE, CMC, and PVDF.

[0011] The present invention also provides a method for preparing the carbon-coated aluminum foam as described above, comprising: Pre-treating the surface of the three-dimensional through-hole aluminum foam; Apply a coating liquid containing a conductive agent on the surface. Finally, a drying process is performed to form a conductive layer on the surface of the three-dimensional through-hole aluminum foam.

[0012] Preferably, the preprocessing is specifically: Clean with acetone and anhydrous ethanol respectively to remove the oily components on the surface; Then use dilute hydrochloric acid to clean and remove the surface oxide layer.

[0013] Preferably, the coating liquid contains 1% to 20% conductive agent, 1% to 10% binder, and the remainder is solvent water or N-methylpyrrolidone.

[0014] The present invention also provides a lithium-ion power battery positive electrode plate, comprising the carbon-coated aluminum foam.

[0015] A method for preparing the above-mentioned positive electrode sheet of the lithium-ion power battery is specifically: coating the positive electrode slurry on the surface and pores of the carbon-coated foamed aluminum, and then drying it to obtain the positive electrode sheet of the lithium-ion power battery.

[0016] Compared with the prior art, the specific beneficial effects of the present invention are: The present invention proposes a method for preparing carbon-coated foamed aluminum. Compared with the existing process technology, the method has a simple preparation path and does not rely on complex equipment, which is beneficial to reducing energy consumption and process costs and is easy to realize industrial large-scale production. The prepared lithium ion positive electrode can effectively fix the active substance and ensure good electrochemical activity while also ensuring good electrical conductivity, thereby making the material exhibit high cycle stability, high energy density and good rate characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a scanning electron microscope image of the carbon-coated aluminum foam prepared in Example 1; Figure 2 The positive electrode sheet of the lithium-ion power battery prepared in Example 2; Figure 3 Schematic diagram of the cycle performance test results of lithium-ion batteries prepared in different embodiments. DETAILED DESCRIPTION

[0018] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the specification of the present invention. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as a limitation to the present invention.

[0019] Example 1. (1) The through-hole aluminum foam with a pore density of 110 PPI and a thickness of 100 μm was degreased with acetone and anhydrous ethanol respectively; then the surface oxide layer was washed away with 0.1 mol / L dilute hydrochloric acid; (2) Coating a coating liquid containing a conductive agent on the surface of the through-hole foam aluminum, wherein the conductive agent is 5%, the binder PTFE is 3%, and the balance is solvent water. The conductive agent is acetylene black; (3) Drying the through-hole aluminum foam coated in step (2) to obtain a carbon-coated aluminum foam containing a conductive layer.

[0020] The obtained carbon-coated aluminum foam has a scanning electron microscope image. Figure 1 , coating the positive electrode slurry on the surface and pores of the carbon-coated aluminum foam, and then drying to obtain a positive electrode sheet for a lithium-ion power battery. Figure 3 As shown in a, when lithium manganese iron phosphate is used as the positive electrode active material, the assembled lithium-ion battery has a -1 After 200 cycles at a current of 120 mAh g -1 discharge capacity.

[0021] Example 2. (1) The through-hole aluminum foam with a pore density of 100 PPI and a thickness of 100 μm was degreased with acetone and anhydrous ethanol respectively; then the surface oxide layer was washed away with 0.1 mol / L dilute hydrochloric acid; (2) Coating a coating liquid containing a conductive agent on the surface of the through-hole foam aluminum, with the conductive agent being 5%, the binder being CMC being 5%, and the balance being solvent water, and the conductive agent being Super P; (3) Drying the through-hole aluminum foam coated in step (2) to obtain a carbon-coated aluminum foam containing a conductive layer.

[0022] The positive electrode slurry is coated on the surface and pores of the carbon-coated aluminum foam, and then dried to obtain a positive electrode sheet for a lithium-ion power battery. Figure 2 As shown. Tests have shown that Figure 3 As shown in b, when lithium manganese iron phosphate is used as the positive electrode active material, the assembled lithium-ion battery has a -1 After 200 cycles at a current of 115 mAh g -1 discharge capacity.

[0023] Example 3. (1) The through-hole aluminum foam with a pore density of 110 PPI and a thickness of 100 μm was degreased with acetone and anhydrous ethanol respectively; then the surface oxide layer was washed away with 0.1 mol / L dilute hydrochloric acid; (2) coating a coating liquid containing a conductive agent on the surface of the through-hole aluminum foam, wherein the conductive agent is 5%, the binder is PVDF 3%, and the balance is solvent N-methylpyrrolidone, and the conductive agent is CNT; (3) Drying the through-hole aluminum foam coated in step (2) to obtain a carbon-coated aluminum foam containing a conductive layer.

[0024] The positive electrode slurry is coated on the surface and pores of the carbon-coated aluminum foam, and then dried to obtain a positive electrode sheet for a lithium-ion power battery. Figure 3 c shows that when lithium manganese iron phosphate is used as the positive electrode active material, the assembled lithium-ion battery has a -1 After 200 cycles at a current of 1.5 , there is still 118 mAh g -1 discharge capacity.

[0025] Example 4. (1) The through-hole aluminum foam with a pore density of 100 PPI and a thickness of 100 μm was degreased with acetone and anhydrous ethanol respectively; then the surface oxide layer was washed away with 0.1 mol / L dilute hydrochloric acid; (2) coating a coating liquid containing a conductive agent on the surface of the through-hole aluminum foam, wherein the conductive agent is 5%, the binder PVDF is 3%, and the balance is the solvent N-methylpyrrolidone, and the conductive agent is a mixture of CNT and graphene; (3) Drying the through-hole aluminum foam coated in step (2) to obtain a carbon-coated aluminum foam containing a conductive layer.

[0026] The positive electrode slurry is coated on the surface and pores of the carbon-coated aluminum foam, and then dried to obtain a positive electrode sheet for a lithium-ion power battery. Figure 3 As shown in d, when lithium manganese iron phosphate is used as the positive electrode active material, the assembled lithium-ion battery has a -1 After 200 cycles at a current of 1.5 , there is still 119 mAh g -1 discharge capacity.

[0027] In summary, the lithium-ion battery electrode prepared by the preparation method of the carbon-coated aluminum foam proposed in the present invention can ensure good electrochemical activity and good electrical conductivity, thereby making the material exhibit high cycle stability, high energy density and good rate characteristics.

[0028] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A carbon-coated aluminum foam, characterized in that: It is composed of a three-dimensional through-hole aluminum foam and a conductive layer coated on the surface of the three-dimensional through-hole aluminum foam. The conductive layer includes a conductive agent and a binder. The conductive agent is selected from one or a combination of at least two of acetylene black, Super P, graphene, and CNT.

2. The carbon-coated aluminum foam according to claim 1, characterized in that: The thickness of the three-dimensional through-hole aluminum foam is 5 μm to 200 μm, the aperture of the three-dimensional through hole is within 1 mm, the pore density is 100 PPI to 110 PPI, and the width of the aluminum wire skeleton of the three-dimensional aluminum foam is 30 μm to 100 μm.

3. The carbon-coated aluminum foam according to claim 1, characterized in that: The thickness of the conductive layer is 0.1 μm to 3 μm.

4. The carbon-coated aluminum foam according to claim 1, characterized in that: The mass ratio of the conductive agent to the binder is 1~20:1~10.

5. The carbon-coated aluminum foam according to claim 1, characterized in that: The binder is selected from one of PTFE, CMC, and PVDF, or a combination of at least two of them.

6. A method for preparing the carbon-coated aluminum foam according to any one of claims 1 to 5, characterized in that: The steps include: Pre-treating the surface of the three-dimensional through-hole aluminum foam; A coating liquid containing a conductive agent is applied to the surface. Finally, a drying process is performed to form a conductive layer on the surface of the three-dimensional through-hole aluminum foam.

7. The method for preparing carbon-coated aluminum foam according to claim 6, characterized in that: The pre-processing is specifically as follows: Clean with acetone and anhydrous ethanol respectively to remove the oily components on the surface; Then use dilute hydrochloric acid to clean and remove the surface oxide layer.

8. The method for preparing carbon-coated aluminum foam according to claim 6, characterized in that: The coating liquid contains 1% to 20% of the conductive agent, 1% to 10% of the binder, and the remainder is solvent water or N-methylpyrrolidone.

9. A positive electrode sheet for a lithium-ion power battery, characterized in that: It comprises the carbon-coated foamed aluminum as described in any one of claims 1 to 5.

10. A method for preparing a positive electrode sheet for a lithium-ion power battery as claimed in claim 9, characterized in that: The positive electrode slurry is coated on the surface and pores of the carbon-coated aluminum foam, and then dried to obtain a positive electrode sheet for a lithium-ion power battery.

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