A foam aluminum inner filling carbon composite current collector and a preparation method and application thereof

Abstract

The application discloses a kind of foam aluminum inner filling carbon composite current collector and its preparation method and application, belong to composite current collector and its preparation technical field.The application solves the problem that the existing foam aluminum positive electrode current collector still needs to be improved in the conductive performance.The application fills in the three-dimensional through hole of foam aluminum after sodium chloride is used as template agent and is blended with polyacrylonitrile, and after stage heat treatment, using water to dissolve sodium chloride, constructs porous carbon structure in the three-dimensional through hole of foam aluminum, and the composite current collector obtained combines the three-dimensional porous structure of foam aluminum and the high conductivity of porous carbon, significantly improves the mechanical strength of material, enhances the structural stability of current collector, while the continuous porous carbon structure effectively reduces the contact resistance of the current collector material and electrode material, improves the conductivity.And the abundant pore structure of the current collector also effectively improves the volume strain of the current collector during charging and discharging, improves the cycle stability and safety of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of composite current collector of foamed aluminum filled with carbon and its preparation method and application, belong to composite current collector and its preparation technical field. BACKGROUND

[0002] Aluminum-based materials are widely used as current collector materials due to their excellent electrical conductivity and lightweight properties. Traditional commercial aluminum-based current collector materials mainly include aluminum foil, carbon-coated aluminum foil and foamed aluminum. However, these materials have certain limitations in performance, especially in high energy density and high power density applications.

[0003] As the most basic current collector material, aluminum foil has good electrical conductivity and cost-effectiveness. However, its smooth surface limits the contact area with electrode materials, and during the charging and discharging process of the battery, the aluminum foil cannot effectively buffer the volume change, leading to a decrease in battery performance.

[0004] Carbon-coated aluminum foil is prepared by coating a layer of carbon material on the surface of aluminum foil, which improves the electrical conductivity of the current collector and the adhesion with electrode materials, reduces the internal resistance of the battery, and improves the rate performance and cycle stability of the battery. However, the preparation process of carbon-coated aluminum foil is relatively complex, and the uniformity and stability of the carbon layer are still technical challenges.

[0005] Foamed aluminum provides a larger specific surface area and better electrochemical performance due to its three-dimensional porous structure, but its porosity is large, its mechanical strength is low, and it is easy to form an oxide film in air, which leads to poor contact with electrode materials and high resistance, which is not conducive to improving the power density of the device, and its electrical conductivity still needs to be improved. SUMMARY

[0006] To solve the problem of improving the electrical conductivity of existing foamed aluminum positive electrode current collector, the present application provides a composite current collector of foamed aluminum filled with carbon and its preparation method and application.

[0007] The technical solution of the present application is as follows:

[0008] One of the objectives of the present application is to provide a preparation method of a composite current collector of foamed aluminum filled with carbon, which comprises the following steps:

[0009] (1) Mix sodium chloride and polyacrylonitrile, and then perform ball milling treatment to obtain a mixed powder with uniform mixing and fine particles;

[0010] (2) Place foamed aluminum with three-dimensional through holes in a graphite mold, fill the mixed powder, and cover the graphite mold cover with threads and exhaust holes;

[0011] (3) Put the graphite mold into a tube furnace, introduce flowing protective gas, perform two-stage heat preservation treatment, and then naturally cool to room temperature to obtain a foamed aluminum / carbon composite.

[0012] (4) using water to dissolve sodium chloride in the foamed aluminum / carbon composite to obtain a porous integrated composite current collector.

[0013] Further limited, the mass ratio of sodium chloride to polyacrylonitrile in (1) is 1:(1-1000).

[0014] Further limited, the particle size of the mixed powder obtained in (1) is 0.1-100 microns.

[0015] Further limited, the protective gas in (3) is argon.

[0016] Further limited, the first holding zone of the two-stage holding in (3) is 320-400℃, and the time is 2 hours.

[0017] Further limited, the second holding zone of the two-stage holding in (3) is 600-650℃, and the time is 3 hours.

[0018] Further limited, the heating rate from the first holding zone to the second holding zone of the two-stage holding in (3) is 2-10℃ / min.

[0019] The second object of the present application is to provide a composite current collector prepared by the above method.

[0020] Further limited, the composite current collector is composed of foamed aluminum and a porous carbon structure filled in the three-dimensional through holes of the foamed aluminum.

[0021] The third object of the present application is to provide an application of the above composite current collector, specifically for preparing a positive electrode sheet of a lithium ion battery, a lithium-sulfur battery or a sodium ion battery.

[0022] The present application has the following advantages:

[0023] In the present application, sodium chloride is used as a template agent, which is blended with polyacrylonitrile and filled in the three-dimensional through holes of foamed aluminum, and then a stage heat treatment is performed, and sodium chloride is dissolved in water, and a porous carbon structure is constructed in the three-dimensional through holes of foamed aluminum, and a composite current collector is obtained, which combines the three-dimensional porous structure of foamed aluminum and the high conductivity of porous carbon, significantly improves the mechanical strength of the material, enhances the structural stability of the current collector, and the continuous porous carbon structure effectively reduces the contact resistance between the current collector material and the electrode material, improves the conductivity. And the abundant pore structure of the current collector also effectively improves the volume strain of the current collector during the charging and discharging process, improves the cycle stability and safety of the battery.

[0024] In summary, the composite current collector prepared by the present application has higher mechanical strength, lower contact resistance and better electrochemical performance than the existing commercial aluminum-based current collector materials, and has significant advantages in improving battery performance and safety, and is expected to play an important role in high energy density and high power density battery technology.

[0025] In addition, the present application uses sodium chloride as a template agent, and can stably and at low cost prepare a composite current collector with rich pore structure and high conductivity, and can also control the pore structure according to the filling amount and particle size of sodium chloride. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM images (different magnifications) of the composite current collector prepared for Example 1;

[0027] Figure 2 Cycle performance graph of the lithium ion battery assembled for the positive electrode prepared for Example 1 and Comparative Example 1;

[0028] Figure 3 Cycle performance graph of the lithium-sulfur battery assembled for the positive electrode prepared for Example 2, Comparative Example 2 and Comparative Example 3;

[0029] Figure 4 Comparison graph of the resistivity of the positive electrode sheet prepared for Example 2, Comparative Example 2 and Comparative Example 3. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0031] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0032] Example 1

[0033] The method for preparing the foam aluminum / carbon composite porous integrated current collector in this example is as follows:

[0034] (1) 100 g of sodium chloride and 200 g of polyacrylonitrile (polyacrylonitrile molecular weight 25000-80000) were weighed and added to a ball mill for ball milling, and the specific ball milling power was 1 KW, and the ball milling time was 1 h, to obtain a mixed powder of sodium chloride / polyacrylonitrile with uniform mixing and refined particles, and the particle size was 20 μm.

[0035] (2) Put the three-dimensional through-hole aluminum foam with a size of 10 cm x 10 cm x 1 mm (purchased from Fuersun Electronic Material Co., Ltd., model PPI-90) into a graphite mold, and uniformly fill the above obtained sodium chloride / polyacrylonitrile mixed powder (specifically fill 1 g), and cover the graphite mold cover with threads and exhaust holes.

[0036] (3) Put the filled and tightly covered graphite mold into a tube furnace, pass argon as a protective gas, first heat to 325°C for 2h, then heat to 650°C at a heating rate of 2°C / min and keep for 3h, and then cool to room temperature.

[0037] (4) The foam aluminum / carbon composite obtained after cooling is soaked in water for 1h, and the sodium chloride is dissolved and removed to obtain a foam aluminum / carbon composite porous integrated current collector, which is then dried in a 60°C air drying oven for standby.

[0038] The method for preparing a positive electrode sheet using the above foam aluminum / carbon composite porous integrated current collector is as follows:

[0039] Step one, mix the positive active material LiMnFePO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 93.5:3:3.5 in an N-methylpyrrolidone solution to obtain a positive electrode material slurry;

[0040] Step two, coat the positive electrode material slurry prepared in step one on the foam aluminum / carbon composite porous integrated current collector prepared in Example 1 after cutting and welding the aluminum tabs, and after oscillation until the slurry is completely filled, dry it in an oven at 100°C for 12h to obtain a positive electrode sheet.

[0041] The above prepared positive electrode sheet is assembled with a metal lithium negative electrode and a lithium ion secondary electrolyte (LB-275) to form a lithium ion battery.

[0042] Comparative Example 1

[0043] The method for preparing a current collector in this comparative example is as follows:

[0044] (1) Put the three-dimensional through-hole aluminum foam with a size of 10 cm x 10 cm x 1 mm (purchased from Fuersun Electronic Material Co., Ltd., model PPI-90) into a graphite mold, and cover the graphite mold cover with threads and exhaust holes.

[0045] (2) Put the filled and tightly covered graphite mold into a tube furnace, pass argon as a protective gas, first heat to 325°C for 2h, then heat to 650°C at a heating rate of 2°C / min and keep for 3h, and then cool to room temperature.

[0046] The method for preparing a positive electrode sheet using the above current collector in this comparative example is as follows:

[0047] Step one, mix the positive active material LiMnFePO4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 93.5:3:3.5 in N-methyl pyrrolidone solution to obtain a positive material slurry;

[0048] Step two, coat the positive material slurry prepared in step one on the current collector of the comparative example 1 after cutting and welding the aluminum tab, and dry in a 100℃ oven for 12h after oscillation until the slurry is completely filled, to obtain a positive electrode sheet.

[0049] The lithium ion battery is assembled by using the positive electrode sheet prepared above, a metal lithium negative electrode, and a lithium ion secondary electrolyte (LB-275).

[0050] Example 2

[0051] The method for preparing the foam aluminum / carbon composite porous integrated current collector in this example is as follows:

[0052] (1) Take 100g of sodium chloride and 1000g of polyacrylonitrile, and add them to a ball mill for ball milling. The specific ball milling power is 1KW, and the ball milling time is 1h. The sodium chloride / polyacrylonitrile mixed powder obtained is uniformly mixed and the particle size is refined to 10μm.

[0053] (2) Put a three-dimensional through-hole foam aluminum with a size of 10cm×10cm×1mm (purchased from Fuersun Electronic Material Co., Ltd., model PPI-90) into a graphite mold, and uniformly fill the above obtained sodium chloride / polyacrylonitrile mixed powder (specifically 1g) into the graphite mold. Cover the graphite mold cover with threads and exhaust holes.

[0054] (3) Put the filled and tightly covered graphite mold into a tube furnace, and pass argon as a protective gas. First, heat to 330℃ and keep for 2h, then heat to 650℃ at a heating rate of 5℃ / min and keep for 3h, and then cool to room temperature.

[0055] (4) Soak the foam aluminum / carbon composite obtained after cooling in water for 1h, and then remove the sodium chloride by dissolution to obtain a foam aluminum / carbon composite porous integrated current collector. Then, dry in a 60℃ air drying oven, and reserve for use.

[0056] The method for preparing the positive electrode sheet by using the above foam aluminum / carbon composite porous integrated current collector in this example is as follows:

[0057] Step one, mix the positive active material S8 / carbon composite material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 93.5:3:3.5 in N-methyl pyrrolidone solution to obtain a positive material slurry;

[0058] Step two, the positive material slurry prepared in step one was coated on the foam aluminum / carbon composite porous integrated current collector prepared in example 2 after cutting and welding with aluminum tabs, and after oscillation until the slurry was completely filled, it was dried in an oven at 100°C for 12h to obtain a positive electrode sheet.

[0059] In this example, the above-prepared positive electrode sheet, metal lithium negative electrode and lithium-sulfur battery secondary electrolyte (1MLiTFSI / DOL-DME (v / v = 1:1)) were used to assemble a lithium-sulfur battery.

[0060] Comparative Example 2

[0061] The method for preparing the current collector in this comparative example is as follows:

[0062] (1) A three-dimensional through-hole foam aluminum with a size of 10cm x 10cm x 1mm (purchased from Fuersun Electronic Materials Co., Ltd., model PPI-90) was placed in a graphite mold, and a graphite mold cover with threads and exhaust holes was covered.

[0063] (2) The filled and tightly covered graphite mold was placed in a tube furnace, argon was introduced as a protective gas, first heated to 330°C for 2h, then heated to 650°C at a rate of 5°C / min and kept for 3h, then cooled to room temperature to obtain a current collector, which was ready for use.

[0064] The method for preparing the positive electrode sheet using the above current collector in this comparative example is as follows:

[0065] Step one, the positive active material S8 / carbon composite material, conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) were mixed in N-methyl pyrrolidone solution at a mass ratio of 93.5:3:3.5 to obtain a positive electrode material slurry;

[0066] Step two, the positive electrode material slurry prepared in step one was coated on the foam aluminum / carbon composite porous integrated current collector prepared in comparative example 2 after cutting and welding with aluminum tabs, and after oscillation until the slurry was completely filled, it was dried in an oven at 100°C for 12h to obtain a positive electrode sheet.

[0067] In this example, the above-prepared positive electrode sheet, metal lithium negative electrode and lithium-sulfur battery secondary electrolyte (LS-001) were used to assemble a lithium-sulfur battery.

[0068] Comparative Example 3

[0069] The method for preparing the current collector in this comparative example is as follows:

[0070] (1) A carbon-coated aluminum foil with a size of 10cm x 10cm x 1mm was placed in a graphite mold, and a graphite mold cover with threads and exhaust holes was covered.

[0071] (2) Put the graphite mold filled and tightly covered into a tube furnace, pass in argon as protective gas, first heat to 350℃ for 2h, then heat to 655℃ at a heating rate of 5℃ / min and keep for 3h, then cool to room temperature to obtain the current collector, ready for use.

[0072] The method for preparing the positive electrode sheet of the present comparative example using the above current collector is as follows:

[0073] Step one, mix the positive active material S8 / carbon composite material, conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 93.5:3:3.5 in N-methyl pyrrolidone solution to obtain positive electrode material slurry.

[0074] Step two, coat the positive electrode material slurry prepared in step one on the foam aluminum / carbon composite porous integrated current collector prepared in comparative example 2 after cutting and welding aluminum tabs, and after oscillation until the slurry is completely filled, dry in an oven at 100℃ for 12h to obtain a positive electrode sheet.

[0075] The lithium-sulfur battery of the present example is assembled using the above prepared positive electrode sheet, metal lithium negative electrode and lithium-sulfur battery secondary electrolyte (LS-001).

[0076] Example 3

[0077] The method for preparing the foam aluminum / carbon composite porous integrated current collector of the present example is as follows:

[0078] (1) Take 100g of sodium chloride and 500g of polyacrylonitrile, add them to a ball mill for ball milling, the specific ball milling power is 1KW, the ball milling time is 1h, to obtain a mixed powder of sodium chloride / polyacrylonitrile with uniform mixing and fine particles, the particle size is 20μm.

[0079] (2) Put the three-dimensional through-hole foam aluminum with a size of 10cm×10cm×1mm (purchased from Fuersun Electronic Material Co., Ltd., model PPI-90) into a graphite mold, uniformly fill the above obtained sodium chloride / polyacrylonitrile mixed powder (specifically 1g), and cover the graphite mold cover with threads and exhaust holes.

[0080] (3) Put the graphite mold filled and tightly covered into a tube furnace, pass in argon as protective gas, first heat to 350℃ for 2h, then heat to 655℃ at a heating rate of 5℃ / min and keep for 3h, then cool to room temperature.

[0081] (4) After cooling, the foam aluminum / carbon composite obtained is soaked in water for 60min, after dissolving and removing sodium chloride, a foam aluminum / carbon composite porous integrated current collector is obtained, and then dried in a 60℃ air drying oven, ready for use.

[0082] The method for preparing the positive plate by using the above-mentioned foam aluminum / carbon composite porous integrated current collector is as follows:

[0083] Step one, the positive active material Na3V2(PO4)3, the conductive agent acetylene black, the C45 type carbon black conductive agent, and the binder polyvinylidene fluoride (PVDF) are mixed in N-methyl pyrrolidone solution according to the mass ratio of 93.5:1.5:1.5:3.5 to obtain a positive material slurry;

[0084] Step two, the positive material slurry prepared in step one is coated on the foam aluminum / carbon composite current collector prepared in example 3 after cutting and welding the aluminum tab, and after oscillation until the slurry is completely filled, drying at 100°C for 12h to obtain a positive plate.

[0085] In this embodiment, the above-mentioned prepared positive plate is assembled with a metal sodium negative electrode and a sodium ion secondary electrolyte (NP-005) to form a sodium ion battery.

[0086] Effect example

[0087] (1) The micro-morphology of the composite current collector prepared in example 1 is characterized, and the results are shown in Figure 1 . As can be seen from Figure 1 a, the polyacrylonitrile carbon material uniformly fills in the three-dimensional network structure of the foam aluminum after removing the sodium chloride template, Figure 1 b further shows that the particle size of the carbon material is about 50nm, and the pore distribution is uniform, which provides space for the uniform filling of the subsequent active material.

[0088] (2) The cycle performance of the batteries prepared in examples 1 and 2 and comparative examples 1-3 is tested and compared, and the results are shown in Figure 2 and 3 . As can be seen from Figure 2 , the initial capacity of the battery assembled in example 1 is 110mAh g -1 , and after 1000 cycles at a current density of 5C, the discharge capacity is still 58mAh g -1 , while the initial capacity of comparative example 1 is 85mAh g -1 , and after 1000 cycles at a current density of 5C, the capacity decays to 39mAh g -1 . Therefore, the composite current collector prepared in example 1 has a better discharge capacity retention rate. As can be seen from Figure 3 , when the foam aluminum / carbon composite current collector prepared in example 2 is used for the positive electrode of a lithium-sulfur battery, the initial discharge capacity is 1001mAh g -1 at a current density of 0.2C, and after 200 cycles, the discharge capacity is maintained at 578mAh g -1The initial discharge capacity of Comparative Example 2 and Comparative Example 3 is 789 mAh g -1 and 553 mAh g -1 The discharge capacity after 200 cycles is 555 mAh g -1 and 350 mAh g -1 It can be seen that the composite current collector prepared in Example 2 can stimulate the high activity of the positive electrode material of the lithium-sulfur battery, and provide higher discharge capacity.

[0089] (3) The resistivity of the positive electrode sheet prepared in Example 2 and Comparative Example 2 and Comparative Example 3 was characterized, and the comparison results are shown in FIG. 3. Figure 4 As can be seen from the figure, the resistivity of the foam positive electrode sheet prepared in Example 2 is 46 Ω·μm, and the resistivity of the positive electrode sheet of Comparative Example 2 and the positive electrode sheet of Comparative Example 3 is 58 Ω·μm and 86 Ω·μm, respectively. It can be seen that the positive electrode sheet prepared in Example 2 has smaller resistivity, which is beneficial to the rate discharge performance of the electrode sheet, and at the same time reduces the energy loss due to its own resistance.

[0090] In summary, the composite current collector provided by the present application can significantly improve the discharge capacity and cycle life of the battery when used in lithium ion or sodium ion batteries, and effectively improves the rate performance of the electrode.

[0091] The above only describes the preferred embodiments of the present application, and those skilled in the art can make appropriate changes and modifications to the above embodiments, therefore, the present application is not limited to the above specific embodiments, and some modifications and changes of the present application should fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a composite current collector, characterized in that, include: (1) Sodium chloride and polyacrylonitrile were mixed and then ball-milled to obtain a uniformly mixed powder with fine particles. (2) Place the aluminum foam with three-dimensional through holes into a graphite mold, fill it with mixed powder, and cover it with a graphite mold cover with threads and vent holes. (3) The graphite mold is placed in a tube furnace, a flowing protective gas is introduced, and after two-stage heat preservation treatment, it is naturally cooled to room temperature to obtain aluminum foam / carbon composite. (4) Sodium chloride in the aluminum / carbon foam composite is removed by water dissolution to obtain a porous integrated composite current collector.

2. The preparation method according to claim 1, characterized in that, (1) The mass ratio of sodium chloride to polyacrylonitrile is 1:(1~1000).

3. The preparation method according to claim 1, characterized in that, (1) The particle size of the mixed powder obtained is 0.1 to 100 μm.

4. The preparation method according to claim 1, characterized in that, (3) The protective gas is argon.

5. The preparation method according to claim 1, characterized in that, (3) The first insulation zone of the two-stage insulation is 320-400℃ and the time is 2h.

6. The preparation method according to claim 1, characterized in that, (3) The second insulation zone of the two-stage insulation is 600-650℃ and the time is 3h.

7. The preparation method according to claim 1, characterized in that, (3) The heating rate from the first insulation zone to the second insulation zone in the two-stage insulation process is 2 to 10℃ / min.

8. A composite current collector prepared by the method according to any one of claims 1 to 7.

9. The composite current collector according to claim 8, characterized in that, The composite current collector consists of aluminum foam and a porous carbon structure filled within the three-dimensional pores of the aluminum foam.

10. An application of the composite current collector as described in claim 8, characterized in that, A positive electrode sheet used to prepare lithium-ion batteries, lithium-sulfur batteries, or sodium-ion batteries.

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