Porous copper foil-silicon carbon integrated negative pole piece as well as preparation method and application thereof

Abstract

The invention provides a porous copper foil-silicon carbon integrated negative pole piece as well as a preparation method and application thereof, and belongs to the technical field of lithium battery materials. The preparation method comprises the following steps: compounding a porous copper foil with a resin solution, and activating an obtained porous precursor by adopting an activating gas to obtain a porous copper-carbon composite framework precursor; and under the condition of protective gas, introducing silane gas, carrying out vapor deposition on the porous copper-carbon composite skeleton precursor, introducing carbon source gas, and carrying out carbon coating to obtain the porous copper foil-silicon carbon integrated negative electrode plate. According to the invention, the copper foil and the silicon-carbon negative electrode material are integrally combined, so that the silicon-carbon material and the copper foil current collector have stronger binding force, the silicon-carbon material can be prevented from layering and falling off in the circulation process, the battery has the characteristics of high capacity and super-long circulation, meanwhile, the battery preparation process flow is shortened, and the time cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and in particular to a porous copper foil-silicon carbon integrated negative electrode sheet and a preparation method and application thereof. Background Art

[0002] Lithium-ion secondary batteries are widely used in portable electronic products, electric vehicles, energy storage, etc. due to their high mass and volume energy density, long cycle and low self-discharge performance. However, the combination of traditional graphite and positive electrode is far from meeting market demand. Although the existing Si has a theoretical capacity of up to 4200mAh / g, its expansion is up to 300%, which affects the cycle performance and restricts market promotion and application.

[0003] At present, the expansion problem of Si negative electrode is mainly alleviated by coating carbon materials on the surface of silicon. However, the traditional coating method has the problem that the Si particle size is large and it is difficult to form a uniform carbon coating layer on the surface of silicon particles, and the volume expansion of silicon will still drive the rupture of the carbon layer, so that the carbon coating layer gradually separates and fails, and the expansion problem of silicon cannot be suppressed for a long time. In order to solve the bottleneck of the traditional coating method, Chinese patent CN115966684A uses porous carbon as a matrix, and obtains a silicon-carbon composite material with Si nanometer size <10nm and uniform distribution by silane deposition, but the porous carbon matrix used in this method has the problem of low strength of porous carbon skeleton during the circulation process; Chinese patent CN115863600A first carbon-coated metal compounds to obtain porous carbon matrix precursors, and deposited Si on the porous carbon matrix precursors by silane deposition to obtain silicon-carbon composite negative electrode materials, but some metal ions may react with electrolytes during the circulation process, affecting the long-term stability of the battery. In addition, the current production of silicon-carbon negative electrode sheets mainly involves mixing silicon-carbon with a conductive agent and a binder to form a slurry, which is then coated on copper foil. This method has the problem of a long process time, and the binder is prone to failure during the battery cycle, resulting in silicon-carbon shedding. Summary of the invention

[0004] The purpose of the present invention is to provide a porous copper foil-silicon carbon integrated negative electrode plate and its preparation method and application, so as to solve the problems of insufficient skeleton strength of the existing porous carbon matrix and easy detachment of the silicon carbon negative electrode from the copper foil during battery cycling. The porous copper foil-silicon carbon integrated negative electrode prepared by this method has the advantages of stable structure and high skeleton strength.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a porous copper foil-silicon carbon integrated negative electrode sheet, comprising the following steps:

[0007] Mixing the resin, the curing agent and the organic solvent to obtain a resin solution;

[0008] After compounding the porous copper foil with the resin solution, drying and curing are performed in sequence to obtain a porous precursor;

[0009] Activating the porous precursor with an activation gas to obtain a porous copper-carbon composite skeleton precursor;

[0010] Under protective gas conditions, silane gas is introduced to vapor-deposit the porous copper-carbon composite skeleton precursor, and then carbon source gas is introduced to perform carbon coating to obtain a porous copper foil-silicon-carbon integrated negative electrode sheet.

[0011] Preferably, the resin includes one or two of asphalt resin, phenolic resin, epoxy resin and furan resin, the curing agent includes one or two of hexamethylenetetramine, hydroxyethylethylenediamine and diethylenetriamine, the organic solvent includes ethanol or acetone, the mass fraction of the resin in the resin solution is 40-60%, and the mass of the curing agent is 5-15% of the mass of the resin.

[0012] Preferably, the compounding is carried out under static conditions, and the compounding time is 2 to 12 hours; the drying temperature is 30 to 100° C., and the drying time is 12 to 24 hours.

[0013] Preferably, the curing temperature is 120-200° C., the curing time is 2-6 hours, and the atmosphere is nitrogen or argon.

[0014] Preferably, the activation gas includes CO2 and / or water vapor, the activation temperature is 700-1100°C, the time is 1-12 hours, and the atmosphere is nitrogen or argon.

[0015] Preferably, the silane gas includes monosilane and / or disilane, the protective gas includes one or more of nitrogen, argon and helium, and the flow ratio of the silane gas to the protective gas is 1:1 to 10; the temperature of the vapor deposition is 500 to 1000°C, and the time is 1 to 12 hours.

[0016] Preferably, the carbon source gas includes one or more of methane, ethane, propane, acetylene and propyne, and the flow ratio of the carbon source gas to the protective gas is 1:1-10; the ratio of Si to carbon skeleton is 1:9-9:1; the temperature of the carbon coating is 500-1000°C, and the time is 1-12h.

[0017] The present invention provides a porous copper foil-silicon carbon integrated negative electrode sheet prepared by the preparation method described in the above technical solution.

[0018] Preferably, based on 100% of the total mass content of silicon and carbon, the silicon content is 10-90% and the carbon content is 10-90%.

[0019] The present invention provides the application of the porous copper foil-silicon carbon integrated negative electrode plate described in the above technical solution in a lithium battery.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention uses resin to directly generate porous carbon on the porous copper foil, forming a stable and high-strength support structure, which is conducive to building a stronger porous carbon skeleton and reducing the expansion of Si during the cycle.

[0022] (2) Porous copper foil has excellent conductivity and can form a continuous conductive network, effectively improving the conductivity of the negative electrode material, thereby improving the performance of high-rate charge and discharge.

[0023] (3) In the negative electrode sheet prepared by the present invention, the silicon-carbon material extends from the inside to the outside in the porous copper foil, which increases the contact area of ​​the silicon-carbon negative electrode material, has more lithium ion migration channels and a shorter migration path, thereby improving the rate performance.

[0024] (4) The present invention integrates copper foil and silicon-carbon negative electrode material, so that the silicon-carbon material and the copper foil current collector have stronger bonding force, which can prevent the silicon-carbon material from stratifying and falling off during the cycle process. It has the characteristics of high capacity and ultra-long cycle, and at the same time shortens the process flow of battery preparation and reduces time cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of the method for preparing the porous copper foil-silicon carbon integrated negative electrode plate. DETAILED DESCRIPTION

[0026] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0027] like Figure 1 As shown, the present invention provides a method for preparing a porous copper foil-silicon carbon integrated negative electrode sheet, comprising the following steps:

[0028] Mixing the resin, the curing agent and the organic solvent to obtain a resin solution;

[0029] After compounding the porous copper foil with the resin solution, drying and curing are performed in sequence to obtain a porous precursor;

[0030] Activating the porous precursor with an activation gas to obtain a porous copper-carbon composite skeleton precursor;

[0031] Under protective gas conditions, silane gas is introduced to vapor-deposit the porous copper-carbon composite skeleton precursor, and then carbon source gas is introduced to perform carbon coating to obtain a porous copper foil-silicon-carbon integrated negative electrode sheet.

[0032] The present invention mixes resin, curing agent and organic solvent to obtain resin solution.

[0033] In the present invention, the resin preferably includes one or two of asphalt resin, phenolic resin, epoxy resin and furan resin, and the curing agent preferably includes one or two of hexamethylenetetramine, hydroxyethylethylenediamine and diethylenetriamine. When the resin or curing agent is two or more of the above, the present invention has no special limitation on the ratio of different types of resins or curing agents, and any ratio is acceptable.

[0034] The present invention has no particular limitation on the specific models and specifications of different types of resins. The resins may be prepared by using corresponding commercially available resins known in the art or by methods known in the art.

[0035] In the present invention, the organic solvent preferably includes ethanol or acetone, the mass fraction of the resin in the resin solution is preferably 40-60%, more preferably 40-48%, and the mass of the curing agent is preferably 5-15% of the resin mass, more preferably 5-10%.

[0036] The present invention has no particular limitation on the mixing of the resin, curing agent and organic solvent, and they can be stirred and mixed uniformly according to methods well known in the art.

[0037] The resin in the present invention is conducive to forming a more solid porous carbon structure, which in turn helps to improve the stability of the silicon-carbon negative electrode material structure and ensure its cycle performance.

[0038] After obtaining the resin solution, the present invention compounds the porous copper foil with the resin solution, and then sequentially performs drying and curing to obtain a porous precursor.

[0039] The present invention has no particular limitation on the specification and source of the porous copper foil, and any commercially available porous copper foil known in the art may be used.

[0040] In the present invention, before use, the porous copper foil is preferably firstly ultrasonically cleaned with acetone, then ultrasonically cleaned with methanol, and then compounded with the resin solution.

[0041] The present invention has no special limitation on the usage ratio of the resin solution to the porous copper foil, as long as the resin solution completely immerses the copper foil.

[0042] In the present invention, the composite is preferably carried out under static conditions; the present invention preferably places the porous copper foil in a vacuum bag, injects a resin solution, evacuates the bag, takes out the copper foil after composite under static conditions, dries to remove the solvent, and then solidifies to obtain a porous precursor.

[0043] In the present invention, the compounding time is preferably 2 to 12 hours, more preferably 6 to 12 hours, and the temperature is preferably room temperature; the drying temperature is preferably 30 to 100°C, more preferably 30 to 60°C, and the time is preferably 12 to 24 hours, more preferably 16 to 24 hours; the drying method is preferably vacuum drying.

[0044] In the present invention, the curing temperature is preferably 120-200° C., more preferably 150-180° C., and further preferably 160° C., the curing time is preferably 2-6 hours, and more preferably 3-5 hours, and the atmosphere is preferably nitrogen or argon. During the curing process, the resin generates a cross-linked structure and simultaneously generates high molecular polymer characteristics.

[0045] A porous precursor is obtained or, in the present invention, the porous precursor is activated by using an activation gas to obtain a porous copper-carbon composite skeleton precursor.

[0046] In the present invention, the activation gas preferably includes CO2 and / or water vapor, the activation temperature is preferably 700-1100°C, more preferably 700-900°C, the time is preferably 1-12h, more preferably 1-5h, the flow rate is preferably 1-10L / min, more preferably 1-5L / min, and the atmosphere is preferably nitrogen or argon. The present invention forms a porous carbon skeleton through the activation process.

[0047] The present invention has no particular limitation on the heating rate for heating to the curing and activation temperature, which can be adjusted according to actual needs. In the embodiment of the present invention, the heating rate is specifically 5°C / min.

[0048] In the present invention, the silane gas preferably includes monosilane and / or disilane, the protective gas preferably includes one or more of nitrogen, argon and helium, the flow rate of the silane gas is preferably 1 to 8 L / min, more preferably 3 to 5 L / min; the flow rate ratio of the silane gas to the protective gas is preferably 1:1 to 10, more preferably 1:1 to 5; the temperature of the vapor deposition is preferably 500 to 1000°C, more preferably 650 to 800°C, and the time is preferably 1 to 12 hours, more preferably 1 to 6 hours. When the silane gas or protective gas is more than two of the above, the present invention has no special restrictions on the ratio of different types of gases, and any ratio is acceptable.

[0049] After completing the vapor deposition, the present invention introduces a carbon source gas under protective gas conditions. In the present invention, the carbon source gas preferably includes one or more of methane, ethane, propane, acetylene and propyne, and the flow rate of the carbon source gas is preferably 1 to 8 L / min, more preferably 3 to 5 L / min; the flow ratio of the carbon source gas to the protective gas is preferably 1:1 to 10, more preferably 1:1; the temperature of the carbon coating is preferably 500 to 1000°C, more preferably 650 to 800°C, and the time is preferably 1 to 12h, more preferably 1 to 6h. When the carbon source gas is more than the above two types, the present invention has no special limitation on the ratio of different types of gases, and any ratio is acceptable.

[0050] The present invention provides a porous copper foil-silicon carbon integrated negative electrode sheet prepared by the preparation method described in the above technical solution. In the porous copper foil-silicon carbon integrated negative electrode sheet of the present invention, the porous carbon skeleton is evenly distributed in the porous copper foil, nano-silicon is deposited in the pores of the carbon skeleton, and the surface of the nano-silicon is coated with a carbon layer.

[0051] In the present invention, based on 100% of the total mass content of silicon and carbon, the silicon content is preferably 10-90%, more preferably 44-53%, and the carbon content is preferably 10-90%, more preferably 47-56%.

[0052] The present invention provides the application of the porous copper foil-silicon carbon integrated negative electrode plate described in the above technical solution in a lithium battery.

[0053] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0054] Example 1

[0055] S1: Cut the copper foil into a shape of 3×15 cm and first ultrasonically clean it in acetone and then in methanol;

[0056] S2: Phenolic resin as raw material (10 g), hexamethylenetetramine as curing agent (0.5 g), and ethanol as solvent (14 g) were mixed under stirring to obtain a resin solution, wherein the mass ratio of phenolic resin, hexamethylenetetramine and ethanol was 20:1:28;

[0057] S3: Put the cut copper foil into a vacuum bag, add the resin solution prepared above, until the copper foil is completely immersed, and then seal the vacuum bag and evacuate it, and let it stand at room temperature for 12 hours;

[0058] S4: Take out the copper foil after standing and vacuum dry it at 30°C for 24h;

[0059] S5: The dried copper foil was heated to 160°C at a heating rate of 5°C / min in a N2 atmosphere, and maintained at this temperature for 3 hours for curing, and then heated to 700°C at a heating rate of 5°C / min, and water vapor was introduced at a flow rate of 1L / min for activation for 1 hour. After cooling in the furnace, a porous copper-carbon composite skeleton was obtained;

[0060] S6: Add the obtained porous copper-carbon composite skeleton into a rotary kiln, introduce disilane under nitrogen protection, wherein the disilane gas flow rate is 5 L / min, and the disilane gas flow rate: nitrogen flow rate = 1:1, the deposition temperature is 650°C, and the deposition time is 1 hour; after the deposition is completed, introduce propyne under nitrogen protection, wherein the propyne flow rate is 5 L / min, and the propyne flow rate: nitrogen flow rate = 1:1, and carbon coating is carried out at 650°C for 6 hours. After the carbon coating is completed, it is cooled with the furnace to obtain a porous copper foil-silicon carbon integrated negative electrode sheet, wherein, based on the total mass content of silicon and carbon as 100%, the silicon content is 53%, and the carbon content is 47%.

[0061] Example 2

[0062] The only difference from Example 1 is that the mass ratio of phenolic resin, hexamethylenetetramine and ethanol in S2 is 10:1:10.

[0063] In the prepared porous copper foil-silicon-carbon integrated negative electrode sheet, based on 100% of the total mass content of silicon and carbon, the silicon content is 50% and the carbon content is 50%.

[0064] Example 3

[0065] The only difference from Example 1 is that in S2, epoxy resin is used as raw material, diethylenetriamine is used as curing agent, and acetone is used as solvent.

[0066] In the prepared porous copper foil-silicon carbon integrated negative electrode sheet, based on 100% of the total mass content of silicon and carbon, the silicon content is 44% and the carbon content is 56%.

[0067] Example 4

[0068] The only difference from Example 1 is that in S5, CO2 is introduced for activation, and the activation time is 12 hours.

[0069] In the prepared porous copper foil-silicon-carbon integrated negative electrode sheet, based on 100% total mass content of silicon and carbon, the silicon content is 52% and the carbon content is 48%.

[0070] Comparative Example 1

[0071] Add a resin-based porous carbon material into a rotary kiln, introduce disilane under nitrogen protection, the disilane gas flow rate is 5 L / min, the disilane gas flow rate: nitrogen flow rate = 1:1, the deposition temperature is 650°C, and the deposition time is 1 hour; after the silane deposition is completed, introduce propyne under nitrogen protection, wherein the propyne flow rate is 5 L / min, the propyne flow rate: nitrogen flow rate = 1:1, and deposit at 650°C for 6 hours. After the deposition is completed, cool with the furnace to obtain a silicon-carbon negative electrode. Based on the total mass content of silicon and carbon as 100%, the silicon content is 50% and the carbon content is 50%.

[0072] The obtained silicon-carbon negative electrode was made into a negative electrode sheet with a mass ratio of silicon-carbon negative electrode: conductive carbon black: carbon nanotubes: binder LA132 = 94:1:1:4.

[0073] Comparative Example 2

[0074] A porous carbon material of coconut shell is added into a rotary kiln, and disilane is introduced under nitrogen protection, with a disilane gas flow rate of 5 L / min, disilane gas flow rate: nitrogen flow rate = 1:1, a deposition temperature of 650°C, and a deposition time of 1 hour; after the silane deposition is completed, propyne is introduced under nitrogen protection, with a propyne flow rate of 5 L / min, propyne flow rate: nitrogen flow rate = 1:1, and deposition is carried out at 650°C for 6 hours. After the deposition is completed, the material is cooled with the furnace to obtain a silicon-carbon negative electrode. Based on the total mass content of silicon and carbon as 100%, the silicon content is 49% and the carbon content is 51%.

[0075] The obtained silicon-carbon negative electrode was made into a negative electrode sheet with a mass ratio of silicon-carbon negative electrode: conductive carbon black: carbon nanotubes: binder: LA132 = 94:1:1:4.

[0076] Performance Testing

[0077] 1) The negative electrode sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were subjected to electrical performance tests, and the negative electrode sheets were made into CR2032 button batteries. The test conditions were as follows: electrolyte: JN-JW-2249; counter electrode: pure lithium sheet;

[0078] Charge and discharge regime: 1) Stand for 10 min; 2) Constant current discharge (0.1C, 0.005V); 3) Stand for 10 min; 4) Rate discharge (0.05C, 0.005V); 5) Stand for 10 min; 6) Rate discharge (0.02C, 0.005V);

[0079] 7) Let stand for 10 min; 8) Charge at a rate of 0.1C, 1.5V. The results are shown in Table 1.

[0080] Table 1 Electrical performance data of materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2

[0081]

[0082] It can be seen from Table 1 that, compared with Comparative Examples 1 to 2, the negative electrode sheets prepared in Examples 1 to 4 have more excellent electrical properties.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a porous copper foil-silicon carbon integrated negative electrode sheet, characterized in that: The following steps are involved: Mixing the resin, the curing agent and the organic solvent to obtain a resin solution; After compounding the porous copper foil with the resin solution, drying and curing are performed in sequence to obtain a porous precursor; Activating the porous precursor with an activation gas to obtain a porous copper-carbon composite skeleton precursor; Under protective gas conditions, silane gas is introduced to vapor-deposit the porous copper-carbon composite skeleton precursor, and then carbon source gas is introduced to perform carbon coating to obtain a porous copper foil-silicon-carbon integrated negative electrode sheet.

2. The preparation method according to claim 1, characterized in that: The resin includes one or two of asphalt resin, phenolic resin, epoxy resin and furan resin, the curing agent includes one or two of hexamethylenetetramine, hydroxyethylethylenediamine and diethylenetriamine, the organic solvent includes ethanol or acetone, the mass fraction of the resin in the resin solution is 40-60%, and the mass of the curing agent is 5-15% of the mass of the resin.

3. The preparation method according to claim 1, characterized in that: The compounding is carried out under static conditions, and the compounding time is 2 to 12 hours; the drying temperature is 30 to 100° C., and the drying time is 12 to 24 hours.

4. The preparation method according to claim 1, characterized in that: The curing temperature is 120-200° C., the curing time is 2-6 hours, and the atmosphere is nitrogen or argon.

5. The preparation method according to claim 1, characterized in that: The activation gas includes CO2 and / or water vapor, the activation temperature is 700-1100°C, the time is 1-12 hours, and the atmosphere is nitrogen or argon.

6. The preparation method according to claim 1, characterized in that: The silane gas includes monosilane and / or disilane, the protective gas includes one or more of nitrogen, argon and helium, and the flow ratio of the silane gas to the protective gas is 1:1-10; the temperature of the vapor deposition is 500-1000°C, and the time is 1-12h.

7. The preparation method according to claim 1, characterized in that: The carbon source gas includes one or more of methane, ethane, propane, acetylene and propyne, and the flow ratio of the carbon source gas to the protective gas is 1:1-10; the temperature of the carbon coating is 500-1000°C, and the time is 1-12h.

8. The porous copper foil-silicon carbon integrated negative electrode sheet prepared by the preparation method according to any one of claims 1 to 7.

9. The porous copper foil-silicon carbon integrated negative electrode sheet according to claim 8, characterized in that: Based on 100% of the total mass content of silicon and carbon, the silicon content is 10-90% and the carbon content is 10-90%.

10. Use of the porous copper foil-silicon carbon integrated negative electrode sheet according to claim 8 or 9 in a lithium battery.

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