Porous copper-graphene composite current collector for lithium battery and preparation method of porous copper-graphene composite current collector

Abstract

The invention discloses a porous copper-graphene composite current collector for a lithium battery, and also discloses a preparation method of the composite current collector, and the preparation method comprises the following steps: preparing an electroplating copper electrolyte, adding graphene into the electroplating copper electrolyte, and uniformly dispersing the graphene to obtain an electroplating copper-graphene electrolyte; placing a copper foil in the electrocoppering-graphene electrolyte for electroplating treatment to obtain a Cu-Gr foil of which the surface is uniformly coated with a copper-graphene composite layer; the Cu-Gr foil is placed in an electrogalvanizing electrolyte for electrogalvanizing treatment, on the basis of the copper-graphene composite layer, a zinc layer is coated, and the Cu-Gr / Zn foil of a double-layer structure is obtained; carrying out solution treatment on the Cu-Gr / Zn foil to obtain a porous copper precursor; and carrying out dealloying treatment on the porous copper precursor, and dissolving zinc in the porous copper precursor to obtain the porous copper-graphene composite current collector. The composite current collector has a cross-scale synergistic distribution pore structure, and the binding force between the graphene and the copper substrate is strong.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery negative electrode current collectors, and relates to a porous copper-graphene composite current collector for lithium batteries. The present invention also relates to a preparation method of the composite current collector. Background Art

[0002] The negative electrode current collector of lithium-ion batteries (LIBs) is typically made of pure copper foil (8-20μm thick), which carries the active material and provides an electron conduction path. However, traditional copper foil exposes three core problems when supporting high-capacity negative electrode materials: dendrite growth, volume expansion, and low specific surface area and porosity.

[0003] To overcome the above problems, researchers proposed graphene-modified copper foil current collector, using the ultra-high conductivity of graphene (10 6 S / m), mechanical strength (130GPa) and chemical stability, thereby improving the overall performance of the current collector.

[0004] Some studies have used physical coating or chemical vapor deposition (CVD) to coat copper foil with graphene to improve conductivity and mechanical strength. Chinese patent application number CN108172838A, published on June 15, 2018, discloses a method for preparing a graphene-coated copper foil current collector. By ultrasonically dispersing graphene, a highly reduced graphene coating is formed on the copper foil surface. This coating can reduce battery internal resistance, improve adhesion of active materials, and mitigate lithium dendrite formation. Chinese patent application number CN107732249A, published on February 23, 2018, discloses a method for preparing a copper foil-graphene composite negative electrode current collector. Graphene is directly coated onto the copper foil surface using a continuous chemical vapor deposition method, forming an integrated composite material. This improves the bonding strength between the current collector and the active material, ensuring a tighter bond. However, due to the inherent limitations of the two-dimensional structure, it cannot effectively accommodate the volume expansion of the electrode material.

[0005] In recent years, the research focus has gradually shifted to the construction and design of three-dimensional porous structures. Three-dimensional porous structures have extremely high specific surface areas, providing more active sites for the storage and transmission of lithium ions. The three-dimensional porous copper current collector adapts to the volume changes of the electrode material during the charge and discharge process through its porous structure, thereby alleviating stress concentration and maintaining the integrity of the electrode structure. In addition, three-dimensional porous copper has good electronic conductivity, and its unique structure can form an efficient electron transmission network, reducing the resistance to electron transmission. A Chinese patent with a publication date of April 9, 2021 and publication number CN112635772B discloses a method for preparing porous copper foil for lithium batteries. A non-porous copper foil substrate is used, and an alloy copper foil layer is covered by electrodeposition and dealloyed to form a porous copper foil layer with a porosity of 20-30%. This can reduce the volume share in the battery while increasing the specific surface area to meet the requirements of lightweight lithium-ion batteries. A Chinese patent with a publication date of March 9, 2018 and publication number CN107785586A discloses a method for preparing a three-dimensional porous copper / graphene composite current collector for the negative electrode of a secondary metal lithium battery. Nanoporous copper is prepared by dealloying, and graphene is formed under catalysis by CVD to prepare a three-dimensional porous copper-graphene composite current collector with a continuous through-structure. During operation, a stable solid electrolyte interface is formed and lithium dendrites are suppressed.

[0006] In summary, while some progress has been made in the design of three-dimensional porous structures for graphene-modified copper foil current collectors, existing methods typically only form pore structures of a single scale. Furthermore, conventional processes often introduce graphene via surface coating or chemical vapor deposition (CVD), resulting in weak interfacial bonding with the copper substrate and prone to delamination during cycling. Furthermore, existing preparation methods rely on complex and costly processes (such as CVD or 3D printing), further hindering their large-scale application. Summary of the Invention

[0007] The purpose of the present invention is to provide a porous copper-graphene composite current collector for lithium batteries, which has a cross-scale coordinated distribution of pore structure and strong bonding between graphene and copper matrix.

[0008] Another object of the present invention is to provide a method for preparing the composite current collector, which solves the problems of complex porous structure construction process and low process controllability in existing methods. The technical solution adopted by the present invention is: The technical solution adopted by the present invention is a method for preparing a porous copper-graphene composite current collector for lithium batteries, which is specifically implemented according to the following steps: Step 1: preparing a copper electroplating electrolyte, adding graphene thereto, and stirring to uniformly disperse the graphene to obtain a copper electroplating-graphene electrolyte; Step 2, pre-treating the copper foil; Step 3: Placing the copper foil in a copper-graphene electroplating electrolyte for electroplating to obtain a Cu-Gr foil with a surface uniformly coated with a copper-graphene composite layer; Step 4: placing the Cu-Gr foil in an electrogalvanizing electrolyte for electrogalvanizing treatment, and then coating the copper-graphene composite layer with a zinc layer to obtain a Cu-Gr / Zn foil with a double-layer structure; Step 5, performing a solution treatment on the Cu-Gr / Zn foil to obtain a porous copper precursor; Step 6: Dealloying the porous copper precursor to dissolve the zinc therein to obtain a porous copper-graphene composite current collector.

[0009] The present invention is also characterized in that: In step 1, the components and concentrations of the copper electroplating electrolyte are: 60-100 g / L copper sulfate, 50-150 g / L sulfuric acid, and 30-100 mg / L sodium chloride.

[0010] In step 1, the amount of graphene added is 1~2g / L.

[0011] Step 2 is as follows: Soak the copper foil in a 0.5~1.5 mol / L hydrochloric acid solution for 30 seconds to remove surface impurities and oxide layer.

[0012] In step 3, the electroplating current is 0.1-0.4A, and the electroplating time is 10-30min.

[0013] In step 4, the components and concentrations of the electrogalvanizing electrolyte are: 6-12 g / L zinc oxide, 100-150 g / L sodium hydroxide.

[0014] In step 4, the electroplating current is 0.1-0.4A, and the electroplating time is 10-30min.

[0015] In the solution treatment of step 5, the heating rate is 5-10°C / min, the solution temperature is 200-400°C, and the holding time is 2-4h.

[0016] The dealloying treatment in step 6 is specifically as follows: immersing the porous copper precursor in 0.5-1.5 mol / L sulfuric acid for 24-36 hours.

[0017] Another technical solution adopted by the present invention is a porous copper-graphene composite current collector for lithium batteries, which is prepared by the above method. It uses a porous copper foil as a substrate, and irregularly shaped doped graphene is distributed on the surface of the copper foil, and part of the graphene is embedded in the copper foil substrate.

[0018] The beneficial effects of the present invention are: (1) The method of the present invention adopts a synergistic strategy of electroplating-dealloying, so that graphene is coated on the surface of the copper foil and partially embedded in the interior of the copper matrix. The graphene and the copper matrix are mechanically engaged to enhance the interfacial bonding strength, thereby constructing a porous copper-graphene composite current collector with a three-dimensional through-structure. (2) The method of the present invention constructs a copper-graphene composite current collector with a cross-scale coordinated pore structure through the mechanism of metal solid solution and selective corrosion. This method breaks through the technical bottleneck of single pore size in the preparation of traditional porous materials and realizes the cross-scale coordinated distribution of nanoscale pores (<100nm) and submicron pores (200-500nm). Nanopores provide channels for rapid lithium ion transmission, and submicron pores can accommodate active materials to prevent volume expansion; (3) The method of the present invention uses conventional electroplating equipment and does not require CVD / 3D printing, which shortens the process flow and significantly reduces the cost of raw materials compared to vapor-deposited graphene copper foil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM image of the composite current collector prepared in Example 2 of the present invention; Figure 2 This is a pore size characterization diagram of the composite current collector prepared in Example 2 of the present invention; Figure 3 This is a pore size characterization diagram of the current collector prepared in Comparative Example 2 of the present invention; Figure 4 The initial discharge curves of the current collectors prepared in Example 2 and Comparative Examples 1-2 of the present invention; Figure 5 Figure 2 is a diagram of the nucleation overpotential of lithium in the current collectors prepared in Example 2 of the present invention and Comparative Examples 1-2; Figure 6 Graphs showing the coulombic efficiencies of the current collectors prepared in Example 2 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] The method for preparing a porous copper-graphene composite current collector for a lithium battery of the present invention is specifically implemented according to the following steps: Step 1: preparing a copper electroplating electrolyte, adding graphene thereto, and stirring to uniformly disperse the graphene to obtain a copper electroplating-graphene electrolyte; The composition and concentration of the copper electroplating electrolyte are: 60-100g / L copper sulfate, 50-150g / L sulfuric acid, and 30-100mg / L sodium chloride. In addition, the added amount of graphene is 1-2g / L.

[0022] Step 2: Soak the copper foil in a 0.5-1.5 mol / L hydrochloric acid solution for 30 seconds to remove surface impurities and oxide layer. Step 3: Place the copper foil obtained in step 2 in the copper-graphene electroplating electrolyte obtained in step 1 for electroplating, and wash with deionized water after electroplating to obtain a copper foil with a surface uniformly covered with a copper-graphene composite layer, i.e., Cu-Gr foil; wherein the electroplating current is 0.1-0.4A and the electroplating time is 10-30min.

[0023] Step 4: Placing the copper foil obtained in step 3 in a zinc electroplating electrolyte for zinc electroplating. A zinc layer is then coated on top of the copper-graphene layer on the surface of the copper foil to obtain a copper foil with a double-layer structure, i.e., Cu-Gr / Zn foil. The zinc electroplating electrolyte comprises the following components and concentrations: 6-12 g / L zinc oxide and 100-150 g / L sodium hydroxide. The electroplating current is 0.1-0.4 A, and the electroplating time is 10-30 minutes.

[0024] Step 5: placing the Cu-Gr / Zn foil obtained in step 4 in a tube furnace for solution treatment at a heating rate of 5-10°C / min, a solution temperature of 200-400°C, and a holding time of 2-4h to obtain a porous copper precursor; Step 6: Immerse the porous copper precursor obtained in step 5 in 0.5-1.5 mol / L sulfuric acid for dealloying for 24-36 hours to dissolve the zinc therein to form a three-dimensional porous copper-graphene structure, thereby obtaining a porous copper-graphene composite current collector.

[0025] The purity of the copper foil used in the embodiment of the present invention is ≥99.99%, and the battery separator used is a common commercial separator - Celgard 2325.

[0026] Example 1: Step 1, prepare copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60~70℃ and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain copper electroplating electrolyte, wherein the copper sulfate concentration is 80g / L, the sulfuric acid concentration is 60g / L, and the sodium chloride concentration is 50mg / L; then add graphene (1g / L) and magnetically stir (600rpm, 90min) until uniformly dispersed to obtain copper electroplating-graphene electrolyte.

[0027] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 1 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0028] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 30 minutes, and the electroplating current is 0.1A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0029] Step 4: Prepare the electrogalvanizing electrolyte: Add 30g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 2g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters to 10min for the electroplating time and 0.1A for the electroplating current to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0030] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 300° C. for 2 hours to obtain a porous copper precursor.

[0031] Step 6: Immerse the precursor in 1M H2SO4 for dealloying for 24 hours to selectively dissolve Zn, obtain a three-dimensional porous copper-graphene structure, and obtain a composite current collector.

[0032] Example 2: Step 1, prepare copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60~70℃ and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain copper electroplating electrolyte, wherein the copper sulfate concentration is 80g / L, the sulfuric acid concentration is 60g / L, and the sodium chloride concentration is 50mg / L; then add graphene (1g / L) and magnetically stir (600rpm, 90min) until uniformly dispersed to obtain copper electroplating-graphene electrolyte.

[0033] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 1 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0034] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 30 minutes, and the electroplating current is 0.2A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0035] Step 4: Prepare the electrogalvanizing electrolyte: Add 30g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 2g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters to 10min for the electroplating time and 0.1A for the electroplating current to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0036] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 300° C. for 2 hours to obtain a porous copper precursor.

[0037] Step 6: Immerse the precursor in 1M H2SO4 for dealloying for 24 hours to selectively dissolve Zn, obtain a three-dimensional porous copper-graphene structure, and obtain a composite current collector.

[0038] Example 3: Step 1, prepare copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60~70℃ and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain copper electroplating electrolyte, wherein the copper sulfate concentration is 80g / L, the sulfuric acid concentration is 60g / L, and the sodium chloride concentration is 50mg / L; then add graphene (1g / L) and magnetically stir (600rpm, 90min) until uniformly dispersed to obtain copper electroplating-graphene electrolyte.

[0039] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 1 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0040] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 30 minutes, and the electroplating current is 0.1A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0041] Step 4: Prepare the electrogalvanizing electrolyte: Add 30g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 2g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters to 10min for the electroplating time and 0.2A for the electroplating current to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0042] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 300° C. for 2 hours to obtain a porous copper precursor.

[0043] Step 6: Immerse the precursor in 1M H2SO4 for dealloying for 24 hours to selectively dissolve Zn, obtain a three-dimensional porous copper-graphene structure, and obtain a composite current collector.

[0044] Example 4: Step 1, prepare copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60~70℃ and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain copper electroplating electrolyte, wherein the copper sulfate concentration is 80g / L, the sulfuric acid concentration is 60g / L, and the sodium chloride concentration is 50mg / L; then add graphene (1g / L) and magnetically stir (600rpm, 90min) until uniformly dispersed to obtain copper electroplating-graphene electrolyte.

[0045] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 1 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0046] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 30 minutes, and the electroplating current is 0.2A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0047] Step 4: Prepare the electrogalvanizing electrolyte: Add 30g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 2g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters to 10min for the electroplating time and 0.2A for the electroplating current to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0048] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 300° C. for 2 hours to obtain a porous copper precursor.

[0049] Step 6: Immerse the precursor in 1M H2SO4 for dealloying for 24 hours to selectively dissolve Zn, obtain a three-dimensional porous copper-graphene structure, and obtain a composite current collector.

[0050] Example 5: Step 1, prepare a copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60-70°C and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain a copper electroplating electrolyte, wherein the copper sulfate concentration is 100 g / L, the sulfuric acid concentration is 50 g / L, and the sodium chloride concentration is 80 mg / L; then add graphene (2 g / L) and magnetically stir (600 rpm, 90 min) until uniformly dispersed to obtain a copper electroplating-graphene electrolyte.

[0051] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 1.5 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0052] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 10 minutes, and the electroplating current is 0.4A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0053] Step 4: Prepare the electrogalvanizing electrolyte: Add 25g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 3g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters to 20min for the electroplating time and 0.1A for the electroplating current to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0054] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 200° C. for 4 hours to obtain a porous copper precursor.

[0055] Step 6: Immerse the precursor in 0.5M H2SO4 for dealloying for 36 hours to selectively dissolve Zn, obtain a three-dimensional porous copper-graphene structure, and obtain a composite current collector.

[0056] Example 6: Step 1, prepare copper electroplating electrolyte: dissolve copper sulfate in deionized water at 60~70℃ and stir until completely dissolved; slowly add concentrated sulfuric acid in a ventilated environment; then add NaCl to supplement chloride ions to obtain copper electroplating electrolyte, wherein the copper sulfate concentration is 60g / L, the sulfuric acid concentration is 150g / L, and the sodium chloride concentration is 30mg / L; then add graphene (2g / L) and magnetically stir (600rpm, 90min) until uniformly dispersed to obtain copper electroplating-graphene electrolyte.

[0057] Step 2: Cut the copper foil into rectangular slices of the same size, immerse them in 0.5 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0058] Step 3: Immerse the pretreated copper foil in the copper-graphene electroplating electrolyte, connect the positive electrode to the copper plate, and the negative electrode to the copper foil. Set the electroplating parameters, the electroplating time is 20 minutes, and the electroplating current is 0.2A to obtain a copper foil (Cu-Gr) with a surface uniformly coated with a copper-graphene composite layer. After electroplating, rinse with deionized water.

[0059] Step 4: Prepare the electrogalvanizing electrolyte: Add 35g of sodium hydroxide to 250mL of deionized water and stir until completely dissolved. Add 1.5g of zinc oxide and stir until completely dissolved to obtain the electrogalvanizing electrolyte. Transfer the Cu-Gr foil to the electrogalvanizing electrolyte, with the positive electrode connected to the zinc plate and the negative electrode connected to the Cu-Gr foil. Set the electroplating parameters, the electroplating time is 10min, and the electroplating current is 0.4A, to form a Cu-Gr / Zn double-layer structure. After electroplating, rinse with deionized water, then soak in anhydrous ethanol for 60s, and blow dry to remove surface moisture.

[0060] Step 5: Place the Cu-Gr / Zn foil in a tube furnace and heat it to 400° C. for 3 hours to obtain a porous copper precursor.

[0061] In step 6, the precursor is immersed in 1.5M H2SO4 for dealloying for 24 hours to selectively dissolve Zn to obtain a three-dimensional porous copper-graphene structure and a composite current collector.

[0062] Comparative Example 1: In this comparative example, only the copper foil was pretreated, and the treatment method was the same as in Example 2, namely: The copper foil was cut into rectangular slices of the same size and immersed in 1 mol / L dilute hydrochloric acid for 30 s to remove the surface oxide layer. The slices were then rinsed with deionized water and dried.

[0063] Comparative Example 2: This comparative example is basically the same as Example 2, except that graphene is not used to modify the surface of the copper foil, that is, step 1 and step 3 are not performed. The specific steps of this comparative example are: Step 1: Cut the copper foil into rectangular slices of the same size, immerse them in 1 mol / L dilute hydrochloric acid for 30 seconds to remove the surface oxide layer, and then rinse with deionized water and dry them.

[0064] Step 2, prepare an electro-zinc plating electrolyte: add 30g of sodium hydroxide to 250mL of deionized water, stir until completely dissolved, add 2g of zinc oxide, stir until completely dissolved, and obtain an electro-zinc plating solution.

[0065] Place the copper foil pretreated in step 1 in the zinc electroplating electrolyte, with the positive electrode connected to the zinc plate and the negative electrode to the copper foil. Set the electroplating parameters to 10 minutes and a current of 0.1A to form a Cu-Zn double-layer structure. After electroplating, rinse with deionized water, soak in anhydrous ethanol for 60 seconds, and blow dry to remove surface moisture.

[0066] Step 3: Place the Cu-Zn foil in a tube furnace and heat it to 300° C. for 2 hours to obtain a porous copper precursor.

[0067] Step 4: Immerse the precursor in 1M H2SO4 for dealloying for 24 hours to selectively dissolve Zn to obtain a three-dimensional porous copper structure and a porous copper current collector.

[0068] The composite current collector prepared in Example 2 was tested by scanning electron microscopy. The results are as follows: Figure 1 As shown, it can be seen that the substrate is a porous copper foil, and silvery-white doped graphene is distributed on the surface of the copper foil. The graphene has an irregular shape, and some areas are obviously covered or interspersed in the porous copper foil structure.

[0069] The pore size of the current collectors prepared in Example 2 and Comparative Example 2 was characterized. The results are as follows: Figure 2 and Figure 3 As shown, it can be seen that the average pore size of the current collector in Comparative Example 2 is 0.78 μm, and the average pore size of the current collector in Example 2 is 0.49 μm. This is because the porous copper-graphene composite current collector prepared by the method of the present invention has not only macropores formed after the dealloying treatment, but also micropores and mesopores existing on the graphene surface, constructing a pore structure with cross-scale coordinated distribution.

[0070] The copper foils prepared in Example 2, Comparative Example 1 and Comparative Example 2 were prepared into half-cells: The lithium sheet was used as the counter electrode and the three copper foils were used as the working electrodes to assemble a CR2032 button cell. The electrolyte used was: solvent DMC:EC:EMC = 1:1:1, solute was 1M LiPF6, and the total amount of electrolyte used for each button cell was 40μL. At a current density of 1mA / cm 2 , surface capacity is 1mAh / cm 2 Metal lithium was deposited under the conditions of , and the charge-discharge cycle performance test was carried out. The results are as follows Figure 4-Figure 6 shown.

[0071] Figure 4Figure 1 is the initial discharge curve. Initially, the voltage curves for the three copper foils are nearly identical, indicating similar growth overpotentials. However, the latter half of the curves show significant differences, indicating different nucleation overpotentials. This suggests that the introduction of graphene in Example 2 provides abundant active sites within the three-dimensional porous structure, allowing lithium ions to more easily form small nuclei on the current collector surface rather than clustering, thus reducing the formation of lithium dendrites.

[0072] Figure 5 is the nucleation overpotential of lithium in the three copper foils. It can be seen that the porous copper with graphene introduced in Example 2 has the lowest nucleation overpotential, indicating that the porous copper-graphene composite material can undergo deposition reaction for lithium adsorption only at a lower additional voltage, and its performance is significantly better than that of the copper foil in Comparative Example 1 that has only been pretreated and the copper foil in Comparative Example 2 that has not been coated with graphene.

[0073] Figure 6 The figure shows the coulombic efficiency of three copper foils. The coulombic efficiency of the copper foil in comparative example 1 begins to drop significantly after 10 cycles, and decays to below 80% after 30 cycles. The coulombic efficiency of the copper foils in comparative example 2 and example 2 remains basically the same during the first 20 cycles, but after 20 cycles, the coulombic efficiency of the copper foil in comparative example 2 also begins to drop sharply, while the coulombic efficiency of the copper foil in example 2 remains at 97% after 30 cycles.

Claims

1. A method for preparing a porous copper-graphene composite current collector for a lithium battery, characterized in that: Please follow the steps below to implement: Step 1: preparing a copper electroplating electrolyte, adding graphene thereto, and stirring to uniformly disperse the graphene to obtain a copper electroplating-graphene electrolyte; Step 2, pre-treating the copper foil; Step 3: Placing the copper foil in a copper-graphene electroplating electrolyte for electroplating to obtain a Cu-Gr foil with a surface uniformly coated with a copper-graphene composite layer; Step 4: placing the Cu-Gr foil in an electrogalvanizing electrolyte for electrogalvanizing treatment, and then coating the copper-graphene composite layer with a zinc layer to obtain a Cu-Gr / Zn foil with a double-layer structure; Step 5, performing a solution treatment on the Cu-Gr / Zn foil to obtain a porous copper precursor; Step 6: Dealloying the porous copper precursor to dissolve the zinc therein to obtain a porous copper-graphene composite current collector.

2. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In step 1, the components and concentrations of the copper electroplating electrolyte are: 60-100 g / L copper sulfate, 50-150 g / L sulfuric acid, and 30-100 mg / L sodium chloride.

3. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In step 1, the amount of graphene added is 1-2 g / L.

4. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: Step 2 is as follows: Soak the copper foil in a 0.5~1.5 mol / L hydrochloric acid solution for 30 seconds to remove surface impurities and oxide layer.

5. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In step 3, the electroplating current is 0.1-0.4A, and the electroplating time is 10-30min.

6. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In step 4, the components and concentrations of the electrogalvanizing electrolyte are: 6-12 g / L zinc oxide and 100-150 g / L sodium hydroxide.

7. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In step 4, the electroplating current is 0.1-0.4A, and the electroplating time is 10-30min.

8. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: In the solution treatment of step 5, the heating rate is 5-10°C / min, the solution temperature is 200-400°C, and the holding time is 2-4h.

9. The method for preparing a porous copper-graphene composite current collector for a lithium battery according to claim 1, wherein: The dealloying treatment in step 6 is specifically as follows: immersing the porous copper precursor in 0.5-1.5 mol / L sulfuric acid for 24-36 hours.

10. A porous copper-graphene composite current collector for a lithium battery, characterized in that: It is prepared by the method described in any one of claims 1 to 9, and uses a porous copper foil as a substrate. Irregularly shaped doped graphene is distributed on the surface of the copper foil, and part of the graphene is embedded in the copper foil substrate.

Images