Composite three-dimensional current collector, metal anode and metal secondary battery prepared by chemical plating

Abstract

The present invention discloses a composite three-dimensional current collector, a metal negative electrode and a metal secondary battery prepared based on chemical plating, and belongs to the technical field of metal secondary batteries. The composite three-dimensional current collector includes a non-metallic three-dimensional skeleton matrix and a metal coating uniformly distributed on the surface of the matrix by chemical plating. When the metal battery is working, the affinity between metals is used to induce metals such as Mg, Li, Na, Ca and Zn to be uniformly electrodeposited and stripped on the surface of the composite three-dimensional current collector, and the three-dimensional porous structure of the matrix provides a buffer space for metal deposition, so that metal ions are rapidly and uniformly electrodeposited, which can enhance the stability of the electrode interface and reduce dendrite growth, reduce the metal electrodeposition overpotential, and extend the service life of the metal negative electrode. The composite three-dimensional current collector prepared based on chemical plating of the present invention solves the problem of uneven growth of metal negative electrodes and is an effective way to commercialize metal secondary batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal secondary batteries, and specifically relates to a non-metal skeleton composite three-dimensional current collector prepared based on chemical plating, and a corresponding metal negative electrode and a metal secondary battery. Background Art

[0002] In recent years, people have been demanding high-energy-density secondary batteries for applications in large-scale equipment such as power-driven vehicles and energy storage systems. Metal secondary batteries based on metal negative electrodes such as Mg, Li, Zn, Na, K, and Ca have high energy density and are a high-performance energy storage battery system that has attracted much attention.

[0003] However, metal negative electrodes still face many challenges in their practical application, and uncontrollable dendrite growth is one of them. On the one hand, dendrites formed during the metal deposition process can easily pierce the diaphragm and contact the positive electrode, causing battery short circuits or even fires; on the other hand, dendrites may also react with the electrolyte, resulting in reduced coulombic efficiency and limited cycle life. In the research of metal secondary batteries, thicker glass fiber diaphragms are usually used to reduce the risk of short circuits during the cycle, but the weight of the thick diaphragm and the limitation on the E / C ratio are very unfavorable for obtaining practical high-energy-density metal secondary batteries, especially soft-pack batteries.

[0004] In the process of exploring the commercialization of metal negative electrodes, the problem of dendrite growth is generally solved by adding various electrolyte additives to construct artificial solid electrolyte interphases (SEI). Yang Xiaowei et al. introduced silane or siloxane functional additives to regulate the organic solvation structure of magnesium ions, construct a stable SEI, reduce the polarization overpotential of magnesium negative electrodes, and improve the cycle life of batteries (CN118040049A). Cui Guanglei et al. introduced specific inorganic chloride additives and used their in-situ chemical reaction with magnesium metal to form SEI films, thereby improving the compatibility of negative electrode interfaces and improving the cycle performance of magnesium metal secondary batteries (CN114865079A). Although the above studies have achieved certain effects on promoting uniform deposition of magnesium metal, most additives are continuously consumed during battery cycling, and the SEI layer formed is not tough enough to withstand volume changes during cycling, so the effect of improving long-cycle stability is limited.

[0005] The three-dimensional current collector has a large specific surface area and porous structure, which can reduce the local current density, promote uniform metal deposition, and provide sufficient buffer space for metal deposition. Wu Kai et al. prepared a three-dimensional porous hollow carbon fiber current collector, which has both porous and hollow structures. It can be used to load metal negative electrodes to inhibit the growth of negative electrode lithium dendrites (CN110649267A). Ye Huan et al. prepared a three-dimensional current collector by modifying the non-precious metal coating on the surface of carbon fiber by annealing reduction method, which can inhibit the formation of dendrites and changes in electrode volume in the battery (CN109950547A). Ye Huan et al. prepared a surface-modified nickel-based foam three-dimensional skeleton material by high-temperature calcination. The lithium-philic surface can promote uniform lithium deposition, and the three-dimensional skeleton can alleviate volume expansion and improve the cycle stability of lithium negative electrode (CN110649267A). Chai Zhonghua prepared copper foam by electrodeposition, and then treated the copper foam by electroplating to prepare a three-dimensional porous copper current collector, which has a significant inhibitory effect on the growth of dendrite lithium and dead lithium (CN109786750A). Yang Chengkai et al. used a three-dimensional porous copper metal coated with polydopamine as a skeleton, and continued to deposit and adsorb a uniform and dense lithium-philic silver particle layer on the surface of the copper current collector deposited with polydopamine by chemical plating, which significantly improved the cycle performance and safety of metal lithium secondary batteries (CN113937269A). Hong Bo et al. deposited metal zinc on a 3D porous current collector by electrodeposition to prepare a 3D porous zinc-loaded current collector. The current collector with this structure can effectively maintain the stability of the skeleton during the deposition of sodium or potassium metal, and achieve dendrite-free sodium or potassium deposition and long cycle life (CN110828828A). The above research has suppressed the uneven deposition of lithium to a certain extent, but the three-dimensional skeleton is generally made of metal or conductive non-metallic materials, and the metal modification method is generally high-temperature calcination, annealing induction, and reduction of electrodeposited metal on the skeleton surface. Both the skeleton material and the modification method have certain limitations, and currently they are still unable to effectively solve the problems encountered in the practical application of high-energy-density batteries. Therefore, the development of better methods for modifying metal layers on various non-metallic three-dimensional skeletons to prepare composite three-dimensional current collectors is of great significance to the development of high-energy-density metal secondary batteries. Summary of the invention

[0006] In order to solve the above existing technical problems, the present invention aims to provide a method for preparing a composite three-dimensional current collector by modifying a metal coating on a lightweight porous non-metallic skeleton through chemical plating. The composite structure prepared by modifying the metal coating on the non-metallic three-dimensional skeleton is used as a current collector. While reducing the dead weight of the three-dimensional current collector, it can also adjust the negative electrode deposition process of the secondary metal battery, thereby guiding the uniform electrodeposition of the negative electrode and extending the service life.

[0007] Chemical plating is a process in which metal ions in an electrolyte solution are reduced and deposited on the surface of a substrate using a reducing agent without the need for an external current, thereby forming a metal coating layer that is firmly bonded to the substrate. Chemical plating has the characteristics of simple process and equipment, convenient operation, and is suitable for various materials of any complex shape. The coating prepared by the chemical plating method has good density, good conductivity, and high bonding strength. Compared with other surface modification processes, chemical plating can be used to perform metal modification on various lightweight non-metallic substrates (carbon fiber cloth, polymer diaphragm, paper, foam, etc.) to obtain a high specific surface area composite three-dimensional current collector. Non-metallic composite material current collectors are characterized by light weight, porosity, and large specific surface area, providing sufficient buffer space for metal deposition. In addition, the coating modified by chemical plating has good affinity with the electrodeposited metal, which can induce uniform electrodeposition of the metal and inhibit the rapid longitudinal growth of the metal on the surface of the current collector.

[0008] Specifically, to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] A composite three-dimensional current collector comprises a non-metallic three-dimensional skeleton substrate and a metal coating uniformly distributed on the surface of the non-metallic three-dimensional skeleton substrate by chemical plating, wherein the non-metallic three-dimensional skeleton substrate is a three-dimensional porous material, preferably a lightweight three-dimensional porous material, such as carbon fiber cloth, polymer diaphragm, paper (including carbon paper, fiber paper, polymer paper, etc.) or polymer foam, etc.; the metal of the metal coating is one or more of Cu, Ag, Co, Ni, Sn, Bi, etc.

[0010] Preferably, the non-metallic three-dimensional skeleton matrix is ​​a carbon fiber cloth having a three-dimensional porous structure.

[0011] Preferably, the metal coating is a Cu coating with a thickness of 1 to 5 μm. More preferably, nano-scale Cu particles are uniformly and densely covered on each carbon fiber of the carbon fiber cloth.

[0012] The present invention provides a method for preparing the above-mentioned composite three-dimensional current collector, the steps of which are as follows:

[0013] (1) Matrix roughening: Immerse non-metallic three-dimensional skeleton matrix materials such as carbon fiber cloth in a roughening solution and heat for a period of time for roughening treatment. After the roughening is completed, stop heating, cool to room temperature, take out the substrate, wash it with deionized water, and dry it to obtain the roughened matrix material sample;

[0014] (2) Matrix grafting: The roughened carbon fiber cloth and other matrix material samples are cut into the required size, and then polydopamine (PDA) is grafted after ultrasonic cleaning to obtain a matrix sample with PDA surface modification;

[0015] (3) Matrix sensitization: Immerse the matrix sample such as carbon fiber cloth after PDA surface modification in the sensitizing solution for a period of time, take it out and rinse it with deionized water to obtain the sensitized matrix sample such as carbon fiber cloth;

[0016] (4) Matrix activation: Immerse the sensitized carbon fiber cloth and other matrix samples in the activation solution for a period of time, take out the samples, rinse them with deionized water, and then store them in ultrapure water for later use;

[0017] (5) Chemical plating: Place the activated substrate sample into the chemical plating solution, maintain a constant temperature reaction for a certain period of time, then take out the chemically plated sample, wash it, and dry it to obtain a composite three-dimensional current collector.

[0018] In the above step (1), the roughening liquid includes but is not limited to a mixture of concentrated sulfuric acid and concentrated nitric acid, a mixture of hydrogen peroxide and concentrated sulfuric acid, a mixture of chromic acid and sulfuric acid, etc. In some embodiments of the present invention, a mixture of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 1:1 is used. Preferably, the carbon fiber cloth is immersed in the roughening liquid, heated in a blast oven at 100°C for 12 h for roughening treatment, cooled, and the carbon fiber cloth is taken out and washed with deionized water until neutral, and then dried in a vacuum drying oven.

[0019] In the above step (2), the polydopamine grafting is to immerse the roughened substrate sample after ultrasonic cleaning in the grafting solution, stir it in the dark for a period of time for surface modification, and then take out the PDA surface modified substrate sample, wash it, and dry it. Wherein, in some embodiments of the present invention, the ultrasonic cleaning is to add acetone, ethanol, and ultrapure water to the roughened substrate sample in sequence for ultrasonic cleaning, and finally wash it with ultrapure water twice and soak it in ultrapure water. During grafting, the substrate sample is placed in the grafting solution, which contains 0.01-0.03 g / L dopamine hydrochloride (DA) and Tris buffer solution (5-15 mM / L, pH≈8.5), and stir it in the dark for 1-4 h. Thereafter, the PDA surface modified substrate sample is taken out and washed with ultrapure water and anhydrous ethanol for multiple times, and vacuum dried to obtain the PDA surface modified substrate sample.

[0020] In the above step (3), preferably, the sensitizing solution is a 5-30 g / L SnCl2·2H2O / HCl aqueous solution, and its composition is 5-30 g / L SnCl2·2H2O, 37% HCl 50 ml / L. In some embodiments of the present invention, the substrate sample after PDA surface modification is immersed in a 5-30 g / L SnCl2·2H2O / HCl aqueous solution at 20-50°C for 5-30 min, and then taken out and rinsed with running deionized water for three minutes to obtain a sensitized substrate sample.

[0021] In the above step (4), the activation solution includes but is not limited to PdCl2 / HCl aqueous solution, AgNO3 solution, etc. Preferably, the activation solution is a PdCl2 / HCl aqueous solution, and its composition is 0.2-2 g / L PdCl2, 37% HCl 50 ml / L. In some embodiments of the present invention, the sensitized substrate sample is immersed in a 0.2-2 g / L PdCl2 / HCl aqueous solution at 20-50°C for 5-30 min, the sample is taken out and rinsed with deionized water for multiple times, and then stored in ultrapure water for use.

[0022] In the above step (5), preferably, the chemical plating solution is a chemical copper plating solution, and its preparation process can be: weigh copper salt, complexing agent, and stabilizer respectively, dissolve in deionized water, stir at a certain speed to make a solution, and after heating to a certain temperature, add the reducing agent to the mixed solution until it is fully dissolved. Among them, the copper salt includes but is not limited to copper sulfate, copper chloride, copper acetate, copper nitrate, etc.; the complexing agent includes but is not limited to disodium ethylenediaminetetraacetic acid, potassium sodium tartrate, trisodium citrate, etc.; the stabilizer includes but is not limited to triethanolamine, thiosulfate, potassium ferrocyanide trihydrate, 2-amino-5-mercapto-1,3,4-thiadiazole, etc.; the reducing agent includes but is not limited to dimethylaminoborane, formaldehyde, glyoxylic acid, sodium hypophosphite, sodium borohydride, aminoborane, hydrazine hydrate, etc. In some embodiments of the present invention, the copper source in the chemical plating solution is copper sulfate pentahydrate with a concentration of 1.0 to 2.0 g / L; the complexing agent is disodium ethylenediaminetetraacetate with a concentration of 2.0 to 2.5 g / L; the stabilizer is triethanolamine with a concentration of 11 to 15 g / L; and the reducing agent is dimethylaminoborane with a concentration of 8 to 12 g / L.

[0023] Preferably, the chemical plating reaction temperature is 25-60°C and the chemical plating reaction time is 5-120 min. In order to improve the corrosion resistance of the Cu plating layer and further improve the conductivity of the Cu plating layer, the composite three-dimensional current collector prepared by chemical plating can be annealed at a temperature range of 500-600°C.

[0024] The present invention also provides a metal negative electrode, comprising the composite three-dimensional current collector and metals such as magnesium, zinc, lithium, sodium, potassium and calcium electrodeposited thereon. Preferably, it is a magnesium metal negative electrode or a zinc metal negative electrode, comprising the composite three-dimensional current collector prepared by the above method and magnesium metal or zinc metal electrodeposited thereon.

[0025] Preferably, the surface of the composite three-dimensional current collector is between 0.1 and 8 mA / cm 2 Deposition at a current density of 0.2 to 8 mAh / cm 2 to obtain the metal negative electrode such as magnesium or zinc.

[0026] The present invention also provides the use of the composite three-dimensional current collector and the metal negative electrode in a metal secondary battery, preferably the use of a magnesium metal negative electrode in a magnesium metal secondary battery, thereby obtaining a metal secondary battery, the negative electrode of which is the metal negative electrode.

[0027] The beneficial effects of the present invention are:

[0028] (1) The present invention provides a method for preparing a composite three-dimensional current collector by depositing metal on a lightweight non-metallic three-dimensional skeleton substrate through chemical plating, and a composite three-dimensional current collector such as copper / carbon fiber cloth is prepared. The chemical plating process has low cost and convenient operation. The chemical plating solution using dimethylaminoborane as a reducing agent is stable and has a long service life. The copper plating layer of the prepared copper / carbon fiber cloth composite three-dimensional current collector is evenly coated on each carbon fiber, and the plating layer is uniform and dense and has good bonding strength with the carbon fiber substrate.

[0029] (2) The present invention utilizes the porous structure and large specific surface area of ​​composite three-dimensional current collectors such as copper / carbon fiber cloth to provide a larger buffer space for the deposition of metals such as Mg and Zn. During the electrodeposition, metal coatings such as Cu are used to adjust the nucleation and growth process of metals such as Mg and Zn, thereby inducing the uniform growth of metals along the three-dimensional skeleton fibers.

[0030] (3) The battery negative electrode composed of a composite three-dimensional current collector such as copper / carbon fiber cloth and metals such as Mg and Zn has excellent charge and discharge performance, thereby improving the cycle stability, cycle life and coulombic efficiency of the battery.

[0031] (4) The battery negative electrode of the present invention is composed of a composite three-dimensional current collector such as copper / carbon fiber cloth and a metal such as Mg and Zn. The metal is uniformly deposited on the three-dimensional skeleton fiber, which can enhance the stability of the electrode interface and reduce dendrite growth, reduce the metal electrodeposition overpotential, and extend the service life of the metal negative electrode. Therefore, the deposition / stripping behavior of the metal when using a thin diaphragm is significantly improved, providing a new idea for promoting the practical application of high energy density Mg, Zn and other metal secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the scanning electron microscopy result of Mg deposition on the carbon fiber cloth (CC) substrate in Comparative Example 1.

[0033] Figure 2 The overpotential and cycle stability test results of the assembled half-cell in Example 1 are shown in Table 1, where a and b are respectively 2 and 8 mA / cm 2 The first cycle overpotential test results of the Mg negative electrode and CC positive electrode half-cell (named Mg / / CC half-cell) under current density, c is the Mg / / CC half-cell at 1 mA / cm 2Cyclic stability test results under different current densities.

[0034] Figure 3 This is the scanning electron microscope result of Mg deposited on the copper sheet in Comparative Example 2.

[0035] Figure 4 The overpotential and cycle stability test results of the assembled half-cell in Example 2 are shown in Table 2, where a and b are respectively 2 and 8 mA / cm 2 The test results of the first cycle overpotential of the Mg negative electrode and Cu positive electrode half-cell (named Mg / / Cu half-cell) under current density, c is the Mg / / Cu half-cell at 1 mA / cm 2 Cyclic stability test results under different current densities.

[0036] Figure 5 These are the scanning electron microscope and energy spectrum results of the carbon fiber cloth (CC) and the Cu@CC composite three-dimensional current collector in Example 1, wherein a is a scanning electron microscope (SEM) photo of the carbon fiber cloth, b is a scanning electron microscope photo of the Cu@CC composite three-dimensional current collector, and c and d are the SEM and EDS spectra of the Cu@CC composite three-dimensional current collector.

[0037] Figure 6 This is the scanning electron microscopy result of Mg deposited on the Cu@CC composite three-dimensional current collector in Example 1.

[0038] Figure 7 is the overpotential and cycle stability test results of the assembled half-cell in Example 1, where a and b are the overpotential and cycle stability of the Mg negative electrode and Cu@CC positive electrode half-cell (named Mg / / Cu@CC half-cell) at 1 mA / cm 2 and 8 mA / cm 2 The first cycle overpotential test results under current density, c is the Mg / / Cu@CC half-cell at 1 mA / cm 2 Cyclic stability test results under different current densities.

[0039] Figure 8 It is the coulombic efficiency and charge and discharge results of the half-cells assembled with three current collectors in Example 6, wherein a shows the coulombic efficiency of the three half-cells Mg / / CC, Mg / / Cu and Mg / / Cu@CC, and b and c are the charge and discharge curves of the 1st and 100th cycles, respectively.

[0040] Fig. 9 1 is the voltage-time curve of the half-cell assembled with three current collectors in Example 6, wherein a, b, and c correspond to CC, Cu, and Cu@CC composite three-dimensional current collectors, respectively.

[0041] Fig.10This is the coulombic efficiency result of the Zn half-cell assembled with three current collectors in Example 9.

[0042] Fig.11 In Example 10, three current collectors were pre-deposited with magnesium and used as negative electrodes to assemble the full battery for discharge capacity and coulombic efficiency.

[0043] Fig.12 In Example 11, three current collectors were pre-deposited with magnesium and used as negative electrodes to assemble the full battery to obtain the discharge capacity and coulombic efficiency results.

[0044] Fig.13 These are the discharge capacity and coulombic efficiency results of the soft-pack battery assembled after Cu@CC was pre-deposited with magnesium in Example 12 and used as the negative electrode, where a and b correspond to the glass fiber filter paper separator and Celgard separator, respectively. DETAILED DESCRIPTION

[0045] The present invention is described in detail below by specific examples, but the present invention can be implemented by other methods and is not limited to the following examples. Therefore, the protection scope of the present invention is not limited by the following examples. The experimental methods, reagents and materials described in the examples, unless otherwise specified, are conventional methods or can be purchased through commercial channels. The experimental instruments and equipment involved in the examples, unless otherwise specified, are parameters selected by the manufacturer.

[0046] Comparative Example 1

[0047] A pure carbon fiber cloth (CC) treated with a mixture of sulfuric acid and nitric acid and not modified by chemical plating was used as the positive electrode and a metal Mg sheet was used as the negative electrode to assemble a half-cell. Mg metal was deposited on the carbon fiber cloth by electrochemical means. At 0.1 mA / cm 2 Deposition at a current density of 8 mAh / cm 2 After the magnesium metal is removed, the microstructure of the Mg deposited on the carbon fiber cloth is shown in Figure 1 As shown in the figure, the Mg deposition layer on the three-dimensional current collector skeleton of the carbon fiber cloth is uneven, and it grows continuously along a small number of nucleation sites to generate large pieces of Mg. This shows that although the carbon fiber cloth is a three-dimensional porous structure, it lacks the induced deposition effect of the surface coating layer, so its nucleophilicity with Mg metal is poor, and the controllability of Mg metal electrodeposition on the carbon fiber cloth matrix is ​​poor. Figure 2 a and b are the Mg negative electrode and CC positive half-cell (named as Mg / / CC half-cell) obtained by the above method at 1 mA / cm 2 and 8 mA / cm 2 The test results of the first cycle overpotential under current density show that the above negative electrode has a current density of 1 mA / cm 2 and 8 mA / cm 2The overpotentials at the current density are large (138 mV and 437 mV, respectively). 2 Cyclic stability diagram at current density ( Figure 2 As can be seen from (c), the battery cycle stability is poor and the voltage is high throughout the entire process.

[0048] Comparative Example 2

[0049] A metal Cu sheet was used as the positive electrode and a metal Mg sheet was used as the negative electrode to assemble a half-cell (named Mg / / Cu half-cell). Mg metal was deposited on the copper sheet by electrochemical means. 2 Deposition at a current density of 8 mAh / cm 2 After magnesium metal is removed, the microstructure of Mg deposition on the copper sheet is shown in Figure 3 As shown. It can be seen that the Mg deposition layer on the copper skeleton can only be deposited on the surface of copper metal, generating large pieces of Mg. This shows that although the copper sheet has good nucleophilicity with Mg, it is a planar structure with no gaps in the middle, which cannot provide enough nucleation space for the electrodeposition of Mg metal. Therefore, the electrodeposition process of Mg metal will continue to grow along some nucleation sites. Figure 4 a and b are the Mg / / Cu half-cell obtained by the above method at 1 mA / cm 2 and 8 mA / cm 2 The test results of the first cycle overpotential under current density show that the above negative electrode 1 mA / cm 2 and 8 mA / cm 2 The overpotentials at the current density are large (188 mV and 427 mV, respectively). 2 Cyclic stability diagram at current density ( Figure 4 As can be seen from (c), the battery cycle stability is poor and the voltage is high throughout the entire process.

[0050] Example 1

[0051] Preparation of Cu@CC composite three-dimensional current collector by chemical plating:

[0052] (1) Substrate pretreatment

[0053] The purchased carbon fiber cloth three-dimensional current collector was placed in a mixture of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 1:1, heated and soaked in a blast drying oven at 100°C for 12 hours. After the end, the heating was stopped, cooled to room temperature, and the carbon fiber cloth was taken out. After that, it was repeatedly washed with deionized water several times, and dried in a vacuum drying oven at 60°C to obtain a hydrophilic carbon fiber cloth sample.

[0054] The acid-treated sample was cut into a certain size, and acetone, ethanol, and ultrapure water were added in turn for ultrasonic cleaning. Finally, it was washed twice with ultrapure water and soaked in ultrapure water. Then it was placed in a flask, 200 mL of Tris buffer solution (10 mM / L, pH ≈ 8.5) and 0.02 g / L dopamine hydrochloride were added, and stirred for 2 h in the dark. After that, the carbon fiber cloth sample modified with polydopamine was taken out and washed three times with ultrapure water and anhydrous ethanol, and vacuum dried. Polydopamine was grafted onto the surface of the carbon fiber cloth.

[0055] The carbon fiber cloth sample grafted with PDA was immersed in a 10 g / L SnCl2·2H2O / HCl aqueous solution at 25°C for 15 min, then taken out and rinsed with flowing deionized water for three minutes. The hydrolyzed tin ions were adsorbed on the surface of the substrate to obtain the sensitized carbon fiber cloth sample. The sensitized carbon fiber cloth sample was immersed in a 0.2 g / L PdCl2 / HCl aqueous solution at 25°C for 15 min, the sample was taken out and rinsed with deionized water three times, and the Pd active sites were successfully introduced into the surface of the carbon fiber cloth. The pre-treated carbon fiber cloth was then stored in ultrapure water for later use.

[0056] (2) Chemical plating of Cu

[0057] Weigh 1.5 g of copper sulfate pentahydrate, 2.35 g of disodium ethylenediaminetetraacetate, and 11.3 g of triethanolamine respectively and dissolve them in 1 L of deionized water. Stir at 500 r / min to make a uniform mixed solution. Take 200 mL of the plating solution into a chemical plating tank and heat it to 50°C. Then add 0.236 g of the reducing agent dimethylaminoborane to the above solution and stir until it is fully dissolved.

[0058] The activated carbon fiber cloth sample was placed in the above chemical plating solution and kept at 50°C for 30 min. Then the sample after chemical plating was taken out. Its color changed from black to purple-red. It was rinsed with deionized water and anhydrous ethanol three times in sequence. After drying, a composite three-dimensional current collector was obtained. Scanning electron microscopy and EDS spectrum ( Figure 5 ) It can be seen that nano-scale particles of uniform size are evenly covered on the carbon fiber cloth, the coating is mainly Cu element, and the Cu@CC material after chemical plating still maintains a three-dimensional hollow porous structure.

[0059] (3) Assembly of half-cell and performance testing

[0060] A half-cell (named Mg / / Cu@CC half-cell) was assembled with a metal Mg sheet as the negative electrode, a glass fiber filter paper as the separator, a Cu@CC composite three-dimensional current collector (punched into a disc with a diameter of 19 mm) as the positive electrode, and an APC solution (0.4 M (MgPhCl)2-AlCl3 / THF) as the electrolyte. Mg metal was deposited on the Cu@CC composite three-dimensional current collector by an electrochemical method. 2 Deposition at a current density of 8 mAh / cm 2 After the magnesium metal is removed, the microstructure of the Mg deposited on Cu@CC is shown in Figure 6 As shown. From the electron microscopy results, it can be seen that Mg metal grows along the fibers in Cu@CC and is evenly distributed in the fiber gaps and on the surface, without large pieces of Mg being generated. This shows that the Cu@CC composite three-dimensional current collector prepared by chemically plating the carbon fiber cloth substrate, that is, the three-dimensional porous structure of the substrate is retained to provide sufficient space for the deposition of Mg metal, and the surface-modified metal copper coating has good nucleophilicity with Mg, which can induce the uniform electrodeposition of Mg metal on the three-dimensional current collector. Figure 7 a and b are the Mg / / Cu@CC half-cells obtained by the above method at 1 mA / cm 2 and 8 mA / cm 2 The first cycle overpotential test under current density shows that the above negative electrode 1 mA / cm 2 and 8 mA / cm 2 The overpotentials at the current densities are small (122 mV and 382 mV, respectively). 2 Cyclic stability diagram at current density ( Figure 7 As can be seen from Figure c), the voltage polarization of magnesium deposition / dissolution on Cu@CC is small, and the assembled Mg / / Cu@CC half-cell can be stably cycled for more than 1000 times with an average coulombic efficiency of 99.80%.

[0061] Example 2

[0062] The other conditions were the same as those in Example 1, except that the reaction temperature of the chemically plated modified carbon fiber cloth was 20°C. 2 The battery cycle was stable for 1400 cycles at the current density, and the average Coulomb efficiency was 99.78%.

[0063] Example 3

[0064] The other conditions were the same as those in Example 1, except that the reaction temperature of the chemically plated modified carbon fiber cloth was 30°C. The Cu@CC obtained under these conditions was assembled into a half-cell with a Mg metal negative electrode and the electrochemical performance of the cell was tested. The Mg / / Cu@CC half-cell was2 The stable cycle under the current density was 1390 times, and the average Coulomb efficiency was 99.47%.

[0065] Example 4

[0066] The other conditions were the same as those in Example 1, except that the reaction temperature of the chemically plated modified carbon fiber cloth was 40°C. The Cu@CC obtained under these conditions was assembled into a half-cell with a Mg metal anode and the electrochemical performance of the cell was tested. The Mg / / Cu@CC half-cell had a 2 The stable cycle under the current density was 1390 times, and the average Coulomb efficiency was 99.81%.

[0067] Example 5

[0068] The other conditions were the same as those in Example 1, except that the reaction time of chemical plating modified carbon fiber cloth was 10 min. The Cu@CC obtained under these conditions was assembled into a half-cell with a Mg metal negative electrode and the electrochemical performance of the cell was tested. The Mg / / Cu@CC half-cell was 2 The stable cycle at the current density was 1400 times, and the average Coulomb efficiency was 99.61%.

[0069] Example 6

[0070] Other conditions were the same as those in Example 1, except that the diaphragm was replaced with a thinner Celgard diaphragm, a metal Mg sheet was used as the negative electrode, and Cu, CC, and Cu@CC composite three-dimensional current collectors were used as the positive electrode to assemble half-cells for electrochemical testing. 2 The charge and discharge cycle test was carried out at a current density of . The coulomb efficiency comparison and charge and discharge curve comparison of the half-cell composed of three positive electrode materials are as follows Figure 8 As shown. Figure 8 As can be seen in Figure a, the Mg / / Cu@CC half-cell can be stably cycled for more than 130 cycles at high coulombic efficiency, while the coulombic efficiency of the Mg / / CC half-cell will decay sharply within 30 cycles, and the Mg / / Cu half-cell will short-circuit within 10 cycles and cannot continue to cycle. The three-dimensional cross-linked network structure can reduce the local current density and slow down the growth rate of Mg, thereby improving the cycle performance of the half-cell; in addition, the introduction of metal plating on the surface of the three-dimensional network fiber effectively induces the uniform electrodeposition of Mg, further improving the coulombic efficiency and cycle life of the Mg / / Cu@CC half-cell. Figure 8 The charge-discharge curves shown in b and c also show that the Mg / / Cu@CC half-cell has highly reversible charge-discharge performance and the voltage polarization is significantly reduced. 2 Cyclic stability diagram at current density ( Fig. 9) It can be seen that even with a thinner Celgard separator, the Mg / / Cu@CC half-cell maintains excellent cycling stability at higher current density.

[0071] Example 7

[0072] The other conditions were the same as those in Example 1, except that the diaphragm was replaced with a thinner Celgard diaphragm and the deposition time of chemical Cu plating was 3 min. Due to the short reaction time, the carbon fiber was not completely covered by the Cu plating layer, and some fibers were exposed, resulting in uneven magnesium deposition. The Cu@CC composite three-dimensional current collector was used as the positive electrode and assembled with the magnesium metal negative electrode. The half-cell was tested at 0.1 mA / cm 2 The charge-discharge cycle test was carried out at a current density of 1.5 Mg / / Cu@CC half-cell with an average coulombic efficiency of 97.75% after 980 cycles.

[0073] Example 8

[0074] The other conditions were the same as those in Example 1, except that the diaphragm was replaced with a thinner Celgard diaphragm and the deposition time of chemically plated Cu was 5 min. The Cu@CC composite three-dimensional current collector was used as the positive electrode and a half-cell was assembled with a magnesium metal negative electrode. 2 The charge-discharge cycle test was carried out at a current density of 1.5 Mg / / Cu@CC half-cell with 980 cycles and a coulombic efficiency of 99.55%.

[0075] Example 9

[0076] Other conditions are the same as those in Example 1, except that a metal Zn sheet is used as the negative electrode, a ZnSO4 aqueous solution is used as the electrolyte, and half-cells are assembled with CC, Cu and Cu@CC as the positive electrodes (named Zn / / CC half-cell, Zn / / Cu half-cell and Zn / / Cu@CC half-cell, respectively). The coulombic efficiency of the Zn / / Cu@CC half-cell is shown in Fig.10 As shown. Fig.10 It can be seen that at 8.0 mA / cm 2 At high current density, the Zn / / Cu@CC half-cell can stably cycle for nearly 50 cycles at high coulombic efficiency, while the Zn / / Cu half-cell cannot stably cycle due to short circuit within 30 cycles, and the Zn / / CC half-cell short circuits within 15 cycles. This shows that the Cu@CC composite three-dimensional current collector is also beneficial to improving the cycle stability and life of Zn batteries.

[0077] Example 10

[0078] The other conditions were the same as those in Example 1, except that after the half-cell was assembled, the 2 The current density of 2 mAh / cm was deposited on Cu, CC and Cu@CC composite current collectors.2 After depositing magnesium (named Mg@Cu, Mg@CC and Mg@Cu@CC respectively), they were disassembled, and then the three current collectors with deposited magnesium were cleaned with tetrahydrofuran. After the tetrahydrofuran evaporated, they were used as the negative electrode of the whole battery. Mo6S8, conductive agent (Super P) and binder (PVDF) were fully mixed in a mass ratio of 7:2:1, evenly coated on Ni foil, and vacuum dried in a vacuum oven at 60°C for 12 h. Then, electrode discs with a diameter of 1 cm were punched out as the positive electrode of the whole battery, with a loading of 1-1.5 mg. The whole battery was assembled with Whatman glass fiber filter paper as the diaphragm and APC (200 μL 0.4 M (MgPhCl)2-AlCl3 / THF) solution as the electrolyte. Pre-deposited 2 mAh / cm 2 The three current collectors Mg@Cu, Mg@CC and Mg@Cu@CC were used as negative electrodes and assembled into full batteries (named Mg@Cu / / Mo6S8 full battery, Mg@CC / / Mo6S8 full battery and Mg@Cu@CC / / Mo6S8 full battery, respectively). The electrochemical performances are shown in Figure 2 Fig.11 As shown. Fig.11 It can be obtained that the Mg@Cu@CC / / Mo6S8 full battery assembled with Cu@CC composite three-dimensional current collector can stably cycle for 450 cycles with an average coulombic efficiency of 99.24%, and the discharge specific capacity of the Mo6S8 cathode is about 71.6 mAh / g at the 450th cycle. The Mg@Cu / / Mo6S8 full battery assembled with copper foil has a discharge specific capacity of 70.3 mAh / g at 450 cycles. However, the capacity of the Mg@CC / / Mo6S8 full battery assembled with CC rapidly decayed after 130 cycles, which may be caused by the poor nucleophilicity of Mg and carbon fiber cloth.

[0079] Embodiment 11

[0080] The other conditions were the same as those in Example 1, except that after the half-cell was assembled, the 2 The current density of 2 mAh / cm was deposited on Cu, CC and Cu@CC composite current collectors. 2After depositing Mg metal (named Mg@Cu, Mg@CC and Mg@Cu@CC respectively), they were disassembled, and then the three current collectors with deposited magnesium were cleaned with tetrahydrofuran. After the tetrahydrofuran evaporated, they were used as the negative electrode of the full battery. Mo6S8, conductive agent (Super P) and binder (PVDF) were fully mixed in a mass ratio of 7:2:1, evenly coated on Ni foil, and vacuum dried in a vacuum oven at 60℃ for 12 h. Then, electrode discs with a diameter of 1 cm were punched out as the positive electrode of the full battery, with a loading of 1-1.5 mg. The thinner Celgard 2325 was used as the separator, and APC (60 μL 0.4 M (MgPhCl)2-AlCl3 / THF) solution was used as the electrolyte to assemble the full battery (named Mg@Cu / / Mo6S8 full battery, Mg@CC / / Mo6S8 full battery and Mg@Cu@CC / / Mo6S8 full battery respectively). Electrochemical performance tests show that the Mg@CC / / Mo6S8 full battery assembled with CC three-dimensional current collector first experienced capacity decay, and the discharge capacity was almost 0 after 90 cycles. In addition, the unevenness of Mg metal deposition on the two-dimensional copper foil also caused the Mg@Cu / / Mo6S8 full battery assembled with copper foil as the current collector to experience capacity decay after long cycles, and eventually short-circuited at 270 cycles. The discharge capacity of the Mg@Cu@CC / / Mo6S8 full battery assembled with Cu@CC composite three-dimensional current collector can still reach 72.7 mAh / g after 450 cycles, with a capacity retention rate of 96.3% and a cycle average coulombic efficiency of 99.60% ( Fig.12 ). These results show the advantages of Cu@CC in the Mg metal deposition / dissolution process and its high compatibility with Mo6S8 cathode.

[0081] Example 12

[0082] The other conditions were the same as those in Example 1, except that the Cu@CC composite three-dimensional current collector prepared by chemical plating was first assembled into a soft-pack half-cell (named Mg / / Cu@CC soft-pack half-cell). The specific preparation steps were as follows: a metal Mg sheet was used as the negative electrode, Celgard 2325 was used as the separator, Cu@CC was used as the positive electrode, and APC solution (0.4 M (MgPhCl)2-AlCl3 / THF, purchased from Duoduo Chemical) was used as the electrolyte. The electrolyte was charged at 0.1 mA / cm 2 The current density of 2.0 mAh / cm was pre-deposited on the Cu@CC current collector. 2 The battery was then disassembled, and the pre-magnesium-treated Cu@CC was cleaned with THF. After the THF was completely evaporated, the pre-magnesium-deposited Cu@CC was obtained, which was named Mg@Cu@CC.

[0083] The Mg@Cu@CC after pre-deposition of magnesium was used as the negative electrode of the full battery. Mo6S8, conductive agent (Super P) and binder (PVDF) were fully mixed at a mass ratio of 7:2:1, evenly coated on Ni foil, and vacuum dried in a vacuum oven at 60 °C for 12 h before being used as the positive electrode of the full battery. The Whatman glass fiber filter paper (Mo6S8 active material loading of 0.585 mg / cm 2 ) and thinner Celgard 2325 (Mo6S8 active material loading of 0.429 mg / cm 2 ) as the diaphragm, APC solution (0.4 M (MgPhCl)2-AlCl3 / THF) as the electrolyte, assembled into a soft-pack full battery (named Mg / / Cu@CC soft-pack full battery). The full battery with glass fiber filter paper as the diaphragm was stably cycled for 100 cycles. At the 100th cycle, the discharge specific capacity of the Mo6S8 cathode was about 54.4 mAh / g, and the capacity retention rate was 93.96% ( Fig.13 Even with the thinner Celgard 2325 as the separator, the discharge capacity of the soft-pack full battery assembled with Cu@CC composite three-dimensional current collector can still reach 69.9 mAh / g after 100 cycles, and the capacity retention rate is 93.32% ( Fig.13 b). The experimental results show that the Cu@CC composite three-dimensional current collector can be used as the negative electrode carrier of the soft-pack battery. Even in the case of a thinner separator (Celgard 2325), the battery can still cycle stably and has a high discharge specific capacity.

[0084] The preferred specific embodiments and experimental verification of the present invention are described in detail above. It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a metal negative electrode, the metal negative electrode comprising a composite three-dimensional current collector and a metal electrodeposited on the composite three-dimensional current collector, wherein: The composite three-dimensional current collector comprises a non-metallic three-dimensional skeleton matrix and a metal coating uniformly distributed on the surface of the non-metallic three-dimensional skeleton matrix by chemical plating; the non-metallic three-dimensional skeleton matrix is ​​a three-dimensional porous material selected from one of carbon fiber cloth, paper or polymer foam; the metal of the metal coating is selected from one or more of Cu, Ag, Co, Ni, Sn and Bi; the metal electrodeposited on the composite three-dimensional current collector is magnesium, zinc, lithium, sodium, potassium or calcium; characterized in that the preparation method comprises the following steps: 1) Matrix roughening: Immerse the non-metallic three-dimensional skeleton matrix material in a roughening solution, heat it for a period of time for roughening treatment, then cool it to room temperature, take out the matrix material, wash it with deionized water, and dry it; 2) Matrix grafting: the roughened matrix material is cut into the required size, and polydopamine is grafted after ultrasonic cleaning to obtain a matrix with polydopamine surface modification, wherein the polydopamine grafting is performed by immersing the matrix in a grafting solution, stirring for 1 to 4 hours in a dark environment, and then taking out the matrix, washing it, and drying it, wherein the grafting solution is a Tris buffer solution containing 0.01 to 0.03 g / L dopamine hydrochloride; 3) Matrix sensitization: immerse the substrate modified with polydopamine in a sensitizing solution for a period of time, take it out and rinse it with deionized water to obtain a sensitized substrate; 4) Activation of substrate: Immerse the sensitized substrate in the activation solution for a period of time, take it out and rinse it with deionized water to obtain the activated substrate; 5) Chemical plating: Put the activated substrate into the chemical plating solution, keep the reaction at a constant temperature for a certain period of time, then take out the chemically plated substrate, wash it, and dry it to obtain a composite three-dimensional current collector; 6) Electrodeposition: Electrodepositing metal on the surface of the composite three-dimensional current collector.

2. The preparation method according to claim 1, characterized in that The non-metal three-dimensional skeleton matrix is ​​carbon fiber cloth; the metal coating is a Cu coating with a thickness of 1 to 5 μm.

3. The preparation method according to claim 1, characterized in that: The roughening solution in step 1) is a mixture of concentrated sulfuric acid and concentrated nitric acid, a mixture of hydrogen peroxide and concentrated sulfuric acid, or a mixture of chromic acid and sulfuric acid.

4. The preparation method according to claim 1, characterized in that: The sensitizing solution in step 3) is a SnCl2·2H2O / HCl aqueous solution, and the substrate is immersed in the sensitizing solution at 20-50°C for 5-30 min; the activating solution in step 4) is a PdCl2 / HCl aqueous solution or an AgNO3 solution, and the substrate is immersed in the activating solution at 20-50°C for 5-30 min.

5. The preparation method according to claim 1, characterized in that: The chemical plating solution in step 5) is a chemical copper plating solution, which is prepared by dissolving a copper salt, a complexing agent, and a stabilizer in deionized water, stirring and heating, and then adding a reducing agent; wherein the copper salt is selected from copper sulfate, copper chloride, copper acetate, and copper nitrate; the complexing agent is selected from disodium ethylenediaminetetraacetic acid, potassium sodium tartrate, and trisodium citrate; the stabilizer is selected from triethanolamine, thiosulfate, potassium ferrocyanide trihydrate, 2-amino-5-mercapto-1,3,4-thiadiazole; the reducing agent is selected from dimethylaminoborane, formaldehyde, glyoxylic acid, sodium hypophosphite, sodium borohydride, aminoborane, and hydrazine hydrate; the chemical plating reaction temperature is 25-60°C, and the reaction time is 5-120 min.

6. The preparation method according to claim 1, characterized in that: Step 6) 0.1~8 mA / cm 2 Deposition at a current density of 0.2 to 8 mAh / cm 2 of magnesium or zinc to obtain a magnesium or zinc metal negative electrode.

7. The metal negative electrode obtained according to the preparation method according to any one of claims 1 to 6.

8. A metal secondary battery, characterized in that: The negative electrode of the metal secondary battery is the metal negative electrode according to claim 7.

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