CN119517997A

CN119517997A - Composite three-dimensional current collector, metal anode and metal secondary battery prepared by chemical plating

Info

Publication number: CN119517997A
Application number: CN202510098249.9A
Authority: CN
Inventors: 李琦; 周剑; 徐东升; 柴昱明
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2025-01-22
Filing date: 2025-01-22
Publication date: 2025-02-25
Anticipated expiration: 2045-01-22
Also published as: CN119517997B

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

Composite three-dimensional current collector prepared based on chemical plating, metal negative electrode and metal secondary battery

Technical Field

The invention belongs to the technical field of metal secondary batteries, and particularly relates to a non-metal framework composite three-dimensional current collector prepared based on chemical plating, a corresponding metal negative electrode and a corresponding metal secondary battery.

Background

In recent years, in the application of large-sized devices such as power-driven vehicles and energy storage systems, there has been an increasing demand for secondary batteries having high energy density. Metal secondary batteries based on Mg, li, zn, na, K, ca and other metal cathodes have high energy density and are a high-performance energy storage battery system of great interest.

However, metal anodes still present challenges in the practical process, one of which is uncontrolled dendrite growth. On one hand, dendrites formed in the metal deposition process are easy to pierce through a diaphragm to contact with a positive electrode, so that a battery is short-circuited or even a fire disaster occurs, and on the other hand, dendrites can also have side reactions with electrolyte, so that coulomb efficiency is reduced, and the cycle life is limited. In the research of metal secondary batteries, thicker glass fiber separators are generally used to reduce the risk of short circuits during cycling, but the dead weight of the thick separators and the limitation of the E/C ratio are very disadvantageous for obtaining practical high energy density metal secondary batteries, especially soft pack batteries.

In exploring the commercialization of metal anodes, dendrite growth problems are generally solved by adding various electrolyte additives to build an artificial solid electrolyte interface (Solid electrolyte interphases, SEI). Yang Xiaowei and the like regulate and control the organic solvation structure of magnesium ions by introducing silane or siloxane functional additives, construct stable SEI, reduce the polarization overpotential of a magnesium negative electrode and improve the cycle life of a battery (CN 118040049A). Cui Guanglei and the like form an SEI film by introducing a specific inorganic chloride additive and utilizing in-situ chemical reaction of the SEI film and magnesium metal, so that the interface compatibility of a negative electrode is improved, and the cycle performance of the magnesium metal secondary battery is improved (CN 114865079A). Although the above-mentioned studies have a certain effect of promoting uniform deposition of magnesium metal, most additives are continuously consumed during the battery cycle, and the formed SEI layer has insufficient toughness and cannot withstand the volume change during the cycle, so that the long-cycle stability improvement effect is limited.

The three-dimensional current collector has a larger specific surface area and a porous structure, can reduce local current density, promote uniform deposition of metal, and provide sufficient buffer space for deposition of metal. Wu Kai et al prepared a three-dimensional porous hollow carbon fiber current collector having both porous and hollow structures for supporting a metal anode that inhibited the growth of negative lithium dendrites (CN 110649267 a). She Huan and the like, the three-dimensional current collector prepared by modifying the non-noble metal coating on the surface of the carbon fiber by an annealing reduction method can inhibit dendrite formation and electrode volume change in the battery (CN 109950547A). She Huan and the like prepare the foam nickel-based three-dimensional framework material with surface modification by high-temperature calcination, the surface of the lithium-philic material can promote uniform deposition of lithium, the three-dimensional framework can relieve volume expansion, and the cycling stability of a lithium negative electrode is improved (CN 110649267A). Copper foam is prepared by the electro-deposition method of China, and then the three-dimensional porous copper current collector is prepared by treating the copper foam by an electroplating method, and the current collector has obvious inhibition effect on the growth of dendrite lithium and dead lithium (CN 109786750A). Yang Chengkai and the like take polydopamine coated three-dimensional porous copper metal as a framework, and a uniform and compact lithium-philic silver particle layer is continuously deposited and adsorbed on the surface of a copper current collector for depositing polydopamine by an electroless plating method, so that the cycle performance and the safety (CN 113937269A) of the metal lithium secondary battery are remarkably improved. Flood wave and the like deposit metal zinc on the 3D porous current collector through an electrodeposition means to prepare the 3D porous zinc-loaded current collector. The current collector with the structure can effectively maintain the framework stability in the deposition process of sodium or potassium metal, and realize dendrite-free sodium or potassium deposition and long cycle life (CN 110828828A). The above-mentioned research has suppressed the nonuniform deposition of lithium to a certain extent, but the three-dimensional skeleton generally adopts metal or conductive nonmetallic material, and the metal modification method generally comprises high-temperature calcination, annealing induction and reduction of electrodeposited metal on the surface of the skeleton. Both the framework material and the modification method have certain limitations, and the difficult problems in the practical process of the high-energy-density battery can not be solved effectively at present. Therefore, the development of a better method for preparing the composite three-dimensional current collector by modifying the metal layer on various nonmetallic three-dimensional frameworks is of great significance to the development of the metal secondary battery with high energy density.

Disclosure of Invention

In order to solve the above-mentioned 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 nonmetallic skeleton by electroless plating. The composite structure prepared by modifying the metal coating with the nonmetal three-dimensional framework is used as a current collector, so that the dead weight of the three-dimensional current collector is reduced, the negative electrode deposition process of the secondary metal battery can be regulated, the uniform electrodeposition of the negative electrode is guided, and the service life is prolonged.

Electroless plating is a process in which metal ions in an electrolyte solution are reduced and deposited on the surface of a substrate by a reducing agent without applying an electric current to form a metal plating layer firmly bonded to a substrate. The chemical plating has the characteristics of simple process and equipment, convenient operation and the like, and is suitable for various materials with any complex shape. The plating layer prepared by the chemical plating method has good compactness, good conductivity and high binding force. Compared with other surface modification processes, the electroless plating can carry out metal modification on various light nonmetallic substrates (carbon fiber cloth, polymer diaphragms, paper, foam and the like) to obtain the high specific surface area composite three-dimensional current collector. The non-metal matrix composite current collector has the characteristics of light weight, multiple holes and large specific surface area, and provides enough buffer space for metal deposition. In addition, the chemical plating modified coating has better affinity with electrodeposited metal, can induce uniform electrodeposited metal, and inhibit the metal from growing longitudinally and rapidly on the surface of the current collector.

Specifically, in order to achieve the technical purpose, the invention adopts the following technical scheme:

The composite three-dimensional current collector comprises a nonmetallic three-dimensional framework substrate and metal plating layers uniformly distributed on the surface of the nonmetallic three-dimensional framework substrate through electroless plating, wherein the nonmetallic three-dimensional framework substrate is a three-dimensional porous material, preferably a light three-dimensional porous material such as carbon fiber cloth, a polymer diaphragm, paper (comprising carbon paper, fiber paper, high polymer paper and the like) or polymer foam and the like, and one or more of metals such as Cu, ag, co, ni, sn, bi and the like of the metal plating layers.

Preferably, the nonmetallic three-dimensional skeleton matrix is carbon fiber cloth with a three-dimensional porous structure.

Preferably, the metal coating is a Cu coating, and the thickness is 1-5 mu m. More preferably, each carbon fiber of the carbon fiber cloth is uniformly and densely covered with nano-sized Cu particles.

The invention provides a preparation method of the composite three-dimensional current collector, which comprises the following steps:

(1) The substrate roughening, namely soaking a non-metal three-dimensional framework substrate material such as carbon fiber cloth and the like in a roughening solution, heating for a period of time to perform roughening treatment, stopping heating after roughening, cooling to room temperature, taking out a substrate, washing with deionized water, and drying to obtain a roughened substrate material sample;

(2) Cutting the roughened matrix material samples such as carbon fiber cloth and the like into required sizes, and performing Polydopamine (PDA) grafting after ultrasonic cleaning to obtain a matrix sample after PDA surface modification;

(3) Matrix sensitization, namely immersing matrix samples such as carbon fiber cloth and the like subjected to PDA surface modification into sensitization liquid for a period of time, taking out the matrix samples and then flushing the matrix samples with deionized water to obtain matrix samples such as sensitized carbon fiber cloth and the like;

(4) Matrix activation, namely immersing matrix samples such as sensitized carbon fiber cloth and the like into an activating solution for a period of time, taking out the samples, flushing the samples with deionized water, and then preserving the samples in ultrapure water for standby;

(5) And (3) chemical plating, namely placing the activated substrate sample into chemical plating solution, keeping constant temperature for reacting for a certain time, taking out the chemically plated sample, cleaning and drying to obtain the composite three-dimensional current collector.

In the step (1), the roughening solution includes, but is not limited to, a mixed solution of concentrated sulfuric acid and concentrated nitric acid, a mixed solution of hydrogen peroxide and concentrated sulfuric acid, a mixed solution of chromic acid and sulfuric acid, etc., and in some embodiments of the present invention, a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1 is used. Preferably, the carbon fiber cloth is soaked in the roughening liquid, is heated at 100 ℃ in a blast oven for roughening treatment by 12 h, is cooled, is taken out, is washed to be neutral by deionized water, and is dried in a vacuum drying oven.

In the step (2), the polydopamine grafting is to soak the roughened matrix sample after ultrasonic cleaning in a grafting solution, stir for a period of time in a dark place to carry out surface modification, then take out the matrix sample with PDA surface modification, clean and dry. In some embodiments of the present invention, the ultrasonic cleaning is to sequentially add acetone, ethanol and ultrapure water to the roughened substrate sample for ultrasonic cleaning, and finally clean the substrate sample with ultrapure water for 2 times, and soak the substrate sample in the ultrapure water. During grafting, a substrate sample is placed into a grafting solution, wherein the grafting solution contains 0.01-0.03 g/L dopamine hydrochloride (DA) and Tris buffer solution (5-15 mM/L, pH is approximately equal to 8.5), and the mixture is stirred for 1-4 hours in a dark place. And then taking out the substrate sample with the PDA surface modified, cleaning the substrate sample with ultrapure water and absolute ethyl alcohol for a plurality of times, and vacuum drying the substrate sample to obtain the substrate sample with the PDA surface modified.

In the step (3), preferably, the sensitization solution is 5-30 g/L SnCl ₂·2H₂ O/HCl aqueous solution, and the components of the sensitization solution are 5-30 g/L SnCl ₂·2H₂ O and 37% HCl 50 ml/L. In some embodiments of the invention, the substrate sample after PDA surface modification is immersed in 5-30 g/L SnCl ₂·2H₂ O/HCl aqueous solution for 5-30 min at 20-50 ℃, taken out and rinsed with flowing deionized water for three minutes, thus obtaining the sensitized substrate sample.

In the step (4), the activating solution includes, but is not limited to, pdCl ₂/HCl aqueous solution, agNO ₃ solution and the like. Preferably, the activating solution is PdCl ₂/HCl aqueous solution, and the components of the activating solution are 0.2-2 g/L PdCl ₂ and 37% HCl 50 ml/L. In some embodiments of the invention, the sensitized substrate sample is immersed in a PdCl ₂/HCl aqueous solution with the concentration of 0.2-2 g/L for 5-30 min at the temperature of 20-50 ℃, taken out, washed with deionized water for a plurality of times, and then stored in ultrapure water for standby.

In the step (5), preferably, the electroless plating solution is an electroless copper plating solution, and the preparation process of the electroless copper plating solution comprises the steps of respectively weighing copper salt, complexing agent and stabilizer, dissolving in deionized water, uniformly stirring at a certain speed to prepare a solution, heating to a certain temperature, and adding a reducing agent into the mixed solution until the solution is fully dissolved. Wherein the copper salt comprises but is not limited to copper sulfate, copper chloride, copper acetate, copper nitrate and the like, the complexing agent comprises but is not limited to disodium ethylenediamine tetraacetate, sodium potassium tartrate, trisodium citrate and the like, the stabilizer comprises but is not limited to triethanolamine, thiosulfate, potassium ferrocyanide trihydrate, 2-amino-5-mercapto-1, 3, 4-thiadiazole and the like, and the reducing agent comprises but is not limited to dimethylaminoborane, formaldehyde, glyoxylic acid, sodium hypophosphite, sodium borohydride, aminoborane, hydrazine hydrate and the like. In some embodiments of the invention, the copper source in the chemical plating solution is copper sulfate pentahydrate with the concentration of 1.0-2.0 g/L, the complexing agent is disodium ethylenediamine tetraacetate with the concentration of 2.0-2.5 g/L, the stabilizer is triethanolamine with the concentration of 11-15 g/L, and the reducing agent is dimethylaminoborane with the concentration of 8-12 g/L.

Preferably, the electroless plating reaction temperature is 25-60 ℃ and the electroless 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 the temperature range of 500-600 ℃.

The invention also provides a metal negative electrode, which comprises the composite three-dimensional current collector and metals such as magnesium, zinc, lithium, sodium, potassium, calcium and the like electrodeposited on the composite three-dimensional current collector. Preferably a magnesium metal negative electrode or a zinc metal negative electrode, comprising the composite three-dimensional current collector prepared by the method and magnesium metal or zinc metal electrodeposited on the composite three-dimensional current collector.

Preferably, the surface of the composite three-dimensional current collector is deposited with 0.2-8 mAh/cm ² of magnesium or zinc and other metals under the current density of 0.1-8 mA/cm ², and the magnesium or zinc and other metal negative electrode is obtained.

The invention also provides application of the composite three-dimensional current collector and the metal negative electrode in a metal secondary battery, preferably application of the magnesium metal negative electrode in the magnesium metal secondary battery. Thus, a metal secondary battery whose negative electrode is the metal negative electrode was obtained.

The invention has the beneficial effects that:

(1) The invention provides a method for preparing a composite three-dimensional current collector by depositing metal on a light nonmetallic three-dimensional framework substrate through electroless plating, and the composite three-dimensional current collector such as copper/carbon fiber cloth is prepared. The chemical plating process has low cost, convenient operation, stable chemical plating solution taking dimethylamino borane and the like as reducing agents and long service life, and the prepared copper plating layer of the copper/carbon fiber cloth composite three-dimensional current collector is uniformly coated on each carbon fiber, and the plating layer is uniform and compact and has good binding force with a carbon fiber substrate.

(2) The invention provides a larger buffer space for metal deposition of Mg, zn and the like by utilizing the porous structure and large specific surface area of the composite three-dimensional current collector of copper/carbon fiber cloth and the like, and adjusts the nucleation and growth process of the metal of Mg, zn and the like by utilizing the metal coating of Cu and the like in electrodeposition so as to induce the metal to uniformly grow along the three-dimensional skeleton fiber.

(3) The battery cathode composed of the copper/carbon fiber cloth and other composite three-dimensional current collector and Mg, zn and other metals has excellent charge and discharge performance, so that the cycle stability, the cycle life and the coulomb efficiency of the battery are improved.

(4) The battery cathode consists of the composite three-dimensional current collector such as copper/carbon fiber cloth and metals such as Mg, zn and the like, and the metals are uniformly deposited on the three-dimensional framework fibers, so that the stability of an electrode interface can be enhanced, dendrite growth can be reduced, the electrodeposition overpotential of the metals can be reduced, and the service life of the metal cathode can be prolonged. Therefore, the deposition/stripping behavior of the metal is obviously improved when the thin diaphragm is used, and a new idea is provided for pushing the metal secondary batteries with high energy density such as Mg, zn and the like to be put into practical use.

Drawings

FIG. 1 is a scanning electron microscope result of Mg deposited on a carbon fiber cloth (CC) substrate in comparative example 1.

Fig. 2 is the overpotential and cyclic stability test results for the assembled half-cell of comparative example 1, where a and b are the first pass potential test results for Mg negative and CC positive half-cells (designated Mg// CC half-cells) at current densities of 1 mA/cm ² and 8 mA/cm ², respectively, and c is the cyclic stability test result for Mg// CC half-cells at current densities of 1 mA/cm ².

Fig. 3 is a scanning electron microscope result of Mg deposited on the copper sheet in comparative example 2.

Fig. 4 is the overpotential and cyclic stability test results for the assembled half cell of comparative example 2, where a and b are the first pass potential test results for Mg negative and Cu positive half cells (designated Mg// Cu half cell) at current densities of 1 mA/cm ² and 8 mA/cm ², respectively, and c is the cyclic stability test result for Mg// Cu half cell at current densities of 1 mA/cm ².

Fig. 5 is a Scanning Electron Microscope (SEM) photograph of the carbon fiber cloth (CC) and cu@cc composite three-dimensional current collector in example 1, wherein a is a Scanning Electron Microscope (SEM) photograph of the carbon fiber cloth, b is a scanning electron microscope photograph of the cu@cc composite three-dimensional current collector, and c and d are SEM and EDS spectra of the cu@cc composite three-dimensional current collector.

Fig. 6 is a scanning electron microscope result of Mg deposited on the cu@cc composite three-dimensional current collector in example 1.

Fig. 7 is the overpotential and cycling stability test results for the assembled half cell of example 1, where a and b are the test results for the first pass overpotential at 1 mA/cm ² and 8 mA/cm ² current densities for the Mg negative electrode, cu@cc positive electrode half cell (designated Mg// cu@cc half cell), and c is the cycling stability test result for the Mg// cu@cc half cell at 1 mA/cm ² current density, respectively.

Fig. 8 is the coulombic efficiency and charge and discharge results of the assembled half-cells of the three current collectors of example 6, wherein a shows the coulombic efficiencies 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 1 st and 100 th turns, respectively.

Fig. 9 is a voltage versus time plot for three current collector assembled half cells of example 6, wherein a, b, c correspond to CC, cu, and cu@cc composite three-dimensional current collectors, respectively.

Fig. 10 is the coulombic efficiency results for the Zn half-cells assembled with three current collectors in example 9.

Fig. 11 is a graph showing the discharge capacity and coulombic efficiency results of assembled full cells using three current collectors as negative electrodes after magnesium pre-deposition in example 10.

Fig. 12 is the discharge capacity and coulombic efficiency results of assembled full cells using three current collectors as negative electrodes after pre-depositing magnesium in example 11.

Fig. 13 is the discharge capacity and coulombic efficiency results of assembled soft-pack cells, using cu@cc as the negative electrode after pre-depositing magnesium in example 12, where a and b correspond to the glass fiber filter paper separator and Celgard separator, respectively.

Detailed Description

The present invention will be described in detail by way of specific examples, but the present invention may be practiced by other methods and is not limited to the following examples. Accordingly, the scope of the present invention is not limited by the following examples. The experimental methods, reagents and materials described in the examples, unless otherwise indicated, were all those conventionally used or were all commercially available. The experimental apparatus and equipment in the examples are all parameters selected by manufacturers unless otherwise specified.

Comparative example 1

And (3) treating with a sulfuric acid and nitric acid mixed solution, taking pure carbon fiber cloth (CC for short) which is not subjected to chemical plating modification as a positive electrode, and taking a metal Mg sheet as a negative electrode to assemble the half-cell. Mg metal is deposited on the carbon fiber cloth by electrochemical means. After depositing 8 mAh/cm ² of magnesium metal at a current density of 0.1 mA/cm ², it was disassembled and the microstructure of the Mg deposition on the carbon fiber cloth is shown in fig. 1. The carbon fiber cloth has the advantages that the Mg deposition layer on the three-dimensional current collector skeleton of the carbon fiber cloth is uneven, and grows continuously along a small part of nucleation sites to generate massive Mg, which indicates that the carbon fiber cloth is of a three-dimensional porous structure, but lacks the induced deposition effect of the surface coating, so that the carbon fiber cloth has poor nucleophilicity with Mg metal and poor electrodeposition controllability of the Mg metal on the carbon fiber cloth substrate. In FIG. 2, a and b are the test results of the first pass potentials of the Mg negative electrode obtained by the method, and the CC positive electrode half cell (named as Mg// CC half cell) at the current densities of 1mA/cm ² and 8 mA/cm ², respectively, and it can be seen that the over potentials of the negative electrode at the current densities of 1mA/cm ² and 8 mA/cm ² are relatively large (138 mV and 437 mV, respectively). As can be seen from the cycling stability diagram (c in FIG. 2) of the Mg// CC half-cell at a current density of 1mA/cm ², the cycling stability of the cell is poor and the voltage of the whole process is large.

Comparative example 2

The metal Cu sheet was used as a positive electrode, and the metal Mg sheet was used as a negative electrode to assemble a half cell (designated as Mg// Cu half cell). Mg metal is deposited on the copper sheet by electrochemical means. After depositing 8 mAh/cm ² Mg metal at a current density of 0.1 mA/cm ², it was disassembled and the microstructure of the Mg deposit on the copper sheet is shown in fig. 3. The Mg deposition layer on the copper skeleton can only be deposited on the surface of copper metal to generate massive Mg, which shows that the copper sheet has good nucleophilicity with Mg, but has a planar structure, no gap in the middle and can not provide enough nucleation space for the electrodeposition of Mg metal, so that the electrodeposition process of Mg metal can continuously grow along part of nucleation sites. In FIG. 4, a and b are the results of the first pass potential test of the Mg// Cu half-cell obtained by the method above at current densities of 1mA/cm ² and 8 mA/cm ², respectively, and it can be seen that the overpotential of the negative electrodes 1mA/cm ² and 8 mA/cm ² is relatively large (188 mV and 427 mV, respectively). As can be seen from the cycling stability graph (c in FIG. 4) of the Mg// Cu half cell at a current density of 1mA/cm ², the cycling stability of the cell is poor and the voltage of the whole process is large.

Example 1

Preparing a Cu@CC composite three-dimensional current collector by electroless plating:

(1) Substrate pretreatment

Placing the purchased three-dimensional current collector of the carbon fiber cloth into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with the volume ratio of 1:1, heating and soaking the carbon fiber cloth in a blast drying oven at 100 ℃ for 12 h ℃, stopping heating after the completion, cooling to room temperature, and taking out the carbon fiber cloth. And repeatedly washing with deionized water for several times, and drying in a vacuum drying oven at 60 ℃ to obtain a hydrophilic carbon fiber cloth sample.

Cutting the acid-treated sample into a certain size, sequentially adding acetone, ethanol and ultrapure water for ultrasonic cleaning, and finally cleaning with ultrapure water for 2 times, and soaking in the ultrapure water. After this time, it was placed in a flask, 200 mL of Tris buffer (10 mM/L, pH. Apprxeq.8.5) and 0.02 g/L dopamine hydrochloride were added and stirred in the dark for 2 h. And then taking out the polydopamine surface-modified carbon fiber cloth sample, washing the sample with ultrapure water and absolute ethyl alcohol for 3 times, and vacuum drying to graft polydopamine on the surface of the carbon fiber cloth.

Immersing the carbon fiber cloth sample grafted with the PDA into 10 g/L SnCl ₂·2H₂ O/HCl aqueous solution, immersing the sample in the aqueous solution at 25 ℃ for 15 min, taking out the sample, washing the sample with flowing deionized water for three minutes, and adsorbing hydrolyzed tin ions on the surface of a substrate to obtain a sensitized carbon fiber cloth sample. Immersing the sensitized carbon fiber cloth sample into 0.2 g/L PdCl ₂/HCl aqueous solution at 25 ℃ for 15 min, taking out the sample, flushing with deionized water for three times, successfully introducing Pd active sites onto the surface of the carbon fiber cloth, and then preserving the pretreated carbon fiber cloth in ultrapure water for later use.

(2) Electroless Cu plating

1.5 G copper sulfate pentahydrate, 2.35 g ethylene diamine tetraacetic acid disodium and 11.3 g triethanolamine are respectively weighed and dissolved in deionized water of 1L, 500 r/min is stirred to prepare uniform mixed solution, 200 mL plating solution is taken in an electroless plating tank and heated to 50 ℃, and then 0.236 g reducing agent dimethylaminoborane is added into the solution and stirred until the solution is fully dissolved.

And (3) placing the activated carbon fiber cloth sample into the chemical plating solution, keeping the constant temperature of 50 ℃ for reaction for 30min, taking out the chemically plated sample, changing the color of the chemically plated sample from black of pure carbon fiber cloth to mauve, sequentially flushing the chemically plated sample with deionized water and absolute ethyl alcohol for three times, and drying the chemically plated sample to obtain the composite three-dimensional current collector. As can be seen from a scanning electron microscope and an EDS (fig. 5), nano-scale particles with uniform size are uniformly covered on the carbon fiber cloth, a plating layer is mainly Cu element, and the chemically plated Cu@CC material still maintains a three-dimensional hollow porous structure.

(3) Assembled half cell and performance test

The metal Mg sheet is used as a negative electrode, glass fiber filter paper is used as a diaphragm, a Cu@CC composite three-dimensional current collector (punched into a wafer with the diameter of 19 mm) is used as a positive electrode, an APC solution (0.4M (MgPhCl) ₂-AlCl₃/THF) is used as an electrolyte to assemble a half cell (named as a Mg// Cu@CC half cell), and Mg metal is deposited on the Cu@CC composite three-dimensional current collector through an electrochemical method. After depositing 8 mAh/cm ² of magnesium metal at a current density of 0.1 mA/cm ², it was disassembled and the microstructure of the deposit of Mg on cu@cc is shown in fig. 6. As can be seen from the electron microscope results, mg metal grows along the fibers at Cu@CC, is uniformly distributed on the gaps and the surfaces of the fibers, and does not generate massive Mg. The Cu@CC composite three-dimensional current collector prepared by chemically plating the modified carbon fiber cloth substrate is characterized in that a three-dimensional porous structure of a substrate is reserved to provide enough space for deposition of Mg metal, and meanwhile, a surface modified metal copper plating layer is good in nucleophilicity with Mg, so that uniform electrodeposition of the Mg metal on the three-dimensional current collector can be induced. In FIG. 7, a and b are the first pass potentials of the Mg// Cu@CC half cells obtained by the method described above at current densities of 1mA/cm ² and 8 mA/cm ², respectively, and it can be seen that the overpotential at current densities of the above-described cathodes 1mA/cm ² and 8 mA/cm ² are both small (122 mV and 382 mV, respectively). As can be seen from the cyclic stability graph (c in FIG. 7) of the Mg// Cu@CC half cell at a current density of 1mA/cm ², the voltage polarization of magnesium deposited/dissolved on the Cu@CC is small, and the assembled Mg// Cu@CC half cell can stably circulate for more than 1000 circles, and the average coulombic efficiency is 99.80%.

Example 2

Other conditions were the same as in example 1, except that the reaction temperature of the electroless modified carbon fiber cloth was 20 ℃. The Mg// cu@cc half cell was cycled steadily for 1400 cycles at a current density of 1 mA/cm ² with an average coulombic efficiency of 99.78%.

Example 3

Other conditions were the same as in example 1, except that the reaction temperature of the electroless modified carbon fiber cloth was 30 ℃. The cu@cc and Mg metal negative electrode obtained under this condition were assembled into a half cell and the electrochemical performance of the cell was tested, the Mg// cu@cc half cell was stably cycled 1390 cycles at a current density of 1mA/cm ², and the average coulombic efficiency was 99.47%.

Example 4

Other conditions were the same as in example 1, except that the reaction temperature of the electroless modified carbon fiber cloth was 40 ℃. The cu@cc and Mg metal negative electrode obtained under this condition were assembled into a half cell and the electrochemical performance of the cell was tested, the Mg// cu@cc half cell was cycled for 1390 cycles at a current density of 1 mA/cm ², and the average coulombic efficiency was 99.81%.

Example 5

Other conditions were the same as in example 1, except that the reaction time of electroless modified carbon fiber cloth was 10 min. The cu@cc and Mg metal negative electrode obtained under this condition were assembled into a half cell and the electrochemical performance of the cell was tested, the Mg// cu@cc half cell was cycled steadily for 1400 cycles at a current density of 1mA/cm ², and the average coulombic efficiency was 99.61%.

Example 6

Other conditions were the same as in example 1 except that the separator was replaced with a thinner Celgard separator, a metal Mg sheet was used as the negative electrode, cu, CC and cu@cc composite three-dimensional current collectors were used as the positive electrodes, respectively, and half cells were assembled for electrochemical testing. The charge-discharge cycle test was performed at a current density of 1 mA/cm ². The coulombic efficiency contrast and charge-discharge curve pair of half cells composed of three positive electrode materials are shown in fig. 8. As can be seen from fig. 8a, the Mg// cu@cc half cell can stably circulate for more than 130 circles under high coulombic efficiency, while the coulombic efficiency of the Mg// CC half cell can be drastically attenuated within 30 circles, and the Mg// Cu half cell is short-circuited within 10 circles, so that the circulation cannot be continued. In addition, the metal plating layer is introduced to the surface of the three-dimensional reticular fiber, so that uniform electrodeposition of Mg is effectively induced, and the coulomb efficiency and the cycle life of the Mg// Cu@CC half cell are further improved. The charge and discharge curves shown in fig. 8b and c also show that the Mg// cu@cc half cell has highly reversible charge and discharge properties, and the voltage polarization is significantly reduced. As can be seen from the cycling stability graph at a current density of 1 mA/cm ² (fig. 9), the Mg// cu@cc half cell maintains excellent cycling stability at higher current densities even with a thinner Celgard separator.

Example 7

Other conditions were the same as in example 1 except that the separator was replaced with a thinner Celgard separator and the electroless Cu deposition time was 3 min, and since the reaction time was shorter, the carbon fibers were not completely covered by the Cu plating, and part of the fibers were bare resulting in uneven magnesium deposition. And (3) taking the Cu@CC composite three-dimensional current collector as an anode, assembling a half cell with a magnesium metal anode, and performing charge-discharge cycle test under the current density of 0.1 mA/cm ². Mg// cu@cc half cell cycles 980 turns with an average coulombic efficiency of 97.75%.

Example 8

Other conditions were the same as in example 1 except that the membrane was replaced with a thinner Celgard membrane and the electroless Cu deposition time was 5min. And (3) taking the Cu@CC composite three-dimensional current collector as an anode, assembling a half cell with a magnesium metal anode, and performing charge-discharge cycle test under the current density of 0.1 mA/cm ². The Mg// Cu@CC half cell is cycled 980 turns, and the coulombic efficiency is 99.55%.

Example 9

Other conditions are the same as those of example 1, except that a metal Zn sheet is selected as the negative electrode, a ZnSO ₄ aqueous solution is used as the electrolyte, and the electrolyte is respectively used as the positive electrode to assemble a half cell (named as Zn// CC half cell, zn// Cu half cell and Zn// Cu@CC half cell in sequence). The Zn// Cu@CC half cell coulombic efficiencies are shown in FIG. 10. As can be seen from fig. 10, at a large current density of 8.0 mA/cm ², the Zn// cu@cc half cell can be cycled stably for nearly 50 cycles at high coulombic efficiency, while the Zn// Cu half cell cannot be cycled stably due to short circuit within 30 cycles, and the Zn// CC half cell is shorted within 15 cycles. The Cu@CC composite three-dimensional current collector is also beneficial to improving the cycle stability and the service life of a Zn battery.

Example 10

Other conditions were the same as in example 1 except that after half cell assembly was completed, magnesium (designated as mg@cu, mg@cc and mg@cu@cc, respectively) of 2 mAh/cm ² was deposited on the Cu, CC and cu@cc composite current collectors at a current density of 0.1 mA/cm ², and then disassembled, and then the three current collectors on which the magnesium was deposited were cleaned with tetrahydrofuran, and after the tetrahydrofuran was volatilized clean, used as a full cell negative electrode. mo ₆S₈, Fully mixing a conductive agent (Super P) and a binder (PVDF) according to a mass ratio of 7:2:1, uniformly coating on a Ni foil, vacuum drying in a vacuum oven at 60 ℃ for 12h ℃, and then flushing into an electrode wafer with a diameter of 1: 1 cm to serve as a full battery anode, wherein the loading amount is 1-1.5 mg, whatman glass fiber filter paper is used as a diaphragm, and an APC (200 mu L of 0.4M (MgPhCl) ₂-AlCl₃/THF) solution is used as an electrolyte to assemble the full battery. The electrochemical performance of the three current collectors mg@cu, mg@cc and mg@cu@cc after pre-deposition of 2 mAh/cm ² magnesium as negative electrodes, respectively, assembled into full cells (designated as mg@cu// Mo ₆S₈ full cell, mg@cc// Mo ₆S₈ full cell and mg@cu@cc// Mo ₆S₈ full cell, respectively) is shown in fig. 11. As can be seen from fig. 11, the mg@cu@cc// Mo ₆S₈ full cell assembled by the cu@cc composite three-dimensional current collector can stably circulate for 450 turns with an average coulombic efficiency of 99.24%, and the specific discharge capacity of the Mo ₆S₈ cathode at 450 turns is about 71.6 mAh/g. The specific discharge capacity of the Mg@Cu// Mo ₆S₈ full cell obtained by copper foil assembly at 450 circles is 70.3 mAh/g. However, the mg@cc// Mo ₆S₈ full cell assembled from CC undergoes rapid capacity decay after 130 cycles, which may be caused by poor nucleophilicity of Mg and carbon fiber cloth.

Example 11

Other conditions were the same as in example 1 except that after half cell assembly was completed, after 2 mAh/cm ² Mg metal (designated mg@cu, mg@cc and mg@cu@cc, respectively) was deposited on the Cu, CC and cu@cc composite current collectors at a current density of 0.1 mA/cm ², they were disassembled, and then the three current collectors on which magnesium was deposited were cleaned with tetrahydrofuran and used as full cell cathodes after the tetrahydrofuran was volatilized clean. mo ₆S₈, Fully mixing a conductive agent (Super P) and a binder (PVDF) according to a mass ratio of 7:2:1, uniformly coating on a Ni foil, vacuum drying in a vacuum oven at 60 ℃ for 12h ℃, punching into an electrode wafer with a diameter of 1:1 cm to serve as a full battery anode, carrying 1-1.5 mg, taking a thinner Celgard 2325 as a diaphragm, and using an APC (60 mu L0.4M (MgPhCl) ₂-AlCl₃/THF) solution as an electrolyte to assemble a full battery (named as Mg@Cu// Mo ₆S₈ full battery respectively, respectively, Mg@cc// Mo ₆S₈ full cell and mg@cu@cc// Mo ₆S₈ full cell). Electrochemical performance tests show that the capacity decay of the Mg@CC// Mo ₆S₈ full cell assembled by the CC three-dimensional current collector occurs firstly, and the discharge capacity is almost 0 after 90 circles. In addition, the non-uniformity of Mg metal deposition on the two-dimensional copper foil also causes capacity fade after long cycling of the mg@cu// Mo ₆S₈ full cell assembled with the copper foil as a current collector, and eventually short circuit at 270 turns. The discharge capacity of the Mg@Cu@CC// Mo ₆S₈ full battery assembled by the Cu@CC composite three-dimensional current collector after 450 circles can still reach 72.7 mAh/g, the capacity retention rate is 96.3%, and the cycle average coulombic efficiency is 99.60% (figure 12). These results demonstrate that cu@cc exhibits advantages in Mg metal deposition/dissolution processes, as well as high suitability for Mo ₆S₈ cathodes.

Example 12

Other conditions were the same as in example 1 except that the electroless plating prepared cu@cc composite three-dimensional current collector was first assembled into a soft-pack half-cell (designated Mg// cu@cc soft-pack half-cell), specifically prepared by pre-depositing 2.0 mAh/cm ² Mg metal on the cu@cc current collector at a current density of 0.1 mA/cm ² with a metallic Mg sheet as the negative electrode, celgard 2325 as the separator, cu@cc as the positive electrode, APC solution (0.4M (MgPhCl) ₂-AlCl₃/THF, purchased from doc & gt) as the electrolyte. And then the battery is disassembled, the premagnesized Cu@CC is cleaned by THF, and after the THF is completely volatilized, the Cu@CC after magnesium deposition is obtained and is named as Mg@Cu@CC.

Mg@cu@cc after magnesium pre-deposition was used as a full cell negative electrode, mo ₆S₈, a conductive agent (Super P) and a binder (PVDF) were thoroughly mixed in a mass ratio of 7:2:1, uniformly coated on a Ni foil, and vacuum-dried in a vacuum oven at 60 ℃ for 12h to be used as a full cell positive electrode. Soft-pack full cells (named Mg// cu@cc soft-pack full cells) were assembled using Whatman glass fiber filter paper (Mo ₆S₈ active material loading of 0.585 Mg/cm ²) and thinner Celgard 2325 (Mo ₆S₈ active material loading of 0.429 Mg/cm ²) as separator, respectively, and APC solution (0.4M (MgPhCl) ₂-AlCl₃/THF) as electrolyte. The full cell with the glass fiber filter paper as the diaphragm was stably cycled for 100 circles, and the discharge specific capacity of the Mo ₆S₈ cathode at the 100 th circle was about 54.4 mAh/g, and the capacity retention rate was 93.96% (a in FIG. 13). And even if a thinner Celgard 2325 is adopted as a diaphragm, the discharge capacity of the soft-package full battery assembled by the Cu@CC composite three-dimensional current collector after 100 circles can still reach 69.9mAh/g, and the capacity retention rate is 93.32% (b in fig. 13). Experimental results show that the Cu@CC composite three-dimensional current collector can be used as a negative electrode carrier of a soft package battery, and the battery can still stably circulate and has higher specific discharge capacity even under the condition of a thinner diaphragm (Celgard 2325).

Preferred embodiments of the present invention and experimental verification are described in detail above. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

1. The composite three-dimensional current collector is characterized by comprising a non-metal three-dimensional skeleton matrix and a metal coating uniformly distributed on the surface of the non-metal three-dimensional skeleton matrix through chemical plating, wherein the non-metal three-dimensional skeleton matrix is made of three-dimensional porous materials and is selected from one or more of carbon fiber cloth, polymer diaphragms, paper or polymer foams, and the metal of the metal coating is selected from Cu, ag, co, ni, sn and Bi.

2. The composite three-dimensional current collector of claim 1, wherein the non-metal three-dimensional skeleton matrix is carbon fiber cloth, the metal coating is a Cu coating, and the thickness is 1-5 μm.

3. The method for preparing the composite three-dimensional current collector according to claim 1 or 2, comprising the following steps:

1) Coarsening a matrix, namely soaking a non-metal three-dimensional framework matrix material in coarsening liquid, heating for a period of time to coarsen, cooling to room temperature, taking out the matrix material, washing with deionized water, and drying;

2) Cutting the roughened matrix material into a required size, and performing polydopamine grafting after ultrasonic cleaning to obtain a polydopamine surface-modified matrix;

3) The substrate sensitization, namely immersing the substrate with the polydopamine surface modified into sensitization liquid for a period of time, taking out the substrate, and flushing the substrate with deionized water to obtain a sensitized substrate;

4) Activating the matrix, namely immersing the sensitized matrix into an activating solution for a period of time, taking out, and washing with deionized water to obtain an activated matrix;

5) And (3) chemical plating, namely placing the activated matrix into chemical plating solution, keeping constant temperature for reacting for a certain time, taking out the matrix after chemical plating, cleaning and drying to obtain the composite three-dimensional current collector.

4. The method according to claim 3, wherein the roughening liquid 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.

5. The method of claim 3, wherein the polydopamine grafting in step 2) is performed by immersing the substrate in a grafting solution, stirring for a period of time in the absence of light, then removing the substrate, washing, and drying, wherein the grafting solution is Tris buffer solution containing dopamine hydrochloride.

6. The preparation method according to claim 3, wherein the sensitization solution in step 3) is SnCl ₂·2H₂ O/HCl aqueous solution, the substrate is immersed in the sensitization solution at 20-50 ℃ for 5-30 min, the activation solution in step 4) is PdCl ₂/HCl aqueous solution or AgNO ₃ solution, and the substrate is immersed in the activation solution at 20-50 ℃ for 5-30 min.

7. The method of claim 3, wherein the electroless plating solution in step 5) is an electroless copper plating solution, and is prepared by dissolving copper salt, complexing agent and stabilizer in deionized water, stirring uniformly and heating, and adding 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 ethylenediamine tetraacetate, sodium potassium 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, and the electroless plating reaction temperature is 25-60 ℃ and the electroless plating reaction time is 5-120 min.

8. A metal negative electrode comprising the composite three-dimensional current collector of claim 1 or 2 and a metal electrodeposited on the composite three-dimensional current collector, wherein the metal is magnesium, zinc, lithium, sodium, potassium or calcium.

9. A metal secondary battery, wherein the negative electrode of the metal secondary battery is the metal negative electrode of claim 8.