Three-dimensional porous copper and preparation method therefor

Abstract

The present application discloses three-dimensional porous copper and a preparation method therefor. The preparation method for the three-dimensional porous copper comprises the following steps: providing a copper alloy matrix, wherein the copper alloy matrix comprises a Cu element and a non-Cu metallic element, and the standard electrode potential of the non-Cu metallic element is less than that of the Cu element; providing a corrosive liquid, wherein the corrosive liquid comprises a neutral salt, a weakly acidic complexing agent, and a solvent, the molar concentration of the neutral salt is recorded as C1, the molar concentration of the weakly acidic complexing agent is recorded as C2, the molar concentrations are both in the unit of mol / L, 0.04≤C2 / C1≤0.60, and C2 is less than or equal to 0.20 mol / L; and using the corrosive liquid as an electrolyte to perform electrochemical corrosion on the copper alloy matrix so as to obtain three-dimensional porous copper. The present application can improve the porosity of three-dimensional porous copper, and can also reduce cracks in the three-dimensional porous copper.

Description

Three-dimensional porous copper and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311278003.7, filed on September 28, 2023, entitled “Three-dimensional porous copper and its preparation method,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a three-dimensional porous copper and a preparation method thereof. Background Art

[0004] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in consumer electronics, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. The negative electrode is an important component of the battery, which affects the performance of the battery. At present, the negative electrode of the battery is usually formed by arranging a negative electrode film layer including negative electrode active materials such as graphite on a copper foil. However, with the continuous expansion of battery application fields, people are more and more demanding on batteries with high energy density. Metal batteries and negative electrode-free batteries can have high energy density because they do not use negative electrode film layers. However, the uneven deposition of metals and dendrite problems restrict the development of metal batteries and negative electrode-free batteries. As an important component of metal batteries and negative electrode-free batteries, the negative electrode current collector is expected to alleviate the uneven deposition of metals and dendrite problems by improving it.

[0005] Three-dimensional porous copper has the advantages of light weight and large specific surface area. When used in batteries, it can improve the energy density of the battery and improve the reliability of the battery. Especially when used in metal batteries and negative electrode-free batteries, when the negative electrode adopts a three-dimensional porous copper structure, it can also reduce the problem of uneven metal deposition and dendrite problems. Electrochemical corrosion (i.e., electrochemical dealloying) of the copper alloy matrix is ​​a powerful method for preparing a three-dimensional porous copper structure. At present, the three-dimensional porous copper structure prepared by the dealloying process has problems such as low porosity and many surface cracks. Therefore, when it is used in the battery current collector, it will affect the performance of the battery.

[0006] The above statements are only used to provide background information related to the present application and do not necessarily constitute prior art.

[0007] Summary of the Invention

[0008] The present application provides a three-dimensional porous copper and a preparation method thereof, which can improve the porosity of the three-dimensional porous copper and reduce cracks in the three-dimensional porous copper.

[0009] In a first aspect, the present application provides a method for preparing three-dimensional porous copper, comprising the following steps: providing a copper alloy substrate, wherein the copper alloy substrate comprises a Cu element and a non-Cu metal element, wherein the standard electrode potential of the non-Cu metal element is less than the standard electrode potential of the Cu element; providing a corrosive solution, wherein the corrosive solution comprises a neutral salt, a weakly acidic chelating agent, and a solvent, wherein the molar concentration of the neutral salt is denoted as C1, and the molar concentration of the weakly acidic chelating agent is denoted as C2, both in mol / L, 0.04≤C2 / C1≤0.60, and C2 is less than or equal to 0.20 mol / L; and electrochemically corroding the copper alloy substrate using the corrosive solution as an electrolyte to obtain three-dimensional porous copper.

[0010] The etching solution provided in the embodiments of the present application can provide a stable corrosion environment, reduce the precipitation reaction of metal ions dissolved during the electrochemical dealloying process, thereby reducing the pore blocking and surface passivation problems of the prepared three-dimensional porous copper, and further improve the porosity of the prepared three-dimensional porous copper structure; at the same time, it can also reduce crack formation.

[0011] The three-dimensional porous copper obtained by the preparation method provided in the embodiment of the present application can have a high porosity and fewer cracks, thereby improving the electrochemical performance of the battery when used in a battery current collector.

[0012] In some embodiments, 0.10≤C2 / C1≤0.24. By further adjusting C2 / C1 within the above range, the porosity of the prepared three-dimensional porous copper structure can be further increased, and crack formation can be reduced.

[0013] In some embodiments, C1 is 0.2 mol / L-2.0 mol / L, and optionally 0.5 mol / L-1.5 mol / L. By further adjusting the molar concentration of the neutral salt C1 within the above range, the electrochemical dealloying reaction rate can be increased, the porosity of the prepared three-dimensional porous copper structure can be increased, and crack formation can be reduced.

[0014] In some embodiments, C2 is 0.04 mol / L-0.20 mol / L, and optionally 0.08 mol / L-0.16 mol / L. By further adjusting the molar concentration C2 of the weakly acidic complexing agent within the above range, the pore blocking and surface passivation problems of the prepared three-dimensional porous copper can be further reduced, the porosity of the prepared three-dimensional porous copper structure can be increased, and the formation of hydrogen embrittlement cracks can be further reduced.

[0015] In some embodiments, the neutral salt includes one or more of sodium salt and potassium salt, and may optionally include one or more of sodium chloride and potassium chloride.

[0016] In some embodiments, the weakly acidic chelating agent comprises one or more of a dicarboxylic acid, a polycarboxylic acid, and their respective salts, and may optionally comprise one or more of citric acid, isocitric acid, malic acid, tartaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and their respective salts. Optionally, the salt comprises one or more of a sodium salt, a potassium salt, a sodium-potassium salt, and an ammonium salt.

[0017] By further adjusting the weakly acidic complexing agent within the above range, the porosity of the prepared three-dimensional porous copper structure can be further improved, and crack formation can also be reduced.

[0018] In some embodiments, the solvent comprises water.

[0019] In some embodiments, the copper alloy substrate is electrochemically corroded using a three-electrode system with the corrosive solution as the electrolyte, the copper alloy substrate being the working electrode, the AgCl / Ag electrode being the reference electrode, and the platinum electrode being the counter electrode.

[0020] In some embodiments, the voltage between the copper alloy substrate and the reference electrode is -0.70V to -0.15V.

[0021] In some embodiments, the temperature for electrochemically corroding the copper alloy substrate using the corrosive solution as the electrolyte is 10° C.-65° C., and can be optionally 20° C.-35° C.

[0022] In some embodiments, the copper alloy substrate is electrochemically corroded using the corrosive solution as the electrolyte for a period of 3 hours to 24 hours, optionally 6 hours to 10 hours.

[0023] In some embodiments, the copper alloy substrate is in the form of a sheet or foil.

[0024] In some embodiments, the non-Cu metal element includes one or more of Mn, Zn, Ni, Al, and Fe.

[0025] In some embodiments, the preparation method further includes the step of rinsing the copper alloy substrate with a corrosive solution.

[0026] In some embodiments, the preparation method further comprises the steps of: washing the electrochemically etched three-dimensional porous copper with water, washing with alcohol, and drying the electrochemically etched three-dimensional porous copper. The water washing can remove soluble salts in the three-dimensional porous copper structure, and the alcohol washing can remove residual moisture in the three-dimensional porous copper structure.

[0027] In some embodiments, the atomic percentage of non-Cu metal elements in the copper alloy matrix is ​​greater than 65 at.%, and can be 65 at.%-80 at.%. Thus, when the prepared three-dimensional porous copper is used in a battery current collector, the electrochemical performance of the battery can be better improved.

[0028] The second aspect of the present application provides a three-dimensional porous copper, which is prepared by the preparation method of the first aspect of the present application.

[0029] In some embodiments, the pore diameter of the three-dimensional porous copper is 0.3 μm-20 μm, and optionally 2 μm-8 μm.

[0030] In some embodiments, the ligament width of the three-dimensional porous copper is 0.5 μm-20 μm, and optionally 2 μm-8 μm.

[0031] In some embodiments, the non-Cu metal residue in the three-dimensional porous copper is less than or equal to 5 at.%, and may be less than or equal to 2 at.%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Example 1.

[0033] FIG2 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Example 13.

[0034] FIG3 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Example 16.

[0035] FIG4 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 1.

[0036] FIG5 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 2.

[0037] FIG6 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 3.

[0038] FIG7 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 4.

[0039] FIG8 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 5.

[0040] FIG9 shows a scanning electron microscope (SEM) image of the three-dimensional porous copper prepared in Comparative Example 6. DETAILED DESCRIPTION

[0041] Below, the embodiments of the three-dimensional porous copper and its preparation method of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0042] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0044] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0045] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0046] In this application, the terms "plurality" and "multiple" refer to two or more.

[0047] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0048] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0049] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0050] The embodiments of the present application provide a method for preparing three-dimensional porous copper.

[0051] The preparation method comprises the following steps: providing a copper alloy substrate, the copper alloy substrate comprising a Cu element and a non-Cu metal element, the standard electrode potential of the non-Cu metal element being lower than the standard electrode potential of the Cu element; providing a corrosive solution, the corrosive solution comprising a neutral salt, a weakly acidic complexing agent and a solvent, the molar concentration of the neutral salt being denoted as C1, the molar concentration of the weakly acidic complexing agent being denoted as C2, both in mol / L, 0.04≤C2 / C1≤0.60, and C2 being less than or equal to 0.20 mol / L; and electrochemically corroding the copper alloy substrate using the corrosive solution as an electrolyte to obtain three-dimensional porous copper.

[0052] Currently, the etching solutions used in the dealloying process to fabricate three-dimensional porous copper structures primarily include strong acid solutions (such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and acetic acid), strong base solutions (such as sodium hydroxide and potassium hydroxide), neutral salt solutions (such as sodium chloride), or mixed solutions of strong acids and neutral salts. However, all of these etching solutions have certain drawbacks.

[0053] When the corrosive liquid is a strong alkaline solution or a neutral salt solution, the acidity and alkalinity of the corrosive liquid are difficult to control, which easily causes the metal ions dissolved from the copper alloy matrix to form solid metal compound particles and adsorb on the surface of the formed three-dimensional porous copper structure, thereby easily causing pore blocking and surface passivation problems, and thus causing the porosity of the prepared three-dimensional porous copper structure to be far lower than the theoretical value (i.e., the theoretical value of the porosity after the copper alloy matrix is ​​completely dealloyed). In addition, since the surface of the three-dimensional porous copper structure is covered with solid metal compound particles, the presence of solid metal compound particles will also hinder the further modification of the three-dimensional porous copper structure, for example, it will hinder the lithiation treatment of the three-dimensional porous copper structure, and then when applied to batteries, it is difficult to effectively improve the performance of the battery.

[0054] When the corrosive liquid is a strong acid solution or a mixed solution of a strong acid and a neutral salt, the prepared three-dimensional porous copper structure is prone to cracks during electrochemical corrosion. When used in batteries, the cracked structure is likely to aggravate the uneven deposition of metal, thereby affecting the performance of the battery.

[0055] The etching solution provided in the embodiment of the present application includes a neutral salt and a weakly acidic chelating agent, and the molar concentration C1 of the neutral salt and the molar concentration C2 of the weakly acidic chelating agent also satisfy 0.04≤C2 / C1≤0.60 and C2 is less than or equal to 0.20 mol / L.

[0056] During the electrochemical dealloying process, the non-Cu metal in the copper alloy matrix loses electrons, and the electrons flow to the counter electrode through the external circuit. The hydrogen ions near the counter electrode gain electrons to produce hydrogen. At the same time, the etching solution between the counter electrode and the working electrode acts as a conductive solution, contributing ionic conductivity to allow the current to flow smoothly.

[0057] The neutral salt in the etching solution itself does not participate in the electrochemical reaction, so its concentration can remain relatively stable during the electrochemical dealloying process, and the electrochemical dealloying effect is not affected by changes in the etching solution concentration. The molar concentration C1 of the neutral salt and the molar concentration C2 of the weakly acidic complexing agent satisfy C2 / C1 less than or equal to 0.60. Compared with the weakly acidic complexing agent, the molar concentration of the neutral salt is higher, thereby providing a sufficiently large and stable ionic conductivity for the electrochemical dealloying working circuit, thereby ensuring smooth current flow in the working circuit.

[0058] Weakly acidic complexing agents provide hydrogen ions for the reduction half-reaction at the electrode, thereby maintaining the weak acidity of the corrosive solution. As hydrogen ions are consumed, a large number of free acid radicals can also act as complexing agents, thereby reducing or even inhibiting the precipitation reaction of metal ions dissolved during the dealloying process. In addition, they can complex the metal ions dissolved during the dealloying process and promote the forward corrosion reaction.

[0059] The molar concentration C1 of the neutral salt and the molar concentration C2 of the weakly acidic complexing agent satisfy C2 / C1 greater than or equal to 0.04, thereby helping to reduce the precipitation reaction of the metal ions dissolved during the electrochemical dealloying process, thereby reducing the problem of pore blocking and surface passivation, and further improving the porosity of the prepared three-dimensional porous copper structure. During the electrochemical dealloying process, the counter electrode continuously consumes hydrogen ions due to hydrogen evolution. When C2 / C1 is less than 0.04, the etching solution near the counter electrode easily becomes alkaline. At the same time, after the etching solution in this area diffuses toward the working electrode, it is also easy for the metal ions dissolved from the copper alloy matrix to form solid metal compound particles and adsorb on the surface of the formed three-dimensional porous copper structure, which easily causes pore blocking and surface passivation problems, and also reduces the porosity of the prepared three-dimensional porous copper structure, and its porosity is usually far lower than the theoretical value.

[0060] The molar concentration C2 of the weakly acidic complexing agent also needs to be less than or equal to 0.20 mol / L to reduce the formation of hydrogen embrittlement cracks. When the molar concentration C2 of the weakly acidic complexing agent is greater than 0.20 mol / L, the hydrogen ion concentration at the dealloying interface is too high, which can easily cause a violent chemical dealloying reaction and thus easily lead to the formation of hydrogen embrittlement cracks.

[0061] Therefore, the etching solution provided in the embodiment of the present application can provide a stable corrosion environment, reduce the precipitation reaction of the metal ions dissolved during the electrochemical dealloying process, thereby reducing the pore blocking problem and surface passivation problem of the prepared three-dimensional porous copper, and further improve the porosity of the prepared three-dimensional porous copper structure; at the same time, it can also reduce crack formation.

[0062] The three-dimensional porous copper obtained by the preparation method provided in the embodiment of the present application can have a high porosity and fewer cracks, thereby improving the electrochemical performance of the battery when used in a battery current collector.

[0063] C2 / C1 can be 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.24, 0.30, 0.40, 0.50, 0.60, or any range thereof. In some embodiments, optionally, 0.06≤C2 / C1≤0.40, 0.08≤C2 / C1≤0.30, 0.10≤C2 / C1≤0.24, 0.10≤C2 / C1≤0.20, and 0.10≤C2 / C1≤0.16.

[0064] By further adjusting C2 / C1 within the above range, the porosity of the prepared three-dimensional porous copper structure can be further improved and crack formation can be reduced.

[0065] In some embodiments, the molar concentration C2 of the weakly acidic complexing agent can be 0.04mol / L-0.20mol / L, for example, it can be 0.04mol / L, 0.05mol / L, 0.06mol / L, 0.07mol / L, 0.08mol / L, 0.09mol / L, 0.10mol / L, 0.11mol / L, 0.12mol / L, 0.13mol / L, 0.14mol / L, 0.15mol / L, 0.16mol / L, 0.17mol / L, 0.18mol / L, 0.19mol / L, 0.20mol / L, or a range consisting of any of the above values. Alternatively, the molar concentration C2 of the weakly acidic complexing agent can be 0.08mol / L-0.16mol / L.

[0066] By further adjusting the molar concentration C2 of the weakly acidic complexing agent within the above range, the pore blocking problem and surface passivation problem of the prepared three-dimensional porous copper can be further reduced, the porosity of the prepared three-dimensional porous copper structure can be improved, and the formation of hydrogen embrittlement cracks can be further reduced.

[0067] In some embodiments, the molar concentration C1 of the neutral salt can be 0.2mol / L-2.0mol / L, for example, it can be 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1.0mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L, 1.6mol / L, 1.7mol / L, 1.8mol / L, 1.9mol / L, 2.0mol / L, or a range consisting of any of the above values. Optionally, the molar concentration C1 of the neutral salt can be 0.5mol / L-1.5mol / L.

[0068] By further adjusting the molar concentration C1 of the neutral salt within the above range, the reaction rate of electrochemical dealloying can be increased, the porosity of the prepared three-dimensional porous copper structure can be increased, and crack formation can be reduced.

[0069] In some embodiments, the copper alloy substrate may be in sheet or foil form.

[0070] The copper alloy matrix includes Cu element and non-Cu metal elements. The atomic mass ratio of Cu element and non-Cu metal elements is not particularly limited and can be adjusted according to the required porosity of the three-dimensional porous copper structure.

[0071] In some embodiments, the atomic percentage of non-Cu metal elements in the copper alloy matrix can be greater than 65 at.%, optionally 65 at.%-80 at.%, and more preferably 70 at.%-75 at.%. As a result, when the prepared three-dimensional porous copper is used in a battery current collector, the electrochemical performance of the battery can be better improved.

[0072] In some embodiments, the non-Cu metal elements in the copper alloy matrix may include one or more of Mn, Zn, Ni, Al, and Fe.

[0073] In some embodiments, the copper alloy matrix may further include non-metallic elements, such as C, Si, etc.

[0074] The copper alloy substrate can be purchased commercially or prepared according to methods known in the art, for example, by a smelting method.

[0075] In some embodiments, the molar amount of the weakly acidic complexing agent in the etching solution may be more than twice the molar amount of the non-Cu metal element in the copper alloy matrix, and may be 2 to 8 times.

[0076] In some embodiments, the neutral salt in the etching solution may include one or more of sodium salt and potassium salt, and may optionally include one or more of sodium chloride and potassium chloride.

[0077] The complexing effect of the weakly acidic complexing agent generally refers to the ability of the weakly acidic complexing agent to complex non-Cu metal ions dissolved from the copper alloy matrix. In some embodiments, the weakly acidic complexing agent in the etching solution may include one or more of a dicarboxylic acid, a polycarboxylic acid, and their respective salts.

[0078] Optionally, the weak acid complexing agent in the etching solution may include one or more of citric acid, isocitric acid, malic acid, tartaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and their respective salts.

[0079] Optionally, the salts of the above-mentioned dicarboxylic acids and polycarboxylic acids may include one or more of sodium salt, potassium salt, sodium-potassium salt and ammonium salt.

[0080] By further adjusting the weakly acidic complexing agent within the above range, the porosity of the prepared three-dimensional porous copper structure can be further improved, and crack formation can also be reduced.

[0081] In some embodiments, the solvent in the etching solution may include water, such as deionized water, pure water, etc.

[0082] In some embodiments, a three-electrode system can be used to electrochemically etch the copper alloy substrate using a corrosive solution as an electrolyte, wherein the copper alloy substrate serves as a working electrode, the AgCl / Ag electrode serves as a reference electrode, and the platinum electrode serves as a counter electrode.

[0083] In some embodiments, the voltage between the copper alloy substrate and the reference electrode may be -0.70V to -0.15V.

[0084] In some embodiments, the temperature for electrochemically corroding the copper alloy substrate using the corrosive solution as the electrolyte may be 10° C.-65° C., and may be optionally 20° C.-35° C.

[0085] In some embodiments, the time for electrochemically etching the copper alloy substrate using the etching solution as the electrolyte may be 3 hours to 24 hours, and may optionally be 6 hours to 10 hours.

[0086] In some embodiments, the preparation method may further include the step of rinsing the copper alloy substrate with a corrosive solution.

[0087] In some embodiments, the preparation method may further include the steps of: washing the three-dimensional porous copper after electrochemical etching with water, washing with alcohol, and drying. The water washing can remove soluble salts in the three-dimensional porous copper structure, and the alcohol washing can remove residual moisture in the three-dimensional porous copper structure.

[0088] The number of water washing and alcohol washing is not particularly limited, and the washing time is also not particularly limited.

[0089] Optionally, anhydrous ethanol can be used for alcohol washing.

[0090] The embodiment of the present application also provides a three-dimensional porous copper prepared by the above preparation method.

[0091] In some embodiments, the diameter of the holes of the three-dimensional porous copper may be 0.3 μm-20 μm, and optionally 2 μm-8 μm.

[0092] In some embodiments, the ligament width of the three-dimensional porous copper may be 0.5 μm-20 μm, optionally 2 μm-8 μm.

[0093] In some embodiments, the non-Cu metal residue (atomic percentage) of the three-dimensional porous copper may be less than or equal to 5 at.%, and may optionally be less than or equal to 2 at.%.

[0094] Example

[0095] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0096] Preparation of copper alloy substrate

[0097] A Mn75Cu25 alloy was prepared using a Mn:Cu ratio of 75:25 (at%) using vacuum induction melting. The resulting CuMn alloy was cut into 3 mm ingots, cold-rolled to a thickness of approximately 0.25 mm, and then annealed in an argon atmosphere at 400°C-700°C for 6 hours.

[0098] The annealed CuMn alloy was cut into alloy sheets of 32.0 mm × 25.0 mm in size. The surface of the CuMn alloy was polished to a bright finish using 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpaper, respectively. The alloy was then ultrasonically cleaned in 200 ml of deionized water and 200 ml of ethanol for 20 seconds, respectively, and then vacuum-baked at 25°C for 1 hour to obtain CuMn alloy sheets with a clean and bright surface.

[0099] Example 1

[0100] Weigh NaCl and citric acid in batches and add them to 400g of deionized water. Stir continuously until completely dissolved. Transfer the solution to a 500ml volumetric flask and add deionized water to 500ml to obtain a corrosion solution. The concentration of NaCl is 1mol / L, and the concentration of citric acid is 0.12mol / L.

[0101] Rinse the platinum electrode (counter electrode), AgCl / Ag reference electrode, platinum electrode holder, and electrolytic cell with 300ml of deionized water, and absorb any remaining water with dust-free paper. Rinse each component three times with 50ml of the above-mentioned etching solution, and transfer the remaining 300ml of etching solution to the etching tank.

[0102] Secure the CuMn alloy sheet to the platinum electrode holder and install the electrodes in the order of the platinum electrode holder (working electrode), AgCl / Ag reference electrode, and platinum electrode (counter electrode), ensuring that all electrodes are at the same height, approximately half the height of the electrolytic cell. Connect these three electrodes to the electrochemical workstation, so that the CuMn alloy sheet and the platinum electrode form the working circuit, and the CuMn alloy sheet and the AgCl / Ag reference electrode form the reference circuit.

[0103] During the electrochemical dealloying process, a constant potential method was used, with a voltage difference of -0.2 V between the CuMn alloy sheet and the AgCl / Ag reference electrode, and the corrosion time was set to 8 hours. After the corrosion reaction was completed, the CuMn alloy sheet turned from silvery white to copper.

[0104] Remove the above-mentioned three-dimensional porous copper sheet and soak it in 200 ml of deionized water three times, each soaking time is 10 minutes, to wash away the soluble salts remaining in the three-dimensional porous copper sheet; then soak the above-mentioned three-dimensional porous copper sheet twice with 100 ml of anhydrous ethanol, each soaking time is 5 minutes, to wash away the residual water in the three-dimensional porous copper sheet; finally, transfer the above-mentioned three-dimensional porous copper sheet to a vacuum drying oven and bake it in an environment of 30°C and -0.1 MPa for 4 hours.

[0105] Examples 2 to 17

[0106] The preparation method of the three-dimensional porous copper sheet is similar to that of Example 1, except that the composition and / or concentration of the etching solution are different. Specific parameters are shown in Table 1.

[0107] Comparative Examples 1 to 6

[0108] The preparation method of the three-dimensional porous copper sheet is similar to that of Example 1, except that the composition and / or concentration of the etching solution are different. Specific parameters are shown in Table 1. In Table 1, / indicates that the corresponding component is not added to the etching solution.

[0109] Performance Testing

[0110] (1) Surface morphology test of three-dimensional porous copper sheet

[0111] The surface morphology of the three-dimensional porous copper sheet is tested using a scanning electron microscope (SEM), which can be a ZEISS Sigma 300.

[0112] (2) Mn residue test of three-dimensional porous copper sheet

[0113] The atomic percentage of residual Mn in the three-dimensional porous copper sheet was determined by inductively coupled plasma atomic emission spectroscopy (ICP).

[0114] (3) Porosity test of three-dimensional porous copper sheet

[0115] The length, width, and thickness of the three-dimensional porous copper sheet were measured using a micrometer screw, and the mass of the three-dimensional porous copper sheet was weighed using an analytical balance. To reduce measurement errors, the length and width of the three-dimensional porous copper sheet were measured at three different locations and the average values ​​were taken. The thickness of the three-dimensional porous copper sheet was measured at five different locations and the average values ​​were taken. The mass of the three-dimensional porous copper sheet was weighed three times and the average values ​​were taken.

[0116] The porosity of the three-dimensional porous copper sheet is:

[0117] P: Porosity of the three-dimensional porous copper sheet.

[0118] m: average mass of the three-dimensional porous copper sheet, in g.

[0119] a: Average length of the three-dimensional porous copper sheet, in mm.

[0120] b: Average width of the three-dimensional porous copper sheet, in mm.

[0121] h: average thickness of the three-dimensional porous copper sheet, in mm.

[0122] ρ: True density of pure copper, in g / cm 3 .

[0123] The test results are shown in Table 1.

[0124] Table 1

[0125] As can be seen from the test results in Table 1, by adjusting the corrosion solution to include a neutral salt and a weakly acidic chelating agent, and adjusting the molar concentration C1 of the neutral salt and the molar concentration C2 of the weakly acidic chelating agent to satisfy 0.04≤C2 / C1≤0.60 and C2 less than or equal to 0.20mol / L, a stable corrosion environment can be provided, thereby reducing the precipitation reaction of manganese ions dissolved during the electrochemical dealloying process, thereby reducing the pore blocking problem and surface passivation problem of the prepared three-dimensional porous copper, and thus improving the porosity of the prepared three-dimensional porous copper sheet; at the same time, crack formation can also be reduced. As can be seen from Figures 1 to 3, the prepared three-dimensional porous copper sheet has a high porosity, and at the same time, there is no obvious solid metal compound particle coverage on the surface of the prepared three-dimensional porous copper sheet, and no obvious cracks (no cracks with a width of more than 5μm) are formed.

[0126] The molar ratio C2 / C1 of the weakly acidic complexing agent to the neutral salt in the etching solution prepared in Comparative Example 1 is very small, and the molar concentration C2 of the weakly acidic complexing agent in the etching solution is also small. At this time, the weakly acidic complexing agent cannot fully play its role in maintaining the acidity of the electrolyte and complexing manganese ions. In addition, during the electrochemical dealloying process, the electrode will continuously consume hydrogen ions due to hydrogen evolution, and thus the etching solution near the electrode is easily converted to alkaline, thereby causing the manganese ions dissolved in the copper alloy matrix to easily form solid metal compound particles and adsorb on the surface of the formed three-dimensional porous copper, which is easy to cause pore blocking and surface passivation problems, and also reduce the porosity of the prepared three-dimensional porous copper sheet. As can be seen from Figure 4, the porosity of the prepared three-dimensional porous copper sheet is low, and the surface of the prepared three-dimensional porous copper sheet is also covered with a large number of solid metal compound particles.

[0127] In Comparative Example 2, the etching solution used a citric acid solution. Because citric acid itself participates in the chemical dealloying reaction, the concentration of the citric acid solution decreases during the dealloying process, thereby affecting the ionic conductivity of the etching solution and the dealloying effect, thereby reducing the porosity of the three-dimensional porous copper sheet. Furthermore, when the etching solution used a citric acid solution, the electrochemical dealloying rate is relatively slow, while the chemical dealloying rate is relatively fast, which easily leads to crack formation. As can be seen from Figure 5, the porosity of the prepared three-dimensional porous copper sheet is low, and cracks have also formed on the surface of the prepared three-dimensional porous copper sheet.

[0128] The etching solution in Comparative Example 3 uses a neutral salt and acetic acid solution. Acetic acid is a monobasic acid. At the same molar concentration, it can dissociate fewer hydrogen ions. At the same time, acetic acid itself does not complex manganese ions. Therefore, during the electrochemical dealloying process, the manganese ions dissolved from the copper alloy matrix easily form solid metal compound particles and adsorb on the surface of the formed three-dimensional porous copper. As can be seen from Figure 6, the porosity of the prepared three-dimensional porous copper sheet is relatively low, and the surface of the prepared three-dimensional porous copper sheet is also covered with a large number of solid metal compound particles.

[0129] In the etching solution prepared in Comparative Example 4, the molar ratio C2 / C1 of the weakly acidic complexing agent to the neutral salt was relatively high. Consequently, the electrochemical dealloying reaction rate was slow, and the copper alloy matrix was not completely dealloyed. This resulted in a low porosity in the prepared three-dimensional porous copper sheet. Furthermore, the molar concentration C1 of the neutral salt in the etching solution was relatively low, and the dealloying reaction of the copper alloy matrix was primarily a chemical corrosion reaction, which also easily led to crack formation. As can be seen in Figure 7, the prepared three-dimensional porous copper sheet has a low porosity and cracks have formed on its surface.

[0130] In the etching solution prepared in Comparative Example 5, the molar ratio C2 / C1 of the weakly acidic complexing agent to the neutral salt is low, and the molar concentration C1 of the neutral salt is high. This results in a faster electrochemical dealloying reaction, which generates significant stress in the copper alloy matrix. This results in significant cracks in the resulting three-dimensional porous copper sheet. As shown in Figure 8, large cracks have formed on the surface of the prepared three-dimensional porous copper sheet.

[0131] The molar concentration C2 of the weakly acidic complexing agent in the etching solution prepared in Comparative Example 6 is relatively high, which causes a violent chemical dealloying reaction and easily leads to the formation of hydrogen embrittlement cracks. As can be seen from Figure 9, large cracks are formed on the surface of the prepared three-dimensional porous copper sheet.

[0132] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing three-dimensional porous copper, comprising the following steps: Providing a copper alloy matrix, wherein the copper alloy matrix includes a Cu element and a non-Cu metal element, wherein the standard electrode potential of the non-Cu metal element is lower than the standard electrode potential of the Cu element; Providing a corrosive solution, wherein the corrosive solution comprises a neutral salt, a weakly acidic complexing agent and a solvent, wherein the molar concentration of the neutral salt is recorded as C1, and the molar concentration of the weakly acidic complexing agent is recorded as C2, both in mol / L, 0.04≤C2 / C1≤0.60, and C2 is less than or equal to 0.20 mol / L; The copper alloy substrate is electrochemically corroded by using the corrosive solution as an electrolyte to obtain three-dimensional porous copper.

2. The preparation method according to claim 1, wherein 0.10≤C2 / C1≤0.

24.

3. The preparation method according to any one of claims 1 to 2, wherein: C1 is 0.2mol / L-2.0mol / L, and can be optionally 0.5mol / L-1.5mol / L; and / or, C2 is 0.04mol / L-0.20mol / L, and can be optionally 0.08mol / L-0.16mol / L.

4. The preparation method according to any one of claims 1 to 3, wherein: The neutral salt includes one or more of sodium salt and potassium salt, and may optionally include one or more of sodium chloride and potassium chloride; and / or, The weakly acidic complexing agent includes one or more of dicarboxylic acids, polycarboxylic acids, and their respective salts, and may be selected from citric acid, isocitric acid, malic acid, tartaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and their respective salts. Optionally, the salt includes one or more of sodium salt, potassium salt, sodium potassium salt, and ammonium salt; and / or, The solvent includes water.

5. The preparation method according to any one of claims 1 to 4, wherein: The copper alloy substrate is electrochemically corroded by using a three-electrode system with the corrosive solution as an electrolyte, the copper alloy substrate is a working electrode, the AgCl / Ag electrode is a reference electrode, and the platinum electrode is a counter electrode.

6. The preparation method according to claim 5, wherein: The voltage between the copper alloy substrate and the reference electrode is -0.70V to -0.15V.

7. The preparation method according to any one of claims 1 to 6, wherein: The temperature for electrochemically corroding the copper alloy substrate using the corrosive solution as an electrolyte is 10° C.-65° C., and can be optionally 20° C.-35° C.; and / or, The time for electrochemically corroding the copper alloy substrate using the corrosive solution as the electrolyte is 3h-24h, and can be optionally 6h-10h.

8. The preparation method according to any one of claims 1 to 7, wherein: The copper alloy substrate is in the form of a sheet or foil; and / or, The non-Cu metal elements include one or more of Mn, Zn, Ni, Al, and Fe.

9. The preparation method according to any one of claims 1 to 8, wherein: The preparation method further comprises the step of: using a corrosive liquid to rinse the copper alloy substrate.

10. The preparation method according to any one of claims 1 to 9, wherein: The preparation method also includes the steps of: washing the three-dimensional porous copper after electrochemical corrosion with water, washing with alcohol and drying.

11. The preparation method according to any one of claims 1 to 10, wherein: The atomic percentage of the non-Cu metal elements in the copper alloy matrix is ​​greater than 65 at.%, and can be selected to be 65 at.%-80 at.%.

12. A three-dimensional porous copper prepared by the preparation method according to any one of claims 1 to 11.

13. The three-dimensional porous copper according to claim 12, wherein: The pore diameter of the three-dimensional porous copper is 0.3 μm-20 μm, and can be 2 μm-8 μm; and / or, The ligament width of the three-dimensional porous copper is 0.5 μm-20 μm, and can be 2 μm-8 μm; and / or, The non-Cu metal residue in the three-dimensional porous copper is less than or equal to 5 at.%, and can be less than or equal to 2 at.%.

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