Current collector, preparation method thereof and non-cathode battery

Abstract

The invention relates to the technical field of batteries, in particular to a current collector, a preparation method thereof and a negative-electrode-free battery. The current collector comprises a negative current collector substrate and a functional coating, the functional coating comprises a composite microsphere material, and the composite microsphere material is of a core-shell structure and sequentially comprises an inner core, a first shell layer, a second shell layer and a third shell layer from inside to outside; the inner core is a copper metal microsphere with a hollow structure; the first shell layer comprises metal carbide with a pore structure, and copper metal is contained in the pore structure; the second shell layer comprises copper metal; the third shell layer includes a porous material. According to the current collector, the uniformity and conductivity of lithium ion deposition can be improved, the weight of the current collector can be reduced to the maximum extent, the energy density is improved, and meanwhile the structural strength of the current collector is enhanced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a current collector and a preparation method thereof and a negative electrode-free battery. Background Art

[0002] In order to improve the energy density of lithium batteries, more and more research efforts are being invested in the weight reduction design of battery cells. The negative electrode-free battery structure does not require negative electrode active materials, so it greatly reduces the mass of the battery and improves the energy density of lithium batteries. However, the negative electrode-free battery structure currently faces a serious problem. Without the lithium embedding of the negative electrode active material, where should the lithium ions released from the positive electrode go? Although the conventional copper foil negative electrode can deposit lithium, it faces the risk of uneven lithium deposition, forming lithium dendrites, piercing the diaphragm, causing contact short circuits between the positive and negative electrodes, and causing safety problems. Therefore, how to solve the problem of uneven lithium deposition in the negative electrode-free battery structure is one of the key points of the application of the negative electrode-free battery structure.

[0003] The patent with publication number CN113013417A discloses a negative electrode-free lithium metal battery structure, in which an electronic conductor layer and an ion conductive layer are coated on the outer layer of the traditional negative electrode current collector. Although this method can accommodate the lithium source escaping from the positive electrode, the patent adopts a method of directly immersing copper foil in an ion coating gel. The coating does not have a large number of pores, thus hindering the deposition rate of lithium ions on the surface of the copper foil. The efficiency of lithium deposition is low. In severe cases, lithium ions are not deposited in time (high rate charging) and are deposited on the coating surface, causing lithium dendrites to pierce the diaphragm and cause a short circuit. In addition, the ion conductive layer is difficult to prepare, and the traditional negative electrode metal substrate has a large mass, which affects the energy density of the battery.

[0004] The patent with publication number CN116581361A discloses a negative electrode-free lithium battery structure, which provides lithium insertion space and avoids direct reaction with the electrolyte by setting a lithium titanate layer and inserting lithium in combination with a solid electrolyte. However, the current solid electrolyte has problems such as low ion transfer rate and interface contact, which affects the power performance of the battery, and the setting of the lithium titanate layer also increases weight, which is not conducive to improving the energy density of the negative electrode-free battery.

[0005] The patent with publication number CN115863660B discloses a negative electrode current collector for a negative electrode-free lithium battery, which is a copper foil current collector surface etched to prepare a nanosilver array to induce the deposition of lithium ions. However, this method is difficult and uneven to prepare, and it is easy to cause safety problems such as short circuit caused by membrane penetration.

[0006] Therefore, how to improve the uniformity and conductivity of lithium ion deposition has become one of the important solutions for the application of negative electrode-free battery current collectors. Summary of the invention

[0007] In view of this, the present invention provides a current collector and a preparation method thereof and a negative electrode-free battery. The current collector can improve the uniformity and conductivity of lithium ion deposition, and can also reduce the weight of the current collector to a certain extent, improve the energy density, and enhance the structural strength of the current collector.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a current collector, comprising:

[0010] a) negative electrode current collector matrix;

[0011] b) a functional coating, which is disposed on at least one surface of the negative electrode current collector substrate in the thickness direction; the functional coating comprises a composite microsphere material, which has a core-shell structure, and comprises a core, a first shell layer, a second shell layer and a third shell layer from the inside to the outside;

[0012] The core is a copper metal microsphere with a hollow structure;

[0013] The first shell layer includes a metal carbide having a porous structure, wherein the porous structure includes copper metal;

[0014] The second shell layer includes copper metal;

[0015] The third shell includes a porous material.

[0016] In the embodiment of the present invention, the copper metal microspheres with a hollow structure may be in the shape of a sphere, an ellipsoid or an irregular sphere.

[0017] In an embodiment of the present invention, the metal carbide includes at least one of titanium carbide, tungsten carbide and zirconium carbide.

[0018] In an embodiment of the present invention, the porous material includes at least one of ZIF, MOF, and COF.

[0019] In an embodiment of the present invention, the negative electrode current collector substrate includes one of copper foil, titanium foil, nickel mesh, stainless steel foil, and carbon cloth.

[0020] Preferably, the diameter of the inner core is 110-1100 nm.

[0021] Preferably, the diameter of the hollow structure is 100 to 1000 nm.

[0022] Preferably, the thickness of the first shell layer is 500-2000 nm, the porosity is 5%-20%, and the pore size of the pore structure is 50-200 nm.

[0023] Preferably, the thickness of the second shell layer is 10-100 nm.

[0024] Preferably, the thickness of the third shell layer is 500-1000 nm.

[0025] Preferably, the thickness of the functional coating on one side is 0.5 to 10 μm.

[0026] Preferably, the mass ratio of metal carbide, copper metal and porous material is (5-20):(40-80):(20-40).

[0027] In an embodiment of the present invention, the first shell layer further comprises a carbon material. The first shell layer comprises a metal carbide and a carbon material.

[0028] Preferably, when the first shell layer comprises metal carbide and carbon material, the mass percentage of the metal carbide in the first shell layer is 10% to 90%.

[0029] In an embodiment of the present invention, the third shell layer further includes a first adhesive.

[0030] Preferably, when the third shell layer includes a porous material and a first binder, the mass ratio of the porous material in the third shell layer to the first binder is (80-95):(5-20).

[0031] In an embodiment of the present invention, the functional coating further includes a second binder.

[0032] Preferably, when the functional coating comprises a composite microsphere material and a second binder, the mass ratio of the composite microsphere material to the second binder in the functional coating is (80-95):(5-20).

[0033] In an embodiment of the present invention, the first binder and the second binder independently include at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0034] In a second aspect, the present invention provides a method for preparing a current collector, comprising the following steps:

[0035] S1, mixing a pore-forming agent and a third binder to obtain a pore-forming agent slurry, coating the pore-forming agent slurry on the surface of the polymer microspheres, drying the obtained material, dissolving the polymer microspheres, washing with water, and drying to obtain a hollow porous precursor material;

[0036] The hollow porous precursor material and the metal salt solution are mixed, and subjected to a first soaking treatment to obtain a first soaked material; in an inert gas atmosphere, the first soaked material is contacted with an alkane gas, and subjected to a first high temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material;

[0037] S2, mixing a metal carbide three-dimensional skeleton precursor material and a solution containing copper ions, and subjecting the mixture to a second soaking treatment to obtain a second soaked material; under the action of a reducing agent, the copper ions in the second soaked material are reduced to copper metal to obtain a microsphere precursor material; subjecting the microsphere precursor material to a second high-temperature treatment to obtain a microsphere material, wherein the microsphere material is a microsphere material having a hollow structure and a copper metal microsphere surface composited with a first shell layer and a second shell layer;

[0038] S3, preparing a porous material to obtain a porous material slurry, and coating the porous material slurry on the surface of the microsphere material to obtain a composite microsphere material;

[0039] S4, preparing the composite microsphere material to obtain a composite microsphere material slurry, coating the composite microsphere material slurry on the surface of the negative electrode current collector substrate, and drying to obtain the current collector.

[0040] In an embodiment of the present invention, in step S1, the pore-forming agent includes at least one of ammonium bicarbonate, ammonium chloride, and ammonium nitrate.

[0041] In an embodiment of the present invention, the third binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0042] Preferably, the mass ratio of the pore former to the third binder is (90-95):(5-10).

[0043] In an embodiment of the present invention, the high molecular polymer microspheres include at least one of polyethylene microspheres, polystyrene microspheres, polyethylene microspheres, polyvinyl chloride microspheres, and polypropylene microspheres.

[0044] In an embodiment of the present invention, the metal salt solution includes at least one of a titanium tetrachloride aqueous solution, a tungsten tetrachloride aqueous solution, and a zirconium chloride aqueous solution.

[0045] Preferably, the concentration of the metal salt solution is 0.01 to 0.5 mol / L.

[0046] Preferably, the first immersion treatment time is 0.5 to 2 hours.

[0047] In an embodiment of the present invention, the alkane gas includes at least one of methane, ethane, propane and butane.

[0048] Preferably, the temperature of the first high temperature treatment is 800-1400° C., and the time of the first high temperature treatment is 2-6 hours.

[0049] In an embodiment of the present invention, in step S2, the solution containing copper ions includes at least one of a copper sulfate solution, a copper nitrate solution, and a copper chloride solution.

[0050] Preferably, the concentration of the solution containing copper ions is 0.1 to 0.5 mol / L.

[0051] Preferably, the second immersion treatment time is 2 to 4 hours.

[0052] In an embodiment of the present invention, the reducing agent includes at least one of hydrazine hydrate, iron and zinc.

[0053] Preferably, the temperature of the second high temperature treatment is 600-800° C., and the time of the second high temperature treatment is 2-4 hours.

[0054] In an embodiment of the present invention, in step S3, preparing the porous material to obtain the porous material slurry comprises: mixing the porous material and the first binder to prepare the porous material slurry.

[0055] In the embodiment of the present invention, in step S4, preparing the composite microsphere material to obtain the composite microsphere material slurry comprises: mixing the composite microsphere material and the second binder to obtain the composite microsphere material slurry.

[0056] In a third aspect, the present invention provides a negative electrode-free battery, which includes the above-mentioned current collector and / or the current collector prepared by the above-mentioned preparation method.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] 1. The current collector of the present invention includes a negative electrode current collector matrix and a functional coating disposed on the surface of the negative electrode current collector matrix; the functional coating includes a composite microsphere material, the composite microsphere material has a core-shell structure, and includes a core, a first shell layer, a second shell layer and a third shell layer from the inside to the outside; the core is a copper metal microsphere with a hollow structure; the first shell layer includes a metal carbide with a pore structure, and the pore structure includes copper metal; the second shell layer includes copper metal; and the third shell layer includes a porous material. Among them, the hollow structure greatly reduces the weight of the current collector and improves the energy density, and the hollow structure and the pore structure can provide a large amount of site space for the deposition of lithium ions, improve the uniformity of lithium ion deposition, and improve safety performance; the characteristics of the pore structure are conducive to the shuttling of lithium ions, provide a higher ion transmission speed, and are conducive to the improvement of power performance.

[0059] 2. Copper metal is deposited on the surface and pores of the first shell layer of metal carbide. This structure not only enhances the conductivity of the hollow structure, which is conducive to attracting lithium ions, but also its metallic properties can enhance compatibility with the current collector, improve the overall conductivity of the current collector, further improve the structural strength of the metal carbide, and improve the electrochemical performance of the battery. Therefore, the application of the present invention in the negative electrode-free battery market has obvious market competitiveness;

[0060] When copper foil is selected as the negative electrode current collector substrate, the deposited copper metal can further enhance the compatibility between the functional coating and the copper foil.

[0061] 3. The porous material in the current collector of the present invention can increase gas adsorption, improve battery safety, and prevent excessive growth of lithium dendrites from causing puncture short circuit of the diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic diagram of the structure of the composite microsphere material of the present invention.

[0063] The reference numerals are as follows:

[0064] 1: kernel;

[0065] 2: first shell;

[0066] 3: second shell;

[0067] 4: The third shell. DETAILED DESCRIPTION

[0068] The present invention discloses a current collector and a method for preparing the same and a battery. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are deemed to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0069] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes, and do not indicate or imply relative importance.

[0070] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0071] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0072] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0073] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0074] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0075] Specifically, the present invention adopts the following technical solutions:

[0076] In a first aspect, the present invention provides a current collector, comprising:

[0077] a) negative electrode current collector matrix;

[0078] b) a functional coating, which is disposed on at least one surface of the negative electrode current collector substrate in the thickness direction; the functional coating comprises a composite microsphere material, which has a core-shell structure, and comprises a core, a first shell layer, a second shell layer and a third shell layer from the inside to the outside;

[0079] The core is a copper metal microsphere with a hollow structure;

[0080] The first shell layer includes a metal carbide having a porous structure, wherein the porous structure includes copper metal;

[0081] The second shell layer includes copper metal;

[0082] The third shell includes a porous material.

[0083] In an embodiment of the present invention, the metal carbide includes at least one of titanium carbide, tungsten carbide and zirconium carbide. The metal carbide can support the structural strength of the composite microsphere material, and the metal carbide has good electrical conductivity, which can improve the electrical conductivity of the negative electrode-free current collector.

[0084] In an embodiment of the present invention, the core is a copper metal microsphere with a hollow structure, the pore structure of the first shell layer includes copper metal, and the second shell layer includes copper metal. Copper metal can enhance conductivity, is conducive to attracting lithium ions, improves the structural strength of the metal carbide substrate, and its metallic properties can enhance compatibility with the current collector.

[0085] In an embodiment of the present invention, the porous material includes at least one of ZIF, MOF, and COF. The porous material layer has a pore structure, which can increase gas adsorption, improve battery safety, and prevent excessive growth of lithium dendrites from causing puncture short circuit of the diaphragm.

[0086] In an embodiment of the present invention, the particle size of the porous material is 100-500 nm. Exemplarily, the particle size of the porous material is any value among 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or any value within the range consisting of any two of the above values.

[0087] In an embodiment of the present invention, the negative electrode current collector substrate includes one of copper foil, titanium foil, nickel mesh, stainless steel foil, and carbon cloth.

[0088] Preferably, the negative electrode current collector substrate is copper foil. When copper foil is selected as the negative electrode current collector substrate, the deposited copper metal can further enhance the compatibility between the functional coating and the copper foil.

[0089] Preferably, the diameter of the core is 110-1100 nm. Exemplarily, the diameter of the core is any value among 110 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, or any value within the range formed by any two of the above values.

[0090] Preferably, the diameter of the hollow structure is 100 to 1000 nm. Exemplarily, the diameter of the hollow structure is any value in 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or any value in the range of any two of the above values. The diameter of the hollow structure within this range can greatly reduce the weight of the negative electrode current collector, improve the energy density, and the hollow structure can provide a large amount of site space for the deposition of lithium ions, improve the uniformity of lithium ion deposition, and improve safety performance.

[0091] Preferably, the thickness of the first shell layer is 500-2000nm, the porosity is 5%-20%, and the pore size of the pore structure is 50-200nm. Exemplarily, the thickness of the first shell layer is any value in 500nm, 600nm, 800nm, 1000nm, 1200nm, 1400nm, 1600nm, 1800nm, 2000nm or any value in the range of any two of the above values, the porosity is any value in 5%, 7%, 9%, 10%, 11%, 13%, 15%, 17%, 19%, 20% or any value in the range of any two of the above values, and the pore size of the pore structure is any value in 50nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm or any value in the range of any two of the above values. The parameters of the first shell layer are within the above range, which can provide a large amount of site space for the deposition of lithium ions, improve the uniformity of lithium ion deposition, and improve safety performance; it is also beneficial to the shuttling of lithium ions, providing a higher ion transmission speed, which is beneficial to the improvement of power performance.

[0092] Preferably, the thickness of the second shell layer is 10 to 100 nm. Exemplarily, the thickness of the second shell layer is any value among 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any value within the range of any two of the above values. The thickness of the second shell layer within this range can effectively enhance the conductivity, help attract lithium ions, improve the structural strength of the metal carbide substrate layer, and its metallic properties can enhance the compatibility with the current collector.

[0093] Preferably, the thickness of the third shell layer is 500-1000 nm. Exemplarily, the thickness of the third shell layer is any value among 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or any value within the range of values ​​composed of any two of the above values. The thickness of the third shell layer within this range can effectively increase gas adsorption, improve battery safety, and prevent excessive growth of lithium dendrites from puncturing the diaphragm and causing short circuit.

[0094] Preferably, the thickness of the functional coating on one side is 0.5 to 10 μm. Exemplarily, the thickness of the functional coating on one side is any value among 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value within the range of any two of the above values.

[0095] Preferably, the mass ratio of metal carbide, copper metal and porous material is (5-20): (40-80): (20-40). Exemplarily, the mass ratio of metal carbide, copper metal and porous material is any value among 1:8:8, 1:6:3, 7:45:35, 12:60:25, 1:4:1 or any value within the range consisting of any two of the above values.

[0096] In an embodiment of the present invention, the first shell layer further comprises a carbon material, which can serve as a carrier for the metal carbide to attach, improve the conductivity of the negative electrode-free current collector, and also play a role in adsorbing gas.

[0097] Preferably, when the first shell layer includes metal carbides and carbon materials, the mass percentage of the metal carbides in the first shell layer is 10% to 90%. Exemplarily, the mass percentage of the metal carbides in the first shell layer is any value among 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or any value within the range consisting of any two of the above values.

[0098] In an embodiment of the present invention, the third shell layer further includes a first adhesive.

[0099] Preferably, when the third shell layer includes a porous material and a first binder, the mass ratio of the porous material to the first binder in the third shell layer is (80-95):(5-20). Exemplarily, the mass ratio of the porous material to the first binder is any value among 4:1, 9:1, 95:14, 19:1, or any value within the range consisting of any two of the above values.

[0100] In an embodiment of the present invention, the functional coating further includes a second binder.

[0101] Preferably, when the functional coating includes a composite microsphere material and a second binder, the mass ratio of the composite microsphere material to the second binder in the functional coating is (80-95):(5-20). Exemplarily, the mass ratio of the composite microsphere material to the second binder is any value among 4:1, 9:1, 95:14, 19:1, or any value within the range of any two of the above values.

[0102] In the embodiment of the present invention, the first binder and the second binder independently include at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid. However, the types of binders are not limited thereto, and any binder type recognized by those skilled in the art is within the protection scope of the present invention.

[0103] In a second aspect, the present invention provides a method for preparing a current collector, comprising the following steps:

[0104] S1, mixing a pore-forming agent and a third binder to obtain a pore-forming agent slurry, coating the pore-forming agent slurry on the surface of the polymer microspheres, drying the obtained material, dissolving the polymer microspheres, washing with water, and drying to obtain a hollow porous precursor material;

[0105] The hollow porous precursor material and the metal salt solution are mixed, and subjected to a first soaking treatment to obtain a first soaked material; in an inert gas atmosphere, the first soaked material is contacted with an alkane gas, and subjected to a first high temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material;

[0106] S2, mixing a metal carbide three-dimensional skeleton precursor material and a solution containing copper ions, and subjecting the mixture to a second soaking treatment to obtain a second soaked material; under the action of a reducing agent, the copper ions in the second soaked material are reduced to copper metal to obtain a microsphere precursor material; subjecting the microsphere precursor material to a second high-temperature treatment to obtain a microsphere material, wherein the microsphere material is a microsphere material having a hollow structure and a copper metal microsphere surface composited with a first shell layer and a second shell layer;

[0107] S3, preparing a porous material to obtain a porous material slurry, and coating the porous material slurry on the surface of the microsphere material to obtain a composite microsphere material;

[0108] S4, preparing the composite microsphere material to obtain a composite microsphere material slurry, coating the composite microsphere material slurry on the surface of the negative electrode current collector substrate, and drying to obtain the current collector.

[0109] In an embodiment of the present invention, in step S1, the pore-forming agent includes at least one of ammonium bicarbonate, ammonium chloride, and ammonium nitrate.

[0110] In an embodiment of the present invention, the third binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0111] After high-temperature treatment, the third binder is carbonized to obtain the carbon material in the first shell layer.

[0112] Preferably, the mass ratio of the pore-forming agent to the third binder is (90-95):(5-10). Exemplarily, the mass ratio of the pore-forming agent to the third binder is any value among 9:1, 91:7, 94:9, 19:1, or any value within the range of any two of the above values.

[0113] In the embodiment of the present invention, the drying process in step S1 can gradually decompose the pore-forming agent into CO 2 NH 3 Preferably, the drying temperature is 200-300°C and the drying time is 20-40 minutes.

[0114] In an embodiment of the present invention, the high molecular polymer microspheres include at least one of polyethylene microspheres, polystyrene microspheres, polyethylene microspheres, polyvinyl chloride microspheres, and polypropylene microspheres.

[0115] In the embodiment of the present invention, the dissolution treatment of the high molecular polymer microspheres is specifically: immersing the dried material in a toluene solution for 4 to 12 hours to dissolve the high molecular polymer microspheres.

[0116] In an embodiment of the present invention, the metal salt solution includes at least one of a titanium tetrachloride aqueous solution, a tungsten tetrachloride aqueous solution, and a zirconium chloride aqueous solution.

[0117] Preferably, the concentration of the metal salt solution is 0.01 to 0.5 mol / L. Exemplarily, the concentration of the metal salt solution is any value among 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or any value within the range consisting of any two of the above values.

[0118] Preferably, the first immersion treatment time is 0.5 to 2 hours. Exemplarily, the first immersion treatment time is any value among 0.5 hours, 1 hour, 1.5 hours, 2 hours, or any value within the range of any two of the above values.

[0119] In an embodiment of the present invention, the alkane gas includes at least one of methane, ethane, propane and butane.

[0120] Preferably, the temperature of the first high temperature treatment is 800-1400°C, and the time of the first high temperature treatment is 2-6h. Exemplarily, the temperature of the first high temperature treatment is any value in 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, or any value in the range of any two of the above values, and the time of the first high temperature treatment is any value in 2h, 3h, 4h, 5h, 6h, or any value in the range of any two of the above values. When the temperature of the first high temperature treatment is lower than 800°C, the compaction density of the hollow copper-based microspheres will be reduced, the energy density will be reduced to a certain extent, the conductivity will be worse, and the cycle and rate performance of the battery will be deteriorated; when the temperature of the first high temperature treatment is higher than 1400°C, the pores inside the composite microspheres will be closed, which is not conducive to the deposition of lithium ions.

[0121] In an embodiment of the present invention, in step S2, the solution containing copper ions includes at least one of a copper sulfate solution, a copper nitrate solution, and a copper chloride solution.

[0122] Preferably, the concentration of the solution containing copper ions is 0.1 to 0.5 mol / L. Exemplarily, the concentration of the solution containing copper ions is any value among 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or any value within the range consisting of any two of the above values.

[0123] Preferably, the second immersion treatment time is 2 to 4 hours. Exemplarily, the second immersion treatment time is any value among 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any value within the range of any two of the above values.

[0124] In an embodiment of the present invention, the reducing agent includes at least one of hydrazine hydrate, iron and zinc.

[0125] Preferably, the temperature of the second high temperature treatment is 600-800°C, and the time of the second high temperature treatment is 2-4h. Exemplarily, the temperature of the second high temperature treatment is any value among 600°C, 650°C, 700°C, 750°C, 800°C, or any value within the range of any two of the above values, and the time of the second high temperature treatment is any value among 2h, 2.5h, 3h, 3.5h, 4h, or any value within the range of any two of the above values.

[0126] In an embodiment of the present invention, in step S3, preparing the porous material to obtain the porous material slurry comprises: mixing the porous material and the first binder to prepare the porous material slurry.

[0127] In the embodiment of the present invention, in step S4, preparing the composite microsphere material to obtain the composite microsphere material slurry comprises: mixing the composite microsphere material and the second binder to obtain the composite microsphere material slurry.

[0128] In an embodiment of the present invention, the coating method includes at least one of spray coating, extrusion coating, and transfer coating.

[0129] In a third aspect, the present invention provides a negative electrode-free battery, which includes the above-mentioned current collector and / or the current collector prepared by the above-mentioned preparation method.

[0130] In the embodiment of the present invention, the negative electrode-free battery may be a lithium ion battery or a sodium ion battery.

[0131] In the embodiment of the present invention, the battery structure includes but is not limited to button batteries, soft-pack batteries, cylindrical batteries, etc.

[0132] The present application has no particular restrictions on the positive electrode sheet, separator, and electrolyte in the battery, and those skilled in the art can select them according to actual needs as long as the purpose of the present application can be achieved.

[0133] The reagents, instruments or materials used in the present invention can be obtained through commercial channels.

[0134] The present invention will be further described below in conjunction with embodiments:

[0135] Embodiment 1:

[0136] The preparation of the current collector in this embodiment includes the following steps:

[0137] (1) Preparation of hollow three-dimensional skeleton precursor:

[0138] The ammonium bicarbonate particles are ball-milled to prepare particles with a suitable particle size of 100 nm, and then the binder sodium carboxymethyl cellulose (CMC) and the ammonium bicarbonate particles are uniformly mixed in a ratio of 95:5, and vacuum stirred into a slurry, and then the slurry is spray-dried onto the surface of polyethylene (about 500 nm) microspheres, and the thickness of the coating layer is 1000 nm. Then, the material is allowed to stand in an environment of 240° C. for 30 minutes, and the dried material is immersed in a toluene solvent for 8 hours to dissolve the polyethylene microspheres, and then washed with water and dried to obtain a hollow porous precursor material;

[0139] The hollow porous precursor material was immersed in a titanium tetrachloride solution with a concentration of 0.1 mol / L, stirred and immersed for 2 h, and then the immersed material was taken out and heated under N 2 Under protective conditions, methane alkane gas is introduced to carry out high-temperature titanation reaction. The high-temperature titanation reaction temperature is 1000°C and the reaction time is 4 hours to obtain a titanium carbide three-dimensional skeleton precursor material.

[0140] (2) Preparation of titanium carbide microspheres composited with copper metal:

[0141] The above-mentioned titanium carbide three-dimensional skeleton precursor material is immersed in a copper sulfate solution with a concentration of 0.2 mol / L for 2 hours, and then a hydrazine hydrate reducing agent is added to the solution and fully reacted for 4 hours to obtain a composite three-dimensional material with copper element coated inside and on the surface of the three-dimensional skeleton. The composite three-dimensional material is then heated in an environment of 600°C for 2 hours to obtain a microsphere material.

[0142] (3) Preparation of composite microsphere materials:

[0143] The ZIF porous material is ground into particles with a particle size of 100-500nm, and the particles are uniformly mixed with the binder CMC at a mass ratio of 90:10 to obtain a ZIF porous material slurry. The ZIF porous material slurry is sprayed on the surface of the microsphere material by spray drying with a thickness of 800nm ​​to obtain a composite microsphere material. The structural schematic diagram is shown in FIG. Figure 1 shown.

[0144] (4) Preparation of current collector:

[0145] The composite microsphere material and the binder CMC were stirred and mixed evenly in a ratio of 90:10, and evenly coated on both surfaces of the copper foil by spray drying to form a functional coating with a single-side thickness of 1 μm.

[0146] Example 2a:

[0147] The only difference between this embodiment and embodiment 1 is that the high-temperature titaniumization reaction temperature for the preparation of the precursor is 1200°C.

[0148] Example 2b:

[0149] The only difference between this embodiment and embodiment 1 is that the high-temperature titaniumization reaction temperature for the precursor preparation is 800° C. and the reaction time is 6 hours.

[0150] Example 2c:

[0151] The only difference between this embodiment and embodiment 1 is that the high-temperature titaniumization reaction temperature for the precursor preparation is 1400° C. and the reaction time is 2 h.

[0152] Example 3a:

[0153] The only difference between this embodiment and embodiment 1 is that the particle size of the polyethylene microspheres is different. The particle size of this embodiment is 800 nm.

[0154] Example 3b:

[0155] The only difference between this embodiment and embodiment 1 is that the particle size of the polyethylene microspheres is different. The particle size of this embodiment is 100 nm.

[0156] Example 3c:

[0157] The only difference between this embodiment and embodiment 1 is that the particle size of the polyethylene microspheres is different. The particle size of this embodiment is 1000 nm.

[0158] Comparative Example 1:

[0159] The only difference between this comparative example and Example 1 is that the composite microsphere material does not have copper metal properties.

[0160] Comparative Example 2:

[0161] The only difference between this comparative example and Example 1 is that the high-temperature titanization reaction temperature is 600°C.

[0162] Comparative Example 3:

[0163] The only difference between this comparative example and Example 1 is that the composite microspheres do not have a porous structure, that is, no ammonium bicarbonate particles are added in the preparation of the hollow three-dimensional skeleton precursor in step (1).

[0164] Comparative Example 4:

[0165] The only difference between this comparative example and Example 1 is that the composite microspheres have no hollow structure, that is, polyethylene microspheres are not used in the preparation of the hollow three-dimensional skeleton precursor in step (1).

[0166] Performance test of current collector and composite microsphere materials:

[0167] Test methods include:

[0168] (1) Specific surface area: The specific surface area is expressed in N 2 The adsorption method is used to measure the specific surface area of ​​the composite microsphere material by the amount of gas adsorption;

[0169] (2) Maximum compaction density: The current collector was passed through a roller press under different pressure conditions, and the maximum compaction density was 3.2, 3.3, 3.4, 3.5, and 3.6 g / cm 3 Under the compaction density of , the cross-section scanning electron microscope (SEM) and argon ion polishing (CP) technology are used to determine whether the functional coating material is broken;

[0170] (3) Weight: Cut the current collector into a size of 10 × 10 cm and weigh it;

[0171] (4) Conductivity: The conductivity is measured by a powder level resistivity test. A certain amount of composite microsphere material is placed in a test container. The same mass of material is pressed into a dense block under a certain pressure condition (5 tons of pressure), and its resistivity is tested in this state.

[0172] Table 1: Physical and chemical tests of current collector and composite microsphere materials

[0173]

[0174] The specific surface area test shows that Examples 1-3 have a larger specific surface area, a higher maximum compaction density, and good conductivity;

[0175] In Comparative Example 1, the copper metal is eliminated, which reduces the structural strength of the composite microspheres, which is manifested in a lower maximum compaction density, which easily causes structural collapse, and the conductivity results show that the conductivity is also reduced accordingly;

[0176] Comparative Example 2 reduces the titaniumization temperature, which reduces the structural strength of the composite microspheres, which is manifested in a lower maximum compaction density and easily causes structural breakage;

[0177] In Comparative Example 3, ammonium bicarbonate was eliminated, which significantly reduced the specific surface area of ​​the composite microspheres;

[0178] Although the compaction density can be increased to a certain extent after the hollow structure is eliminated in Comparative Example 4, the specific surface area is reduced too much, which affects the transmission of lithium ions.

[0179] Battery preparation and performance testing:

[0180] 1. Preparation of batteries:

[0181] (1) Negative electrode:

[0182] The negative electrode sheet used the current collector prepared in the above examples and comparative examples.

[0183] (2) Preparation of positive electrode sheet:

[0184] The positive electrode active material is NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), the conductive agent is conductive carbon black (SP) and carbon nanotubes, the binder is polyvinylidene fluoride (PVDF5130), and the positive electrode current collector is 13μm aluminum foil. The positive electrode active material, SP, carbon nanotubes, and binder are mixed in a ratio of 97:1.5:0.5:1, and N-methylpyrrolidone (NMP) is added and stirred to form a uniform and stable positive electrode slurry. The positive electrode slurry is evenly coated on the positive electrode current collector, and the coating surface density is 195g / m 2 After drying and cold pressing, the positive electrode sheet is obtained, and the compaction density is 3.4g / cm 3 .

[0185] (3) Selection of isolation membrane:

[0186] A polypropylene film is selected as the isolation film base film, and the isolation film structure includes: 9μm polyethylene (PE) base film+3μm ceramic coating layer (CSC)+3μm polyvinylidene fluoride (PVDF) adhesive coating layer (PCS)+3μm PCS.

[0187] (4) Battery cell assembly process:

[0188] Arrange the positive electrode sheet, separator, current collector and separator in order, and assemble them in sequence by stacking.

[0189] (5) Preparation of electrolyte:

[0190] Select LiPF 6 Dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 1:1:1, with a concentration of 1.2 mol / L.

[0191] (6) Preparation of batteries:

[0192] The electrolyte was injected into the dry battery cell, and after soaking for 24 hours, the battery cell was formed at 45°C. The formation process was as follows: charge at 0.05C to 3.4V, and then charge at 0.2C to 3.75V. The battery cell was completed after aging at room temperature for 24 hours.

[0193] 2. Battery performance test:

[0194] The test standard method is as follows:

[0195] (1) DC internal resistance ACR test: The battery is charged and discharged according to the standard 0.5C / 1C charging and discharging system: let it stand for 30 minutes, charge it to 4.25V at 0.5C constant current and constant voltage, let it stand for 30 minutes, and then discharge it at 1C constant current for 0.5h, that is, discharge it to 50% SOC, and use a DC internal resistance meter to test the DC internal resistance of the battery;

[0196] (2) 0.5C / 1C cycle 500 cycles capacity retention test: The charge and discharge test was carried out according to the standard test process 0.5C / 1C system, the process is: stand for 30 minutes, charge to 4.25V at 0.5C constant current and constant voltage, stand for 30 minutes, and then discharge to 2.5V at 1C current constant current; test the capacity retention rate of 500 cycles until the discharge capacity of the battery is less than 80% of the initial capacity and stop the test;

[0197] (3) 1C energy density = 1C discharge capacity × 1C discharge average voltage / total weight of the battery;

[0198] (4) Gas volume test: The gas volume test is carried out by the water displacement method and measured using a volume tester. According to the initial weight m1 of the battery cell and the mass m2 immersed in water, the buoyancy of the battery cell in water = ρgV, which is proportional to the weight. The density ρ of water and the mass acceleration g are known, so the volume V = (m1-m2) / ρg;

[0199] (5) Hot box test: The battery is charged and discharged according to the standard charging and discharging system: let it stand for 30 minutes, charge it to 4.25V at 0.5C constant current and constant voltage, place it in a hot box, heat it to 130℃ at a heating rate of 5℃ per minute and keep it for half an hour. Observe it for half an hour. If there is no fire or smoke, continue to heat it at a rate of 5℃ and test the failure temperature in turn every 5℃ until the battery fails. The temperature at this time is the failure temperature.

[0200] (6) Maximum charge rate test: The standard charge and discharge process is as follows: let stand for 30 minutes, charge to 4.25V at 0.5C constant current and constant voltage, let stand for 30 minutes, then discharge to 2.5V at 1, 2, or 3C constant current until the battery has thermal runaway. The rate at this time is the maximum charge rate of a battery without a negative electrode, which indirectly reflects the safety performance of the current collector structure.

[0201] Table 2: Battery performance characterization

[0202]

[0203]

[0204] From the relevant electrical performance test results, the electrochemical performance of the current collector prepared by the present invention shows good results, and the energy density, power performance, and safety performance of the embodiment are better than those of the comparative example;

[0205] The results of comparative example 1 show that the internal resistance of the battery increases significantly. This is because the composite microspheres have no copper metal support. On the one hand, the pressure resistance is reduced, which reduces the material per unit volume of the battery and affects the energy density. On the other hand, the conductivity is poor, which increases the internal resistance and polarization of the battery, thereby reducing the rate performance and safety performance of the battery.

[0206] Compared with the embodiment, in Comparative Example 2, the titaniumization temperature is lowered, so that the compaction density of the microspheres is reduced, which reduces the energy density to a certain extent. In addition, the conductivity of the material is strongly related to the temperature, and the conductivity is also partially affected. Therefore, the battery polarization is slightly increased, and the cycle and rate performance of the battery are deteriorated.

[0207] Compared with the embodiment, in Comparative Example 3, due to the cancellation of pore formation, the specific surface area of ​​the composite material is reduced, and the gas adsorption capacity is reduced, thereby reducing the safety performance of the battery. In addition, due to the reduction in gas adsorption, the battery is affected by more gas, which makes the contact between the pole pieces worse, deteriorates the conductivity of the battery, and deteriorates the polarization of the battery, thereby also causing the deterioration of the cycle and energy density.

[0208] Compared with the embodiment, in Comparative Example 4, since the hollow structure is eliminated, the weight of the material itself becomes heavier, which reduces the energy density of the battery. In addition, due to the solid structure, the specific surface area is reduced, which also deteriorates the gas adsorption capacity of the battery, resulting in the deterioration of the battery cycle and rate performance.

[0209] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A current collector, characterized in that: The current collector comprises: a) negative electrode current collector matrix; b) a functional coating, the functional coating being disposed on at least one surface of the negative electrode current collector substrate in a thickness direction; the functional coating comprising a composite microsphere material having a core-shell structure, and sequentially comprising a core, a first shell layer, a second shell layer and a third shell layer from the inside to the outside; The core is a copper metal microsphere with a hollow structure; The first shell layer comprises a metal carbide having a porous structure, wherein the porous structure comprises copper metal; The second shell layer includes copper metal; The third shell layer includes a porous material.

2. The current collector according to claim 1, characterized in that: The metal carbide includes at least one of titanium carbide, tungsten carbide and zirconium carbide; The porous material includes at least one of ZIF, MOF, and COF; The negative electrode current collector matrix includes one of copper foil, titanium foil, nickel mesh, stainless steel foil and carbon cloth.

3. The current collector according to claim 1, characterized in that: The diameter of the core is 110-1100 nm; the diameter of the hollow structure is 100-1000 nm; The thickness of the first shell layer is 500-2000 nm, the porosity is 5%-20%, and the pore size of the pore structure is 50-200 nm; The thickness of the second shell layer is 10 to 100 nm; The thickness of the third shell layer is 500-1000 nm; The thickness of the functional coating on one side is 0.5-10 μm.

4. The current collector according to claim 1, characterized in that: The mass ratio of the metal carbide, copper metal and porous material is (5-20): (40-80): (20-40); And / or, the first shell layer further includes a carbon material, and the mass percentage of the metal carbide in the first shell layer is 10% to 90%.

5. The current collector according to claim 1, characterized in that: The third shell layer also includes a first binder; The mass ratio of the porous material in the third shell layer to the first binder is (80-95):(5-20); And / or, the functional coating further comprises a second binder; The mass ratio of the composite microsphere material to the second binder in the functional coating is (80-95): (5-20); The first binder and the second binder independently include at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

6. A method for preparing a current collector, characterized in that: The steps include: S1, mixing a pore-forming agent and a third binder to obtain a pore-forming agent slurry, coating the pore-forming agent slurry on the surface of a polymer microsphere, drying the obtained material, dissolving the polymer microsphere, washing with water, and drying to obtain a hollow porous precursor material; Mixing the hollow porous precursor material and a metal salt solution, and subjecting the mixture to a first soaking treatment to obtain a first soaked material; In an inert gas atmosphere, the first soaked material is contacted with an alkane gas, and subjected to a first high-temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material; S2, mixing the metal carbide three-dimensional skeleton precursor material and the solution containing copper ions, and subjecting the mixture to a second soaking treatment to obtain a second soaked material; under the action of a reducing agent, the copper ions in the second soaked material are reduced to copper metal to obtain a microsphere precursor material; subjecting the microsphere precursor material to a second high-temperature treatment to obtain a microsphere material, wherein the microsphere material is a microsphere material having a hollow structure and a copper metal microsphere surface composited with a first shell layer and a second shell layer; S3, preparing a porous material to obtain a porous material slurry, and coating the porous material slurry on the surface of the microsphere material to obtain a composite microsphere material; S4, preparing the composite microsphere material to obtain a composite microsphere material slurry, coating the composite microsphere material slurry on the surface of the negative electrode current collector substrate, and drying to obtain a current collector.

7. The preparation method according to claim 6, characterized in that: In the step S1, the pore-forming agent includes at least one of ammonium bicarbonate, ammonium chloride, and ammonium nitrate; The third binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid; The mass ratio of the pore former to the third binder is (90-95):(5-10); The polymer microspheres include at least one of polyethylene microspheres, polystyrene microspheres, polyethylene microspheres, polyvinyl chloride microspheres, and polypropylene microspheres; The metal salt solution includes at least one of a titanium tetrachloride aqueous solution, a tungsten tetrachloride aqueous solution, and a zirconium chloride aqueous solution; The concentration of the metal salt solution is 0.01 to 0.5 mol / L; The first immersion treatment time is 0.5 to 2 hours; The alkane gas includes at least one of methane, ethane, propane and butane; The temperature of the first high temperature treatment is 800-1400° C., and the time of the first high temperature treatment is 2-6 hours.

8. The preparation method according to claim 6, characterized in that: In step S2, the solution containing copper ions includes at least one of a copper sulfate solution, a copper nitrate solution, and a copper chloride solution; The concentration of the solution containing copper ions is 0.1-0.5 mol / L; The second immersion treatment time is 2 to 4 hours; The reducing agent includes at least one of hydrazine hydrate, iron and zinc; The temperature of the second high temperature treatment is 600-800° C., and the time of the second high temperature treatment is 2-4 hours.

9. The preparation method according to claim 6, characterized in that: In the step S3, the porous material is prepared to obtain a porous material slurry by mixing the porous material and a first binder to prepare a porous material slurry; In the step S4, the composite microsphere material is prepared to obtain composite microsphere material slurry by mixing the composite microsphere material and the second binder to obtain the composite microsphere material slurry.

10. A negative electrode-free battery, characterized in that: The negative electrode-free battery comprises the current collector according to any one of claims 1 to 5, and / or the current collector prepared by the preparation method according to any one of claims 6 to 9.

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