Current collector, method for producing the same, and non-aqueous electrolyte battery

Abstract

The application 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 electrode current collector substrate and a functional coating; the functional coating comprises a composite microsphere material; the composite microsphere material has a core-shell structure and comprises, from inside to outside, an inner core, a first shell layer, a second shell layer and a third shell layer; the inner core is a copper metal microsphere with a hollow structure; the first shell layer comprises a metal carbide with a pore structure, and the pore structure comprises copper metal; the second shell layer comprises copper metal; and the third shell layer comprises a porous material. The current collector can improve the uniformity of lithium ion deposition and the conductivity, can limit the weight of the current collector, can improve the energy density, and can enhance the structural strength of the current collector.

Description

TECHNICAL FIELD

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

[0002] In order to improve the energy density of lithium batteries, more and more research efforts are put into the weight reduction design of the battery cell. The negative electrode-free battery structure greatly reduces the weight of the battery and improves the energy density of the lithium battery because it does not need negative active material. However, the negative electrode-free battery structure currently faces a serious problem. Without the lithium intercalation of the negative 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, causing the puncture of the separator, causing the short circuit of the positive and negative electrodes, and triggering 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] Patent No. CN113013417A discloses a negative electrode-free lithium metal battery structure. An electronic conductor layer and an ion conductor layer are coated on the outer layer of the traditional negative electrode current collector. Although this method can accommodate the lithium source released from the positive electrode, the patent uses a method of directly immersing the copper foil in the ion coating glue solution. The coating has no large number of pores, thus hindering the deposition speed of lithium ions on the surface of the copper foil, and the efficiency of lithium deposition is low. In severe cases, it can cause lithium dendrites to puncture the separator and trigger a short circuit due to the delayed deposition of lithium ions (high-rate charging). In addition, the preparation of the ion conductor layer is difficult, and the mass of the traditional negative electrode metal substrate is large, which affects the energy density of the battery.

[0004] Patent No. CN116581361A discloses a negative electrode-free lithium battery structure. A lithium titanate layer is provided to intercalate lithium and combine with the solid-state electrolyte, providing intercalation space and avoiding direct reaction with the electrolyte. However, the current solid-state electrolyte has low ion transmission rate and interface contact problems, which affect the power performance of the battery. In addition, the setting of the lithium titanate layer also brings weight gain, which is not conducive to the improvement of the energy density of the negative electrode-free battery.

[0005] Patent No. CN115863660B discloses a negative electrode current collector for a negative electrode-free lithium battery. The copper foil current collector surface is etched to prepare a nano-silver array to induce the deposition of lithium ions. However, this method is difficult to prepare and is not uniform, which can easily cause the penetration of the separator and trigger safety problems such as short circuit.

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

[0007] Therefore, the application provides a current collector, a preparation method thereof and a negative electrode-free battery. The current collector can improve the uniformity of lithium ion deposition and conductivity, and can also reduce the weight of the current collector, improve the energy density, and enhance the structural strength of the current collector.

[0008] In order to achieve the above-mentioned application purposes, the application provides the following technical solutions.

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

[0010] a) a negative electrode current collector substrate;

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

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

[0013] The first shell layer comprises a metal carbide having a pore structure, and the pore structure comprises copper metal;

[0014] The second shell layer comprises copper metal;

[0015] The third shell layer comprises a porous material.

[0016] In an embodiment of the application, the copper metal microsphere having a hollow structure can be spherical, ellipsoidal or irregularly spherical.

[0017] In an embodiment of the application, the metal carbide comprises at least one of titanium carbide, tungsten carbide and zirconium carbide.

[0018] In an embodiment of the application, the porous material comprises at least one of ZIF, MOF and COF.

[0019] In an embodiment of the application, the negative electrode current collector substrate comprises 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 100-1000 nm.

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

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

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

[0025] Preferably, the functional coating has a single-side thickness of 0.5-10 μm.

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

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

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

[0029] In an embodiment of the present application, the third shell layer further comprises a first binder.

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

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

[0032] Preferably, when the functional coating comprises the composite microsphere material and the 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 application, the first binder and the second binder independently comprise at least one of sodium carboxymethyl cellulose, styrene butadiene rubber and polyacrylic acid.

[0034] In a second aspect, the present application 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 a high polymer microsphere, and performing drying treatment and high polymer microsphere dissolution treatment on the obtained material, and then performing water washing and drying to obtain a hollow porous precursor material;

[0036] mixing the hollow porous precursor material and a metal salt solution to perform first soaking treatment to obtain a first soaked material, and contacting the first soaked material with an alkane gas in an inert gas atmosphere to perform first high temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material;

[0037] S2, mixing the metal carbide three-dimensional skeleton precursor material and the solution containing copper ions, and performing 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; performing a second high-temperature treatment on the microsphere precursor material to obtain a microsphere material, the microsphere material being a microsphere material with a hollow structure, and the first shell and the second shell being combined on the surface of the copper metal microsphere;

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

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

[0040] In an embodiment of the present application, 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 application, the third binder includes at least one of sodium carboxymethyl cellulose, butadiene rubber, and polyacrylic acid.

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

[0043] In an embodiment of the present application, 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 application, 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 0.01-0.5 mol / L.

[0046] Preferably, the time of the first soaking treatment is 0.5-2 h.

[0047] In an embodiment of the present application, 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 h.

[0049] In an embodiment of the present application, 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 0.1-0.5 mol / L.

[0051] Preferably, the second soaking treatment is performed for 2-4 h.

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

[0053] Preferably, the second high-temperature treatment is performed at a temperature of 600-800 ℃ for 2-4 h.

[0054] In the embodiment of the present application, in step S3, the porous material is mixed with the first binder to prepare the porous material slurry.

[0055] In the embodiment of the present application, in step S4, the composite microsphere material is mixed with the second binder to prepare the composite microsphere material slurry.

[0056] In a third aspect, the present application provides a negative-electrode-free battery comprising the current collector described above and / or prepared by the preparation method described above.

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

[0058] 1. The current collector comprises a negative-electrode current collector substrate and a functional coating arranged on the surface of the negative-electrode current collector substrate; the functional coating comprises a composite microsphere material, which has a core-shell structure and comprises, from inside to outside, a core, a first shell layer, a second shell layer and a third shell layer; the core is a copper metal microsphere having a hollow structure; the first shell layer comprises a metal carbide having a pore structure, and the pore structure contains copper metal; the second shell layer comprises copper metal; and the third shell layer comprises a porous material. The hollow structure greatly reduces the weight of the current collector and improves the energy density. Moreover, the hollow structure and the pore structure can provide a large number of site spaces for the deposition of lithium ions, improve the uniformity of lithium ion deposition, and improve the safety performance. The characteristics of the pore structure are conducive to the shuttling of lithium ions and provide a high ion transmission speed, which is conducive to the improvement of the power performance.

[0059] 2. The copper metal is deposited on the surface of the first shell layer comprising the metal carbide and in the pores. This structure not only enhances the electrical conductivity of the hollow structure and is conducive to the attraction of lithium ions, but also has metal characteristics that can enhance the compatibility with the current collector, improve the overall electrical 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 has obvious market competitiveness in the application of negative-electrode-free batteries.

[0060] When the negative current collector substrate is selected as a copper foil, 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 application can increase the gas adsorption, improve the battery safety, and prevent the excessive growth of lithium dendrites to cause the puncture short circuit of the separator. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 The figure is a schematic diagram of the structure of the composite microspheres of the application.

[0063] The reference signs are as follows:

[0064] 1: core;

[0065] 2: first shell layer;

[0066] 3: second shell layer;

[0067] 4: third shell layer. DETAILED DESCRIPTION

[0068] The application discloses a current collector, a preparation method thereof and a battery. Those skilled in the art can refer to the content herein and appropriately improve process parameters to realize. It is particularly pointed out that all similar replacements and changes are obvious to those skilled in the art, and they are regarded as included in the application. The method and application of the application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the method and application described herein without departing from the content, spirit and scope of the application, to realize and apply the technology of the application.

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

[0070] In the description of the application, the term "at least one of" or other similar terms connected to a list of items can 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 can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0071] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as exactly that endpoint. Any of the ranges or values should be interpreted as being approximate, as encompassing fractions thereof, and ranges ending with a letter designation (e.g., g), should be interpreted to also cover that numerical value (e.g., g) as an endpoint. The endpoints of the ranges and any values are also linked to the disclosure of the endpoint terms themselves, e.g., "up to 10" is an assertion of at least up to 10 and a disclosure of an exact endpoint of 10.

[0072] If there is no specific description, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0073] If there is no specific description, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0074] If there is no specific description, the "includes" and "contains" mentioned in the present application represent open type, and can also be closed type. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

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

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

[0077] a) a negative electrode current collector substrate;

[0078] b) a functional coating, the functional coating being 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, the composite microsphere material has a core-shell structure, and comprises, from inside to outside, an inner core, a first shell layer, a second shell layer, and a third shell layer;

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

[0080] The first shell layer comprises a metal carbide with a pore structure, and the pore structure comprises copper metal;

[0081] The second shell layer comprises copper metal;

[0082] The third shell layer comprises a porous material.

[0083] In an embodiment of the present application, the metal carbide comprises at least one of titanium carbide, tungsten carbide, and zirconium carbide. The metal carbide can play a role in supporting the structural strength of the composite microsphere material, and at the same time, the metal carbide has good electrical conductivity, which can improve the electrical conductivity of the negative electrode-free current collector.

[0084] In the embodiments of the present application, the core is a copper metal microsphere with a hollow structure, the first shell layer includes copper metal in the pore structure, and the second shell layer includes copper metal. The copper metal can enhance the electrical conductivity, facilitate the attraction of lithium ions, improve the structural strength of the metal carbide base layer, and has the metal characteristics that can enhance the compatibility with the current collector.

[0085] In the embodiments of the present application, the porous material includes at least one of ZIF, MOF, and COF. The porous material layer has a pore structure, can increase the gas adsorption, improve the battery safety, and prevent the excessive growth of lithium dendrites to cause the puncture short circuit of the separator.

[0086] In the embodiments of the present application, the particle size of the porous material is 100-500 nm. For example, the particle size of the porous material is any one of 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm, or any one of the values within the range formed by any two of the above values.

[0087] In the embodiments of the present application, 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 the negative electrode current collector substrate is copper foil, 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. For example, the diameter of the core is any one of 110 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, and 1100 nm, or any one of the values within the range formed by any two of the above values.

[0090] Preferably, the diameter of the hollow structure is 100-1000 nm. For example, the diameter of the hollow structure is any one of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, and 1000 nm, or any one of the values within the range formed by any two of the above values. The diameter of the hollow structure in 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 number of site spaces for the deposition of lithium ions, improve the uniformity of the lithium ion deposition, and improve the safety performance.

[0091] As preferred, 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. Exemplarily, the thickness of the first shell layer is any one of 500 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, 2000 nm, or any one of the values within the range formed by any two of the above values. The porosity is any one of 5%, 7%, 9%, 10%, 11%, 13%, 15%, 17%, 19%, 20%, or any one of the values within the range formed by any two of the above values. The pore size of the pore structure is any one of 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or any one of the values within the range formed by any two of the above values. The parameters of the first shell layer within the above ranges can provide a large number of site spaces for the deposition of lithium ions, improve the uniformity of lithium ion deposition, and improve the safety performance. Moreover, the first shell layer is conducive to the shuttling of lithium ions, provides a high ion transmission speed, and is conducive to the improvement of the power performance.

[0092] As preferred, the thickness of the second shell layer is 10-100 nm. Exemplarily, the thickness of the second shell layer is any one of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any one of the values within the range formed by any two of the above values. The thickness of the second shell layer within the range can effectively enhance the electrical conductivity, is conducive to the attraction of lithium ions, improves the structural strength of the metal carbide base layer, and the metal characteristics of the second shell layer can enhance the compatibility with the current collector.

[0093] As preferred, the thickness of the third shell layer is 500-1000 nm. Exemplarily, the thickness of the third shell layer is any one of 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or any one of the values within the range formed by any two of the above values. The thickness of the third shell layer within the range can effectively increase the gas adsorption, improve the safety of the battery, and prevent the excessive growth of lithium dendrites to cause the puncture short circuit of the separator.

[0094] As preferred, the single-side thickness of the functional coating layer is 0.5-10 μm. Exemplarily, the single-side thickness of the functional coating layer is any one of 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 one of the values within the range formed by any two of the above values.

[0095] As preferred, the mass ratio of the metal carbide, the copper metal and the porous material is (5-20):(40-80):(20-40). Exemplarily, the mass ratio of the metal carbide, the copper metal and the porous material is any value in the range of any two values selected from 1:8:8, 1:6:3, 7:45:35, 12:60:25, 1:4:1.

[0096] In the embodiment of the present application, the first shell layer further comprises a carbon material. The carbon material can serve as a carrier for the metal carbide to adhere to, and can also improve the conductivity of the anode-free current collector, and can also serve as a gas adsorption.

[0097] As preferred, when the first shell layer comprises the metal carbide and the carbon material, the mass percentage of the metal carbide in the first shell layer is 10%-90%. Exemplarily, the mass percentage of the metal carbide in the first shell layer is any value in the range of any two values selected from 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%.

[0098] In the embodiment of the present application, the third shell layer further comprises a first binder.

[0099] As preferred, when the third shell layer comprises the porous material and the 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 in the range of any two values selected from 4:1, 9:1, 95:14, 19:1.

[0100] In the embodiment of the present application, the functional coating further comprises a second binder.

[0101] As preferred, when the functional coating comprises the composite microspheres material and the second binder, the mass ratio of the composite microspheres material to the second binder in the functional coating is (80-95):(5-20). Exemplarily, the mass ratio of the composite microspheres material to the second binder is any value in the range of any two values selected from 4:1, 9:1, 95:14, 19:1.

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

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

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

[0105] mixing the hollow porous precursor material and a metal salt solution to obtain a first immersion treated material; and contacting the first immersion treated material with an alkane gas in an inert gas atmosphere and subjecting to first high temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material;

[0106] S2, mixing the metal carbide three-dimensional skeleton precursor material and a solution containing copper ions to obtain a second immersion treated material; reducing the copper ions in the second immersion treated material to copper metal under the action of a reducing agent to obtain a microsphere precursor material; and subjecting the microsphere precursor material to second high temperature treatment to obtain a microsphere material, the microsphere material being a microsphere material with a hollow structure, the surface of the copper metal microspheres being compounded with a first shell layer and a second shell layer;

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

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

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

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

[0111] After high temperature treatment, the third binder is carbonized to obtain 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). For example, the mass ratio of the pore-forming agent to the third binder is any one of 9:1, 91:7, 94:9, 19:1 or any value within the range formed by any two of the above values.

[0113] In the embodiment of the present application, the drying treatment in step S1 can gradually decompose the pore-forming agent into gas components such as CO2 and NH3, thereby leaving a pore structure. Preferably, the temperature of the drying treatment is 200-300°C, and the time of the drying treatment is 20-40 min.

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

[0115] In an embodiment of the present application, the high-molecular polymer microspheres dissolving treatment specifically includes: soaking the material after the drying treatment in a toluene solution for 4-12 hours to dissolve the high-molecular polymer microspheres.

[0116] In an embodiment of the present application, 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 0.01-0.5 mol / L. For example, the concentration of the metal salt solution is any one of 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, or any one of the values within the range formed by any two of the above values.

[0118] Preferably, the time of the first soaking treatment is 0.5-2 hours. For example, the time of the first soaking treatment is any one of 0.5 hours, 1 hour, 1.5 hours, and 2 hours, or any one of the values within the range formed by any two of the above values.

[0119] In an embodiment of the present application, 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℃, and the time of the first high-temperature treatment is 2-6 hours. For example, the temperature of the first high-temperature treatment is any one of 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, and 1400℃, or any one of the values within the range formed by any two of the above values, and the time of the first high-temperature treatment is any one of 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours, or any one of the values within the range formed by any two of the above values. When the temperature of the first high-temperature treatment is lower than 800℃, the compaction density of the hollow copper-based microspheres decreases, to some extent, reducing the energy density and making the conductivity worse and the cycle and rate performance of the battery worse. When the temperature of the first high-temperature treatment is higher than 1400℃, the pores in the composite microspheres are closed, which is not conducive to the deposition of lithium ions.

[0121] In an embodiment of the present application, 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 0.1-0.5 mol / L. For example, the concentration of the solution containing copper ions is any one of 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 formed by any two of the above values.

[0123] Preferably, the second soaking treatment is performed for 2-4 h. For example, the second soaking treatment is performed for any one of 2 h, 2.5 h, 3 h, 3.5 h, 4 h or any value within the range formed by any two of the above values.

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

[0125] Preferably, the second high-temperature treatment is performed at a temperature of 600-800 ℃ and for a time of 2-4 h. For example, the second high-temperature treatment is performed at a temperature of any one of 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃ or any value within the range formed by any two of the above values and for a time of any one of 2 h, 2.5 h, 3 h, 3.5 h, 4 h or any value within the range formed by any two of the above values.

[0126] In an embodiment of the present application, in step S3, the porous material is mixed with the first binder to prepare the porous material slurry.

[0127] In an embodiment of the present application, in step S4, the composite microsphere material is mixed with the second binder to prepare the composite microsphere material slurry.

[0128] In an embodiment of the present application, the coating method comprises at least one of spraying, extrusion coating, and transfer coating.

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

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

[0131] In an embodiment of the present application, the battery structure comprises, but is not limited to, a button cell, a soft pack battery, a cylindrical battery, and the like.

[0132] The positive electrode sheet, the separator, and the electrolyte in the battery are not particularly limited in the present application, and can be selected by a person skilled in the art according to actual needs, as long as the purpose of the present application can be achieved.

[0133] The reagents, instruments, and materials used in this invention can all be obtained through commercial channels.

[0134] The present invention will be further illustrated below with reference to the embodiments:

[0135] Example 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] Ammonium bicarbonate particles were ball-milled to prepare particles with a suitable particle size of 100 nm. Then, sodium carboxymethyl cellulose (CMC) binder was uniformly mixed with ammonium bicarbonate particles at a ratio of 95:5 and vacuum stirred into a slurry. The slurry was then spray-dried onto the surface of polyethylene (approximately 500 nm) microspheres with a coating thickness of 1000 nm. The mixture was then allowed to stand at 240 °C for 30 min. The dried material was then immersed in toluene solvent for 8 h to dissolve the polyethylene microspheres. After washing with water and drying, the hollow porous precursor material was obtained.

[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 hours. Then the immersed material was taken out and subjected to a high-temperature titaniumization reaction under N2 protection by introducing methane alkane gas. The high-temperature titaniumization reaction temperature was 1000℃ and the reaction was carried out for 4 hours to obtain the titanium carbide three-dimensional framework precursor material.

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

[0141] The above-mentioned titanium carbide three-dimensional framework precursor material was immersed in a copper sulfate solution with a concentration of 0.2 mol / L for 2 hours. Then, hydrazine hydrate reducing agent was added to the solution, and the reaction was allowed to proceed for 4 hours to obtain a composite three-dimensional material with copper elemental coating inside and on the surface of the three-dimensional framework. The composite three-dimensional material was then heated at 600°C for 2 hours to obtain microsphere material.

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

[0143] ZIF porous material was ground into particles with a size of 100-500 nm, and then mixed with binder CMC at a mass ratio of 90:10 to obtain a ZIF porous material slurry. This ZIF porous material slurry was then spray-dried onto the surface of microspheres to a thickness of 800 nm, resulting in a composite microsphere material. A schematic diagram of its structure is shown below. Figure 1 As shown.

[0144] (4) Preparation of current collector:

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

[0146] Example 2a:

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

[0148] Example 2b:

[0149] The only difference between this example and Example 1 is that the high-temperature titration reaction temperature for the preparation of the precursor is 800°C, and the reaction time is 6 h.

[0150] Example 2c:

[0151] The only difference between this example and Example 1 is that the high-temperature titration reaction temperature for the preparation of the precursor is 1400°C, and the reaction time is 2 h.

[0152] Example 3a:

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

[0154] Example 3b:

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

[0156] Example 3c:

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

[0158] Comparative Example 1:

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

[0160] Comparative Example 2:

[0161] The only difference between this comparative example and Example 1 is that the high-temperature titration 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 pore structure, i.e., no ammonium bicarbonate particles were 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 do not have a hollow structure, i.e., polyethylene microspheres are not used in the preparation of the hollow three-dimensional framework precursor in step (1).

[0166] Performance testing of the current collector and the composite microsphere material:

[0167] The test method includes:

[0168] (1) Specific surface area: The specific surface area is measured by the N2 adsorption method, and the specific surface area contained in the composite microsphere material is characterized by the adsorption amount of the gas;

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

[0170] (3) Weight: The current collector is cut into a size of 10x10 cm, and the weight is weighed;

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

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

[0173]

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

[0175] In Comparative Example 1, the copper metal is cancelled, which reduces the structural strength of the composite microspheres, which is manifested as a lower maximum compaction density, which easily causes the structure to collapse, and the conductivity result shows that the conductivity is also reduced accordingly;

[0176] In Comparative Example 2, the titaniumization temperature is reduced, which reduces the structural strength of the composite microspheres, which is manifested as a lower maximum compaction density, which easily causes the structure to break;

[0177] In Comparative Example 3, the cancellation of ammonium bicarbonate significantly reduces the specific surface area of the composite microspheres;

[0178] In Comparative Example 4, although the hollow structure is cancelled, it can improve the compaction density to a certain extent, but the specific surface area is too high, which affects the transmission of lithium ions. ​

[0179] Preparation and performance test of the battery:

[0180] 1. Preparation of the battery:

[0181] (1) Preparation of the negative electrode sheet:

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

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

[0184] The positive active material is selected from NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), the conductive agent is selected from conductive carbon black (SP) and carbon nanotubes, the binder is selected from polyvinylidene fluoride (PVDF5130), and the positive current collector is selected from 13 μm aluminum foil. The positive active material, SP, carbon nanotubes, and binder are mixed in a ratio of 97:1.5:0.5:1, N-methyl pyrrolidone (NMP) is added, and the mixture is stirred to form a uniform and stable positive electrode slurry. The positive electrode slurry is uniformly coated on the positive current collector, and the coating density is 195 g / m 2 . After drying and cold pressing, the positive electrode sheet is obtained, and the tap density is 3.4 g / cm 3 .

[0185] (3) Selection of the separator film:

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

[0187] (4) Cell assembly process:

[0188] The positive electrode sheet, the separator film, the current collector, and the separator film are arranged in order, and the assembly is performed in a stacking manner.

[0189] (5) Preparation of the electrolyte:

[0190] LiPF6 is dissolved in a solvent composed of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, and the concentration is 1.2 mol / L.

[0191] (6) Preparation of the battery:

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

[0193] 2. Performance test of the battery:

[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 charging and discharging system of 0.5C / 1C: standing for 30 min, 0.5C constant current and constant voltage charging to 4.25V, standing for 30 min, then discharging at 1C current constant current for 0.5h, i.e. discharging to the state of 50% SOC, and the DC internal resistance of the battery is tested by using a DC internal resistance tester;

[0196] (2) 0.5C / 1C cycle 500 times capacity retention rate test: the charging and discharging test is carried out according to the standard test procedure 0.5C / 1C system, the procedure is: standing for 30 min, 0.5C constant current and constant voltage charging to 4.25V, standing for 30 min, then discharging at 1C current constant current to 2.5V; test the capacity retention rate for 500 cycles, until the discharge capacity of the battery is lower than 80% of the initial capacity, stop the test;

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

[0198] (4) Gas volume test: the gas volume test is tested by using the drainage method, and the volume tester is used for measurement, according to the initial weight m1 of the battery cell, the mass m2 immersed in water, the buoyancy of the battery cell in water = pgV, and the relationship is proportional to the weight, the density p of water and the mass acceleration g are known, so the volume V = (m1-m2) / pg;

[0199] (5) Hot box test: the battery is charged and discharged according to the standard charging and discharging system: standing for 30 min, 0.5C constant current and constant voltage charging to 4.25V, placing into the hot box, heating to 130℃ at the rate of 5℃ per minute, and observing for half an hour, if there is no fire and smoke, continue to heat at the rate of 5℃, and test the failure temperature every 5℃ in turn, until the battery fails, and the temperature at this time is the failure temperature;

[0200] (6) Maximum charge rate test: according to the standard charging and discharging procedure: standing for 30 min, 0.5C constant current and constant voltage charging to 4.25V, standing for 30 min, then discharging at 1, 2, 3C current constant current to 2.5V, until the battery occurs thermal runaway, at this time the rate is the maximum charge rate of the negative electrode-free battery, 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 current collectors prepared using the application all show good results in electrochemical performance, and the energy density, power performance, and safety performance of the examples are all better than those of the comparative examples;

[0205] The results of Comparative Example 1 show that the battery internal resistance is significantly increased, because the composite microspheres have no support of copper metal, which on the one hand reduces the pressure resistance of the microspheres, reduces the material in the unit volume of the battery, and affects the energy density, and on the other hand, the electrical conductivity of the microspheres is poor, which causes the battery internal resistance and polarization to increase, thus reducing the rate performance and safety performance of the battery;

[0206] Comparative Example 2 has a lower titaniumization temperature than the examples, which reduces the compaction density of the microspheres and to some extent reduces the energy density, and in addition, the electrical conductivity of the material is strongly related to the temperature, and the electrical conductivity is also affected, thus the battery polarization is slightly increased, and the cycle and rate performance of the battery is deteriorated;

[0207] Comparative Example 3 has a lower compaction density than the examples, which reduces the specific surface area of the composite material and the gas adsorption capacity, thus reducing the safety performance of the battery, and in addition, the reduction in the gas adsorption capacity causes the battery to be more affected by the gas, which deteriorates the electrical conductivity between the electrodes and the battery polarization, thus deteriorating the cycle and energy density of the battery;

[0208] Comparative Example 4 has a higher weight than the examples due to the cancellation of the hollow structure, which reduces the energy density of the battery, and in addition, the solid structure reduces the specific surface area and deteriorates the gas adsorption capacity of the battery, thus deteriorating the cycle and rate performance of the battery.

[0209] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be considered within the protection scope of the application.

Claims

1. A current collector characterized by comprising: The current collector comprises: a) a negative electrode current collector substrate; b) a functional coating provided on at least one surface of the negative electrode current collector substrate in the thickness direction; the functional coating comprises a composite microsphere material having a core-shell structure, which comprises, from inside to outside, an inner core, a first shell layer, a second shell layer, and a third shell layer; the inner core is a copper metal microsphere having a hollow structure; the first shell layer comprises a metal carbide having a pore structure, and the pore structure comprises copper metal; the second shell layer comprises copper metal; the third shell layer comprises a porous material and a first binder, and the mass ratio of the porous material to the first binder is (80-95):(5-20); the porous material comprises at least one of ZIF, MOF, and COF.

2. The current collector of claim 1, wherein the metal carbide comprises at least one of titanium carbide, tungsten carbide, and zirconium carbide; the negative electrode current collector substrate comprises one of a copper foil, a titanium foil, a nickel mesh, a stainless steel foil, and a carbon cloth.

3. The current collector of claim 1, wherein the diameter of the inner core is 110-1100 nm; and 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 diameter of the pore structure is 50-200 nm; the thickness of the second shell layer is 10-100 nm; the thickness of the third shell layer is 500-1000 nm; the single-sided thickness of the functional coating is 0.5-10 μm.

4. The current collector of claim 1, wherein 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 comprises a carbon material, and the mass percentage content of the metal carbide in the first shell layer is 10%-90%.

5. The current collector of claim 1, wherein 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 comprise at least one of sodium carboxymethyl cellulose, styrene butadiene rubber, and polyacrylic acid.

6. A method of making the current collector of claim 1, wherein comprises the following steps: 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 high polymer microsphere, and performing drying treatment, high polymer microsphere dissolution treatment, and then water washing and drying on the obtained material to obtain a hollow porous precursor material; the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium chloride, and ammonium nitrate; and the third binder comprises at least one of sodium carboxymethyl cellulose, styrene butadiene rubber, and polyacrylic acid; mixing the hollow porous precursor material and a metal salt solution to perform first soaking treatment to obtain a first soaked material; in an inert gas atmosphere, contacting the first soaked material with an alkane gas to perform first high temperature treatment to obtain a metal carbide three-dimensional skeleton precursor material; the first high temperature treatment is performed at a temperature of 800-1400 ℃ for 2-6 h. S2, mixing the metal carbide three-dimensional skeleton precursor material and a solution containing copper ions, and performing 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; performing a second high-temperature treatment on the microsphere precursor material to obtain a microsphere material, the microsphere material being a microsphere material with a hollow structure, and the copper metal microsphere surface being compounded with a first shell layer and a second shell layer; S3, mixing the porous material and a first binder to prepare a porous material slurry, coating the porous material slurry on the surface of the microsphere material to obtain a composite microsphere material; S4, preparing a composite microsphere material slurry from the composite microsphere material, and 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 mass ratio of the pore-forming agent to the third binder is (90-95):(5-10); The high 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 0.01-0.5 mol / L; The time of the first soaking treatment is 0.5-2 h; The alkane gas includes at least one of methane, ethane, propane, and butane.

8. The preparation method according to claim 6, characterized in that, In the 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 time of the second soaking treatment is 2-4 h; 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 h.

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

10. A non-aqueous electrolyte secondary battery characterized by comprising: The anode-free battery includes the current collector of any one of claims 1-5 and / or the current collector prepared by the preparation method of any one of claims 6-9.

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