Elastic current collector and preparation method and application thereof

Abstract

The invention provides an elastic current collector and a preparation method and application thereof. The elastic current collector comprises a metal foil and an elastic carbon interface layer arranged on at least one side surface of the metal foil, and the elastic carbon interface layer comprises an elastic carbon material, a conductive additive and a binder; the elastic carbon material comprises hollow carbon and / or biomass-based porous carbon, and the surface and the interior of the biomass-based porous carbon are both provided with pore structures. According to the invention, hollow carbon and / or biomass-based porous carbon are / is used as an elastic carbon material, mixed with the conductive additive and the binder, and then coated on the surface of at least one side of the metal foil to form the elastic carbon interface layer, so that the surface roughness of the current collector is increased and the interface stress is dynamically reduced without influencing the electrochemical performance of the electrode; therefore, the electrochemical stability of the electrode is effectively improved, and the preparation method is simple and suitable for large-scale application.

Description

Technical Field

[0001] The invention belongs to the field of secondary batteries and relates to an elastic current collector and a preparation method and application thereof. Background Art

[0002] Silicon negative electrode has a capacity of up to 3579mAh / g, and it is low-cost and abundant in reserves, making it an ideal negative electrode for the next generation of lithium-ion batteries. However, the interfacial bonding between the silicon negative electrode and the traditional copper foil current collector is weak. When undergoing volume expansion during the charge and discharge process, the conductive interface stress between the silicon negative electrode coating and the current collector continues to accumulate, resulting in interface disconnection and electrochemical performance degradation. At present, the optimization of silicon negative electrodes focuses on active material modification, binder optimization, and conductive agent development, with less attention paid to current collectors. In order to improve the interfacial bonding between the silicon negative electrode active material coating and the current collector, existing methods include increasing the surface roughness of the copper foil current collector, improving the surface viscosity of the current collector, and developing elastic composite current collectors.

[0003] For example, CN117117078A discloses a lithium-ion battery and a negative electrode plate thereof, which increases the contact area between the copper current collector and the negative electrode active material by adopting a copper current collector with a certain roughness, thereby strengthening the physical interlocking between the negative electrode active material and the copper current collector, and suppressing the problem of plate demolding; CN119008970A discloses a highly conductive and highly viscous current collector carbon-coated slurry, which obtains a modified adhesive with high viscosity by ester exchange reaction of polyvinyl alcohol and methyl methacrylate, thereby improving the bonding strength between the current collector and the active material; CN111211330A discloses a flexible lithium-ion battery, which improves the compressible elasticity of the current collector by coating a conductive silver layer on a porous mesh film as a current collector, thereby achieving the effect of alleviating interface stress.

[0004] However, increasing the surface roughness of copper foil can enhance the interfacial bonding strength between the silicon negative electrode coating and the current collector, but it cannot reduce the accumulation of interfacial stress, resulting in limited improvement in the performance of the silicon negative electrode; improving the surface viscosity of the current collector through organic polymer coating will reduce the interfacial electronic conductivity, increase the interfacial resistance and cannot relieve the interfacial stress; elastic current collectors can relieve interfacial stress and improve electrochemical performance, but the charging and discharging effects under large currents are limited.

[0005] Therefore, how to develop a current collector that can effectively alleviate the interfacial stress between the current collector and the electrode coating without negatively affecting the electrochemical performance of the electrode is an urgent problem to be solved. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an elastic current collector and a preparation method and application thereof. The present invention uses hollow carbon and / or biomass-based porous carbon as elastic carbon materials, mixes with conductive additives and binders, and then applies them on at least one side of the metal foil to form an elastic carbon interface layer. Without affecting the electrochemical performance of the electrode, the roughness of the current collector surface is increased, the interfacial stress is dynamically reduced, and the interface is permanently connected to maintain conductive connection, which effectively improves the electrochemical stability of the electrode. The preparation method is simple and suitable for large-scale application.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an elastic current collector, the elastic current collector comprising a metal foil and an elastic carbon interface layer disposed on at least one surface of the metal foil, the elastic carbon interface layer comprising an elastic carbon material, a conductive additive and a binder;

[0009] The elastic carbon material includes hollow carbon and / or biomass-based porous carbon, and the surface and interior of the biomass-based porous carbon have pore structures at the same time.

[0010] In the present invention, by arranging an elastic carbon interface layer including hollow carbon and / or biomass-based porous carbon on at least one side of the metal foil, the roughness of the current collector surface can be improved, and the bonding sites between the current collector and the electrode coating can be increased. Moreover, since the hollow carbon and / or biomass-based porous carbon have a certain compression elasticity, the stress at the interface between the electrode and the current collector can be relieved and the stability of the interfacial electronic conductive interface can be increased. In addition, the use of biomass-based porous carbon as the elastic carbon interface layer also has the advantage of low cost and is suitable for large-scale applications.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the thickness of the elastic carbon interface layer is 0.5-2 μm, for example 0.5 μm, 0.7 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm or 2 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] In the present invention, different thicknesses of the elastic carbon interface layer can be selected according to the degree of volume change of the electrode material used during use; by controlling the thickness of the elastic carbon interface layer within the range of 0.5 to 2 μm, the stability and conductivity of the current collector can be better taken into account, so that the current collector can effectively buffer the electrode stress.

[0014] Preferably, the average particle size of the elastic carbon material is 0.5-5 μm, for example 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the wall thickness of the hollow carbon is 5 to 20 nm, for example, 5 nm, 7 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the porosity of the biomass-based porous carbon is 10 to 90%, for example 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In the present invention, by regulating the wall thickness of the hollow carbon and / or the porosity of the biomass-based porous carbon, the compressible elasticity and conductivity of the interface layer can be regulated; by controlling the wall thickness of the hollow carbon to 5 to 20 nm and the porosity of the biomass-based porous carbon to 10% to 90%, the electrode can achieve a better balance between conductivity and buffering electrode strain effect.

[0018] Preferably, when the elastic carbon material includes the hollow carbon and the biomass-based porous carbon, the mass ratio of the hollow carbon and the biomass-based porous carbon is (5-50):(50-95), for example, 5:95, 10:90, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55 or 50:50, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In the present invention, when two elastic carbon materials are used, by controlling the mass ratio of hollow carbon and biomass-based porous carbon within the range of (5-50):(50-95), the material can better achieve a balance between electrode electrochemical performance, strain resistance and cost.

[0020] Preferably, the mass ratio of the elastic carbon material, the conductive additive and the binder in the elastic carbon interface layer is (25-45):(25-45):(10-30), for example, 25:45:30, 30:40:30, 35:50:15, 40:40:20, 45:30:25 or 45:45:10, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In the present invention, by adjusting the mass ratio of the elastic carbon material, the conductive additive and the binder in the elastic carbon interface layer, especially the proportion of the elastic carbon material, the compressible elasticity, conductivity and roughness of the elastic layer can be adjusted, and then the connection strength between the electrode coating and the current collector can be adjusted to achieve different degrees of buffering electrode stress.

[0022] In a second aspect, the present invention provides a method for preparing an elastic current collector as described in the first aspect, the preparation method comprising: evenly dispersing an elastic carbon material, a conductive additive and a binder in a solvent to obtain a conductive slurry, then coating the obtained conductive slurry on a metal foil, and drying to obtain the elastic current collector.

[0023] In the present invention, the elastic carbon interface layer can be prepared by uniformly dispersing the elastic carbon material, the conductive additive and the binder in a solvent and then coating the same on a metal foil. The method is simple and applicable to the preparation of any electrode and is suitable for large-scale application.

[0024] Preferably, the mixing method includes stirring or sanding.

[0025] Preferably, the coating method includes coating or gravure printing.

[0026] Preferably, the preparation process of the hollow carbon includes: introducing a carbon source into a quartz tube, depositing a graphitized carbon layer on a template by chemical vapor deposition to obtain a template / graphitized carbon layer composite, and then etching the template in the template / graphitized carbon layer composite with a solvent to obtain the hollow carbon.

[0027] Preferably, in the method for preparing the hollow carbon, the template comprises any one of silicon dioxide, magnesium oxide, zinc oxide, iron oxide or magnesium carbonate.

[0028] Preferably, the average particle size of the template is 0.5-5 μm, for example 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In the present invention, hollow carbon with different pore sizes can be prepared by using templates with different particle sizes, and a better anti-strain effect can be achieved by controlling the average particle size of the template within the range of 0.5 to 5 μm.

[0030] Preferably, the carbon source comprises a liquid carbon source or a gaseous carbon source.

[0031] Preferably, the liquid carbon source includes any one of acetonitrile, methanol or ethanol.

[0032] Preferably, the gaseous carbon source comprises methane or acetylene.

[0033] Preferably, the heating rate of the chemical vapor deposition is 15 to 25°C / min, for example, 15°C / min, 16°C / min, 17°C / min, 18°C / min, 19°C / min, 20°C / min, 21°C / min, 22°C / min, 23°C / min, 24°C / min or 25°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the temperature of the chemical vapor deposition is ≥700°C, for example 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the chemical vapor deposition time is 20 to 180 min, for example 20 min, 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min or 180 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In the present invention, the wall thickness of the hollow carbon can be adjusted by regulating the temperature and / or time of chemical vapor deposition, and can be freely selected according to needs in practical applications.

[0037] Preferably, the liquid carbon source is introduced into the quartz tube by an inert gas.

[0038] Preferably, the flow rate of the inert gas or the gaseous carbon source is 150 to 200 mL / min, for example 150 mL / min, 160 mL / min, 170 mL / min, 180 mL / min, 190 mL / min or 200 mL / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the inert gas or the gaseous carbon source is introduced before the heating begins, and the ventilation time is 10 to 20 minutes, for example, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes or 20 minutes, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] The present invention does not limit the preparation process of biomass-based porous carbon. Exemplarily, the present invention provides a method for preparing biomass-based porous carbon, which comprises: calcining a biomass material in a protective gas atmosphere to obtain the biomass-based porous carbon.

[0041] Preferably, the biomass material includes any one of lily pollen, rapeseed pollen, pine pollen, rice straw, wheat straw, corn straw or bamboo powder, or a combination of at least two of them.

[0042] In the present invention, the sources of biomass materials are wide, which can effectively reduce costs.

[0043] Preferably, the flow rate of the protective gas is 50 to 200 mL / min, for example, 50 mL / min, 70 mL / min, 100 mL / min, 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min or 200 mL / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the protective gas comprises argon.

[0045] Preferably, protective gas is introduced before the temperature rises, and the ventilation time is 10 to 20 minutes, for example 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes or 20 minutes, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the heating rate of calcination is 15 to 20°C / min, for example, 15°C / min, 16°C / min, 17°C / min, 18°C / min, 19°C / min or 20°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Preferably, the calcination temperature is 800-1000°C, such as 800°C, 850°C, 900°C, 950°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Preferably, the calcination holding time is 0.5 to 2 h, for example, 0.5 h, 0.8 h, 1.0 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2.0 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In the present invention, the porosity of the biomass-based porous carbon can be adjusted by regulating the calcination temperature and / or time.

[0050] Preferably, the calcined product is washed, filtered and dried in sequence.

[0051] The cleaning includes first cleaning in an acid solution and then second cleaning in deionized water.

[0052] Preferably, the acid solution comprises a hydrochloric acid solution.

[0053] Preferably, the concentration of the acid solution is 0.05-1M, for example 0.05M, 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, 0.7M, 0.8M, 0.9M or 1.0M, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] Preferably, the conductive additive includes any one of carbon black, acetylene black, Ketjen black, carbon nanotubes or carbon fibers, or a combination of at least two thereof.

[0055] Preferably, the binder includes any one of polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, sodium carboxymethyl cellulose, sodium alginate, styrene-butadiene rubber or polyvinylidene fluoride, or a combination of at least two thereof.

[0056] Preferably, the metal foil material includes any one of copper foil, aluminum foil, composite copper foil, composite aluminum foil or nickel foil.

[0057] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0058] (1) preparing an elastic carbon material: placing a template in a quartz tube, introducing a carbon source into the quartz tube at a flow rate of 150 to 200 mL / min for 10 to 20 min, then heating the quartz tube to ≥700°C at a heating rate of 15 to 20°C / min, and depositing a graphitized carbon layer for 20 to 180 min to obtain a template / graphitized carbon layer composite, then preparing a 2.5 to 5 mol / L sodium hydroxide solution, placing the template / graphitized carbon layer composite in the sodium hydroxide solution, etching the template in the template / graphitized carbon layer composite, and then washing the product with deionized water, filtering and drying it in sequence to obtain the elastic carbon material;

[0059] (2) preparing a conductive paste: adding an elastic carbon material, a conductive additive and a binder into a solvent in a mass ratio of (25-45):(25-45):(10-30), and dispersing them uniformly by stirring or sand grinding to obtain the conductive paste;

[0060] (3) Preparing an elastic current collector: coating the conductive paste obtained in step (2) on a metal foil by coating or gravure printing, and drying to obtain the elastic current collector.

[0061] In a third aspect, the present invention provides a negative electrode for a lithium ion battery, wherein the negative electrode for the lithium ion battery comprises the elastic current collector as described in the first aspect.

[0062] Preferably, the lithium-ion battery negative electrode comprises a silicon-based negative electrode.

[0063] It is understandable that among the currently used battery negative electrode materials, silicon-based negative electrodes have higher capacity, but their volume changes greatly during use. The elastic current collector provided by the present invention is particularly suitable for such electrode materials with large volume changes.

[0064] In a fourth aspect, the present invention further provides a lithium ion battery, wherein the lithium ion battery comprises the lithium ion battery negative electrode as described in the second aspect.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] The elastic current collector provided by the present invention can improve the roughness of the current collector surface, increase the bonding sites between the current collector and the electrode coating, relieve the stress at the interface between the electrode and the current collector, and increase the stability of the interfacial electronic conductive interface. By using biomass-based porous carbon as the elastic carbon material, it also has the significant advantage of low cost; moreover, the preparation method of this elastic current collector is simple and suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the structure of the elastic current collector provided in Example 1.

[0068] Figure 2 It is a schematic diagram of the preparation process of the elastic current collector provided in Example 1.

[0069] Figure 1 Middle: 1-elastic carbon interface layer; 2-conductive additive; 3-metal foil. DETAILED DESCRIPTION

[0070] The technical scheme of the present invention is further illustrated by specific examples below. Those skilled in the art should understand that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0072] Example 1

[0073] This embodiment provides an elastic current collector, such as Figure 1 As shown, it is composed of a metal foil 3 and an elastic carbon interface layer 1, a conductive additive 2 and a binder arranged on one side of the metal foil 3, wherein the metal foil is a copper foil, the elastic carbon interface layer is 1 μm thick and is composed of hollow carbon with a pore size of 1 μm and a wall thickness of 10 nm, the conductive additive is carbon black SP, and the binder is lithium polyacrylate. Figure 2 As shown, the preparation method of the elastic carbon current collector is: first prepare the elastic carbon material, then prepare the conductive slurry, and finally prepare the elastic carbon current collector, as follows:

[0074] (1) Preparation of hollow carbon:

[0075] A SiO2 template with an average particle size of 1 μm is placed in a quartz tube, a carbon source is introduced into the quartz tube at a flow rate of 200 mL / min for 15 min, and then the quartz tube is heated to 900°C at a heating rate of 20°C / min, and a graphitized carbon layer is deposited for 1 h to obtain a template / graphitized carbon layer composite, and then a 3 mol / L sodium hydroxide solution is prepared, and the template / graphitized carbon layer composite is placed in the sodium hydroxide solution to etch the template, and then the product is washed with deionized water, filtered and dried in sequence to obtain a hollow carbon;

[0076] (2) preparing a conductive slurry: adding an elastic carbon material, a conductive additive and a binder in a mass ratio of 40:40:20 to deionized water, stirring at a stirring speed of 500 rpm for 5 h to obtain a conductive slurry;

[0077] (3) Preparation of elastic current collector: The conductive slurry obtained in step (2) was coated on a copper foil using a 5 μm scraper, and then dried at 80° C. to obtain an elastic current collector.

[0078] Example 2

[0079] This embodiment provides an elastic current collector, which is composed of a metal foil and an elastic carbon interface layer, a conductive additive and a binder arranged on one surface of the foil, wherein the metal foil is a copper foil, the elastic carbon interface layer has a thickness of 0.5 μm and is composed of biomass-based porous carbon with a porosity of 60%, the conductive additive is Ketjen black, and the binder is lithium polyacrylate. The preparation method of the elastic carbon current collector is as follows:

[0080] (1) Preparation of biomass-based porous carbon:

[0081] The carbonized wheat straw was placed in a quartz tube, argon gas was introduced into the quartz tube at a gas flow rate of 100 mL / min for 15 min, and then the temperature was increased to 900°C at a heating rate of 20°C / min, and the temperature was kept for 1 h. After cooling to room temperature, the calcined product was washed in a hydrochloric acid solution with a concentration of 0.07 M, and then washed for a second time in deionized water, and porous carbon was obtained after filtering and drying;

[0082] (2) preparing a conductive slurry: adding an elastic carbon material, a conductive additive and a binder in a mass ratio of 25:45:30 to deionized water, stirring at a stirring speed of 500 rpm for 5 h to obtain a conductive slurry;

[0083] (3) Preparation of elastic current collector: The conductive slurry obtained in step (2) is coated on a copper foil using a 2 μm scraper, and then dried at 80° C. to obtain an elastic current collector.

[0084] Example 3

[0085] This embodiment provides an elastic current collector, which is composed of a metal foil and an elastic carbon interface layer, a conductive additive and a binder arranged on one surface of the metal foil, wherein the metal foil is a copper foil, the thickness of the elastic carbon interface layer is 2 μm, and it is composed of hollow carbon with a pore size of 1 μm and a wall thickness of 10 nm and biomass-based porous carbon with a porosity of 60%, the mass ratio of the hollow carbon to the biomass-based porous carbon is 20:80, the conductive additive is Ketjen black, and the binder is lithium polyacrylate. The preparation method of the elastic carbon current collector is as follows:

[0086] (1) Preparation of hollow carbon: placing a SiO2 template with an average particle size of 1 μm in a quartz tube, introducing a carbon source into the quartz tube at a flow rate of 200 mL / min for 15 min, then heating the quartz tube to 900°C at a heating rate of 20°C / min, and depositing a graphitized carbon layer for 1 h to obtain a template / graphitized carbon layer composite, then preparing a 3 mol / L sodium hydroxide solution, placing the template / graphitized carbon layer composite in the sodium hydroxide solution, etching the template in the template / graphitized carbon layer composite, and then washing the product with deionized water, filtering and drying it in sequence to obtain hollow carbon;

[0087] (2) Preparation of biomass-based porous carbon: Carbonized wheat straw was placed in a quartz tube, argon gas was introduced into the quartz tube at a gas flow rate of 100 mL / min for 15 min, and then the temperature was increased to 900°C at a heating rate of 20°C / min, and the temperature was kept for 1 h. After cooling to room temperature, the calcined product was washed in a 0.07 M hydrochloric acid solution, and then washed again in deionized water. After filtering and drying, porous carbon was obtained;

[0088] (3) preparing a conductive slurry: firstly, hollow carbon and biomass-based porous carbon were mixed in a mass ratio of 20:80 to obtain an elastic carbon material, and then the elastic carbon material, a conductive additive and a binder were added thereto in a ratio of 45:25:30 in deionized water, and stirred at a stirring speed of 500 rpm for 5 h to obtain a uniform dispersion to obtain a conductive slurry;

[0089] (4) Preparation of elastic current collector: The conductive slurry obtained in step (3) was coated on the copper foil using a 10 μm scraper, and then dried at 80° C. to obtain an elastic current collector.

[0090] Example 4

[0091] The difference between this embodiment and embodiment 1 is that the elastic carbon interface layer is composed of hollow carbon with a pore size of 0.5 μm, the conductive additive is acetylene black, the current collector is aluminum foil, and in the preparation method, a SiO2 template with an average particle size of 0.5 μm is used in step (1).

[0092] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0093] Example 5

[0094] The difference between this embodiment and embodiment 2 is that the conductive additive is carbon nanotubes, and in the preparation method, Ketjen black is replaced by carbon nanotubes in step (2).

[0095] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0096] Example 6

[0097] The difference between this embodiment and embodiment 2 is that the conductive additive is carbon fiber, and in the preparation method, carbonized bamboo powder is used as a carbon source in step (1), and Ketjen black is replaced by carbon fiber in step (2).

[0098] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0099] Example 7

[0100] The difference between this embodiment and embodiment 1 is that the thickness of the elastic carbon interface layer is 0.3 μm, and in the preparation method, it is coated on the copper foil by a 1 μm scraper.

[0101] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0102] Example 8

[0103] The difference between this embodiment and embodiment 1 is that the thickness of the elastic carbon interface layer is 5 μm, and in the preparation method, it is coated on the copper foil by a 20 μm scraper.

[0104] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0105] Example 9

[0106] The difference between this embodiment and embodiment 1 is that in the preparation method, in step (2), elastic carbon material, conductive additive and binder are added thereto in a mass ratio of 10:70:20.

[0107] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0108] Example 10

[0109] The difference between this embodiment and embodiment 1 is that in the preparation method, in step (2), elastic carbon material, conductive additive and binder are added thereto in a mass ratio of 70:10:20.

[0110] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0111] Embodiment 11

[0112] The difference between this embodiment and embodiment 1 is that in the preparation method, in step (2), hollow carbon and biomass-based porous carbon are mixed in a mass ratio of 3:97 to form an elastic carbon material.

[0113] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0114] Example 12

[0115] The difference between this embodiment and embodiment 1 is that in the preparation method, in step (2), hollow carbon and biomass-based porous carbon are mixed in a mass ratio of 95:5 to form an elastic carbon material.

[0116] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0117] Example 13

[0118] The difference between this embodiment and embodiment 1 is that the wall thickness of the hollow carbon is 3 nm, and in the preparation method, in step (1), the time of chemical vapor deposition is 15 min.

[0119] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0120] Embodiment 14

[0121] The difference between this embodiment and embodiment 1 is that the wall thickness of the hollow carbon is 25 nm, and in the preparation method, in step (1), the time of chemical vapor deposition is 200 min.

[0122] The structural parameters and preparation methods of the remaining elastic current collectors are consistent with those in Example 1.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 1 is that the current collector is composed of a metal foil, a conductive additive and a binder, and in the preparation method, step (1) is not performed, and no elastic carbon material is added in step (2).

[0125] The structural parameters and preparation methods of the remaining current collectors are consistent with those in Example 1.

[0126] Comparative Example 2

[0127] The difference between this comparative example and Example 1 is that the current collector is a copper foil with a certain roughness, and no other preparation process is required.

[0128] Application Example 1

[0129] The electrode active material and the solvent are mixed evenly, and coated on the elastic current collector provided in Example 1. The copper foil is placed in a vacuum drying oven at 80°C for 5 hours for drying, then taken out and pressed into small discs. The small discs are weighed and the mass is recorded. The small discs are placed in a glove box to assemble button batteries.

[0130] Application Example 2-14

[0131] The difference between this application example and application example 1 is that the electrode active material and the solvent are mixed evenly and coated on the elastic current collector provided in Example 2-14.

[0132] Other preparation parameters were consistent with those in Application Example 1.

[0133] Comparative Application Example 1-2

[0134] The difference between Comparative Application Example 1-2 and Application Example 1 is that the electrode active material and the solvent are mixed evenly and coated on the elastic current collector provided by Comparative Example 1-2.

[0135] Other preparation parameters were consistent with those in Application Example 1.

[0136] Performance Testing

[0137] The long cycle performance of the batteries prepared in Application Examples 1-14 and Comparative Application Examples 1-2 was tested with a current density of 0.2C, and the cycle performance of the batteries under high current was tested with a current density of 1C. The measured electrochemical properties of the batteries are shown in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] From the data comparison of application examples 1-6 and comparative application examples 1 and 2 in Table 1, it can be seen that the positive electrode sheet or negative electrode sheet obtained by using the elastic current collector provided by the present invention shows better cycle performance than that using the traditional current collector. This also shows that in the present invention, whether hollow carbon or porous carbon, or a combination of the two is selected as the elastic carbon material, and it is mixed with a conductive additive and a binder to form an elastic carbon interface layer, the interface can maintain a permanent conductive connection, so that the battery shows better cycle performance, and effectively improves the electrochemical stability of the electrode.

[0142] From the data comparison of Application Examples 7-8 and Application Example 1 in Table 1, it can be seen that when the thickness of the elastic carbon interface layer is controlled in the range of 0.5 to 2 μm, the capacity retention rate of the battery after 200 cycles at 0.2C and 1C is higher, which means that when the thickness of the elastic carbon interface layer is in the range of 0.5 to 2 μm, the obtained current collector can better balance stability and conductivity.

[0143] From the data comparison of Application Examples 9-12 and Application Example 1 in Table 1, it can be seen that changing the mass proportion of the elastic carbon material in the elastic carbon interface layer or changing the mass ratio of hollow carbon and biomass-based porous carbon will also affect the cycle performance of the battery; by controlling the mass ratio of the elastic carbon material, the conductive additive and the binder in the elastic carbon interface layer within the range of (25-45):(25-45):(10-30), and controlling the mass ratio of hollow carbon and biomass-based porous carbon within the range of (5-50):(50-95), the obtained elastic carbon interface layer can play a better role in buffering electrode stress.

[0144] From the data comparison between Application Examples 13-14 and Application Example 1 in Table 1, it can be seen that the wall thickness of the graphite carbon sphere can be adjusted by regulating the time of chemical vapor deposition. By controlling the wall thickness of the hollow carbon within the range of 5 to 20 nm, the elastic carbon interface layer can also play a better role in buffering the electrode stress, so that the battery can show better cycle performance.

[0145] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An elastic current collector, characterized in that: The elastic current collector comprises a metal foil and an elastic carbon interface layer disposed on at least one side of the metal foil, wherein the elastic carbon interface layer comprises an elastic carbon material, a conductive additive and a binder; The elastic carbon material includes hollow carbon and / or biomass-based porous carbon, and the surface and interior of the biomass-based porous carbon have pore structures at the same time.

2. The elastic current collector according to claim 1, characterized in that: The thickness of the elastic carbon interface layer is 0.5 to 2 μm; Preferably, the average particle size of the elastic carbon material is 0.5 to 5 μm; Preferably, the wall thickness of the hollow carbon is 5 to 20 nm; Preferably, the porosity of the biomass-based porous carbon is 10% to 90%; Preferably, when the elastic carbon material includes the hollow carbon and the biomass-based porous carbon, the mass ratio of the hollow carbon to the biomass-based porous carbon is (5-50):(50-95); Preferably, the mass ratio of the elastic carbon material, the conductive additive and the binder in the elastic carbon interface layer is (25-45):(25-45):(10-30).

3. A method for preparing an elastic current collector as claimed in claim 1 or 2, characterized in that: The preparation method comprises: uniformly dispersing elastic carbon material, conductive additive and binder in a solvent to obtain conductive slurry, then coating the obtained conductive slurry on a metal foil, and drying to obtain the elastic current collector.

4. The method for preparing the elastic current collector according to claim 3, characterized in that: The mixing method includes stirring or sanding; Preferably, the coating method includes coating or gravure printing.

5. The method for preparing the elastic current collector according to claim 3 or 4, characterized in that: The preparation process of the hollow carbon comprises: introducing a carbon source into a quartz tube, depositing a graphitized carbon layer on a template by chemical vapor deposition to obtain a template / graphitized carbon layer composite, and then etching the template in the template / graphitized carbon layer composite with a solvent to obtain the hollow carbon; Preferably, in the method for preparing the hollow carbon, the template comprises any one of silicon dioxide, magnesium oxide, zinc oxide, iron oxide or magnesium carbonate; Preferably, the average particle size of the template is 0.5 to 5 μm; Preferably, the carbon source comprises a liquid carbon source or a gaseous carbon source; Preferably, the liquid carbon source includes any one of acetonitrile, methanol or ethanol; Preferably, the gaseous carbon source comprises methane or acetylene.

6. The method for preparing the elastic current collector according to claim 5, characterized in that: The heating rate of the chemical vapor deposition is 15-20°C / min; Preferably, the temperature of the chemical vapor deposition is ≥700°C; Preferably, the chemical vapor deposition time is 20 to 180 minutes; Preferably, the liquid carbon source is introduced into the quartz tube by an inert gas; Preferably, the flow rate of the inert gas or the gaseous carbon source is 150 to 200 mL / min; Preferably, the inert gas or the gaseous carbon source is introduced before the temperature rise begins, and the ventilation time is 10 to 20 minutes.

7. The method for preparing an elastic current collector according to any one of claims 3 to 6, characterized in that: The conductive additive includes any one of carbon black, acetylene black, Ketjen black, carbon nanotubes or carbon fibers, or a combination of at least two thereof; Preferably, the binder comprises any one of polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, sodium carboxymethyl cellulose, sodium alginate, styrene-butadiene rubber or polyvinylidene fluoride, or a combination of at least two thereof; Preferably, the metal foil material includes any one of copper foil, aluminum foil, composite copper foil, composite aluminum foil or nickel foil.

8. The method for preparing an elastic current collector according to claim 3, characterized in that: The preparation method comprises the following steps: (1) preparing an elastic carbon material: placing a template in a quartz tube, introducing a gaseous carbon source into the quartz tube at a flow rate of 150 to 200 mL / min for 10 to 20 min, then heating the quartz tube to ≥700°C at a heating rate of 15 to 20°C / min, and depositing a graphitized carbon layer for 20 to 180 min to obtain a template / graphitized carbon layer composite, then preparing a 2.5 to 5 mol / L sodium hydroxide solution, placing the template / graphitized carbon layer composite in the sodium hydroxide solution, etching the template in the template / graphitized carbon layer composite, and then washing the product with deionized water, filtering and drying it in sequence to obtain the elastic carbon material; (2) preparing a conductive paste: adding an elastic carbon material, a conductive additive and a binder into a solvent in a mass ratio of (25-45):(25-45):(10-30), and dispersing them uniformly by stirring or sand grinding to obtain the conductive paste; (3) Preparing an elastic current collector: coating the conductive paste obtained in step (2) on a metal foil by coating or gravure printing, and drying to obtain the elastic current collector.

9. A negative electrode for a lithium ion battery, characterized in that: The negative electrode of the lithium-ion battery comprises the elastic current collector as claimed in claim 1 or 2; Preferably, the lithium-ion battery negative electrode comprises a silicon-based negative electrode.

10. A lithium ion battery, characterized in that: The lithium ion battery comprises the lithium ion battery negative electrode as claimed in claim 9.

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