Three-layer current collector, lithium ion battery electrode and lithium ion battery

Abstract

The utility model provides a three-layer current collector, a lithium ion battery electrode and a lithium ion battery. The three-layer current collector comprises a first conductive non-metal layer, a polymer supporting layer and a second conductive non-metal layer which are stacked in sequence. According to the structure, the thickness of the current collector can be further reduced under the condition that the current collector has relatively high mechanical property and conductivity, and the problem that the current collector in the prior art cannot give consideration to both thinning and good mechanical property and conductivity is solved.

Description

Technical Field

[0001] The utility model relates to the field of lithium - ion batteries. Specifically, it relates to a three - layer current collector, a lithium - ion battery electrode and a lithium - ion battery. Background Art

[0002] With the development of lithium - ion battery technology, high energy density, light weight and flexibility of lithium - ion batteries have become the pursuit of people. The negative current collector of traditional lithium - ion batteries is copper foil, and the positive current collector is aluminum foil. Thinning the copper / aluminum foil (the total mass of the positive and negative current collectors accounts for about 14 - 18% of the total mass of the battery) can achieve the light weight of lithium - ion batteries, improve the energy density and reduce the cost. However, due to the limitation of preparation technology, the thinnest mass - produced copper foil can reach 6μm at present, and the thinnest mass - produced aluminum foil can reach 8μm. After they are thinned, the mechanical strength decreases, resulting in the deterioration of their processing performance.

[0003] At present, there is a new type of composite current collector with a three - layer structure, with a polymer layer in the middle and a conductive metal layer on each of the upper and lower sides. The advantage of this current collector is that it can greatly improve the safety performance of the battery and reduce the weight of the battery. However, such composite current collectors are mainly prepared by a two - step method (magnetron sputtering - electroplating in water) and a three - step method (magnetron sputtering - evaporation - electroplating in water), depositing copper or aluminum onto the middle polymer film. Among them, magnetron sputtering has high requirements for equipment, complex processes and low yield, resulting in high cost per unit area of the composite current collector. At the same time, due to the poor compatibility between the metal and the polymer film, the mechanical properties of the obtained current collector also need to be improved.

[0004] Based on this, how to thin the thickness of the current collector without reducing the mechanical strength and conductivity is an important problem faced by this field. Summary of the Utility Model

[0005] The main purpose of the utility model is to provide a three - layer current collector, a lithium - ion battery electrode and a lithium - ion battery, so as to solve the problem in the prior art that the current collector cannot balance thinning with good mechanical properties and conductivity.

[0006] To achieve the above purpose, according to one aspect of the utility model, a three - layer current collector is provided, which includes a first conductive non - metal layer, a polymer support layer and a second conductive non - metal layer stacked in sequence.

[0007] Furthermore, the thicknesses of the first conductive non - metal layer and the second conductive non - metal layer are respectively 0.5 - 3μm.

[0008] Furthermore, the thickness of the polymer support layer is 4 - 8μm.

[0009] Further, the polymer support layer is a polyamide support layer, a polyethylene terephthalate support layer, a polyimide support layer, a polyethylene support layer, a polypropylene support layer, a polystyrene support layer, a polyvinyl chloride support layer, an aramid support layer, an acrylonitrile-butadiene-styrene copolymer support layer, a polybutylene terephthalate support layer, or a poly-p-phenylenediamine terephthalamide support layer.

[0010] Further, the first conductive non-metal layer is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer, or a conductive carbon nanotube layer.

[0011] Further, the second conductive non-metal layer is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer, or a conductive carbon nanotube layer.

[0012] Further, the polymer support layer is a polyethylene support layer, and the first and second conductive non-metal layers are both conductive carbon black layers; or, the polymer support layer is a polyethylene support layer, and the first and second conductive non-metal layers are both conductive graphene layers; or, the polymer support layer is a polyethylene support layer, the first conductive non-metal layer is a conductive carbon black layer, and the second conductive non-metal layer is a conductive graphene layer.

[0013] Another aspect of the present utility model provides a lithium-ion battery electrode, comprising the above three-layer current collector.

[0014] Another aspect of the present utility model provides a lithium-ion battery, comprising the above lithium-ion battery electrode.

[0015] Further, the lithium-ion battery can be a lithium iron phosphate battery, a lithium iron manganese phosphate battery, or a lithium cobalt oxide battery.

[0016] The present utility model provides a three-layer current collector, which includes a first conductive non-metal layer, a polymer support layer, and a second conductive non-metal layer stacked in sequence. This structure can further reduce the thickness of the current collector while maintaining high mechanical properties and conductivity, solving the problem in the prior art that the current collector cannot balance thickness reduction with good mechanical properties and conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The specification drawings forming a part of this application are used to provide a further understanding of the present utility model. The schematic embodiments of the present utility model and their descriptions are used to explain the present utility model and do not constitute an improper limitation of the present utility model. In the drawings:

[0018] Figure 1 A schematic structural diagram of the three-layer current collector is shown.

[0019] Among them, each reference numeral represents the following:

[0020] 11. First conductive non-metallic layer; 12. Polymer support film; 13. Second conductive non-metallic layer. Detailed implementation manners

[0021] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0022] As described in the background art, in the prior art, the current collector cannot balance the problems of thinning and good mechanical properties and conductivity. And the present utility model provides a three-layer current collector, as Figure 1 shown, which includes a first conductive non-metallic layer 11, a polymer support layer 12, and a second conductive non-metallic layer 13 stacked in sequence.

[0023] Since the three layers in the current collector are all non-metallic layers, the compatibility and consistency between the layers are improved, and the entire current collector can exhibit better mechanical properties after being stacked; at the same time, in the present utility model, conductive non-metallic layers with good conductivity are provided on both the upper and lower surfaces of the polymer support layer 12 to improve the overall conductivity of the current collector. In addition, the materials used in the conductive non-metallic layers can better fuse with the positive and negative electrode materials in the electrode, and do not introduce other impurities or metal foreign matters, and will not have a negative impact on the battery. Due to the above reasons, the current collector in the present utility model can be made with a relatively thin thickness to meet the lightweight requirements of the battery.

[0024] In a preferred implementation manner, the thicknesses of the first conductive non-metallic layer 11 and the second conductive non-metallic layer 13 in the current collector are respectively 0.5 - 3 μm. Such a thickness can better play their conductive role, and at the same time can further control the overall thickness of the current collector to be thinner.

[0025] Preferably, the thickness of the polymer support layer 12 in the current collector is 4 - 8 μm. Such a thickness of the polymer layer can better play a supporting role, making the overall current collector exhibit better mechanical properties, enabling it to have better mechanical performance in various electrochemical reactions of the fuel cell, and thus improving the durability of the fuel cell.

[0026] In order to better maintain the mechanical properties of the obtained current collector, the polymer support layer 12 is a polyamide support layer, a polyethylene terephthalate support layer, a polyimide support layer, a polyethylene support layer, a polypropylene support layer, a polystyrene support layer, a polyvinyl chloride support layer, an aramid support layer, an acrylonitrile-butadiene-styrene copolymer support layer, a polybutylene terephthalate support layer, or a poly(p-phenylene terephthalamide) support layer. The above polymer support layers can better combine with the conductive layer, will not have a performance decline due to processes such as coating and drying during the preparation process, and can well control the preparation cost.

[0027] In some typical embodiments, it is preferably selected that the first conductive non-metal layer 11 is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer or a conductive carbon nanotube layer. The above several conductive non-metal layers can further improve the conductivity of the current collector, and at the same time have a certain strength, thereby improving its mechanical properties. Similarly, it is preferably selected that the second conductive non-metal layer 13 is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer or a conductive carbon nanotube layer.

[0028] In a preferred embodiment, the polymer support layer 12 is a polyethylene support layer, the first conductive non-metal layer 11 and the second conductive non-metal layer 13 are both conductive carbon black layers. Selecting the same kind of carbon black layer for the first and second conductive non-metal layers can further improve the overall consistency of the current collector, and obtain better mechanical properties and conductivity; or, the polymer support layer 12 is a polyethylene support layer, the first conductive non-metal layer 11 and the second conductive non-metal layer 13 are both conductive graphene layers. Selecting the same kind of graphene layer for the first and second conductive non-metal layers can further reduce the thickness of the current collector based on such single-atom layer materials; or, the polymer support layer 12 is a polyethylene support layer, the first conductive non-metal layer 11 is a conductive carbon black layer, and the second conductive non-metal layer 13 is a conductive graphene layer. The selection of this layer type can further reduce its thickness on the basis of taking into account mechanical properties and conductivity.

[0029] Another aspect of the present utility model provides a lithium-ion battery electrode, which includes the above three-layer current collector. The obtained electrode has a controllable thickness, and has good mechanical properties and conductivity, and can meet the use requirements in a fuel cell. The above battery electrode can be a positive electrode or a negative electrode.

[0030] Another aspect of the present utility model provides a lithium-ion battery, which includes the above lithium-ion battery electrode. The obtained battery has a high energy density and low cost, and has good commercial prospects.

[0031] Since the electrolyte systems of lithium iron phosphate ion batteries, lithium iron manganese phosphate ion batteries and lithium cobalt oxide ion batteries can better match the electrode based on the three-layer current collector provided by the present utility model, the above three lithium-ion batteries exhibit better electrochemical performance and application effects.

[0032] All layers of materials of the three-layer current collector in the present utility model are known materials, and the specific preparation process can also be made by using conventional film-forming methods in the art. For example, the polymer support layer 12 can be made by using methods such as casting film-forming and coating film-forming commonly used in the industry. The first conductive non-metal layer 11 and the second conductive non-metal layer 13 can be directly formed on the upper and lower surfaces of the polymer support layer 12 by using methods such as electroless plating and coating commonly used in the art. During the coating process, as long as it is considered for film-forming properties, various additives beneficial to film-forming can be added to the coating slurry according to known methods in the art, such as adhesives, wetting agents, dispersants, etc. For the convenience of operation, the present utility model exemplarily provides the following preparation method for the three-layer current collector:

[0033] First, a conductive slurry is prepared by mixing a conductive agent, an adhesive, a wetting agent, and a dispersant in a certain proportion. The solid content of each part is: conductive agent 60-80%, adhesive 10-20%, wetting agent 5-15%, and dispersant 5-15%. The proportion of the solid content of each component in this step is not limited to the above range. The polymer support layer 12 is directly selected from common existing polymer material products such as polyamide (PA), polyethylene terephthalate, polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PPE), polyvinyl chloride (PVC), aramid, acrylonitrile-butadiene-styrene copolymer (ABS), polybutylene terephthalate (PET), and poly(p-phenyleneterephthalamide) (PPTA), and there are no special restrictions on its specifications and models. Among them, the adhesive used to prepare the conductive slurry can be selected from existing materials, including but not limited to: one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, polypropylene, polyacrylic acid, polyacrylate, and styrene-butadiene copolymer. The wetting agent is selected from one or more of isopropanol, polyoxyethylene ether, mercaptan, hydrazide, and mercaptal acetal, and the selection of the wetting agent is not limited to the above several existing materials. The dispersant used to prepare the conductive slurry is selected from one or more of the following existing materials: carboxymethyl cellulose polymers, polyvinylpyrrolidone, polyethylene, polypropylene, and polyethylene glycol. Similarly, the selection of the dispersant is not limited to the above range. The above slurries are all known materials in the prior art.

[0034] Secondly, regarding the coating method of the conductive paste on the polymer support layer 12, thermal spraying, spin coating, dip coating, electroless plating, or common manual methods such as brush coating and roller coating can be used. Exemplarily, the conductive paste is transferred to a microgravure roll coating transfer tank. After the paste is circulated to remove bubbles, the conductive paste is successively coated on the upper and lower surfaces of the polymer film by the microgravure roll coating method, and a three-layer current collector is made after drying in an oven. This process has simple requirements, a high yield, a fast production speed, and low requirements for equipment. The above microgravure roll coating method is reverse coating, the coating speed is 20 - 150 m / min, the coating roll is a microgravure roll, its line number is 100 - 400, and the cell depth is 0.5 - 4 μm.

[0035] The three-layer current collector provided by the present utility model abandons the conventional method of obtaining a composite current collector by plating a metal material on the polymer surface, providing a simple and effective idea for the design of the composite current collector. The preparation method and various properties of the three-layer current collector provided by the present utility model will be further described below in conjunction with embodiments.

[0036] Example 1

[0037] Step 1: Prepare a conductive paste with a certain solid content of 30%; among them, the conductive agent paste accounts for 75% of the solid content, the binder accounts for 15% of the paste solid content, the wetting agent accounts for 5% of the paste solid content, and the dispersant accounts for 5% of the paste solid content;

[0038] Step 2: Coat the above paste on the upper surface of the polymer film by the microgravure roll coating method, and a three-layer current collector with a structure of conductive layer / polymer film / conductive layer is obtained after drying. The structural schematic diagram is shown in Figure 1 .

[0039] Example 2

[0040] Step 1: Prepare a conductive paste with a certain solid content of 40%; among them, the conductive agent paste accounts for 80% of the solid content, the binder accounts for 10% of the paste solid content, the wetting agent accounts for 5% of the paste solid content, and the dispersant accounts for 5% of the paste solid content;

[0041] Step 2: Coat the above paste on the upper surface of the polymer film by the microgravure roll coating method, and a three-layer current collector with a structure of conductive layer / polymer film / conductive layer is obtained after drying. The structural schematic diagram is also shown in Figure 1 .

[0042] Comparative Example 1 is a composite aluminum foil prepared by a certain company using magnetron sputtering - electroplating method.

[0043] Comparative Example 2 is a composite copper foil prepared by a certain company using magnetron sputtering - evaporation - electroplating method.

[0044] Table 1 shows the comparison of the electrical conductivity and mechanical properties of the above examples and comparative examples, where the tensile strength is divided into Machine Direction (MD, longitudinal) and Transverse Direction (TD, transverse).

[0045] Table 1

[0046]

[0047] As can be seen from the above examples, the above examples of the present utility model achieve a reduction in the thickness of the current collector while maintaining the mechanical properties and electrical conductivity without significant decline.

[0048] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A three-layer current collector, characterized in that: The three-layer current collector comprises a first conductive non-metallic layer (11), a polymer support layer (12) and a second conductive non-metallic layer (13) stacked in sequence.

2. The three-layer current collector according to claim 1, characterized in that: The thickness of the first conductive non-metallic layer (11) and the second conductive non-metallic layer (13) are respectively 0.5 to 3 μm.

3. The three-layer current collector according to claim 1, characterized in that: The thickness of the polymer support layer (12) is 4-8 μm.

4. The three-layer current collector according to any one of claims 1 to 3, characterized in that: The polymer support layer (12) is a polyamide support layer, a polyterephthalate support layer, a polyimide support layer, a polyethylene support layer, a polypropylene support layer, a polystyrene support layer, a polyvinyl chloride support layer, an aramid support layer, an acrylonitrile-butadiene-styrene copolymer support layer, a polybutylene terephthalate support layer or a poly(p-phenylene terephthalamide) support layer.

5. The three-layer current collector according to claim 4, characterized in that: The first conductive non-metallic layer (11) is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer or a conductive carbon nanotube layer.

6. The three-layer current collector according to claim 5, characterized in that: The second conductive non-metallic layer (13) is a conductive acetylene black layer, a conductive carbon black layer, a conductive graphite layer, a conductive graphene layer, a conductive graphene-like layer or a conductive carbon nanotube layer.

7. The three-layer current collector according to claim 6, characterized in that: The polymer support layer (12) is a polyethylene support layer, and the first conductive non-metal layer (11) and the second conductive non-metal layer (13) are both conductive carbon black layers; or, the polymer support layer (12) is a polyethylene support layer, and the first conductive non-metal layer (11) and the second conductive non-metal layer (13) are both conductive graphene layers; or, the polymer support layer (12) is a polyethylene support layer, the first conductive non-metal layer (11) is a conductive carbon black layer, and the second conductive non-metal layer (13) is a conductive graphene layer.

8. A lithium ion battery electrode, comprising a current collector, characterized in that: The current collector is a three-layer current collector according to any one of claims 1 to 7.

9. A lithium ion battery comprising a battery electrode, characterized in that: The battery electrode is the lithium-ion battery electrode according to claim 8.

10. The lithium ion battery according to claim 9, characterized in that: The lithium ion battery is a lithium iron phosphate battery, a lithium iron manganese phosphate battery or a lithium cobalt oxide battery.

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