A method for preparing a self-supporting electrode and a dry electrode sheet

Abstract

This invention provides a method for preparing a self-supporting electrode sheet. First, an electrode active material, a conductive agent, a solid additive, and a binder are mixed to obtain a mixture. Then, the mixture is fiberized and shaped to obtain the self-supporting electrode sheet. This application also provides a dry-process electrode sheet. Due to the introduction of camphene, the dry-process electrode sheet provided by this application becomes more flexible, cracking is suppressed, and rate performance is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for preparing a self-supporting electrode and a dry electrode. Background Technology

[0002] The electrode fabrication process for lithium-ion batteries can be divided into two types based on whether solvents are used: wet process and dry process. The difference between these two processes lies in their composition. In the wet process, active materials, conductive agents, and binders are mixed evenly in a solvent, followed by complex steps such as degassing and settling. The resulting electrode slurry is then coated onto a current collector, and the solvent is dried at an appropriate temperature to obtain a usable electrode. This process requires significant production space due to the use and recovery of solvents and the use of drying equipment, and can uncontrollably cause some environmental damage. In contrast, the dry process eliminates the need for any solvents during production, thus avoiding the need for complex drying and solvent recovery equipment. This achieves cost reduction, efficiency improvement, and environmental protection, making it a more advanced battery electrode processing technology. However, the dry process presents several technical challenges, such as electrode cracking due to material hardness and poor rate performance due to low electrode porosity. These issues require solutions and optimization. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a method for preparing a self-supporting electrode sheet. The self-supporting electrode sheet prepared in this application can solve the problems of electrode sheet cracking and low porosity during the preparation of dry electrode sheets, and ultimately improve the rate performance of the electrode.

[0004] In view of this, this application provides a method for preparing a self-supporting electrode, comprising the following steps:

[0005] A) The electrode active material, conductive agent, solid additive and binder are mixed to obtain a mixture; the solid additive includes camphene;

[0006] B) The mixture is fiberized and then shaped to obtain a self-supporting electrode.

[0007] Preferably, the process for preparing the mixture is as follows:

[0008] The electrode active material and the conductive agent are mixed to obtain the first mixture;

[0009] The first mixture and the solid additive are mixed to obtain a second mixture;

[0010] The second mixture and the adhesive are mixed to obtain a mixture.

[0011] Preferably, the electrode active material is selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide; based on the mixture, the content of the electrode active material is 85-99.8 wt%.

[0012] Preferably, the conductive agent is selected from one or more of carbon black, conductive graphite, carbon fiber, carbon nanotubes and graphene; based on the mixture, the content of the conductive agent is 0.1 to 5 wt%.

[0013] Preferably, the solid additive further includes one or more of starch, ammonium bicarbonate, urea, polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol; based on the mixture, the content of the solid additive is 0-5 wt% and ≠ 0.

[0014] Preferably, the adhesive is selected from one or more of methyl methacrylate, polyacrylonitrile, polyoxypropylene, polyoxyethylene, polyvinyl chloride, polyvinylidene fluoride and polytetrafluoroethylene, and the content of the adhesive is 0.1 to 5 wt% based on the mixture.

[0015] Preferably, the fiberization is performed by applying shear force to the mixture;

[0016] The device for applying shear force is selected from one or more of a planetary ball mill, a mechanical mixer, and an air jet mill.

[0017] Preferably, the forming method is multiple rolling; the thickness of the self-supporting electrode sheet is 50-400 μm.

[0018] Preferably, the method for preparing the self-supporting electrode is as follows:

[0019] The electrode active material and conductive agent are mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Then, solid additives are added and mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Next, binder is added and mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Finally, the mixture is mixed at a speed of 800-1500 rpm for 2-10 min to obtain a fibrous mixture.

[0020] The fibrous mixture is rolled multiple times to obtain a self-supporting electrode.

[0021] This application also provides a dry electrode sheet, which consists of a self-supporting electrode sheet and a current collector on its surface, wherein the self-supporting electrode sheet is a self-supporting electrode sheet prepared by the aforementioned preparation method.

[0022] This application provides a method for preparing a self-supporting electrode sheet. First, an electrode active material, a conductive agent, a solid additive, and a binder are mixed to obtain a mixture. Then, the mixture is fiberized and shaped to obtain the self-supporting electrode sheet. In the preparation of the self-supporting electrode sheet, camphene is used as a solid additive. Camphene itself has low hardness, which can reduce the hardness of the electrode sheet and suppress cracking during the electrode sheet forming process. At the same time, camphene is a volatile solid material that is easy to remove to create pores, without affecting the electrode's performance, and can increase porosity, thereby enhancing the rate performance of the electrode sheet. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the dry electrode sheet preparation process of the present invention;

[0024] Figure 2 A photograph showing the appearance of the dry electrode sheet prepared in Comparative Example 1 of this invention;

[0025] Figure 3 This is a photograph of the appearance of the dry electrode sheet prepared in Example 3 of the present invention;

[0026] Figure 4 The above are rate performance curves of the dry electrode sheets prepared in Comparative Examples 1, 2, 1, 3 and 5 of this invention. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] Dry processing has significant advantages in terms of cost, energy consumption, and environmental protection. However, its process route is not yet mature, and testing methods are not yet perfect. Problems such as electrode cracking and low porosity during preparation urgently need to be addressed, hindering its industrialization. Therefore, this invention provides a method for preparing self-supporting electrodes, using camphene as an additive. Camphene, a solid material, has low hardness; its doping can reduce the system's hardness, buffer the shear force on a unit area of ​​material, and reduce cracking during electrode rolling. Simultaneously, camphene is a volatile solid material, easily removed during the heating process of dry electrode composite, thus improving porosity without affecting the electrode's performance and enhancing its rate performance. A schematic diagram of the dry electrode preparation process in this application is shown below. Figure 1 As shown, prior to this, this application first provides a method for fabricating a self-supporting electrode, including the following steps:

[0029] A) The electrode active material, conductive agent, solid additive and binder are mixed to obtain a mixture; the solid additive includes camphene;

[0030] B) The mixture is fiberized and then shaped to obtain a self-supporting electrode.

[0031] In the preparation of the self-supporting electrode, this application first mixes the electrode active material, conductive agent, solid additive, and binder to obtain a mixture; in this application, the solid additive includes camphene. In order to ensure uniform dispersion of the conductive agent, the mixture is prepared according to the following method:

[0032] The electrode active material and the conductive agent are mixed to obtain the first mixture;

[0033] The first mixture and the solid additive are mixed to obtain a second mixture;

[0034] The second mixture and the adhesive are mixed to obtain a mixture.

[0035] In the preparation of the above mixture, if the electrode active material, solid additive, and binder are directly mixed, the binder may fibrousize and clump together, which is detrimental to the uniform distribution of the conductive agent. Therefore, as a preferred embodiment, the above-mentioned raw materials are added sequentially in the manner described above.

[0036] In this application, the electrode active material is selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide; based on the mixture, the content of the electrode active material is 85-99.8 wt%; more specifically, the electrode active material is selected from lithium nickel cobalt manganese oxide, and the content of the electrode active material is 90-97 wt%. The conductive agent is selected from one or more of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene; based on the mixture, the content of the conductive agent is 0.1-5 wt%; more specifically, the conductive agent is selected from conductive graphite, and the content of the conductive agent is 1-3 wt%. The solid additive also includes one or more of starch, ammonium bicarbonate, urea, polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol; based on the mixture, the content of the solid additive is 0-5 wt% and ≠ 0; more specifically, the solid additive is selected from camphene, and the content of the solid additive is 1-3 wt%. The adhesive is selected from one or more of methyl methacrylate, polyacrylonitrile, polyoxypropylene, polyoxyethylene, polyvinyl chloride, polyvinylidene fluoride and polytetrafluoroethylene, and the content of the adhesive is 0.1 to 5 wt% based on the mixture; the adhesive is selected from polytetrafluoroethylene and the content of the adhesive is 1 to 3 wt%.

[0037] The present application then fiberizes the mixture to obtain a fiberized mixture; the fiberization is carried out in a manner well known to those skilled in the art. In the present application, the fiberization is specifically achieved by applying shear force. The device for applying shear force includes, but is not limited to, at least one of mixing equipment such as a ball mill, a mechanical mixer, and an air jet mill. In the present application, the device for applying shear force is a planetary ball mill.

[0038] According to the present invention, the above-mentioned fibrous mixture is finally shaped to obtain a self-supporting electrode sheet; the shaping method is specifically multiple rolling; the rolling is a technique well known to those skilled in the art, and this application does not have any particular limitation on it. The thickness of the self-supporting electrode sheet is 50-400 μm, specifically, the thickness of the self-supporting electrode sheet is 100-300 μm.

[0039] In this application, the specific method for preparing the self-supporting electrode is as follows:

[0040] The electrode active material and conductive agent are mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Then, solid additives are added and mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Next, binder is added and mixed in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min. Finally, the mixture is mixed at a speed of 800-1500 rpm for 2-10 min to obtain a fibrous mixture.

[0041] The fibrous mixture is rolled multiple times to obtain a self-supporting electrode.

[0042] This application also provides a dry electrode sheet, which consists of a self-supporting electrode sheet and a current collector on its surface, wherein the self-supporting electrode sheet is a self-supporting electrode sheet prepared by the above-described preparation method.

[0043] The dry electrode sheet provided in this application is obtained by hot rolling composite of a self-supporting electrode sheet and a current collector; the hot rolling temperature is 150-200℃.

[0044] The dry electrode sheet provided by this invention becomes softer due to the addition of camphene, which suppresses cracking and significantly improves rate performance. At 2C, the discharge specific capacity of the dry electrode sheet without camphene and the dry electrode sheet with camphene are 54.3 mAh / g and 179 mAh / g, respectively.

[0045] To further understand the present invention, the preparation method of the self-supporting electrode sheet and the electrode sheet provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0046] Example 1

[0047] The mass ratio of NCM8303, SuperP, PTFE, and camphene was 95:3:1:1. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180°C to obtain a dry-prepared electrode sheet.

[0048] Example 2

[0049] The mass ratio of NCM8303, SuperP, PTFE, and camphene was 94:3:1:2. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180°C to obtain a dry-prepared electrode sheet.

[0050] Example 3

[0051] The mass ratio of NCM8303, SuperP, PTFE, and camphene was 93:3:1:3. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was ball-milled at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180°C to obtain a dry-prepared electrode sheet.

[0052] Example 4

[0053] The mass ratio of NCM8303, SuperP, PTFE, and camphene was 92:3:1:4. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180°C to obtain a dry-prepared electrode sheet.

[0054] Example 5

[0055] The mass ratio of NCM8303, SuperP, PTFE, and camphene was 91:3:1:5. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was ball-milled at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180°C to obtain a dry-prepared electrode sheet.

[0056] Comparative Example 1

[0057] The mass ratio of NCM8303, SuperP, and PTFE was 96:3:1. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, PTFE was added, and the mixture was ball-milled at 200 rpm for 30 min. Then the speed was increased to 800 rpm and the mixture was mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180℃ to obtain a dry-prepared electrode sheet.

[0058] Comparative Example 2

[0059] The mass ratio of NCM8303, SuperP, PTFE, and camphene was weighed to be 86:3:1:10. NCM8303 and SuperP were mixed in a planetary ball mill at 200 rpm for 30 min. After the mixture was homogeneous, camphene was added and mixed in a planetary ball mill at 200 rpm for 30 min. Then PTFE was added and the mixture was mixed in a planetary ball mill at 200 rpm for 30 min. The speed was then increased to 800 rpm and mixed for 5 min to obtain a fibrous mixture. The fibrous mixture was rolled multiple times until it reached a thickness of 100 μm. It was then rolled and compounded with a current collector at 180℃ to obtain a dry-prepared electrode sheet.

[0060] Figure 2 This is a photograph showing the appearance of the electrode sheet prepared in Comparative Example 1. Figure 3 This is a photograph showing the appearance of the electrode sheet prepared in Example 3. Figure 2 and Figure 3 The comparison shows that both the electrode without camphene and the electrode with camphene have a self-supporting structure, but the former has poor flexibility and more cracks on the surface, while the latter is softer and has a smoother surface. This indicates that the addition of camphene can buffer the unit area extrusion force on the electrode during rolling, making the force more evenly distributed and achieving the effect of increasing the flexibility of the electrode.

[0061] Figure 4 The graphs show the rate performance test curves of the electrodes prepared in Comparative Example 1, Comparative Example 2, Example 1, Example 3, and Example 5. As can be seen from the graphs, the rate performance is significantly enhanced after the addition of camphene. The discharge capacity differences are significant after 0.5C; at 2C, the discharge specific capacities are 54.3 mAh / g, 30 mAh / g, 105.2 mAh / g, 179 mAh / g, and 110.7 mAh / g, respectively. The significant performance improvement after the addition of camphene indicates that during the composite stage, camphene volatilizes, achieving the purpose of creating pores inside the dry electrode, increasing the wetting ability of the electrolyte, and improving the rate performance. However, the amount of camphene added must be appropriate. Too little will lead to insufficient toughening and decreased pore-forming ability, while too much may result in some residue, affecting conductivity. This phenomenon is particularly evident in Comparative Example 2, where excessive camphene disrupts the conductive network of the electrode, causing a significant decrease in conductivity.

[0062] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0063] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a self-supporting electrode tab, comprising the following steps: A) mixing an electrode active material, a conductive agent, a solid additive and a binder to obtain a mixture; the solid additive comprises camphene; the content of the solid additive is 0-5 wt% and ≠ 0, based on the mixture; B) fiberizing the mixture and then reshaping to obtain a self-supporting electrode tab; the process for preparing the mixture is specifically as follows: mixing an electrode active material and a conductive agent to obtain a first mixture; mixing the first mixture and a solid additive to obtain a second mixture; mixing the second mixture and a binder to obtain a mixture.

2. The production method according to claim 1, characterized by, the electrode active material is selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide and lithium cobaltate; the content of the electrode active material is 85-99.8 wt%, based on the mixture.

3. The preparation method according to claim 1, characterized in that, the conductive agent is selected from one or more of carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene; the content of the conductive agent is 0.1-5 wt%, based on the mixture.

4. The production method according to claim 1, characterized by, the solid additive further comprises one or more of starch, ammonium bicarbonate, urea, polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol.

5. The method of claim 1, wherein, the binder is selected from one or more of methyl methacrylate, polyacrylonitrile, polyoxypropylene, polyoxyethylene, polyvinyl chloride, polyvinylidene fluoride and polytetrafluoroethylene; the content of the binder is 0.1-5 wt%, based on the mixture.

6. The method of claim 1, wherein, the fiberizing is performed by applying a shearing force to the mixture; the device for applying the shearing force is selected from one or more of a planetary ball mill, a mechanical stirrer and an air jet mill.

7. The preparation method according to claim 1, characterized in that, the reshaping is performed by multiple rolling; the thickness of the self-supporting electrode tab is 50-400 μm.

8. The method of any one of claims 1 to 7, wherein the method further comprises the step of: the method for preparing the self-supporting electrode tab is specifically as follows: mixing an electrode active material and a conductive agent in a planetary ball mill at a speed of 200-1500 rpm for 2-60 min, then adding a solid additive in the planetary ball mill at a speed of 200-1500 rpm for 2-60 min, then adding a binder in the planetary ball mill at a speed of 200-1500 rpm for 2-60 min, and finally mixing at a speed of 800-1500 rpm for 2-10 min to obtain a fiberized mixture; multiple rolling of the fiberized mixture to obtain a self-supporting electrode tab. 9.A dry electrode tab, which is composed of a self-supporting electrode tab and a current collector on the surface of the self-supporting electrode tab; the dry electrode tab is obtained by hot rolling of the self-supporting electrode tab and the current collector; the temperature of the hot rolling is 150-200 ℃; the self-supporting electrode tab is prepared by the method according to any one of claims 1-8.

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