A dry electrode pole piece, a preparation method and application thereof

Abstract

The application relates to a dry-process electrode tab and a preparation method and application thereof. The preparation method of the dry-process electrode tab comprises the following steps: step A: mixing and stirring an active material, a conductive agent and a binder to obtain dry powder with uniform mixing; adding a certain amount of coupling agent dispersion liquid and stirring at a certain temperature to obtain fibrous powder; step B: extruding the fibrous powder to obtain a sheet, rolling the sheet into an electrode tab film, and performing hot roller pressing on the electrode tab film and a current collector to obtain the dry-process electrode tab. The coupling agent is introduced into the preparation process of the secondary battery dry-process electrode tab, the use amount of the binder is reduced, the proportion of the conductive carbon content is increased, some problems existing in the preparation process of the dry-process electrode tab are optimized, the film resistance is reduced, and the peeling strength of the electrode tab is greatly improved.

Description

Technical Field

[0001] This invention relates to the technical field of sodium-ion batteries, and in particular to a dry-process electrode sheet, its preparation method, and its application. Background Technology

[0002] Dry electrode technology is an electrode preparation process that involves mixing active materials, conductive agents, and binders at high speed to obtain fibrous electrode powder, which is then continuously hot-rolled and thermally bonded to a current collector to form the electrode sheet. Dry electrode preparation offers lower production costs, higher efficiency, and is environmentally friendly as it does not use organic solvents. Applying dry electrode technology in sodium-ion battery manufacturing can significantly reduce costs and mitigate the risk of declining competitiveness due to falling lithium carbonate prices. However, some challenges remain in dry electrode preparation, such as high film resistance and poor peel strength, which affect the battery's electrochemical performance. These issues require further solutions and optimization. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a dry electrode sheet, its preparation method, and its application. This invention introduces a coupling agent into the preparation process of the dry electrode sheet for secondary batteries, reducing the amount of binder used, increasing the proportion of conductive carbon, optimizing some existing problems in the dry electrode preparation process, and significantly improving the peel strength of the electrode sheet while reducing film resistance.

[0004] The first objective of this invention is to provide a method for preparing a dry electrode sheet, comprising the following steps:

[0005] Step A: Stir and mix the active material, conductive agent, and binder to obtain a uniformly mixed dry powder; add a certain amount of coupling agent dispersion and stir at a certain temperature to obtain a fibrous powder.

[0006] Step B: The fibrous powder is extruded to obtain a sheet with a thickness of 250-400 μm, and rolled into an electrode film. The electrode film and the current collector are hot rolled together to obtain the dry electrode sheet.

[0007] The inorganic component of the coupling agent in the coupling agent dispersion is 40% to 76%.

[0008] In one embodiment of the present invention, in step A, the active material is selected from positive electrode active materials or negative electrode active materials.

[0009] In one embodiment of the present invention, the positive electrode active material is selected from one or more of sodium-ion layered oxides, polyanionic materials, Prussian blue materials, lithium-ion ternary materials, lithium cobalt oxide, lithium iron phosphate, and lithium manganese iron phosphate; the negative electrode active material is selected from one or more of hard carbon materials, graphite materials, silicon carbide materials, sodium titanate, lithium titanate, and alloy-type negative electrode materials.

[0010] In one embodiment of the present invention, in step A, the amount of coupling agent added to the dispersion of active material, conductive agent, binder, and coupling agent satisfies the following: active material 93.5wt% to 98wt%, conductive agent 1.5wt% to 5wt%, binder 0.6wt% to 1wt%, and coupling agent 0.2wt% to 0.5wt%.

[0011] In one embodiment of the present invention, in step A, the coupling agent dispersion comprises a coupling agent and a dispersion solvent, wherein the mass ratio of the coupling agent to the dispersion solvent is 1:2 to 3. The coupling agent in the coupling agent dispersion is selected from one or more of γ-aminopropyltriethoxysilane, aluminum zirconium coupling agent LD-139, zirconate coupling agent FD-NZ97, or zirconate ester coupling agent KENREACT NZ 38.

[0012] In one embodiment of the present invention, in step A, the stirring speed for mixing the active material, conductive agent and binder is 100-300 r / min and the stirring time is 0.5-2 h.

[0013] In one embodiment of the present invention, in step A, the stirring conditions for stirring at a certain temperature are: stirring speed of 1000-3500 r / min and stirring time of 1-3 h.

[0014] In one embodiment of the present invention, step B satisfies at least one or more of the following conditions:

[0015] The extrusion molding temperature is 40–120°C;

[0016] The temperature of the hot roll pressing composite is 100-200℃;

[0017] The temperature at which the electrode film is rolled into a thin film is 80–150°C.

[0018] The thickness of the electrode film is 120–200 μm.

[0019] A second objective of this invention is to provide a dry electrode sheet obtained by the aforementioned preparation method.

[0020] A third objective of the present invention is to provide a secondary battery comprising the aforementioned dry electrode sheet.

[0021] The technical solution of the present invention has the following advantages compared with the prior art:

[0022] This invention introduces coupling agents into the dry electrode fabrication process for secondary batteries, offering the following advantages: 1. Adding coupling agents significantly improves the adhesion properties of PTFE and greatly enhances the flexibility of PTFE-reinforced composite materials. Therefore, introducing coupling agents into the dry electrode fabrication process can significantly improve the peel strength of the dry electrode sheets. 2. Because the addition of coupling agents enhances the adhesion properties of PTFE, the PTFE content can be reduced and the conductive agent content increased during the dry electrode fabrication process. This helps to reduce the film resistance of the electrode sheet and optimize the poor rate performance caused by the dry electrode. 3. The dry electrode fabrication process does not require the addition of toxic organic solvents, resulting in no emissions of toxic gases, no pollution, and no residue. It also eliminates the need for ovens and NMP recovery devices required in the wet electrode coating process, effectively reducing the cost of sodium-ion battery fabrication and aligning with the principles of "green, environmentally friendly, cost-effective, and energy-saving." Attached Figure Description

[0023] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0024] Figure 1 This is a SEM image of the dry electrode sheet obtained in Embodiment 1 of the present invention;

[0025] Figure 2 This is a SEM image of the dry electrode sheet in Comparative Example 2 of the present invention. Detailed Implementation

[0026] In order to solve the technical problems pointed out in the background art, the present invention proposes a dry electrode sheet, its preparation method and application.

[0027] This invention is achieved through the following scheme:

[0028] This invention provides a method for preparing a dry electrode sheet, comprising the following steps:

[0029] Step A: Stir and mix the active material, conductive agent, and binder to obtain a uniformly mixed dry powder; add a certain amount of coupling agent dispersion and stir at a certain temperature to obtain a fibrous powder.

[0030] Step B: The fibrous powder is extruded to obtain a sheet with a thickness of 250-400 μm, and rolled into an electrode film. The electrode film and the current collector are hot rolled together to obtain the dry electrode sheet.

[0031] The inorganic characteristic portion of the coupling agent in the coupling agent dispersion is 40% to 76%. Further, it is preferably 57.7% to 75.4%.

[0032] In specific embodiments, in step A, the active material is selected from a positive electrode active material or a negative electrode active material.

[0033] In specific embodiments, the positive electrode active material is selected from one or more of sodium-based layered oxides, polyanionic materials, Prussian blue materials, lithium-based ternary materials, lithium cobaltate, lithium iron phosphate and lithium manganese iron phosphate; the negative electrode active material is selected from one or more of hard carbon materials, graphite materials, silicon-carbon materials, sodium titanate, lithium titanate and alloy-type negative electrode materials.

[0034] Further, the positive electrode active material is a sodium-ion battery layered oxide positive electrode material NaNi i Fe j Mn k M m O₂;

[0035] Further, the layered metal oxide satisfies: 0.6 < x ≤ 1, 0 < i ≤ 0.4, 0 < j ≤ 0.5, 0 < k ≤ 0.6, 0 < m ≤ 0.2, i + j + k + m = 1;

[0036] Still further, when 0.6 < x ≤ 0.8, the material is a P2-phase layered oxide; when 0.8 < x ≤ 1, the material is an O3-phase layered oxide.

[0037] In specific embodiments, in step A, the addition amounts of the active material, conductive agent, binder, and coupling agent in the coupling agent dispersion satisfy: 93.5wt% to 98wt% of the active material, 1.5wt% to 5wt% of the conductive agent, 0.6wt% to 1wt% of the binder, and 0.2wt% to 0.5wt% of the coupling agent.

[0038] Further, the conductive agent is a conventional conductive agent in the art, which is not particularly limited herein, and may be one or more of SuperP, Ketjen black, carbon nanotubes, carbon nanofibers, graphene, and conductive carbon. It is preferably carbon nanotubes and carbon nanofibers.

[0039] Further, the binder is a conventional binder in the art, which is not particularly limited herein, and may be one or more of polyvinylidene fluoride (PVDF), acrylic resin (PAA), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), polyether ether ketone (PEEK), polyether block amide (PEBA), polyurethane (TPU), and polyhexamethylene adipamide (PA66); further, polytetrafluoroethylene (PTFE) is preferred.

[0040] In a specific embodiment, in step A, the coupling agent dispersion is a mixed solution of coupling agent and dispersing solvent, and the mass ratio of coupling agent to dispersing solvent is 1:2 to 3.

[0041] In a specific embodiment, the coupling agent in the coupling agent dispersion is selected from one or more of γ-aminopropyltriethoxysilane, aluminum zirconium coupling agent LD-139, zirconate coupling agent FD-NZ97, or zirconate ester coupling agent KENREACT NZ 38. Further, the coupling agent is preferably a zirconate ester coupling agent. More preferably, the zirconate ester coupling agent of the present invention has a high proportion of inorganic components, ranging from 57.7% to 75.4%, thus providing more inorganic reaction sites and enhancing the interaction with the surface of inorganic powders.

[0042] The organic groups on silane coupling agents lack sufficient reactivity with thermoplastic resins such as polyethylene, polypropylene, polystyrene, and ABS, resulting in poor coupling effects in these systems. This invention enhances the interaction with the surface of inorganic powders by using zirconate coupling agents with high inorganic content and silane coupling agents. In contrast, many existing silane coupling agents in the art have an inorganic content of less than 40%, resulting in too few inorganic reaction sites and affecting the coupling effect between the coupling agent and the inorganic powder.

[0043] Furthermore, the dispersing solvent is ethanol.

[0044] In a specific embodiment, in step A, the stirring speed for mixing the active material, conductive agent, and binder is 100-300 r / min, and the stirring time is 0.5-2 h.

[0045] In a specific embodiment, in step A, the stirring conditions for stirring at a certain temperature are: stirring speed of 1000-3500 r / min and stirring time of 1-3 h.

[0046] In a specific embodiment, step B requires at least one or more of the following conditions to be met:

[0047] The extrusion molding temperature is 40–120°C;

[0048] The temperature of the hot roll pressing composite is 100-200℃;

[0049] The temperature at which the electrode film is rolled into a thin film is 80–150°C.

[0050] The thickness of the electrode film is 120–200 μm.

[0051] This invention provides a dry electrode sheet obtained by the aforementioned preparation method.

[0052] The present invention provides a secondary battery, including the dry electrode sheet.

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0054] Example 1

[0055] This embodiment provides a method for preparing a dry electrode sheet, which can be used as the positive electrode of a sodium-ion battery. The preparation method includes:

[0056] 1. The positive electrode material O3-NaNi 0.34 Fe 0.33 Mn 0.33 O2, carbon nanotubes, and PTFE were mixed in a mixing tank at a mass percentage of 97.5%, 1.3%, and 0.8% respectively, at a speed of 200 r / min to obtain a uniformly mixed dry powder. Then, a zirconate coupling agent KENREACT NZ 38 dispersion at a mass percentage of 0.4 wt% was added. The stirring temperature was controlled at 55℃, and the stirring speed was adjusted to 5500 r / min. The high-speed shear force generated by the high-intensity stirring ensured the uniform dispersion of the active material, conductive agent, binder, and coupling agent, achieving a fibrous effect and yielding a fibrous powder.

[0057] 2. The fibrous powder is extruded in an extruder at 80°C to obtain a sheet with a thickness of 350μm; the obtained sheet is rolled at 120°C to form an electrode film with a thickness of 180μm; finally, the electrode film and the aluminum foil current collector are hot rolled together at 150°C to obtain the positive electrode of the sodium ion dry electrode.

[0058] Example 2

[0059] This embodiment was prepared entirely according to the scheme of Example 1, except that the positive electrode material O3-NaNi was added. 0.34 Fe 0.33 Mn 0.33 The mass ratios of O2, carbon nanotubes, PTFE, and zirconate coupling agent are 97.5 wt%, 1.7 wt%, 0.6 wt%, and 0.2 wt%, respectively.

[0060] Example 3

[0061] This embodiment was prepared entirely according to the scheme of Example 1, except that the positive electrode material O3-NaNi was added. 0.34 Fe 0.33 Mn 0.33 The mass ratios of O2, carbon nanotubes, PTFE, and zirconate coupling agent are 97 wt%, 1.5 wt%, 1 wt%, and 0.5 wt%, respectively.

[0062] Example 4

[0063] This embodiment was prepared entirely according to the scheme of Example 1, except that the coupling agent added was γ-aminopropyltriethoxysilane (KH-550).

[0064] Comparative Example 1

[0065] 1. The positive electrode material O3-NaNi 0.34 Fe 0.33 Mn 0.33 O2, carbon nanotubes, and PTFE are mixed in a mixing tank at a mass percentage of 97.5%, 1.7%, and 0.8% respectively, at a speed of 200 r / min to obtain a uniformly mixed dry powder. The mixing temperature is controlled at 55℃ and the mixing speed is adjusted to 5500 r / min. The high-speed shear force generated by the high-intensity mixing makes the conductive materials, conductive agents, and binders uniformly dispersed, achieving a fibrous effect.

[0066] 2. The fibrous powder is extruded at 80°C to obtain a sheet with a thickness of 350μm; the obtained sheet is rolled at 120°C to form a positive electrode film with a thickness of 180μm; finally, the positive electrode film and the aluminum foil current collector are hot rolled together at 150°C to obtain the sodium ion dry electrode positive electrode.

[0067] Comparative Example 2

[0068] This comparative example was prepared exactly according to the scheme of Comparative Example 1, except that the positive electrode material O3-NaNi was added. 0.34 Fe 0.33 Mn 0.33 The mass ratios of O2, carbon nanotubes, and PTFE are 97.5%, 0.5%, and 2%, respectively.

[0069] Comparative Example 3

[0070] This embodiment was prepared entirely according to the scheme of Example 1, except that the coupling agent added was methyltrimethoxysilane coupling agent (the proportion of inorganic components was less than 40%).

[0071] Performance testing

[0072] The peeling force and film resistance of the positive electrode plates obtained in the examples and comparative examples were tested, and the experimental results are shown in Table 1.

[0073] Table 1. Electrode peeling force and diaphragm resistance of Examples 1-3 and Comparative Examples 1-3

[0074]

[0075]

[0076] As shown in Table 1, Examples 1-4, which are dry electrode sheets prepared using the method of the present invention, all exhibit high peel strength, low film resistance, and excellent flexibility. Comparative Example 1 uses the preparation method of Example 1, except that no zirconate coupling agent is added. With the same PTFE mass (0.8%), the peel strength is significantly lower than that of Examples 1-3, the adhesion performance of the surface electrode is poor, and the flexibility of the electrode is low. This indicates that the addition of the zirconate coupling agent helps to enhance the adhesion performance of the thermoplastic resin PTFE. Comparative Example 2 uses the preparation method of Comparative Example 1, except that the mass of PTFE is increased to 2%. Figure 1 , Figure 2 Scanning electron microscopy also shows that Comparative Example 2 added a relatively large amount of PTFE. Under such circumstances, the peel strength of the electrode is still lower than that of Example 1 (0.8% PTFE), and barely similar to that of Example 2 (0.6% PTFE). However, the significant increase in the PTFE content means that the proportion of conductive agent needs to be reduced, resulting in a significant increase in the film resistance of the electrode. Comparative Example 3 adopted the preparation method of Example 1, except that the zirconate coupling agent was replaced with the common silane coupling agent methyltrimethoxysilane (inorganic component proportion less than 40%). Since PTFE is a thermoplastic resin, the silane coupling agent in Comparative Example 3 has few inorganic reaction sites, resulting in poor coupling effect of the coupling agent. Therefore, its peel strength improvement effect is not significant, and the flexibility of the electrode is also poor.

[0077] The above conclusions show that zirconate coupling agents can effectively enhance the bonding performance of PTFE. Therefore, in the dry electrode preparation process, the use of binders can be reduced, thereby increasing the proportion of conductive agents. This can improve the film resistance of the electrode and enhance the rate performance of the material without reducing the bonding strength.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a dry electrode sheet, characterized in that, Includes the following steps: Step A: The active material, conductive agent, and binder are stirred and mixed to obtain a uniformly mixed dry powder; a certain amount of coupling agent dispersion is added, and the mixture is stirred at a certain temperature to obtain a fibrous powder; the amount of coupling agent added in the active material, conductive agent, binder, and coupling agent dispersion meets the following requirements: active material 93.5wt%~98wt%, conductive agent 1.5wt%~5wt%, binder 0.6wt%~1wt%, coupling agent 0.2wt%~0.5wt%; the coupling agent is selected from one or more of aluminum zirconium coupling agent LD-139, zirconate coupling agent FD-NZ97, or zirconate coupling agent KENREACT NZ 38; the binder is PTFE; Step B: The fibrous powder is extruded to form a thin sheet, which is then rolled into an electrode film. The electrode film and the current collector are then hot-rolled together to obtain the dry electrode sheet. The inorganic component of the coupling agent in the coupling agent dispersion is 40% to 76%.

2. The preparation method according to claim 1, characterized in that, In step A, the active material is selected from positive electrode active materials or negative electrode active materials.

3. The preparation method according to claim 2, characterized in that, The positive electrode active material is selected from one or more of sodium-ion layered oxides, polyanionic materials, Prussian blue materials, lithium-ion ternary materials, lithium cobalt oxide, lithium iron phosphate, and lithium manganese iron phosphate; the negative electrode active material is selected from one or more of hard carbon materials, graphite materials, silicon carbide materials, sodium titanate, lithium titanate, and alloy negative electrode materials.

4. The preparation method according to claim 1, characterized in that, In step A, the coupling agent dispersion comprises a coupling agent and a dispersing solvent, wherein the mass ratio of the coupling agent to the dispersing solvent is 1:2~3.

5. The preparation method according to claim 1, characterized in that, In step A, the active material, conductive agent, and binder are mixed at a stirring speed of 100~300 r / min for a stirring time of 0.5~2 h.

6. The preparation method according to claim 1, characterized in that, In step A, the stirring conditions at a certain temperature are as follows: stirring speed is 1000~3500 r / min, and stirring time is 1~3 h.

7. The preparation method according to claim 1, characterized in that, In step B, at least one or more of the following conditions must be met: The extrusion molding temperature is 40~120℃; The temperature of the hot roll pressing composite is 100~200℃; The thickness of the sheet is 250~400μm; The temperature at which the electrode film is rolled into a thin film is 80~150℃; The thickness of the electrode film is 120~200μm.

8. A dry-process electrode sheet, characterized in that, Obtained by the preparation method according to any one of claims 1-7.

9. A secondary battery, characterized in that, Includes the dry electrode sheet as described in claim 8.

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