A method for preparing a thick electrode film with a high content of a high-conductivity agent and applications thereof

Abstract

The application relates to a preparation method and application of a thick electrode film with a high content of conductive agents, and a preparation process and method, which comprises the steps of wet grinding and mixing, spray granulation, low-temperature coating, fiberization, one-time hot roller pressing, electrode film compounding and the like. The application has the beneficial effects that the application not only solves the problems of a thin thickness and a low content of carbon conductive agents of an electrode film prepared by a traditional process, but also can introduce a hydrophobic binder to inhibit the dissolution of a positive electrode material in a near-neutral aqueous electrolyte, so as to solve the cycle stability problem of a near-neutral aqueous battery. In addition, the related process can improve the consistency of the electrode sheet.

Description

Technical Field

[0001] This invention relates to the field of manufacturing neutral to weakly acidic aqueous metal-ion batteries, and more specifically, to a method for preparing and applying a thick electrode film with a high conductivity agent content. Background Technology

[0002] To address global warming, countries worldwide have set greenhouse gas emission reduction targets, leading to the evolution and development of large-scale renewable energy acquisition and storage systems. Aqueous metal-ion secondary batteries, as a green, safe, and low-cost energy storage system, have attracted widespread attention. Materials such as manganese-based cathodes, vanadium-based cathodes, and Prussian blue cathodes have been developed into promising cathode materials for large-scale applications in aqueous metal-ion batteries. However, in near-neutral aqueous electrolytes, during discharge, the valence state of Mn in manganese-based cathodes can fall below +3, resulting in the Gaines-Taylor effect and the generation of Mn. 2+ Mn 2+ Dissolving into the electrolyte leads to capacity decay during long-cycle operation, and other materials exhibit similar dissolution issues. Furthermore, Mn-based cathodes have low conductivity, affecting ion diffusion, overall electrode electrochemical stability, and the energy density and rate performance of individual cells. Therefore, these cathode materials are unsuitable for thick electrodes; to produce thick electrodes, the conductive agent content must be increased to ensure stable battery cycle performance. Currently, wet processing is only suitable for producing thin electrodes with low carbon content. While dry processes developed in recent years can produce thick electrodes, no related processes have been reported for electrodes with high conductive agent content. Furthermore, most of these processes employ a one-step air jet milling process. For example, patent CN 112687833 A discloses an electrode preparation method that includes sequential dry powder stirring, pulverization and fiberization, and roll pressing and bonding. The mass ratio of the active material, conductive agent, and binder is (70-90):(5-10):(3-10). Patent CN 112420986 A uses an air jet mill and extruder-based secondary fiberization process, where the active material, conductive carbon, binder, and solid electrolyte account for 80-90%, 2-5%, 5-10%, and 1-5% of the total mixture, respectively. This makes it difficult to achieve good dispersion for electrodes with high conductive agent content, and the consistency of the prepared electrodes is also difficult to guarantee.

[0003] The above patents all involve less than 10% conductive carbon addition, and their dry processes are mostly used in lithium battery electrode manufacturing. The coatings or encapsulation layers on the surface of the active material are merely to inhibit the reaction between the active material and the electrolyte, or to improve the ion transport efficiency of the entire positive electrode. This dry process is not suitable for the preparation of positive electrodes with poor conductivity, such as manganese dioxide. Therefore, developing an electrode film that simultaneously possesses high conductive agent content and long cycle stability and is suitable for near-neutral aqueous metal-ion batteries has become an urgent problem for those skilled in the art. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing and applying a thick electrode film with a high conductive agent content. Due to the low conductivity of materials like manganese dioxide, the amount of conductive carbon added during electrode preparation is often higher than 15%, and its density is much lower than that of the active material. During the "fibrillation" process, high-speed centrifugal force causes the conductive carbon to separate from the active material, resulting in poor electrode conductivity. More importantly, the use of materials with significantly different densities increases the difficulty of preparing thick electrodes with high conductive agent content and leads to poor electrode consistency, making the production process uncontrollable. Therefore, this invention prepares a thick electrode film with high conductive agent content by wet milling and mixing conductive carbon powder and active material, followed by spray granulation and coating sintering to form micron-sized particles with uniform density. These particles are then used as the powder for fibrillation.

[0005] In a first aspect, a method for preparing a thick electrode film with a high conductive agent content is provided, comprising:

[0006] S1. A slurry of submicron to nanoscale mixture of conductive agent, active material and coating agent is obtained by wet milling;

[0007] S2. Spray drying yields micron- to millimeter-sized mixed powders with uniform density and particle size;

[0008] S3. The mixture powder described in S2 is mixed with the hydrophobic solid binder powder and heat-treated at a certain temperature to achieve the coating of the coating agent in S1 on the surface of the active material and the bonding of the binder with the powder described in S2.

[0009] S4. The powder described in S3 is subjected to high-speed air milling to fiberize the binder therein, resulting in a clump-shaped powder in the state of "marshmallow".

[0010] S5. After being hot-rolled and formed in one step, a thick electrode film with a high conductive agent content is then laminated onto the electrode current collector using conductive adhesive.

[0011] Preferably, in S1, the active material is a positive electrode active material, which includes manganese compounds, Prussian blue compounds, and vanadium compounds; the conductive agent includes one or more of Super P, acetylene black, AC, CNT, CF, graphite, or graphene; in S3, the binder includes one or more of solid PTFE, SBR, or PVDF, or a combination of at least two of them; the mass ratio of the active material, conductive agent, and binder is (70-85):(12-30):(3-10).

[0012] Preferably, in S1, the wet milling is carried out in a ball mill, colloid mill, circulating mill or sand mill, with a mixing speed of 100-700 rpm and a mixing time of 0.5-2 h.

[0013] Preferably, in S2, the concentration of the spray is 100-200℃ and the inlet pressure is 0.2-0.8MPa.

[0014] Preferably, in step S3, the mixed powder and the hydrophobic solid binder powder are mixed in a high-speed mixer for 0.5-1 hour and 300-1000 rpm.

[0015] Preferably, in S1, the coating agent accounts for 0.01%-3% of the active material, and the coating agent contains one or more elements such as nickel, cobalt, aluminum, tungsten, strontium, titanium, zirconium, niobium, antimony, boron, magnesium, zinc or copper.

[0016] Preferably, in S4, the fiberization process employs airflow pulverization, and the mixed powder undergoes heat treatment at a certain temperature; wherein, the feed airflow pressure used in the airflow pulverization process is 0.2-0.8 MPa, and the pulverizing airflow pressure is 0.1-0.7 MPa; the heat treatment temperature is 100-300℃, the time is 1-5 hours, the atmosphere is nitrogen or argon, and the high-temperature treatment equipment includes a forced-air drying oven, a rotary kiln, a roller kiln, and a tube furnace.

[0017] Preferably, in S5, the conductive adhesive is a mixture of glue and conductive carbon, wherein the conductive adhesive includes SBR, TUP, CMC, PTFE, PVDF and PVB; and the conductive carbon includes one or a combination of at least two of Super P, acetylene black, CNT, CF, KS-6, graphite or graphene.

[0018] In a second aspect, a metal-ion battery employing a near-neutral aqueous electrolyte is provided, the metal-ion battery comprising a thick electrode film with a high conductivity agent content as described in any of the first aspects.

[0019] The beneficial effects of this invention are: by wet-milling conductive carbon powder and active material, followed by spray granulation and coating sintering to prepare micron-sized particles with uniform density, and using these particles as fibrous powder, the resulting thick electrode film with high conductive agent content has higher uniformity, conductivity, and better flexibility and wettability. Attached Figure Description

[0020] Figure 1 The image shows a scanning electron microscope (SEM) image of the electrode film prepared in Example 1.

[0021] Figure 2 The image shows a scanning electron microscope (SEM) image of the electrode film prepared in Comparative Example 1.

[0022] Figure 3 The cycling curves are for the thick electrodes with high conductive agent content in Example 1 and Comparative Example 1. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0024] Existing processes for preparing thick electrode films with high conductive agent content are difficult to produce thick electrode films with high conductive agent content that have good consistency and conductivity. In order to solve the above-mentioned technical problems, this application provides a process for preparing thick electrode films with high electrode film consistency and high conductive agent content, and a method for improving the ionic and electronic conductivity of electrode films. The process and method include wet milling and mixing, spray granulation, low-temperature coating, fiberization, one-time hot rolling, and electrode film composite.

[0025] The wet milling process involves adding conductive carbon to the positive electrode powder slurry, pre-mixing it mechanically, and then using a circulating ball mill to achieve a uniform wet-milled mixture. Finally, a coating agent is added to the slurry, and mixing continues. Electron microscopy and electrochemical testing revealed that this process exhibits significantly better mixing uniformity than a one-step dry mixing method, and is simple to operate and suitable for mass production. The subsequent spray granulation process instantly dries the slurry, yielding micron-sized particles without secondary crushing, simplifying the production process and reducing costs. Low-temperature sintering in a rotary kiln results in a powder mixture with uniform size and density, effectively suppressing the release of Mn during battery charging and discharging. 2+ The coating layer dissolves and improves the cycle stability of the battery. More importantly, the mixed powder with the coating layer will not cause the separation of conductive carbon and active material due to the high-speed centrifugal force during the fiberization process. The resulting thick electrode sheet with high conductivity and toughness, high porosity, and uniform electrode film quality is suitable for mass production.

[0026] To further enhance the fibrousness of the thick electrode film with high conductivity, in some embodiments, the binder is mechanically mixed with the spray-dried mixed powder and then subjected to low-temperature sintering. For example, the holding temperature is 200–300°C, and the holding time is 3–5 hours. Limiting the temperature and holding time of the holding process within the above range is beneficial for further improving the adhesion between the active material and the coating layer. To further improve the adhesion between the coating layer and manganese dioxide, thereby improving the overall performance of the cathode material, the heating rate during the holding calcination process is 1–3°C / min, and the atmosphere is an inert gas such as nitrogen or argon.

[0027] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0028] Comparative Example 1:

[0029] Thick electrodes with high conductive agent content include:

[0030] Manganese dioxide, acetylene black, and PTFE dry powder were added to a high-speed mixer in a ratio of 7:2:1 and mixed evenly. After heating in a 70°C oven for 1 hour, the mixture was then subjected to fiberization treatment in an air jet mill. The air jet mill had a feed pressure of 0.6 MPa and a pulverizing pressure of 0.4 MPa. After heating in a 70°C oven for another hour, the mixture was formed into a marshmallow-like shape. Finally, an electrode film was pressed using a 130°C hot roller with a 300-micron slit width and laminated onto a current collector using conductive adhesive to prepare a manganese dioxide positive electrode sheet.

[0031] Negative electrode and electrolyte, including:

[0032] The negative electrode is pure zinc foil, and the electrolyte is a near-neutral 1M ZnSO4.

[0033] Example 1:

[0034] A method for preparing a thick electrode film with high conductive agent content, comprising:

[0035] Step 1: Add manganese dioxide, acetylene black, aluminum nitrate, and deionized water to the circulating mill in a ratio of 7:2:0.01:14, and mix at 500 rpm for half an hour to form a uniform slurry.

[0036] Step 2: Pass the slurry obtained in Step 1 into the spray granulation equipment and perform spray granulation at a spray temperature of 120℃ and an inlet pressure of 0.5MPa; then collect the spray granulated material.

[0037] Step 3: Place the material obtained in Step 2 in a tube furnace and heat treat it at 250°C in an inert gas atmosphere for 5 hours to obtain a mixed material of Al-coated manganese dioxide and carbon.

[0038] Step 4: Mix the mixed material obtained in Step 3 with PTFE powder at a ratio of 9:1 using a high-speed mixer. Heat the mixture in a 70°C oven for 1 hour, and then feed it into an air jet mill for fiberization. The air jet mill feed pressure is 0.6 MPa and the pulverizing pressure is 0.4 MPa to obtain the fiberized mixed powder.

[0039] Step 5: Place the mixed powder from Step 4 into a 170℃ oven and heat for 1 hour until it becomes a marshmallow-like substance; finally, use a 130℃ hot roller with a 300-micron gap width to press it into an electrode film.

[0040] Step 6: Composite the electrode film obtained in Step 5 onto the current collector using conductive adhesive to prepare a manganese dioxide positive electrode sheet.

[0041] Negative electrode and electrolyte, including:

[0042] The negative electrode is pure zinc foil, and the electrolyte is a near-neutral 1M ZnSO4.

[0043] Example 2:

[0044] The difference between this embodiment and Embodiment 1 is that in step three, the material obtained in step two is mixed with PTFE powder at a ratio of 9:1 using a high-speed mixer, and then placed in a tube furnace for heat treatment at 250°C in an inert gas atmosphere for 5 hours. Other parameters and conditions are exactly the same as in Embodiment 1.

[0045] Example 3:

[0046] The difference between this embodiment and Embodiment 1 is that the feed pressure is changed to 0.6 MPa and the crushing air pressure is 0.2 MPa, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0047] Example 4:

[0048] The difference between this embodiment and Embodiment 1 is that aluminum nitrate is replaced with zirconium nitrate, while the other parameters and conditions are exactly the same as in Embodiment 1.

Claims

1. A method for preparing a thick electrode film with high conductive agent content, characterized in that, include: S1. A slurry of submicron to nanoscale mixture of conductive agent, active material and coating agent is obtained by wet milling; S2. Spray drying yields micron- to millimeter-sized mixed powders with uniform density and particle size; S3. The mixture powder described in S2 is mixed with the hydrophobic solid binder powder and heat-treated at a certain temperature to achieve the coating of the coating agent in S1 on the surface of the active material and the bonding of the binder with the powder described in S2. S4. The powder described in S3 is subjected to high-speed air milling to fiberize the binder therein, resulting in a clump-shaped powder in the state of "marshmallow". S5. After a single hot roll forming process, a thick electrode film with a high conductive agent content is bonded to the electrode current collector using conductive adhesive; In S1, the active material is a positive electrode active material, which includes manganese compounds, Prussian blue compounds, and vanadium compounds; the conductive agent includes one or more combinations of Super P, acetylene black, AC, CNT, CF, graphite, or graphene; In S3, the binder includes one or more combinations of solid PTFE, SBR, or PVDF; the mass ratio of the active material, conductive agent, and binder is (70-85):(12-30):(3-10); In S5, the single hot roll forming temperature is 120-250℃, the gap width is 100-1000μm, and the electrode film thickness is 150-1500μm.

2. The method for preparing a thick electrode film with high conductive agent content according to claim 1, characterized in that, In S1, the wet milling is carried out in a ball mill, colloid mill, circulating mill or sand mill, with a mixing speed of 100-700 rpm and a mixing time of 0.5-2 h.

3. The method for preparing a thick electrode film with high conductive agent content according to claim 2, characterized in that, In S2, the temperature of the spray is 100-200℃, and the inlet pressure is 0.2-0.8MPa.

4. The method for preparing a thick electrode film with high conductive agent content according to claim 3, characterized in that, In S3, the mixed powder and the hydrophobic solid binder powder are mixed in a high-speed mixer for 0.5-1 h at a speed of 300-1000 rpm.

5. The method for preparing a thick electrode film with high conductive agent content according to claim 4, characterized in that, In S1, the coating agent accounts for 0.01%-3% of the active material, and the coating agent contains one or more elements such as nickel, cobalt, aluminum, tungsten, strontium, titanium, zirconium, niobium, antimony, boron, magnesium, zinc or copper.

6. The method for preparing a thick electrode film with high conductive agent content according to claim 5, characterized in that, In S4, the fiberization process employs airflow pulverization, and the mixed powder undergoes heat treatment at a certain temperature. The feed airflow pressure used in the airflow pulverization process is 0.2–0.8 MPa, and the pulverizing airflow pressure is 0.1–0.7 MPa. The heat treatment temperature is 100–300 °C, the time is 1–5 h, the atmosphere is nitrogen or argon, and the heat treatment equipment includes a forced-air drying oven, a rotary kiln, a roller kiln, and a tube furnace.

7. The method for preparing a thick electrode film with high conductive agent content according to claim 6, characterized in that, In S5, the conductive adhesive is a mixture of glue and conductive carbon. The conductive adhesive includes SBR, TUP, CMC, PTFE, PVDF and PVB; the conductive carbon includes one or a combination of at least two of Super P, acetylene black, CNT, CF, KS-6, graphite or graphene.

8. A metal-ion battery employing a near-neutral aqueous electrolyte, characterized in that, The metal-ion battery includes a thick electrode film with a high conductivity agent content prepared by any one of the methods described in claims 1-7.

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