Prussian blue composite positive electrode material and preparation method and application thereof

Abstract

The invention discloses a Prussian blue type composite positive electrode material and a preparation method and application thereof, and the Prussian blue type composite positive electrode material provided by the invention is composite powder containing a Prussian blue type positive electrode material, a conductive agent, a binder and a functional additive, the mass ratio of the Prussian blue positive electrode material to the conductive agent to the binder to the functional additive is (90-99): (1-5): (0-5): (0-0.5). According to the Prussian blue composite positive electrode material provided by the invention, the components are uniformly distributed, the Prussian blue composite positive electrode material has the characteristics of high compaction, easy dispersion, relapse resistance, high conductivity and the like, and the Prussian blue composite positive electrode material can be directly used for wet homogenization and can also be directly used for dry electrode manufacturing.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a Prussian blue-based composite cathode material, its preparation method, and its application. Background Technology

[0002] Prussian blue cathode materials (PBLs) possess advantages such as high capacity, low cost, and good conductivity, making them promising candidates for electrochemical energy storage. However, the contact between PBLs and conductive agents is affected by their morphology; smaller particles are difficult to mix uniformly, while larger particles, typically cubic in shape, result in insufficient contact with the conductive agent. PBLs also readily reabsorb moisture after dehydration, making particle dispersion difficult and increasing slurry viscosity during homogenization. Mechanical stirring methods used in battery cell preparation cannot ensure uniform distribution and effective contact between PBLs particles and conductive agents, binders, and additives. Currently, to improve the application characteristics of PBLs, two approaches have been taken: surface modification, including improving conductivity and resistance to reabsorption; and changing the application state, including using raw materials containing water of crystallization and applying them in slurry form. However, these modification methods have limited impact on the performance improvement of Prussian blue cathode materials. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a Prussian blue-based composite cathode material, its preparation method, and its application.

[0004] The technical problem solved by this invention is achieved by the following technical solution.

[0005] This invention provides a Prussian blue composite cathode material, which is a composite powder comprising a Prussian blue cathode material, a conductive agent, a binder, and a functional additive, wherein the mass ratio of the Prussian blue cathode material, the conductive agent, the binder, and the functional additive is (90-99):(1-5):(0-5):(0-0.5).

[0006] The present invention also provides a method for preparing the above-mentioned Prussian blue composite cathode material, comprising: mixing the washing material, conductive agent, binder and functional additive of the Prussian blue cathode material into a slurry, and then ball milling and drying to obtain the Prussian blue composite cathode material.

[0007] The present invention also provides a positive electrode sheet, which includes a positive current collector and a positive active material layer disposed on the positive current collector; the positive active material layer includes the above-mentioned Prussian blue composite positive electrode material; and the positive electrode sheet can be prepared by a dry preparation process or a wet preparation process.

[0008] The present invention also provides a battery comprising a positive electrode, wherein the positive electrode is the aforementioned positive electrode.

[0009] The present invention has the following beneficial effects:

[0010] This invention provides a Prussian blue-based composite cathode material, its preparation method, and its applications. The Prussian blue-based composite cathode material provided by this invention is a composite powder comprising a Prussian blue-based cathode material, a conductive agent, a binder, and functional additives, with a mass ratio of (90-99):(1-5):(0-5):(0-0.5). The Prussian blue-based composite cathode material provided by this invention exhibits uniform distribution of its components. Under the action of the binder, the Prussian blue-based cathode material and the conductive agent are in close contact, enhancing the material's conductivity, reducing the internal resistance of the electrode, and effectively increasing the peel force between the powder and the electrode. The functional additives improve the dispersibility and viscosity of the composite powder, thereby giving the Prussian blue-based composite cathode material provided by this invention characteristics such as high tapping speed, easy dispersibility, and high conductivity. In addition, the aforementioned Prussian blue composite cathode materials have a wide range of applications. When used in wet electrode processes, they can improve the efficiency of the homogenization process, and when used in dry electrode processes, they can improve the mixing uniformity with other materials. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a SEM image of the Prussian blue composite cathode material prepared in Example 1 of the present invention. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0014] The following is a detailed description of a Prussian blue-based composite cathode material, its preparation method, and its application, provided by embodiments of the present invention.

[0015] In a first aspect, embodiments of the present invention provide a Prussian blue composite cathode material, which is a composite powder comprising a Prussian blue cathode material, a conductive agent, a binder and a functional additive, wherein the mass ratio of the Prussian blue cathode material, the conductive agent, the binder and the functional additive is (90-99):(1-5):(0-5):(0-0.5).

[0016] This invention provides a Prussian blue-based composite cathode material, which is a composite powder comprising a Prussian blue-based cathode material, a conductive agent, a binder, and functional additives. The conductive agent enhances the material's conductivity and reduces the internal resistance of the electrode; the binder effectively increases the peel force between the composite powder and the electrode; and the functional additives improve the dispersibility and water resistance of the composite powder. Compared to slurries containing Prussian blue-based cathode materials, the Prussian blue-based composite cathode material provided in this invention is a composite powder. The components in the composite powder are uniformly distributed and tightly bound, exhibiting good flowability, anti-reabsorption, high tapping strength, and good conductivity. The composition of the Prussian blue-based cathode material is not limited. Furthermore, through the scientific proportioning of the components, a Prussian blue-based composite cathode material with good stability is obtained.

[0017] In some alternative embodiments, the composite powder is a composite particle comprising a uniformly mixed Prussian blue-based cathode material, a conductive agent, a binder, and functional additives.

[0018] Preferably, the composite particles are spherical with a particle size of 2μm-30μm and a water content of 5%-15%.

[0019] The Prussian blue-based composite cathode material provided in this invention is a composite powder comprising a Prussian blue-based cathode material, a conductive agent, a binder, and functional additives. The composite powder consists of multiple component particles. The spherical secondary particles facilitate close contact between the Prussian blue-based cathode material and the conductive agent, reducing the internal resistance of the electrode. The spherical morphology also helps to increase the material's tap density, improve storage and transport characteristics, and accelerate dispersion during homogenization. Furthermore, the spherical morphology and high flowability of the composite particles accelerate moisture removal, achieving further deep dehydration of the composite powder, thereby improving the thermal stability and crystallinity of the Prussian blue-based composite cathode material, ensuring the material's purity and performance.

[0020] In some alternative embodiments, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, and graphene.

[0021] In some alternative embodiments, the adhesive is a water-based composite adhesive, including at least one of PTFE (polytetrafluoroethylene), PAA (polyacrylic acid), CMC (sodium carboxymethyl cellulose), PEO (polyethylene oxide), PVA (polyvinyl alcohol), and PMA (polymethacrylic acid).

[0022] In some alternative embodiments, the functional additive is at least one of compounds that enhance dispersion and water-repellent effects. The compounds that enhance dispersion include surfactants such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), sodium polyacrylate (ASAP), etc., and the compounds that repel water include polyacrylic acid analogs such as polyacrylic acid (PAA), etc.

[0023] Prussian blue-based cathode materials are prone to reabsorbing moisture after dehydration, making particle dispersion difficult and increasing slurry viscosity during homogenization. To address these issues, the present invention provides a solution that incorporates functional additives into the Prussian blue-based composite cathode material. These additives can achieve the following effects: slow down the reabsorption of moisture by the composite powder during storage and processing, and improve the flowability of the slurry and the uniformity of dispersion of each material during the preparation process.

[0024] Secondly, embodiments of the present invention also provide a method for preparing the above-mentioned Prussian blue composite cathode material, comprising: mixing the washing material, conductive agent, binder and functional additives of the Prussian blue cathode material into a slurry, and then ball milling and drying to obtain the Prussian blue composite cathode material.

[0025] This invention also provides a method for preparing the above-mentioned Prussian blue composite cathode material. The method involves mixing the washing material of the Prussian blue cathode material with a conductive agent, binder, and functional additives to form a slurry. The resulting slurry is then ball-milled. Ball milling alters the morphology of the Prussian blue cathode material, facilitating sufficient contact between it and the conductive agent. This overcomes the shortcomings of traditional slurry preparation methods that use mechanical stirring, which struggle to ensure uniform distribution and effective contact between the Prussian blue cathode material particles and the conductive agent, binder, and functional additives. The powder is then dried using a spray drying method to obtain a composite powder with good flowability, high tapping density, and uniform distribution of all components. The preparation method provided by this invention is simple, efficient, and produces a uniformly dispersed and tightly contacted conductive agent and Prussian blue cathode material. The prepared Prussian blue composite cathode material exhibits high tapping density, easy dispersibility, anti-reabsorption properties, and high conductivity. Furthermore, the composition of the Prussian blue cathode material is not limited.

[0026] In some alternative implementations, the following steps are included:

[0027] The washing material, conductive agent, binder and functional additives of the Prussian blue cathode material obtained by precipitation reaction are placed in an aqueous solvent and mixed evenly to obtain a mixed slurry.

[0028] The mixed slurry is ball-milled and dispersed evenly, and the particle size is controlled to obtain a dispersed slurry;

[0029] Under an inert atmosphere, the dispersed slurry is spray-dried to obtain a Prussian blue-based composite cathode material.

[0030] The preparation method of the Prussian blue composite cathode material provided in this invention includes the following steps: First, the washing material of the Prussian blue cathode material obtained by precipitation reaction is dispersed in a dispersion system along with a conductive agent, a binder, and functional additives. The washing material used in this step is the material obtained by washing the slurry of the Prussian blue cathode material prepared by co-precipitation. Compared with dry powder, using the washing material directly eliminates the need for further crushing and drying, saving energy and making it easier to disperse in the dispersion system, resulting in higher dispersion uniformity and stability. Then, the prepared mixed slurry is ball-milled. Ball milling not only promotes the uniformity of mixing of the components in the system, but more importantly, it can minimize the sharp edges and corners of the cubic particles of the Prussian blue cathode material, forming a more rounded and regular structure, ensuring uniform particle size, no irregularities, and no large particles. This is beneficial for the Prussian blue cathode material and the conductive agent to form a closer contact in the Prussian blue composite cathode material. Finally, the dispersion slurry is dried, preferably by spray drying, to obtain a composite powder with good flowability, high tapping density, and uniform distribution of components. Furthermore, this composite powder can be further dehydrated, improving the stability and crystallinity of the Prussian blue composite cathode material. Therefore, the composite powder prepared using the method provided in this invention can be directly used for wet homogenization, simplifying the feeding process and improving slurry dispersibility and flowability; it can also be used for dry electrode manufacturing, as its high flowability facilitates uniform mixing with other materials, improving electrode consistency.

[0031] In some alternative embodiments, the solids content of the mixed slurry is 15%-40%.

[0032] In some alternative embodiments, the inlet air temperature of the spray dryer is in the range of 150°C-250°C, preferably 180-230°C, and the outlet air temperature is in the range of 80°C-130°C.

[0033] Thirdly, embodiments of the present invention also provide a positive electrode sheet, which includes a positive current collector and a positive active material layer disposed on the positive current collector; the positive active material layer includes the above-mentioned Prussian blue composite positive electrode material, and the positive electrode sheet can be prepared by a dry preparation process or a wet preparation process.

[0034] This invention also provides a positive electrode sheet, which includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive active material layer includes the aforementioned Prussian blue composite positive electrode material. Based on the characteristics of the synthesized Prussian blue composite positive electrode material, such as high tapping, easy dispersion, anti-reabsorption, and high conductivity, its use in wet electrode processes can improve the efficiency of the homogenization process, and its use in dry electrode processes can improve the mixing uniformity with other materials. Therefore, the positive electrode sheet can be prepared by wet or dry preparation processes. For example, the wet preparation process can be: mixing the Prussian blue composite positive electrode material, solvent, and binder into a homogenate, and then coating the slurry onto the surface of the positive current collector to prepare the positive electrode sheet. The dry preparation process can be: mixing the Prussian blue composite positive electrode material and binder, laying them on the surface of the positive current collector, and then rolling to prepare the positive electrode sheet.

[0035] Fourthly, embodiments of the present invention also provide a battery, the battery including a positive electrode sheet, wherein the positive electrode sheet is the aforementioned positive electrode sheet.

[0036] The present invention will be further described below with reference to embodiments.

[0037] Example 1

[0038] A method for preparing a Prussian blue-based composite cathode material includes the following steps:

[0039] S1, the Prussian blue cathode material washing material (water content 25%, this part of water is deducted when weighing the ingredients) obtained by precipitation reaction, conductive carbon SP, binder PAA and surfactant PEG are weighed in a mass ratio of 95:3.0:1.5:0.5, and mixed evenly in an aqueous solvent to obtain a mixed slurry with a solid content of 20%.

[0040] S2, the mixed slurry is ball-milled and dispersed evenly and the particle size is controlled to obtain a dispersed slurry;

[0041] S3. The dispersed slurry is spray-dried under an inert atmosphere. The inlet air temperature is 200℃ and the outlet air temperature is 100℃ to obtain a composite powder. The composite powder contains spherical particles with a particle size of 15μm and a water content of 10%. See the SEM image of the composite powder. Figure 1 As can be seen, the particles have good dispersibility and high uniformity in particle size.

[0042] Electrode preparation: Using NMP as the dispersion solvent, the composite powder and binder PVDF were directly homogenized at a mass ratio of 97:3, with a solid content of 45%. Transfer coating was used, and the surface density of the double-sided coating was controlled at 200 g / m². 2 .

[0043] Example 2

[0044] The steps are basically the same as in Example 1, except that the adhesive PAA is not added in step S1.

[0045] Example 3

[0046] The steps are basically the same as in Example 1, except that the surfactant PEG is not added in step S1.

[0047] Example 4

[0048] The steps are basically the same as in Example 1, except that the inlet air temperature for spray drying in step S3 is 250°C.

[0049] Example 5

[0050] The steps are basically the same as in Example 1, except that the composite powder prepared in Example 1 is used for dry electrode preparation: the composite powder of Prussian blue cathode material and the binder PTFE are dry mixed and formed in a mass ratio of 97:3.

[0051] Comparative Example 1

[0052] The steps are basically the same as in Example 1, except that conductive carbon SP is not added in step S1, but is added in the electrode preparation homogenization section instead.

[0053] Comparative Example 2

[0054] A method for preparing Prussian blue-based cathode material dry powder involves drying the Prussian blue-based cathode material washing material obtained by precipitation reaction to a dry powder with a water content of 10%.

[0055] Using NMP as the dispersion solvent, a slurry was directly prepared with the dry powder of the Prussian blue-based cathode material, conductive carbon SP, and binder PVDF at a mass ratio of 92:3.5:4.5, resulting in a solid content of 45%. A transfer coating method was employed, with the surface density of the double-sided coating controlled at 200 g / m². 2 .

[0056] Comparative Example 3

[0057] A method for preparing Prussian blue-based cathode material dry powder involves drying Prussian blue detergent obtained by precipitation reaction to a dry powder with a water content of 10%.

[0058] Prussian blue dry powder was used for dry electrode preparation. The dry powder of Prussian blue cathode material, conductive carbon SP and binder PTFE were dry mixed and formed into sheets at a mass ratio of 92:3.5:4.5.

[0059] Performance evaluation

[0060] The preparation method of the soft-pack battery is as follows: The DC resistance (DCR) is evaluated using a soft-pack battery with hard carbon as the negative electrode. Specifically: (1) The electrode sheets prepared in the examples and comparative examples are used as positive electrode sheets; (2) Hard carbon is used to prepare the negative electrode sheet. The hard carbon: conductive carbon: SBR: CMC: PAA are homogenized in a mass ratio of 92:4:2:1:1 with a solid content of 45%. The coating is applied by transfer method, and the surface density of the double-sided coating is controlled to be 100 g / m². 2 (3) The battery resting time is 12h, the rated capacity is set to 150mA / g to determine the current density, and the voltage range is 2.0V-4.0V.

[0061] The viscosity of the slurry, the electrode peeling force (180° peeling method), and the DC internal resistance (DCR) of the assembled soft-pack battery cells were tested after homogenization for Examples 1 to 5 and Comparative Examples 1 to 3. The measured data are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] As can be seen from Table 1 above: Examples 1-5, using composite powder of Prussian blue cathode material for homogenization, showed significantly lower slurry viscosity than the slurry homogenized with dry Prussian blue cathode material in Comparative Example 2. Furthermore, the DC internal resistance of the pouch cell prepared using composite powder of Prussian blue cathode material in Examples 1-5 was significantly lower than the DC internal resistance of the electrode sheets prepared using dry Prussian blue cathode material in Comparative Examples 2 and 3. These comparisons demonstrate that the flowability of the composite powder of Prussian blue cathode material prepared in the embodiments of this invention is superior to that of dry Prussian blue cathode material, and the contact effect between the pre-mixed conductive carbon and the Prussian blue cathode material is superior to the contact effect between the dry Prussian blue cathode material and conductive carbon added during wet homogenization.

[0066] Compared with Example 1 and Example 2, the introduction of a binder into the composite powder of Prussian blue cathode material is beneficial to improving the peel strength of the electrode sheet. Compared with Example 3, the introduction of a surfactant into the composite powder of Prussian blue cathode material is beneficial to improving the flowability of the composite powder during homogenization. Compared with Example 1, the drying temperature of the composite powder of Prussian blue cathode material during preparation was too high, which was not conducive to the function of the binder. The results of Example 5 show that the composite powder can be used for dry electrode preparation, and compared with Comparative Example 3, it has higher peel strength and lower DC internal resistance of the soft-pack cell. This is attributed to the better mixing effect of the composite powder of Prussian blue cathode material with the conductive agent and binder.

[0067] Therefore, the composite powder of Prussian blue cathode material provided by the present invention improves the contact between Prussian blue cathode material and conductive agent and binder. Its spherical morphology during homogenization is conducive to the uniform mixing effect with other materials and improves the fluidity of the slurry. As a result, the electrode sheet produced has greater peel strength and lower DC internal resistance of the cell.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Prussian blue-based composite cathode material, characterized in that, It is a composite powder containing Prussian blue-based cathode material, conductive agent, binder and functional additive, and the mass ratio of the Prussian blue-based cathode material, the conductive agent, the binder and the functional additive is (90-99):(1-5):(0-5):(0-0.5).

2. The Prussian blue-based composite cathode material according to claim 1, characterized in that, The composite powder is a composite particle containing a uniformly mixed Prussian blue-based cathode material, a conductive agent, a binder, and functional additives. Preferably, the composite particles are spherical with a particle size of 2μm-30μm and a water content of 5%-15%.

3. The Prussian blue-based composite cathode material according to claim 1 or 2, characterized in that, The conductive agent includes at least one of conductive carbon black, carbon nanotubes, and graphene.

4. The Prussian blue-based composite cathode material according to claim 1 or 2, characterized in that, The adhesive is a water-based composite adhesive, including at least one of PTFE (polytetrafluoroethylene), PAA (polyacrylic acid), CMC (sodium carboxymethyl cellulose), PEO (polyethylene oxide), PVA (polyvinyl alcohol), and PMA (polymethacrylic acid).

5. The Prussian blue composite cathode material according to claim 1 or 2, characterized in that, The functional additives include at least one of polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), sodium polyacrylate (ASAP), and polyacrylic acid (PAA).

6. A method for preparing a Prussian blue-based composite cathode material according to any one of claims 1-5, characterized in that, include: The Prussian blue-based cathode material is prepared by mixing the washing material, conductive agent, binder and functional additives, then ball milling and drying to obtain the Prussian blue-based composite cathode material.

7. The preparation method according to claim 6, characterized in that, Includes the following steps: The washing material, conductive agent, binder and functional additives of the Prussian blue cathode material obtained by precipitation reaction are placed in an aqueous solvent and mixed evenly to obtain a mixed slurry. The mixed slurry is ball-milled and dispersed evenly, and the particle size is adjusted to obtain a dispersed slurry; Under an inert atmosphere, the dispersion slurry is spray-dried to obtain the Prussian blue composite cathode material.

8. The preparation method according to claim 7, characterized in that, The solid content of the mixed slurry is 15%-40%, the inlet air temperature of the spray dryer is in the range of 150℃-250℃, and the outlet air temperature is in the range of 80℃-130℃.

9. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive active material layer disposed on the positive current collector; the positive active material layer includes the Prussian blue composite positive electrode material as described in any one of claims 1 to 5; the positive electrode sheet can be prepared by a dry preparation process or a wet preparation process.

10. A battery, the battery comprising a positive electrode, characterized in that, The positive electrode sheet is the positive electrode sheet described in claim 9.

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