Prussian blue-based positive electrode material and preparation method thereof, and battery

Abstract

The application discloses a Prussian blue type positive material and a preparation method and a battery thereof, and relates to the technical field of Prussian blue type positive materials. The method comprises the following steps: adding a metal salt solution into a bottom liquid through a first feeding pipe, and adding a precipitant solution into the bottom liquid through a multi-point feeding system, so that the metal salt solution and the precipitant solution react in the bottom liquid to generate the Prussian blue type positive material. The multi-point feeding system comprises a precipitant discharging pipe and a plurality of precipitant discharging ports. The precipitant discharging pipe is annularly distributed, and the plurality of precipitant discharging ports are uniformly and interval arranged on the precipitant discharging pipe. The precipitant solution is uniformly distributed to each region in the reaction space through the multi-point feeding system, so that the time aggregation of the reactants can be dispersed through spatial redistribution, and the balanced distribution of the reactants in the whole reaction space is realized. Under the premise of improving the production capacity by compressing the reaction time, the uniformity, consistency and excellent electrical performance of the Prussian blue type positive material are considered.

Description

Technical Field

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

[0002] Prussian blue cathode materials possess advantages such as high capacity, low cost, and good conductivity, and have broad application prospects in the field of electrochemical energy storage. Prussian blue cathode materials are typically synthesized using a co-precipitation method. However, due to the low solubility of its main raw material, sodium ferrocyanide, it is difficult to increase the solid content of the reaction. Therefore, the industry has long sought to develop preparation methods with higher production capacity.

[0003] Currently, common methods to improve the production capacity of Prussian blue cathode materials include shortening the reaction time and increasing the reactant concentration. Shortening the reaction time leads to a faster reaction rate, increased crystal structure defects, smaller primary particles, increased specific surface area, and decreased processing and electrochemical performance. Increasing the reactant concentration to improve single-batch, single-reactor production capacity leads to a faster reaction rate, increased particle agglomeration, and reduced synthesis uniformity. Therefore, how to improve production capacity by shortening the reaction time while simultaneously maintaining the product's uniformity, consistency, and overall electrical performance is a long-term goal in this field.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a Prussian blue-based cathode material, its preparation method, and a battery thereof.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a Prussian blue-based cathode material, comprising adding a metal salt solution to a base liquid through a first feed pipe, adding a precipitant solution to the base liquid through a multi-point feed system, and reacting the metal salt solution and the precipitant solution in the base liquid to generate a Prussian blue-based cathode material.

[0007] The multi-point feeding system includes a precipitant discharge pipe and multiple precipitant discharge ports. The precipitant discharge pipe is arranged in a ring, and the multiple precipitant discharge ports are evenly spaced on the precipitant discharge pipe.

[0008] Secondly, the present invention provides a Prussian blue-based cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0009] Thirdly, the present invention provides a battery comprising a Prussian blue cathode material as described in the foregoing embodiments.

[0010] The present invention has the following beneficial effects: This invention provides a Prussian blue cathode material, its preparation method, and a battery. By employing a multi-point feeding system, the precipitant solution is uniformly distributed to various regions in the reaction space, allowing the temporal accumulation of reactants to be dispersed through spatial redistribution, achieving a balanced distribution of the reaction zone throughout the entire reaction space. While increasing production capacity by compressing the reaction time, the uniformity and consistency of the Prussian blue cathode material are also taken into account, ensuring that the Prussian blue cathode material has excellent electrical performance. 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 schematic diagram of the reaction apparatus provided in Embodiment 1 of the present invention.

[0013] Explanation of key component symbols: 100-Reaction device; 110-Agitator; 120-First feed pipe; 130-Multi-point feed system; 131-Drive motor; 132-Flocculant discharge pipe; 133-Flocculant discharge port. Detailed Implementation

[0014] 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.

[0015] In a first aspect, the present invention provides a method for preparing a Prussian blue-based cathode material. The structure of the reaction apparatus 100 applicable to this method is described in [reference needed]. Figure 1 The specific method includes adding a metal salt solution to the bottom liquid through the first feed pipe 120, adding a precipitant solution to the bottom liquid through the multi-point feed system 130, and reacting the metal salt solution and the precipitant solution in the bottom liquid to generate a Prussian blue cathode material.

[0016] The multi-point feeding system 130 includes a precipitant discharge pipe 132 and multiple precipitant discharge ports 133. The precipitant discharge pipe 132 is arranged in a ring, and the multiple precipitant discharge ports 133 are evenly spaced on the precipitant discharge pipe 132.

[0017] By employing a multi-point feeding system 130, the precipitant solution is uniformly distributed to various spaces in the reaction system, allowing the temporal accumulation of reactants to be dispersed through spatial redistribution, thus achieving a balanced distribution of the reaction zone throughout the entire reaction space. While increasing production capacity, the uniformity and consistency of the Prussian blue cathode material are also taken into account, ensuring that the Prussian blue cathode material has excellent electrical performance.

[0018] It is understood that the reaction apparatus 100 used in the preparation method provided by the present invention is equipped with a stirring paddle 110 to ensure uniform mixing of raw materials and reaction process. The reaction apparatus 100 can be existing equipment such as a reaction tank, and the stirring paddle 110 can also be an existing device, only requiring the addition of a multi-point feeding system 130 to the existing reaction apparatus 100.

[0019] In an optional implementation, the metal salt solution and the precipitant solution are fed simultaneously to ensure the stability and uniformity of the synthesis.

[0020] By using the multi-point feeding system 130 provided by the present invention, it is possible to ensure that the raw materials are uniformly dispersed in the reaction space. Even if the present invention uses a high-concentration raw material solution and a short feeding time, there will be no problem of poor uniformity and consistency of the generated Prussian blue cathode material due to the large accumulation of precipitant solution or metal salt solution.

[0021] In an optional embodiment, the position of the precipitant outlet 133 is higher than the position of the outlet of the first feed pipe 120. That is, the precipitant outlet 133 is located on the side closer to the reaction liquid surface, while the outlet of the first feed pipe 120 is located on the side farther away from the reaction liquid surface.

[0022] By controlling the positions of the precipitant outlet 133 and the outlet of the first feed pipe 120, the metal salt solution is first stirred and dispersed at the bottom after being added to the reaction system, so that the precipitant solution added in a ring distribution reacts with the uniformly dispersed metal salt solution, ensuring that each raw material reacts uniformly in the entire reaction space, and the resulting product takes into account both increased production capacity and good electrical performance.

[0023] If the position of the precipitant outlet 133 is lower than the position of the outlet of the first feed pipe 120, or if the position of the precipitant outlet 133 and the position of the outlet of the first feed pipe 120 are at the same level, then after the precipitant solution and the metal salt solution are added to the reaction system simultaneously, they will directly contact and react before they have time to disperse. This results in a fast reaction rate, poor reaction uniformity, many defects, and deterioration of the electrochemical performance of the final product.

[0024] In an optional embodiment, the multi-point feeding system 130 further includes a drive motor 131, which drives the precipitant outlet pipe 132 to move axially along the reaction apparatus 100. This not only adjusts the position of the precipitant outlet 133 to meet the above requirements, but also continuously raises the position of the precipitant outlet 133 as the reaction progresses, to prevent the precipitant solution from accumulating at the bottom and causing uneven dispersion of the reaction raw materials. It also reduces the contact between the precipitant and high concentrations of nucleated particles.

[0025] In an optional embodiment, the metal salt solution includes a transition metal salt, a complexing agent, and a first solvent.

[0026] Transition metal salts include at least one of manganese, iron, cobalt, nickel, and copper salts.

[0027] The chelating agent includes at least one of citric acid, sodium citrate, sodium metaphosphate, and ascorbic acid.

[0028] The first solvent includes at least one of water and anhydrous ethanol.

[0029] Preferably, the concentration of the transition metal salt in the metal salt solution is 1.5 mol / L to 2.5 mol / L.

[0030] Preferably, the concentration of the complexing agent in the metal salt solution is 0.1 mol / L to 0.5 mol / L.

[0031] By adding a complexing agent to the transition metal salt solution, the transition metal salt can be complexed with the complexing agent in advance. When it is added to the bottom liquid and dispersed, it comes into contact with the precipitant solution, reducing the ion product during the reaction and generating Prussian blue-type cathode materials at a slower reaction rate.

[0032] In an optional embodiment, the precipitant solution comprises a precipitant and a second solvent.

[0033] The precipitant is sodium ferrocyanide, with a concentration of 0.5 mol / L to 1.0 mol / L.

[0034] The second solvent includes at least one of water and anhydrous ethanol.

[0035] In an optional embodiment, the base liquid includes a complexing agent, a sodium supplement, and a third solvent.

[0036] The chelating agent includes at least one of citric acid, sodium citrate, sodium metaphosphate, and ascorbic acid.

[0037] Sodium supplements include at least one of sodium chloride and sodium sulfate.

[0038] The third solvent includes at least one of water and anhydrous ethanol.

[0039] Preferably, the concentration of the complexing agent in the base solution is 0.2 mol / L to 1.0 mol / L.

[0040] Adding a small amount of complexing agent to the substrate can complex the added transition metal ions, reduce the concentration of free metal ions in the substrate, and slow down the contact reaction rate between transition metal ions and ferrocyanide ions.

[0041] In an optional embodiment, the reaction atmosphere is an inert atmosphere, the reaction temperature is 30~80℃, and the reaction time is 1~4h.

[0042] Preferably, after the reaction is complete, the reaction slurry is further filtered, washed, and dried to separate and obtain Prussian blue-based cathode materials.

[0043] Preferably, the washing includes either plate and frame washing or centrifugal washing.

[0044] Preferably, the drying process includes any one of blower drying, vacuum drying, inert atmosphere drying, or reducing atmosphere drying.

[0045] Secondly, the present invention provides a Prussian blue-based cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0046] Thirdly, the present invention provides a battery comprising a Prussian blue cathode material as described in the foregoing embodiments.

[0047] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0048] Example 1 This embodiment provides a method for preparing a Prussian blue-based cathode material, including the following steps: S01. Prepare a 0.6 mol / L sodium ferrocyanide solution using deionized water as the solvent. Prepare a 2 mol / L transition metal ion solution, wherein the molar ratio of ferrous sulfate to manganese sulfate is 1:1, and 0.2 mol / L sodium citrate is added to the metal salt solution, using deionized water as the solvent. Prepare a supporting solution with a sodium citrate concentration of 0.5 mol / L and a sodium sulfate concentration of 0.5 mol / L, using deionized water as the solvent. The molar ratio of the transition metal salt in the metal salt solution to the sodium ferrocyanide in the precipitant is 1.1:1, and the molar ratio of sodium citrate in the supporting solution to the sodium ferrocyanide in the precipitant is 1:1.

[0049] S02. Add the base liquid obtained in step S01 to the reaction apparatus 100. Please refer to [link / reference]. Figure 1 The reaction apparatus 100 is equipped with a stirring paddle 110, a first feed pipe 120 and a multi-point feed system 130.

[0050] The multi-point feeding system 130 includes a drive motor 131, a precipitant discharge pipe 132, and multiple precipitant discharge ports 133. The drive motor 131 drives the precipitant discharge pipe 132 to move along the axial direction of the reaction device 100. The precipitant discharge pipe 132 is arranged in a ring. The six precipitant discharge ports 133 are evenly spaced on the precipitant discharge pipe 132. The position of the precipitant discharge ports 133 is higher than the position of the discharge port of the first feed pipe 120.

[0051] The precipitant solution obtained in step S01 is added to the base liquid through the multi-point feeding system 130, and the metal salt solution from step S02 is added to the base liquid through the first feed pipe 120. The feeding time is 3 hours. The outlet height of the first feed pipe 120 is 1 / 2 of the initial liquid level of the base liquid. The precipitant outlet pipe 132 gradually moves upward as the reaction proceeds, maintaining a height of 1 / 3 of the liquid level of the base liquid. The reaction temperature in the reaction device 100 is controlled at 50°C, and the reaction atmosphere is nitrogen. After the feeding is completed, the mixture is stirred continuously for 30 minutes to obtain the reaction slurry.

[0052] S03. The reaction slurry obtained in step S02 is filtered, centrifuged, washed, and vacuum dried to obtain Prussian blue cathode material.

[0053] Example 2 The difference between this embodiment and Embodiment 1 is that there are three outlets on the precipitant discharge pipe.

[0054] Example 3 The difference between this embodiment and Embodiment 1 is that the precipitant discharge pipe gradually moves upward as the reaction proceeds, and the height is maintained at 1 / 2 of the distance from the bottom liquid surface; Example 4 The difference between this embodiment and Example 1 is that the concentration of sodium ferrocyanide in the precipitant solution is 0.8 mol / L.

[0055] Comparative Example 1 The difference between this embodiment and Embodiment 1 is that there is only one outlet on the precipitant discharge pipe.

[0056] Comparative Example 2 The difference between this embodiment and Embodiment 1 is that the precipitant discharge pipe does not move upward with the reaction.

[0057] Comparative Example 3 The difference between this embodiment and Embodiment 1 is that sodium citrate is not added to the metal salt solution.

[0058] Experimental Example 1 The Prussian blue cathode materials prepared by the preparation methods provided in Examples 1-4 and Comparative Examples 1-3 were subjected to performance testing, and the results are shown in Table 1.

[0059] In Table 1, particle size and particle size distribution were measured using a laser particle size analyzer. Water content was measured using a thermogravimetric analyzer. Electrical properties were measured using coin cells.

[0060] The specific method for electrical performance testing is as follows: the discharge capacity, rate and cycle are evaluated using a coin cell with sodium sheet as negative electrode. Specifically: (1) Prussian blue positive electrode material, conductive carbon black and binder PVDF are weighed in a mass ratio of 7:2:1, and NMP solvent is added and mixed evenly to obtain positive electrode slurry. The positive electrode slurry is coated on aluminum foil and dried to obtain positive electrode sheet; (2) The battery is packed in a 2032 model battery case, with sodium sheet as negative electrode and fiber separator (model WhatmanGrade GF / D) as filament. The electrolyte is 1 mol / L NaPF6 (EC:PC=1:1, 5%FEC); (3) The battery is left to stand for 12 h, the rated capacity is set to 150 mA / g to determine the current density, the capacity is tested by setting a 0.1 C charge and discharge program, the rate is tested by setting a 10 C charge and discharge program, and the cycle is tested by setting a 2 C charge and discharge program. The voltage range is 2.0 V-4.0 V.

[0061] Table 1 Performance of Prussian blue-based cathode materials

[0062] As shown in Table 1, the Prussian blue cathode material prepared by the method provided in this embodiment of the invention has uniform particle size, low water content, high specific capacity, and good cycle performance. Furthermore, this preparation method does not require the introduction of large-scale reaction equipment; only modifications to the feed pipeline of the precipitant solution are needed, making it suitable for large-scale industrial production.

[0063] Compared to Example 1, Comparative Example 1 has only one precipitant outlet. After the precipitant is added to the bottom liquid, the concentration in the reaction zone is high, resulting in an excessively fast reaction rate, small particle size, many vacancy defects, high water content, and deterioration of specific capacity and circulation performance.

[0064] Compared to Example 1, in Comparative Example 2, the precipitant discharge pipe does not move upward with the reaction. After the precipitant is added to the bottom liquid, the concentration of reactants near the discharge port is high, the number of particles is large, which leads to fast nucleation and growth rates, many vacancy defects, high water content, and deterioration of specific capacity and circulation performance.

[0065] Compared to Example 1, Comparative Example 3 did not add sodium citrate to the metal salt solution. After the metal salt was added to the bottom solution, the concentration of free metal ions in the diffusion zone was high, the reaction rate was fast, resulting in fast nucleation and growth rates, more vacancy defects, high water content, and deterioration of specific capacity and cycling performance.

[0066] The Prussian blue-based cathode material, its preparation method, and the battery provided in this invention have at least the following advantages: The present invention designs a multi-point feeding system 130 to expand the distribution of raw materials added to the reaction device 100 from a single point to a spatial multi-point distribution, so that the accumulation of reaction raw materials in time can be dispersed by spatial redistribution, thereby achieving a balanced distribution of reaction raw materials throughout the reaction space.

[0067] This effectively balances the contradiction between shortening the reaction time and improving the reaction uniformity. The resulting Prussian blue cathode material products have good consistency and uniformity, low water content, high specific capacity, and good cycle performance. This method can take into account both increased production capacity and the good electrical performance of Prussian blue cathode material products.

[0068] This invention adds a complexing agent to the metal salt solution, so that the newly added transition metal ions are first fully dispersed in the base solution to a low concentration, and then react with the added ferrocyanide ions, thereby reducing the ion product during the reaction and avoiding direct reaction between the newly added precipitant solution and the high concentration of transition metal ions.

[0069] This invention controls the outlet positions of the first feed pipe 120 and the precipitant outlet pipe 132, so that the added precipitant reacts with uniformly dispersed transition metal ions, rather than reacting directly with newly added high-concentration transition metal ions, thereby achieving the goal of high-speed synthesis of uniform Prussian blue cathode materials.

[0070] The above description is merely a preferred embodiment of the present invention and is 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 method for preparing a Prussian blue-based cathode material, characterized in that, The process includes adding a metal salt solution to the bottom liquid through a first feed pipe, adding a precipitant solution to the bottom liquid through a multi-point feed system, and the metal salt solution and the precipitant solution reacting in the bottom liquid to generate a Prussian blue-type cathode material. The multi-point feeding system includes a precipitant discharge pipe and multiple precipitant discharge ports. The precipitant discharge pipe is arranged in a ring, and the multiple precipitant discharge ports are evenly spaced on the precipitant discharge pipe.

2. The preparation method according to claim 1, characterized in that, The metal salt solution and the precipitant solution are added simultaneously.

3. The preparation method according to claim 1, characterized in that, The position of the precipitant outlet is higher than the position of the outlet of the first feed pipe.

4. The preparation method according to claim 1 or 3, characterized in that, The multi-point feeding system also includes a drive motor, which drives the precipitant discharge pipe to move axially along the reaction device.

5. The preparation method according to claim 1, characterized in that, The metal salt solution comprises a transition metal salt, a complexing agent, and a first solvent; The transition metal salt includes at least one of manganese salt, iron salt, cobalt salt, nickel salt, and copper salt; The complexing agent includes at least one of citric acid, sodium citrate, sodium metaphosphate, and ascorbic acid; The first solvent includes at least one of water and anhydrous ethanol; Preferably, the concentration of the transition metal salt in the metal salt solution is 1.5 mol / L to 2.5 mol / L; Preferably, the concentration of the complexing agent in the metal salt solution is 0.1 mol / L to 0.5 mol / L.

6. The preparation method according to claim 1, characterized in that, The precipitant solution includes a precipitant and a second solvent; The precipitant is sodium ferrocyanide, and the concentration of sodium ferrocyanide is 0.5 mol / L to 1.0 mol / L; The second solvent includes at least one of water and anhydrous ethanol.

7. The preparation method according to claim 1, characterized in that, The base liquid includes a complexing agent, a sodium supplement, and a third solvent; The complexing agent includes at least one of citric acid, sodium citrate, sodium metaphosphate, and ascorbic acid; The sodium supplement includes at least one of sodium chloride and sodium sulfate; The third solvent includes at least one of water and anhydrous ethanol; Preferably, the concentration of the complexing agent in the base solution is 0.2 mol / L to 1.0 mol / L.

8. The preparation method according to claim 1, characterized in that, The reaction atmosphere is inert, the reaction temperature is 30~80℃, and the reaction time is 1~4h; Preferably, after the reaction is completed, the reaction slurry is further filtered, washed and dried to separate and obtain Prussian blue-based cathode materials; Preferably, the washing includes either plate and frame washing or centrifugal washing; Preferably, the drying includes any one of blower drying, vacuum drying, inert atmosphere drying, or reducing atmosphere drying.

9. A Prussian blue-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that, Including the Prussian blue-type cathode material as described in claim 9.

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