Preparation method of high-performance manganese-based Prussian blue

Abstract

A preparation method of high-performance manganese-based Prussian blue comprises the following steps: step 1, dissolving sodium ferrocyanide in deionized water to obtain a solution A; different types of transition metal salts and a complexing agent are dissolved in deionized water, and different types of solutions B are obtained; 2, deionized water is added into a reaction kettle, different kinds of solutions B and the solution A are added into the reaction kettle step by step at the same speed or different speeds, after the step-by-step feeding reaction is completed, stirring is conducted to obtain turbid liquid, the turbid liquid is centrifuged, precipitates are washed and dried, and the high-performance manganese-based Prussian blue material is obtained. Wherein the transition metal ions in the solution B fed in the first step are not manganese ions independently, and the transition metal ions in the solution B fed in the second step are manganese ions. The particle size of the manganese-based Prussian blue positive electrode material can be effectively reduced, the cycle performance is remarkably improved, and the problems of poor cycle performance and the like caused by factors such as large particle size and unstable crystal lattices in the cycle process of manganese-based Prussian blue are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy batteries, relates to the field of sodium ion batteries, and specifically relates to a method for preparing high-performance manganese-based Prussian blue. Background Art

[0002] Lithium-ion batteries are widely used in various portable devices and electric vehicles due to their long service life, stable cycle performance, and high power density. However, the global lithium resource reserves are small and extremely unevenly distributed, which is easily affected by geopolitics and has large price fluctuations, which will hinder the application of lithium-ion batteries in large-scale energy storage in the future.

[0003] Sodium-ion batteries are favored among many alternative electrochemical energy storage battery alternatives because of their uniform distribution of sodium resources, abundant reserves, and low cost. Sodium and lithium are in the same main group and have similar physical and chemical properties. Among the key materials of sodium-ion batteries, positive electrode materials are one of the main factors that determine battery performance and cost, and account for the largest proportion of raw material costs, exceeding 30%. From the perspective of technical route development, based on the differentiation of positive electrode materials, the current mainstream sodium positive electrode materials have developed into three major technical routes: layered oxides, polyanionic compounds, and Prussian blue compounds. Prussian blue compounds have great potential in the future because of their good structural stability and rate performance, low cost, high specific capacity and energy density, etc.

[0004] Common Prussian blue sodium-ion battery cathode materials mainly include iron-based Prussian blue and manganese-based Prussian blue. Compared with iron-based Prussian blue, manganese-based Prussian blue has a higher discharge potential, which can achieve higher energy density. However, due to key problems such as the large number of vacancy defects and high crystal water content, the manganese-based Prussian blue synthesized by the traditional coprecipitation method still faces major challenges in being used as a cathode material for sodium-ion batteries. Studies have shown that for manganese-based Prussian blue materials, reducing the reaction rate or increasing the reaction temperature can effectively reduce vacancy defects and crystal water content. However, early complexation with cations through complexing agents can reduce the reaction rate, but it will cause the particle size of manganese-based Prussian blue to become abnormally large, which is not only not conducive to the diffusion of sodium ions, but also increases the difficulty of dehydration of crystal water. The grains are severely broken during the cycle, which leads to worse cycle performance. Therefore, while improving the crystallinity of manganese-based Prussian blue, it can effectively control the particle size, thereby improving the cycle performance, which has become a key problem that needs to be solved for manganese-based Prussian blue. Summary of the invention

[0005] The present invention provides a method for preparing high-performance Prussian blue. Under the premise of reducing the reaction rate, a multi-step feeding method is used to introduce ions different from the base material to achieve particle size control of the manganese-based Prussian blue material, while achieving the effects of doping and reducing defects, thereby improving its cycle performance. By changing the feeding rate, feeding amount or metal ion type of the first step of feeding, the particle size of the manganese-based Prussian blue can be effectively regulated, and the element doping ratio can be changed at the same time.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing high-performance manganese-based Prussian blue comprises the following steps:

[0008] Step 1, dissolving sodium ferrocyanide in deionized water to obtain solution A; dissolving different types of transition metal salts and complexing agents in deionized water to obtain different types of solutions B;

[0009] Step 2: Add deionized water to the reactor, add different types of solution B and solution A to the reactor at a certain rate, stir for 12 hours after the step-by-step feeding reaction is completed, obtain a suspension, centrifuge the suspension, wash the precipitate with a washing solvent for 3-5 times, and put the collected material into a vacuum oven at 80-150° C. and dry for 8 hours to obtain a high-performance manganese-based Prussian blue material; wherein the transition metal ion in the first step feeding solution B is not selected as manganese ion alone, and the transition metal ion in the second step feeding solution B is manganese ion. In the present invention, the multi-step feeding method is divided into at least two steps of feeding.

[0010] Furthermore, if there are more than two feeding steps, in the subsequent feeding step, the transition metal salt does not limit the type of transition metal ions, and Mn 2+ 、Ni 2+ , Fe 2+ 、Co 2+ , Cu 2+ 、Zn 2+ A combination of one or more of .

[0011] Further, the transition metal ions in the first step of step 2, the feeding solution B, include Ni 2+ , Fe 2+ 、Co 2+ , Cu 2+ 、Zn 2+ One of the 2+ 、Ni 2+ , Fe 2+ 、Co 2+ , Cu 2+ 、Zn 2+ A combination of at least two of .

[0012] Furthermore, the transition metal ions in the first step of step 2, the feed solution B, include Mn 2+ When Mn 2+ The content does not exceed 30% of the total amount of transition metal ions in the first step feeding solution B.

[0013] Furthermore, the total amount of solution A and solution B fed in the first step is 1%-10% of the total amount of solution A and solution B fed.

[0014] Furthermore, the concentrations of solution A and different types of solution B are both 0.01-0.6 mol / L.

[0015] Furthermore, in different feeding steps, the feeding speeds of solution A and solution B are the same, the feeding speed ratio between different steps is 0.5-10, and the stirring speeds in different feeding steps are the same.

[0016] Furthermore, the temperature in the reactor is 10-80°C, and the stirring speed is 50-700r / min.

[0017] Furthermore, the complexing agent includes one or a combination of sodium pyrophosphate, sodium citrate, citric acid, and EDTA-disodium.

[0018] Furthermore, transition metal salts of different ions are independently selected from a combination of one or more of sulfates, acetates, nitrates, and chlorides.

[0019] Furthermore, an inert gas is introduced into the reactor as a protective atmosphere, and the inert gas includes a combination of one or more of argon and nitrogen.

[0020] Furthermore, the washing solvent includes a combination of one or more of deionized water, anhydrous ethanol and acetone.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for preparing high-performance Prussian blue, which can effectively reduce the particle size of manganese-based Prussian blue positive electrode materials and significantly improve the cycle performance. By changing the feeding rate and the ratio of the step-by-step feeding amount, as well as the type of metal ions, etc. in a multi-step feeding method, the doping effect can be effectively achieved while reducing the particle size, thereby solving the problems of poor cycle performance of manganese-based Prussian blue due to factors such as large particle size and lattice instability during the cycle process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a graph of capacity retention rates of comparative examples and embodiments of the present invention;

[0024] Figure 2 It is a graph of gram capacity of comparative examples and embodiments of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] Embodiment 1:

[0027] A method for preparing high-performance manganese-based Prussian blue comprises the following steps:

[0028] Step 1: Dissolve 120 g of sodium ferrocyanide in deionized water to prepare 630 mL of sodium ferrocyanide solution, referred to as solution A;

[0029] Step 2: Dissolve 3 g zinc sulfate, 0.5 g manganese sulfate, and 10 g sodium citrate in deionized water to prepare 30 mL of a mixed solution, referred to as solution B1;

[0030] Step 3: Dissolve 40 g of manganese sulfate and 190 g of sodium citrate in deionized water to prepare 600 mL of a mixed solution, which is referred to as solution B2;

[0031] Step 4: Add 300 mL of deionized water into the reactor, and simultaneously add solution A and solution B1 into the reactor at a rate of 2 mL / min. After the addition is complete, simultaneously add the remaining solution A and solution B2 into the reactor at a rate of 10 mL / min.

[0032] Step 5: Stir for 12 hours (rotation speed is 700 rpm), wash the suspension three times with deionized water by centrifugation, and bake it in a vacuum drying oven at 120°C for 8 hours to obtain a high-performance manganese-based Prussian blue positive electrode material.

[0033] Embodiment 2:

[0034] A method for preparing high-performance manganese-based Prussian blue comprises the following steps:

[0035] Step 1: Dissolve 120 g of sodium ferrocyanide in deionized water to prepare 660 mL of sodium ferrocyanide solution, referred to as solution A;

[0036] Step 2: Dissolve 3 g zinc sulfate and 10 g sodium citrate in deionized water to prepare 30 mL of a mixed solution, referred to as solution B1;

[0037] Step 3: Dissolve 40 g of manganese sulfate and 190 g of sodium citrate in deionized water to prepare 600 mL of a mixed solution, which is referred to as solution B2;

[0038] Step 4: Dissolve 3 g of ferrous sulfate, 0.5 g of manganese sulfate, and 10 g of sodium citrate in deionized water to prepare 30 mL of a mixed solution, which is referred to as solution B3;

[0039] Step 5: Add 300 mL of deionized water to the reactor, and simultaneously add solution A and solution B1 to the reactor at a rate of 2 mL / min. After the addition is complete, add solution A and solution B2 to the reactor at a rate of 10 mL / min. After the addition is complete, add the remaining solution A and solution B3 to the reactor at a rate of 2 mL / min.

[0040] Step 6: Stir for 12 hours (rotation speed is 700 rpm) to obtain a suspension, wash the suspension three times with deionized water by centrifugation, and place it in a vacuum drying oven at 120° C. for 8 hours to obtain a high-performance manganese-based Prussian blue positive electrode material.

[0041] Comparative Example 1:

[0042] A method for preparing manganese-based Prussian blue comprises the following steps:

[0043] Step 1: Dissolve 120 g of sodium ferrocyanide in deionized water to prepare 600 mL of sodium ferrocyanide solution, referred to as solution A;

[0044] Step 2: Dissolve 40 g of manganese sulfate and 190 g of sodium citrate in deionized water to prepare 600 mL of a mixed solution, referred to as solution B;

[0045] Step 3: Add 300 mL of deionized water into the reactor, and simultaneously add solution A and solution B into the reactor at a rate of 10 mL / min;

[0046] Step 6: Stir for 12 hours (rotation speed is 700 rpm), wash the suspension three times with deionized water by centrifugation, and bake in a vacuum drying oven at 120° C. for 8 hours to obtain a manganese-based Prussian blue positive electrode material.

[0047] in conclusion:

[0048] Compared with Comparative Example 1, the capacity retention rates of the two embodiments are significantly better than those of Comparative Example 1. Figure 1 As shown, the gram capacity is also better than that of Comparative Example 1, and Example 2 is more obvious. Figure 2 As shown, it means that the three-step feeding is better than the two-step feeding to a certain extent. The three-step feeding introduces more doping ions, which can effectively stabilize the material structure. In addition, the particle sizes of Example 1 and Example 2 are significantly smaller than those of Comparative Example 1, as shown in Table 1, which means that the present invention can effectively reduce the particle size of manganese-based Prussian blue and improve the cycle performance.

[0049] Table 1: Particle size comparison of manganese-based Prussian blue prepared in each embodiment and comparative example

[0050] Comparative Example Example 1 Example 2 Particle size / um 8.263 1.495 2.068

[0051] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing high-performance manganese-based Prussian blue, characterized in that: The following steps are involved: Step 1, dissolving sodium ferrocyanide in deionized water to obtain solution A; dissolving different types of transition metal salts and complexing agents in deionized water to obtain different types of solutions B; Step 2, adding deionized water into the reactor, adding different types of solution B and solution A into the reactor step by step at the same or different rates, stirring to obtain a suspension after the step-by-step feeding reaction is completed, centrifuging the suspension, washing and drying the precipitate to obtain a high-performance manganese-based Prussian blue material; wherein the transition metal ions in the feeding solution B in the first step are not manganese ions alone, and the transition metal ions in the feeding solution B in the second step are manganese ions.

2. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: In step 2, in the subsequent feeding steps of the stepwise feeding, the type of transition metal ions is not limited.

3. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: Step 2: The first step of feeding the transition metal ions in solution B includes Ni 2+ , Fe 2+ 、Co 2+ , Cu 2+ 、Zn 2+ One of the 2+ 、Ni 2+ , Fe 2+ 、Co 2+ , Cu 2+ 、Zn 2+ If the transition metal ions in the first step feed solution B include Mn 2+ When Mn 2 + The content does not exceed 30% of the total amount of transition metal ions in the first step feeding solution B.

4. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: The total amount of solution A and solution B added in the first step is 1%-10% of the total amount of solution A and solution B added.

5. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: The concentrations of solution A and different types of solution B are both 0.01-0.6 mol / L.

6. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: In step 2, in different feeding steps, the feeding speeds of solution A and solution B are the same, and the feeding speed ratio between different steps is 0.5-10.

7. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: The temperature in the reactor is 10-80°C, and the stirring speed is 50-700r / min.

8. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: The complexing agent includes one or a combination of sodium pyrophosphate, sodium citrate, citric acid, and EDTA-disodium.

9. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: The transition metal salts of different ions are independently selected from one or more combinations of sulfates, acetates, nitrates and chlorides.

10. The method for preparing a high-performance manganese-based Prussian blue according to claim 1, characterized in that: Inert gas was introduced into the reactor as a protective atmosphere.

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