A method for recycling Prussian-type positive electrode materials and manganese-based Prussian white positive electrode materials prepared therefrom

Abstract

The present invention discloses a method for recycling Prussian-type positive electrode materials and a manganese-based Prussian white positive electrode material prepared therefrom, belonging to the field of battery recycling technology. The Prussian-type positive electrode material recycling method of the present invention involves reacting waste Prussian-type positive electrode materials under boiling conditions to precipitate ferrous ions and cyanide, followed by separation and recovery of ferric hydroxide through oxidative hydrolysis. Furthermore, the recovered liquid is adjusted to allow the metal ions and cyanide contained therein to undergo complexation to regenerate metal cyanate. Finally, a complexing agent and a soluble metal salt are introduced for coprecipitation to regenerate a high-purity Prussian-type material. The recycling method has simple operating steps, a high yield and purity of the final product, and is safe and non-toxic. The resulting Prussian-type material, particularly the manganese-based Prussian white positive electrode material prepared using a soluble manganese salt, has moderate particle size, high dispersibility, and high electrochemical activity, comparable to existing commercially available products.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling, and in particular to a method for recycling a Prussian-type positive electrode material and a manganese-based Prussian white positive electrode material prepared therefrom. Background Art

[0002] Prussian cathode materials are a type of sodium ion battery cathode material with an open framework structure. Specifically, they belong to metal-organic framework structure materials. The metal and ferrocyanide in their lattice are arranged in the order of Fe—C≡N—M to form a three-dimensional structural skeleton. The iron ions and metal M ions are arranged in a cubic shape, and the C≡N radicals are located on the edges of the cube. This type of material belongs to the cubic crystal system, with a particle size of about 20 to 50 nm. It has three-dimensional sodium ion insertion and extraction channels. The advantages of this type of material as a sodium ion battery cathode material are mainly three points: (1) The rigid framework structure and open large pores and sites ensure that sodium ions with large ionic radius can be reversibly inserted and extracted without changing the material structure; (2) Because of the two-electron redox reaction, the theoretical capacity of Prussian sodium cathode materials is as high as 170mAh / g; (3) The synthesis process of Prussian cathode materials is generally simple, low in toxicity, and low in preparation and raw material costs, making them suitable for large-scale production.

[0003] However, as Prussian cathode materials gradually move towards industrialization, the large amount of waste materials generated has also become a problem that needs to be solved. This is mainly because the structure of Prussian sodium cathode materials is different from that of conventional cathode materials, and the recycling method is also different. The material contains [Fe(CN)6] 4- It has a certain low toxicity, but may cause environmental pollution if not handled properly. Summary of the Invention

[0004] Based on the defects of the existing technology, the purpose of the present invention is to provide a method for recovering Prussian-type positive electrode materials. The method mainly separates the iron ions from the system through azeotropic treatment, and then re-complexes the separated cyanide with the metal ions in the separation system through complexation and finally converts it into Prussian-type materials, thereby achieving safe and effective recovery of various ions in the waste materials.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for recycling a Prussian cathode material comprises the following steps:

[0007] (1) The Prussian cathode material separated from the waste battery is immersed in an acidic solution with a pH value less than 2.5 and reacted under boiling conditions for 0.5 to 2 hours to obtain a treatment solution A;

[0008] (2) introducing oxygen into the treatment solution A and adjusting the solution pH to 2.7-4 to cause precipitation reaction to be complete, filtering to obtain iron hydroxide precipitate and treatment solution B;

[0009] (3) The pH of the treatment solution B is adjusted to 6-10 and stabilized, a complexing agent and a soluble metal salt are added to carry out a coprecipitation reaction until it is complete, and the solution is filtered to obtain a Prussian material.

[0010] In the method for recovering the Prussian cathode material of the present invention, the Prussian cathode material is first immersed in a strong acid solution and reacted under boiling conditions to precipitate metal ions such as manganese ions and sodium ions in the material, while [Fe(CN)6] 4- The stable structure is also destroyed and ferrous ions and cyanide are precipitated. At this time, the ferrous ions precipitated in the solution are oxidized and hydrolyzed by oxygen and a specific weakly acidic environment to form ferric hydroxide in one step and separate from the solution system; further, when the pH of the solution after separation and precipitation is adjusted to 6-10, the metal ions and cyanide in the solution undergo complexation to generate metal cyanate, and finally a complexing agent and a soluble metal salt are introduced for co-precipitation to regenerate a high-purity Prussian material. The recovery method has simple operating steps, a high yield and high purity of the final product, and is safe and non-toxic. According to actual conditions, the recovered product can be selected to further prepare a high-performance Prussian cathode material.

[0011] Preferably, the Prussian cathode material is a Na2Mn[Fe(CN)6] cathode material.

[0012] Since iron and manganese are two complementary elements commonly used in the field of battery positive electrode materials, when the iron element in the material is precipitated, under optimal conditions, the manganese element can effectively and highly actively complex with the remaining cyanide to form [Mn(CN)6] 4- .

[0013] More preferably, the soluble metal salt in step (3) is a soluble manganese salt.

[0014] When the active ions in the treatment solution B are [Mn(CN)6] 4- When introducing soluble manganese salt and complexing agent for co-precipitation reaction, a highly active manganese-rich manganese-based Prussian white positive electrode material can be generated. This material not only has uniformly dispersed particles, but also has high electrochemical activity, which is comparable to existing commercial materials on the market and has a high production cost-effectiveness.

[0015] Preferably, the complexing agent and the soluble manganese salt are mixed before being added into the treatment solution B.

[0016] Premixing the complexing agent and soluble manganese salt can effectively reduce the reaction rate during the coprecipitation reaction, reduce the content of coordinated water and interstitial water, thereby improving the dispersibility and quality of the obtained material, and ultimately improving the product's gram capacity and electrochemical cycle stability.

[0017] Preferably, in step (3), after pH adjustment, the treatment solution B is subjected to the following treatment before the complexing agent and the soluble metal salt are added: the concentration of metal cyanate in the treatment solution B is detected and adjusted to 0.3-1 mol / L.

[0018] By detecting and adjusting the concentration of metal cyanate, the amount of soluble metal salt to be added can be effectively known to avoid adding too much or too little, which would cause waste of raw materials or the generation of by-products.

[0019] Preferably, the complexing agent in step (3) is at least one of maleic acid, citric acid, citric acid, ethylenediaminetetraacetic acid (EDTA), sodium citrate, and ammonia water.

[0020] Preferably, the concentration of the complexing agent in step (3) is 0.4 to 15 mol / L.

[0021] Preferably, the temperature during the co-precipitation reaction in step (3) is 30-90° C. and the time is 1-5 hours.

[0022] Preferably, the Prussian material obtained in step (3) is further subjected to aging and drying treatments.

[0023] More preferably, the aging time is 3 to 48 hours; the drying temperature is 60 to 100° C., and the drying time is 4 to 12 hours.

[0024] Another object of the present invention is to provide a manganese-based Prussian white positive electrode material, which is recovered and prepared by the Prussian white positive electrode material recovery method of the present invention.

[0025] When waste manganese-based Prussian white cathode materials are recycled, it is only necessary to use a soluble manganese salt and a re-complexed manganese cyanate to carry out a co-precipitation reaction in the above-mentioned recycling method to directly obtain a manganese-based Prussian white cathode material with moderate particle size, good dispersibility and high electrochemical activity. The material preparation operation steps are simple, the waste material recycling rate is high, the economic benefits are high, and the performance quality of the output material is comparable to the existing commercially available manganese-based Prussian white cathode material.

[0026] The beneficial effect of the present invention is that the present invention provides a method for recovering Prussian-type positive electrode materials, wherein the method reacts the waste Prussian-type positive electrode materials under boiling conditions to precipitate ferrous ions and cyanide, and then separates and recovers ferric hydroxide through oxidative hydrolysis; further, by adjusting the recovered liquid, the metal ions and cyanide contained therein are complexed to regenerate metal cyanate, and finally a complexing agent and a soluble metal salt are introduced for coprecipitation to regenerate high-purity Prussian-type materials. The recovery method has simple operating steps, a high yield and high purity of the final product, and is safe and non-toxic. The obtained Prussian-type materials, especially the manganese-based Prussian white positive electrode materials prepared using soluble manganese salts, have moderate particles, high dispersibility and electrochemical activity, and are comparable to existing commercially available products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of the manganese-based Prussian white positive electrode material recovered and prepared by the recovery method of the Prussian-type positive electrode material described in Example 1 of the present invention.

[0028] Figure 2 This is the XRD pattern of the manganese-based Prussian white positive electrode material recovered and prepared by the recovery method of the Prussian-type positive electrode material described in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments / comparative examples. Its purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The experimental reagents, raw materials and instruments designed for the implementation of the present invention and the comparative examples are all commonly used ordinary reagents, raw materials and instruments unless otherwise specified.

[0030] Example 1

[0031] An embodiment of the method for recycling the Prussian cathode material of the present invention comprises the following steps:

[0032] (1) Scrape off the positive electrode material separated from the waste manganese-based Prussian white sodium Na2Mn[Fe(CN)6] battery, collect 80 kg, soak it in 100 L of 3 mol / L sulfuric acid solution with a pH value less than 2.5, and react it under boiling conditions for 1 hour to obtain treated solution A;

[0033] (2) introducing oxygen into treatment solution A and adjusting the solution pH to 3.5 with water to allow precipitation reaction to complete, filtering the red precipitate to obtain iron hydroxide precipitate and the remaining treatment solution B;

[0034] (3) The pH of the treatment solution B was adjusted to 8 and stabilized. The concentration of manganese cyanate in the solution was detected by ICP to be 0.312 mol / L. The solution was transferred to a reactor and 100 L of 2 mol / L citric acid and 100 L of 2 mol / L manganese sulfate solution were directly added and mixed. The coprecipitation reaction was carried out at 70 ° C for 1 to 5 hours until complete, aged for 48 hours, filtered, and dried at 100 ° C for 10 hours to obtain a manganese-based Prussian white positive electrode material. The obtained material was observed by scanning electron microscopy. Figure 1 As shown, it can be seen that the material particles are evenly dispersed, moderate in size, and have no obvious agglomeration; further XRD test results are as follows Figure 2 As shown, the material has high purity and no obvious impurity characteristic peaks.

[0035] Example 2

[0036] An embodiment of the method for recovering the Prussian white cathode material of the present invention is provided. The only difference between this embodiment and embodiment 1 is that step (3) of the recovery method is: adjusting the pH of the treatment solution B to 8 and stabilizing it, using ICP to detect the concentration of manganese cyanate in the solution to be 0.312 mol / L, transferring it to a reactor, adding 200 L of precursor solution and mixing, carrying out a coprecipitation reaction at 70° C. for 1 to 5 hours until complete, aging for 48 hours, filtering, and drying at 100° C. for 10 hours to obtain a manganese-based Prussian white cathode material; the precursor solution is an aqueous solution of citric acid and manganese sulfate, and the concentrations of citric acid and manganese sulfate are both 1 mol / L.

[0037] Example 3

[0038] An embodiment of the method for recovering the Prussian white cathode material of the present invention is provided. The only difference between this embodiment and embodiment 1 is that step (3) of the recovery method is as follows: (3) adjusting the pH of the treatment solution B to 10 and stabilizing it, using ICP to detect the concentration of manganese cyanate in the solution to be 0.305 mol / L, transferring it to a reactor, directly adding 100 L of 2 mol / L complexing agent citric acid and 100 L of 2 mol / L manganese sulfate solution to mix, carrying out a coprecipitation reaction at 70° C. for 1 to 5 hours until complete, aging for 48 hours, filtering, and drying at 100° C. for 10 hours to obtain a manganese-based Prussian white cathode material.

[0039] Comparative Example 1

[0040] A method for recycling a Prussian cathode material comprises the following steps:

[0041] (1) Scrape off the positive electrode material separated from the waste manganese-based Prussian white sodium Na2Mn[Fe(CN)6] battery, collect 80 kg, soak it in 100 L of 3 mol / L sulfuric acid solution with a pH value less than 2.5, and react it under boiling conditions for 1 hour to obtain treated solution A;

[0042] (2) oxygen was introduced into the treatment solution A and the pH of the solution was adjusted to 6 with water to allow the precipitation reaction to proceed to completion. At this time, a red precipitate was observed to be generated first, and then a brown precipitate was generated. After filtering the precipitate, a mixed precipitate of iron hydroxide and manganese oxyhydroxide was obtained, as well as the remaining treatment solution B;

[0043] (3) The pH of the treatment solution B was adjusted to 8 and stabilized. The concentration of manganese cyanate in the solution was detected by ICP and was 0.109 mol / L. The content was too low and could not be further used to synthesize manganese-based Prussian white positive electrode materials.

[0044] Comparative Example 2

[0045] A method for recycling a Prussian cathode material comprises the following steps:

[0046] (1) Scrape off the positive electrode material separated from the waste manganese-based Prussian white sodium Na2Mn[Fe(CN)6] battery, collect 80 kg, soak it in 100 L of 3 mol / L sulfuric acid solution with a pH value less than 2.5, and react it under boiling conditions for 1 hour to obtain treated solution A;

[0047] (2) introducing oxygen into treatment solution A and adjusting the solution pH to 3.5 with water to allow precipitation reaction to complete. After filtering the red precipitate, iron hydroxide precipitate and the remaining treatment solution B are obtained;

[0048] (3) The pH of the treatment solution B was adjusted to 11 and stabilized. The concentration of manganese cyanate in the solution was detected by ICP and was 0.11 mol / L. The content was too low and could not be further used to synthesize manganese-based Prussian white positive electrode materials.

[0049] Effect Examples

[0050] In order to verify the properties and performance of the manganese-based Prussian white positive electrode material prepared by recycling the Prussian-type positive electrode material described in the present invention, the particle size distribution (D10, D50, D90), specific surface area, and tap density of the products of each embodiment were tested. At the same time, the material was used as the positive electrode material for sodium ion batteries to prepare positive electrode sheets. Commercial sodium electrolyte separators and sodium sheets were used to prepare sodium ion half-cells. At an operating voltage of 2 to 4 V, charge and discharge tests were carried out at a rate of 0.2C and the discharge specific capacity was recorded. At the same time, a commercially available manganese-rich manganese-based Prussian white positive electrode material was used as a control sample and the same treatment and testing were performed for comparison with the products of each embodiment. The test results are shown in Table 1.

[0051] Table 1

[0052]

[0053] As can be seen from Table 1, the particle size distribution and uniformity of the products re-prepared by the recycling method described in each embodiment are almost consistent with those of the existing commercial manganese-rich manganese-based Prussian white positive electrode material on the market, and the specific surface area and tap density are also relatively similar. In terms of electrochemical performance, the discharge specific capacity of the products is also comparable to that of the commercial material, indicating that the recycling method of the Prussian-type positive electrode material described in the present invention can not only effectively solve the problem of recycling existing waste Prussian-type positive electrode materials, but also the performance of the products prepared by further processing the recovered materials is comparable to that of commercial products, and can completely replace the production and use of existing commercial manganese-rich manganese-based Prussian white positive electrode materials.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for recovering Prussian cathode materials, characterized in that: The following steps are involved: (1) The Prussian cathode material separated from the waste battery is immersed in an acidic solution with a pH value less than 2.5 and reacted under boiling conditions for 0.5 to 2 hours to obtain a treatment solution A; (2) introducing oxygen into the treatment solution A and adjusting the solution pH to 2.7-4 to cause precipitation reaction to be complete, filtering to obtain iron hydroxide precipitate and treatment solution B; (3) Adjust the pH of the treatment solution B to 6-10 and stabilize it, detect the concentration of metal cyanate in the treatment solution B and adjust it to 0.3-1 mol / L, add a complexing agent and a soluble metal salt to carry out a coprecipitation reaction until it is complete, filter, and obtain a Prussian material.

2. The method for recycling Prussian cathode materials according to claim 1, wherein: The Prussian cathode material is a Na2Mn[Fe(CN)6] cathode material.

3. The method for recycling Prussian cathode materials according to claim 2, wherein: The soluble metal salt in step (3) is a soluble manganese salt.

4. The method for recycling Prussian cathode materials according to claim 1, wherein: The complexing agent and the soluble manganese salt are mixed before being added into the treatment solution B.

5. The method for recycling Prussian cathode materials according to claim 1, wherein: The complexing agent in step (3) is at least one of maleic acid, citric acid, citric acid, ethylenediaminetetraacetic acid, sodium citrate, and ammonia water.

6. The method for recycling Prussian cathode materials according to claim 5, wherein: The concentration of the complexing agent in step (3) is 0.4-15 mol / L.

7. The method for recycling Prussian cathode materials according to claim 1, wherein: The co-precipitation reaction in step (3) is carried out at a temperature of 30 to 90° C. and for a time of 1 to 5 hours.

8. The method for recycling Prussian cathode materials according to claim 1, wherein: The Prussian material obtained in step (3) is further subjected to aging and drying treatments; The aging time is 3 to 48 hours; the drying temperature is 60 to 100° C. and the drying time is 4 to 12 hours.

9. A manganese-based Prussian white positive electrode material, characterized in that: The cathode material is recovered and prepared by the recovery method of the Prussian cathode material according to any one of claims 1 to 8.

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