WO2024066182A1

WO2024066182A1 - Prussian-type sodium ion positive electrode material and recycling method therefor

Info

Publication number: WO2024066182A1
Application number: PCT/CN2023/077899
Authority: WO
Inventors: 谢英豪; 李爱霞; 余海军; 李长东
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-09-29
Filing date: 2023-02-23
Publication date: 2024-04-04
Also published as: CN115579539A

Abstract

Disclosed·in the present application are a Prussian-type sodium ion positive electrode material and a recycling method therefor. Provided in the described present application is the recycling method for the Prussian-type sodium ion positive electrode material, comprising the following steps: obtaining a positive electrode material; cleaning or soaking the positive electrode material by means of an acidic solution; regulating the concentrations of transition metal ions, ferrocyanide radicals and sodium ions in the solution A to preset concentrations; adding a complexing agent solution into the solution B for mixing reaction; filtering the solution C to obtain filter residues; and drying the filter residues to obtain the Prussian-type sodium ion positive electrode material. The recycling method for the Prussian-type sodium ion positive electrode material can recycle low-toxicity [Fe(CN)6]4- in waste Prussian-type sodium batteries, and thus avoid great pressure exerted on the environment by directly discarded Prussian-type sodium ion positive electrode materials, thereby protecting the ecological equilibrium. In addition, the produced Prussian-type sodium ion positive electrode material has good regeneration performance and thus can meet the commercial requirements.

Description

Prussian sodium ion positive electrode material and recovery method thereof

Technical Field

The embodiments of the present application relate to the field of battery technology, for example, a Prussian sodium ion positive electrode material and a recovery method thereof.

Background technique

Prussian sodium ion cathode materials are a type of sodium ion battery cathode materials with an open framework structure. It belongs to the metal-organic framework structure. The metal and ferrocyanide in the lattice are arranged according to Fe—C≡N—M to form a three-dimensional structural skeleton. The Fe ions and metal M ions are arranged in a cubic shape, and the C≡N roots 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, and has a three-dimensional sodium ion insertion and extraction channel.

It has three main advantages: (1) The rigid framework structure and open large pores and sites ensure that sodium ions with larger ionic radius can be reversibly inserted and removed without changing the material structure; (2) Because of the double-electron redox reaction, the theoretical capacity of Prussian sodium ion positive electrode materials is as high as 170mAhg-1; (3) The simple synthesis process, low toxicity and low cost make this material suitable for large-scale production; (4) Prussian sodium ion positive electrode materials have obvious cost advantages over lithium battery materials and even other sodium ion battery positive electrode materials. Therefore, Prussian positive electrode materials are gradually moving towards industrialization, and Prussian sodium ion batteries are also moving towards industrialization.

However, the industrialization of Prussian sodium-ion batteries will generate a large amount of waste Prussian sodium-ion cathode materials, which contain low-toxic [Fe(CN) ₆ ] ^4- . If they are directly discarded, they will cause great pressure on the environment and destroy the ecological balance. Therefore, how to deal with these waste Prussian sodium-ion cathode materials is an urgent problem to be solved.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

The embodiment of the present application provides a method for improving the recovery rate of ferrocyanate to reduce the pressure on the environment, and obtains a Prussian sodium ion positive electrode material with good regeneration performance and a recovery method thereof.

The embodiments of the present application are implemented through the following technical solutions:

A method for recovering a Prussian sodium ion cathode material comprises the following steps:

obtaining a positive electrode material;

The positive electrode material is cleaned or soaked with an acidic solution to obtain a solution A;

Adjusting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A to preset concentrations to obtain a solution B;

Adding a complexing agent solution to the solution B for a mixing reaction to obtain a solution C;

The solution C is filtered to obtain a filter residue;

The filter residue is dried to obtain a Prussian sodium ion positive electrode material.

In one embodiment, the acidic solution is a non-oxidizing acid solution.

In one embodiment, the pH of the solution A is 3-6.

In one embodiment, the complexing agent solution includes at least one of maleic acid, citric acid, citric acid, EDTA, sodium citrate and ammonia water.

In one embodiment, the concentration of the complexing agent solution is 0.4 mol/L to 15 mol/L.

In one embodiment, the preset concentration of the transition metal ion is 0.4 mol/L to 2 mol/L; and

The preset concentration of ferrocyanate is 0.3 mol/L to 0.6 mol/L; and

The preset concentration of the sodium ions is 0.3 mol/L to 0.6 mol/L.

In one embodiment, the mixed reaction is carried out at a pH of 6.5 to 9.5 and an inert atmosphere.

In one of the embodiments, the drying conditions are: temperature of 50° C. to 80° C., and time of 8 h to 12 h.

In one embodiment, the filtrate obtained by filtering the solution C is recycled.

In one embodiment, the acidic solution is an inorganic acid that does not react with the filtering metal.

A Prussian sodium ion positive electrode material is produced by the Prussian sodium ion positive electrode material recovery method described in any of the above embodiments.

Compared with the related art, the embodiments of the present application have at least the following advantages:

The above-mentioned Prussian sodium ion positive electrode material recovery method uses an acidic solution to clean or soak the positive electrode material so that the active substance on the positive electrode material can be dissolved in the acidic solution to obtain solution A, that is, the transition metal ions, sodium ions and acid-soluble substances such as ferrocyanate in the positive electrode material are free in the acidic solution to form solution A, and then the transition metal ion concentration, ferrocyanate concentration and sodium ion concentration in solution A are adjusted to a preset concentration, and then solution B and a complexing agent solution are mixed and reacted so that ferrocyanate can react with transition metal ions and sodium ions to precipitate to generate Prussian crystals, and finally solution C is filtered, and the filtered residue is dried to obtain a Prussian crystal with good regeneration performance. Sodium ion positive electrode material. By adopting the above-mentioned recycling method, the low-toxic [Fe(CN) ₆ ] ^4- in the discarded Prussian sodium battery can be recycled, avoiding the direct discard of the Prussian sodium ion positive electrode material causing greater pressure on the environment, thereby protecting the ecological balance. In addition, the produced Prussian sodium ion positive electrode material has good regeneration performance, meets the market requirements, and can be directly put into production, thereby reducing the production cost of the Prussian sodium ion battery.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of a method for recovering a Prussian sodium ion cathode material according to an embodiment of the present application;

FIG. 2 is a SEM image of a Prussian sodium ion positive electrode material product according to an embodiment of the present application.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to suppress this application. The term "and/or" used herein includes any and all combinations of one or more of the related listed items.

The embodiment of the present application provides a method for recovering a Prussian sodium ion positive electrode material, comprising the following steps: obtaining a positive electrode material; washing or soaking the positive electrode material with an acidic solution to obtain a solution A; The concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A are adjusted to preset concentrations to obtain a solution B; a complexing agent solution is added to the solution B for a mixing reaction to obtain a solution C; the solution C is filtered to obtain a filter residue; the filter residue is dried to obtain a Prussian sodium ion positive electrode material.

The above-mentioned Prussian sodium ion positive electrode material recovery method uses an acidic solution to wash or soak the positive electrode material so that the active material on the positive electrode material can be dissolved in the acidic solution to obtain solution A, that is, the transition metal ions, sodium ions and acid-soluble substances such as ferrocyanate in the positive electrode material are free in the acidic solution to form solution A, and then the transition metal ion concentration, ferrocyanate concentration and sodium ion in solution A are adjusted to a preset concentration, and then solution B and the complexing agent solution are mixed and reacted so that ferrocyanate can react with transition metal ions and sodium ions to precipitate and generate Prussian crystals, and finally solution C is filtered, and the filtered residue is dried to obtain a Prussian sodium ion positive electrode material with good regeneration performance. The above-mentioned recovery method can recycle the low-toxic [Fe(CN) ₆ ] ^4- in the discarded Prussian sodium battery, avoiding the direct discard of the Prussian sodium ion positive electrode material from causing greater pressure on the environment, thereby protecting the ecological balance. In addition, the produced Prussian sodium-ion positive electrode material has good regeneration performance, meets market requirements, and can be directly put into production, thereby reducing the production cost of Prussian sodium-ion batteries.

Please refer to FIG. 1. To better understand the technical solution and beneficial effects of the present application, the present application is further described in detail below in conjunction with specific examples. A Prussian sodium ion cathode material recovery method according to one embodiment includes some or all of the following steps:

S110, obtaining positive electrode materials, which can be obtained from waste Prussian sodium-ion batteries for backup.

S120, washing or soaking the positive electrode material with an acidic solution to obtain solution A. It can be understood that since the positive electrode material obtained from the waste Prussian sodium ion battery includes aluminum foil and active material, the positive electrode material is washed or soaked with an acidic solution to dissolve the active material, so that the transition metal ions, sodium ions and acid-soluble substances such as ferrocyanate in the active material are freed in the acidic solution to form solution A, thereby achieving separation of the aluminum foil and the active material, so that the active material can be better collected later.

S130, adjusting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A to preset concentrations so that the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A meet the regeneration requirements, and obtaining solution B for standby use.

S140, mixing the solution B and the complexing agent solution to obtain a solution C.

It should be noted that, since the reaction rate of ferrous ions and ferrocyanide is very fast during the formation of Prussian crystals, the final Prussian sodium-ion battery positive electrode material often contains more ferrocyanide vacancy defects and crystal water. The presence of ferrocyanide vacancy defects will reduce the structural stability of the Prussian sodium-ion battery positive electrode material, and the repeated insertion and extraction of sodium ions may cause the structure of the Prussian sodium-ion battery positive electrode material to collapse. At the same time, crystal water will occupy the position of ferrocyanide vacancy defects or the gap position of the crystal structure, thereby hindering the transport of sodium ions in the crystal structure, thereby reducing the conductivity of the Prussian sodium-ion battery. Therefore, the present application performs a mixed reaction on solution B and the complexing agent solution so that the complexing agent solution can effectively inhibit the reaction rate of the transition metal ions and ferrocyanide, thereby effectively avoiding the phenomenon that the vacancy defects of the Prussian crystals generated by the excessively fast reaction rate of the transition metal ions and ferrocyanide are more serious, so that the prepared Prussian sodium ion positive electrode material has good regeneration performance. As shown in FIG2 , the regenerated Prussian sodium ion positive electrode material has good morphology and meets the requirements for market sales.

S150, filtering the solution C to obtain a filter residue to separate the Prussian precipitate from the liquid.

S160, drying the filter residue to effectively remove the crystal water in the Prussian precipitate to obtain a Prussian sodium ion positive electrode material, so that the obtained Prussian sodium ion positive electrode material has good regeneration performance, and the regenerated Prussian sodium ion positive electrode material can be directly put into production, thereby effectively reducing the production cost of Prussian sodium ion batteries.

The above-mentioned Prussian sodium ion positive electrode material recovery method uses an acidic solution to wash or soak the positive electrode material so that the active material on the positive electrode material can be dissolved in the acidic solution to obtain solution A, that is, the transition metal ions, sodium ions and acid-soluble substances such as ferrocyanate in the positive electrode material are free in the acidic solution to form solution A, and then the transition metal ion concentration, ferrocyanate concentration and sodium ion in solution A are adjusted to a preset concentration, and then solution B and the complexing agent solution are mixed and reacted so that ferrocyanate can react with transition metal ions and sodium ions to precipitate and generate Prussian crystals, and finally solution C is filtered, and the filtered residue is dried to obtain a Prussian sodium ion positive electrode material with good regeneration performance. The above-mentioned recovery method can recycle the low-toxic [Fe(CN) ₆ ] ^4- in the discarded Prussian sodium battery, avoiding the direct discard of the Prussian sodium ion positive electrode material from causing greater pressure on the environment, thereby protecting the ecological balance.

Further, referring to FIG. 2 , the above-mentioned recovery method is used to produce the Prussian sodium ion The positive electrode material has good regeneration performance, meets market requirements, and can be directly put into production, thereby reducing the production cost of Prussian-type sodium-ion batteries.

In one embodiment, the acidic solution is a non-oxidizing acid solution. It is understandable that since the cathode material obtained from the waste Prussian sodium ion battery contains a large amount of ferrocyanide, and ferrocyanide is easy to generate ferrocyanide under the oxidant, and ferrocyanide is more likely to undergo hydration than ferrocyanide to produce toxic hydrocyanic acid, thereby causing greater harm to the human body. Therefore, the acidic solution of the present application is a non-oxidizing acid, which can ensure that the transition metal ions, sodium ions and ferrocyanate on the active material are freed from the non-oxidizing acid to form solution A, and the added non-oxidizing acid can effectively inhibit the oxidation of ferrocyanide to ferrocyanide, so as to improve the recovery rate of ferrocyanide, and at the same time, it can also avoid the generation of ferrocyanide with higher toxicity, so as to ensure the safety of the Prussian sodium ion cathode material in the recovery process, so as to reduce the harm of toxic hydrocyanic acid to the human body and the environment.

It should be noted that, compared with traditional sodium ion battery or lithium ion battery recycling methods, most of them use high temperature calcination to quickly separate the active material from the aluminum foil. However, for the Prussian sodium ion battery recycling of the present application, since the positive electrode material obtained from the dismantling of the discarded Prussian sodium ion battery contains a large amount of ferrocyanide, and since ferrocyanide is easily decomposed into _N2 under high temperature conditions, the structure of ferrocyanide is destroyed, resulting in a low recovery rate of ferrocyanide, and thus the maximum benefit of the Prussian sodium ion battery cannot be achieved. Therefore, the present application adopts a non-oxidizing acid, which can ensure that ferrocyanide is not easily decomposed under the conditions of non-oxidizing acid, so as to ensure that the structure of ferrocyanide will not change to the greatest extent, thereby improving the recovery rate of ferrocyanide. On the other hand, the added non-oxidizing acid can also effectively inhibit the oxidation of ferrocyanide to ferrocyanide, so as to further improve the recovery rate of ferrocyanide. At the same time, it can also avoid the generation of highly toxic ferrocyanide, so as to ensure the safety of Prussian sodium ion positive electrode materials during the recovery process, so as to reduce the harm of toxic hydrocyanic acid to human body and environment.

In one embodiment, the non-oxidizing acid solution includes at least one of a dilute HCl solution, a H ₂ CO ₃ solution, a dilute sulfuric acid solution, and a phosphoric acid solution. It is understood that the non-oxidizing acid solution refers to a type of acid solution that ionizes H ⁺ when dissolved in water and has weak oxidizing properties, so as to effectively avoid the decomposition of ferrocyanide and improve the recovery rate of ferrocyanide.

Furthermore, in one embodiment, the pH of the solution A is 3 to 6. It can be understood that since ferrocyanide is easily oxidized to ferrocyanide under strong acidic conditions, the present application uses a non-oxidizing acid to directly dissolve the active substance and controls the pH of the solution A to be 3 to 6, which can provide a warm and stable environment for ferrocyanide. and conditions to better avoid the oxidative decomposition of ferrocyanide, thereby ensuring the recovery rate of ferrocyanide and avoiding the formation of ferrocyanide, thereby increasing the maximum benefit of recycling discarded Prussian sodium-ion batteries, thereby reducing harm to the environment and human body and improving the safety of the recycling process.

In one embodiment, the concentration of the non-oxidizing acid solution is 0.05mol/L to 0.5mol/L. It is understandable that if the concentration is lower than 0.05mol/L, it is difficult to ensure that the non-oxidizing acid solution can fully dissolve the active substance from the aluminum foil, which is likely to cause a low recovery rate of ferrocyanide; if the concentration of the non-oxidizing acid solution is higher than 0.5mol/L, it is easy to cause ferrocyanide to decompose. Therefore, the present application controls the concentration of the non-oxidizing acid solution to 0.05mol/L to 0.5mol/L. In this way, the added non-oxidizing acid solution can not only fully dissolve the active substance on the aluminum foil, but also avoid the phenomenon that ferrocyanide is easily oxidized to ferrocyanide with higher toxicity. In this way, not only the recovery rate of ferrocyanide is improved, but also the safety of the recovery process is ensured.

In one embodiment, before the step of obtaining the positive electrode material, the following step is also included: dismantling the discarded Prussian sodium ion battery to separate the positive electrode material, the negative electrode material and the separator, so as to obtain the positive electrode material.

In one of the embodiments, the step of washing or soaking the positive electrode material with an acidic solution includes the following specific steps: scraping the active substance on the aluminum foil into a non-oxidizing acid solution to obtain a mixed solution to quickly separate the aluminum foil from the active substance, thereby improving production efficiency; washing or soaking the positive electrode material with the mixed solution to fully dissolve the active substance remaining on the aluminum foil to achieve comprehensive recovery of ferrocyanide in the positive electrode material, thereby improving the recovery rate of ferrocyanide.

In one embodiment, before the step of adjusting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A to preset concentrations, and after the step of washing or soaking the positive electrode material with an acidic solution, the following step is also included: detecting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A.

It can be understood that the concentrations of transition metal ions, ferrocyanate and sodium ions in solution A are detected by using an ICP (Inductive Coupled Plasma Emission Spectrometer) inductively coupled plasma spectrometer to quickly obtain the actual concentrations of transition metal ions, ferrocyanate and sodium ions in solution A, so as to better adjust the concentrations of transition metal ions, ferrocyanate and sodium ions in solution A to meet the requirements for preparing regenerated Prussian sodium ion positive electrode materials. It is worth mentioning that since the ICP (Inductive Coupled Plasma Emission Spectrometer) inductively coupled plasma spectrometer is provided with multiple detection units, each detection unit can detect the concentration of a corresponding element, so that It is able to realize the rapid detection of transition metal ions, ferrocyanate and sodium ions in solution A, thereby improving the recovery efficiency.

In one embodiment, the complexing agent solution is a mixture of maleic acid, EDTA and sodium citrate. It can be understood that since the added maleic acid has good scale inhibition performance, can adsorb impurities, has good colloidal properties and dispersing effects, it can not only improve the dispersibility of the complexing agent to ensure the preparation of uniform Prussian crystals with less impurities, but also cooperate with the use of EDTA and sodium citrate. The added EDTA and sodium citrate can effectively improve the complexing ability, complexing capacity and biodegradability of the complexing agent to obtain a complexing agent with higher complexing capacity, stronger complexing ability and good biodegradability. In this way, the addition of the compounded complexing agent is beneficial to the dispersibility of the complexing agent in solution B on the one hand, thereby facilitating the generation of uniform Prussian crystals with less impurities, so as to reduce the vacancy defects and crystal water content of the Prussian crystals, and obtain Prussian sodium ion positive electrode materials with excellent electrochemical properties; on the other hand, it helps to improve the biodegradability of the complexing agent to reduce the pressure on the environment, and on the other hand, it also ensures that the complexing capacity is higher to improve the recovery rate of ferrocyanide and the Prussian crystals with more stable complexing ability are obtained, so as to ensure that the Prussian crystals with more stable structure are obtained. It is worth mentioning that the added sodium citrate can also provide sodium ions to provide sufficient sodium source for Prussian crystals, thereby ensuring that ferrocyanide, transition metal ions and sodium ions can fully and comprehensively react to improve the recovery rate of ferrocyanide.

In one embodiment, the mass ratio of maleic acid, EDTA and sodium citrate is 1: (0.5-0.8): 1. It can be understood that by compounding maleic acid, EDTA and sodium citrate in a mass ratio of 1: (0.5-0.8): 1, a complexing agent with good dispersibility, easy degradation, high complexing capacity and strong complexing ability can be obtained.

In one embodiment, the concentration of the complexing agent solution is 0.4 mol/L to 15 mol/L, so as to ensure that the complexing agent can better control the reaction rate of ferrocyanide and transition metal ions, so as to effectively slow down the speed of forming Prussian crystals, reduce the vacancy defects and crystal water content of Prussian crystals, and obtain Prussian sodium ion positive electrode materials with excellent electrochemical properties.

In one embodiment, the step of adjusting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A to preset concentrations includes the following specific steps: first adjusting the concentration of ferrocyanate, then adjusting the concentration of transition metal ions, and finally adjusting the concentration of sodium ions.

It can be understood that if the concentration of transition metal ions is adjusted first and then the concentration of ferrocyanate is adjusted, the final If the concentration of sodium ions is adjusted later, the sufficient transition metal ions added can react quickly with ferrocyanate to form Prussian crystals with more vacancy defects, which is not conducive to the formation of Prussian crystals. Therefore, the present application first adjusts the ferrocyanate in solution A to increase the concentration of ferrocyanate in solution A, thereby reducing the vacancy defects of ferrocyanate generated by Prussian crystals, that is, ensuring that under the condition of a higher concentration of ferrocyanate, the vacancy defects of ferrocyanate formed by ferrocyanate in Prussian crystals are less, which is conducive to the generation of Prussian crystals with fewer vacancy defects, and then replenishes the concentration of transition metal ions to a preset concentration to ensure that the recovered transition metal ions can fully react with ferrocyanate, and then ferrocyanate reacts with the subsequently added transition metal ions, that is, the transition metal ions and ferrocyanate react in stages to better slow down the excessive reaction rate of the transition metal ions and ferrocyanate to cause the generation of Prussian crystals with more serious vacancy defects, and finally adjusts the sodium ions so that the generated Prussian crystals can meet the requirements of regeneration performance.

In one of the embodiments, the transition metal ion concentration is adjusted by using a transition metal salt so that the transition metal ion concentration reaches a preset requirement. Specifically, in one of the embodiments, the preset concentration of the transition metal ion is 0.4 mol/L to 2 mol/L to ensure that the transition metal ions in solution B meet the production requirements of the regenerated Prussian sodium ion positive electrode material.

In one of the embodiments, the concentration of transition metal ions is adjusted by using ferrocyanate, so that the concentration of ferrocyanate reaches the preset requirement. Specifically, in one of the embodiments, the preset concentration of ferrocyanate is 0.3 mol/L to 0.6 mol/L, so as to ensure that the ferrocyanate in solution B reaches the production requirement of the regenerated Prussian sodium ion positive electrode material.

In one embodiment, sodium salt is used to adjust the transition metal ion concentration so that the ferrocyanate concentration reaches a preset requirement. Specifically, in one embodiment, the preset concentration of sodium ions is 0.3 mol/L to 0.6 mol/L to ensure that the sodium ions in solution B meet the production requirements of the regenerated Prussian sodium ion positive electrode material.

In one embodiment, the transition metal salt includes at least one of a divalent Mn salt, a divalent Fe salt, a divalent Co salt, a divalent Ni salt, a divalent Cu salt and a divalent Zn salt, so as to adjust the transition metal concentration.

In one embodiment, the divalent Mn salt includes at least one of MnCl ₂ and MnSO ₄ .

In one embodiment, the divalent Fe salt includes at least one of FeCl ₂ and FeSO ₄ .

In one embodiment, the divalent Co salt includes at least one of CoCl ₂ and CoSO ₄ .

In one embodiment, the divalent Ni salt includes at least one of NiCl ₂ and NiSO ₄ .

In one embodiment, the divalent Cu salt includes at least one of CuCl ₂ and CuSO ₄ .

In one embodiment, the divalent Zn salt includes at least one of ZnCl ₂ and ZnSO ₄ .

In one embodiment, the ferrocyanide-containing salt includes at least one of potassium ferrocyanide and sodium ferrocyanide.

In one embodiment, the sodium salt includes at least one of NaCl ₂ and NaSO ₄ .

In one of the embodiments, the step of mixing the solution B and the complexing agent solution comprises the following specific steps: adding water to the reactor for preheating, and passing the solution B and the complexing agent solution into the reactor for mixing reaction, so as to achieve the mixing reaction of the solution B and the complexing agent solution. Specifically, in one of the embodiments, the mixing reaction is carried out under the conditions of pH 6.5 to 9.5 and inert atmosphere to ensure the normal reaction of the solution B and the complexing agent solution. Further, in one of the embodiments, the flow ratio of the solution B and the complexing agent solution is 1 to 1, so as to ensure that the complexing agent solution can be better mixed with the solution B, so as to more effectively suppress the speed of generating Prussian crystals, so as to obtain Prussian crystals with fewer vacancy defects. Further, the preheating temperature is 40°C to 50°C.

In one embodiment, before the step of filtering the solution C, the following step is further included: performing an aging reaction on the solution C. It can be understood that the aging reaction on the solution C is conducive to the formation of Prussian crystals, so as to avoid the formation of Prussian crystals with more vacancy defects. Further, in one embodiment, the aging time is 8h to 10h.

In one of the embodiments, the drying conditions are: temperature of 50°C to 80°C, time of 8h to 12h, so as to effectively remove moisture from the filter residue to ensure that a Prussian sodium ion positive electrode material with good regeneration performance is obtained.

In one embodiment, the filtrate obtained by filtering the solution C is recycled. It can be understood that since the filtrate obtained after filtration is a complexing agent solution, the complexing agent solution can be recycled to reduce the production cost of recycling.

The present application embodiment also provides a Prussian sodium ion positive electrode material, which is produced by the Prussian sodium ion positive electrode material recovery method described in any of the above embodiments. It can be understood that the Prussian sodium ion positive electrode material produced by the above Prussian sodium ion positive electrode material recovery method can obtain a good regeneration performance, that is, the electrical performance of the Prussian sodium ion positive electrode material sold on the market can be achieved, thereby realizing the recycling of the low-toxic [Fe(CN) ₆ ] ^4- in the discarded Prussian sodium battery, avoiding the direct discard of the Prussian sodium ion positive electrode material causing greater pressure on the environment, thereby protecting the ecological balance.

Some specific examples are given below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

The abandoned Prussian sodium-ion battery is disassembled to separate the positive electrode material, the negative electrode material and the separator to obtain the positive electrode material; the positive electrode material is washed or soaked with a 0.05 mol/L dilute HCl solution to obtain a solution A with a pH of 6; the solution A is detected with an ICP inductively coupled plasma spectrometer, and potassium ferrocyanide, _MnCl2 and _NaCl2 are sequentially added to the solution A to make the concentration of [Fe(CN)6] ^4- in the solution B reach 0.3 mol/L, the concentration of Mn2 ⁺ reach 0.4 mol/L, and the concentration of Na ⁺ reach 0.3 mol/L, to obtain a solution B;

Water is added to the reactor to preheat it to 40° C. Solution B and 0.4 mol/L maleic acid solution are introduced into the reactor for a mixed reaction, wherein the conditions for the mixed reaction are to control the flow ratio of solution B and the complexing agent solution to be 1:1 and the pH of the mixed reaction to be 6.5 under an inert atmosphere, the solution C is aged for 8 hours, and then the solution C is filtered to obtain a filter residue and a filtrate; the filtrate obtained by filtering the solution C is recycled, and the filter residue is dried at a temperature of 80° C. for 8 hours to obtain a Prussian sodium ion positive electrode material.

Example 2

The discarded Prussian sodium ion battery is disassembled to separate the positive electrode material, the negative electrode material and the separator to obtain the positive electrode material; the positive electrode material is cleaned or soaked with a 0.30 mol/L H ₂ CO ₃ solution; A solution A with a pH of 5 is obtained; an ICP inductively coupled plasma spectrometer is used to detect the solution A, and sodium ferrocyanide, FeSO ₄ and NaSO ₂ are sequentially added to the solution A to make the concentration of [Fe(CN)6] ^4- in the solution B reach 0.45 mol/L, the concentration of Fe ²⁺ reach 1.2 mol/L, and the concentration of Na ⁺ reach 0.45 mol/L, thereby obtaining a solution B;

Water is added to the reactor to preheat to 45°C, and solution B and 7.7 mol/LEDTA solution are introduced into the reactor for mixed reaction, wherein the mixed reaction conditions are to control the flow ratio of solution B and complexing agent solution to be 1:1 and the pH of the mixed reaction to be 8 under inert atmosphere conditions, and the solution C is aged for 9 hours, and then the solution C is filtered to obtain filter residue and filtrate; the filtrate obtained by filtering the solution C is recycled, and the filter residue is dried at a temperature of 65°C for 10 hours to obtain a Prussian sodium ion positive electrode material. In addition, the produced Prussian sodium ion positive electrode material has good regeneration performance, meets market requirements, and can be directly put into production, thereby reducing the production cost of Prussian sodium ion batteries.

Example 3

Dismantle discarded Prussian sodium-ion batteries to separate positive electrode materials, negative electrode materials and separators to obtain positive electrode materials; use 0.5 mol/L dilute sulfuric acid solution to wash or soak the positive electrode materials to obtain solution A with a pH of 3; use an ICP inductively coupled plasma spectrometer to detect solution A, and add sodium ferrocyanide, _NiCl2 and _NaCl2 to solution A in sequence to make the concentration of [Fe(CN)6] ^4- in solution B reach 0.6 mol/L, the concentration of Ni2 ⁺ reach 2 mol/L, and the concentration of Na ⁺ reach 0.6 mol/L, thereby obtaining solution B;

Water is added to the reactor to preheat it to 50° C. Solution B and 15 mol/L sodium citrate solution are introduced into the reactor for a mixed reaction, wherein the conditions for the mixed reaction are to control the flow ratio of solution B and the complexing agent solution to be 1:1 and the pH of the mixed reaction to be 9.5 under an inert atmosphere, the solution C is aged for 10 hours, and then the solution C is filtered to obtain a filter residue and a filtrate; the filtrate obtained by filtering the solution C is recycled, and the filter residue is dried at a temperature of 50° C. for 12 hours to obtain a Prussian sodium ion positive electrode material.

Example 4

The abandoned Prussian sodium-ion battery is disassembled to separate the positive electrode material, the negative electrode material and the separator to obtain the positive electrode material; the positive electrode material is washed or soaked with a 0.05 mol/L dilute HCl solution to obtain a solution A with a pH of 6; the solution A is detected with an ICP inductively coupled plasma spectrometer, and potassium ferrocyanide, MnCl ₂ and NaCl ₂ are added to the solution A in sequence to reduce the [Fe(CN) 6] The concentration of ^4- reaches 0.3 mol/L, the concentration of Mn ²⁺ reaches 0.4 mol/L, and the concentration of Na ⁺ reaches 0.3 mol/L, and solution B is obtained;

Water is added to the reactor to preheat it to 40°C, and solution B, 0.4 mol/L maleic acid solution, 0.4 mol/L EDTA and 0.4 mol/L sodium citrate are introduced into the reactor for mixed reaction, wherein the mass ratio of maleic acid solution, EDTA and sodium citrate is 1:0.5:1, and the conditions for the mixed reaction are to control the flow ratio of solution B and complexing agent solution to be 1:1 and the pH of the mixed reaction to be 6.5 under inert atmosphere conditions, and the solution C is aged for 8 hours, and then the solution C is filtered to obtain a filter residue and a filtrate; the filtrate obtained by filtering the solution C is recycled, and the filter residue is dried at a temperature of 80°C for 8 hours to obtain a Prussian sodium ion positive electrode material.

Comparative Example 1

The difference from Example 1 is that the order of adding potassium ferrocyanide, MnCl ₂ and NaCl ₂ to solution A is different, that is, in Comparative Example 1, MnCl ₂ , potassium ferrocyanide and NaCl ₂ are added to solution A in sequence. The other conditions are the same as in Example 1.

Comparative Example 2

The difference from Example 1 is that the pH of solution A is 1.5, and the other conditions are the same as those in Example 1.

Test items

The Prussian sodium ion positive electrode materials obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were made into sodium ion batteries, and commercially available manganese-based Prussian sodium ion batteries were purchased as standard reference values. Examples 1 to 4, Comparative Examples 1, Comparative Example 2 and commercially available manganese-based Prussian sodium ion batteries were tested, and the test data shown in the following table were obtained:

Among them, D10, D50, and D90 represent the particle size parameters of the Prussian sodium ion positive electrode material, which means that 10%, 50%, and 90% of the particle sizes are within the measured size values;

BET represents the total surface area of particles per unit volume or unit mass.

TD stands for tap density.

It can be seen from the above table that the physical and chemical test results of Examples 1 to 4 are significantly better than those of Comparative Examples 1 and 2, especially the physical and chemical test results of Example 4 are the best.

From the comparison between Examples 1 and 4 and Comparative Example 1, it can be seen that since the order of adjusting the transition metal ions, ferrocyanate and sodium ions in Solution A is different between Comparative Example 1 and Examples 1 and 4, manganese salt is first added to Solution A in Comparative Example 1. Since the concentration of sodium ferrocyanide in Solution A is low, it tends to form Mn ₂ [Fe(CN) ₆ ] with lower solubility, resulting in a decrease in the concentration of sodium ferrocyanide and manganese salt in Solution B, thereby affecting the specific capacity of the Prussian sodium ion positive electrode material.

From the comparison between Examples 1 and 4 and Comparative Example 2, it can be seen that since Comparative Example 2 uses lower pH conditions, [Fe(CN) ₆ ] ^4- decomposes, thereby reducing the concentration of [Fe(CN) ₆ ] ^4- in solution B, resulting in more vacancy defects in the final generated Prussian sodium ion positive electrode material, resulting in a decrease in specific capacity.

In order to better understand the technical solutions and beneficial effects of the present application, the present application is further described in detail below in conjunction with specific embodiments:

The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as a suppression of the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

A method for recovering a Prussian sodium ion cathode material comprises the following steps:

obtaining a positive electrode material;

The positive electrode material is cleaned or soaked with an acidic solution to obtain a solution A;

Adjusting the concentrations of transition metal ions, ferrocyanate and sodium ions in the solution A to preset concentrations to obtain a solution B;

The solution B and the complexing agent solution are mixed to react to obtain a solution C;

Filtering the solution C to obtain a filter residue;

The filter residue is dried to obtain a Prussian sodium ion positive electrode material.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the acidic solution is a non-oxidizing acid solution.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the pH of the solution A is 3 to 6.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the complexing agent solution comprises at least one of maleic acid, citric acid, citric acid, EDTA, sodium citrate and ammonia water.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the concentration of the complexing agent solution is 0.4 mol/L to 15 mol/L.
The method for recovering Prussian sodium ion cathode materials according to claim 1, wherein the preset concentration of the transition metal ions is 0.4 mol/L to 2 mol/L; and

The preset concentration of ferrocyanate is 0.3 mol/L to 0.6 mol/L; and

The preset concentration of the sodium ions is 0.3 mol/L to 0.6 mol/L.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the mixing reaction is carried out under a pH of 6.5 to 9.5 and an inert atmosphere.
The method for recovering Prussian sodium ion positive electrode materials according to claim 1, wherein the drying conditions are: temperature of 50°C to 80°C and time of 8h to 12h.
The method for recovering a Prussian sodium ion positive electrode material according to claim 1, wherein the filtrate obtained by filtering the solution C is recycled.
A Prussian sodium ion positive electrode material produced by the Prussian sodium ion positive electrode material recovery method described in any one of claims 1 to 9.