Prussian sodium-ion cathode material and recovery method thereof

Abstract

The application provides a prussian-type sodium-ion positive electrode material and a recycling method thereof. The application provides a prussian-type sodium-ion positive electrode material recycling method, which comprises the following steps: obtaining a positive electrode material; cleaning or soaking the positive electrode material with an acidic solution, adjusting the concentrations of transition metal ions, ferrocyanide ions and sodium ions in the solution A to a preset concentration, adding a complexing agent solution to the solution B and mixing for a reaction; filtering the solution C to obtain a filter residue; and drying the filter residue to obtain the prussian-type sodium-ion positive electrode material. The prussian-type sodium-ion positive electrode material recycling method can recycle low-toxicity [Fe(CN)6] 4‑ from discarded prussian-type sodium batteries, avoids the great pressure on the environment caused by directly discarding the prussian-type sodium-ion positive electrode material, thereby protecting the ecological balance, and the regenerated prussian-type sodium-ion positive electrode material produced has good regeneration performance and meets the requirements of the market.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of batteries, in particular to a Prussian-type sodium-ion positive electrode material and a recycling method thereof. BACKGROUND

[0002] The Prussian-type sodium-ion positive electrode material is a kind of sodium-ion battery positive electrode material with an open framework structure. It belongs to a metal-organic framework structure, metal and ferricyanide in the crystal lattice are arranged in the form of Fe-C=N-M to form a three-dimensional structural framework, Fe ions and metal M ions are arranged in the form of a cube, and C=N roots are located on the edges of the cube. This kind of material belongs to a cubic system, the particle size is about 20-50 nm, and it has three-dimensional sodium-ion intercalation and deintercalation channels.

[0003] Its advantages mainly include the following three points: (1) the rigid framework structure and the open macropore and site ensure that sodium ions with a large ion radius can be reversibly intercalated and deintercalated without changing the material structure; (2) because of the double-electron redox reaction, the theoretical capacity of the Prussian-type sodium-ion positive electrode material is as high as 170 mAhg-1; (3) the simple synthesis process, low toxicity and low cost make the material suitable for large-scale production; (4) the Prussian-type sodium-ion positive electrode material has a clear cost advantage over lithium battery materials and even other sodium-ion battery positive electrode materials. Therefore, the Prussian-type positive electrode material gradually moves towards industrialization, so that the Prussian-type sodium-ion battery also moves towards industrialization.

[0004] However, a large amount of waste Prussian-type sodium-ion positive electrode material will be produced in the industrialization of the Prussian-type sodium-ion battery, and the Prussian-type sodium-ion positive electrode material contains low-toxicity [Fe(CN)6] 4- , and if it is directly discarded, it will cause great pressure on the environment and destroy the ecological balance. Therefore, how to deal with the waste Prussian-type sodium-ion positive electrode material is a problem to be solved. SUMMARY

[0005] The purpose of the application is to overcome the deficiencies in the prior art, provide a Prussian-type sodium-ion positive electrode material with improved ferrocyanate recovery rate to reduce the pressure on the environment, and a recycling method thereof with good regeneration performance.

[0006] The purpose of the application is achieved by the following technical scheme:

[0007] A Prussian-type sodium-ion positive electrode material recycling method, comprising the following steps:

[0008] obtaining a positive electrode material;

[0009] cleaning or soaking the positive electrode material with an acidic solution to obtain a solution A;

[0010] Adjust the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A to a preset concentration to obtain solution B;

[0011] Solution B is mixed with a complexing agent solution to obtain solution C.

[0012] The solution C is filtered to obtain filter residue;

[0013] The filter residue is dried to obtain a Prussian-type sodium ion cathode material.

[0014] In one embodiment, the acidic solution is a non-oxidizing acid solution.

[0015] In one embodiment, the pH of solution A is 3 to 6.

[0016] In one embodiment, the complexing agent solution includes at least one of maleic acid, citric acid, citric acid, EDTA, sodium citrate, and ammonia.

[0017] In one embodiment, the concentration of the complexing agent solution is 0.4 mol / L to 15 mol / L.

[0018] In one embodiment, the preset concentration of the transition metal ions is 0.4 mol / L to 2 mol / L; and

[0019] The preset concentration of the ferrocyanate ion is 0.3 mol / L to 0.6 mol / L; and

[0020] The preset concentration of sodium ions is 0.3 mol / L to 0.6 mol / L.

[0021] In one embodiment, the mixing reaction was carried out under conditions of pH 6.5–9.5 and an inert atmosphere.

[0022] In one embodiment, the drying conditions are: a temperature of 50°C to 80°C and a time of 8 to 12 hours.

[0023] In one embodiment, the filtrate obtained by filtering the solution C is recycled.

[0024] In one embodiment, the acidic solution is an inorganic acid that does not react with the filtered metal.

[0025] A Prussian-type sodium-ion cathode material is produced using the Prussian-type sodium-ion cathode material recycling method described in any of the above embodiments.

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] The above-described method for recovering Prussian-type sodium-ion cathode materials involves washing or soaking the cathode material in an acidic solution. This allows the active substances on the cathode material to dissolve in the acidic solution, resulting in solution A. Solution A is formed by the free release of acid-soluble substances such as transition metal ions, sodium ions, and ferrocyanide ions from the cathode material in the acidic solution. The concentrations of transition metal ions, ferrocyanide ions, and sodium ions in solution A are then adjusted to preset concentrations. Next, solution B and a complexing agent solution are mixed and reacted to allow ferrocyanide ions to precipitate with the transition metal ions and sodium ions, generating Prussian-type crystals. Finally, solution C is filtered, and the filter residue is dried to obtain Prussian-type sodium-ion cathode materials with good recyclability. Using this recovery method, the low-toxicity [Fe(CN)6] in discarded Prussian-type sodium batteries can be recovered. 4- Recycling avoids the significant environmental impact of directly discarding Prussian-type sodium-ion cathode materials, thus protecting the ecological balance. Furthermore, the produced Prussian-type sodium-ion cathode materials exhibit good regenerability, meet market requirements, and can be directly used in production, thereby reducing the production cost of Prussian-type sodium-ion batteries. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a flowchart of a method for recovering Prussian-type sodium-ion cathode materials according to an embodiment of the present invention;

[0030] Figure 2 SEM image of a Prussian-type sodium-ion cathode material product according to an embodiment of the present invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] This application provides a method for recovering Prussian-type sodium-ion cathode materials, comprising the following steps: obtaining cathode material; washing or soaking the cathode material with an acidic solution to obtain solution A; adjusting the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A to a preset concentration to obtain solution B; adding a complexing agent solution to solution B for mixing and reaction to obtain solution C; filtering solution C to obtain filter residue; and drying the filter residue to obtain Prussian-type sodium-ion cathode material.

[0035] The above-described method for recovering Prussian-type sodium-ion cathode materials involves washing or soaking the cathode material in an acidic solution. This allows the active substances on the cathode material to dissolve in the acidic solution, resulting in solution A. Solution A is formed by the free release of acid-soluble substances such as transition metal ions, sodium ions, and ferrocyanide ions from the cathode material in the acidic solution. The concentrations of transition metal ions, ferrocyanide ions, and sodium ions in solution A are then adjusted to preset concentrations. Next, solution B and a complexing agent solution are mixed and reacted to allow ferrocyanide ions to precipitate with the transition metal ions and sodium ions, generating Prussian-type crystals. Finally, solution C is filtered, and the filter residue is dried to obtain Prussian-type sodium-ion cathode materials with good recyclability. Using this recovery method, the low-toxicity [Fe(CN)6] in discarded Prussian-type sodium batteries can be recovered. 4- Recycling avoids the significant environmental impact of directly discarding Prussian-type sodium-ion cathode materials, thus protecting the ecological balance. Furthermore, the produced Prussian-type sodium-ion cathode materials exhibit good regenerability, meet market requirements, and can be directly used in production, thereby reducing the production cost of Prussian-type sodium-ion batteries.

[0036] Please see Figure 1To better understand the technical solution and beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments. One embodiment of the Prussian-type sodium ion cathode material recovery method includes some or all of the following steps:

[0037] S110. Obtain the positive electrode material. The positive electrode material can be obtained from the waste Prussian sodium-ion battery for later use.

[0038] S120. The positive electrode material is cleaned or soaked in an acidic solution to obtain solution A. It is understood that since the positive electrode material obtained from discarded Prussian sodium-ion batteries includes aluminum foil and active material, cleaning or soaking the positive electrode material in an acidic solution allows the active material to dissolve. This releases acid-soluble substances such as transition metal ions, sodium ions, and ferrocyanate ions from the active material into solution A, thereby separating the aluminum foil from the active material for better subsequent collection.

[0039] S130. Adjust the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A to a preset concentration so that the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A meet the requirements for regeneration, and obtain solution B for later use.

[0040] S140. The solution B and the complexing agent solution are mixed and reacted to obtain solution C.

[0041] It should be noted that, due to the very rapid reaction between ferrous ions and ferrocyanide ions during the formation of Prussian-type crystals, the final Prussian-type sodium-ion battery cathode material often contains a large number of ferrocyanide vacancy defects and water of crystallization. The presence of ferrocyanide vacancy defects reduces the structural stability of the Prussian-type sodium-ion battery cathode material, and repeated sodium ion intercalation and deintercalation may lead to structural collapse. Simultaneously, water of crystallization occupies the sites of ferrocyanide vacancy defects or interstitial positions in the crystal structure, thus hindering the transport of sodium ions within the crystal structure and consequently reducing the conductivity of the Prussian-type sodium-ion battery. Therefore, this application involves mixing solution B and the complexing agent solution to effectively suppress the reaction rate between transition metal ions and ferrocyanide ions, thereby effectively avoiding the phenomenon of excessively rapid reaction between transition metal ions and ferrocyanide ions leading to severe vacancy defects in the formation of Prussian-type crystals. This results in a Prussian-type sodium-ion cathode material with good regeneration performance. Figure 2 As shown, the regenerated Prussian-type sodium ion cathode material has a good morphology and meets the requirements for market sales.

[0042] S150. The solution C is filtered to obtain filter residue, thereby achieving the separation of Prussian-type precipitates from the liquid.

[0043] S160. The filter residue is dried to effectively remove the water of crystallization in the Prussian precipitate to obtain a Prussian sodium-ion cathode material. The obtained Prussian sodium-ion cathode material has good regeneration performance and can be directly put into production, thereby effectively reducing the production cost of Prussian sodium-ion batteries.

[0044] The above-described method for recovering Prussian-type sodium-ion cathode materials involves washing or soaking the cathode material in an acidic solution. This allows the active substances on the cathode material to dissolve in the acidic solution, resulting in solution A. Solution A is formed by the free release of acid-soluble substances such as transition metal ions, sodium ions, and ferrocyanide ions from the cathode material in the acidic solution. The concentrations of transition metal ions, ferrocyanide ions, and sodium ions in solution A are then adjusted to preset concentrations. Next, solution B and a complexing agent solution are mixed and reacted to allow ferrocyanide ions to precipitate with the transition metal ions and sodium ions, generating Prussian-type crystals. Finally, solution C is filtered, and the filter residue is dried to obtain Prussian-type sodium-ion cathode materials with good recyclability. Using this recovery method, the low-toxicity [Fe(CN)6] in discarded Prussian-type sodium batteries can be recovered. 4- Recycling avoids the significant environmental impact of directly discarding Prussian-type sodium-ion cathode materials, thus protecting the ecological balance.

[0045] Further, please refer to Figure 2 Using the above-mentioned recycling method, the Prussian-type sodium-ion cathode material produced 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.

[0046] In one embodiment, the acidic solution is a non-oxidizing acid solution. It is understood that the cathode material obtained from discarded Prussian sodium-ion batteries contains a large amount of ferrocyanide ions. Ferrocyanide ions readily convert to ferricyanide ions under oxidizing agents. Furthermore, ferricyanide ions are more prone to hydration than ferrocyanide ions to produce toxic hydrogen cyanide, posing a significant hazard to human health. Therefore, the acidic solution in this application is a non-oxidizing acid. This ensures that the transition metal ions, sodium ions, and ferrocyanide ions on the active material are freed in the non-oxidizing acid to form solution A. Simultaneously, the added non-oxidizing acid effectively inhibits the oxidation of ferrocyanide ions to ferricyanide ions, thereby improving the recovery rate of ferrocyanide ions. It also avoids the formation of highly toxic ferricyanide ions, ensuring the safety of the Prussian sodium-ion cathode material during the recycling process and reducing the harm of toxic hydrogen cyanide to human health and the environment.

[0047] It should be noted that, compared to traditional sodium-ion or lithium-ion battery recycling methods, most employ high-temperature calcination to quickly separate the active material from the aluminum foil. However, for the Prussian-type sodium-ion battery recycling described in this application, the positive electrode material obtained from dismantling waste Prussian-type sodium-ion batteries contains a large amount of ferrocyanide. Furthermore, ferrocyanide readily decomposes into N2 under high-temperature conditions, thus damaging the structure of the ferrocyanide and resulting in a low recovery rate. Consequently, the maximum efficiency of the Prussian-type sodium-ion battery cannot be achieved. Therefore, by employing a non-oxidizing acid, this invention ensures that ferrocyanide is not easily decomposed under non-oxidizing acid conditions, thus maximizing the preservation of its structure and improving its recovery rate. Furthermore, the added non-oxidizing acid effectively inhibits the oxidation of ferrocyanide to ferricyanide, further enhancing the recovery rate. Simultaneously, it avoids the generation of highly toxic ferricyanide, ensuring the safety of Prussian sodium-ion cathode materials during the recycling process and reducing the harm of toxic hydrogen cyanide to humans and the environment.

[0048] In one embodiment, the non-oxidizing acid solution includes at least one selected from dilute HCl solution, H₂CO₃ solution, dilute sulfuric acid solution, and phosphoric acid solution. It is understood that a non-oxidizing acid solution refers to a solution that ionizes into H₂ when dissolved in water. + A type of acid solution with weak oxidizing properties is used to effectively prevent the decomposition of ferrocyanide and thus improve the recovery rate of ferrocyanide.

[0049] Furthermore, in one embodiment, the pH of solution A is 3-6. It is understood that since ferrocyanide is easily oxidized to ferricyanide under strongly acidic conditions, this application uses a non-oxidizing acid to directly dissolve the active material and controls the pH of solution A to 3-6. This provides mild conditions for ferrocyanide, better preventing its oxidative decomposition, thus ensuring the recovery rate of ferrocyanide, avoiding the formation of ferricyanide, and thereby maximizing the benefits of recycling waste Prussian sodium-ion batteries. This reduces harm to the environment and human health, and improves the safety of the recycling process.

[0050] In one embodiment, the concentration of the non-oxidizing acid solution is 0.05 mol / L to 0.5 mol / L. It is understood that if the concentration is below 0.05 mol / L, it is difficult to ensure that the non-oxidizing acid solution can completely dissolve the active material from the aluminum foil, resulting in a low recovery rate of ferrocyanide. If the concentration of the non-oxidizing acid solution is above 0.5 mol / L, ferrocyanide is prone to decomposition. Therefore, this application controls the concentration of the non-oxidizing acid solution to 0.05 mol / L to 0.5 mol / L. This ensures that the added non-oxidizing acid solution can not only completely dissolve the active material on the aluminum foil but also avoids the easy oxidation of ferrocyanide into highly toxic ferricyanide. Thus, it not only improves the recovery rate of ferrocyanide but also ensures the safety of the recovery process.

[0051] In one embodiment, prior to obtaining the positive electrode material, the method further includes the following step: disassembling a discarded Prussian sodium-ion battery to separate the positive electrode material, the negative electrode material, and the separator, thereby obtaining the positive electrode material.

[0052] In one embodiment, the step of cleaning or soaking the positive electrode material with an acidic solution includes the following specific steps: scraping the active material on the aluminum foil into a non-oxidizing acid solution to obtain a mixture, so as to quickly separate the aluminum foil from the active material and thus improve production efficiency; cleaning or soaking the positive electrode material with the mixture to completely dissolve the active material remaining on the aluminum foil, so as to achieve complete recovery of ferrocyanide in the positive electrode material and thus improve the recovery rate of ferrocyanide.

[0053] In one embodiment, before the step of adjusting the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A to a preset concentration, and after the step of cleaning or soaking the positive electrode material with an acidic solution, the following step is further included: detecting the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A.

[0054] It is understandable that using an ICP (Inductively Coupled Plasma Emission Spectrometer) to detect the concentrations of transition metal ions, ferrocyanide, and sodium ions in solution A allows for rapid determination of their actual concentrations. This enables subsequent adjustments to ensure these concentrations meet the requirements for preparing regenerated Prussian-type sodium-ion cathode materials. Notably, because the ICP has multiple detection units, each capable of detecting the concentration of a single element, it allows for rapid detection of transition metal ions, ferrocyanide, and sodium ions in solution A, thereby improving recovery efficiency.

[0055] In one embodiment, the complexing agent solution includes at least one of maleic acid, citric acid, citric acid, EDTA, sodium citrate, and ammonia.

[0056] In one embodiment, the complexing agent solution is a mixture of maleic acid, EDTA and sodium citrate. It is understandable that the added maleic acid, due to its good scale inhibition properties and ability to adsorb impurities, along with its excellent colloidal characteristics and dispersing effect, not only improves the dispersibility of the complexing agent, ensuring the preparation of uniform Prussian-type crystals with fewer impurities, but also, in conjunction with the use of EDTA and sodium citrate, effectively enhances the complexing ability, complexing capacity, and biodegradability of the complexing agent. This results in a complexing agent with high complexing capacity, strong complexing ability, and good biodegradability. Thus, the addition of the compounded complexing agent benefits the dispersion of the complexing agent in solution B, thereby facilitating the formation of uniform Prussian-type crystals with fewer impurities, reducing vacancy defects and water of crystallization content in the Prussian-type crystals, and obtaining Prussian-type sodium-ion cathode materials with excellent electrochemical performance. On the other hand, it helps improve the biodegradability of the complexing agent, reducing environmental impact, and also ensures a high complexing capacity to improve the recovery rate of ferrocyanide and a more stable complexing ability, thus ensuring a structurally stable Prussian-type crystal. It is worth mentioning that the added sodium citrate can also provide sodium ions, providing a sufficient sodium source for Prussian crystals, thereby ensuring that ferrocyanide, transition metal ions and sodium ions can react fully and completely, so as to improve the recovery rate of ferrocyanide.

[0057] 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 using a compound of 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.

[0058] In one embodiment, the concentration of the complexing agent solution is 0.4 mol / L to 15 mol / L to ensure that the complexing agent can better control the reaction rate between ferrocyanide and transition metal ions, so as to effectively slow down the rate of Prussian crystal formation, reduce the vacancy defects and water of crystallization content of Prussian crystals, and obtain Prussian sodium ion cathode material with excellent electrochemical performance.

[0059] In one embodiment, the step of adjusting the concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A to a preset concentration includes the following specific steps: first adjusting the concentration of ferrocyanate ions, then adjusting the concentration of transition metal ions, and finally adjusting the concentration of sodium ions.

[0060] It is understandable that if the concentration of transition metal ions is adjusted first, then the concentration of ferrocyanate is adjusted, and finally the concentration of sodium ions is adjusted, then the added sufficient transition metal ions can quickly react with ferrocyanate to generate Prussian-type crystals with more vacancy defects, which is not conducive to the formation of Prussian-type crystals. Therefore, this application first adjusts the concentration of ferrocyanide in solution A to increase the concentration of ferrocyanide in solution A, thereby reducing the vacancy defects in the formation of Prussian-type crystals. That is, it ensures that under the condition of a higher concentration of ferrocyanide, there are fewer vacancy defects in the formation of ferrocyanide in Prussian-type crystals, which is conducive to the formation of Prussian-type crystals with fewer vacancy defects. Then, the concentration of transition metal ions is supplemented to a preset concentration to ensure that the recovered transition metal ions can fully react with ferrocyanide. After that, the ferrocyanide reacts with the subsequently added transition metal ions. That is, the reaction between transition metal ions and ferrocyanide is carried out in stages, so as to better slow down the reaction rate between transition metal ions and ferrocyanide to slow down the formation of Prussian-type crystals with more severe vacancy defects. Finally, the sodium ion concentration is adjusted so that the generated Prussian-type crystals can meet the requirements of regeneration performance.

[0061] In one embodiment, a transition metal salt is used to adjust the concentration of transition metal ions to achieve a preset concentration. Specifically, in one embodiment, the preset concentration of the transition metal ions is 0.4 mol / L to 2 mol / L to ensure that the transition metal ions in solution B meet the production requirements for regenerated Prussian sodium-ion cathode materials.

[0062] In one embodiment, ferrocyanate is used to adjust the concentration of transition metal ions so that the ferrocyanate concentration reaches a preset requirement. Specifically, in one embodiment, the preset concentration of ferrocyanate is 0.3 mol / L to 0.6 mol / L to ensure that the ferrocyanate concentration in solution B meets the production requirements of regenerated Prussian sodium-ion cathode material.

[0063] In one embodiment, sodium salt is used to adjust the concentration of transition metal ions 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 ion concentration in solution B meets the production requirements for regenerated Prussian-type sodium ion cathode materials.

[0064] In one embodiment, the transition metal salt includes at least one of divalent Mn salt, divalent Fe salt, divalent Co salt, divalent Ni salt, divalent Cu salt, and divalent Zn salt, to achieve adjustment of the transition metal concentration.

[0065] In one embodiment, the divalent Mn salt includes at least one of MnCl2 and MnSO4.

[0066] In one embodiment, the divalent Fe salt includes at least one of FeCl2 and FeSO4.

[0067] In one embodiment, the divalent Co salt includes at least one of CoCl2 and CoSO4.

[0068] In one embodiment, the divalent Ni salt includes at least one of NiCl2 and NiSO4.

[0069] In one embodiment, the divalent Cu salt includes at least one of CuCl2 and CuSO4.

[0070] In one embodiment, the divalent Zn salt includes at least one of ZnCl2 and ZnSO4.

[0071] In one embodiment, the ferrocyanate comprises at least one of potassium ferrocyanide and sodium ferrocyanide.

[0072] In one embodiment, the sodium salt includes at least one of NaCl2 and NaSO4.

[0073] In one embodiment, the step of mixing solution B and the complexing agent solution includes the following specific steps: adding water to the reaction vessel for preheating, and then introducing solution B and the complexing agent solution into the reaction vessel for mixing to achieve the mixing reaction of solution B and the complexing agent solution. Specifically, in one embodiment, the mixing reaction is carried out under pH 6.5–9.5 and an inert atmosphere to ensure the normal progress of the reaction between solution B and the complexing agent solution. Further, in one embodiment, the flow rate ratio of solution B to the complexing agent solution is 1:1 to ensure that the complexing agent solution can be better and more uniformly mixed with solution B, thereby more effectively suppressing the rate of Prussian crystal formation to obtain Prussian crystals with fewer vacancy defects. Further, the preheating temperature is 40°C–50°C.

[0074] In one embodiment, prior to the step of filtering the solution C, the following step is further included: aging the solution C. It is understood that aging the solution C promotes the formation of Prussian-type crystals, thereby avoiding the formation of Prussian-type crystals with numerous vacancy defects. Further, in one embodiment, the aging time is 8 to 10 hours.

[0075] In one embodiment, the drying conditions are: a temperature of 50°C to 80°C and a time of 8 to 12 hours, to effectively remove moisture from the filter residue and ensure that a Prussian-type sodium-ion cathode material with good regeneration performance is obtained.

[0076] In one embodiment, the filtrate obtained by filtering the solution C is recycled. It is understood that since the filtrate obtained after filtration is a complexing agent solution, this allows for the recycling of the complexing agent solution, thereby reducing the production costs associated with recycling.

[0077] This application also provides a Prussian-type sodium-ion cathode material, produced using the Prussian-type sodium-ion cathode material recycling method described in any of the above embodiments. It is understood that the Prussian-type sodium-ion cathode material produced by the above-described Prussian-type sodium-ion cathode material recycling method exhibits good regeneration performance, achieving electrical performance comparable to commercially available Prussian-type sodium-ion cathode materials, thereby realizing low-toxicity [Fe(CN)6] in discarded Prussian-type sodium batteries. 4- Recycling avoids the significant environmental impact of directly discarding Prussian-type sodium-ion cathode materials, thus protecting the ecological balance.

[0078] Compared with the prior art, the present invention has at least the following advantages:

[0079] The above-described method for recovering Prussian-type sodium-ion cathode materials involves washing or soaking the cathode material in an acidic solution. This allows the active substances on the cathode material to dissolve in the acidic solution, resulting in solution A. Solution A is formed by the free release of acid-soluble substances such as transition metal ions, sodium ions, and ferrocyanide ions from the cathode material in the acidic solution. The concentrations of transition metal ions, ferrocyanide ions, and sodium ions in solution A are then adjusted to preset concentrations. Next, solution B and a complexing agent solution are mixed and reacted to allow ferrocyanide ions to precipitate with the transition metal ions and sodium ions, generating Prussian-type crystals. Finally, solution C is filtered, and the filter residue is dried to obtain Prussian-type sodium-ion cathode materials with good recyclability. Using this recovery method, the low-toxicity [Fe(CN)6] in discarded Prussian-type sodium batteries can be recovered. 4- Recycling avoids the significant environmental impact of directly discarding Prussian-type sodium-ion cathode materials, thus protecting the ecological balance.

[0080] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the examples are commercially available.

[0081] Example 1

[0082] Discarded Prussian sodium-ion batteries were disassembled to separate the positive electrode material, negative electrode material, and separator, yielding the positive electrode material. The positive electrode material was then cleaned or soaked in a 0.05 mol / L dilute HCl solution to obtain solution A with a pH of 6. Solution A was analyzed using an ICP-based inductively coupled plasma optical emission spectrometer. Potassium ferrocyanide, MnCl2, and NaCl2 were added sequentially to solution A to adjust the concentration of [Fe(CN)6] in solution B. 4- The concentration reached 0.3 mol / L, Mn 2+ The concentration reached 0.4 mol / L, Na + The concentration reached 0.3 mol / L, resulting in solution B;

[0083] Water was added to the reactor and preheated to 40°C. Solution B and 0.4 mol / L maleic acid solution were then introduced into the reactor for mixing. The mixing reaction was carried out under inert atmosphere conditions, with the flow ratio of solution B to complexing agent solution controlled at 1:1 and the pH of the mixing reaction at 6.5. Solution C was aged for 8 hours and then filtered to obtain filter residue and filtrate. The filtrate obtained from filtering solution C was recycled, and the filter residue was dried at 80°C for 8 hours to obtain Prussian sodium ion cathode material.

[0084] Example 2

[0085] Discarded Prussian sodium-ion batteries were disassembled to separate the positive electrode material, negative electrode material, and separator, yielding the positive electrode material. The positive electrode material was then cleaned or soaked in a 0.30 mol / L H₂CO₃ solution to obtain solution A with a pH of 5. Solution A was analyzed using an ICP-based inductively coupled plasma optical emission spectrometer. Sodium ferrocyanide, FeSO₄, and NaSO₂ were added sequentially to solution A to induce the [Fe(CN)₆] content in solution B. 4- The concentration reached 0.45 mol / L, Fe 2+ The concentration reached 1.2 mol / L, Na + The concentration reached 0.45 mol / L, resulting in solution B;

[0086] Water was added to the reactor and preheated to 45°C. Solution B and 7.7 mol / L LEDTA solution were then introduced into the reactor for mixing. The mixing reaction conditions were as follows: under an inert atmosphere, the flow ratio of solution B to the complexing agent solution was controlled at 1:1, and the pH of the mixture was 8. Solution C was aged for 9 hours, then filtered to obtain filter residue and filtrate. The filtrate obtained from filtering solution C was recycled, and the filter residue was dried at 65°C for 10 hours to obtain Prussian sodium-ion cathode material. Furthermore, the produced Prussian sodium-ion cathode material exhibits good regeneration performance, meets market requirements, and can be directly used in production, thereby reducing the production cost of Prussian sodium-ion batteries.

[0087] Example 3

[0088] Discarded Prussian sodium-ion batteries were disassembled to separate the positive electrode material, negative electrode material, and separator, yielding the positive electrode material. The positive electrode material was then cleaned or soaked in a 0.5 mol / L dilute sulfuric acid solution to obtain solution A with a pH of 3. Solution A was analyzed using an ICP-based inductively coupled plasma optical emission spectrometer. Sodium ferrocyanide, NiCl2, and NaCl2 were added sequentially to solution A to adjust the concentration of [Fe(CN)6] in solution B. 4- The concentration reached 0.6 mol / L, Ni 2+ The concentration reached 2 mol / L, Na + The concentration reached 0.6 mol / L, resulting in solution B;

[0089] Water was added to the reactor and preheated to 50°C. Solution B and 15 mol / L sodium citrate solution were then introduced into the reactor for mixing. The mixing reaction was carried out under an inert atmosphere with a flow ratio of 1:1 between solution B and the complexing agent solution and a pH of 9.5. Solution C was aged for 10 hours and then filtered to obtain filter residue and filtrate. The filtrate obtained from filtering solution C was recycled, and the filter residue was dried at 50°C for 12 hours to obtain Prussian sodium ion cathode material.

[0090] Example 4

[0091] Discarded Prussian sodium-ion batteries were disassembled to separate the positive electrode material, negative electrode material, and separator, yielding the positive electrode material. The positive electrode material was then cleaned or soaked in a 0.05 mol / L dilute HCl solution to obtain solution A with a pH of 6. Solution A was analyzed using an ICP-based inductively coupled plasma optical emission spectrometer. Potassium ferrocyanide, MnCl2, and NaCl2 were added sequentially to solution A to adjust the concentration of [Fe(CN)6] in solution B. 4- The concentration reached 0.3 mol / L, Mn 2+ The concentration reached 0.4 mol / L, Na + The concentration reached 0.3 mol / L, resulting in solution B;

[0092] Water was added to the reactor and preheated to 40°C. Solution B, 0.4 mol / L maleic acid solution, 0.4 mol / L EDTA, and 0.4 mol / L sodium citrate were introduced into the reactor for mixing and reaction. The mass ratio of maleic acid solution, EDTA, and sodium citrate was 1:0.5:1. The mixing reaction conditions were as follows: the flow ratio of solution B to complexing agent solution was controlled at 1:1 under an inert atmosphere, and the pH of the mixing reaction was 6.5. Solution C was aged for 8 hours, and then filtered to obtain filter residue and filtrate. The filtrate obtained from filtering solution C was recycled, and the filter residue was dried at 80°C for 8 hours to obtain Prussian sodium ion cathode material.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that the order in which potassium ferrocyanide, MnCl2, and NaCl2 are added to solution A is different; that is, in Comparative Example 1, MnCl2, potassium ferrocyanide, and NaCl2 are added to solution A in sequence. 2. The remaining conditions are the same as in Example 1.

[0095] Comparative Example 2

[0096] The difference from Example 1 is that the pH of solution A is 1.5, while the other conditions are the same as in Example 1.

[0097] Test Project

[0098] Sodium-ion batteries were fabricated using the Prussian-type sodium-ion cathode materials obtained in Examples 1-4 and Comparative Examples 1 and 2. Commercially available manganese-based Prussian sodium-ion batteries were purchased as standard references. The batteries from Examples 1-4, Comparative Examples 1 and 2, and the commercially available manganese-based Prussian sodium-ion batteries were tested, and the test data are shown in the table below:

[0099] Among them, D10, D50, and D90 represent the particle size parameters of Prussian sodium-ion cathode materials, which represent 10%, 50%, and 90% of the measured particle size values.

[0100] BET represents the total surface area of ​​particles per unit volume or unit mass.

[0101] TD represents tap density.

[0102]

[0103] As can be seen from the table above, the physicochemical test results of Examples 1 to 4 are significantly better than those of Comparative Examples 1 and 2, especially the physicochemical test results of Example 4 are the best.

[0104] As can be seen from the comparison between Examples 1 and 4 and Comparative Example 1, the order in which the transition metal ions, ferrocyanide ions, and sodium ions in solution A are adjusted in Comparative Example 1 and Examples 1 and 4 are different. In Comparative Example 1, manganese salt is added to solution A first. Because the concentration of sodium ferrocyanide in solution A is low, it tends to form Mn2[Fe(CN)6], which has lower solubility. This leads to a decrease in the concentration of sodium ferrocyanide and manganese salt in solution B, thereby affecting the specific capacity of Prussian sodium ion cathode materials.

[0105] A comparison of Examples 1 and 4 with Comparative Example 2 shows that, due to the use of lower pH conditions in Comparative Example 2, [Fe(CN)6]... 4- Decomposition, thereby reducing the concentration of [Fe(CN)6] in solution B. 4- The concentration of certain substances leads to more vacancy defects in the final Prussian-type sodium ion cathode material, resulting in a decrease in specific capacity.

[0106] To better understand the technical solution and beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments:

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for recovering Prussian-type sodium-ion cathode materials, characterized in that, Includes the following steps: Obtain the cathode material; The positive electrode material is cleaned or soaked in an acidic solution to obtain solution A; wherein the acidic solution is a non-oxidizing acid solution; and the pH of solution A is 3-6. The concentrations of transition metal ions, ferrocyanate ions, and sodium ions in solution A are adjusted to preset concentrations to obtain solution B; wherein, the concentration of ferrocyanate ions is adjusted first, then the concentration of transition metal ions is adjusted, and finally the concentration of sodium ions is adjusted. The solution B and the complexing agent solution are mixed and reacted to obtain solution C; The solution C is filtered to obtain filter residue; The filter residue is dried to obtain a Prussian-type sodium ion cathode material.

2. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The complexing agent solution includes at least one of maleic acid, citric acid, EDTA, sodium citrate, and ammonia.

3. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The concentration of the complexing agent solution is 0.4 mol / L to 15 mol / L.

4. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The preset concentration of the transition metal ions is 0.4 mol / L to 2 mol / L; and The preset concentration of the ferrocyanate ion is 0.3 mol / L to 0.6 mol / L; and The preset concentration of sodium ions is 0.3 mol / L to 0.6 mol / L.

5. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The mixed reaction was carried out under pH 6.5–9.5 and an inert atmosphere.

6. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The drying conditions are: temperature 50℃~80℃, time 8h~12h.

7. The method for recovering Prussian-type sodium-ion cathode materials according to claim 1, characterized in that, The filtrate obtained by filtering the solution C is recycled.

8. A Prussian-type sodium-ion cathode material, characterized in that, It is produced using the Prussian-type sodium-ion cathode material recovery method described in any one of claims 1 to 7.

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