Recovery method and preparation method of a Prussian-type cathode material

Abstract

The present invention provides a recovery method and a preparation method for a Prussian-type cathode material. In the recovery method, the Prussian-type cathode material disassembled from a battery is dissolved in a non-oxidizing acid to obtain a clear solution, and then an oxygen source is introduced into the clear solution for an oxidation reaction. After solid-liquid separation, a transition metal hydroxy oxide and a solution containing H<subgt;4< / subgt>[Fe(CN)<subgt;6< / subgt;] and / or H<subgt;4< / subgt>[Mn(CN)<subgt;6< / subgt;] are obtained. The recovery method of the present invention can effectively separate and extract the transition metal elements in the Prussian-type material that are not coordinated with cyanide groups, and no cyanide ions or hydrocyanic acid will be generated during the process. The recovered solution can be further processed into a raw material for synthesizing the Prussian-type cathode material. The recovery method can process the Prussian-type cathode material in waste sodium batteries on a large scale, and the treatment process is non-toxic, harmless, and has a simple process. The recovery method has good economic benefits.

Description

Technical Field

[0001] The present invention belongs to the field of sodium ion batteries, and particularly relates to a recovery method and a preparation method of a Prussian-type cathode material. Background Art

[0002] Prussian blue (PB, Na x Fe[Fe(CN)6]) and its analog PBA (Na x M[Fe(CN)6], where M is selected from Ni, Co, Mn, Cu, etc.) are a large class of transition metal hexacyanoferrates. They have an open framework structure. The M and Fe elements can provide numerous redox sites and excellent structural stability, and can accommodate alkaline cations with relatively large ionic radii such as Na + and K + to be embedded / extracted. Therefore, they can be used to prepare inexpensive sodium battery cathode materials. The specific capacity of iron-based Prussian white (Na2Fe[Fe(CN)6]) can reach 160 mA·h·g -1 , while the specific capacity of high-manganese Prussian white (Na2Mn[Mn(CN)6]) can reach 209 mA·h·g -1 . Its comprehensive performance has approached that of lithium iron phosphate batteries, so it has received extensive attention and promotion. Related research on the preparation of Prussian-type materials and the construction and performance improvement of Prussian-type batteries has been carried out on a large scale.

[0003] CN111252784A discloses a preparation method of a manganese-based Prussian white cathode material, including step 1), dissolving a manganese salt containing divalent manganese ions in deionized water to form solution A; step 2), dissolving sodium ferrocyanide in deionized water to form solution B; step 3), dropping solution A into solution B for coprecipitation reaction to obtain a suspension; step 4), transferring the suspension obtained in step 3) to a reaction kettle, adding a soluble sodium salt, and after hydrothermal reaction for a certain time, filtering and drying the precipitate to obtain the manganese Prussian white cathode material. The preparation method of this invention can regulate the morphology and size distribution of the product. The prepared manganese-based Prussian white has good crystallinity. When applied to the electrode of a sodium ion battery, it can significantly improve the electrochemical performance of the sodium ion battery, especially effectively improving the charge-discharge capacity.

[0004] CN107039622A provides a preparation method of a sodium-ion battery based on a graphite / prussian blue cathode material, specifically as follows: Mix a ferrous chloride solution and a sodium ferrocyanide solution, first raise the temperature programmatically to 70-90 °C, then lower the temperature programmatically to room temperature, wash and dry to obtain prussian blue nanospheres; then add the prussian blue nanospheres to a graphene oxide solution, stir and mix, separate, cool and freeze-dry to obtain graphene oxide-coated prussian blue nanospheres, and then reduce them in hydrazine hydrate to obtain graphite / prussian blue; finally, grind, vacuum-dry and press graphite / prussian blue together with a conductive agent, isopropanol and polytetrafluoroethylene as the cathode, use a sodium metal sheet as the anode, use NaClO4 as the electrolyte, and use a chitosan membrane as the separator to assemble a sodium-ion battery based on graphite / prussian blue under an argon atmosphere. The sodium-ion battery prepared by the present invention has good stable cycle performance, and the capacity retention rate is as high as over 90%.

[0005] It can be predicted that with the large-scale application and industrialization of prussian materials, a large amount of waste prussian sodium cathode materials will inevitably be generated. Since the prussian sodium cathode materials not only contain metal elements with recycling value, but also contain low-toxicity substances [FeCN)6] 4- , how to deal with these waste cathode materials is an urgent problem to be solved. However, at present, most of the research focuses on how to prepare and optimize prussian materials, and there is no targeted technical solution for the recycling of prussian cathode materials. Moreover, the current mainstream recycling methods for ternary cathode materials in lithium-ion batteries, such as wet recycling and dry recycling, will produce a large amount of highly toxic cyanides when directly applied to prussian materials, and are not very suitable for prussian sodium cathode materials.

[0006] From the above, it can be seen that it is very necessary to develop a new technical solution suitable for recycling prussian cathode materials, which has very important practical significance for promoting the development and application of prussian cathode materials. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a recycling method and a preparation method of a prussian cathode material. The recycling method first dissolves the prussian cathode material disassembled from the battery in a non-oxidizing acid to obtain a clear solution, then introduces an oxygen source into the clear solution for an oxidation reaction, and obtains a transition metal hydroxy oxide and a solution containing H4[Fe(CN)6] and / or H4[Mn(CN)6] after solid-liquid separation. The recycling method of the present invention can effectively separate the transition metal elements in the prussian material that are not coordinated with cyanide groups from [Fe(CN)6] 4- and / or [Mn(CN)6] 4- separation, and can retain [Fe(CN)6] 4- and / or [Mn(CN)6]4- The structure will not produce cyanide ions and hydrocyanic acid. After recycling, the solution containing [Fe(CN)6] 4- and / or [Mn(CN)6] 4- can be further processed into raw materials for synthesizing Prussian - type cathode materials; the recycling method can process Prussian - type cathode materials in waste sodium batteries on a large scale, and the treatment process is non - toxic, harmless, and has a simple process. The recycling method has good economic benefits.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for recycling Prussian - type cathode materials, and the recycling method includes the following steps:

[0010] (1) Disassemble the battery containing Prussian - type cathode materials to obtain Prussian - type cathode materials;

[0011] (2) Place the Prussian - type cathode materials obtained in step (1) in a non - oxidizing acid for dissolution to obtain a first solution;

[0012] (3) Pass an oxygen source into the first solution obtained in step (2) for an oxidation reaction, and then after solid - liquid separation, obtain transition metal hydroxyoxides and a second solution containing H4[Fe(CN)6] and / or H4[Mn(CN)6].

[0013] The recycling method of the present invention can effectively separate the transition metal elements in the Prussian - type materials that are not coordinated with cyanide from [Fe(CN)6] 4- and / or [Mn(CN)6] 4- and can retain the structure of [Fe(CN)6] 4- and / or [Mn(CN)6] 4- without generating cyanide ions and hydrocyanic acid. After recycling, the solution containing [Fe(CN)6] 4- and / or [Mn(CN)6] 4- can be further processed into raw materials for synthesizing Prussian - type cathode materials; the recycling method can process Prussian - type cathode materials in waste sodium batteries on a large scale, and the treatment process is non - toxic, harmless, and has a simple process. The recycling method has good economic benefits.

[0014] The following are preferred technical solutions of the present invention, but not limitations to the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, the Prussian - type cathode material in step (1) includes any one or a combination of at least two of manganese - based Prussian white, iron - based Prussian white, or manganese - based high - manganese Prussian white. Typical but non - limiting examples of the combination include the combination of manganese - based Prussian white and iron - based Prussian white, the combination of manganese - based Prussian white and manganese - based high - manganese Prussian white, the combination of iron - based Prussian white and manganese - based high - manganese Prussian white, and the combination of manganese - based Prussian white, iron - based Prussian white, and manganese - based high - manganese Prussian white.

[0016] As a preferred technical solution of the present invention, the non - oxidizing acid in step (2) includes hydrochloric acid and / or phosphoric acid.

[0017] As a preferred technical solution of the present invention, the pH of the non - oxidizing acid in step (2) is 2 - 6, such as 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0018] By controlling the pH of the non - oxidizing acid of the present invention to be 2 - 6, the Prussian - type cathode material can be dissolved to form a solution, and at the same time, a suitable pH environment is provided for subsequent gas - phase oxidation. If the pH is close to neutral, it will be difficult to dissolve the Prussian - type cathode material; if the pH > 8 or < 2, the Prussian - type cathode material will decompose.

[0019] As a preferred technical solution of the present invention, the dosage of the Prussian - type cathode material in step (2) is 0.15 - 0.65 mol / L, such as 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, or 0.65 mol / L, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0020] Preferably, the molar amount of the non - oxidizing acid in step (2) is 10% and below of the molar amount of the Prussian - type cathode material, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0021] The present invention limits the dosage of the non - oxidizing acid. If the dosage of the acid is too much, it may introduce too many acid - radical ions, increasing the subsequent impurity - removal cost; if the dosage of the acid is too small, it may lead to slow dissolution of the Prussian - type cathode material.

[0022] As a preferred technical solution of the present invention, the oxygen source in step (3) includes oxygen.

[0023] Preferably, the amount of the oxygen source in step (3) is 1 times or more of the total molar amount of free transition metal ions in the first solution, for example, 1 times, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times or 4 times, etc., but is not limited to the listed values. Other values not listed within the above numerical range are also applicable.

[0024] The free transition metal ions in the first solution of the present invention refer to free transition metal ions such as Fe ions and Mn ions other than the Fe and Mn elements coordinated with cyanide in [Fe(CN)6] and [Mn(CN)6]. Then, by controlling the amount of the oxygen source to be 1 times or more of the total molar amount of the free transition metal ions in the first solution, that is, maintaining an equal reaction or an excess reaction, preferably an excess, it can be ensured that the transition metal ions are fully oxidized to hydroxy oxides.

[0025] As a preferred technical solution of the present invention, the temperature of the oxidation reaction in step (3) is 25-90°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, etc., but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

[0026] The present invention controls the temperature of the oxidation reaction within a temperature range of 25 to 90° C., thereby ensuring that the oxidation reaction proceeds rapidly.

[0027] Preferably, the oxidation reaction time in step (3) is 30 to 360 min, for example, 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, 210 min, 240 min, 270 min, 300 min, 330 min or 360 min, etc., but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

[0028] The present invention can improve the oxidation rate of transition metal ions as much as possible by prolonging the reaction time, but too long a reaction time will also lead to an increase in cost.

[0029] As a preferred technical solution of the present invention, the recovery method comprises the following steps:

[0030] (1) disassembling a battery containing a Prussian-type positive electrode material to obtain a Prussian-type positive electrode material; the Prussian-type positive electrode material includes any one of manganese-based Prussian white, iron-based Prussian white, or manganese-based high-manganese Prussian white, or a combination of at least two thereof;

[0031] (2) The Prussian - type cathode material obtained in step (1) is placed in hydrochloric acid and / or phosphoric acid with a pH of 2 - 6, and the dosage is 0.15 - 0.65 mol / L, and the molar amount of the non - oxidizing acid is 10% or less of the molar amount of the Prussian - type cathode material, and then dissolution is carried out to obtain a first solution;

[0032] (3) Oxygen is introduced into the first solution obtained in step (2) as an oxygen source, and oxygen is continuously introduced at 25 - 90 °C for an oxidation reaction for 30 - 360 min. The dosage of the oxygen source is controlled to be 1 - 4 times the total molar amount of free transition metal ions in the first solution. After solid - liquid separation, a transition metal hydroxy - oxide and a second solution containing H4[Fe(CN)6] and / or H4[Mn(CN)6] are obtained.

[0033] In a second aspect, the present invention provides a preparation method of a Prussian - type cathode material, and the preparation method includes the following steps:

[0034] (S1) The pH of the second solution obtained by the recovery method described in the first aspect is adjusted using sodium hydroxide to obtain a third solution containing Na4[Fe(CN)6] and / or Na4[Mn(CN)6];

[0035] (S2) The third solution obtained in step (S1) is subjected to a coprecipitation reaction with a fourth solution containing a complexing agent and a divalent transition metal salt to obtain a Prussian - type cathode material.

[0036] As a preferred technical solution of the present invention, the pH of the second solution in step (S1) is adjusted within the range of 6 - 10, such as 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0037] Preferably, step (S1) further includes adding a sodium additive to the obtained third solution.

[0038] Preferably, the sodium additive includes sodium chloride.

[0039] Preferably, the complexing agent in step (S2) includes citric acid.

[0040] Preferably, the divalent transition metal salt in step (S2) includes manganese sulfate.

[0041] Preferably, the temperature of the coprecipitation reaction in step (S2) is 50 - 60 °C, such as 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0042] Preferably, the pH of the coprecipitation reaction in step (S2) is 6.5 to 9.5, such as 6.5, 7, 7.5, 8, 8.5, 9, 9.5, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0043] Preferably, step (S2) further includes aging, washing, and drying in sequence after the coprecipitation reaction to obtain the Prussian-type cathode material.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] The recycling method of the present invention can effectively separate the transition metal elements not coordinated with cyanide in the Prussian-type material from [Fe(CN)6] 4- and / or [Mn(CN)6] 4- and can retain the structure of [Fe(CN)6] 4- and / or [Mn(CN)6] 4- without generating cyanide ions and hydrocyanic acid. The solution containing [Fe(CN)6] 4- and / or [Mn(CN)6] 4- after recycling can be further processed into raw materials for synthesizing Prussian-type cathode materials; the recycling method can process Prussian-type cathode materials in waste sodium batteries on a large scale, and the treatment process is non-toxic, harmless, and has a simple process, and the recycling method has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the SEM test diagram of the manganese-based Prussian white cathode material obtained by the preparation method of Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0048] Example 1

[0049] This example provides a recycling method for Prussian-type cathode materials, and the recycling method includes the following steps:

[0050] (1) Collect waste sodium-ion batteries of manganese-based Prussian white (Na2Mn[Fe(CN)6]) generated in the laboratory, disassemble to obtain the positive electrode sheet, scrape off the manganese-based Prussian white cathode material on the positive electrode sheet, and a total of 110 mol of manganese-based Prussian white cathode material is collected;

[0051] (2) Add the manganese-based Prussian white cathode material obtained in step (1) to 400 L of hydrochloric acid solution with pH = 2 and soak for dissolution. The dosage of the manganese-based Prussian white cathode material is 0.275 mol / L, and filter to obtain the first solution;

[0052] (3) Pass oxygen into the first solution obtained in step (2) as the oxygen source. Set the flow rate of oxygen to 1000 Nm 3 / h, continuously pass oxygen at 55 °C for 300 min for the oxidation reaction, control the dosage of the oxygen to be 2 times the molar amount of free Mn 2+ in the first solution. After filtration, a red manganese oxyhydroxide precipitate and a second solution containing ferrocyanic acid are obtained.

[0053] This example also provides a preparation method of a Prussian-type cathode material. The preparation method includes the following steps:

[0054] (S1) Use sodium hydroxide to adjust the pH of the second solution obtained by the recycling method to 8, and then add sodium chloride as a sodium additive to make the concentration of the sodium chloride reach 0.275 mol / L to obtain a third solution containing sodium ferrocyanide;

[0055] (S2) Prepare a fourth solution containing 0.458 mol / L of citric acid and 0.458 mol / L of manganese sulfate. React the third solution obtained in step (S1) with the fourth solution in a reaction kettle under nitrogen protection at 55 °C. Use a metering pump to control the flow rates of the third solution and the fourth solution to maintain the pH of the reaction system at 6.5 - 9.5. After the reaction is completed, age for 12 h, then wash with pure water and filter, and finally dry at 160 °C for 12 h to obtain the manganese-based Prussian white cathode material.

[0056] Figure 1 is the SEM test diagram of the manganese-based Prussian white cathode material obtained by the preparation method of Example 1 of the present invention. It can be seen from the figure that the prepared manganese-based Prussian white cathode material has a cubic structure, good crystallinity, and a particle size of 1 - 4 μm.

[0057] Example 2

[0058] This example provides a recycling method of a Prussian-type cathode material. The recycling method includes the following steps:

[0059] (1) Collect waste sodium-ion batteries with iron-based Prussian white (Na2Fe[Fe(CN)6]) produced in the laboratory, disassemble to obtain the positive electrode sheet, scrape off the iron-based Prussian white cathode material on the positive electrode sheet, and collect a total of 210 mol of the iron-based Prussian white cathode material;

[0060] (2) Add the iron-based Prussian white cathode material obtained in step (1) to 1400 L of phosphoric acid solution with pH = 4 and soak for dissolution. Among them, the dosage of the iron-based Prussian white cathode material is 0.15 mol / L to obtain a first solution;

[0061] (3) Pass oxygen into the first solution obtained in step (2) as the oxygen source. Set the flow rate of oxygen to 3200 Nm 3 / h, continuously pass oxygen at 90 °C for 360 min of oxidation reaction, control the dosage of the oxygen to be 4 times the molar amount of free Fe 2+ in the first solution, and then after filtration, obtain a red manganese oxyhydroxide precipitate and a second solution containing ferrocyanic acid.

[0062] This example also provides a preparation method of a Prussian-type cathode material, and the preparation method includes the following steps:

[0063] (S1) Use sodium hydroxide to adjust the pH of the second solution obtained by the recovery method to 6, and then add sodium chloride as a sodium additive to make the concentration of the sodium chloride reach 0.15 mol / L to obtain a third solution containing sodium ferrocyanide;

[0064] (S2) Prepare a fourth solution containing 0.25 mol / L of citric acid and 0.25 mol / L of manganese sulfate. Mix the third solution obtained in step (S1) with the fourth solution in a reaction kettle under nitrogen protection, carry out a hydrothermal reaction at 50 °C, use a metering pump to control the flow rates of the third solution and the fourth solution, keep the pH of the reaction system at 6.5 - 9.5, age for 10 h after the reaction, then wash with pure water and filter, and finally dry at 140 °C for 14 h to obtain a manganese-based Prussian white cathode material.

[0065] Example 3

[0066] This example provides a recovery method of a Prussian-type cathode material, and the recovery method includes the following steps:

[0067] (1) Collect waste sodium-ion batteries with manganese-based high-manganese Prussian white (Na2Mn[Mn(CN)6]) cathodes generated in the laboratory, disassemble to obtain the cathode plates, scrape off the manganese-based high-manganese Prussian white cathode material on the cathode plates, and collect a total of 50 mol of manganese-based high-manganese Prussian white cathode material;

[0068] (2) Add the manganese-based high-manganese Prussian white cathode material obtained in step (1) to 80 L of a mixed solution of hydrochloric acid and phosphoric acid with pH = 6 and soak for dissolution. Among them, the dosage of the manganese-based high-manganese Prussian white cathode material is 0.15 mol / L to obtain a first solution;

[0069] (3) Introduce oxygen as the oxygen source into the first solution obtained in step (2), set the flow rate of oxygen to 300 Nm 3 / h, continuously introduce oxygen at 25 °C for an oxidation reaction for 240 min, control the amount of oxygen used to be 1 time the molar amount of free Mn 2+ in the first solution. After filtration, a red manganese oxyhydroxide precipitate and a second solution containing H4[Mn(CN)6] are obtained.

[0070] This example also provides a method for preparing a Prussian - type cathode material, and the preparation method includes the following steps:

[0071] (S1) Use sodium hydroxide to adjust the pH of the second solution obtained by the recycling method to 10, and then add sodium chloride as a sodium additive to make the concentration of sodium chloride reach 0.15 mol / L, obtaining a third solution containing Na4[Mn(CN)6];

[0072] (S2) Prepare a fourth solution containing 0.25 mol / L of citric acid and 0.25 mol / L of manganese sulfate. Mix the third solution obtained in step (S1) and the fourth solution in a reaction kettle under nitrogen protection, carry out a hydrothermal reaction at 60 °C, use a metering pump to control the flow rates of the third solution and the fourth solution, so that the pH of the reaction system is maintained at 6.5 - 9.5. After the reaction ends, age for 14 h, then wash with pure water and filter, and finally dry at 180 °C for 10 h to obtain a manganese - based Prussian white cathode material.

[0073] Example 4

[0074] This example provides a method for recycling a Prussian - type cathode material. Except that the hydrochloric acid with pH = 2 in step (2) is adjusted to pH = 1.5, other conditions are exactly the same as those in Example 1.

[0075] Example 5

[0076] This example provides a method for recycling a Prussian - type cathode material. Except that the hydrochloric acid with pH = 2 in step (2) is adjusted to pH = 4, other conditions are exactly the same as those in Example 1.

[0077] Example 6

[0078] This example provides a method for recycling a Prussian - type cathode material. Except that the hydrochloric acid with pH = 2 in step (2) is adjusted to pH = 6, other conditions are exactly the same as those in Example 1.

[0079] Example 7

[0080] This embodiment provides a method for recycling Prussian - type cathode materials. Except that the hydrochloric acid with pH = 2 in step (2) is adjusted to pH = 6.5, other conditions are exactly the same as those in Embodiment 1.

[0081] Embodiment 8

[0082] This embodiment provides a method for recycling Prussian - type cathode materials. Except that a total of 12 mol of manganese - based Prussian white cathode materials are collected in step (1), such that the amount of manganese - based Prussian white cathode materials used in step (2) is 0.03 mol / L, other conditions are exactly the same as those in Embodiment 1;

[0083] This embodiment also provides a method for preparing Prussian - type cathode materials. Except that the concentration of sodium chloride in step (S1) is adjusted from 0.275 mol / L to 0.03 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.458 mol / L to 0.05 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0084] Embodiment 9

[0085] This embodiment provides a method for recycling Prussian - type cathode materials. Except that a total of 20 mol of manganese - based Prussian white cathode materials are collected in step (1), such that the amount of manganese - based Prussian white cathode materials used in step (2) is 0.05 mol / L, other conditions are exactly the same as those in Embodiment 1;

[0086] This embodiment also provides a method for preparing Prussian - type cathode materials. Except that the concentration of sodium chloride in step (S1) is adjusted from 0.275 mol / L to 0.05 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.458 mol / L to 0.083 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0087] Embodiment 10

[0088] This embodiment provides a method for recycling Prussian - type cathode materials. Except that a total of 60 mol of manganese - based Prussian white cathode materials are collected in step (1), such that the amount of manganese - based Prussian white cathode materials used in step (2) is 0.15 mol / L, other conditions are exactly the same as those in Embodiment 1;

[0089] This embodiment also provides a method for preparing a Prussian - type cathode material. Except that the concentration of sodium chloride in step (S1) is adjusted from 0.275 mol / L to 0.15 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.25 mol / L to 0.25 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0090] Embodiment 11

[0091] This embodiment provides a method for recycling a Prussian - type cathode material. Except that in step (1), a total of 160 mol of manganese - based Prussian white cathode material is collected, such that the amount of manganese - based Prussian white cathode material used in step (2) is 0.4 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0092] This embodiment also provides a method for preparing a Prussian - type cathode material. Except that the concentration of sodium chloride in step (S1) is adjusted from 0.275 mol / L to 0.4 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.458 mol / L to 0.678 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0093] Embodiment 12

[0094] This embodiment provides a method for recycling a Prussian - type cathode material. Except that in step (1), a total of 260 mol of manganese - based Prussian white cathode material is collected, such that the amount of manganese - based Prussian white cathode material used in step (2) is 0.65 mol / L, other conditions are exactly the same as those in Embodiment 1;

[0095] This embodiment also provides a method for preparing a Prussian - type cathode material. Except that the concentration of sodium chloride in step (S1) is adjusted from 0.275 mol / L to 0.65 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.458 mol / L to 1.083 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0096] Embodiment 13

[0097] This embodiment provides a method for recycling a Prussian - type cathode material. Except that in step (1), a total of 320 mol of manganese - based Prussian white cathode material is collected, such that the amount of manganese - based Prussian white cathode material used in step (2) is 0.8 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0098] This embodiment also provides a method for preparing a Prussian-type cathode material. Except that the sodium chloride concentration in step (S1) is adjusted from 0.275 mol / L to 0.8 mol / L, and the concentrations of citric acid and manganese sulfate in step (S2) are adjusted from 0.458 mol / L to 1.333 mol / L, other conditions are exactly the same as those in Embodiment 1.

[0099] Example 14

[0100] This embodiment provides a method for recycling a Prussian-type cathode material. Except that the temperature of the oxidation reaction in step (3) is adjusted from 55 °C to 20 °C, other conditions are exactly the same as those in Embodiment 1.

[0101] Example 15

[0102] This embodiment provides a method for recycling a Prussian-type cathode material. Except that the temperature of the oxidation reaction in step (3) is adjusted from 55 °C to 25 °C, other conditions are exactly the same as those in Embodiment 1.

[0103] Example 16

[0104] This embodiment provides a method for recycling a Prussian-type cathode material. Except that the temperature of the oxidation reaction in step (3) is adjusted from 55 °C to 90 °C, other conditions are exactly the same as those in Embodiment 1.

[0105] Example 17

[0106] This embodiment provides a method for recycling a Prussian-type cathode material. Except that the temperature of the oxidation reaction in step (3) is adjusted from 55 °C to 95 °C, other conditions are exactly the same as those in Embodiment 1.

[0107] Comparative Example 1

[0108] Purchase commercially available manganese-based Prussian white material for subsequent testing.

[0109] After performing particle size tests (respectively obtaining data of D10, D50, and D100), thermogravimetric analysis (TG), and specific surface area tests (BET) on the newly prepared Prussian white materials obtained by the recycling method and the preparation method in the examples and the manganese-based Prussian white material purchased in Comparative Example 1, and using them as cathode materials to fabricate sodium-ion button batteries, charge-discharge tests are carried out under the conditions of 2 - 4 V and 0.1 C. The results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1:

[0114] (1) Comparing Example 1 with Examples 4 - 7, it is found that the specific capacity of Examples 1, 5, and 6 is better than that of Examples 4 and 7. This is because the pH of Example 4 is too low, which may cause partial decomposition of the [Fe(CN)6] 4- group to produce hydrocyanic acid and volatilize into the air, resulting in a lower concentration of the [Fe(CN)6] 4- group in the second solution for preparing the Prussian - type cathode material, forming more vacancy defects, and thus leading to a decrease in specific capacity; while the pH of Example 7 is too high. Under this pH condition, the solubility of the Prussian - type cathode material is relatively low, and less Na2Mn[Fe(CN)]6 dissolves in the first solution, also resulting in a lower concentration of the [Fe(CN)6] 4- group in the second solution for preparing the Prussian - type cathode material, forming more vacancy defects, and thus leading to a decrease in specific capacity;

[0115] (2) Comparing Example 1 with Examples 8 - 13, it is found that the specific capacity of Example 1 is higher than that of Examples 8 and 9. This is because the amount of Prussian material used is too small, resulting in a lower concentration of the [Fe(CN)6] 4- group;

[0116] (3) Comparing Example 1 with Examples 14 - 17, it is found that the specific capacity of Example 1 is higher than that of Examples 14 and 17. This is because a lower reaction temperature may cause incomplete oxidation of Mn 2+ ions in the first solution, while too high a reaction temperature may promote the formation and volatilization of hydrocyanic acid, thus affecting the recovery rate of the [Fe(CN)6] 4- group;

[0117] As can be seen from the above, when the pH of the non - oxidizing acid, the amount of Prussian white, and the oxidation temperature are not suitable, it will ultimately cause a decrease in the concentration of ferrocyanate in the first solution, resulting in an increase in vacancy defects of the synthesized Prussian white and a decrease in specific capacity, but it has little effect on the particle size of the obtained product; while with the coordination of appropriate parameters, using the recovery method and preparation method of the present invention can effectively separate and recover the transition metal elements not coordinated with cyanide groups in the Prussian - type material from [Fe(CN)6] 4- and / or [Mn(CN)6] 4- and finally a new Prussian - type cathode material with excellent performance can be prepared.

[0118] The present invention illustrates the detailed structural features of the present invention through the above embodiments. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

[0119] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0120] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0121] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for recycling a Prussian - type cathode material, characterized in that, The recovery method includes the following steps: (1) Disassembling the battery containing Prussian - type cathode material to obtain Prussian - type cathode material; (2) Placing the Prussian - type cathode material obtained in step (1) into a non - oxidizing acid for dissolution to obtain a first solution; (3) Passing an oxygen source into the first solution obtained in step (2) for an oxidation reaction, and after solid - liquid separation, obtaining transition metal hydroxy - oxide and a second solution containing H4[Fe(CN)6] and / or H4[Mn(CN)6].

2. The recovery method according to claim 1, wherein The Prussian - type cathode material described in step (1) includes any one or a combination of at least two of manganese - based Prussian white, iron - based Prussian white, or manganese - based Prussian blue - manganese white.

3. The recovery method according to claim 1, wherein, The non - oxidizing acid described in step (2) includes hydrochloric acid and / or phosphoric acid.

4. The recovery method according to claim 1, characterized in that, The pH of the non - oxidizing acid described in step (2) is 2 - 6.

5. The recovery method according to claim 1, wherein The dosage of the Prussian - type cathode material described in step (2) is 0.15 - 0.65 mol / L.

6. The recovery method according to claim 1, characterized in that, The molar amount of the non - oxidizing acid described in step (2) is 10% or less of the molar amount of the Prussian - type cathode material.

7. The recovery method according to claim 1, characterized in that The oxygen source described in step (3) includes oxygen.

8. The recycling method according to claim 1, characterized in that The dosage of the oxygen source described in step (3) is 1 time or more of the total molar amount of free transition metal ions in the first solution.

9. The recovery method according to claim 1, characterized in that The temperature of the oxidation reaction described in step (3) is 25 - 90 °C.

10. The recycling method according to claim 1, wherein The time of the oxidation reaction described in step (3) is 30 - 360 min.

11. The recovery method according to claim 1, wherein, The recovery method includes the following steps: (1) Disassembling the battery containing Prussian - type cathode material to obtain Prussian - type cathode material; the Prussian - type cathode material includes any one or a combination of at least two of manganese - based Prussian white, iron - based Prussian white, or manganese - based Prussian blue - manganese white; (2) Placing the Prussian - type cathode material obtained in step (1) into hydrochloric acid and / or phosphoric acid with a pH of 2 - 6 at a dosage of 0.15 - 0.65 mol / L, and making the molar amount of the non - oxidizing acid be 10% or less of the molar amount of the Prussian - type cathode material for dissolution to obtain a first solution; (3) Passing oxygen as the oxygen source into the first solution obtained in step (2), continuously passing oxygen at 25 - 90 °C for an oxidation reaction for 30 - 360 min, controlling the dosage of the oxygen source to be 1 - 4 times the total molar amount of free transition metal ions in the first solution, and after solid - liquid separation, obtaining transition metal hydroxy - oxide and a second solution containing H4[Fe(CN)6] and / or H4[Mn(CN)6].

12. A preparation method of a Prussian-type cathode material, characterized in that, The preparation method includes the following steps: (S1) Adjusting the pH of the second solution obtained by the recovery method according to any one of claims 1 - 11 using sodium hydroxide to obtain a third solution containing Na4[Fe(CN)6] and / or Na4[Mn(CN)6]; (S2) Performing a co - precipitation reaction on the third solution obtained in step (S1) and a fourth solution containing a complexing agent and a divalent transition metal salt to obtain Prussian - type cathode material.

13. The preparation method according to claim 12, characterized in that, The adjustment range of the pH of the second solution described in step (S1) is 6 - 10.

14. The preparation method according to claim 12, wherein Step (S1) also includes adding a sodium additive to the obtained third solution.

15. The preparation method according to claim 14, characterized in that, The sodium additive includes sodium chloride.

16. The preparation method according to claim 12, wherein, The complexing agent described in step (S2) includes citric acid.

17. The preparation method according to claim 12, characterized in that, The divalent transition metal salt described in step (S2) includes manganese sulfate.

18. The preparation method according to claim 12, wherein, The temperature of the coprecipitation reaction described in step (S2) is 50 - 60 °C.

19. The preparation method according to claim 12, characterized in that, The pH of the coprecipitation reaction described in step (S2) is 6.5 - 9.

5.

20. The preparation method according to claim 12, wherein, Step (S2) further includes, after the coprecipitation reaction, aging, washing, and drying in sequence to obtain the Prussian-type cathode material.

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