A method for recovering a positive electrode material from a waste sodium-ion battery

Abstract

The application discloses a method for recovering positive electrode materials from waste sodium ion batteries. The method is to discharge and disassemble the waste sodium ion batteries to separate positive electrode sheets and negative electrode sheets, mix the positive electrode sheets and the negative electrode sheets for calcination, perform acid reduction leaching on calcined slag to obtain a metal leaching solution, perform hydrolysis precipitation on the metal leaching solution by adjusting pH to obtain a metal precipitation slag, perform acid dissolution on the metal precipitation slag and adjust a metal metering ratio to obtain a metal purification solution, mix the metal purification solution with a precipitant and a complexing agent to perform a co-precipitation reaction to obtain a metal hydroxide precursor, and perform a solid-phase sintering reaction on the metal hydroxide precursor and sodium carbonate to obtain sodium ion positive electrode materials. The sodium ion positive electrode materials regenerated by the method have excellent electrochemical performance and almost reach the discharge specific capacity of original positive electrode materials, and the method is simple, low in cost, suitable for various transition metal sodium ion batteries and wide in application range.

Description

Technical Field

[0001] This invention relates to a method for recycling electrode materials, specifically a method for recycling positive electrode materials from waste sodium-ion batteries, belonging to the field of sodium-ion battery recycling. Background Technology

[0002] Lithium-ion batteries are limited and expensive, requiring alternatives. Sodium-ion batteries are abundant, inexpensive, and environmentally friendly, leading to their development. Compared to lithium-ion batteries, the most prominent advantages of sodium-ion batteries are: (1) Economy: Abundant resources and simple refining; compatible with lithium-ion battery processes, making it easy to switch and reuse production lines; lower cost of auxiliary materials such as current collectors. (2) Safety: High internal resistance, low instantaneous heat generation, and low risk of thermal safety accidents; can discharge to 0V without over-discharge issues, ensuring safe transportation; and a wide operating temperature range.

[0003] Various companies are vying for dominance, with prominent examples including Zhongke Haina, CATL, and Sodium Innovation Energy. Zhongke Haina jointly developed and put into operation a sodium-ion battery energy storage system with Huayang Technology in June 2021; in July 2022, the world's first GWh sodium-ion battery production line was completed, with a second-phase project planned for later implementation. CATL announced its first-generation sodium-ion battery with an energy density of 160Wh / kg in July 2021, with the second generation expected to exceed 200Wh / kg, and a basic industrial chain expected to be formed by 2023. Sodium Innovation Energy anticipates completing the production of 3,000 tons of cathode materials and 5,000 tons of electrolyte in 2022.

[0004] Currently, the recycling of sodium-ion battery cathode materials is not yet mature. The methods used for lithium-ion battery recycling involve crushing the battery into black powder, then leaching and extracting to recover heavy metals such as nickel, cobalt, and manganese, ultimately obtaining a single-component transition metal solution. This process is cumbersome; the crushing process makes it difficult to effectively control impurities and purity, and the leaching and extraction processes consume significant amounts of acid and alkali, resulting in high costs and lengthy processes. The product obtained is a single-component intermediate rather than cathode material.

[0005] The expansion of sodium-ion battery production capacity will inevitably lead to demand for the sodium-ion battery recycling industry. The positive electrode materials, negative electrode materials, negative electrode sheets, electrolytes, etc. of sodium-ion batteries are different from those of lithium batteries. Therefore, new environmentally friendly processes are needed to recycle waste sodium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing sodium-ion battery cathode material recycling technologies, such as complex processes, high costs, and low recycling efficiency, the present invention aims to provide a method for recycling cathode materials from waste sodium-ion batteries. This method achieves the regeneration of sodium-ion battery cathode materials, and the regenerated sodium-ion battery cathode materials have a high discharge specific capacity, almost reaching the discharge specific capacity of the original cathode materials. Furthermore, the method is simple to operate, low in cost, and conducive to resource recycling.

[0007] To achieve the above-mentioned technical objectives, this invention provides a method for recovering positive electrode materials from waste sodium-ion batteries. The method involves discharging and disassembling the waste sodium-ion batteries to separate positive and negative electrode sheets. The positive and negative electrode sheets are then mixed and calcined. The calcined residue is leached by acid reduction to obtain a metal leachate. The metal leachate is then hydrolyzed and precipitated by adjusting the pH to obtain a metal precipitate residue. The metal precipitate residue is dissolved by acid and the metal stoichiometric ratio is adjusted to obtain a metal purification solution. This metal purification solution is mixed with a precipitant and a complexing agent for a co-precipitation reaction to obtain a metal hydroxide precursor. The metal hydroxide precursor is then subjected to a solid-state sintering reaction with sodium carbonate to obtain the sodium-ion positive electrode material.

[0008] In the recycling process of this invention, firstly, the positive and negative electrode sheets obtained from the disassembly and separation of waste sodium-ion batteries are directly used as the initial raw materials for the extraction of transition metals. This eliminates the complex mechanical process of crushing traditional batteries into powder and avoids the introduction of more impurities due to mechanical crushing, thus improving product purity. Secondly, after calcination, the aluminum in the positive and negative electrode sheets dissolves into molten aluminum and is separated and recovered. At the same time, the carbon materials, conductive agents, binders, and other organic matter in the electrode sheets are also burned off in the form of carbon dioxide and water vapor. Finally, the transition metals are further purified by acid reduction leaching and pH adjustment to precipitate the metals. This allows the metal precursor obtained by the co-precipitation reaction of the purified transition metal product to directly react with sodium carbonate to obtain sodium-ion battery positive electrode materials, achieving efficient recycling of sodium-ion battery positive electrode materials.

[0009] As a preferred embodiment, the main component of the cathode material in the spent sodium-ion battery is expressed as Na. x MO2, where 0 < x ≤ 1, and M is a transition metal element. When M is a combination of multiple transition metal elements, the sum of the number of atoms of all transition metal elements equals 1.

[0010] As a preferred embodiment, the transition metal element is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, and Cu.

[0011] As a preferred embodiment, during the battery discharge and disassembly process to separate the positive and negative electrode sheets, the discharge cutoff voltage is 0–0.5V, and the sodium-ion battery positive and negative electrode sheets are separated and screened from individual cells. During this process, since some waste sodium-ion batteries cannot be fully discharged, the discharge cutoff voltage can be 0–0.5V. When separating and screening the sodium-ion battery positive and negative electrode sheets from individual cells, it is permissible for some easily carbonized materials such as separator electrolyte to be mixed in with the positive and negative electrode sheets.

[0012] As a preferred embodiment, the calcination conditions are: an oxygen-containing atmosphere, a temperature of 1000–1300℃, and a time of 2–15 h, more preferably 7–9 h. The oxygen-containing atmosphere is air, and the ventilation rate is 50–70 mL / min.

[0013] As a preferred option, the aluminum in the positive and negative electrode sheets is melted and directly recycled during the calcination process.

[0014] If the calcination temperature is too low, the molten aluminum will be difficult to melt and separate, and some aluminum compounds will remain attached to the cathode material. If the calcination temperature is too high, the molten aluminum will not melt but will instead react with a small amount of oxygen to form aluminum oxide, hindering the formation of molten aluminum. Similarly, if the calcination time is too short, the molten aluminum will not melt completely, and the carbon materials, conductive agents, and binders will not burn completely. If the calcination time is too long, energy consumption will increase and process costs will rise.

[0015] As a preferred embodiment, the leaching agent used in the acid reduction leaching process is a mixture of concentrated sulfuric acid and hydrogen peroxide solution.

[0016] As a preferred embodiment, in the acid reduction leaching process, the mass ratio of solid to leaching agent is 2 to 10:1, and more preferably 3 to 6:1.

[0017] As a preferred embodiment, the molar ratio of concentrated sulfuric acid to hydrogen peroxide is 3–10:1, more preferably 3–5:1, and most preferably 4:1. Controlling the molar ratio of concentrated sulfuric acid to hydrogen peroxide within a suitable range during acid reduction leaching is beneficial for improving the leaching efficiency of metal ions. Excessive use of concentrated sulfuric acid will lead to insufficient reduction and a reduced leaching rate of metal ions, while excessive use of hydrogen peroxide will increase the preparation cost.

[0018] As a preferred embodiment, the concentrated sulfuric acid has a pH value of 0.5 to 1. Controlling the pH value of the concentrated sulfuric acid within a suitable range is beneficial to improving the leaching efficiency of metal ions. If the pH value of the concentrated sulfuric acid is too low, the acidity is too strong, resulting in the need for more alkali to neutralize it, causing waste; if the pH value of the concentrated sulfuric acid is too high, the acidity is not strong enough, which will relatively reduce the leaching rate of metal ions.

[0019] As a preferred embodiment, the hydrogen peroxide solution has a mass fraction of 10% to 40%, more preferably 10% to 20%. Because the reaction process of the hydrogen peroxide solution involves its own disproportionation decomposition reaction, if the concentration is too high, the hydrogen peroxide will decompose into water and oxygen, resulting in resource waste and increased costs.

[0020] As a preferred embodiment, the metal leachate is subjected to hydrolysis precipitation by adjusting the pH to 7-11 to obtain a metal precipitate residue. In this metal precipitation process, the pH value can be adjusted according to the precipitation conditions of different metal elements. When multiple metal elements are present, the maximum pH value required for the precipitation of all metals is used as the system pH control value.

[0021] As a preferred option, the pH adjuster is sodium hydroxide solution.

[0022] As a preferred embodiment, concentrated sulfuric acid is used in the acid dissolution process.

[0023] As a preferred option, the process of adjusting the metal stoichiometry is as follows: determine the content of each metal element in the solution, and add the corresponding metal sulfate so that the molar ratio of each metal element in the solution is the same as the atomic ratio of the same metal element in the original waste sodium-ion battery.

[0024] As a preferred embodiment, the total concentration of metal ions in the metal purification solution is 1.5–2.5 mol / L.

[0025] As a preferred embodiment, the precipitant is a sodium hydroxide solution.

[0026] As a preferred embodiment, the complexing agent is ammonia.

[0027] As a preferred embodiment, the molar concentration of the sodium hydroxide solution is 3–5 mol / L.

[0028] As a preferred embodiment, the ammonia solution has a mass fraction of 20% to 40%.

[0029] As a preferred embodiment, the molar amount of sodium carbonate is 1.01 to 1.1 times the theoretically required molar amount for the reaction with the metal hydroxide precursor, and more preferably 1.04 times.

[0030] As a preferred embodiment, the solid-state sintering reaction conditions are: an oxygen-containing atmosphere, a temperature of 750–950°C, and a time of 5–12 hours. A further preferred atmosphere is air, with a flow rate of 60 mL / min, a sintering temperature of 850°C, and a time of 7–9 hours. Controlling the temperature and time within a suitable range during solid-state sintering is beneficial for improving the quality of the regenerated cathode material. When the sintering temperature is too low, the reaction between the precursor and the sodium source will be insufficient, while when the sintering temperature is too high, the sintered product will harden severely, hindering separation. Similarly, too short a sintering time will result in insufficient solid-state reaction, while too long a sintering time, due to the high power consumption of the roller kiln, will lead to resource waste and increased energy consumption.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) There is no need to crush the battery into powder, which reduces the recycling cost and avoids too many impurities caused by mechanical crushing. The positive and negative electrode sheets are obtained as the initial material through simple sorting, which improves the purity of the recycled product, solves the environmental problems caused by waste batteries, and improves the efficiency of resource utilization.

[0033] (2) The sodium ion cathode material obtained by recycling has excellent electrochemical performance and its discharge specific capacity can reach more than 97% of the discharge specific capacity of the original cathode material, which is almost the same as the discharge specific capacity of the original cathode material.

[0034] (3) The recycling method is simple, low-cost, and highly efficient, with a transition metal recovery rate of over 98%. It is applicable to sodium-ion batteries with different transition metals (such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu) and has a wide range of applications. Detailed Implementation

[0035] In this invention, the main component of the sodium-ion battery positive electrode is a layered oxide structure with the molecular formula Na. x MO2, where x is greater than 0 and less than or equal to 1, has an active M metal that can be one or more transition elements such as Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, such as Na. 2 / 3 [Fe 1 / 2 Mn 1 / 2 O2. This invention does not impose any special restrictions on the source of the sodium-ion battery positive electrode sheet; generally, waste sodium-ion battery positive electrode sheets from battery manufacturers are sufficient.

[0036] The following describes preferred embodiments of the present invention, and the specific details of these embodiments further illustrate the above-mentioned content of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment of a method for recovering positive electrode materials from spent sodium-ion batteries includes the following steps:

[0039] Take a number of used soft-pack sodium-ion batteries. The main component of the positive electrode material of these batteries is Na[Ni]. 1 / 3 Co 1 / 3 Fe 1 / 3 O2 is discharged with salt water until the voltage is 0V. After drying, it is cut open from the side edge with scissors and the positive and negative electrode plates are manually sorted out for later use. The diaphragm and the battery cell shell are recycled as waste.

[0040] The positive and negative electrode sheets were placed together in a container in a tube furnace for calcination. The container had two layers with a small hole in the middle to ensure that molten aluminum could flow through to the bottom layer. The calcination temperature was 1100℃, and the air flow rate was 60mL / min.

[0041] The remaining material after calcination was dissolved in concentrated sulfuric acid, the pH was adjusted to 0.5, and 15% hydrogen peroxide solution was added. The volume of the hydrogen peroxide solution was 1 / 4 of that of the concentrated sulfuric acid.

[0042] After leaching, the liquid is heated to 60°C in a water bath and stirred continuously. Then, NaOH solution is slowly added dropwise to adjust the pH to 9.5 to induce precipitation. The precipitate is filtered and washed with pure water.

[0043] The precipitate was dissolved in concentrated sulfuric acid. After complete dissolution, the copper, iron, and manganese content was determined by ICP, and the solution was prepared according to the formula Na[Ni]. 1 / 3 Co 1 / 3 Fe 1 / 3 Copper sulfate, iron and manganese solution was added to O2 in a 1:1:1 metal ratio. After adjustment, the total concentration of metal ions was measured to be 1.8 mol / L. Finally, twice the amount of sodium hydroxide solution (3.6 mol / L) was added to co-precipitate metal hydroxides.

[0044] The co-precipitated metal hydroxide was dried and then sintered with sodium carbonate powder at 850℃ for 10 h, with sodium carbonate in excess by 1.04 times. The sintering atmosphere was air with a flow rate of 60 mL / min.

[0045] The sintered material is the positive electrode material for sodium-ion batteries, and its molecular formula remains the same as before, namely Na[Ni]. 1 / 3Co 1 / 3 Fe 1 / 3 O2.

[0046] Charge-discharge tests were conducted using a battery tester at room temperature (25°C). The recovered cathode material achieved a discharge specific capacity of 158 mAh / g in the first week, reaching 95.8% of the original cathode material's discharge specific capacity (165 mAh / g). ICP testing showed a transition metal recovery rate of 98.2% (based on total nickel, cobalt, and iron elements).

[0047] Example 2

[0048] This embodiment of a method for recovering positive electrode materials from spent sodium-ion batteries includes the following steps:

[0049] Take a number of used soft-pack sodium-ion batteries. The main component of the positive electrode material of these batteries is Na. 2 / 3 [Mn 1 / 3 Co 2 / 3O2 is discharged with salt water until the voltage is 0V. After drying, it is cut open from the side edge with scissors and the positive and negative electrode plates are manually sorted out for later use. The diaphragm and the battery cell shell are recycled as waste.

[0050] The positive and negative electrode sheets were placed together in a container in a tube furnace for calcination. The container had two layers with a small hole in the middle to ensure that molten aluminum could flow through to the bottom layer. The calcination temperature was 1100℃, and the air flow rate was 60mL / min.

[0051] The remaining material after calcination was dissolved in concentrated sulfuric acid, the pH was adjusted to 0.5, and 15% hydrogen peroxide solution was added. The volume of the hydrogen peroxide solution was 1 / 4 of that of the concentrated sulfuric acid.

[0052] After leaching, the liquid is heated to 60°C in a water bath and stirred continuously. Then, NaOH solution is slowly added dropwise to adjust the pH to 11 to precipitate. The precipitate residue is filtered and washed with pure water.

[0053] The precipitate was dissolved in concentrated sulfuric acid. After complete dissolution, the copper, iron, and manganese content was determined by ICP, and the solution was prepared according to the Na... 2 / 3 [Mn 1 / 3 Co 2 / 3 The metal ions in O2 were adjusted by adding copper sulfate, iron and manganese solution in a 1:2 ratio. The total concentration of metal ions was measured to be 1.8 mol / L. Finally, twice the amount of sodium hydroxide solution (3.6 mol / L) was added to co-precipitate metal hydroxides.

[0054] The co-precipitated metal hydroxide was dried and then sintered with sodium carbonate powder at 850℃ for 10 h, with sodium carbonate in excess by 1.04 times. The sintering atmosphere was air with a flow rate of 60 mL / min.

[0055] The sintered material becomes the positive electrode material for sodium-ion batteries, and its molecular formula remains the same as before, which is Na. 2 / 3 [Mn 1 / 3Co 2 / 3 O2.

[0056] Charge-discharge tests were conducted using a battery tester at room temperature (25°C). The recovered cathode material achieved a discharge specific capacity of 110 mAh / g in the first week, reaching 97.3% of the original cathode material's discharge specific capacity (113 mAh / g). ICP testing showed a transition metal recovery rate of 98.0% (based on total manganese and cobalt elements).

[0057] Example 3

[0058] This embodiment of a method for recovering positive electrode materials from spent sodium-ion batteries includes the following steps:

[0059] Take a number of used soft-pack sodium-ion batteries. The main component of the positive electrode material of these batteries is Na. 7 / 9[Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2 is discharged with salt water until the voltage is 0V. After drying, it is cut open from the side edge with scissors and the positive and negative electrode plates are manually sorted out for later use. The diaphragm and the battery cell shell are recycled as waste.

[0060] The positive and negative electrode sheets were placed together in a container in a tube furnace for calcination. The container had two layers with a small hole in the middle to ensure that molten aluminum could flow through to the bottom layer. The calcination temperature was 1100℃, and the air flow rate was 60mL / min.

[0061] The remaining material after calcination was dissolved in concentrated sulfuric acid, the pH was adjusted to 0.5, and 15% hydrogen peroxide solution was added. The volume of the hydrogen peroxide solution was 1 / 4 of that of the concentrated sulfuric acid.

[0062] After leaching, the liquid is heated to 60°C in a water bath and stirred continuously. Then, NaOH solution is slowly added dropwise to adjust the pH to 11 to precipitate. The precipitate residue is filtered and washed with pure water.

[0063] The precipitate was dissolved in concentrated sulfuric acid. After complete dissolution, the copper, iron, and manganese content was determined by ICP, and the solution was prepared according to the Na... 7 / 9 [Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 The metal concentration of O2 was adjusted by adding copper sulfate, iron and manganese solution in a 2:1:6 ratio. The total concentration of metal ions was measured to be 1.9 mol / L. Finally, twice the amount of sodium hydroxide solution (3.8 mol / L) was added to co-precipitate metal hydroxide.

[0064] The co-precipitated metal hydroxide was dried and then sintered with sodium carbonate powder at 850℃ for 10 h, with sodium carbonate in excess by 1.04 times. The sintering atmosphere was air with a flow rate of 60 mL / min.

[0065] The sintered material becomes the positive electrode material for sodium-ion batteries, and its molecular formula remains the same as before, which is Na. 7 / 9 [Cu 2 / 9Fe 1 / 9 Mn 2 / 3 O2.

[0066] Charge-discharge tests were conducted using a battery tester at room temperature (25°C). The recovered cathode material achieved a discharge specific capacity of 90 mAh / g in the first week, reaching 97.8% of the original cathode material's discharge specific capacity (92 mAh / g). ICP testing showed a transition metal recovery rate of 98.1% (based on total copper, iron, and manganese elements).

[0067] Example 4

[0068] The cathode material was recovered using the method of Example 1, except that the amount of sodium carbonate added during the solid-phase reaction was changed to 1.0 times.

[0069] The cathode material prepared in this embodiment was subjected to charge-discharge tests using a battery tester at room temperature (25°C). The results showed that the discharge specific capacity of the recovered cathode material reached 130 mAh / g in the first week, which was only 78.8% of the discharge specific capacity of the original cathode material (165 mAh / g). ICP testing showed that its transition metal recovery rate reached 96.9% (based on the total amount of nickel, cobalt, and iron).

[0070] It is evident that if an inappropriate excess of sodium carbonate is added during the solid-phase reaction, the reaction between sodium carbonate and metal hydroxide will be incomplete, leading to a decrease in discharge specific capacity. Furthermore, the transition metal does not react completely with sodium carbonate, resulting in a reduced transition metal recovery rate.

[0071] Comparative Example 1

[0072] The sodium-ion batteries are crushed into battery powder using a battery crusher, and then the positive electrode material is recycled. The specific steps include:

[0073] Take a number of used soft-pack sodium-ion batteries. The main component of the positive electrode material of these batteries is Na[Ni]. 1 / 3 Co 1 / 3 Fe 1 / 3 O2 is discharged with salt water until the voltage reaches 0V, then dried and crushed into sodium-ion battery black powder using a traditional battery crusher.

[0074] Sodium-ion battery black powder was dissolved in concentrated sulfuric acid, and the pH was adjusted to 0.5. At the same time, 15% hydrogen peroxide solution was added, with the volume of the hydrogen peroxide solution being 1 / 4 of that of the concentrated sulfuric acid.

[0075] After leaching, the liquid is heated to 60°C in a water bath and stirred continuously. Then, NaOH solution is slowly added dropwise to adjust the pH to 9.5 to induce precipitation. The precipitate is filtered and washed with pure water.

[0076] The precipitate was dissolved in concentrated sulfuric acid. After complete dissolution, the copper, iron, and manganese content was determined by ICP, and the solution was prepared according to the formula Na[Ni]. 1 / 3 Co 1 / 3 Fe 1 / 3 Copper sulfate, iron and manganese solution was added to O2 in a 1:1:1 metal ratio. After adjustment, the total concentration of metal ions was measured to be 1.8 mol / L. Finally, twice the amount of sodium hydroxide solution (3.6 mol / L) was added to co-precipitate metal hydroxides.

[0077] The co-precipitated metal hydroxide was dried and then sintered with sodium carbonate powder at 850℃ for 10 h, with sodium carbonate in excess by 1.04 times. The sintering atmosphere was air with a flow rate of 60 mL / min.

[0078] The sintered material is the positive electrode material for sodium-ion batteries, and its molecular formula remains the same as before, namely Na[Ni]. 1 / 3Co 1 / 3 Fe 1 / 3 O2.

[0079] Charge-discharge tests were conducted using a battery tester at room temperature (25°C). The first-week discharge specific capacity of the recovered cathode material reached 148 mAh / g, which is only 89.7% of the discharge specific capacity of the original cathode material (165 mAh / g). ICP testing showed that the transition metal recovery rate reached 93.2% (based on the total amount of nickel, cobalt, and iron).

[0080] It is evident that if the process of crushing batteries into black powder is adopted instead of calcining and dissolving aluminum, the discharge specific capacity of the recovered positive electrode material will be reduced, and the transition metal will also be reduced accordingly due to the loss during the crushing process.

[0081] Comparative Example 2

[0082] The cathode material was recovered using the method described in Example 1, except that no hydrogen peroxide solution was added during the acid leaching process.

[0083] The cathode material obtained by the comparative regeneration was charged and discharged at room temperature (25℃) using a battery tester. The results showed that the discharge specific capacity of the recycled cathode material reached 118 mAh / g in the first week, which is 71.5% of the discharge specific capacity of the original cathode material (165 mAh / g). ICP testing showed that its transition metal recovery rate reached 85.2% (based on the total amount of nickel, cobalt, and iron).

[0084] It is evident that without the addition of hydrogen peroxide reducing agent during the leaching process, the leaching rate of transition metals decreases, which in turn reduces the recovery rate of transition metals. At the same time, the discharge specific capacity of the regenerated cathode material is significantly reduced.

[0085] In summary, by comprehensively controlling the electrode calcination conditions, acid leaching and reduction conditions, pH value of M metal precipitation, acid dissolution conditions of precipitate residue, concentration of metal ions in purification solution, and co-precipitation reaction conditions, this invention can achieve efficient recovery of cathode materials from waste sodium-ion batteries.

Claims

1. A method for recovering cathode materials from spent sodium-ion batteries, characterized in that: The waste sodium-ion battery is discharged and disassembled to separate the positive and negative electrode sheets. The positive and negative electrode sheets are mixed and calcined. During the calcination process, the aluminum water obtained by dissolving the metallic aluminum in the positive and negative electrode sheets is separated and recovered. The calcined slag is leached by acid reduction to obtain a metal leachate. The metal leachate is hydrolyzed and precipitated by adjusting the pH to obtain a metal precipitate residue. The metal precipitate residue is dissolved by acid and the metal stoichiometry is adjusted to obtain a metal purification solution. The metal purification solution is mixed with a precipitant and a complexing agent to carry out a co-precipitation reaction to obtain a metal hydroxide precursor. The metal hydroxide precursor is then subjected to a solid-state sintering reaction with sodium carbonate to obtain the sodium ion positive electrode material. The main component of the cathode material in the waste sodium-ion battery is expressed as Na. x MO2, where 0 < x ≤ 1, and M is a transition metal element; The calcination conditions are: an oxygen-containing atmosphere, a temperature of 1000~1300℃, and a time of 2~15h; The leaching agent used in the acid reduction leaching process is a mixture of concentrated sulfuric acid and hydrogen peroxide solution, with the concentrated sulfuric acid having a pH of 0.5 to 1 and the hydrogen peroxide solution having a mass fraction of 10% to 40%. In the acid reduction leaching process, the mass ratio of solid to leaching agent is 2~10:1; The molar ratio of concentrated sulfuric acid to hydrogen peroxide is 3~10:1; The metal leaching solution is hydrolyzed and precipitated by adjusting the pH to 7-11 to obtain metal precipitate residue; The process of adjusting the metal stoichiometry is as follows: determine the content of each metal element in the solution, and add the corresponding metal sulfate so that the molar ratio of each metal element in the solution is the same as the atomic ratio of the same metal element in the original waste sodium-ion battery. The molar amount of sodium carbonate used is 1.01 to 1.1 times the theoretically required molar amount for the reaction with the metal hydroxide precursor; The conditions for the solid-state sintering reaction are: an oxygen-containing atmosphere, a temperature of 750~950℃, and a time of 5~12h.

2. The method for recovering positive electrode material from spent sodium-ion batteries according to claim 1, characterized in that: The transition metal element is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, and Cu.

3. The method for recovering positive electrode material from spent sodium-ion batteries according to claim 1, characterized in that: The acid used in the acid dissolution process is concentrated sulfuric acid; The total concentration of metal ions in the metal purification solution is 1~3 mol / L; The precipitant is a sodium hydroxide solution; The complexing agent is ammonia water; The molar concentration of the sodium hydroxide solution is 2~6 mol / L; The mass fraction of the ammonia solution is 15% to 55%.