Method for recycling valuable elements in waste lithium iron phosphate positive electrode material

Abstract

The present application belongs to the technical field of resource recycling of waste lithium batteries, and particularly relates to a method for recycling valuable elements in waste lithium iron phosphate positive materials, comprising: adding alkali liquor to the lithium iron phosphate waste material for beating, adding an oxidizing agent for reaction, and then filtering to obtain a lithium, iron and phosphorus-containing leaching residue and a sodium phosphate solution; adding water to the lithium, iron and phosphorus-containing leaching residue for beating, adding an iron salt, and then filtering after reaction to obtain a lithium-containing solution and an iron and phosphorus-containing leaching residue; adding a precipitant to the lithium-containing solution, and then filtering after reaction to obtain a lithium salt; adding alkali liquor to the iron and phosphorus-containing leaching residue for reaction, and then filtering to obtain iron hydroxide and a sodium phosphate solution; and combining the sodium phosphate solutions, evaporating and crystallizing to obtain sodium phosphate crystals. The method for recycling valuable elements in waste lithium iron phosphate positive materials can obtain lithium salt, sodium phosphate and iron hydroxide from the lithium iron phosphate waste material, and realizes comprehensive recycling of the lithium iron phosphate waste material.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery resource recycling technology, specifically relating to a method for recycling valuable elements in waste lithium iron phosphate cathode materials. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the amount of scrapped power batteries is increasing daily, with lithium iron phosphate batteries accounting for a large proportion. Currently, the main recycling methods for lithium iron phosphate waste include direct regeneration, pyrometallurgical recycling, and wet recycling. While direct regeneration is simple and environmentally friendly, the recycled lithium iron phosphate cathode material contains impurities, resulting in poor performance of the regenerated lithium iron phosphate batteries. Wet recycling is currently the most widely used method; its main technical route involves dissolving and then precipitating the material to ultimately obtain lithium salts, iron salts, and phosphate salts.

[0003] Methods for dissolving lithium iron phosphate generally fall into two categories: acid leaching and alkaline leaching. Chinese invention patent CN 111206161 A discloses a comprehensive utilization method for waste positive electrode materials from lithium iron phosphate batteries, employing a melting (550-850℃)-sulfuric acid dissolution method to extract lithium, ultimately yielding a product containing lithium, iron, and phosphorus. While this method achieves a lithium recovery rate of ≥95%, the melting process requires high temperatures and consumes a lot of energy, and the acid dissolution process results in phosphorus loss. Invention patent CN 112694074 A discloses a method for recycling lithium iron phosphate waste and its application, involving leaching the waste under alkaline conditions, followed by ammonia leaching to ultimately obtain lithium phosphate and iron(III) oxide (Fe3O4). Although this method has a lower loss rate of lithium, iron, and phosphorus, the ammonia leaching step uses a large amount of ammonia water, generating a large amount of ammonia-nitrogen-containing wastewater, which is detrimental to clean production. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for recycling valuable elements from waste lithium iron phosphate cathode materials.

[0005] Specifically, the method for recycling valuable elements in waste lithium iron phosphate cathode materials according to the present invention includes:

[0006] (1) Add alkaline solution to lithium iron phosphate waste and slurry it. Add oxidant and react. Then filter to obtain lithium, iron and phosphorus leaching residue and sodium phosphate solution.

[0007] (2) Add water to the lithium, iron and phosphorus leaching residue, slurry it, add iron salt, react and filter to obtain lithium solution and iron and phosphorus leaching residue;

[0008] (3) Add a precipitant to the lithium-containing solution, and filter after reaction to obtain lithium salt;

[0009] (4) Add alkaline solution to the iron and phosphorus leaching residue and react it. Filter to obtain iron hydroxide and sodium phosphate solution.

[0010] (5) Combine the sodium phosphate solution from step (1) with the sodium phosphate solution from step (4), and then evaporate and crystallize to obtain sodium phosphate crystals.

[0011] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, in steps (1) and (4), the alkaline solution is one of potassium hydroxide and sodium hydroxide.

[0012] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, the concentration of the alkaline solution is 2-6 mol / L.

[0013] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, in step (1), the molar ratio of hydroxide ions in the alkaline solution to phosphate ions in the waste lithium iron phosphate is 2:1-2.4:1.

[0014] The above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials includes, as described above, at least one of hydrogen peroxide, oxygen, air, and ozone as the oxidant.

[0015] The above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials includes iron salts comprising at least one of ferric sulfate, ferric chloride, and ferric nitrate.

[0016] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, the molar ratio of iron ions in the iron salt to lithium ions in the lithium-containing, iron- and phosphorus-containing leaching residue is 3:1-3.6:1.

[0017] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, the precipitant is sodium carbonate or sodium phosphate.

[0018] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, in step (4), the molar ratio of hydroxide ions in the alkaline solution to phosphate ions in the iron-phosphate leaching residue is 3:1-3.3:1.

[0019] In the above-mentioned method for recycling valuable elements in waste lithium iron phosphate cathode materials, in step (1), the reaction temperature is 70-95℃ and the reaction time is 1-8h; in step (2), the reaction temperature is 70-90℃ and the reaction time is 3-5h; in step (3), the reaction temperature is 85-95℃ and the reaction time is 1-3h; in step (4), the reaction temperature is 75-95℃ and the reaction time is 2-4h.

[0020] The technical solution of the present invention has the following beneficial effects:

[0021] (1) The method of recycling valuable elements in waste lithium iron phosphate cathode materials of the present invention can obtain lithium salt, sodium phosphate and iron hydroxide from lithium iron phosphate waste, and realize the comprehensive recycling of lithium iron phosphate waste;

[0022] (2) The method for recycling valuable elements in waste lithium iron phosphate cathode materials of the present invention uses alkaline solution and iron salt as leaching reagents, which has the advantage of being pollution-free, further reducing production costs and reducing secondary pollution to the environment. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0024] Figure 1 This is a schematic flowchart of the method for recycling valuable elements in waste lithium iron phosphate cathode materials according to the present invention. Detailed Implementation

[0025] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0026] The terms “the,” “the,” “an,” and “a” as used herein do not indicate a limitation on quantity, but rather that at least one of the mentioned objects is present. The terms “preferred,” “more preferred,” etc., refer to embodiments of the invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention.

[0027] When a range of values ​​is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] Specifically, such as Figure 1 As shown, the method for recycling valuable elements in waste lithium iron phosphate cathode materials of the present invention includes:

[0029] (1) Add alkaline solution to lithium iron phosphate waste and slurry it. Add oxidant and react. Then filter to obtain lithium, iron and phosphorus leaching residue and sodium phosphate solution.

[0030] (2) Add water to the lithium, iron and phosphorus leaching residue, slurry it, add iron salt, react and filter to obtain lithium solution and iron and phosphorus leaching residue;

[0031] (3) Add a precipitant to the lithium-containing solution, and filter after reaction to obtain lithium salt;

[0032] (4) Add alkaline solution to the iron and phosphorus leaching residue and react it. Filter to obtain iron hydroxide and sodium phosphate solution.

[0033] (5) Combine the sodium phosphate solution from step (1) with the sodium phosphate solution from step (4), and then evaporate and crystallize to obtain sodium phosphate crystals.

[0034] The present invention provides a method for recycling valuable elements in waste lithium iron phosphate cathode materials, recovering lithium salts, sodium phosphate, and iron hydroxide from lithium iron phosphate waste, thereby achieving comprehensive recycling of lithium iron phosphate waste.

[0035] In some preferred embodiments, the method for recycling valuable elements in waste lithium iron phosphate cathode materials of the present invention includes:

[0036] (1) Add alkaline solution to lithium iron phosphate waste and slurry it. After adding oxidant and reacting, filter to obtain lithium, iron and phosphorus leaching residue and sodium phosphate solution.

[0037] The lithium iron phosphate waste refers to the cathode material obtained from the dismantling of waste lithium iron phosphate batteries and / or the waste cathode material generated during the manufacturing process of lithium iron phosphate batteries.

[0038] The alkaline solution is either potassium hydroxide or sodium hydroxide.

[0039] Preferably, the concentration of the alkaline solution is 2-6 mol / L, and the molar ratio of hydroxide ions in the alkaline solution to phosphate ions in the lithium iron phosphate waste is 2:1-2.4:1.

[0040] More preferably, the concentration of the alkaline solution is 3 mol / L, wherein the molar ratio of hydroxide ions in the alkaline solution to phosphate ions in the lithium iron phosphate waste is 2.2:1.

[0041] Preferably, the oxidant includes at least one of hydrogen peroxide, oxygen, air, and ozone.

[0042] Taking oxygen as the oxidant as an example, the chemical reaction equation that occurs in step (1) is as follows:

[0043] 2H2O+O2+4LiFePO4+8NaOH→4Fe(OH)3+4 / 3Li3PO4+8 / 3Na3PO4

[0044] Preferably, the reaction temperature of lithium iron phosphate waste in alkaline solution is 70-95℃, and the reaction time is 1-8h.

[0045] Further preferred, the lithium iron phosphate waste is reacted in alkaline solution at a temperature of 90°C for a reaction time of 2 hours.

[0046] Alkaline leaching extracts two-thirds of the phosphorus in lithium iron phosphate, effectively separating lithium and iron.

[0047] (2) Add water to the lithium, iron and phosphorus leaching residue, slurry it, add iron salt, react and filter to obtain lithium solution and iron and phosphorus leaching residue.

[0048] Preferably, the iron salt includes at least one of ferric sulfate, ferric chloride, and ferric nitrate, more preferably ferric sulfate.

[0049] Preferably, the molar ratio of iron ions in the iron salt to lithium ions in the lithium, iron, and phosphorus leaching residue is 3:1 to 3.6:1.

[0050] More preferably, the molar ratio of iron ions in the iron salt to lithium ions in the lithium, iron, and phosphorus leaching residue is 3.4:1.

[0051] Taking ferric sulfate as an example, the chemical reaction equations for the salt leaching process are as follows:

[0052] 2Li3PO4+Fe2(SO4)3→2FePO4+3Li2SO4.

[0053] Preferably, the reaction temperature is 70-90℃ and the reaction time is 3-5h.

[0054] More preferably, the reaction temperature is 80°C and the reaction time is 4 hours.

[0055] Alkaline leaching followed by iron salt leaching can effectively extract lithium from lithium iron phosphate.

[0056] (3) Add a precipitant to the lithium-containing solution, and filter after reaction to obtain lithium salt.

[0057] The lithium salt precipitant is sodium carbonate or sodium phosphate.

[0058] Specifically, when the lithium salt precipitant is sodium carbonate, the ionic equation for the reaction is:

[0059] 2Li + +CO3 2- →Li2CO3↓

[0060] When sodium phosphate is used as the lithium salt precipitant, the ionic equation for the reaction is:

[0061] 3Li + +PO4 3- →Li3PO4↓.

[0062] Preferably, the reaction temperature is 85-95℃ and the reaction time is 1-3h.

[0063] More preferably, the reaction temperature is 90°C and the reaction time is 2 hours.

[0064] (4) Add alkaline solution to the iron and phosphorus leaching residue and react it. Filter to obtain iron hydroxide and sodium phosphate solution.

[0065] Preferably, the alkaline solution includes one of potassium hydroxide and sodium hydroxide, more preferably sodium hydroxide.

[0066] Preferably, the concentration of the alkaline solution is 2-6 mol / L, wherein the molar ratio of hydroxide ions to phosphate ions in the iron-phosphorus leaching residue is 3:1-3.3:1.

[0067] More preferably, the concentration of the alkaline solution is 3 mol / L, wherein the molar ratio of hydroxide ions to phosphate ions in the iron-phosphorus leaching residue is 3:15.

[0068] When the alkaline solution is sodium hydroxide, the chemical reaction equations for the reaction between sodium hydroxide and iron- and phosphorus-containing leaching residue are as follows:

[0069] FePO4 + 3NaOH → Na3PO4 + Fe(OH)3

[0070] Preferably, the reaction temperature is 75-95℃ and the reaction time is 2-4h.

[0071] More preferably, the reaction temperature is 80°C and the reaction time is 3 hours.

[0072] (5) Combine the sodium phosphate solution from step (1) with the sodium phosphate solution from step (4), and then evaporate and crystallize to obtain sodium phosphate crystals.

[0073] like Figure 1 As shown, the method of the present invention for recovering valuable elements in waste lithium iron phosphate cathode materials recovers lithium salts, sodium phosphate and iron hydroxide from waste lithium iron phosphate battery cathode materials or waste cathode materials generated during the manufacturing process of lithium iron phosphate batteries. This achieves comprehensive recycling of lithium iron phosphate waste, and there is no waste liquid discharge throughout the process, which reduces production costs and reduces secondary pollution to the environment.

[0074] Example

[0075] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0076] Example 1

[0077] (1) 100g of lithium iron phosphate waste (containing 13.06% phosphorus) was added to 500ml of sodium hydroxide solution with a concentration of 1.84mol / L and pulped. Air was added and the mixture was reacted at 90℃ for 6h. After filtration, 136g of lithium, iron and phosphorus leaching residue and 314ml of sodium phosphate solution were obtained.

[0078] (2) Weigh 50g of the lithium, iron and phosphorus leaching residue from step (1), add 250ml of water to make a slurry, add 15.6g of ferric sulfate, react at 80℃ for 4.5h, filter after reaction to obtain 260ml of lithium sulfate solution and 79g of iron and phosphorus leaching residue.

[0079] (3) Add 8g of sodium carbonate to the lithium sulfate solution in step (2), react at 90℃ for 1h, and then filter to obtain lithium carbonate.

[0080] (4) Weigh 70g of the iron and phosphorus leaching residue from step (2) and add 250ml of 0.82mol / L sodium hydroxide solution to react. After reacting at 80℃ for 3h, filter to obtain 56g of iron hydroxide and 275ml of sodium phosphate solution.

[0081] (5) Mix the sodium phosphate solution in (1) with the sodium phosphate solution in (4), evaporate and crystallize to obtain sodium phosphate crystals.

[0082] Calculations show that after the above process, the recovery rate of lithium and phosphorus in lithium iron phosphate waste is 94%, and the recovery rate of iron is close to 100%.

[0083] Example 2

[0084] (1) 100g of lithium iron phosphate waste (containing 13.06% phosphorus) was added to 400ml of sodium hydroxide solution with a concentration of 2.3mol / L and pulped. Air was added and the mixture was reacted at 90℃ for 5h. After filtration, 142g of lithium, iron and phosphorus leaching residue and 290ml of sodium phosphate solution were obtained.

[0085] (2) Weigh 140g of lithium, iron and phosphorus leaching residue from step (1), add 380ml of water to make a slurry, add 46g of ferric sulfate, react at 80℃ for 2h, filter after reaction to obtain 352ml of lithium sulfate solution and 201g of iron and phosphorus leaching residue.

[0086] (3) Add 17g of sodium carbonate to the lithium sulfate solution in step (2), react at 90℃ for 1h, and then filter to obtain lithium carbonate.

[0087] (4) Weigh 184g of the iron and phosphorus leaching residue from step (2) and add 400ml of 1.62mol / L sodium hydroxide solution to react. After reacting at 90℃ for 3h, filter to obtain 153g of iron hydroxide and 411ml of sodium phosphate solution.

[0088] (5) Mix the sodium phosphate solution in (1) with the sodium phosphate solution in (4), evaporate and crystallize to obtain sodium phosphate crystals.

[0089] Calculations show that after the above process, the lithium recovery rate in lithium iron phosphate waste is 93%, the phosphorus recovery rate is 91%, and the iron recovery rate is 99%.

[0090] Example 3

[0091] (1) 100g of lithium iron phosphate waste (containing 13.06% phosphorus) was added to 500ml of sodium hydroxide solution with a concentration of 1.84mol / L and pulped. Air was added and the mixture was reacted at 85℃ for 6h. After filtration, 154g of lithium, iron and phosphorus leaching residue and 446ml of sodium phosphate solution were obtained.

[0092] (2) Weigh 150g of the lithium, iron and phosphorus leaching residue from step (1), add 400ml of water to make a slurry, add 46g of ferric sulfate, react at 80℃ for 2h, filter after reaction to obtain 348ml of lithium sulfate solution and 212g of iron and phosphorus leaching residue.

[0093] (3) Add 15g of sodium carbonate to the lithium sulfate solution in step (2), react at 90℃ for 1h, and then filter to obtain lithium carbonate.

[0094] (4) Weigh 180g of the iron and phosphorus leaching residue from step (2) and add 420ml of 1.55mol / L sodium hydroxide solution to react. After reacting at 90℃ for 2h, filter to obtain 149g of iron hydroxide and 435ml of sodium phosphate solution.

[0095] (5) Mix the sodium phosphate solution in (1) with the sodium phosphate solution in (4), evaporate and crystallize to obtain sodium phosphate crystals.

[0096] Calculations show that after the above process, the lithium recovery rate in lithium iron phosphate waste is 93%, the phosphorus recovery rate is 88%, and the iron recovery rate is 97%.

[0097] Example 4

[0098] (1) 100g of lithium iron phosphate waste (containing 18.38% phosphorus) was added to 700ml of sodium hydroxide solution with a concentration of 3.22mol / L and pulped. Air was added and the mixture was reacted at 95℃ for 6h. After filtration, 145g of lithium, iron and phosphorus leaching residue and 660ml of sodium phosphate solution were obtained.

[0099] (2) Weigh 134g of the lithium, iron and phosphorus leaching residue from step (1), add 600ml of water to make a slurry, add 61g of ferric sulfate, react at 90℃ for 2.5h, filter after reaction to obtain 538ml of lithium sulfate solution and 233g of iron and phosphorus leaching residue.

[0100] (3) Add 29g of sodium carbonate to the lithium sulfate solution in step (2), react at 90℃ for 1.5h, and then filter to obtain lithium carbonate;

[0101] (4) Weigh 200g of the iron and phosphorus leaching residue from step (2) and add 650ml of 1.5mol / L sodium hydroxide solution to react. After reacting at 95℃ for 2h, filter to obtain 174g of iron hydroxide and 644ml of sodium phosphate solution.

[0102] (5) Mix the sodium phosphate solution in (1) with the sodium phosphate solution in (4), evaporate and crystallize to obtain sodium phosphate crystals.

[0103] Calculations show that after the above process, the lithium recovery rate in lithium iron phosphate waste is 93.4%, the phosphorus recovery rate is 92%, and the iron recovery rate is 98%.

[0104] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for recycling valuable elements from waste lithium iron phosphate cathode materials, characterized in that, include: (1) Add sodium hydroxide solution to lithium iron phosphate waste and slurry it. Add oxidant and react at 70-95℃ for 1-8h. Then filter to obtain lithium, iron and phosphorus leaching residue and sodium phosphate solution. The oxidant includes at least one of hydrogen peroxide, oxygen, air, and ozone; (2) Add water to the lithium, iron and phosphorus leaching residue, slurry it and add iron salt, react it at 70-90℃ for 3-5 hours and then filter it to obtain lithium solution and iron and phosphorus leaching residue; The iron salt includes at least one of ferric sulfate, ferric chloride, and ferric nitrate; (3) Add a precipitant to the lithium-containing solution, react at 85-95℃ for 1-3 hours, and then filter to obtain lithium salt; (4) Add sodium hydroxide solution to the iron and phosphorus leaching residue and react at 75-95℃ for 2-4 hours, then filter to obtain iron hydroxide and sodium phosphate solution; (5) Combine the sodium phosphate solution from step (1) with the sodium phosphate solution from step (4), and then evaporate and crystallize to obtain sodium phosphate crystals.

2. The method for recycling valuable elements in waste lithium iron phosphate cathode materials according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 2-6 mol / L.

3. The method for recycling valuable elements in waste lithium iron phosphate cathode materials according to claim 1, characterized in that, In step (1), the molar ratio of hydroxide ions in the sodium hydroxide solution to phosphate ions in the lithium iron phosphate waste is 2:1-2.4:

1.

4. The method for recycling valuable elements in waste lithium iron phosphate cathode materials according to claim 1, characterized in that, The molar ratio of iron ions in the iron salt to lithium ions in the lithium-containing, iron- and phosphorus-containing leaching residue is 3:1 to 3.6:

1.

5. The method for recycling valuable elements in waste lithium iron phosphate cathode materials according to claim 1, characterized in that, The precipitant is sodium carbonate or sodium phosphate.

6. The method for recycling valuable elements in waste lithium iron phosphate cathode materials according to claim 1, characterized in that, In step (4), the molar ratio of hydroxide ions in the sodium hydroxide solution to phosphate ions in the iron and phosphorus leaching residue is 3:1-3.3:1.

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