A method for selective lithium extraction and recycling from lithium iron phosphate waste

Abstract

This invention discloses a selective lithium extraction and recycling method for lithium iron phosphate waste, belonging to the field of waste lithium battery recycling. The chelating agent used in this invention involves an addition reaction between 1,5-diaminobiurea and sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate to obtain a bipyridine-containing biuret ligand, which can chelate trace amounts of lithium. This improves the lithium extraction rate, achieving a leaching rate as high as 99.53%.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling, specifically relating to a method for selectively extracting lithium from waste lithium iron phosphate. Background Technology

[0002] Lithium iron phosphate (LFP) is currently the most widely used lithium-ion battery material and is considered by many industry professionals to be the future direction of lithium battery development. Since the beginning of the 21st century, with the explosive growth of the lithium battery new energy market, the problem of disposing of used LFP batteries has become increasingly prominent, and their recycling has become a key research focus. Extracting lithium from used LFP batteries not only has high economic benefits but also reduces environmental pollution caused by waste batteries and resource extraction.

[0003] Currently, the main methods for recycling waste LiFePO4 include pyrometallurgy, hydrometallurgy, direct regeneration, mechanochemical methods, and electrochemical methods. For example, patent CN116646635A involves pulverizing pretreated ternary lithium battery cathode material, dispersing it in a solvent, and then heat-treating it to leach lithium ions while retaining transition metal elements in the solid material. The leachate is then evaporated, and lithium is recovered as lithium hydroxide. The solvent is one capable of providing a proton source.

[0004] Chinese patent application CN106910959A discloses a method for selectively recovering lithium from lithium iron phosphate waste. This system involves preparing a slurry from the lithium iron phosphate waste with an oxidant, while simultaneously adjusting the pH value with acid, controlling the pH to 2-11 to achieve selective lithium leaching. The oxidants used are persulfate, ozone, oxygen, hypochlorite, and hydrogen peroxide. This invention first adds an oxidant to prepare the slurry, then adds acid to adjust the pH, resulting in poor filtration of the resulting filter residue and low lithium leaching rate. In the reaction process, the oxidant is added prematurely; with the addition of acid, the leached iron is rapidly oxidized and precipitated, forming many fine crystal nuclei, resulting in nano-sized iron phosphate, leading to poor filtration.

[0005] Existing lithium extraction methods suffer from drawbacks such as high energy consumption, significant environmental pollution, and complex processes. There is an urgent need to develop environmentally friendly, high-recovery-rate, and mild-condition lithium extraction and recycling methods for waste lithium iron phosphate battery cathode materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for selectively extracting lithium from lithium iron phosphate waste, so as to solve the shortcomings of existing recycling methods such as high energy consumption, large environmental pollution and complex process.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides a method for selectively extracting lithium from lithium iron phosphate waste, comprising the following steps:

[0009] Lithium iron phosphate waste is slurried with water, then leaching agent and chelating agent are added for reaction; after the reaction, oxidant is added to continue the reaction, and after the reaction is completed, it is filtered to obtain lithium solution and iron phosphate slag;

[0010] The chelating agent is obtained by an amino-acrylic acid addition reaction of 1,5-diaminobiurea with sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate.

[0011] Lithium was selectively recovered from waste lithium iron phosphate electrode powder using an inorganic salt Fe2(SO4)3 leaching system and a Fe2(SO4)3-H2O2 system. The leaching agent is easy to recycle and reuse, and the resulting phosphorus iron slag is relatively pure.

[0012] Using waste lithium iron phosphate electrode powder as raw material, ferric sulfate as leaching agent, and 30% hydrogen peroxide as oxidant, a selective lithium recovery method under acid-free conditions was realized. The reaction mechanism equation is as follows:

[0013] 6LiFePO4+Fe2(SO4)3+3H2O2=6FePO4+3Li2SO4+2Fe2(OH)3.

[0014] Specifically, the chelating agent is prepared using the following method:

[0015] S1: Sodium hydroxide was added dropwise to (E)-3-([2,2′-bipyridin]-4-yl)acrylic acid until pH=7 to obtain sodium (E)-3-([2,2′-bipyridin]-4-yl)acrylate;

[0016] S2: 1,5-Diaminobiurea, sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, triethylamine, and DMF are placed in a stirred tank, nitrogen is introduced to replace the gas, and the mixture is stirred at 60-70°C for 1-3 hours. After the reaction is completed, DMF is removed by distillation to obtain the chelating agent.

[0017] Preferably, in S2, by weight, 15-30 parts of 1,5-diaminobiurea, 23-46 parts of sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, 2-6 parts of triethylamine, and 200-240 parts of DMF are used.

[0018] In some embodiments of the present invention, the liquid-to-solid ratio of lithium iron phosphate waste when mixed with water to form a slurry is 4.5-5.5:0.8-1.2.

[0019] In some embodiments of the present invention, by weight, there are 45-55 parts of lithium iron phosphate waste, 2-20 parts of leaching agent, 0.005-0.05 parts of chelating agent, and 10-30 parts of oxidant.

[0020] Specifically, the leaching agent has a mass percentage of 85%-90%.

[0021] The leaching agent is at least one of potassium sulfate, aluminum sulfate, ferric sulfate, and ferric chloride.

[0022] Specifically, the oxidant is sodium persulfate or hydrogen peroxide, and the mass percentage of the hydrogen peroxide is 30wt%-50wt%.

[0023] Specifically, the leaching agent and chelating agent are added and reacted at a temperature of 10-50℃ for 30-100 minutes, and the leaching time is 10-50 minutes.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The chelating agent of this invention involves an addition reaction between 1,5-diaminobiurea and sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate to obtain a bipyridine-containing biuret ligand, which can chelate trace amounts of lithium. This improves the lithium extraction rate, achieving a leaching rate as high as 99.53%. Detailed Implementation

[0026] The present invention will be described in detail below with reference to specific embodiments.

[0027] Experimental method: Weigh 50g of waste lithium iron phosphate electrode powder into a 500mL stirred tank, slurry it according to a certain liquid-to-solid ratio (volume mass ratio, L / S, unit is mL / g), add a certain amount of leaching agent, stir and react for a certain time, add oxidant to react, filter, wash the residue with water, dry the residue, use a Dion Aquion ion chromatograph to detect the content of Li and P in the leachate and residue, and calculate the Li leaching rate and P leaching rate according to the Li and P content in the leachate.

[0028] Leaching rate (E) = leaching amount (C) / amount of leached matter (M).

[0029] Example 1

[0030] 1. The preparation method of the chelating agent is as follows:

[0031] K1: Add 20wt% sodium hydroxide to 23g of (E)-3-([2,2′-bipyridin]-4-yl)acrylic acid until pH=7, and remove water by distillation to obtain sodium (E)-3-([2,2′-bipyridin]-4-yl)acrylate;

[0032] K2: Place 15g of 1,5-diaminobiurea, 23g of sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, 2g of triethylamine, and 200g of DMF in a stirred tank, purge with nitrogen to replace the gas, and stir at 60°C for 1 hour. After the reaction is complete, remove DMF by distillation to obtain the chelating agent.

[0033] 2. A method for selectively extracting lithium from lithium iron phosphate waste, comprising the following steps:

[0034] A. Weigh 45g of lithium iron phosphate electrode powder into a stirred tank; add water to make a slurry with a liquid-to-solid ratio of 4.5:0.8, add 10g of 85% potassium sulfate and 0.005g of chelating agent; leach for 30 minutes.

[0035] B. After stirring and reacting for 30 minutes at a water bath temperature of 10℃, add 10g of 30wt% hydrogen peroxide and react. Filter, wash the residue with water, dry the residue at 50℃, detect the metal content in the leachate and residue, and calculate the metal leaching rate.

[0036] The calculation results show that the leaching rate of Li is 94.09% and the leaching rate of P is 0, indicating that the selective leaching effect of Li is extremely significant.

[0037] Example 2

[0038] 1. The preparation method of the chelating agent is as follows:

[0039] K1: Add 24wt% sodium hydroxide to 28g of (E)-3-([2,2′-bipyridin]-4-yl)acrylic acid until pH=7, and remove water by distillation to obtain sodium (E)-3-([2,2′-bipyridin]-4-yl)acrylate;

[0040] K2: Place 18g of 1,5-diaminobiurea, 30g of sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, 5g of triethylamine, and 220g of DMF in a stirred tank, purge with nitrogen to replace the gas, and stir at 65°C for 2 hours. After the reaction is complete, remove DMF by distillation to obtain the chelating agent.

[0041] 2. A method for selectively extracting lithium from lithium iron phosphate waste, comprising the following steps:

[0042] A. Weigh 48g of lithium iron phosphate electrode powder into a stirred tank; add water to make a slurry with a liquid-to-solid ratio of 4.8:0.9, add 2g of 88% aluminum sulfate and 0.01g of chelating agent; leach for 40 minutes.

[0043] B. After stirring and reacting for 50 minutes at a water bath temperature of 30℃, add 15g of 35wt% hydrogen peroxide and react. Filter, wash the residue with water, dry the residue at 54℃, detect the metal content in the leachate and residue, and calculate the metal leaching rate.

[0044] The test results showed that the Li leaching rate was 97.19% and the p leaching rate was 0, indicating that the selective leaching effect of Li was extremely significant.

[0045] Example 3

[0046] 1. The preparation method of the chelating agent is as follows:

[0047] K1: Add 28wt% sodium hydroxide to 41g of (E)-3-([2,2′-bipyridin]-4-yl)acrylic acid until pH=7, and remove water by distillation to obtain sodium (E)-3-([2,2′-bipyridin]-4-yl)acrylate;

[0048] K2: 27g of 1,5-diaminobiurea, 40g of sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, 5g of triethylamine, and 230g of DMF were placed in a stirred tank, and nitrogen gas was introduced to replace the gas. The mixture was stirred at 68°C for 2.5h. After the reaction was completed, DMF was removed by distillation to obtain the chelating agent.

[0049] 2. A method for selectively extracting lithium from lithium iron phosphate waste, comprising the following steps:

[0050] A. Weigh 52g of lithium iron phosphate electrode powder into a stirred tank, add water at a liquid-to-solid ratio of 5.1:1 to make a slurry, add 18g of 88% ferric sulfate and 0.03g of chelating agent; the leaching time is 45min.

[0051] B. After stirring and reacting for 70 minutes at a water bath temperature of 40℃, add 26g of 50wt% hydrogen peroxide and react. Filter, wash the residue with water, dry the residue at 58℃, detect the metal content in the leachate and residue, and calculate the metal leaching rate.

[0052] The test results showed that the leaching rate of Li was 99.02%, and the leaching rate of P was 0, indicating that the selective leaching effect of Li was extremely significant.

[0053] Example 4

[0054] 1. The preparation method of the chelating agent is as follows:

[0055] K1: Add 30wt% sodium hydroxide to 46g of (E)-3-([2,2′-bipyridin]-4-yl)acrylic acid until pH=7, and remove water by distillation to obtain sodium (E)-3-([2,2′-bipyridin]-4-yl)acrylate;

[0056] K2: Place 30g of 1,5-diaminobiurea, 46g of sodium (E)-3-([2,2′-bipyridine]-4-yl)acrylate, 6g of triethylamine, and 240g of DMF in a stirred tank, purge with nitrogen to replace the gas, and stir at 70°C for 3 hours. After the reaction is complete, remove DMF by distillation to obtain the chelating agent.

[0057] 2. A method for selectively extracting lithium from lithium iron phosphate waste, comprising the following steps:

[0058] A. Weigh 55g of lithium iron phosphate electrode powder into a stirred tank; add water to make a slurry with a liquid-to-solid ratio of 5.5:1.2, add 20g of 90% ferric chloride and 0.05g of chelating agent; leach for 50 minutes.

[0059] B. After stirring and reacting at 50℃ for 100 min in a water bath, add 30g of sodium persulfate and react. Filter, wash the residue with water, dry the residue at 60℃, detect the metal content in the leachate and residue, and calculate the metal leaching rate.

[0060] The test results showed that the leaching rate of Li was 99.53%, the leaching rate of P was 0%, and the selective leaching effect of Li was extremely obvious.

[0061] Comparative Example 1

[0062] No chelating agent was added; otherwise, it was the same as in Example 1.

[0063] The test results showed that the Li leaching rate was 69.5% and the P leaching rate was 0.09%.

[0064] Comparative Example 2

[0065] Without adding 1,5-diaminobiurea, otherwise the same as in Example 1.

[0066] The test results showed that the Li leaching rate was 89.5% and the P leaching rate was 0.02%.

[0067] Comparative Example 3

[0068] (E)-3-([2,2′-bipyridine]-4-yl)acrylic acid was not added; otherwise, the same rules applied as in Example 1.

[0069] The test results showed that the Li leaching rate was 86.3% and the P leaching rate was 0.03%.

[0070] In summary, with the addition of a chelating agent, the leaching rate of this invention is 94.09%-99.53%, demonstrating an extremely significant selective leaching effect for Li.

Claims

1. A method for selectively extracting lithium from lithium iron phosphate waste, characterized in that, Includes the following steps: Lithium iron phosphate waste is slurried with water, then leaching agent and chelating agent are added for reaction; after the reaction, oxidant is added to continue the reaction, and after the reaction is completed, it is filtered to obtain lithium solution and iron phosphate slag; The chelating agent was obtained by an amino-acrylic acid addition reaction of 1,5-diaminobiurea with sodium (E)-3-([2,2'-bipyridine]-4-yl)acrylate. The leaching agent is at least one of potassium sulfate, aluminum sulfate, ferric sulfate, and ferric chloride.

2. The method for selective lithium extraction and recovery from lithium iron phosphate waste according to claim 1, characterized in that, The specific preparation method of the chelating agent is as follows: S1: Sodium hydroxide was added dropwise to (E)-3-([2,2'-bipyridin]-4-yl)acrylic acid until pH=7 to obtain sodium (E)-3-([2,2'-bipyridin]-4-yl)acrylate; S2: 1,5-Diaminobiurea, sodium (E)-3-([2,2'-bipyridine]-4-yl)acrylate, triethylamine, and DMF are placed in a stirred tank, nitrogen is introduced to replace the gas, and the mixture is stirred at 60-70°C for 1-3 hours. After the reaction is completed, DMF is removed by distillation to obtain the chelating agent.

3. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 2, characterized in that, In S2, by weight, 15-30 parts of 1,5-diaminobiurea, 23-46 parts of sodium (E)-3-([2,2'-bipyridine]-4-yl)acrylate, 2-6 parts of triethylamine, and 200-240 parts of DMF are used.

4. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 1, characterized in that, The liquid-to-solid ratio when lithium iron phosphate waste is mixed with water to form a slurry is 4.5-5.5:0.8-1.

2.

5. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 1, characterized in that, By weight, 45-55 parts lithium iron phosphate waste, 2-20 parts leaching agent, 0.005-0.05 parts chelating agent, and 10-30 parts oxidizing agent.

6. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 1, characterized in that, The mass percentage of the leaching agent is 85%-90%.

7. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 1, characterized in that, The oxidant is sodium persulfate or hydrogen peroxide. The mass percentage of the hydrogen peroxide is 30wt%-50wt%.

8. The method for selectively extracting lithium from lithium iron phosphate waste according to claim 1, characterized in that, Then add the leaching agent and chelating agent, and react at a temperature of 10-50℃ for 30-100 minutes. The leaching time after adding the leaching agent is 10-50 minutes.