Method for preparing high-purity lithium carbonate through electrolysis of HMnxFe1-xPO4 type lithium ion exchange membrane

Abstract

The invention relates to the technical field of lithium carbonate refining, in particular to a method for preparing high-purity lithium carbonate through electrolysis of an HMnxFe1-xPO4 type lithium ion exchange membrane. The method comprises the following steps: carrying out acid elution on a waste lithium manganese iron phosphate battery positive electrode material LiMnxFe1-xPO4 to obtain a lithium ion sieve HMnxFe1-xPO4; washing the lithium ion sieve with water, drying, grinding to 300 meshes, mixing with linear low-density polyethylene, polyisobutene, an antioxidant and calcium stearate, performing sheet pulling, and performing enhanced hot pressing with nylon mesh cloth to obtain an HMnxFe1-xPO4 type lithium ion exchange membrane; electrolyzing the lithium chloride solution by using an HMnxFe1-xPO4 type lithium ion exchange membrane to prepare a high-purity lithium hydroxide solution; and carbonizing, cleaning, drying and grinding the high-purity lithium hydroxide solution to obtain the final product high-purity lithium carbonate, wherein the purity of the high-purity lithium carbonate can reach 99.995%.

Description

Technical Field

[0001] This invention relates to the field of lithium carbonate refining technology, specifically to a HMn x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane. Background Technology

[0002] Lithium carbonate is the most important lithium salt among lithium compounds and is the main raw material for preparing other high-purity lithium compounds and lithium alloys. Since the beginning of the 21st century, with the rapid development of the information industry, high-purity lithium carbonate with a purity greater than 99.9% has received increasing attention as a cathode material and electrolyte raw material for lithium-ion batteries.

[0003] Ion-exchange membrane electrolysis is a commonly used method for preparing lithium carbonate. After treatment with a cation exchange resin or chelating resin, the polyvalent cations in the crude lithium salt solution are adsorbed and removed, yielding a high-purity lithium salt solution. Using the high-purity lithium salt solution as the anolyte and the lithium hydroxide solution as the catholyte, separated by a cation exchange membrane, the high-purity lithium hydroxide produced by electrolysis is carbonized with carbon dioxide to obtain lithium carbonate precipitate. After washing, drying, and grinding, the final product, high-purity lithium carbonate, is obtained. However, this method requires pretreatment with ion exchange resin, and the resin needs regeneration after adsorption saturation. This not only increases the complexity of the process but also generates a certain amount of waste acid and alkali. Furthermore, during ion-exchange membrane electrolysis, monovalent cations such as sodium and potassium also enter the catholyte along with the lithium ions, resulting in impurities such as sodium hydroxide and potassium hydroxide in the lithium hydroxide product, ultimately affecting the purity of the lithium carbonate product.

[0004] Therefore, there is an urgent need to develop a new ion-exchange membrane electrolysis method to improve the purity of lithium carbonate products while reducing the complexity of the process. Summary of the Invention

[0005] The purpose of this invention is to develop an HMn x Fe 1-x The PO4-type lithium-ion exchange membrane electrolysis method was applied to the preparation of high-purity lithium carbonate, which improved the purity of lithium carbonate products while reducing the complexity of the process.

[0006] The technical solution of the present invention is as follows:

[0007] (1) Discharge and disassemble the waste lithium manganese iron phosphate batteries to extract the positive electrode material LiMn. x Fe 1-x PO4; The above cathode material was added to 0.5-0.6 mol / L hydrochloric acid and stirred at room temperature for 24-30 h to obtain lithium-ion sieve HMn. x Fe 1-xPO4; After washing and drying the above lithium ion sieve, grind it to 300 mesh for later use.

[0008] (2) According to lithium ion sieve HMn x Fe 1-x The mixture contains 66%–69% PO4, 23%–26% linear low-density polyethylene, 6% polyisobutylene, 0.4% antioxidant, and 1.6% calcium stearate. First, the linear low-density polyethylene and polyisobutylene are added to a mixer and mixed evenly. Then, lithium-ion sieve HMn is added. x Fe 1-x PO4, antioxidant, and calcium stearate are further mixed until homogeneous; the mixture is then added to a two-roll mill for sheeting to obtain a 0.4 mm thick film; a layer of 60-mesh nylon mesh is added to both sides of the film, and the film is hot-pressed in a hot press to form a film. After cooling, the finished product HMn is obtained. x Fe 1-x PO4 type lithium ion exchange membrane.

[0009] (3) A 22.6% lithium chloride solution was prepared using crude lithium chloride as the anolyte, and a 0.1% lithium hydroxide solution was prepared using 99.9% high-purity lithium hydroxide as the catholyte. HMn was used to separate the two solutions. x Fe 1-x PO4 type lithium-ion exchange membrane separates the ions; during electrolysis, Li in the anolyte... + via HMn x Fe 1-x The PO4-type lithium-ion exchange membrane enters the catholyte and reacts with OH- ions generated by the electrolysis of water molecules in the catholyte. - The resulting LiOH solution yields a 12.8% lithium hydroxide solution in the catholyte; the anolyte after electrolysis is reused to prepare a lithium chloride solution.

[0010] (4) The above 12.8% lithium hydroxide solution is carbonized with carbon dioxide to obtain lithium carbonate precipitate, which is then washed, dried and ground to obtain the final product, high-purity lithium carbonate, with a purity of up to 99.995%.

[0011] Specifically, the mixing and open mixing temperatures are controlled at 140–145℃, the hot pressing temperature is controlled at 125–135℃, and the hot pressing pressure is controlled at 13–14MPa.

[0012] Among them: HMn x Fe 1-x PO4 type lithium-ion exchange membrane is a cation exchange membrane, because lithium ion sieve HMn x Fe 1- x The presence of PO4 allows only lithium ions to pass through; other cations and anions cannot pass through the membrane.

[0013] Among them: Li+ +HMn x Fe 1-x PO4=LiMn x Fe 1-x PO4+H + and Li + +LiMn x Fe 1-x PO4=LiMn x Fe 1-x PO4+Li + HMn x Fe 1-x The reaction equation for PO4 type lithium ion exchange membrane.

[0014] Wherein: 2Cl - -2e - =Cl2↑ is the reaction equation for the anode.

[0015] Where: 2H₂O + 2e - =H2↑ + 2OH - and OH - +Li + =LiOH is the reaction equation for the cathode.

[0016] Wherein: 2LiOH+CO2=Li2CO3↓+H2O is the carbonization reaction equation for lithium hydroxide.

[0017] The beneficial effects of this invention are: the prepared HMn x Fe 1-x The PO4 type lithium-ion exchange membrane only allows lithium ions to pass through, while other cations and anions cannot pass through the membrane; the process is simpler and does not require additional ion exchange resin pretreatment of the lithium salt solution; the purity of lithium carbonate products can reach 99.995%; and it can realize the secondary utilization of waste manganese iron phosphate battery cathode materials. Detailed Implementation

[0018] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but this is not intended to limit the present invention.

[0019] Example 1:

[0020] (1) Discharge and disassemble the waste lithium manganese iron phosphate batteries to extract the positive electrode material LiMn. x Fe 1-x PO4; The above cathode material was added to 0.5 mol / L hydrochloric acid and stirred at room temperature for 30 h to obtain lithium-ion sieve HMn. x Fe 1-x PO4; After washing and drying the above lithium ion sieve, grind it to 300 mesh for later use.

[0021] (2) According to lithium ion sieve HMn x Fe 1-x The mixture contains 66% PO4, 26% linear low-density polyethylene, 6% polyisobutylene, 0.4% antioxidant, and 1.6% calcium stearate. First, the linear low-density polyethylene and polyisobutylene are mixed evenly in a mixer at 140°C. Then, lithium-ion sieve HMn is added. x Fe 1-x PO4, antioxidant, and calcium stearate were further mixed at 140°C until homogeneous; the mixture was then added to a two-roll mill and stretched at 140°C to obtain a film with a thickness of 0.4 mm; a layer of 60-mesh nylon mesh was added to both sides of the film, and the film was then hot-pressed at 125°C and 14 MPa in a hot press to form a film. After cooling, the finished product HMn was obtained. x Fe 1-x PO4 type lithium ion exchange membrane.

[0022] (3) A 22.6% lithium chloride solution was prepared using crude lithium chloride as the anolyte, and a 0.1% lithium hydroxide solution was prepared using 99.9% high-purity lithium hydroxide as the catholyte. HMn was used to separate the two solutions. x Fe 1-x PO4 type lithium-ion exchange membrane separates the ions; during electrolysis, Li in the anolyte... + via HMn x Fe 1-x The PO4-type lithium-ion exchange membrane enters the catholyte and reacts with OH- ions generated by the electrolysis of water molecules in the catholyte. - The resulting LiOH solution yields a 12.8% lithium hydroxide solution in the catholyte; the anolyte after electrolysis is reused to prepare a lithium chloride solution.

[0023] (4) The above 12.8% lithium hydroxide solution is carbonized with carbon dioxide to obtain lithium carbonate precipitate, which is then washed, dried and ground to obtain the final product, high-purity lithium carbonate, with a purity of up to 99.995%.

[0024] Example 2:

[0025] (1) Discharge and disassemble the waste lithium manganese iron phosphate batteries to extract the positive electrode material LiMn. x Fe 1-x PO4; The above cathode material was added to 0.6 mol / L hydrochloric acid and stirred at room temperature for 24 h to obtain lithium-ion sieve HMn. x Fe 1-x PO4; After washing and drying the above lithium ion sieve, grind it to 300 mesh for later use.

[0026] (2) According to lithium ion sieve HMn x Fe 1-xThe mixture contains 69% PO4, 23% linear low-density polyethylene, 6% polyisobutylene, 0.4% antioxidant, and 1.6% calcium stearate. First, the linear low-density polyethylene and polyisobutylene are added to a mixer and mixed evenly at 145°C. Then, lithium-ion sieve HMn is added. x Fe 1-x PO4, antioxidant, and calcium stearate were further mixed at 145°C until homogeneous; the mixture was then added to a two-roll mill and stretched at 145°C to obtain a film with a thickness of 0.4 mm; a layer of 60-mesh nylon mesh was added to both sides of the film, and the film was then hot-pressed at 135°C and 13 MPa in a hot press to form a film. After cooling, the finished product HMn was obtained. x Fe 1-x PO4 type lithium ion exchange membrane.

[0027] (3) A 22.6% lithium chloride solution was prepared using crude lithium chloride as the anolyte, and a 0.1% lithium hydroxide solution was prepared using 99.9% high-purity lithium hydroxide as the catholyte. HMn was used to separate the two solutions. x Fe 1-x PO4 type lithium-ion exchange membrane separates the ions; during electrolysis, Li in the anolyte... + via HMn x Fe 1-x The PO4-type lithium-ion exchange membrane enters the catholyte and reacts with OH- ions generated by the electrolysis of water molecules in the catholyte. - The resulting LiOH solution yields a 12.8% lithium hydroxide solution in the catholyte; the anolyte after electrolysis is reused to prepare a lithium chloride solution.

[0028] (4) The above 12.8% lithium hydroxide solution is carbonized with carbon dioxide to obtain lithium carbonate precipitate, which is then washed, dried and ground to obtain the final product, high-purity lithium carbonate, with a purity of up to 99.995%.

Claims

1. The present invention provides a method for preparing high purity lithium carbonate by HMn x Fe 1-x PO4 type lithium ion exchange membrane electrolysis, characterized in that: (1) Discharge and disassemble the waste manganese iron lithium phosphate battery, take out the positive material LiMn x Fe 1-x PO4; add the positive material to 0.5-0.6 mol / L hydrochloric acid, stir at room temperature for 24-30 h to obtain lithium ion sieve HMn x Fe 1-x PO4; wash and dry the lithium ion sieve, and grind to 300 mesh for use. (2) According to lithium ion sieve HMn x Fe 1-x The mixture contains 66%–69% PO4, 23%–26% linear low-density polyethylene, 6% polyisobutylene, 0.4% antioxidant, and 1.6% calcium stearate. First, the linear low-density polyethylene and polyisobutylene are added to a mixer and mixed evenly. Then, lithium-ion sieve HMn is added. x Fe 1-x PO4, antioxidant, and calcium stearate are further mixed until homogeneous; the mixture is then added to a two-roll mill for sheeting to obtain a 0.4 mm thick film; a layer of 60-mesh nylon mesh is added to both sides of the film, and the film is hot-pressed in a hot press to form a film. After cooling, the finished product HMn is obtained. x Fe 1-x PO4 type lithium ion exchange membrane. (3) A 22.6% lithium chloride solution was prepared using crude lithium chloride as the anolyte, and a 0.1% lithium hydroxide solution was prepared using 99.9% high-purity lithium hydroxide as the catholyte. HMn was used to separate the two solutions. x Fe 1-x PO4 type lithium-ion exchange membrane separates the ions; during electrolysis, Li in the anolyte... + via HMn x Fe 1-x The PO4-type lithium-ion exchange membrane enters the catholyte and reacts with OH- ions generated by the electrolysis of water molecules in the catholyte. - The resulting LiOH solution yields a 12.8% lithium hydroxide solution in the catholyte; the anolyte after electrolysis is reused to prepare a lithium chloride solution. (4) The above 12.8% lithium hydroxide solution is carbonized with carbon dioxide to obtain lithium carbonate precipitate, which is then washed, dried and ground to obtain the final product, high-purity lithium carbonate, with a purity of up to 99.995%.

2. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: The mixing and open mixing temperatures are controlled at 140–145℃, the hot pressing temperature is controlled at 125–135℃, and the hot pressing pressure is controlled at 13–14MPa.

3. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: HMn x Fe 1-x PO4 type lithium-ion exchange membrane is a cation exchange membrane, because lithium ion sieve HMn x Fe 1- x The presence of PO4 allows only lithium ions to pass through; other cations and anions cannot pass through the membrane.

4. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: Li + +HMn x Fe 1-x PO4=LiMn x Fe 1-x PO4+H + and Li + +LiMn x Fe 1-x PO4=LiMn x Fe 1-x PO4+Li + HMn x Fe 1-x The reaction equation for PO4 type lithium ion exchange membrane.

5. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: 2Cl - -2e - =Cl2↑ is the reaction equation for the anode.

6. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: 2H2O+2e - =H2↑ + 2OH - and OH - +Li + =LiOH is the reaction equation for the cathode.

7. An HMn according to claim 1 x Fe 1-x A method for preparing high-purity lithium carbonate by electrolysis using a PO4-type lithium-ion exchange membrane, characterized in that: 2LiOH + CO2 = Li2CO3↓ + H2O is the carbonization reaction equation for lithium hydroxide.