CN115947323A

CN115947323A - Method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate

Info

Publication number: CN115947323A
Application number: CN202211638999.3A
Authority: CN
Inventors: 张岩岩; 岳海峰; 王曼; 郭欢; 王杰; 范浩
Original assignee: Lithium Source Shenzhen Scientific Research Co ltd
Current assignee: Lithium Source Shenzhen Scientific Research Co ltd
Priority date: 2022-12-20
Filing date: 2022-12-20
Publication date: 2023-04-11

Abstract

The invention provides a method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate, which comprises the following steps: s1, calcining waste lithium iron phosphate battery powder for 2-10 hours at 400-600 ℃ under the condition of oxygen; s2, adding inorganic acid and an oxidant into the calcined lithium iron phosphate powder, and stirring and reacting for 0.5-3 hours at the temperature of 30-60 ℃ to form mixed slurry, wherein the weight ratio of lithium iron phosphate: the inorganic acid: the molar ratio of the oxidant is 2 (0.5-1.5) to 0.5-2.5; s3, filtering the mixed slurry, wherein the filtrate is used for extracting lithium, and the filter residue is used for preparing iron phosphate; s4, adding a copper removing agent into the filter residue, and circularly grinding and reacting for 0.5-3 hours at the temperature of 30-60 ℃ to obtain iron phosphate slurry, wherein the copper removing agent is a mixture of ammonia water and ammonium salt, and the molar ratio of ammonium ions to copper in the mixture is (3-6); and S5, filtering the iron phosphate slurry to obtain iron phosphate filter residues, washing the iron phosphate filter residues with water, and aging, drying and calcining the iron phosphate filter residues to obtain the battery-grade iron phosphate.

Description

Method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate

Technical Field

The invention belongs to the technical field of new energy lithium ion battery recovery, and particularly relates to a method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate.

Background

With the rapid development of the new energy automobile industry, the output of the lithium ion battery is greatly increased, the lithium ion battery is represented by a lithium iron phosphate (LiFePO 4) battery, when the service life of the battery is over, a large amount of waste lithium ion batteries are inevitably generated, if the battery is not properly treated, negative effects on the environment can be caused, and if the battery can be recycled, the problem of environmental pollution can be solved, and economic benefits can also be generated. Therefore, the recovery of LiFePO4 lithium ion batteries has great practical and economic value.

At present, the method for recovering the waste LiFePO4 lithium ion battery mainly separates and recovers different elements in the LiFePO4 lithium ion battery to finally obtain battery-grade iron phosphate, and the process relates to the removal of impurity copper.

CN110112481B discloses a method for preparing a lithium iron phosphate cathode material by recycling waste lithium iron phosphate batteries, which comprises the steps of adding an alkaline substance into an acid leaching solution, adjusting the pH value to 0-3, and adding a vulcanizing agent to remove impurity copper. CN114655969A also uses the scheme of adding a vulcanizing agent into the pickle liquor to remove copper.

CN111009660A discloses a method for preparing a lithium iron phosphate positive electrode material from waste lithium iron phosphate batteries, which comprises the steps of pickling the waste lithium iron phosphate batteries, filtering filter residues, and directly adding iron powder into the pickling solution for replacement to remove copper.

CN111646447B discloses a method for recovering iron phosphate from iron phosphorus slag after lithium extraction of a lithium iron phosphate battery, which comprises the steps of mixing the iron phosphorus slag after lithium extraction of the lithium iron phosphate battery with water, mixing the mixture with slurry, reacting the mixture with acid, carrying out solid-liquid separation to obtain leachate containing iron and phosphorus ions, and then adding iron to replace the leachate to remove copper.

However, the existing copper removal technology is basically carried out in an acid immersion environment, so that iron loss is easily caused, and the recovery of iron phosphate is incomplete.

Disclosure of Invention

Therefore, the invention provides the waste lithium iron phosphate lithium extraction method and the iron phosphate preparation method which do not need to remove copper in an acid leaching environment, so that the loss of iron and phosphorus in the copper removing process is reduced, and the recovery rate is improved.

The invention provides a method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate, which comprises the following steps: s1, calcining waste lithium iron phosphate battery powder for 2-10 hours at 400-600 ℃ under the condition of oxygen; s2, adding inorganic acid and an oxidant into the calcined lithium iron phosphate powder, and stirring and reacting for 0.5-3 hours at the temperature of 30-60 ℃ to form mixed slurry, wherein the weight ratio of lithium iron phosphate: the inorganic acid: the molar ratio of the oxidant is 2 (0.5-1.5) to 0.5-2.5; s3, filtering the mixed slurry, wherein the filtrate is used for extracting lithium, and the filter residue is used for preparing iron phosphate; s4, adding a copper removing agent into the filter residue, and performing circulating grinding reaction for 0.5-3 h at the temperature of 30-60 ℃ to obtain iron phosphate slurry, wherein the copper removing agent is a mixture of ammonia water and ammonium salt, and the molar ratio of ammonium ions to copper in the mixture is 3-6; and S5, filtering the iron phosphate slurry to obtain iron phosphate filter residues, washing the iron phosphate filter residues with water, and aging, drying and calcining the iron phosphate filter residues to obtain the battery-grade iron phosphate.

Preferably, in step S2, the inorganic acid is one or more of sulfuric acid, hydrochloric acid, and nitric acid, and the oxidant is hydrogen peroxide or sodium thiosulfate.

Preferably, in the step S3, during the lithium extraction process, phosphate is added to the filtrate to prepare lithium phosphate.

Preferably, in step S4, the ammonium salt is one or more of ammonium carbonate, ammonium sulfate, ammonium chloride, ammonium phosphate and ammonium nitrate.

Preferably, in the step S4, the grinding is ball milling or sand milling.

Preferably, in the step S4, the molar ratio of the ammonium ions to the ammonia water is 2:3.

preferably, in the step S5, the calcining temperature is 500-800 ℃, and the calcining time is 2-8h.

The method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate provided by the invention has the following beneficial effects: 1. the lithium extraction process controls the dosage of acid and oxidant, can ensure complete leaching of lithium, and simultaneously avoids leaching of other metals, particularly iron, so as to avoid iron loss and influence on lithium extraction purity, and improve recovery rates of lithium and iron phosphate. 2. Copper is directly removed from the filter residue after lithium extraction, instead of being carried out in an acid immersion environment, so that iron loss in the copper removal process is further avoided. 3. In the copper removing process, the reaction is quicker and more sufficient by circulating grinding, and the copper removing effect is improved. 4. The recovery process flow is simple, the production cost is low, and the environment is friendly.

Detailed Description

The technical solution of the present invention is further described below by way of specific embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The invention provides a method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate, which comprises the steps of S1-S5.

S1, calcining the waste lithium iron phosphate battery powder for 2-10 hours at 400-600 ℃ under the condition of oxygen, thereby removing coated carbon, a conductive agent and the like. The waste lithium iron phosphate battery powder can be calcined in an air environment.

S2, adding inorganic acid and an oxidant into the calcined lithium iron phosphate powder, and stirring and reacting for 0.5-3 hours at the temperature of 30-60 ℃ to form mixed slurry, wherein the weight ratio of lithium iron phosphate: the inorganic acid: the molar ratio of the oxidant is 2 (0.5-1.5) to 0.5-2.5.

The inorganic acid is one or more of sulfuric acid, hydrochloric acid and nitric acid, and the oxidant is hydrogen peroxide or sodium thiosulfate.

And S3, filtering the mixed slurry, wherein the filtrate is used for extracting lithium, and the filter residue is used for preparing iron phosphate.

And adding phosphate into the filtrate in the lithium extraction process of the filtrate to prepare lithium phosphate.

S4, adding a copper removing agent into the filter residue, and carrying out circulating grinding reaction for 0.5-3 h at the temperature of 30-60 ℃ to obtain iron phosphate slurry, wherein the copper removing agent is a mixture of ammonia water and ammonium salt, and the molar ratio of ammonium ions to copper in the mixture is 3-6.

The ammonium salt in the copper removing agent is one or more of ammonium carbonate, ammonium sulfate, ammonium chloride, ammonium phosphate and ammonium nitrate. The grinding is ball milling or sanding. The molar ratio of the ammonium ions to the ammonia water is 2:3. most preferably, the ammonium salt is ammonium sulfate, and the molar ratio of the ammonium sulfate to the ammonia water is 1:3.

and S5, filtering the iron phosphate slurry to obtain iron phosphate filter residues, washing the iron phosphate filter residues with water, and aging, drying and calcining the iron phosphate filter residues to obtain the battery-grade iron phosphate. The battery-grade iron phosphate can be used for preparing a precursor of a lithium iron phosphate positive electrode material. The calcining temperature is 500-800 ℃, and the calcining time is 2-8h.

The index results of the iron phosphate prepared by the method provided by the invention are shown in table 1, and as can be seen from table 1, the iron phosphate prepared by the embodiment of the invention has the Cu content of 1ppm, and the specific surface, the median diameter D50, the tap density and the water content of the iron phosphate reach the battery level.

TABLE 1

The applicant states that the present invention is illustrated by the above examples to show the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be carried out. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A method for extracting lithium from waste lithium iron phosphate and preparing iron phosphate is characterized by comprising the following steps:

s1, calcining waste lithium iron phosphate battery powder for 2-10 hours at 400-600 ℃ under the condition of oxygen;

s2, adding inorganic acid and an oxidant into the calcined lithium iron phosphate powder, and stirring and reacting for 0.5-3 hours at the temperature of 30-60 ℃ to form mixed slurry, wherein the weight ratio of the lithium iron phosphate: the inorganic acid: the molar ratio of the oxidant is 2 (0.5-1.5) to 0.5-2.5;

s3, filtering the mixed slurry, wherein the filtrate is used for extracting lithium, and the filter residue is used for preparing iron phosphate;

s4, adding a copper removing agent into the filter residue, and performing circulating grinding reaction for 0.5-3 h at the temperature of 30-60 ℃ to obtain iron phosphate slurry, wherein the copper removing agent is a mixture of ammonia water and ammonium salt, and the molar ratio of ammonium ions to copper in the mixture is 3-6;

and S5, filtering the iron phosphate slurry to obtain iron phosphate filter residues, washing the iron phosphate filter residues with water, and aging, drying and calcining the iron phosphate filter residues to obtain the battery-grade iron phosphate.

2. The method according to claim 1, wherein in the step S2, the inorganic acid is one or more of sulfuric acid, hydrochloric acid and nitric acid, and the oxidant is hydrogen peroxide or sodium thiosulfate.

3. The method according to claim 1, wherein the filtrate in the step S3 is added with phosphate during lithium extraction to prepare lithium phosphate.

4. The method according to claim 1, wherein in the step S4, the ammonium salt is one or more of ammonium carbonate, ammonium sulfate, ammonium chloride, ammonium phosphate and ammonium nitrate.

5. The method of claim 1, wherein in the step S4, the grinding is ball milling or sand milling.

6. The method according to claim 1, wherein in step S4, the molar ratio of ammonium ions to ammonia water is 2:3.

7. the method of claim 1, wherein in step S5, the calcination temperature is 500-800 ℃ and the calcination time is 2-8h.