CN117509688A - An efficient full-component recycling method for waste lithium iron phosphate cathode materials - Google Patents

Abstract

The invention discloses an efficient recovery method of all components of waste lithium iron phosphate battery cathode materials. The cathode material is leached with acid and oxidant to obtain leachate and iron phosphate slag; the leachate is sequentially subjected to neutralization and impurity removal, deep impurity removal, evaporation and concentration. After precipitation and crystallization, industrial Li ₂ CO ₃ and carbon precipitation mother liquor are obtained. The lithium in the carbon precipitation mother liquor is extracted to obtain the raffinate and Li-containing stripping liquid. The raffinate is evaporated and crystallized to obtain sodium chloride crystals or sodium sulfate. Crystals and Li-containing stripping liquid are returned to the lithium precipitation process; concentrated alkali is added to the iron phosphorus slag, and the filtrate and filter residue are separated after stirring and leaching. The filter residue is roasted to obtain low-grade iron concentrate, and the filtrate is evaporated, concentrated, cooled, and crystallized after separation. Sodium phosphate crystals and excess lye are obtained. The invention realizes the efficient recovery of all components of waste lithium iron phosphate battery cathode materials, has the advantages of high lithium recovery rate, resource utilization of iron phosphate slag, and eliminates the output of secondary hazardous waste.

Description

An efficient full-component recycling method for waste lithium iron phosphate cathode materials

Technical field

The invention relates to the field of separation technology, specifically a method for efficient full-component recovery of waste lithium iron phosphate cathode materials.

Background technique

The existing recycling methods for lithium iron phosphate battery cathodes mainly include recycling and material element recovery. The recycling and reuse method is to reuse the repaired lithium iron phosphate as the battery cathode, and for element recovery, the lithium iron phosphate is leached by wet method. Then lithium, phosphorus and iron are recovered respectively.

The main method for recovering elements from lithium iron phosphate cathodes is wet recovery, using acid or alkaline solutions to leach metal ions and then recover them. The metal recovery rate of the fire method is not high during recycling, it consumes high energy and produces harmful gases, so it is generally not used for the recycling of lithium iron phosphate cathode materials. Wet recycling mainly includes acid leaching, acid dissolution-precipitation and mechanical activation treatment. The acid leaching method uses sulfuric acid, hydrochloric acid, phosphoric acid and citric acid to leach the cathode material. At the same time, an oxidant is added to oxidize the divalent iron in lithium iron phosphate to trivalent iron to generate iron phosphate. Lithium is present in the leachate in ionic form. After treatment, it is recovered in the form of lithium phosphate or lithium carbonate. The acid dissolution-precipitation rule is to completely dissolve the lithium iron phosphate positive electrode and then add different precipitants to separately precipitate and recover the elements. The mechanical activation treatment is to achieve the separation of lithium, phosphorus and iron by adding grinding aids (oxalic acid, EDTA-2Na, sodium chloride, etc.) after ball milling and activation in a ball mill.

Some small enterprises have carried out industrial production of lithium iron phosphate cathode material recycling, but only recycle the lithium in the cathode material. The main component of lithium iron phosphate, iron phosphate (content 95%), is not recycled and is discarded, resulting in a waste of resources. Most of the traditional lithium iron phosphate battery cathode material recycling only extracts lithium in the form of lithium carbonate, and the aluminum is stripped separately, and the remaining large amount of iron phosphate is wasted. The existing lithium iron phosphate cathode waste treatment method mainly extracts lithium cobalt oxide, trioxide It is borrowed from the positive electrode waste treatment method of Yuan batteries and so on. The existing lithium iron phosphate cathode material recycling technology has problems such as non-recovery of main components, large acid and alkali consumption, high cost, and wastewater discharge. Studies have shown that it is feasible to use waste iron phosphate as raw material to recover phosphorus, iron and lithium. However, due to the complexity of iron phosphate waste, it is difficult to guarantee the quality of iron phosphate materials directly synthesized from waste. If the precursor is directly synthesized, aluminum will be produced. The carrying affects material properties.

Contents of the invention

The purpose of the present invention is to provide an efficient full-component recycling method of waste lithium iron phosphate cathode materials, aiming to solve the problem of a large amount of iron phosphate being wasted in the existing recycling process of lithium iron phosphate cathode materials.

In order to achieve the above objectives, the invention proposes a full-component efficient recovery method of waste lithium iron phosphate cathode material, which includes the following steps:

(1) Add H ₂ O ₂ and hydrochloric acid or sulfuric acid to the positive and negative electrode powders obtained after dismantling, crushing, and screening retired lithium iron phosphate batteries, and filter to obtain the leachate and iron phosphorus slag;

(2.1) Add one or more of calcium oxide, calcium carbonate, sodium hydroxide or sodium carbonate to the leach solution in step (1) until the pH value is 7-8 to obtain a Li-containing crude solution and impurity-removing residue; Add sodium hydroxide to the Li-containing crude solution until the pH value is greater than 12 to obtain a purified solution and deep impurity removal residue; evaporate and concentrate the purified solution to obtain a concentrated solution;

(2.2) Add Na ₂ CO ₃ solution to the concentrated solution in step (2.1), and obtain industrial Li ₂ CO ₃ and carbon precipitation mother liquor through precipitation and crystallization separation;

(2.3) Use HBL-121 to extract, wash, and strip the lithium in the carbon precipitation mother liquor to obtain the raffinate and the lithium-containing strip liquid. The raffinate is evaporated and crystallized to obtain sodium chloride crystals or sodium sulfate crystals. The lithium-containing stripping solution is returned to step (2.2) for precipitation and crystallization;

(3) Add concentrated alkali to the ferrophosphorus slag in step (1), stir and leach to separate the filtrate and filter residue, roast the filter residue to obtain low-grade iron concentrate, evaporate, concentrate, cool and crystallize the filtrate to obtain sodium phosphate crystals and excess alkali solution, wherein the excess alkali solution is returned to leach iron phosphorus slag.

Preferably, the lithium ion content of the carbon precipitation mother liquor described in step (2.3) is 1-5g/L, and the sodium ion content is 10-80g/L.

Preferably, in the step (2.3), the pH value of the carbon precipitation mother liquor ranges from 10 to 14.

Preferably, in the step (2.3), the extraction ratio is O/A=3/1~3, and the extraction temperature is 25~45°C.

Preferably, in step (2.3), dilute sulfuric acid with a hydrogen ion concentration of 0.1-1 mol/L is used for washing, the washing ratio is O/A=5-20/1, and the washing temperature is 25-45°C.

Preferably, in the step (2.3), dilute sulfuric acid with a hydrogen ion concentration of 1 to 8 mol/L is used for stripping, the stripping ratio is O/A=8 to 25/1, and the stripping temperature is 25 ~45℃.

Preferably, hydrochloric acid with a hydrogen ion concentration of 0.1 to 1 mol/L is used for washing in step (2.3), the washing ratio is O/A=5 to 20/1, and the washing temperature is 25 to 45°C.

Preferably, during stripping in step (2.3), hydrochloric acid with a hydrogen ion concentration of 1 to 8 mol/L is used for a shaking reaction at room temperature with a ratio of O/A=8 to 25/1.

Preferably, the concentrated alkali in step (3) is a NaOH solution, and the concentration of NaOH is 0.5-10mol/L; the liquid-to-solid ratio during stirring and leaching is 4-6:1, and the temperature is 70-110°C. The time is 20min-6h.

Compared with the prior art, the beneficial technical effects of the present invention are:

1. The use of sodium hydroxide leaching-sodium phosphate low-temperature precipitation-alkali cycle realizes resource recovery of phosphorus and iron in phosphorus iron slag. Iron is converted into low-grade iron concentrate, and phosphorus is converted into industrial sodium phosphate.

2. The self-developed special lithium extraction agent HBL-121 is used to achieve efficient and deep separation of lithium and sodium under alkaline conditions, improve the recovery rate of lithium, and solve the industrial problem of difficult processing of carbon precipitation mother liquor.

3. The entire process realizes the full recovery of valuable elements in the lithium iron phosphate cathode material, eliminating the problem of stacking iron phosphate slag. The lithium recovery rate is high, and the lithium and sodium are completely separated, the amount of waste slag is greatly reduced, and the waste water is discharged to near zero. , is a typical low-cost, clean, efficient, energy-saving and emission-reducing production process.

Description of drawings

Figure 1 is a flow chart of an embodiment of the method for efficient recovery of all components of waste lithium iron phosphate battery cathode materials proposed by the present invention. If hydrogen peroxide and sulfuric acid are added to selectively extract lithium, then the lithium extraction will obtain a lithium sulfate solution. Evaporate and crystallize to obtain sodium sulfate crystals.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, ordinary skills in the art All other embodiments obtained by persons without creative efforts shall fall within the protection scope of the present invention.

Example 1

The material liquid is the simulated material liquid provided by Guangdong Fangyuan Company, containing lithium and sodium at 3.05g/L and 58.45g/L respectively. Add sodium hydroxide to adjust the pH to 13. The organic phase composition is 28% HBL-121, 72% sulfonated kerosene, the extraction agent is 0.5 mol/L sulfuric acid, the stripping agent is 4 mol/L sulfuric acid, and the backwashing agent is pure water. The process adopts 4-stage countercurrent extraction, 5-stage countercurrent extraction and washing, 2-stage countercurrent back-extraction, and 1-stage backwashing for continuous production testing in a mixing-clarification box-type extraction tank, and the flow rate is controlled by a peristaltic pump. The extraction, extraction, back-extraction and backwash ratios compared to O/A are 1/1, 10/1, 20/1 and 25/1 respectively. The results after 80 hours of continuous operation are as follows:

Table 1 HBL-121 continuous operation lithium extraction results

Example 2

Take 20g of phosphorus iron slag, use NaOH solutions of different concentrations with a liquid-to-solid ratio of 4:1, keep stirring at 90°C for 60 minutes, filter, and the filter residue is low-grade iron concentrate. Cool the filtrate to normal temperature, and a large number of crystals will precipitate. After filtering , the filter residue is sodium phosphate crystals, and the filtrate can be returned to leach iron phosphate residue after replenishing the consumed alkali. The phosphorus leaching rate changes with NaOH concentration and the results are as follows:

Table 2 Effect of sodium hydroxide concentration on phosphorus leaching rate

Example 3

Use sulfuric acid and hydrogen peroxide to leach the waste lithium iron phosphate battery cathode material to obtain iron phosphate slag and lithium-containing leachate.

In the leachate, use sodium hydroxide to adjust the pH to 7-8, filter to obtain the lithium-containing crude solution and the impurity removal residue, continue to add sodium hydroxide to the lithium-containing crude solution until the pH is greater than 12, and obtain the lithium-containing purified liquid and depth after filtration. After removing impurities, the lithium-containing purified liquid is evaporated and concentrated to obtain a lithium-containing concentrated liquid.

Add sodium carbonate solution to the lithium-containing concentrated solution, and precipitate and crystallize to obtain industrial lithium carbonate and carbon precipitation mother liquor.

HBL-121 is used to extract, wash and back-extract the lithium in the carbon precipitation mother liquor to obtain the raffinate and the lithium-containing strip liquid. The raffinate is evaporated and crystallized to obtain sodium chloride crystals or sodium sulfate crystals. The lithium-containing reaction solution The extract is returned to the lithium-containing concentrated solution for precipitation and crystallization;

Mix the ferrophosphate slag and deep impurity removal slag evenly, then add concentrated alkali, stir and leach, filter and separate while hot to obtain the filtrate and filter residue, roast the filter residue to obtain low-grade iron concentrate, evaporate, concentrate, cool and crystallize the filtrate to obtain sodium phosphate. Crystals and excess alkali solution, the excess alkali solution returns to leach phosphorus iron slag. The recovery rates of lithium, iron, and phosphorus are 99.24%, 97.53%, and 98.12% respectively.

The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited only to the above-mentioned embodiments. For those skilled in the art, improvements and transformations made without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims (7)

1. The method for efficiently recycling the full components of the waste lithium iron phosphate anode material is characterized by comprising the following steps of:

(1) Adding H into positive and negative electrode powder obtained after disassembly, crushing and screening of retired lithium iron phosphate battery ₂ O ₂ And, hydrochloric acid or sulfuric acid, filtering to obtain leaching liquid and ferrophosphorus slag;

(2.1) adding one or more of calcium oxide, calcium carbonate, sodium hydroxide or sodium carbonate into the leaching solution in the step (1) until the pH value is 7-8, so as to obtain a coarse solution containing Li and impurity-removing slag; adding sodium hydroxide into the Li-containing crude solution until the pH value is more than 12 to obtain a purified solution and deep impurity removal slag; evaporating and concentrating the purified solution to obtain a concentrated solution;

(2.2) adding Na to the concentrated solution in the step (2.1) ₂ CO ₃ Precipitating, crystallizing and separating the solution to obtain industrial Li ₂ CO ₃ A carbon precipitation mother liquor;

(2.3) extracting, washing and back-extracting lithium in the carbon precipitation mother liquor by adopting HBL-121 to obtain raffinate and lithium-containing back-extraction liquor, evaporating and crystallizing the raffinate to obtain sodium chloride crystals or sodium sulfate crystals, and returning the lithium-containing back-extraction liquor to the step (2.2) for precipitation and crystallization;

(3) Adding concentrated alkali into the ferrophosphorus slag in the step (1), stirring and leaching, separating to obtain filtrate and filter residue, roasting the filter residue to obtain low-grade iron concentrate, evaporating, concentrating, cooling, crystallizing and separating the filtrate to obtain sodium phosphate crystals and excessive alkali liquor, wherein the excessive alkali liquor returns to leaching the ferrophosphorus slag.

2. The method according to claim 1, wherein the lithium ion content in the carbon precipitation mother liquor in the step (2.3) is 1-5g/L, the pH is adjusted to 10-14, the extraction ratio is O/a=3/1-3, and the extraction temperature is 25-45 ℃.

3. The method according to claim 2, wherein the washing in step (2.3) is performed with dilute sulfuric acid having a hydrogen ion concentration of 0.1 to 1mol/L, the washing ratio is O/a=5 to 20/1, and the washing temperature is 25 to 45 ℃.

4. A method according to claim 3, wherein in the back extraction in step (2.3), dilute sulfuric acid having a hydrogen ion concentration of 1 to 8mol/L is used to perform the shaking reaction at room temperature in comparison with O/a=8 to 25/1.

5. The method according to claim 2, wherein the washing in step (2.3) is performed with hydrochloric acid having a hydrogen ion concentration of 0.1 to 1mol/L, the washing ratio is O/a=5 to 20/1, and the washing temperature is 25 to 45 ℃.

6. The method according to claim 5, wherein hydrochloric acid with a hydrogen ion concentration of 1-8 mol/L is used for the back extraction in the step (2.3) to perform the shaking reaction at room temperature in comparison with O/a=8-25/1.

7. The method according to claim 1, wherein the concentrated alkali in the step (3) is a NaOH solution, the concentration is 0.5-10mol/L, the liquid-solid ratio during stirring leaching is 4-6:1, the temperature is 70-110 ℃, and the leaching time is 20min-6h.