阅读说明：本技术 从退役电池中选择性提锂的方法及其应用 (Method for selectively extracting lithium from retired battery and application thereof ) 是由 李波 李长东 阮丁山 陈若葵 乔延超 包冬莲 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种从退役电池中选择性提锂的方法及其应用,该方法基于二价锰离子和锂离子之间的离子交换作用,将正极材料和二价锰盐以一定比例混合并制备成浆料,通过球磨过程使二价锰盐和正极材料充分混合,有效地破坏了正极材料的晶格结构,以此降低二价锰离子和锂离子交换的活化能,大大降低了后续提锂过程所需的反应能,将球磨后的混料在较低温度下进行焙烧,使得锰盐中的二价锰占据层状结构中的锂位,直接进行锰锂置换,得到单纯的含锂浸出液,本法极大地提高了锂的浸出率和选择性。本发明采用先球磨混料再焙烧的方式,能耗低,安全性高,锂的浸出率和选择性优良,具有极大的应用前景。(The invention discloses a method for selectively extracting lithium from a retired battery and application thereof, the method is based on the ion exchange effect between bivalent manganese ions and lithium ions, a positive electrode material and bivalent manganese salts are mixed according to a certain proportion and prepared into slurry, the bivalent manganese salts and the positive electrode material are fully mixed through a ball milling process, the lattice structure of the positive electrode material is effectively destroyed, so that the activation energy of the bivalent manganese ions and the lithium ions for exchange is reduced, the reaction energy required in the subsequent lithium extraction process is greatly reduced, the mixed material after ball milling is roasted at a lower temperature, the bivalent manganese in the manganese salts occupies the lithium position in a layered structure, and the manganese and the lithium are directly replaced, so that a pure lithium-containing leachate is obtained, and the leaching rate and the selectivity of the lithium are greatly improved. The invention adopts a mode of firstly ball-milling and mixing materials and then roasting, has low energy consumption, high safety and excellent leaching rate and selectivity of lithium, and has great application prospect.)

1. A method for selectively extracting lithium from a decommissioned battery, comprising the steps of:

s1: mixing a lithium battery positive electrode material and divalent manganese salt, adding a solvent to prepare slurry, and carrying out ball milling on the slurry to obtain a ball-milled mixed material;

s2: roasting the ball-milling mixed material to obtain a roasted product;

s3: and adding a leaching agent into the roasted product for leaching to obtain a lithium-rich leaching solution.

2. The method of claim 1, wherein in step S1, the lithium battery positive electrode material is at least one of lithium manganate, lithium cobaltate, lithium nickel cobalt manganate or lithium nickel cobalt aluminate.

3. The method of claim 1, wherein in step S2, the solvent is at least one of water, a hydrochloric acid solution, a sulfuric acid solution, a manganese nitrate solution or a manganese sulfate solution.

4. The method as claimed in claim 1, wherein the solid-to-liquid ratio of the slurry in step S2 is 500-5000 g/L.

5. The method according to claim 1, wherein in step S2, the manganous salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese phosphate, manganese acetate, manganese oxalate or manganese acetylacetonate.

6. The method according to claim 1, wherein in step S2, the molar ratio of manganese ions in the manganous salt to lithium ions in the positive electrode material (0.1-2): 1.

7. the method of claim 1, wherein in step S2, the ball milling has a ball-to-material ratio of (1-100): 1, the rotation speed of ball milling is 200 and 1200rpm, and the ball milling time is 0.5-8 h.

8. The method as claimed in claim 1, wherein in step S3, the baking temperature is 200 ℃ to 800 ℃, the heating rate is 1-20 ℃/min, and the baking time is 1-12 h.

9. The method of claim 1, wherein in step S4, the leaching agent is at least one of water, a carbonic acid solution, a sulfuric acid solution, a hydrochloric acid solution or a sodium hydroxide solution.

10. Use of a process according to any one of claims 1 to 9 for the preparation of a lithium salt.

Technical Field

The invention belongs to the technical field of retired battery recycling, and particularly relates to a method for selectively extracting lithium from retired batteries and application of the method.

Background

With the increasing approach of carbon neutralization targets, a new energy market develops vigorously, the prospect is unlimited, and lithium ion batteries are outstanding in the current energy market. However, the life of the lithium ion battery is only 3-5 years, and as more and more lithium batteries enter the end-of-life period, the reasonable and effective treatment of the retired batteries becomes an inevitable requirement for environmental protection and sustainable resource development.

At present, the recovery method of the retired lithium battery is mainly divided into a wet process route and a fire process route, however, both the wet process metallurgy and the fire process metallurgy intensively and preferentially recover the valuable metals such as nickel, cobalt, manganese and the like in the battery, and the lithium with lower content is often placed at the tail end of the process for treatment, so that the loss of the lithium is serious, and the recovery rate is extremely low. Therefore, how to selectively extract lithium from the retired battery becomes a difficult problem to be solved in the field. The technical routes currently studied include: carbon reduction, aluminothermic reduction, sulfate roasting, high-temperature high-pressure acid leaching, high-temperature high-pressure ion exchange and the like. However, both carbon reduction and aluminothermic reduction have low leaching rate, a great deal of toxic and harmful gas is released in the roasting process of the sulfate, and the high-temperature and high-pressure acid leaching and ion exchange have the problems of low selectivity, high pressure, difficult industrialization and the like.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides a method for selectively extracting lithium from a retired battery and application thereof.

According to one aspect of the invention, a method for selectively extracting lithium from a decommissioned battery is provided, comprising the following steps:

s1: mixing a lithium battery positive electrode material and divalent manganese salt, adding a solvent to prepare slurry, and carrying out ball milling on the slurry to obtain a ball-milled mixed material;

s2: roasting the ball-milling mixed material to obtain a roasted product;

s3: and adding a leaching agent into the roasted product for leaching to obtain a lithium-rich leaching solution.

Wherein the cathode material is of a layered structure.

In some embodiments of the invention, in step S1, the decommissioned battery is at least one of lithium manganate, lithium cobaltate, lithium nickel cobalt manganate or lithium nickel cobalt aluminate.

In some embodiments of the present invention, in step S2, the solvent is at least one of water, a hydrochloric acid solution, a sulfuric acid solution, a manganese nitrate solution, or a manganese sulfate solution.

In some preferred embodiments of the invention, the solvent is water.

In some embodiments of the present invention, in step S2, the solid-to-liquid ratio of the slurry is 500-5000 g/L.

In some preferred embodiments of the present invention, the slurry has a solid-to-liquid ratio of 800-2000 g/L.

In some embodiments of the invention, in step S2, the divalent manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese phosphate, manganese acetate, manganese oxalate or manganese acetylacetonate.

In some embodiments of the present invention, in step S2, the molar ratio of manganese ions in the divalent manganese salt to lithium ions in the positive electrode material (0.1 to 2): 1.

in some preferred embodiments of the present invention, the molar ratio of manganese ions in the divalent manganese salt to lithium ions in the positive electrode material (0.4 to 0.6): 1.

in some embodiments of the present invention, in step S2, the ball-milling has a ball-to-material ratio of (1-100): 1, the rotation speed of ball milling is 200 and 1200rpm, and the ball milling time is 0.5-8 h.

In some preferred embodiments of the present invention, the ball-milling has a ball-to-feed ratio of (2-10): 1, the rotation speed of ball milling is 300-.

In some embodiments of the present invention, in step S3, the baking temperature is 200-.

In some preferred embodiments of the present invention, the calcination temperature is 200-400 ℃, the temperature rise rate is 2-8 ℃/min, and the calcination time is 2-4 h.

In some embodiments of the invention, in step S4, the leaching agent is at least one of water, a carbonic acid solution, a sulfuric acid solution, a hydrochloric acid solution, or a sodium hydroxide solution.

In some preferred embodiments of the invention, the leaching agent is water.

In some embodiments of the present invention, in step S4, the solid-to-liquid ratio of the roasted product to the leaching agent is 800g/L and 100-.

The invention also provides the application of the method in the preparation of lithium salt.

According to a preferred embodiment of the present invention, at least the following advantages are provided:

the invention is based on the ion exchange function between divalent manganese ions and lithium ions, the positive electrode material and the divalent manganese salt are mixed according to a certain proportion and prepared into slurry, the divalent manganese salt and the positive electrode material are fully mixed through the ball milling process, the lattice structure of the positive electrode material is effectively destroyed, the activation energy of the divalent manganese ions and the lithium ion exchange is reduced, the reaction energy required in the subsequent lithium extraction process is greatly reduced, the mixed material after ball milling is roasted at a lower temperature, the divalent manganese in the manganese salt occupies the lithium position in the layered structure, the manganese and lithium replacement is directly carried out, and finally, the pure lithium-containing leachate is obtained. The invention adopts a mode of firstly ball-milling and mixing materials and then roasting, has low energy consumption, high safety and excellent leaching rate and selectivity of lithium, and has great application prospect.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is a process flow diagram of example 1 of the present invention;

FIG. 2 is an XRD of the leached residues in example 1 of the present invention.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Example 1

A method for selectively extracting lithium from a retired 111 type nickel cobalt lithium manganate battery is disclosed, referring to FIG. 1, and the specific process is as follows:

s1: placing the retired 111 type nickel cobalt lithium manganate battery in saturated brine for discharging, disassembling and separating out a positive plate, drying, crushing and screening the positive plate to obtain a 111 type nickel cobalt lithium manganate positive electrode material;

s2: mixing 5g of positive electrode material and manganese chloride according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: mixing the roasted product with deionized water according to the solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.055L of lithium-rich leaching solution and 6.22g of leaching residues. Wherein the lithium concentration in the lithium-rich leaching solution is 5.40g/L, the nickel concentration is 0.017g/L, the manganese concentration is 0.01g/L, and cobalt and aluminum are not detected.

The positive electrode material and the leaching residue in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 1. Wherein the leaching rate of lithium (volume of leachate + lithium concentration)/(mass of leached material + lithium content) × 100%, the selectivity of lithium (volume of leachate + lithium concentration)/(volume of leachate (lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) × 100%, and the leaching rate of lithium in step S4 was calculated to be 95.6%, and the selectivity was 99.5%. The lithium-rich leachate can be used for preparing various lithium salts through enrichment, the leaching residue obtained in the step S4 is analyzed by an X-ray diffractometer (XRD), the result is shown in figure 2, the main phases are oxides of nickel, cobalt and manganese, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

TABLE 1 EXAMPLE 1 cathode Material and Leaching slag composition

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	6.21	18.91	17.12	18.11	0.81
The leached residue%	0.15	15.31	14.98	35.23	0.66

Example 2

A method for selectively extracting lithium from a decommissioned 523 type nickel cobalt lithium manganate battery comprises the following specific processes:

s1: placing an ex-service 523 type nickel cobalt lithium manganate battery in saturated brine for discharging, disassembling and separating out a positive plate, drying, crushing and screening the positive plate to obtain a 523 type nickel cobalt lithium manganate positive electrode material;

s2: mixing 5g of positive electrode material and manganese nitrate according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: mixing the roasted product with deionized water according to a solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.060L of lithium-rich leachate and 6.34g of leaching residues, wherein the lithium concentration in the lithium-rich leachate is 5.54g/L, the nickel concentration is 0.032g/L, the manganese concentration is 0.040g/L, and cobalt and aluminum are not detected.

The positive electrode material and the leaching residue in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 2. Wherein the leaching rate of lithium (volume of leachate + lithium concentration)/(mass of leaching material + lithium content) × 100%, the selectivity of lithium (volume of leachate + lithium concentration)/(volume of leachate (lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) × 100%, and the leaching rate of lithium in step S4 was calculated to be 94.7%, and the selectivity was 98.7%. The lithium-rich leachate can be used for preparing various lithium salts through enrichment, the leaching residue of the step S4 is analyzed by an X-ray diffractometer (XRD), the main phases are oxides of nickel, cobalt and manganese, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

Table 2 example 2 cathode material and leached residue composition

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	7.02	31.56	10.34	11.28	0.56
The leached residue%	0.28	25.34	8.59	29.04	0.37

Example 3

A method for selectively extracting lithium from a retired 811 type nickel cobalt lithium manganate battery comprises the following specific processes:

s1: placing an ex-service 811 type nickel cobalt lithium manganate battery in saturated saline for discharging, disassembling and separating out a positive plate, drying, crushing and screening the positive plate to obtain a 811 type nickel cobalt lithium manganate positive electrode material;

s2: mixing 5g of positive electrode material and manganese sulfate according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: mixing the roasted product with deionized water according to the solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.056L of lithium-rich leaching solution and 6.37g of leaching residue. Wherein the lithium concentration in the lithium-rich leaching solution is 5.92g/L, the nickel concentration is 0.032g/L, the manganese concentration is 0.082g/L, and cobalt and aluminum are not detected.

The positive electrode material and the leaching residue in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 3. Wherein, the leaching rate of lithium is (volume of leaching solution x lithium concentration)/(mass of leaching material x lithium content) x 100%, and the lithium selectivity is (volume of leaching solution x lithium concentration)/(volume of leaching solution x lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) x 100%. The leaching rate of lithium in step S4 was calculated to be 92.1%, and the selectivity of lithium was calculated to be 98.1%. The lithium-rich leachate can be used for preparing various lithium salts through enrichment, the leaching residue of the step S4 is analyzed by an X-ray diffractometer (XRD), the main phases are oxides of nickel, cobalt and manganese, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

TABLE 3 example 3 Positive electrode Material and Leaching slag composition

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	7.20	39.58	5.08	4.97	0.69
The leached residue%	0.45	30.10	4.15	25.39	0.51

Example 4

A method for selectively extracting lithium from a retired lithium cobalt oxide battery comprises the following specific processes:

s1: placing an ex-service lithium cobalt oxide battery in saturated saline for discharging, disassembling and separating out a positive plate, drying, and crushing and screening the positive plate to obtain a lithium cobalt oxide positive electrode material;

s2: mixing 5g of positive electrode material and manganese chloride according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: mixing the roasted product with deionized water according to the solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.062L lithium-rich leaching solution and 6.64g leaching residues. Wherein the lithium concentration in the lithium-rich leaching solution is 5.33g/L, the cobalt concentration is 0.085g/L, the manganese concentration is 0.034g/L, and nickel and aluminum are not detected.

The positive electrode material and the leaching residue in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 4. Wherein, the leaching rate of lithium is (volume of leaching solution x lithium concentration)/(mass of leaching material x lithium content) x 100%, and the lithium selectivity is (volume of leaching solution x lithium concentration)/(volume of leaching solution x lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) x 100%. The leaching rate of lithium in step S4 was calculated to be 94.7%, and the selectivity of lithium was calculated to be 97.8%. The lithium-rich leaching solution can be used for preparing various lithium salts through enrichment, the leaching residue of the step S4 is analyzed by an X-ray diffractometer (XRD), the main phase is cobalt oxide, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

TABLE 4 example 4 composition of positive electrode material and leached residue

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	6.98	0	56.89	0	1.23
The leached residue%	0.05	0	45.12	21.20	1.08

Example 5

A method for selectively extracting lithium from a retired lithium manganate battery comprises the following specific processes:

s1: placing the retired lithium manganate battery in saturated brine for discharging, disassembling and separating out a positive plate, drying, and crushing and screening the positive plate to obtain a lithium manganate positive electrode material;

s2: mixing 5g of positive electrode material and manganese chloride according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: and mixing the roasted product with deionized water according to the solid-to-liquid ratio of 200g/L, stirring for 30min, and filtering and washing to obtain 0.071L of lithium-rich leaching solution and 6.17g of leaching residues. Wherein the lithium concentration in the lithium-rich leaching solution is 2.63g/L, the manganese concentration is 0.095g/L, and nickel, cobalt and aluminum are not detected.

The positive electrode material and the leaching residue in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 5. Wherein, the leaching rate of lithium is (volume of leaching solution x lithium concentration)/(mass of leaching material x lithium content) x 100%, and the lithium selectivity is (volume of leaching solution x lithium concentration)/(volume of leaching solution x lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) x 100%. The leaching rate of lithium in step S4 was calculated to be 90.6%, and the lithium selectivity was calculated to be 96.5%. The lithium-rich leachate can be used for preparing various lithium salts through enrichment, the leaching residue obtained in the step S4 is analyzed by an X-ray diffractometer (XRD), the main phase is manganese oxide, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

TABLE 5 example 5 Positive electrode Material and Leaching slag composition

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	4.12	0	0	62.50	0.21
The leached residue%	0.30	0	0	72.89	0.12

Example 6

A method for selectively extracting lithium from a retired lithium manganate battery comprises the following specific processes:

s1: placing the retired lithium manganate battery in saturated brine for discharging, disassembling and separating out a positive plate, drying, and crushing and screening the positive plate to obtain a lithium manganate positive electrode material;

s2: mixing 5g of positive electrode material and manganese chloride according to the molar ratio of lithium ions to manganese ions of 1:1, adding 2.5mol/L dilute sulfuric acid according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: and mixing the roasted product with deionized water according to the solid-to-liquid ratio of 200g/L, stirring for 30min, and filtering and washing to obtain 0.069L of lithium-rich leaching solution and 5.62g of leaching residues. Wherein the lithium concentration in the lithium-rich leaching solution is 2.63g/L, the nickel concentration is 0.016g/L, the manganese concentration is 0.11g/L, and cobalt and aluminum are not detected.

The positive electrode material and the leached residues in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 6. Wherein, the leaching rate of lithium is (volume of leaching solution x lithium concentration)/(mass of leaching material x lithium content) x 100%, and the lithium selectivity is (volume of leaching solution x lithium concentration)/(volume of leaching solution x lithium concentration + nickel concentration + cobalt concentration + manganese concentration + aluminum concentration)) x 100%. The leaching rate of lithium in step S4 was calculated to be 91.5%, and the lithium selectivity was calculated to be 95.4%. The lithium-rich leachate can be used for preparing various lithium salts through enrichment, the leaching residue obtained in the step S4 is analyzed by an X-ray diffractometer (XRD), the main phase is manganese oxide, and the leaching residue can be used for preparing various transition metal salts after acid dissolution and separation.

TABLE 6 example 6 Positive electrode Material and Leaching slag composition

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	3.96	0	0	65.50	0.27
The leached residue%	0.29	0	0	71.53	0.11

Comparative example 1

The method for selectively extracting lithium from the retired 811 type nickel cobalt lithium manganate battery is mainly characterized in that ball milling mixed materials are not roasted, and the specific process is as follows:

s1: placing an ex-service 811 type nickel cobalt manganese acid battery in saturated saline for discharging, disassembling and separating out a positive plate, drying, crushing and screening the positive plate to obtain a 811 type nickel cobalt manganese acid lithium positive electrode material;

s2: mixing 5g of positive electrode material and manganese chloride according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: mixing the ball-milled mixed material with deionized water according to a solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.056L of lithium-rich leaching solution and leaching residues. Wherein the lithium concentration in the lithium-rich leaching solution is 1.52g/L, the manganese concentration is 1.09g/L, the nickel concentration is 0.03g/L, and cobalt and aluminum are not detected.

The positive electrode material and the leached slag in the comparative example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 7. Wherein the leaching rate of lithium (volume of leachate, lithium concentration)/(mass of leached material, lithium content) is 100%, and the leaching rate of lithium in step S3 is calculated to be 23.6%.

TABLE 7 composition of positive electrode material and leached residue of comparative example 1

Element(s)	Li	Ni	Co	Mn	Al
						Anode material%	7.20	39.58	5.08	4.97	0.69
The leached residue%	5.69	41.58	6.21	5.21	0.63

From the extremely low leaching rate of the comparative example, the replacement effect is greatly reduced if the ball-milled mixed material is not calcined, so that the scheme of the invention needs to firstly carry out ball milling, firstly destroy the lattice structure of the anode material, so as to reduce the activation energy of the exchange of the divalent manganese ions and the lithium ions, and then carry out roasting at a lower temperature, so that the divalent manganese in the manganese salt occupies the lithium position in the anode material structure, and the manganese-lithium replacement is directly carried out, thus the steps of ball milling and roasting are all omitted.

Comparative example 2

The method for selectively extracting lithium from the retired lithium iron phosphate battery is mainly different from the method in the embodiment 3 in the aspect of anode material, and comprises the following specific processes:

s1: placing the retired lithium iron phosphate battery in saturated saline for discharging, disassembling and separating out a positive plate, drying, and crushing and screening the positive plate to obtain a lithium iron phosphate positive electrode material;

s2: mixing 5g of positive electrode material and manganese sulfate according to the molar ratio of lithium ions to manganese ions of 2:1, adding deionized water according to the solid-liquid ratio of 1000g/L, fully grinding to prepare viscous slurry, and mixing the slurry with the weight ratio of 10: ball milling is carried out for 2 hours at a ball-material ratio of 1 and a rotating speed of 300rpm to obtain a ball-milled mixed material;

s3: placing the ball-milled mixed material in a muffle furnace for roasting, wherein the heating rate is 5 ℃/min, and roasting for 5h at 250 ℃ to obtain a roasted product;

s4: mixing the roasted product with deionized water at a solid-to-liquid ratio of 200g/L, stirring for 30min, filtering and washing to obtain 0.062L of lithium leaching solution and leaching residues. Wherein the lithium leaching solution has a lithium concentration of 0.59g/L and an iron concentration of 0.05 g/L.

The positive electrode material and the leached residues in this example were measured by an inductively coupled plasma emission spectrometer (ICP-OES) and an atomic absorption spectrophotometer, and the results are shown in table 8. Wherein the leaching rate of lithium (volume of leachate, lithium concentration)/(mass of leached material, lithium content) is 100%, and the leaching rate of lithium in step S3 is calculated to be 17.65%.

TABLE 8 composition of positive electrode material and leached residue of comparative example 2

The leaching rate of the comparative example was very low because lithium iron phosphate was olivine structure, while the positive electrode material selected for the present invention was layered structure. The principle of the invention is that bivalent manganese in manganese salt occupies lithium position in a layered structure, and manganese-lithium replacement is directly carried out, so that pure lithium-containing leachate can be obtained, the structure and composition of lithium iron phosphate are different from the anode material of the invention, so that the difference of physicochemical properties of the lithium iron phosphate and the lithium iron phosphate is extremely large, the comparative example 2 is that the method is used for extracting lithium from the lithium iron phosphate, due to the structural difference and different replacement mechanisms, bivalent manganese cannot directly occupy lithium position in the lithium iron phosphate structure for replacement, bivalent iron in the lithium iron phosphate is replaced, and simultaneously lithium deintercalation is caused, so that finally the obtained mixed leachate is obtained, and the replacement in the lithium iron phosphate has higher energy barrier, and the low-temperature roasting of the method cannot provide enough energy. Therefore, the method is only suitable for the cathode material with a layered structure and is not suitable for the lithium iron phosphate with an olivine structure, and the purpose of the method cannot be achieved if the cathode material is replaced by the lithium iron phosphate.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.