WO2024183014A1 - Method for selectively recycling lithium and system device for selectively recycling lithium - Google Patents

Abstract

A method for selectively recycling lithium and a system device for selectively recycling lithium. The method comprises the following steps: mixing a positive electrode active material with a carbon reducing agent, and roasting the mixture to obtain a product; and carrying out water leaching treatment on the product, and introducing in the water leaching treatment process tail gas generated in the roasting process to obtain a lithium-rich leachate. Roasting is carried out on the positive electrode active material, so that the carbonization and water leaching process has a high selectivity to lithium, and thus the content of lithium in the lithium-rich leachate is far higher than that of another metal element. In addition, the tail gas is used to carry out carbonization and water leaching, so that lithium carbonate can be transformed into soluble lithium bicarbonate, the leaching rate of lithium is increased, the tail gas can be fully utilized, and recycling costs are reduced.

Description

A method for selectively recovering lithium and a system device for selectively recovering lithium Technical Field

The embodiments of the present application relate to the field of resource recovery technology, such as a method for selectively recovering lithium and a system device for selectively recovering lithium.

Background Art

In recent years, with the rapid development of new energy vehicles, the market demand for lithium-ion power batteries has continued to grow rapidly. As an important component of lithium-ion power batteries, lithium has been in short supply, and its price has continued to rise. At present, the main means of recycling lithium in ternary lithium batteries in industrial production is to recycle lithium at the back end, which causes a considerable amount of lithium loss. Therefore, efficient and selective recycling of lithium at the front end is of great significance to solve the problem of lithium shortage in the market and alleviate the problem of relatively scarce lithium resources in my country.

At present, the method of selectively recovering lithium at the front end is mainly to selectively leach lithium after pretreatment. Usually, water leaching or carbonization water leaching is used after pyrometallurgical pretreatment or mechanical pretreatment. Among them, conventional pyrometallurgical pretreatments include carbon reduction, hydrogen reduction, and sulfation roasting, and mechanical pretreatments include chloride ball milling, nitrate ball milling activation, etc. The selectivity of leaching after mechanical pretreatment is relatively poor, and the leaching rate of lithium is difficult to reach a high level, while the selectivity of leaching after pyrometallurgical pretreatment is better, and the leaching rate of lithium can reach a high level.

Among the leaching methods, water leaching usually has the problem of too high liquid-to-solid ratio, resulting in too low lithium liquid concentration and difficulty in recovering lithium. In contrast, carbonization water leaching is more conducive to obtaining high-concentration lithium liquid, which is conducive to lithium recovery. However, the related technology uses carbon dioxide finished product to pass into water for carbonization water leaching, which will also increase the recovery cost.

Therefore, a method with low cost, good selectivity and high leaching rate is urgently needed to selectively recover lithium.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

The embodiment of the present application provides a method for selectively recovering lithium and a system device for selectively recovering lithium, which uses a roasting method to treat the positive electrode active material so that the carbonization water leaching process has a high selectivity for lithium, so that the lithium content in the lithium-rich leachate is much higher than the content of other metal elements. In addition, the use of tail gas for carbonization water leaching can not only convert lithium carbonate into easily soluble lithium bicarbonate, improve the leaching rate of lithium, but also make full use of tail gas to save recovery costs.

In a first aspect, the present invention provides a method for selectively recovering lithium, the method comprising: Follow these steps:

(1) mixing a positive electrode active material with a carbon reducing agent and calcining to obtain a product;

(2) The product is subjected to water leaching treatment, during which tail gas generated during the roasting process is passed through the water leaching treatment to obtain a lithium-rich leaching solution.

The present application provides a method for selectively recovering lithium, wherein a carbon reducing agent is used to reduce and roast the positive electrode active material. After reduction, the lithium in the positive electrode active material is converted into lithium carbonate, and a lithium-rich leachate is obtained by carbonizing and leaching the lithium carbonate and other products, wherein the gas source of the carbonizing and leaching is the tail gas (including CO ₂ and H ₂ O) generated during the roasting process. The positive electrode active material is treated by roasting, so that the carbonizing and leaching process has a high selectivity for lithium, so that the lithium content in the lithium-rich leachate is much higher than the content of other metal elements. In addition, the use of tail gas for carbonizing and leaching can not only convert lithium carbonate into easily soluble lithium bicarbonate, thereby improving the leaching rate of lithium, but also make full use of tail gas and save recovery costs.

The present application does not specifically limit the type of active substance in the positive electrode active material, including but not limited to any one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium cobalt manganese oxide, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, or a combination of at least two thereof.

As a preferred technical solution of the present application, the particle size of the positive electrode active material is 100-200 mesh, for example, it can be 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh or 200 mesh.

Preferably, the positive electrode active material is prepared by crushing a positive electrode sheet.

The present application does not limit the method of crushing, for example, crushing can be performed in a crusher. At the same time, the type of crusher is not specifically limited. For example, the crusher can be a shearing crusher or a shredder.

Preferably, after the positive electrode sheets are crushed, a screening step is also provided.

In the present application, the positive electrode sheet is crushed and then sieved to separate the positive electrode active material and the aluminum foil, and the positive electrode active material is used to recover lithium.

Preferably, the crushing time is 5 to 20 min, for example, 5 min, 7 min, 10 min, 12 min, 14 min, 16 min, 18 min or 20 min.

As a preferred technical solution of the present application, the carbon reducing agent includes an organic carbon reducing agent and/or an inorganic carbon reducing agent.

During the calcination process of the present application, the carbon reducing agent and the positive electrode active material will undergo a "solid-solid" reduction reaction. In addition, the carbon reducing agent will be cracked during the reduction calcination process, and the reducing gas (such as CO, _H2 and _CH4 , etc.) can also participate in the reaction to carry out a "gas-solid" reduction reaction, greatly improving the efficiency of the reduction process.

In the present application, the reducing gas (such as CO, _H2 and _CH4 , etc.) produced by the decomposition of the carbon reducing agent is combustible and can be fully burned with air to provide heat for the reduction roasting process, and the tail gas produced by the combustion (i.e., the tail gas produced by the reduction roasting process) is used for water immersion treatment. It should be noted that the tail gas produced by the combustion does not contain combustible reducing gas.

In the present application, the carbon reducing agent is preferably an organic carbon reducing agent. The carbon dioxide content in the tail gas generated after the organic carbon reduction roasting is relatively high, and the tail gas can be directly introduced into water for carbonization immersion.

Preferably, the organic carbon reductant comprises sugars and/or biomass.

The present application does not specifically limit the types of sugars, including but not limited to starch.

The present application does not specifically limit the type of biomass, including but not limited to any one of wood chips, straw, rice straw or sawdust, or a combination of at least two of them.

Preferably, the inorganic carbon reducing agent comprises coal.

As a preferred technical solution of the present application, the mass ratio of the carbon reducing agent to the positive electrode active material is 0.1 to 0.4, for example, it can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4.

As a preferred technical solution of the present application, the mixing method includes ball milling.

Preferably, the rotation speed of the ball mill is 300-600 r/min, for example, it can be 300 r/min, 350 r/min, 400 r/min, 450 r/min, 500 r/min, 550 r/min or 600 r/min.

Preferably, the ball milling time is 15 to 60 min, for example, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

As a preferred technical solution of the present application, the heating method during the roasting process includes electric heating and/or self-heating.

In the present application, self-heating specifically means that during the reduction roasting process, the carbon reducing agent is cracked to produce combustible gas (such as CO, _H2 and _CH4 , etc.), and the discharged combustible gas can be burned with air to release heat for reduction roasting, and the tail gas generated after combustion is used for carbonization water immersion treatment. The use of self-heating can not only reduce energy consumption and improve heating efficiency, but also solve the problem of cracking gas treatment, avoiding the pollution and safety problems of cracking gas.

Electric heating refers to the conversion of electrical energy into thermal energy. This process is usually achieved in heating equipment (such as atmosphere tube furnace or box furnace, etc.).

In the present application, an optional implementation method includes: the heating method during the roasting process adopts electric heating Combined with self-heating, when the heat provided by self-heating is not enough to support the heat required for the roasting process, electric heating can be started to supplement the required heat.

Preferably, the calcination process is carried out under a protective atmosphere.

Preferably, the gas in the protective atmosphere includes any one of nitrogen, argon or carbon dioxide, or a combination of at least two of them.

As a preferred technical solution of the present application, the calcination heating rate is 3 to 10°C/min, for example, it can be 3°C/min, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min or 10°C/min, etc.

Preferably, the calcination temperature is 500-750°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C or 750°C.

In the present application, if the calcination temperature is too low, the lithium extraction efficiency will be reduced. This is because the low temperature causes the reduction reaction to be insufficient, and some positive electrode active materials still maintain their inherent form, resulting in insufficient lithium carbonate production; if the calcination temperature is too high, the lithium extraction efficiency will be reduced. This is because the reduction reaction is too sufficient, and more metal elements are generated, which wraps the lithium carbonate and increases the difficulty of leaching.

Preferably, the calcination time is 1 to 5 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h.

As a preferred technical solution of the present application, during the water immersion treatment, the liquid-to-solid ratio of water to the product is (5-15) mL:1g, for example, it can be 5 mL:1g, 7 mL:1g, 9 mL:1g, 11 mL:1g, 13 mL:1g or 15 mL:1g, etc.

Preferably, during the water immersion treatment, the ratio of the exhaust gas introduction rate to the volume of water is (0.5-2) mL/min:1 mL, for example, it can be 0.5 mL/min:1 mL, 0.7 mL/min:1 mL, 1 mL/min:1 mL, 1.2 mL/min:1 mL, 1.4 mL/min:1 mL, 1.6 mL/min:1 mL, 1.8 mL/min:1 mL or 2 mL/min:1 mL, etc.

In the present application, if the ratio of the tail gas introduction rate to the volume of water is too low, the lithium leaching efficiency will be reduced, because the low flow rate of _CO2 will lead to a lower concentration of carbonate in the solution, affecting the dissolution rate and total amount of lithium carbonate dissolved; if the ratio of the tail gas introduction rate to the volume of water is too high, it will lead to excessive waste of _CO2 , and in the case of insufficient lithium carbonate, it will increase the dissolution rate of other valuable metals and reduce the selectivity of leaching.

As a preferred technical solution of the present application, the time of the water immersion treatment is 0.5 to 1.5 h, for example, it can be 0.5 h, 0.7 h, 1 h, 1.2 h or 1.5 h.

Preferably, the water immersion treatment is accompanied by stirring.

Preferably, the stirring speed is 300-500 r/min, for example, it can be 300 r/min, 320 r/min, 340 r/min, 360 r/min, 380 r/min, 400 r/min, 420 r/min, 440 r/min, 460 r/min, 480 r/min or 500 r/min.

As a preferred technical solution of the present application, the method specifically comprises the following steps:

(I) mixing the positive electrode active material and the carbon reducing agent at a rotation speed of 300 to 600 r/min for 15 to 60 min to obtain a mixture, and calcining the mixture at a temperature of 500 to 750° C. for 1 to 5 h to obtain a product;

(II) The product is subjected to water leaching treatment, wherein the liquid-to-solid ratio of water to the product is (5-15) mL:1 g. During the water leaching treatment, tail gas generated during the roasting process is passed through, and the ratio of the introduction rate of the tail gas to the volume of water is (0.5-2) mL/min:1 mL. After 0.5-1.5 h of water leaching treatment, a lithium-rich leaching solution and leaching residue are obtained.

In the present application, after the positive electrode active material and the carbon reducing agent are reduced and roasted, the valuable metal elements (such as nickel, cobalt or manganese, etc.) in the active substance of the positive electrode active material are converted into a metallic state or a low-valent oxide state, and are carbonized and then immersed in water and placed in the leached slag.

The positive electrode active material also includes a binder and a conductive agent, among which the binder may participate in the reduction roasting, and is basically removed by cracking, and the unreacted conductive agent enters the leaching slag.

In a second aspect, an embodiment of the present application provides a system device for selectively recovering lithium, wherein the method described in the first aspect is performed in the system device;

The system device comprises a roasting device and a water immersion container connected in sequence;

The roasting equipment comprises a pyrolysis chamber and a combustion chamber arranged outside the pyrolysis chamber, the pyrolysis chamber is provided with a feed inlet and a combustible gas outlet, the combustion chamber is provided with a combustible gas inlet, an air inlet and an exhaust gas outlet, and the combustible gas outlet is connected to the combustible gas inlet;

The tail gas outlet is connected to an exhaust pipeline, and the output end of the exhaust pipeline extends into the inner cavity of the water immersion container.

In the present application, the carbon reducing agent and the positive electrode active material can be reduced and calcined in a pyrolysis chamber. The combustible gas generated by the cracking of the carbon reducing agent is discharged through the combustible gas outlet and then enters the combustion chamber through the combustible gas inlet. The combustible gas burns with the air entering the combustion chamber, and the heat released by the combustion is transferred to the pyrolysis chamber; the exhaust gas generated after the combustion is transported to the water immersion container through the exhaust gas outlet for water immersion treatment.

Self-heating can be achieved by using the above-mentioned system device.

Preferably, an interlayer is provided between the pyrolysis chamber and the combustion chamber, and a heating element is provided in the interlayer.

In the present application, an interlayer is provided between the pyrolysis chamber and the combustion chamber and a heating element is provided therein, and the heating element can convert electrical energy into thermal energy, thereby realizing combined heating of electric heating and self-heating.

Preferably, the heating element comprises a heating coil.

Preferably, an air intake valve is provided on the connecting pipeline between the combustible gas outlet and the combustible gas inlet.

Preferably, an exhaust valve is provided on the exhaust pipeline.

The numerical range described in this application includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to limited space and for the sake of brevity, this application no longer exhaustively lists the specific point values included in the range.

Compared with the related art, the beneficial effects of the embodiments of the present application are:

The embodiment of the present application provides a method for selectively recovering lithium, wherein a carbon reducing agent is used to reduce and roast the positive electrode active material. After reduction, the lithium in the positive electrode active material is converted into lithium carbonate, and a lithium-rich leachate is obtained by carbonization water leaching of the lithium carbonate and other products, wherein the gas source of the carbonization water leaching is the tail gas (including CO ₂ and H ₂ O) generated during the roasting process. The positive electrode active material is treated by roasting, so that the carbonization water leaching process has a high selectivity for lithium, so that the lithium content in the lithium-rich leachate is much higher than the content of other metal elements. In addition, the use of tail gas for carbonization water leaching can not only convert lithium carbonate into easily soluble lithium bicarbonate, thereby improving the leaching rate of lithium, but also make full use of tail gas to save recovery costs.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

FIG1 is a schematic flow diagram of a method for selectively recovering lithium provided in one embodiment of the present application;

FIG2 is a schematic diagram of a self-heating reduction roasting device provided in a specific embodiment of the present application;

Among them, 1-pyrolysis chamber; 2-combustion chamber; 3-feeding port; 4-combustible gas outlet; 5-combustible gas inlet; 6-air inlet; 7-exhaust gas outlet; 8-water immersion container.

DETAILED DESCRIPTION

The technical solution of the present application is further illustrated below through specific implementation methods.

In a specific embodiment, the present application provides a method for selectively recovering lithium, as shown in FIG1 , the method specifically comprises the following steps:

(1) crushing and screening the nickel-cobalt-manganese ternary positive electrode sheet to obtain aluminum foil and nickel-cobalt-manganese ternary positive electrode active material;

(2) mixing the nickel-cobalt-manganese ternary positive electrode active material with an organic carbon reducing agent and performing autothermal reduction roasting to obtain a roasting product; wherein the organic carbon reducing agent is cracked during the reduction roasting process to produce a cracked combustible gas, the cracked combustible gas is burned with air to provide heat for the reduction roasting process, and the cracked combustible gas is fully burned to produce a combustion exhaust gas;

(3) The roasted product is subjected to a carbonization water leaching treatment, during which combustion tail gas generated during the autothermal reduction roasting process is passed through the carbonization water leaching treatment to obtain a lithium-rich leaching solution and nickel-cobalt-manganese slag.

Example 1

The present embodiment provides a system device for selectively recovering lithium, as shown in FIG2 , comprising a roasting device and a water immersion container 8 connected in sequence; the roasting device comprises a pyrolysis chamber 1 and a combustion chamber 2 arranged at the periphery of the pyrolysis chamber 1, the pyrolysis chamber 1 is provided with a feed port 3 and a combustible gas outlet 4, the combustion chamber 2 is provided with a combustible gas inlet 5, an air inlet 6 and an exhaust gas outlet 7, the combustible gas outlet 4 is connected to the combustible gas inlet 5; the exhaust gas outlet 7 is connected to an exhaust pipeline, and the output end of the exhaust pipeline extends into the inner cavity of the water immersion container 8;

An interlayer is provided between the pyrolysis chamber 1 and the combustion chamber 2, a heating coil is provided in the interlayer, and the heating coil and the combustion chamber 2 are electrically connected via a controller, and the controller is used to adjust the temperature.

In the system device of this embodiment, the carbon reducing agent and the positive electrode active material can react in the pyrolysis chamber 1, and the combustible gas generated by the cracking of the carbon reducing agent is discharged through the combustible gas outlet 4, and then enters the combustion chamber 2 through the combustible gas inlet 5. The combustible gas is burned with the air introduced into the combustion chamber 2, and the heat released by the combustion is transferred to the pyrolysis chamber 1. The exhaust gas generated by the combustion can be introduced into the water immersion container 8.

Example 2

This embodiment provides a method for selectively recovering lithium, which is carried out in the system device provided in Example 1, and specifically comprises the following steps:

(1) 1000 g of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) positive electrode sheet was crushed using a shear crusher for 10 min to obtain crushed ternary electrode sheet powder, and the crushed ternary electrode sheet powder was sieved using a 120-mesh sieve to obtain 903 g of ternary positive electrode active material and 94 g of aluminum foil;

(2) Take 900g of NCM523 ternary positive electrode active material, add 180g of starch, use a ball mill to mix at a speed of 450r/min for 30min, and then place 1000g of the fully mixed material to be calcined on a steel plate. The crucible was placed in a pyrolysis chamber protected by nitrogen and heated to 650°C at a heating rate of 5°C/min. During the heating process, the combustible gas produced by cracking was introduced into the combustion chamber and mixed with air to supplement the heat. The temperature of the pyrolysis chamber was regulated by a controller and kept at 650°C for 3 hours to obtain a reduction roasting product.

(3) 100 g of the reduction roasting product was placed in a water immersion container and carbonized in water using combustion tail gas. The liquid-solid ratio of water to the reduction roasting product was 10 mL:1 g. The ventilation rate of the tail gas was 1000 mL/min. The carbonization water immersion was accompanied by stirring at a stirring rate of 400 r/min. After leaching for 1.5 h, lithium-rich leaching solution and leaching residue were separated.

Test Method:

The lithium-rich leaching solution was subjected to ICP element analysis to detect the concentration of each valuable metal ion therein.

Analysis and calculation of the test results show that the Li leaching rate is 97%, the Ni leaching rate is 0.1%, the Co leaching rate is 0.001%, and the Mn leaching rate is 0.001%.

Example 3

This embodiment provides a method for selectively recovering lithium, which is carried out in the system device provided in Example 1, and specifically comprises the following steps:

(1) 1000 g of LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622) positive electrode sheet was crushed using a shear crusher for 10 min to obtain crushed ternary electrode sheet powder, and the crushed ternary electrode sheet powder was sieved using a 200-mesh sieve to obtain 873 g of ternary positive electrode active material and 125 g of aluminum foil;

(2) 800 g of NCM622 ternary positive electrode active material was taken, 240 g of sawdust was added, and the mixture was ball milled at a speed of 450 r/min for 30 min. Then, 1000 g of the fully mixed material to be calcined was placed in a corundum crucible, and then placed in a nitrogen-protected pyrolysis chamber, and heated to 700 °C at a heating rate of 5 °C/min. During the heating process, the combustible gas generated by cracking was introduced into the combustion chamber, mixed with air to supplement heat, and the temperature of the pyrolysis chamber was regulated by a controller, and kept at 700 °C for 4 h to obtain a reduction calcination product;

(3) 200 g of the reduction roasting product was placed in a water immersion container and carbonized in water using combustion tail gas. The liquid-solid ratio of water to the reduction roasting product was 15 mL:1 g. The ventilation rate of the tail gas was 1500 mL/min. The carbonization water immersion was accompanied by stirring at a stirring rate of 500 r/min. After leaching for 1 h, lithium-rich leaching solution and leaching residue were separated.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 98%, the Ni leaching rate is 0.03%, the Co leaching rate is 0.001%, and the Mn leaching rate is 0.001%.

Example 4

This embodiment provides a method for selectively recovering lithium, which is carried out in the system device provided in Example 1, and specifically comprises the following steps:

(1) 1000 g of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) positive electrode sheet was crushed using a shear crusher for 10 min to obtain crushed ternary electrode sheet powder, and the crushed ternary electrode sheet powder was sieved using a 200-mesh sieve to obtain 863 g of ternary positive electrode active material and 130 g of aluminum foil;

(2) 700 g of NCM811 ternary positive electrode active material was taken, and 175 g of straw was added. The mixture was ball milled at a speed of 450 r/min for 30 min, and then 800 g of the fully mixed material to be calcined was placed in a corundum crucible, and then placed in a pyrolysis chamber protected by nitrogen, and heated to 600 °C at a heating rate of 5 °C/min. During the heating process, the combustible gas generated by cracking was introduced into the combustion chamber, mixed with air to supplement heat, and the temperature of the pyrolysis chamber was regulated by a controller, and the temperature was kept at 600 °C for 5 h to obtain a reduction calcination product;

(3) 500 g of the reduction roasting product was placed in a water immersion container and carbonized in water using combustion tail gas. The liquid-solid ratio of water to the reduction roasting product was 5 mL:1 g. The ventilation rate of the tail gas was 5000 mL/min. The carbonization water immersion was accompanied by stirring at a stirring rate of 300 r/min. After leaching for 1.5 h, lithium-rich leaching solution and leaching residue were separated.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 97.6%, the Ni leaching rate is 0.001%, the Co leaching rate is 0.001%, and the Mn leaching rate is 0.001%.

Example 5

This embodiment provides a method for selectively recovering lithium, which is carried out in the system device provided in Example 1, and specifically comprises the following steps:

(1) 1000 g of _LiCoO2 positive electrode sheet was crushed using a shear crusher for 15 min to obtain crushed electrode sheet powder, and the crushed electrode sheet powder was sieved using a 150-mesh sieve to obtain 890 g of positive electrode active material and 105 g of aluminum foil;

(2) 800 g of _LiCoO2 positive electrode active material was added with 80 g of rice husk, and the mixture was ball milled at a speed of 450 r/min for 30 min. Then, 800 g of the fully mixed material to be calcined was placed in a corundum crucible, and then placed in a pyrolysis chamber protected by nitrogen, and heated to 750 °C at a heating rate of 5 °C/min. During the heating process, the combustible gas generated by cracking was introduced into the combustion chamber, mixed with air to supplement heat, and the temperature of the pyrolysis chamber was regulated by a controller, and kept at 750 °C for 2 h to obtain a reduction calcination product;

(3) 300 g of the reduced roasted product was placed in a water immersion container and carbonized by water immersion using combustion tail gas. The liquid-solid ratio of water to the reduced roasted product was 10 mL:1 g, and the ventilation rate of the tail gas was 2000 mL/min. The carbonization water leaching was accompanied by stirring at a stirring rate of 400 r/min. After leaching for 1.5 h, lithium-rich leaching solution and leaching residue were separated.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 98.2% and the Co leaching rate is 0.01%.

Example 6

This embodiment provides a method for selectively recovering lithium. The difference from Embodiment 2 is that the calcination temperature is adjusted to 450° C., and the other process parameters and operation steps are the same as those of Embodiment 2.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 45.7%, the Ni leaching rate is 0.86%, the Co leaching rate is 0.23%, and the Mn leaching rate is 0.21%.

Example 7

This embodiment provides a method for selectively recovering lithium. The difference from Embodiment 2 is that the roasting temperature is adjusted to 800° C., and the other process parameters and operation steps are the same as those of Embodiment 2.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 88.7%, the Ni leaching rate is 0.29%, the Co leaching rate is 0.01%, and the Mn leaching rate is 0.01%.

Example 8

This embodiment provides a method for selectively recovering lithium. The difference from Example 2 is that the ventilation rate of the tail gas is adjusted to 200 mL/min, so that the ratio of the ventilation rate of the tail gas to the water volume is adjusted to 0.2 mL/min:1 mL, and the remaining process parameters and operating steps are the same as those in Example 2.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 85%, the Ni leaching rate is 0.01%, the Co leaching rate is 0.01%, and the Mn leaching rate is 0.01%.

Example 9

This embodiment provides a method for selectively recovering lithium. The difference from Example 2 is that the ventilation rate of the tail gas is adjusted to 2500 mL/min, so that the ratio of the ventilation rate of the tail gas to the water volume is adjusted to 2.5 mL/min:1 mL, and the remaining process parameters and operating steps are the same as those in Example 2.

The lithium-rich leaching solution was tested using the test method described in Example 2.

Analysis and calculation of the test results show that the Li leaching rate is 95.3%, the Ni leaching rate is 1.03%, the Co leaching rate is 0.5%, and the Mn leaching rate is 0.6%.

analyze:

From the results of Example 2, it can be seen that when the method of the present application is used for lithium extraction, the Li leaching rate is as high as 97%, while the leaching rates of Ni, Co and Mn are very low, which indicates that the method for selectively recovering lithium provided by the present application has a high Li selectivity and a high Li leaching rate.

It can be seen from the results of Example 2, Example 6 and Example 7 that the calcination temperature affects the lithium extraction effect. When the calcination temperature is too low, the lithium extraction efficiency will be reduced to only 45.7%. This is because the low temperature causes the reduction reaction to be insufficient, and some positive electrode active materials still maintain their inherent form, resulting in insufficient lithium carbonate production; when the calcination temperature is too high, the lithium extraction efficiency will be reduced to 88.7%. This is because the reduction reaction occurs too fully, more metal elements are generated, and the lithium carbonate is wrapped, increasing the difficulty of leaching.

It can be seen from the results of Example 2, Example 8 and Example 9 that the ratio of the tail gas introduction rate to the volume of water will also affect the lithium extraction effect. When the ratio of the tail gas introduction rate to the volume of water is too low, the lithium leaching efficiency will be reduced to 85%. This is because the low flow rate of _CO2 will lead to a lower concentration of carbonic acid in the solution, affecting the dissolution rate and total amount of lithium carbonate dissolved; when the ratio of the tail gas introduction rate to the volume of water is too high, it will lead to excessive waste of _CO2 . In the case of insufficient lithium carbonate, the dissolution rate of other valuable metals will increase, reducing the selectivity of leaching.

The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in the present application are within the protection scope and disclosure scope of the present application.

Claims (13)

A method for selectively recovering lithium comprises the following steps: (1) mixing a positive electrode active material with a carbon reducing agent and calcining to obtain a product; (2) The product is subjected to water leaching treatment, during which tail gas generated during the roasting process is passed through the water leaching treatment to obtain a lithium-rich leaching solution. The method according to claim 1, wherein the particle size of the positive electrode active material is 100 to 200 meshes. The method according to claim 1 or 2, wherein the positive electrode active material is prepared by crushing the positive electrode sheet. The method according to claim 3, wherein the crushing time is 5 to 20 minutes. The method according to any one of claims 1 to 4, wherein the carbon reducing agent comprises an organic carbon reducing agent and/or an inorganic carbon reducing agent; Preferably, the organic carbon reductant comprises sugars and/or biomass; Preferably, the inorganic carbon reducing agent comprises coal. The method according to any one of claims 1 to 5, wherein the mass ratio of the carbon reducing agent to the positive electrode active material is 0.1 to 0.4. The method according to any one of claims 1 to 6, wherein the mixing method comprises ball milling; Preferably, the rotation speed of the ball mill is 300-600 r/min; Preferably, the ball milling time is 15 to 60 minutes. The method according to any one of claims 1 to 7, wherein the heating method during the roasting process includes electric heating and/or self-heating; Preferably, the calcination process is carried out under a protective atmosphere; Preferably, the gas in the protective atmosphere includes any one of nitrogen, argon or carbon dioxide, or a combination of at least two thereof; Preferably, the heating rate of the calcination is 3 to 10°C/min; Preferably, the calcination temperature is 500-750°C; Preferably, the calcination time is 1 to 5 hours. The method according to any one of claims 1 to 8, wherein during the water immersion treatment, the liquid-to-solid ratio of water to the product is (5 to 15) mL:1 g; Preferably, during the water immersion treatment, the ratio of the tail gas introduction rate to the volume of water is (0.5-2) mL/min:1 mL; Preferably, the water immersion treatment time is 0.5 to 1.5 hours; Preferably, the water immersion treatment is accompanied by stirring; Preferably, the stirring speed is 300-500 r/min. The method according to any one of claims 1 to 9, comprising the following steps: (I) mixing the positive electrode active material and the carbon reducing agent at a rotation speed of 300 to 600 r/min for 15 to 60 min to obtain a mixture, and calcining the mixture at a temperature of 500 to 750° C. for 1 to 5 h to obtain a product; (II) The product is subjected to water leaching treatment, wherein the liquid-to-solid ratio of water to the product is (5-15) mL:1 g. During the water leaching treatment, tail gas generated during the roasting process is passed through, and the ratio of the introduction rate of the tail gas to the volume of water is (0.5-2) mL/min:1 mL. After 0.5-1.5 h of water leaching treatment, a lithium-rich leaching solution and leaching residue are obtained. A system device for selectively recovering lithium, wherein the method according to any one of claims 1 to 10 is carried out in the system device; The system device comprises a roasting device and a water immersion container connected in sequence; The roasting equipment comprises a pyrolysis chamber and a combustion chamber arranged outside the pyrolysis chamber, the pyrolysis chamber is provided with a feed inlet and a combustible gas outlet, the combustion chamber is provided with a combustible gas inlet, an air inlet and an exhaust gas outlet, and the combustible gas outlet is connected to the combustible gas inlet; The tail gas outlet is connected to an exhaust pipeline, and the output end of the exhaust pipeline extends into the inner cavity of the water immersion container. The system device according to claim 11, wherein an interlayer is provided between the pyrolysis chamber and the combustion chamber, and a heating element is provided in the interlayer. The system of claim 12, wherein the heating element comprises a heating coil.