WO2023245889A1

WO2023245889A1 - Method for recovering battery powder by low-temperature pyrolysis desorption

Info

Publication number: WO2023245889A1
Application number: PCT/CN2022/119978
Authority: WO
Inventors: 余海军; 谢英豪; 李爱霞; 张学梅; 李长东
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-06-23
Filing date: 2022-09-20
Publication date: 2023-12-28
Also published as: CN115172923A; DE112022002405T5; GB202318191D0

Abstract

Disclosed is a method for recovering battery powder by low-temperature pyrolysis desorption, comprising: enabling reaction of a waste battery crushed material in a mixed atmosphere, under an air pressure of 3-8 MPa, and at a temperature of 120-150°C, the mixed atmosphere being mixed gas of CO₂, NO, and O₂; enabling reaction of the obtained reaction product under a negative pressure and at a temperature of 310-360°C; and then sorting to obtain copper-aluminum foil and battery powder. According to the present invention, a combined process of low-temperature high-pressure pyrolysis and medium-temperature negative-pressure pyrolysis is used, and the temperature of the whole process is controlled to be 400°C or below, such that the purpose of separating from a current collector can be achieved; chain scission of a polymer is achieved, and oxidation of copper and aluminum is avoided.

Description

Method for recycling battery powder by low-temperature thermal desorption

Technical field

The invention belongs to the technical field of battery recycling, and specifically relates to a method for low-temperature thermal desorption and recycling of battery powder.

Background technique

Lithium-ion batteries have a complex structure and are composed of multiple components such as casings, separators, positive electrodes, and negative electrodes. In the process of recycling used batteries, it is necessary to separate different components through a series of methods. Among them, the negative electrode is composed of graphite, binder, conductive agent and current collector copper foil. The positive electrode is made of active material powder, binder and conductive agent coated on the current collector aluminum foil. The positive active material powder mainly includes LiCoO ₂ and LiNiO ₂ , LiMnO ₂ , LiFePO ₄ and _LiNix Co _y Mn _1-xy O ₂ , etc.

The pre-treatment process for recycling used lithium-ion batteries usually requires certain technical means to desorb and separate the active material powder from the current collector.

At present, the separation of active materials and current collectors mainly starts from three aspects: ① According to the characteristics of metal aluminum that can be dissolved in alkaline solution, soaking the positive electrode core in an alkaline solution can achieve the purpose of separating the positive electrode powder and current collector. This method has the advantages of low energy consumption and strong operability, but the current collector aluminum foil enters the solution in the form of ions and requires further recycling. In addition, this process requires a large amount of alkali solution. In order to prevent the alkali solution from causing secondary pollution, neutralization treatment is required, which will require additional costs. In order to avoid the introduced alkali solution from contaminating the powder, during the filtration process, The desorption active material must be fully rinsed or acid neutralized; ② Use organic solvents to dissolve the binder PVDF so that the current collector metal foil can be recycled in solid form. However, organic solvents are usually expensive and are not suitable for large-scale industrial applications. ; ③ Direct heating to a specific temperature in the air can deactivate the binder to achieve the purpose of separating the current collector aluminum foil. It is also the most reported pyrolysis pretreatment process for lithium battery recycling.

The pyrolysis pretreatment process is widely used in existing industrial production, but there are also some major problems, such as: ① The temperature of conventional pyrolysis is above 500°C. Due to the complex types of materials, at this temperature, Burning of the electrolyte and diaphragm can easily cause severe local reactions in the pyrolysis furnace, causing the temperature to be out of control. The aluminum metal in the battery will undergo a thermite reaction when the temperature is above 600°C, causing the temperature to rise sharply in an instant and burning through the pyrolysis furnace. Bringing greater safety risks; ② At this temperature, the metal copper and aluminum in the battery are heavily oxidized, resulting in high impurity content in the battery powder, and during subsequent acid leaching, the oxides dissolve and produce a large amount of copper and aluminum slag. , which brings greater pressure to subsequent purification and purification.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for low-temperature thermal desorption and recycling of battery powder, which can achieve the purpose of separating the waste battery active materials from the current collector at a lower temperature.

According to one aspect of the present invention, a method for recovering battery powder by low-temperature thermal desorption is proposed, which includes the following steps:

S1: Used batteries are discharged, dismantled, and crushed to obtain crushed materials;

S2: React the crushed materials in a mixed atmosphere with a pressure of 3-8MPa and a temperature of 120-150°C. The mixed atmosphere is a mixed gas of CO ₂ , NO and O ₂ , with a volume ratio of 100: ( 10-15): (0-2);

S3: React the reaction material obtained in step S2 under negative pressure and 310-360°C, and then sort to obtain copper aluminum foil and battery powder.

In some embodiments of the present invention, in step S1, the particle size of the crushed material is 5 cm or less.

In some embodiments of the present invention, in step S1, the used battery is at least one of a ternary lithium ion battery, a lithium iron phosphate battery, a lithium cobalt oxide battery, a lithium manganate battery or a lithium nickel oxide battery.

In some embodiments of the present invention, in step S2, the reaction time is 3-5 h.

In some embodiments of the present invention, in step S2, the reaction is carried out in a pyrolysis furnace, and the filling rate of the crushed materials in the pyrolysis furnace is controlled to be 5-15%.

In some embodiments of the present invention, in step S3, the negative pressure ranges from -0.01 to -0.08MPa.

In some embodiments of the present invention, in step S3, the reaction time is 1-3 h.

In some embodiments of the present invention, after the reaction in step S2 is completed, the pressure in the pyrolysis furnace is released to normal pressure at a rate of 0.1-0.5 MPa/min, and then the vacuum pump is started to pump to the negative pressure.

In some embodiments of the present invention, in step S3, the reaction temperature is heated to the reaction temperature at a temperature rise rate of 5-10°C/min.

In some embodiments of the present invention, in the copper-aluminum foil obtained in step S3, the copper content is not less than 45wt%, and the aluminum content is not less than 35wt%.

In some embodiments of the present invention, the aluminum content in the battery powder obtained in step S3 is not higher than 0.5wt%.

In some embodiments of the present invention, in step S3, the sorting process is: using a double-layer screen for screening, the upper layer obtained is the copper aluminum foil, and the bottom layer is the battery powder.

According to a preferred embodiment of the present invention, it has at least the following beneficial effects:

1. In the solution of the present invention, in order to solve the problem that used batteries are prone to safety hazards and large-area oxidation of copper and aluminum at higher pyrolysis temperatures, a combined process of low-temperature, high-pressure pyrolysis and medium-temperature negative pressure pyrolysis is adopted, and the entire process is made The temperature of the process is controlled below 400°C, and medium-temperature negative pressure pyrolysis is carried out under anaerobic conditions, which avoids the burning of the electrolyte and diaphragm in the crushed materials, causing temperature out of control, protects the pyrolysis furnace, and reduces the oxidation of copper and aluminum. Degree.

2. When high-pressure mixed gas is introduced, NO is used as a single-electron free radical, which has high activity above 100°C. Under the catalysis of trace oxygen, it can randomly attack carbon atoms in organic polymers. The bonds break the polymer chain to form small molecular compounds, which lowers the thermal decomposition temperature of the polymer. Refer to the following reaction formula:

·NO+[-CH ₂ -CF ₂ -]→R1-CH ₂ -N=O+R ₂ -CF ₂ -N=O.

Taking advantage of the unique absorption properties of carbon dioxide of PVDF, a large volume expansion can occur, causing certain mechanical damage to PVDF, which facilitates NO to break the carbon-carbon bonds more deeply.

At the lower temperature of the present invention, chain scission of the polymer is achieved, oxidation of copper and aluminum is avoided, and the occurrence of thermite reaction is avoided.

3. During negative pressure pyrolysis, the chain-broken organic polymer can be decomposed and carbonized at a slightly higher temperature without heating to above 500°C, and the electrolyte in it can easily reach the boiling point under negative pressure. And enters the exhaust gas treatment system in a gaseous state. At the same time, copper and aluminum will not be oxidized, and the aluminothermic reaction will not occur, achieving the purpose of separation and desorption of battery powder and copper and aluminum foil.

Description of the drawings

The present invention will be further described below in conjunction with the accompanying drawings and examples, wherein:

Figure 1 is a process flow diagram of the present invention.

Detailed ways

The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. 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, other embodiments obtained by those skilled in the art without exerting creative efforts are all protection scope of the present invention.

Example 1

A method of low-temperature thermal desorption and recycling of battery powder. Refer to Figure 1. The specific process is:

Step 1: After discharge and disassembly, the waste ternary lithium-ion batteries are crushed into crushed materials with a particle size of less than 5cm;

Step 2: Add the crushed materials into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 5%, and introduce high-pressure mixed gas, seal it, control the air pressure in the pyrolysis furnace to 3MPa, the temperature to 120°C, continue for 5 hours, and high-pressure mixing Mixed gas of CO ₂ , NO and O ₂ , the volume ratio is 100:10:0.1;

Step 3: After the reaction is completed, release the pressure in the furnace to normal pressure at 0.1MPa/min, start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.01MPa, and raise the temperature to 310 at a heating rate of 5°C/min. ℃, lasting 3 hours;

Step 4: After the pyrolysis reaction is completed, the materials in the pyrolysis furnace are screened using a double-layer screen to obtain the upper layer of pyrolyzed copper and aluminum foil and the bottom layer of battery powder removed during the pyrolysis process.

Monitor the situation in the pyrolysis furnace: During high-pressure pyrolysis, only liquid droplets were observed on the surface of the crushed material, and the volume expanded slightly, and no other obvious changes were observed; during negative pressure pyrolysis, the temperature in the furnace remained constant. The powder falls off obviously and appears metallic luster.

Example 2

A method of low-temperature thermal desorption and recycling of battery powder. The specific process is:

Step 2: Add the crushed materials into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 10%, and introduce high-pressure mixed gas, seal it, control the air pressure in the pyrolysis furnace to 5MPa, and the temperature to 130°C for 4 hours; high-pressure mixing The mixed gas of CO ₂ , NO and O ₂ has a volume ratio of 100:13:1;

Step 3: After the reaction is completed, release the pressure in the furnace to normal pressure at 0.3MPa/min, start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.04MPa, and raise the temperature to 340 at a heating rate of 8°C/min. ℃, lasting 2h;

Step 4: After the pyrolysis reaction is completed, the materials in the pyrolysis furnace are screened using a double-layer screen to obtain the upper layer of pyrolyzed battery material and the bottom layer of battery powder removed during the pyrolysis process.

Example 3

Step 2: Add the crushed materials into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 15%, and introduce high-pressure mixed gas, seal it, control the air pressure in the pyrolysis furnace to 8MPa, and the temperature to 150°C for 3 hours; high-pressure mixing Mixed gas of CO ₂ , NO and O ₂ , the volume ratio is 100:15:2;

Step 3: After the reaction is completed, release the pressure in the furnace to normal pressure at 0.5MPa/min, start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.08MPa, and raise the temperature to 360 at a heating rate of 10°C/min. ℃, lasting 1h;

Comparative example 1

A method for pyrodesorption and recycling of battery powder. The difference from Example 1 is that low-temperature and high-pressure pyrolysis is not performed. The specific process is:

Step 2: Add the crushed materials into the pyrolysis furnace and control the filling rate of the pyrolysis furnace to 5%;

Step 3: Start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.01MPa, and raise the temperature to 310°C at a heating rate of 5°C/min for 3 hours;

Monitor the situation in the pyrolysis furnace: During negative pressure pyrolysis, the temperature in the furnace remains constant, molten droplets appear on the surface of the scraps, and they reunite after cooling, without obvious metallic luster.

Comparative example 2

A method for pyrodesorption and recycling of battery powder. The difference from Example 2 is that low-temperature and high-pressure pyrolysis is not performed. The specific process is:

Step 2: Add the crushed materials into the pyrolysis furnace and control the filling rate of the pyrolysis furnace to 10%;

Step 3: Start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.04MPa, and raise the temperature to 340°C at a heating rate of 8°C/min for 2 hours;

Comparative example 3

A method of thermal desorption and recycling of battery powder. The difference from Example 3 is that low-temperature and high-pressure pyrolysis is not performed. The specific process is:

Step 2: Add the crushed materials into the pyrolysis furnace and control the filling rate of the pyrolysis furnace to 15%;

Step 3: Start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.08MPa, and raise the temperature to 360°C at a heating rate of 10°C/min for 1 hour;

Comparative example 4

A method for thermal desorption and recycling of battery powder. The difference from Example 2 is that low-temperature and high-pressure pyrolysis is not performed, and the pyrolysis temperature in step 3 is increased. The specific process is:

Step 3: Start the vacuum pump to draw negative pressure, control the pressure in the pyrolysis furnace to -0.04MPa, and raise the temperature to 450°C at a heating rate of 8°C/min for 1 hour;

Monitor the situation in the pyrolysis furnace: During negative pressure pyrolysis, after the temperature in the furnace reaches 450°C, a flame appears. The temperature is uncontrolled and rises on its own. Sparks quickly appear and the material appears in a red molten state. After cooling, Afterwards, there was no obvious metallic luster.

The battery powder and metal foil obtained in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

Table 1

In Comparative Examples 1-3, a large amount of transition metal remains in the metal foil, indicating that the pyrolysis temperature is insufficient and the pyrolysis reaction is difficult to completely occur; in Comparative Example 4, a thermite reaction obviously occurs, and basically all the aluminum is oxidized into the black powder. , no formed aluminum foil was obtained.

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various modifications can be made without departing from the purpose of the present invention. Variety. In addition, the embodiments of the present invention and the features in the embodiments may be combined with each other without conflict.

Claims

A method for low-temperature thermal desorption and recycling of battery powder, which is characterized by including the following steps:

S1: Used batteries are discharged, dismantled, and crushed to obtain crushed materials;

S2: React the crushed materials in a mixed atmosphere with a pressure of 3-8MPa and a temperature of 120-150°C. The mixed atmosphere is a mixed gas of CO 2 , NO and O 2 , with a volume ratio of 100: ( 10-15): (0-2);

S3: React the reaction material obtained in step S2 under negative pressure and 310-360°C, and then sort to obtain copper aluminum foil and battery powder.
The method according to claim 1, characterized in that in step S1, the particle size of the crushed material is 5 cm or less.
The method according to claim 1, characterized in that in step S1, the used battery is at least one of a ternary lithium ion battery, a lithium iron phosphate battery, a lithium cobalt oxide battery, a lithium manganate battery or a lithium nickel oxide battery. A sort of.
The method according to claim 1, characterized in that in step S2, the reaction time is 3-5h.
The method according to claim 1, characterized in that in step S2, the reaction is carried out in a pyrolysis furnace, and the filling rate of the crushed materials in the pyrolysis furnace is controlled to 5-15%.
The method according to claim 1, characterized in that in step S3, the pressure of the negative pressure is -0.01~-0.08MPa.
The method according to claim 1, characterized in that in step S3, the reaction time is 1-3h.
The method according to claim 5, characterized in that after the reaction in step S2 is completed, the pressure in the pyrolysis furnace is released to normal pressure at a rate of 0.1-0.5MPa/min, and then the vacuum pump is started to pump to the negative pressure. .
The method according to claim 1, characterized in that, in step S3, the reaction temperature is heated to the reaction temperature at a heating rate of 5-10°C/min.
The method according to claim 1, characterized in that in step S3, the sorting process is: using a double-layer screen for screening, the upper layer obtained is the copper aluminum foil, and the bottom layer is the battery powder.