ES2995435B2 - METHOD FOR RECOVERING BATTERY POWDER BY LOW TEMPERATURE PYROLYSIS DESORPTION - Google Patents

Description

DESCRIPTION

METHOD FOR RECOVERING BATTERY POWDER BY PYROLYSIS DESORPTION

LOW TEMPERATURE

FIELD OF INVENTION

The present disclosure relates to the field of battery recovery and, in particular, relates to a method for recovering battery powder by low-temperature pyrolysis desorption.

BACKGROUND OF THE INVENTION

The lithium-ion battery has a complex structure and consists of a shell, a diaphragm, a positive electrode, a negative electrode, and other components. In the process of recovering waste batteries, different components need to be separated through a series of methods. Among them, the negative electrode consists of graphite, a bonding agent, a conductive agent, and a current collector copper foil, and the positive electrode is manufactured by coating active material powder, a bonding agent, and a conductive agent on a current collector aluminum foil, wherein the active material powder of the positive electrode mainly includes LiCoO<2>, LiNiO<2>, LiMnO<2>, LiFePO4, LiNixCoyMn<1>-x-yO<2>, and so on.

The pretreatment process for recovering waste lithium-ion batteries usually requires certain technical methods to desorb and separate the active material dust from the current collector.

Currently, the separation of active materials from the current collector mainly has three aspects: @ Based on the dissolvability of metallic aluminum in alkaline solution, immersing the positive electrode winding core in alkaline solution can achieve the purpose of separating the dust from the positive electrode of the current collector. This method has the advantages of low energy consumption and strong operability. However, the aluminum foil of the current collector enters the solution in the form of ions, which requires higher recovery. In addition, this process requires a large amount of alkaline solution. In order to avoid secondary pollution of the alkaline solution, neutralization treatment is required, which will require additional costs. To prevent dust contamination by the introduced alkaline solution, the desorbed active materials must be thoroughly washed or neutralized with acid during the filtration process.@By dissolving the PVDF binding agent in an organic solvent, the current collector metal foil can be recovered as a solid, but the organic solvent is usually expensive and not suitable for large-scale industrial applications.@Directly heating the battery to a specific temperature in air can deactivate the binding agent to achieve the purpose of separating the aluminum foil from the current collector, and it is also the most reported pyrolysis pretreatment process for recovering lithium batteries. CN103730704A discloses a method for treating secondary battery waste. CN111799522A discloses a recycling method of positive electrode material, the obtained positive electrode material and its application. CN113161640A discloses a system and method for recovering black powder from waste lithium batteries through multi-stage pyrolysis. CN111313121A discloses a method and system for preparing waste powder from positive and negative electrodes by crushing lithium batteries.

Pyrolysis pretreatment process is widely used in existing industrial production, but there are also some major problems, such as: @ The temperature of conventional pyrolysis is above 500 °C, due to the complex types of materials, at this temperature, the combustion of electrolyte and diaphragm occurs, which easily causes a violent local reaction in the pyrolysis furnace, resulting in an out of control temperature. When the aluminum metal in the battery is at a temperature above 600 °C, an aluminothermic reaction will occur, resulting in a sharp instantaneous temperature rise, burning through the pyrolysis furnace and bringing a great safety hazard. @ At this temperature, the metallic copper and aluminum in the battery are greatly oxidized, resulting in a high content of impurities in the battery powder. During subsequent acid leaching, the oxides are dissolved, resulting in a large amount of copper and aluminum slag, which puts great pressure on subsequent purification.

BRIEF DESCRIPTION OF THE INVENTION

The present invention aims to solve at least one of the aforementioned technical problems existing in the prior art. Therefore, the present invention provides a method for recovering battery dust by low-temperature pyrolysis desorption, which can achieve the purpose of separating the active material from the waste battery from the current collector at a relatively low temperature.

In one aspect, the present invention provides a method for recovering battery dust by low temperature pyrolysis desorption, comprising the following steps:

S1: Unload, disassemble and pulverize a waste battery to obtain pulverized material;

S2: Subjecting the pulverized material to a pyrolysis reaction in a mixed atmosphere at a gas pressure of 3-8 MPa and a temperature of 120-150 °C, wherein 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: Subject the reaction materials obtained in step S2 to a negative pressure pyrolysis reaction at 310-360 °C, and then sieve the reacted materials to obtain copper-aluminum foil and battery powder.

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

In some embodiments of the present invention, in step S1, the waste battery is at least one selected from the group consisting of a ternary lithium ion battery, a lithium iron phosphate battery, a lithium cobalt battery, a lithium manganate battery, or a lithium nickelate battery.

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

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

In some embodiments of the present invention, in step S3, the negative pressure has a value of -0.01 to -0.08MPa.

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

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

In some embodiments of the present invention, in step S3, the reaction temperature is achieved by heating at a 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 45% by weight, and the aluminum content is not less than 35% by weight.

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

In some embodiments of the present invention, in step S3, the screening process comprises: performing screening by using a double-layer sieve, and the material obtained in the upper layer is the copper-aluminum foil, and the material obtained in the lower 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 embodiments of the present invention, in view of the problem that the waste battery is prone to safety hazards and large-area oxidation of copper and aluminum at a relatively high pyrolysis temperature, a combined process of low-temperature, high-pressure pyrolysis and medium-temperature negative pressure pyrolysis is adopted, in which the temperature of the whole process is controlled below 400 ° C, and the medium-temperature negative pressure pyrolysis is carried out under oxygen-free conditions, so as to prevent combustion of the electrolyte and the diaphragm in the pulverized material and the subsequent temperature runaway phenomenon, protecting the pyrolysis furnace and reducing the oxidation degree of copper and aluminum.

2. Under high-pressure mixed gas conditions, NOx acts as a single-electron free radical, exhibiting high activity at temperatures above 100°C. It can randomly attack carbon-carbon bonds in organic polymers under the catalysis of trace oxygen, causing the polymer to cleave into small molecular compounds and reducing the thermal decomposition temperature of the polymer. The reaction formula is as follows:

NO+[-CH2-CF2-HR1-CH2-N=O+ R2-CF2-N=O.

The unique absorption characteristics of PVDF to carbon dioxide can cause large volume expansion, leading to some mechanical damage to the PVDF, which leads to deeper cleavage of carbon-carbon bonds by NO.

In the present invention, under the relatively low temperature, the cleavage of polymer is carried out, the oxidation of copper and aluminum is avoided, and the occurrence of aluminothermic reaction is further avoided.

3. During negative pressure pyrolysis, the organic polymer after cleavage can be decomposed and carbonized at a slightly high temperature without the need to heat above 500°C. The electrolyte within can easily reach the boiling point under negative pressure and enter the waste gas processing system in a gaseous state. Furthermore, copper and aluminum are not oxidized, and the aluminothermic reaction does not occur, achieving the purpose of separating and desorbing battery dust from copper and aluminum foil.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below in conjunction with the figures and embodiments, wherein:

FIGURE 1 is the flow diagram of the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The concept of the present invention and the technical effects produced by the present invention will be clearly and fully described below with reference to examples, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the examples described are only a portion of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

Example 1

A method is provided for recovering battery dust by low-temperature pyrolysis desorption. Referring to FIGURE 1, the specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added into a pyrolysis furnace with a filling rate controlled to be 5%. Then, the pyrolysis furnace was introduced with a high-pressure mixed gas and then sealed, in which the air pressure was controlled to be 3MPa, and the temperature was controlled to be 120 ° C, holding for 5 h, where the high-pressure mixed gas was a mixed gas of CO<2>, NO and O<2> with a volume ratio of 100:10:0.1;

Step 3: After the reaction was completed, the pressure in the furnace was released to normal pressure at a rate of 0.1 MPa/min, and a vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.01 MPa, and the temperature was raised to 310 °C at a heating rate of 5 °C/min, holding for 3 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the copper-aluminum foil after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During high-pressure pyrolysis, only droplets appeared on the surface of the powdered material, and the volume expanded slightly, while no other obvious changes were observed. During negative-pressure pyrolysis, the temperature in the furnace remained constant, the powder material desorbed significantly, and a metallic luster appeared.

Example 2

A method is provided for recovering battery dust by low-temperature pyrolysis desorption. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added into a pyrolysis furnace with a filling rate controlled to be 10%. Then, the pyrolysis furnace was filled with a high-pressure mixed gas and then sealed, in which the air pressure was controlled to be 5MPa, and the temperature was controlled to be 130 °C, holding for 4 h, where the high-pressure mixed gas was a mixed gas of CO<2>, NO and O<2> with a volume ratio of 100:13:1;

Step 3: After the reaction was completed, the pressure in the furnace was released to normal pressure at a rate of 0.3 MPa/min, and a vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.04 MPa, and the temperature was raised to 340 °C at a heating rate of 8 °C/min, holding for 2 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During high-pressure pyrolysis, only droplets appeared on the surface of the powdered material, and the volume expanded slightly, while no other obvious changes were observed. During negative-pressure pyrolysis, the temperature in the furnace remained constant, the powder material desorbed significantly, and a metallic luster appeared.

Example 3

A method is provided for recovering battery dust by low-temperature pyrolysis desorption. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added into a pyrolysis furnace with a filling rate controlled to be 15%. Then, the pyrolysis furnace was filled with a high-pressure mixed gas and then sealed, in which the air pressure was controlled to be 8MPa, and the temperature was controlled to be 150 °C, holding for 3 h, where the high-pressure mixed gas was a mixed gas of CO<2>, NO and O<2> with a volume ratio of 100:15:2;

Step 3: After the reaction was completed, the pressure in the furnace was released to normal pressure at a rate of 0.5 MPa/min, and a vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.08 MPa, and the temperature was raised to 360 °C at a heating rate of 10 °C/min, holding for 1 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During high-pressure pyrolysis, only droplets appeared on the surface of the powdered material, and the volume expanded slightly, while no other obvious changes were observed. During negative-pressure pyrolysis, the temperature in the furnace remained constant, the powder material desorbed significantly, and a metallic luster appeared.

Comparative example 1

A method is provided for recovering battery dust by pyrolysis desorption. This method differs from Example 1 in that low-temperature, high-pressure pyrolysis was not performed. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added to a pyrolysis furnace with a filling rate controlled to be 5%;

Step 3: A vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.01 MPa, and the temperature was raised to 310 °C at a heating rate of 5 °C/min, holding for 3 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During negative pressure pyrolysis, the temperature in the furnace remained constant, molten droplets appeared on the surface of the pulverized material, which agglomerated after cooling, and no obvious metallic luster appeared.

Comparative example 2

A method is provided for recovering battery dust by pyrolysis desorption. This method differs from Example 2 in that low-temperature, high-pressure pyrolysis was not performed. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added to a pyrolysis furnace with a filling rate controlled to be 10%;

Step 3: A vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.04 MPa, and the temperature was raised to 340 °C at a heating rate of 8 °C/min, holding for 2 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During negative pressure pyrolysis, the temperature in the furnace remained constant, molten droplets appeared on the surface of the pulverized material, which agglomerated after cooling, and no obvious metallic luster appeared.

Comparative example 3

A method is provided for recovering battery dust by pyrolysis desorption. This method differs from Example 3 in that low-temperature, high-pressure pyrolysis was not performed. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added to a pyrolysis furnace with a filling rate controlled to be 15%;

Step 3: A vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.08 MPa, and the temperature was raised to 360 °C at a heating rate of 10 °C/min, holding for 1 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During negative pressure pyrolysis, the temperature in the furnace remained constant, molten droplets appeared on the surface of the pulverized material, which agglomerated after cooling, and no obvious metallic luster appeared.

Comparative example 4

A method is provided for recovering battery dust by pyrolysis desorption. This method differs from Example 2 in that low-temperature, high-pressure pyrolysis was not performed, and the pyrolysis temperature was increased in step 3. The specific process is as follows:

Step 1: A waste lithium-ion ternary battery was discharged, disassembled, and then pulverized into pulverized material with a particle size of less than 5 cm;

Step 2: The pulverized material was added to a pyrolysis furnace with a filling rate controlled to be 10%;

Step 3: A vacuum pump was started to pump the furnace to negative pressure. The pressure in the pyrolysis furnace was controlled at -0.04 MPa, and the temperature was raised to 450 °C at a heating rate of 8 °C/min, holding for 1 h;

Step 4: After the pyrolysis reaction was completed, the materials in the pyrolysis furnace were sieved with a double-layer sieve to obtain the battery material after pyrolysis in the upper layer, and the battery powder was desorbed during the pyrolysis process in the lower layer.

Monitoring the conditions in the pyrolysis furnace: During negative pressure pyrolysis, after the temperature in the furnace reached 450 °C, a flame appeared, the temperature was out of control and rose by itself, sparks splashed rapidly, and the material was in a reddish molten state and had no obvious metallic luster after cooling.

The battery powders and metal foils 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 remained in the metal foil, indicating that the pyrolysis temperature was insufficient, making it difficult to fully complete the pyrolysis reaction. In Comparative Example 4, the aluminothermic reaction occurred clearly, and all the aluminum was essentially oxidized to black powder, and no aluminum foil was formed.

Claims (10)

1. A method for recovering battery dust by low-temperature pyrolysis desorption, characterized in that it comprises the following steps: S1: Unloading, disassembling and pulverizing a waste battery to obtain pulverized material; S2: Subjecting the pulverized material to a pyrolysis reaction in a mixed atmosphere at a gas pressure of 3-8 MPa and a temperature of 120-150 °C, wherein 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: Subject the reaction materials obtained in step S2 to a pyrolysis reaction under negative pressure at 310-360 °C, and then sieve the reacted materials to obtain copper-aluminum foil and battery powder. 2. The method according to claim 1, characterized in that in step S1, the particle size of the pulverized material is less than 5 cm. 3. The method according to claim 1, characterized in that in step S1, the waste battery is at least one selected from the group consisting of a ternary lithium ion battery, a lithium iron phosphate battery, a lithium cobalt battery, a lithium manganate battery, or a lithium nickelate battery. 4. The method according to claim 1, characterized in that in step S2, the duration of the pyrolysis reaction is 3-5 h. 5. The method according to claim 1, characterized in that in step S2, the pyrolysis reaction is carried out in a pyrolysis furnace, and the filling rate of the pulverized material in the pyrolysis furnace is controlled to be 5-15%. 6. The method according to claim 1, characterized in that in step S3, the negative pressure has a value of -0.01 to -0.08MPa. 7. The method according to claim 1, characterized in that in step S3, the duration of the pyrolysis reaction is 1-3 h. 8. The method according to claim 5, characterized in that after the pyrolysis reaction is completed in step S2, the pressure in the pyrolysis furnace is released to normal pressure at a rate of 0.1-0.5 MPa/min, and then a vacuum pump is started to pump the pyrolysis furnace to the negative pressure. 9. The method according to claim 1, characterized in that in step S3, the reaction temperature is achieved by heating at a rate of 5-10 °C/min. 10. The method according to claim 1, characterized in that in step S3, the screening process comprises: performing screening by using a double-layer sieve, and the material obtained in the upper layer is the copper-aluminum foil, and the material obtained in the lower layer is the battery powder.