Method for producing hydrogen and directionally reducing valence metal through catalytic pyrolysis of waste ternary lithium battery diaphragm

Abstract

The invention discloses a method for hydrogen production and directional reduction of valence metal through catalytic pyrolysis of a waste ternary lithium battery diaphragm, and belongs to the field of waste lithium battery recovery industries. A shell, positive and negative electrode materials, a current collector, a diaphragm and an electrolyte are obtained after a waste ternary lithium battery is discharged, disassembled, crushed and screened; wherein the diaphragm is a volatile component released by reacting a raw material in the pyrolysis unit in an inert atmosphere; taking a small part (less than 10%) of the positive electrode material as a catalyst, and introducing volatile components into a catalytic reforming unit for reaction to obtain hydrogen-rich gas; the hydrogen-rich gas is introduced into a medium-temperature reduction unit to realize reduction of high-valence metals such as nickel, cobalt and manganese in most (more than 80%) of the positive electrode material; and taking solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder, and adding the reduced black powder into an acid solution without an additional reducing agent to leach and recover valuable metals. Therefore, by adopting the method, the internal source diaphragm and the positive electrode material of the lithium battery can be effectively utilized, high-yield hydrogen-rich gas can be obtained, the catalyst has high stability, the problems that a conventional catalyst is easy to sinter and poor in reusability are solved, the recovery rate of valuable metal is 90% or above, and the method is suitable for industrial production. And the problems of high cost and serious secondary pollution caused by introduction of an external reducing agent are solved.

Description

Technical Field

[0001] The present invention belongs to the field of waste lithium - ion battery recycling industry, and particularly relates to a method for catalytic pyrolysis of waste ternary lithium - ion battery separator to produce hydrogen and directional reduction of valuable metals. Background Art

[0002] With the continuous growth of the demand for mobile energy sources in electric vehicles and electronic products, ternary lithium - ion batteries are increasingly widely used due to their wide operating temperature range, high conversion efficiency, large energy density, long cycle life and other characteristics. However, when the performance of lithium - ion batteries declines, a large number of retired lithium - ion batteries will inevitably be generated. It is reported that by 2030, the global consumption of lithium - ion batteries will exceed 11 million tons. On the one hand, waste lithium - ion batteries contain a large amount of valuable metals (such as Li, Ni, Co, Mn, etc.) and other recyclable materials, with high potential value. On the other hand, if not properly treated, it will cause serious environmental problems such as heavy metal pollution and plastic waste. Therefore, the recycling of waste lithium - ion batteries meets both economic and environmental requirements.

[0003] The hydrometallurgical method is widely used for recovering valuable metals from waste lithium - ion batteries due to its advantages of high efficiency and low energy consumption. The leaching process is usually carried out in an organic or inorganic acid solution. However, since the transition metals in lithium - ion batteries exist in a high - valence state and are not easily dissolved, the leaching efficiency is low. Therefore, a reducing agent must be used to reduce the high - valence transition metals to a low - valence state for dissolution and leaching. Generally, inorganic (such as H2O2, Na2SO3) or organic (such as glucose, sucrose, cellulose or citric acid) reducing agents are used to reduce high - valence metals to improve the leaching efficiency, but these reducing agents are expensive and easily cause secondary pollution.

[0004] In addition, the separator generated during the disassembly process of waste lithium - ion batteries will cause plastic pollution, and the existing lithium - ion battery disassembly and sorting processes do not effectively utilize it. Therefore, by pyrolyzing the waste ternary lithium - ion battery separator and using the pyrolysis volatile components for catalytic reforming to produce hydrogen - rich reducing gas for directional reduction of transition metals, the transformation of high - valence nickel, cobalt, and manganese to low - valence states can be realized, and the effective utilization of the endogenous separator also avoids the consumption of external carbon sources. The transformation of the valence state of transition metals helps to improve their leaching efficiency and the recovery rate of cathode materials. Therefore, based on the full utilization of the catalytic performance of metals in lithium - ion batteries, the present invention realizes the thermal reforming of the endogenous separator of lithium - ion batteries to produce hydrogen, and then uses hydrogen - rich gas to reduce more cathode materials, which can not only promote the full utilization of waste lithium - ion battery separators and avoid plastic pollution, but also realize the reduction and leaching of cathode materials. Summary of the Invention

[0005] Aiming at the defects existing in the above-mentioned existing waste lithium battery recycling technologies, the purpose of the present invention is to provide a method for catalytic pyrolysis of waste ternary lithium battery separators to produce hydrogen and directionally reduce valuable metals, aiming to make full use of the catalytic performance of the waste ternary lithium battery cathode material and the hydrogen-rich reducing gas generated by the catalytic reforming of the separator, and solve the problems of plastic pollution caused by the lithium battery separator and the consumption of reducing agents required for high-valent transition metals. Therefore, the entire recycling process is an efficient, economical, environmentally friendly route, avoiding the consumption of expensive reducing agents, and making full use of waste resources and other advantages.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for catalytic pyrolysis of waste ternary lithium battery separators to produce hydrogen and directionally reduce valuable metals, comprising a discharging unit, a disassembling, crushing and screening unit, a pyrolysis unit, a catalytic reforming unit, a medium-temperature reduction unit and a leaching unit, and including the following steps:

[0008] 1) After the waste ternary lithium battery is discharged, disassembled, crushed and screened, the outer shell, positive and negative electrode materials, current collectors, separators and electrolytes are obtained;

[0009] 2) Among them, the separator is used as a raw material to react in the pyrolysis unit under an inert atmosphere to release volatile components;

[0010] 3) Take a small part (<10%) of the positive electrode material as a catalyst, and introduce the volatile components into the catalytic reforming unit to react to obtain hydrogen-rich gas;

[0011] 4) Introduce the hydrogen-rich gas into the medium-temperature reduction unit to reduce the high-valent metals such as nickel, cobalt and manganese in most (>80%) of the positive electrode materials;

[0012] 5) Use the solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder, and add the reduced black powder to an acid solution without an external reducing agent to leach and recover valuable metals.

[0013] A further improvement of the method of the present invention lies in that in the step of obtaining the outer shell, positive and negative electrode materials, current collectors, separators and electrolytes after the waste ternary lithium battery is discharged, disassembled, crushed and screened, the waste ternary lithium battery is discharged by soaking in a 5 wt.% NaCl solution for 48 h. After the discharged waste lithium battery is naturally air-dried, it is manually disassembled to obtain each component. The selected pure positive and negative electrode sheets are respectively crushed by a universal crusher, and the crushing time is 5 s each time. After the positive and negative electrode wastes are crushed, they are screened through a 200-mesh sieve to remove the current collectors to obtain the positive and negative electrode materials.

[0014] A further improvement of the method of the present invention lies in that protective gases are used in the pyrolysis unit, the catalytic reforming unit and the medium-temperature reduction unit, which can be one or several of nitrogen, helium, argon, and xenon, and the flow rate of the protective gas is 50-100 mL / min.

[0015] A further improvement of the method of the present invention lies in that the pyrolysis unit, the catalytic reforming unit and the medium-temperature reduction unit are carried out in a three-stage furnace. Membrane pyrolysis is carried out in the first-stage furnace, catalytic reforming of pyrolysis volatiles and water vapor with the cathode material as the catalyst is carried out in the second-stage furnace, and medium-temperature reduction of the cathode material with hydrogen-rich gas is carried out in the third-stage furnace.

[0016] A further improvement of the method of the present invention lies in that the membrane is used as a raw material, and in the step of releasing volatiles by reaction in the pyrolysis unit under an inert atmosphere, the membrane pyrolysis temperature is 500-600 °C.

[0017] A further improvement of the method of the present invention lies in that in the step of taking a small part (<10%) of the cathode material as a catalyst and introducing the volatiles into the catalytic reforming unit to react to obtain hydrogen-rich gas, the mass ratio of the catalyst to the membrane is 0.25-2:1, the water vapor flow rate is 0-8 mL / h, the catalytic reforming temperature is 600-800 °C, and the reaction is carried out at a constant temperature for 1 h to obtain hydrogen-rich reducing gas.

[0018] A further improvement of the method of the present invention lies in that in the step of introducing the hydrogen-rich gas into the medium-temperature reduction unit to reduce the high-valence metals such as nickel, cobalt, and manganese in most (>80%) of the cathode material, the reduction temperature is 500-800 °C, and the mass ratio of the cathode material to the membrane is 1-10:1.

[0019] A further improvement of the method of the present invention lies in that in the step of taking the solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder and adding the reduced black powder to an acid solution without an external reducing agent for leaching to recover valuable metals, sulfuric acid solution is used to acid-leach the reduced black powder to recover valuable metals, the sulfuric acid concentration is 4 mol / L, the leaching time is 30 min, the temperature of water bath heating is 80 °C, the stirring speed is 150 r / min, the reduced black powder is mixed with the sulfuric acid solution, and the mixing ratio is 0.1 g / L.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The method for catalytic pyrolysis of waste ternary lithium battery membranes to produce hydrogen and direct reduction of valuable metals provided by the present application uses the cathode material as a catalyst and the membrane as a raw material, and obtains hydrogen-rich gas through catalytic reforming of membrane pyrolysis volatiles and water vapor. The gas yield is up to 74.25 mmol / g at most, and the hydrogen yield is up to 40.29 mmol / g at most.

[0022] 2) The method for catalytic pyrolysis of the diaphragm of waste ternary lithium batteries to produce hydrogen and directionally reduce valuable metals provided by this application. As the positive electrode material of the catalyst (LiNi x Co y Mn 1-x-y O2) mainly produces nickel-cobalt alloy and manganese oxide after the catalytic reforming reaction. Due to the strong stability of the alloy catalyst, the problems of easy sintering and poor reusability of conventional catalysts are avoided, and the cost of catalyst use is reduced.

[0023] 3) The method for catalytic pyrolysis of the diaphragm of waste ternary lithium batteries to produce hydrogen and directionally reduce valuable metals provided by this application reduces the transition metals in the positive electrode material by catalytic reforming the pyrolysis volatiles of the diaphragm to produce hydrogen-rich gas, without introducing external reducing agents and realizing the reduction of transition metals in the positive electrode material. The recovery rates of valuable metals Li, Ni, Co, and Mn after acid leaching reach 95.79%, 98.81%, 98.41%, and 90.31% respectively, promoting the recycling of valuable metals in ternary lithium batteries and solving the problems of high cost and serious secondary pollution caused by the introduction of external reducing agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.

[0026] Figure 1 is the flowchart of the method of the present invention;

[0027] Figure 2 is the SEM image of the positive electrode material reduced by hydrogen-rich gas at different reduction temperatures

[0028] Figure 3 is the XRD pattern of the positive electrode material reduced by hydrogen-rich gas at different reduction temperatures

[0029] Figure 4 is the SEM image of hydrogen-rich gas at different ratios of positive electrode material to diaphragm

[0030] Figure 5 is the XRD pattern of hydrogen-rich gas at different ratios of positive electrode material to diaphragm DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described in detail below with reference to the drawings and embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby. The materials, methods, equipment, and devices described herein are understood to be commercially available unless otherwise specified.

[0033] A method for catalytic pyrolysis of waste ternary lithium battery separator to produce hydrogen and directional reduction of valuable metals, comprising the following steps:

[0034] 1) After the waste ternary lithium battery is discharged, disassembled, crushed and screened, the outer shell, positive and negative electrode materials, current collector, separator and electrolyte are obtained;

[0035] 2) Among them, the separator is used as the raw material to react in a pyrolysis unit under an inert atmosphere to release volatile components;

[0036] 3) Take a small part (<10%) of the positive electrode material as the catalyst, and introduce the volatile components into the catalytic reforming unit to react to obtain hydrogen-rich gas;

[0037] 4) Introduce the hydrogen-rich gas into the medium-temperature reduction unit to realize the reduction of high-valence metals such as nickel, cobalt and manganese in most (>80%) of the positive electrode materials;

[0038] 5) Take the solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder, and add the reduced black powder to an acid solution without an external reducing agent for leaching to recover valuable metals.

[0039] In the following embodiments, the catalytic pyrolysis of the waste ternary lithium battery separator and the directional reduction of valuable metals are carried out in a three-stage furnace. The separator pyrolysis is carried out in the first-stage furnace, the steam catalytic reforming of the pyrolysis volatile components with the positive electrode material as the catalyst is carried out in the second-stage furnace, and the medium-temperature reduction of the positive electrode material with the hydrogen-rich gas is carried out in the third-stage furnace.

[0040] Preferably, the pyrolysis temperature of the separator in step 2) is 500-600 °C.

[0041] Preferably, in the steam catalytic reforming of the pyrolysis volatile components in step 3), the mass ratio of the catalyst to the separator is 0.25-2:1, the steam flow rate is 0-8 mL, the catalytic reforming temperature is 600-800 °C, and the reaction is carried out at a constant temperature for 1 h to obtain hydrogen-rich reduction gas.

[0042] Preferably, in step 4), the hydrogen-rich reduction gas reduces the high-valence metals such as nickel, cobalt and manganese in the positive electrode material, the reduction temperature is 500-800 °C, and the mass ratio of the positive electrode material to the separator is 1-10:1.

[0043] Preferably, in steps 2) and 3), a protective gas can be used in the catalytic pyrolysis and reduction stages of the waste ternary lithium battery, which can be one or several of nitrogen, helium, argon, and xenon, and the flow rate of the protective gas is 50-100 mL / min.

[0044] Example 1

[0045] For the method for pyrolyzing waste lithium battery separator to produce hydrogen and directionally reducing valuable metals in the embodiment of the present invention, please refer to specifically Figure 1, including the following steps:

[0046] 1) After the waste ternary lithium battery is discharged, disassembled, crushed and screened, the shell, positive and negative electrode materials, current collector, separator and electrolyte are obtained.

[0047] 2) The separator reacts as a raw material in a pyrolysis unit under an inert atmosphere to release volatile components, and the pyrolysis temperature is 500 °C;

[0048] 3) The volatile components are introduced into a catalytic reforming unit containing the positive electrode material. When the ratio of the catalyst to the separator is 2:1, the reforming temperature is 800 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min, the catalytic pyrolysis reaction of the separator is carried out. The volatile components generated by the pyrolysis of the separator enter the catalytic reforming area where the positive electrode material is located and react completely to obtain a rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 59.13 mmol / g 隔膜 , where the hydrogen yield is 29.75 mmol / g 隔膜 .

[0049] 4) The hydrogen-rich gas is introduced into a medium-temperature reduction unit to reduce most (>80%) of the high-valent metals such as nickel, cobalt, and manganese in the positive electrode material. The reduction temperature is 500 °C, and the mass ratio of the positive electrode material to the separator is 2:1. Figure 3 The XRD pattern of the reduced positive electrode material is shown, and nickel, cobalt, and manganese are not completely reduced.

[0050] 5) The solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit are used as reduced black powder. The reduced black powder is added to an acid solution without an external reducing agent for leaching to recover valuable metals. The sulfuric acid concentration is 4 mol / L, the leaching time is 30 min, the temperature of the water bath heating is 80 °C, the stirring speed is 150 r / min, the reduced black powder is mixed with the sulfuric acid solution, and the mixing ratio is 0.1 g / L. The recovery rates of valuable metals Li, Ni, Co, and Mn reach 95.79%, 98.81%, 98.41%, and 90.31% respectively.

[0051] Example 2

[0052] The difference between this example and Example 1 is that: using the positive electrode material as the catalyst and the separator as the raw material, when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 700 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min, the catalytic pyrolysis reaction of the separator is carried out. The volatile components generated by the pyrolysis of the separator enter the catalytic reforming area where the positive electrode material is located and react completely to obtain a rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 42.36 mmol / g 隔膜 , where the hydrogen yield is 23.03 mmol / g 隔膜。

[0053] Example 3

[0054] The difference between this example and Example 1 is that: using the positive electrode material as the catalyst and the separator as the raw material, when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 600 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min, the catalytic pyrolysis reaction of the separator is carried out. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 10.70 mmol / g 隔膜 , and the hydrogen yield is 4.47 mmol / g 隔膜 。

[0055] Example 4

[0056] The difference between this example and Example 1 is that: using the positive electrode material as the catalyst and the separator as the raw material, when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 0 mL / h, and the carrier gas N2 flow rate is 100 mL / min, the catalytic pyrolysis reaction of the separator is carried out. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 34.83 mmol / g 隔膜 , and the hydrogen yield is 13.80 mmol / g 隔膜 。

[0057] Example 5

[0058] The difference between this example and Example 1 is that: using the positive electrode material as the catalyst and the separator as the raw material, when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 2 mL / h, and the carrier gas N2 flow rate is 100 mL / min, the catalytic pyrolysis reaction of the separator is carried out. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a hydrogen-rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 57.38 mmol / g 隔膜 , and the hydrogen yield is 27.85 mmol / g 隔膜 。

[0059] Example 6

[0060] The difference between this example and Example 1 is as follows: Using the positive electrode material as the catalyst and the separator as the raw material, a catalytic pyrolysis reaction of the separator is carried out when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 8 mL / h, and the carrier gas N2 flow rate is 100 mL / min. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a hydrogen-rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 51.88 mmol / g 隔膜 , and the hydrogen yield is 25.63 mmol / g 隔膜 .

[0061] Example 7

[0062] The difference between this example and Example 1 is as follows: Using the positive electrode material as the catalyst and the separator as the raw material, a catalytic pyrolysis reaction of the separator is carried out when the ratio of the catalyst to the separator is 2:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a hydrogen-rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 74.25 mmol / g 隔膜 , and the hydrogen yield is 40.29 mmol / g 隔膜 .

[0063] Example 8

[0064] The difference between this example and Example 1 is as follows: Using the positive electrode material as the catalyst and the separator as the raw material, a catalytic pyrolysis reaction of the separator is carried out when the ratio of the catalyst to the separator is 1:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the positive electrode material is located and reacts completely to obtain a hydrogen-rich reducing gas. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 57.38 mmol / g 隔膜 , and the hydrogen yield is 27.85 mmol / g 隔膜 .

[0065] Example 8

[0066] The difference between this example and Example 1 is as follows: Using the cathode material as the catalyst and the separator as the raw material, a catalytic pyrolysis reaction of the separator is carried out when the ratio of the catalyst to the separator is 0.25:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the cathode material is located, and a hydrogen-rich reducing gas is completely obtained through reaction. The collected gas is analyzed by a gas chromatograph, and the syngas yield is 26.65 mmol / g 隔膜 , where the hydrogen yield is 8.73 mmol / g 隔膜 .

[0067] Example 9

[0068] The difference between this example and Example 1 is as follows: Using the cathode material as the catalyst and the separator as the raw material, a catalytic pyrolysis reaction of the separator is carried out when the ratio of the catalyst to the separator is 0.5:1, the pyrolysis temperature is 500 °C, the reforming temperature is 800 °C, the water vapor flow rate is 4 mL / h, and the carrier gas N2 flow rate is 100 mL / min. The volatile matter generated by the pyrolysis of the separator enters the catalytic reforming area where the cathode material is located, and a hydrogen-rich reducing gas is completely obtained through reaction. A 10-cycle stability test is carried out without the catalyst regeneration process. The gas collected in each cycle experiment is analyzed by a gas chromatograph, and the syngas yield fluctuation value is between 27 and 54 mmol / g 隔膜 , where the hydrogen yield fluctuation value is between 21 and 37 mmol / g 隔膜 .

[0069] Example 10

[0070] The difference between this example and Example 1 is as follows: A catalytic pyrolysis reaction of the separator is carried out under the reaction conditions of a catalyst-to-separator ratio of 0.5:1, a pyrolysis temperature of 500 °C, a reforming temperature of 800 °C, a water vapor flow rate of 4 mL / h, and a carrier gas N2 flow rate of 100 mL / min to obtain a hydrogen-rich reducing gas. The hydrogen-rich reducing gas reduces the high-valent metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valent states. The reduction temperature is 600 °C, and the mass ratio of the cathode material to the separator is 2:1 Figure 3 The XRD pattern of the reduced cathode material is shown as follows. Lithium nickel cobalt manganate is reduced to nickel cobalt alloy and manganese oxide

[0071] Example 11

[0072] The difference between this example and Example 1 is that a hydrogen-rich reducing gas is obtained by performing a catalytic pyrolysis reaction of the diaphragm under the reaction conditions of a catalyst-to-diaphragm ratio of 0.5:1, a pyrolysis temperature of 500 °C, a reforming temperature of 800 °C, a water vapor flow rate of 4 mL / h, and a carrier gas N2 flow rate of 100 mL / min. The hydrogen-rich reducing gas reduces the high-valence metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valence states, with a reduction temperature of 700 °C and a mass ratio of the cathode material to the diaphragm of 2:1. Figure 3 The XRD pattern of the reduced cathode material is shown, and lithium nickel cobalt manganate is reduced to nickel cobalt alloy and manganese oxide.

[0073] Example 12

[0074] The difference between this example and Example 1 is that a hydrogen-rich reducing gas is obtained by performing a catalytic pyrolysis reaction of the diaphragm under the reaction conditions of a catalyst-to-diaphragm ratio of 0.5:1, a pyrolysis temperature of 500 °C, a reforming temperature of 800 °C, a water vapor flow rate of 4 mL / h, and a carrier gas N2 flow rate of 100 mL / min. The hydrogen-rich reducing gas reduces the high-valence metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valence states, with a reduction temperature of 800 °C and a mass ratio of the cathode material to the diaphragm of 2:1. Figure 3 The XRD pattern of the reduced cathode material is shown, and lithium nickel cobalt manganate is reduced to nickel cobalt alloy and manganese oxide.

[0075] Example 13

[0076] The difference between this example and Example 1 is that a hydrogen-rich reducing gas is obtained by performing a catalytic pyrolysis reaction of the diaphragm under the reaction conditions of a catalyst-to-diaphragm ratio of 0.5:1, a pyrolysis temperature of 500 °C, a reforming temperature of 800 °C, a water vapor flow rate of 4 mL / h, and a carrier gas N2 flow rate of 100 mL / min. The hydrogen-rich reducing gas reduces the high-valence metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valence states, with a reduction temperature of 700 °C and a mass ratio of the cathode material to the diaphragm of 1:1. Figure 5 The XRD pattern of the reduced cathode material is shown, and lithium nickel cobalt manganate is reduced to nickel cobalt alloy and manganese oxide.

[0077] Example 14

[0078] The difference between this example and Example 1 is that a hydrogen-rich reducing gas is obtained by performing a catalytic pyrolysis reaction of the diaphragm under the reaction conditions of a catalyst-to-diaphragm ratio of 0.5:1, a pyrolysis temperature of 500 °C, a reforming temperature of 800 °C, a water vapor flow rate of 4 mL / h, and a carrier gas N2 flow rate of 100 mL / min. The hydrogen-rich reducing gas reduces the high-valence metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valence states, with a reduction temperature of 700 °C and a mass ratio of the cathode material to the diaphragm of 4:1. Figure 5The XRD pattern of the reduced cathode material is shown. Lithium nickel cobalt manganate is partially reduced to nickel cobalt alloy and partially reduced to nickel oxide and cobalt oxide.

[0079] Example 15

[0080] The difference between this example and Example 1 is that the catalytic pyrolysis reaction of the separator is carried out under the reaction conditions of the ratio of catalyst to separator being 0.5:1, pyrolysis temperature of 500 °C, reforming temperature of 800 °C, water vapor flow rate of 4 mL / h, and carrier gas N2 flow rate of 100 mL / min to obtain hydrogen-rich reducing gas. The hydrogen-rich reducing gas reduces the high-valent metals such as nickel, cobalt, and manganese in the ternary lithium battery to low-valent states. The reduction temperature is 700 °C, and the mass ratio of the cathode material to the separator is 10:1. Figure 5 The XRD pattern of the reduced cathode material is shown. Lithium nickel cobalt manganate is partially reduced to nickel cobalt alloy and partially reduced to nickel oxide and cobalt oxide.

[0081] It can be seen from Examples 1-8 that the catalytic reforming temperature, water vapor flow rate, and mass ratio of catalyst to separator all affect the hydrogen-rich gas yield of the catalytic reforming reaction. When the reforming temperature increases from 600 °C to 800 °C, the hydrogen-rich gas yield increases significantly. When it rises to 900 °C, the gas yield decreases due to catalyst sintering; water vapor promotes the water-gas shift reaction and methane steam reforming reaction, etc., and the hydrogen-rich gas yield increases significantly; while the increase in the mass ratio of catalyst to separator promotes the catalytic reforming reaction of the separator, and a higher hydrogen-rich gas yield per unit mass of the separator is obtained. It can be seen from Example 9 that the cathode material has strong stability as a catalyst. In summary, the hydrogen-rich gas quality and yield prepared by the catalytic pyrolysis technology of waste ternary lithium battery separators proposed by the present invention have achieved remarkable effects and have strong catalytic stability.

[0082] It can be seen from Example 1 and Examples 10-15 that starting from 600 °C, the transition metals in the cathode material can be completely reduced by the hydrogen-rich gas. When the ratio of the cathode material to the separator is less than 2:1, nickel and cobalt can be completely reduced to nickel cobalt alloy. When the ratio increases to more than 4:1, nickel and cobalt are partially reduced to nickel cobalt alloy and partially reduced to nickel oxide and cobalt oxide. However, generally, the leaching rates of valuable metals Li, Ni, Co, and Mn are all greater than 90%. In summary, the hydrogen-rich gas quality and yield prepared by the catalytic pyrolysis technology of waste ternary lithium battery separators proposed by the present invention, as well as the reduction of the hydrogen-rich gas on the cathode material, have achieved remarkable effects.

Claims

1. A method for catalytic pyrolysis of a waste ternary lithium battery separator to produce hydrogen and directionally reduce valuable metals, characterized in that, It includes a discharging unit, a disassembling, crushing and screening unit, a pyrolysis unit, a catalytic reforming unit, a medium-temperature reduction unit and a leaching unit, and comprises the following steps: The waste ternary lithium battery is discharged, disassembled, crushed and screened to obtain a shell, positive and negative electrode materials, current collectors, diaphragms and electrolytes; wherein, taking the diaphragm as the raw material, it reacts in a pyrolysis unit containing an inert atmosphere to release volatile components; taking a small part (<10%) of the positive electrode material as the catalyst, and introducing the volatile components into the catalytic reforming unit to react to obtain hydrogen-rich gas; introducing the hydrogen-rich gas into the medium-temperature reduction unit to reduce the high-valence metals such as nickel, cobalt and manganese in most (>80%) of the positive electrode materials; taking the solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder, and adding the reduced black powder into an acid solution without an external reducing agent to leach and recover valuable metals.

2. The method for catalytic pyrolysis of a waste ternary lithium battery separator to produce hydrogen and directionally reduce valuable metals according to claim 1, characterized in that, In the step that the waste ternary lithium battery is discharged, disassembled, crushed and screened to obtain a shell, positive and negative electrode materials, current collectors, diaphragms and electrolytes, the waste lithium battery is discharged by soaking in a 5 wt.% NaCl solution for 48 h, and after the discharged waste lithium battery is naturally air-dried, it is manually disassembled to obtain each component. The selected pure positive and negative electrode sheets are respectively crushed by a universal crusher, and the crushing time for each time is 5 s. After the positive and negative electrode wastes are crushed, they are screened through a 200-mesh sieve to remove the current collectors and obtain the positive and negative electrode materials.

3. A method for catalytic pyrolysis of waste ternary lithium battery separator to produce hydrogen and direct reduction of valuable metals, according to claim 1, characterized in that, The pyrolysis unit, the catalytic reforming unit and the medium-temperature reduction unit all use a protective gas, which can be one or several of nitrogen, helium, argon and xenon, and the flow rate of the protective gas is 50-100 mL / min.

4. A method for catalytic pyrolysis of a waste ternary lithium battery separator to produce hydrogen and directionally reduce valuable metals according to claim 3, characterized in that The pyrolysis unit, the catalytic reforming unit and the medium-temperature reduction unit are carried out in a three-stage furnace. The diaphragm pyrolysis is carried out in the first-stage furnace, the catalytic reforming of the water vapor of the pyrolysis volatile components with the positive electrode material as the catalyst is carried out in the second-stage furnace, and the medium-temperature reduction of the positive electrode material with the hydrogen-rich gas is carried out in the third-stage furnace.

5. A method for catalytic pyrolysis of a waste ternary lithium battery separator to produce hydrogen and directionally reduce valuable metals according to claim 1, characterized in that, In the step that taking the diaphragm as the raw material and reacting in a pyrolysis unit containing an inert atmosphere to release volatile components, the diaphragm pyrolysis temperature is 500-600 °C.

6. The method for catalytic pyrolysis of the diaphragm of waste ternary lithium batteries to produce hydrogen and directionally reduce valuable metals according to claim 1, characterized in that, In the step that taking a small part (<10%) of the positive electrode material as the catalyst and introducing the volatile components into the catalytic reforming unit to react to obtain hydrogen-rich gas, the mass ratio of the catalyst to the diaphragm is 0.25-2:1, the water vapor flow rate is 0-8 mL / h, the catalytic reforming temperature is 600-800 °C, and the reaction is carried out at a constant temperature for 1 h to obtain hydrogen-rich reducing gas.

7. A method for catalytic pyrolysis of waste lithium battery separators to produce hydrogen and directionally reduce valuable metals according to claim 1, characterized in that, In the step that introducing the hydrogen-rich gas into the medium-temperature reduction unit to reduce the high-valence metals such as nickel, cobalt and manganese in most (>80%) of the positive electrode materials, the reduction temperature is 500-800 °C, and the mass ratio of the positive electrode material to the diaphragm is 1-10:

1.

8. A method for catalytic pyrolysis of waste lithium battery separators to produce hydrogen and directionally reduce valuable metals according to claim 1, characterized in that, In the step of using the solid particles collected from the catalytic reforming unit and the medium-temperature reduction unit as reduced black powder and adding the reduced black powder into an acid solution without an external reducing agent for leaching to recover valuable metals, sulfuric acid solution is used for acid leaching the reduced black powder to recover valuable metals. The sulfuric acid concentration is 4 mol / L, the leaching time is 30 min, the temperature of water bath heating is 80 °C, the stirring speed is 150 r / min, the reduced black powder is mixed with the sulfuric acid solution, and the mixing ratio is 0.1 g / L.

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