Method and use of spent battery separator conversion to high value carbon materials

Abstract

The application belongs to the technical field of solid waste comprehensive utilization, and particularly relates to a method for converting waste battery diaphragm into high-value carbon material and use. The method for converting waste battery diaphragm into high-value carbon material comprises: (1) mixing waste battery diaphragm and urea, and pyrolyzing to obtain pyrolysis carbon; (2) modifying the pyrolysis carbon by alkali liquor to obtain high-value carbon material; wherein in step (1), the pyrolysis is stage heating pyrolysis, and the stage heating comprises: first heating to 200-300 DEG C, and keeping warm; then heating to 350-400 DEG C, and keeping warm; and then heating to 500-800 DEG C, and keeping warm. In the application, urea can react with the battery diaphragm in the carbonization process to form nitrogen-doped carbon material, and after subsequent treatment, N, O-doped carbon material is formed. This doping not only helps to improve the pore structure of the carbon material, but also increases the surface active sites, thereby significantly enhancing the adsorption capacity of the carbon material to industrial pollutants (such as methylene blue and / or microplastics).

Description

Technical Field

[0001] This invention belongs to the field of solid waste comprehensive utilization technology, specifically relating to the method and application of converting waste battery separators into high-value carbon materials. Background Technology

[0002] With the rapid development of the global new energy vehicle and energy storage industries, battery products such as lithium batteries have experienced explosive growth. The resulting battery waste has become a dual challenge of environmental pollution and resource waste. Currently, battery recycling technologies mainly focus on the recycling and regeneration of electrode active materials (such as metals like cobalt and lithium) and electrolytes. However, plastic separators (mainly polyethylene and polypropylene), which account for approximately 15%-25% of battery mass, have long faced the dilemma of "difficult recycling, expensive processing, and low resource utilization rate" due to their chemical stability and recalcitrant degradation characteristics. Statistics show that over one million tons of waste battery separators are generated globally each year. If traditional disposal methods such as landfill or incineration are used, they can easily lead to environmental risks such as microplastic pollution and the release of toxic gases. Therefore, developing high-value utilization technologies for separator waste has become a bottleneck that the industry urgently needs to overcome.

[0003] Current research on the recycling of waste battery separators is still in the laboratory exploration stage. Mainstream technical approaches include mechanical crushing followed by mixing with electrode materials for regeneration, and co-pyrolysis with electrolyte to prepare composite carbon materials. However, these methods have significant drawbacks: the mixing process easily introduces metallic impurities, leading to performance degradation of the recycled materials; and co-pyrolysis technology is limited by the difficulty in controlling electrolyte residues, making continuous production difficult. Furthermore, existing research largely focuses on preparing low-value-added carbon-based fuels or fillers, which have limited economic and environmental benefits.

[0004] It is worth noting that the membrane material itself has excellent properties such as high carbon-to-hydrogen ratio (C / H>6) and low ash content (<0.5%), and can theoretically be used as an ideal precursor for preparing high specific surface area functional carbon materials. However, the existing technology has not yet broken through the key process of its directional conversion into adsorbent carbon materials. Summary of the Invention

[0005] This invention develops a method for converting waste battery separators into high-value carbon materials. This method can convert waste battery separators into high-value carbon materials, which have excellent adsorption rates for pollutants (such as methylene blue and / or microplastics) in water.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0007] The present invention provides a method for converting waste battery separators into high-value carbon materials, comprising: (1) mixing waste battery separators and urea, and pyrolyzing them to obtain pyrolytic carbon; (2) modifying the pyrolytic carbon with an alkaline solution to obtain high-value carbon materials; wherein, in step (1), the pyrolysis is a staged heating pyrolysis, the staged heating includes: first heating to 200℃~300℃ and holding at that temperature; then heating to 350℃~400℃ and holding at that temperature; then heating to 500℃~800℃ and holding at that temperature.

[0008] Preferably, in the above method, the staged heating includes one or more of the following conditions:

[0009] (i) The heating rate of the stage is 2℃ / min to 6℃ / min;

[0010] (ii) The holding time for the 200℃~300℃ stage is 0.5h~1.5h;

[0011] (iii) The holding time for the 350℃~400℃ stage is 0.1h~1h;

[0012] (iv) The heat preservation time for the 500℃~800℃ stage is 1h~2h.

[0013] More preferably, in the above method, the staged heating includes: first heating to 240°C and holding for 1 hour; then heating to 380°C and holding for 0.5 hours; then heating to 600°C to 800°C and holding for 1 to 2 hours.

[0014] Preferably, in the above method, the mass ratio of waste battery separator to urea is 1:(0.1-8).

[0015] More preferably, in the above method, the mass ratio of waste battery separator to urea is 1:(0.5-6).

[0016] Preferably, in the above method, the alkaline solution is selected from one or more of potassium hydroxide, sodium hydroxide, or cesium hydroxide.

[0017] More preferably, in the above method, the concentration of the alkali solution is 0.1M to 5M.

[0018] Preferably, in the above method, the waste battery separator is one or more combinations of single-layer PP, single-layer PE, double-sided PP / PE, or triple-layer PP / PE / PP.

[0019] Another aspect of the present invention provides a high-value carbon material prepared by the method of the present invention.

[0020] Another aspect of the present invention provides the use of the high-value carbon material of the present invention in the adsorption of methylene blue and / or microplastics in water.

[0021] The beneficial effects of this invention include:

[0022] (1) In the method for converting waste battery separators into high-value carbon materials provided by the present invention, urea, as a cheap and environmentally friendly nitrogen source, can react with the battery separator during the carbonization process to form nitrogen-doped carbon materials. After subsequent processing, N and O-doped carbon materials are formed. This doping not only helps to improve the pore structure of carbon materials, but also increases their surface active sites, thereby significantly enhancing their adsorption capacity for industrial pollutants (such as methylene blue and / or microplastics).

[0023] (2) The method for converting waste battery separators into high-value carbon materials provided by the present invention is simple and easy to implement. It does not require a catalyst or additional costs to achieve the clean disposal of waste battery separators. Furthermore, it minimizes the use of chemicals, has high stability, causes little environmental pollution, and has broad development prospects. Detailed Implementation

[0024] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0026] This invention provides a method for converting waste battery separators into high-value carbon materials, comprising: (1) mixing waste battery separators and urea, and pyrolyzing them to obtain pyrolytic carbon; (2) modifying the pyrolytic carbon with an alkaline solution to obtain high-value carbon materials; wherein, in step (1), the pyrolysis is a staged heating pyrolysis, the staged heating includes: first heating to 200℃~300℃ and holding; then heating to 350℃~400℃ and holding; then heating to 500℃~800℃ and holding.

[0027] It should be noted that this invention uses a urea-assisted pyrolysis process with gradient heating and heat preservation to mix waste battery separators and urea, then pyrolyze and carbonize them at high temperature, and finally modify them with alkaline solution to obtain carbon materials with high N and O content (high-value carbon materials), thus realizing the resource utilization of battery separator waste.

[0028] In some specific examples, the staged heating in the above method includes one or more of the following conditions:

[0029] (i) The heating rate of the stage is 2℃ / min to 6℃ / min, for example, 3℃ / min, 4℃ / min or 5℃ / min, etc.;

[0030] (ii) The holding time for the 200℃~300℃ stage is 0.5h~1.5h. For example, the temperature can be 230℃, 250℃ or 280℃, and the time can be 0.8h, 1h or 1.2h, etc.

[0031] (iii) The holding time for the 350℃~400℃ stage is 0.1h~1h. For example, the temperature can be 360℃, 370℃, 380℃ or 390℃, etc., and the time can be 0.3h, 0.5h or 0.8h, etc.

[0032] (iv) The holding time for the 500℃~800℃ stage is 1h~2h. For example, the temperature can be 550℃, 600℃, 650℃, 700℃ or 750℃, and the time can be 1.3h, 1.5h or 1.8h, etc.

[0033] In some specific examples, the above method includes the following stages of heating: first heating to 240℃ and holding for 1 hour; then heating to 380℃ and holding for 0.5 hours; then heating to 600℃~800℃ and holding for 1 hour~2 hours.

[0034] In some specific examples, the mass ratio of waste battery separator to urea in the above method is 1:(0.1-8), such as 1:(0.5-6), 1:(1-5), or 1:(2-4), etc.

[0035] In some specific examples, the alkaline solution in the above method is selected from one or more of potassium hydroxide, sodium hydroxide, or cesium hydroxide.

[0036] In some specific examples, the concentration of the alkali solution in the above method is 0.1M to 5M, such as 1M, 2M, 3M or 4M.

[0037] In some specific examples, the waste battery separator in the above method is one or more combinations of single-layer PP, single-layer PE, double-sided PP / PE, or triple-layer PP / PE / PP.

[0038] This invention also provides a high-value carbon material prepared by the method of this invention.

[0039] This invention also provides an example of the use of the high-value carbon material in the adsorption of methylene blue and / or microplastics in water.

[0040] It should be noted that the high-value carbon material in this invention has increased lyophilicity in aqueous solution due to its high N and O content. This is because the C=N and C=O functional groups may interact with dye molecules through hydrogen bonding and π-π stacking, while the CN and CON functional groups may interact through hydrogen bonding, making it easier for industrial dyes such as methylene blue and microplastics to be adsorbed onto the carbon material.

[0041] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0042] In the following example, the shredded waste membrane was sourced from Changzhou Houde Renewable Resources Technology Co., Ltd.

[0043] I. Preparation of high-value carbon materials from waste membranes

[0044] Example 1

[0045] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:0.5. After mixing, the temperature was increased to 240℃ at a heating rate of 10℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 10℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 10℃ / min and pyrolyzed at 600℃ for 2h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0046] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 20.12% and the O content is 3.32%, which is recorded as 0.5-NO-600.

[0047] Example 2

[0048] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:1. After mixing, the temperature was increased to 240℃ at a heating rate of 10℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 5℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 2h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0049] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 22.36% and the O content is 3.76%, which is recorded as 1-NO-600.

[0050] Example 3

[0051] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:2. After mixing, the temperature was increased to 240℃ at a heating rate of 10℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 3℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 3℃ / min and pyrolyzed at 600℃ for 1h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0052] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 24.18% and the O content is 4.35%, which is recorded as 2-NO-600.

[0053] Example 4

[0054] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was increased to 240℃ at a heating rate of 5℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 5℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 1h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0055] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 39.52% and the O content is 4.39%, which is recorded as 4-NO-600.

[0056] Example 5

[0057] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:6. After mixing, the temperature was increased to 240℃ at a heating rate of 5℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 5℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 2h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0058] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 40.01% and the O content is 4.56%, which is recorded as 6-NO-600.

[0059] Example 6

[0060] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was increased to 240℃ at a heating rate of 5℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 5℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 700℃ at a heating rate of 5℃ / min and pyrolyzed at 700℃ for 2h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0061] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 36.14% and the O content is 4.03%, which is recorded as 4-NO-700.

[0062] Example 7

[0063] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was increased to 240℃ at a heating rate of 5℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 5℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 800℃ at a heating rate of 5℃ / min and pyrolyzed at 800℃ for 2h. Nitrogen gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0064] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an oven at 110℃ and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 33.28% and the O content is 3.56%, which is recorded as 4-NO-800.

[0065] Example 8

[0066] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was increased to 240℃ at a heating rate of 5℃ / min and held at 240℃ for 1h. After the holding period, the temperature was increased to 380℃ at a heating rate of 3℃ / min and held at 380℃ for 0.5h. After the holding period, the temperature was increased to 600℃ at a heating rate of 3℃ / min and pyrolyzed at 600℃ for 1h. Argon gas was introduced simultaneously during all heating processes. After the pyrolysis was completed, the mixture was cooled to room temperature under an argon atmosphere to obtain pyrolytic carbon.

[0067] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 38.56% and the O content is 4.23%, which is denoted as 4R-NO-600.

[0068] Comparative Example 1

[0069] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:0.5. After mixing, the temperature was raised to 600℃ at a heating rate of 10℃ / min and pyrolyzed at 600℃ for 2 hours. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0070] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 5.03% and the O content is 2.21%, which is denoted as D-0.5-NO-600.

[0071] Comparative Example 2

[0072] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:1. After mixing, the temperature was raised to 600℃ at a heating rate of 10℃ / min and pyrolyzed at 600℃ for 2 hours. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0073] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 5.32% and the O content is 2.86%, which is denoted as D-1-NO-600.

[0074] Comparative Example 3

[0075] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:2. After mixing, the temperature was raised to 600℃ at a heating rate of 10℃ / min and pyrolyzed at 600℃ for 1h. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0076] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 5.87% and the O content is 2.89%, which is denoted as D-2-NO-600.

[0077] Comparative Example 4

[0078] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was raised to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 1h. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolytic carbon.

[0079] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 9.43% and the O content is 3.14%, which is denoted as D-4-NO-600.

[0080] Comparative Example 5

[0081] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:6. After mixing, the temperature was raised to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 2 hours. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0082] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 1h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an 80℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 9.61% and the O content is 3.21%, which is denoted as D-6-NO-600.

[0083] Comparative Example 6

[0084] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was raised to 700℃ at a heating rate of 5℃ / min and pyrolyzed at 700℃ for 2 hours. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0085] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 8.40% and the O content is 2.98%, which is denoted as D-4-NO-700.

[0086] Comparative Example 7

[0087] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was raised to 800℃ at a heating rate of 5℃ / min and pyrolyzed at 800℃ for 2 hours. Nitrogen gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0088] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in an oven at 110℃ and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 7.73% and the O content is 2.93%, which is denoted as D-4-NO-800.

[0089] Comparative Example 8

[0090] (1) The crushed waste membrane and urea were thoroughly mixed at a mass ratio of 1:4. After mixing, the temperature was increased to 600℃ at a heating rate of 5℃ / min and pyrolyzed at 600℃ for 1h. Argon gas was introduced at the same time during all heating processes. After pyrolysis, the mixture was cooled to room temperature under a nitrogen atmosphere to obtain pyrolyzed carbon.

[0091] (2) Add 0.5g of pyrolytic carbon to 20ml of potassium hydroxide solution (1M) and stir for 0.5h to make it evenly mixed. After standing for 24h, wash with deionized water until the supernatant is neutral and filter to obtain precipitate. Then place the precipitate in a 100℃ oven and dry for 6h to obtain high-value carbon material. The N content of the high-value carbon material is 8.57% and the O content is 2.96%, which is denoted as D-4R-NO-600.

[0092] II. Characterization of High-Value Carbon Materials

[0093] The high-value carbon materials prepared in Examples 1 to 8 and Comparative Examples 1 to 8 were tested using BET method to obtain their specific surface area (S). BET The pore volume was tested by N2 adsorption-desorption experiment, and the elemental content of the carbon material was verified by X-ray photoelectron spectroscopy analysis. The results are shown in Table 1.

[0094] Table 1. BET specific surface area, pore volume, and elemental content of carbon materials.

[0095]

[0096] The data from Examples 1-8 and Comparative Examples 1-8 show that holding the carbon material at 240℃ and 380℃ introduces more nitrogen (N) elements, increasing defects and thus introducing more oxygen (O) elements. Simultaneously, the introduction of N and O elements increases defects, leading to a decrease in the specific surface area and volume response of the carbon material. With increasing pyrolysis temperature and time, the crystal structure of the carbon material gradually becomes more ordered. This is because high temperatures promote the removal of non-carbon elements (such as oxygen and nitrogen), reducing the content of heteroatoms. During this process, carbon atoms recombine and form more stable graphitized or quasi-graphite structures, resulting in increased lattice order.

[0097] III. Application of High-Value Carbon Materials

[0098] (I) Methylene Blue Adsorption Test in Water

[0099] A 100 mg / L solution of methylene blue was prepared. 5 mg of each of the high-value carbon materials prepared in Examples 1 to 8 (0.5-NO-600, 0.5-NO-600, 2-NO-600, 4-NO-600, 6-NO-600, 4-NO-700, 4-NO-800, and 4R-NO-600) were placed in 20 ml of the methylene blue solution and subjected to shaking at room temperature and pressure on a water bath (25°C) at 160 rpm. Adsorption experiments were conducted with an adsorption time of 6 hours. The removal rate of methylene blue in water was tested (methylene blue was prepared into a 100 mg / L aqueous solution using deionized water, and then diluted with deionized water to prepare standard solutions of 1 mg / L, 2 mg / L, 4 mg / L, 8 mg / L, and 10 mg / L, respectively. The standard solutions were measured using a UV spectrophotometer at a wavelength of 664 nm to obtain a standard curve. The removal rate was obtained by measuring the absorbance of the solution after adsorption). The results are shown in Table 2 below.

[0100] Table 2 Removal rates of methylene blue from water by different high-value carbon materials

[0101] Example Carbon material Methylene blue removal rate (%) Example 1 0.5-N-O-600 78.5 Example 2 0.5-N-O-600 73.6 Example 3 2-N-O-600 71.2 Example 4 4-N-O-600 91.2 Example 5 6-N-O-600 91.8 Example 6 4-N-O-700 88.3 Example 7 4-N-O-800 85.6 Example 8 4R-N-O-600 82.1 Comparative Example 1 D-0.5-N-O-600 56.7 Comparative Example 2 D-1-N-O-600 65.3 Comparative Example 3 D-2-N-O-600 62.2 Comparative Example 4 D-4-N-O-600 78.3 Comparative Example 5 D-6-N-O-600 78.8 Comparative Example 6 D-4-N-O-700 78.6 Comparative Example 7 D-4-N-O-800 76.3 Comparative Example 8 D-4R-N-O-600 76.6

[0102] (II) Microplastic Adsorption Test in Water

[0103] Polystyrene microplastics with a diameter of 1-6 μm were prepared into a 100 mg / L solution. 5 mg of the high-value carbon materials prepared in Examples 1 to 8 (0.5-NO-600, 0.5-NO-600, 2-NO-600, 4-NO-600, 6-NO-600, 4-NO-700, 4-NO-800, and 4R-NO-600) were placed in 20 ml of the microplastic solution, respectively. Adsorption experiments were conducted at room temperature and pressure under the conditions of a water bath (25℃) and a shaking incubator at 160 r / min for 6 h. The removal rate of microplastics in water was tested (by centrifugation in a saturated salt solution (NaCl) to allow the microplastics to float on the surface, washing and drying them, and weighing them; the removal rate was calculated based on the mass ratio before and after adsorption). The results are shown in Table 3 below.

[0104] Table 3. Removal rate of microplastics in water by high-value carbon materials.

[0105] Example Carbon material Microplastic removal rate (%) Example 1 0.5-N-O-600 79.6 Example 2 0.5-N-O-600 75.2 Example 3 2-N-O-600 72.8 Example 4 4-N-O-600 93.4 Example 5 6-N-O-600 95.7 Example 6 4-N-O-700 92.1 Example 7 4-N-O-800 87.8 Example 8 4R-N-O-600 86.1 Comparative Example 1 D-0.5-N-O-600 69.3 Comparative Example 2 D-1-N-O-600 68.2 Comparative Example 3 D-2-N-O-600 66.2 Comparative Example 4 D-4-N-O-600 79.3 Comparative Example 5 D-6-N-O-600 78.2 Comparative Example 6 D-4-N-O-700 77.2 Comparative Example 7 D-4-N-O-800 74.1 Comparative Example 8 D-4R-N-O-600 76.5

[0106] As can be seen from Tables 2 and 3 above, high-value carbon materials doped with N and O have increased lyophilicity in aqueous solutions due to their higher N and O content. This is because C=N and C=O functional groups may interact with dye molecules through hydrogen bonding and π-π stacking, while CN and CON functional groups may interact through hydrogen bonding, making it easier for industrial dyes such as methylene blue and microplastics to be adsorbed onto carbon materials.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for converting spent battery separators into high value carbon materials, characterized by, Comprising: (1) mixing the waste battery separator and urea, and pyrolyzing to obtain pyrolytic carbon; (2) modifying the pyrolytic carbon by alkali solution to obtain high-value carbon material; In step (1), the pyrolysis is staged temperature pyrolysis, and the staged temperature rising includes: first rising to 200-300℃, holding; then rising to 350-400℃, holding; then rising to 500-800℃, holding.

2. The method of claim 1, wherein, The staged temperature rising includes one or more of the following conditions: (i) the temperature rising rate of the staged temperature rising is 2-6℃ / min; (ii) the holding time at 200-300℃ is 0.5-1.5h; (iii) the holding time at 350-400℃ is 0.1-1h; (iv) the holding time at 500-800℃ is 1-2h.

3. The method of claim 2, wherein, The staged temperature rising includes: first rising to 240℃, holding for 1h; then rising to 380℃, holding for 0.5h; then rising to 600-800℃, holding for 1-2h.

4. The method according to any one of claims 1 to 3, characterized in that, The mass ratio of the waste battery separator and urea is 1:(0.1-8).

5. The method of claim 4, wherein, The mass ratio of the waste battery separator and urea is 1:(0.5-6).

6. The method of claim 1, 2, 3, or 5, wherein, The alkali solution is selected from one or more of potassium hydroxide, sodium hydroxide or cesium hydroxide.

7. The method of claim 6, wherein, The concentration of the alkali solution is 0.1-5M.

8. The method of claim 1, 2, 3, 5, or 7, wherein, The waste battery separator is one or more of single-layer PP, single-layer PE, double-sided PP / PE or three-layer PP / PE / PP.

9. The high-value carbon material prepared by the method of any one of claims 1-8.

10. The use of the high-value carbon material of claim 9 in adsorbing methylene blue and / or microplastics in water bodies.

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