A method for preparing pre-lithiated graphene from recycled carbon-based negative electrode materials

Abstract

The embodiment of the present application relates to a method for preparing pre-lithiated graphene by recycling carbon-based negative electrode materials. The method comprises: soaking disassembled carbon-based negative electrode sheets in water, then using an ultrasonic device to perform ultrasonic oscillation, so that the negative electrode material and the negative electrode current collector are peeled off, and after filtration, a negative electrode carbon material slurry is obtained; the negative electrode carbon slurry is dried and then low-temperature calcined below 400 DEG C, so that a sintered negative electrode carbon material is obtained; the sintered negative electrode carbon material is added to dilute nitric acid with a concentration of 6 mol / L or less, stirred and then allowed to stand, so that an acidic solution containing Li + and other metal impurity ions is obtained; cation exchange resin is added to the acidic solution, stirred, and other metal impurity ions are adsorbed by the cation exchange resin, so that an acidic slurry containing Li + and the purified negative electrode carbon material is obtained after filtration; and the acidic slurry is used as a substrate to prepare pre-lithiated graphene by using the Hummers redox method.

Description

Technical Field

[0001] This invention relates to the field of battery anode material recycling technology, and in particular to a method for preparing pre-lithiated graphene by recycling carbon-based anode materials. Background Technology

[0002] In recent years, the new energy industry has entered a stage of rapid development. According to data released by the Ministry of Industry and Information Technology, the national lithium-ion battery production reached 750 GWh in 2022. Although there have been several changes to battery systems to ensure the high energy density and long lifespan required by the new energy industry, the actual battery life is still mainly 3-5 years due to the particle cracking characteristics of the current main graphite-based anode materials after long cycles. Statistics show that the actual recycling volume of waste lithium-ion batteries in my country reached 415,000 tons, an increase of 75.8% year-on-year, mainly consisting of ternary and lithium cobalt oxide batteries.

[0003] Graphene, as a nanomaterial with stable crystallinity, excellent optical properties, and superb electrical conductivity, has a wide range of applications. Among the methods for preparing graphene, the Hummers redox method is the most common and suitable for mass production, and the product performance is relatively stable.

[0004] Pre-lithiated graphene electrode materials are typically prepared from raw graphene materials through chemical synthesis or lithiation technology combined with mechanical exfoliation.

[0005] However, with increasing awareness of sustainable development and environmental protection, researchers have been seeking new ways to promote the green production of graphene batteries. Recycling waste lithium-ion battery materials and reusing them in battery manufacturing is a promising and meaningful research direction. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing pre-lithiated graphene by recycling carbon-based anode materials. By recycling and removing impurities from the carbon-based anode sheet, the lithium element naturally present in the recycled anode material can be used to achieve graphene pre-lithiation, realizing resource recycling. The method proposed in this invention is green, environmentally friendly, and easy to implement.

[0007] Therefore, embodiments of the present invention provide a method for preparing pre-lithiated graphene by recycling carbon-based anode materials, the method comprising:

[0008] The disassembled carbon-based negative electrode sheet is immersed in water, and then ultrasonic vibration is performed using an ultrasonic device to separate the negative electrode material from the negative electrode current collector. After filtration, a negative electrode carbon material slurry is obtained.

[0009] The negative electrode carbon slurry is dried and then calcined at a low temperature below 400°C to obtain the sintered negative electrode carbon material.

[0010] The sintered negative electrode carbon material was added to dilute nitric acid with a concentration of less than 6 mol / L, stirred, and allowed to stand to obtain a solution containing Li. + Acidic solutions containing other metal impurity ions;

[0011] A cation exchange resin is added to the acidic solution, and the mixture is stirred. Other metal impurity ions are adsorbed by the cation exchange resin, and the solution is filtered to obtain a solution containing Li. + And the acidic slurry of purified negative electrode carbon material;

[0012] Pre-lithiated graphene was prepared using the acidic slurry as a substrate via the Hummers redox method.

[0013] Preferably, the low-temperature calcination temperature is 300-400℃, the holding time is 2-4h, and air is introduced during the calcination process at a gas flow rate of 0.5-1L / min.

[0014] Preferably, the soaking time is 2-4 hours, the ultrasonic duration is 0.5-1.5 hours, and the intensity is 30-50 kHz.

[0015] Preferably, in the preparation of the acidic solution, the concentration of the dilute nitric acid is 3 mol / L, the stirring speed is 100-150 r / min, the stirring time is 2-4 h, and the standing time is 2-4 h; the molar ratio of the added dilute nitric acid to the metal impurities contained in the recovered negative electrode carbon material is 2:1-3:1.

[0016] Preferably, the cation exchange resin is a strongly acidic cation exchange resin, wherein the strongly acidic cation exchange resin is a cation exchange resin whose main exchange group is a sulfonic acid group (-SO3H).

[0017] The molar ratio of the acidic functional group used to replace metal ions in the cation exchange resin to the metal impurity ions other than lithium in the negative electrode carbon material is 1:1 to 2:1.

[0018] Preferably, in the preparation of the acidic slurry, the stirring speed is 100-150 r / min and the stirring time is 2-4 h; the filtration is carried out using a PE material filter screen with a mesh size of 100 mesh.

[0019] Preferably, the method further includes: soaking and rinsing the cation exchange resin after adsorbing other metal impurity ions in dilute nitric acid.

[0020] More preferably, the concentration of the dilute nitric acid is between 0.5 mol / L and 1 mol / L.

[0021] The method for preparing pre-lithiated graphene provided in this invention involves low-temperature calcination in air to oxidize the surface of carbon-based material particles, thereby forming pores. This facilitates the peeling of graphite sheets and allows components such as binders and electrolytes attached to the surface of the carbon-based material to volatilize, making it easier to remove metal impurities. The use of cation exchange resin effectively removes metal impurities from the recovered negative electrode material, and the purified cation exchange resin can be regenerated after rinsing with dilute nitric acid. The lithium element naturally present in the recovered negative electrode material can be used for pre-lithiation. During the redox process, lithium ions more readily combine with the oxygen-containing functional groups of graphene oxide, thus achieving pre-lithiation. Therefore, the Hummers redox method is used to directly prepare pre-lithiated graphene. This method is green, environmentally friendly, and low-cost, reducing the risk of introducing metal impurities from external sources in the traditional preparation of pre-lithiated graphene. Attached Figure Description

[0022] Figure 1 A flowchart illustrating the method for preparing pre-lithiated graphene from recycled carbon-based anode materials provided in this embodiment of the invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] This invention provides a method for preparing pre-lithiated graphene by recycling carbon-based anode materials, the main steps of which are as follows: Figure 1 As shown, it includes:

[0025] Step 110: Immerse the disassembled carbon-based negative electrode sheet in water, and then use an ultrasonic device to perform ultrasonic vibration to separate the negative electrode material from the negative electrode current collector. After filtration, a negative electrode carbon material slurry is obtained.

[0026] The soaking time is 2-4 hours, the ultrasonic duration is 0.5-1.5 hours, and the intensity is 30-50 kHz.

[0027] The lithium element in the negative electrode carbon material refers to the lithium element embedded in the negative electrode to be recycled. Under normal circumstances, the mass fraction of lithium element in the negative electrode carbon material is 0.5%-1.5%. In addition to lithium ions, the negative electrode carbon material may also contain some other metal impurity ions.

[0028] Step 120: After drying the negative electrode carbon slurry, it is calcined at a low temperature below 400℃ to obtain the sintered negative electrode carbon material.

[0029] The low-temperature calcination temperature is 300-400℃, the holding time is 2-4h, and air is introduced during the calcination process at a flow rate of 0.5-1L / min.

[0030] Step 130: Add the sintered negative electrode carbon material to dilute nitric acid with a concentration of less than 6 mol / L, stir, and let stand to obtain Li. + Acidic solutions containing other metal impurity ions;

[0031] The preferred concentration of dilute nitric acid is 3 mol / L, the stirring speed is 100-150 r / min, the stirring time is 2-4 h, and the settling time is 2-4 h; the molar ratio of the added dilute nitric acid to the metal impurities contained in the recovered negative electrode carbon material is 2:1-3:1.

[0032] Step 140: Add cation exchange resin to the acidic solution, stir, and allow other metal impurity ions to be adsorbed by the cation exchange resin. After filtration, obtain the solution containing Li. + And the acidic slurry of purified negative electrode carbon material;

[0033] Preferably, the cation exchange resin is a strongly acidic cation exchange resin, and the strongly acidic cation exchange resin is a cation exchange resin whose main exchange group is a sulfonic acid group (-SO3H).

[0034] The total exchange capacity of a cation exchange resin is the molar ratio of the acidic functional groups in the cation exchange resin used to replace metal ions in the exchange reaction to the other metal impurity ions in the negative electrode carbon material, which is 1:1 to 2:1.

[0035] In the preparation of acidic slurry, the stirring speed is 100-150 r / min and the stirring time is 2-4 h; the filtration is carried out using a polyethylene (PE) filter screen with a mesh size of 100 mesh.

[0036] After this step, the cation exchange resin that has adsorbed other metal impurity ions can be soaked and rinsed in dilute nitric acid, wherein the concentration of dilute nitric acid is between 0.5 mol / L and 1 mol / L, in order to recycle the cation exchange resin.

[0037] Step 150: Using acidic slurry as a substrate, pre-lithiated graphene is prepared by the Hummers redox method.

[0038] The Hummers redox method is a conventional existing method and will not be described in detail here. This invention utilizes this method to prepare pre-lithiated graphene. It mainly involves mixing an acidic slurry with concentrated sulfuric acid, adding a strong oxidant, and stirring. During this process, oxidation occurs, generating pre-lithiated graphene oxide. During oxidation, factors such as the concentration of sulfuric acid, the amount of strong oxidant added, reaction time, and temperature can be adjusted to control the oxygen content of the generated graphene oxide. Finally, the oxidized product undergoes multiple washings and filtrations to remove unreacted acid and residual oxides.

[0039] The method for preparing pre-lithiated graphene provided in this invention involves low-temperature calcination in air to oxidize the surface of carbon-based material particles, thereby forming pores. This facilitates the peeling of graphite sheets and allows components such as binders and electrolytes attached to the surface of the carbon-based material to volatilize, making it easier to remove metal impurities. The use of cation exchange resin effectively removes metal impurities from the recovered negative electrode material, and the purified cation exchange resin can be regenerated after rinsing with dilute nitric acid. The lithium element naturally present in the recovered negative electrode material can be used for pre-lithiation. During the redox process, lithium ions more readily combine with the oxygen-containing functional groups of graphene oxide, thus achieving pre-lithiation. Therefore, the Hummers redox method is used to directly prepare pre-lithiated graphene. This method is green, environmentally friendly, and low-cost, reducing the risk of introducing metal impurities from external sources in the traditional preparation of pre-lithiated graphene.

[0040] To more clearly illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with embodiments. In addition, the embodiments described in the present invention are only some embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0041] Example 1

[0042] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 300℃ for 2 hours with an air flow rate of 0.5 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0043] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 2 h, the molar ratio of the added nitric acid to the metal impurities contained in the calcined negative electrode carbon material is 2:1, and let stand for 2 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0044] 3) Add a strongly acidic cation exchange resin containing sulfonic acid groups (-SO3H) to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 1:1. Stir to ensure complete reaction at a stirring speed of 120 r / min for 2 h. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. +And acidic slurry of purified negative electrode carbon material.

[0045] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0046] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0047] Testing of pre-lithiated graphene materials:

[0048] Preparation of negative electrode material: Low graphitization material with a capacity of 330 mAh / g and an efficiency of 80% in the first week was mixed with the prepared pre-lithiated graphene at a mass ratio of 1:1.

[0049] This test was conducted using a CR2032 coin cell, which mainly involved the following materials: lithium sheet, electrolyte (1 mol / L lithium hexafluorophosphate @ ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and fluoroethylene carbonate in a volume ratio of 1:1:1:1), polyethylene (PE) base film, and the negative electrode material prepared in this invention. The coin cell test procedure was 0.1C discharge to 5mV, 0.02C discharge to 5mV, and 0.1C charge to 2V.

[0050] Example 2

[0051] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 350℃ for 2 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0052] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 3 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 2:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0053] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 1:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 2 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0054] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0055] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0056] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0057] Example 3

[0058] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0059] 2) Add the calcined negative electrode carbon material to dilute nitric acid with a concentration of 3 mol / L, stir thoroughly at a stirring speed of 120 r / min for 4 h, the molar ratio of nitric acid to the metal impurities contained in the calcined negative electrode carbon material is 2:1, and let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0060] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 1:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 2 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0061] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0062] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0063] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0064] Example 4

[0065] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0066] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 4 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 3:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0067] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 1:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 2 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0068] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0069] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0070] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0071] Example 5

[0072] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0073] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 4 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 3:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0074] 3) Add the same strong acid cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strong acid cation exchange resin to the other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 2:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 3 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0075] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0076] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0077] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0078] Example 6

[0079] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 0.5% lithium by mass.

[0080] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 4 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 3:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0081] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 2:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 4 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0082] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0083] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0084] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0085] Example 7

[0086] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 1.0% lithium by mass.

[0087] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 4 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 3:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0088] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 2:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 4 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0089] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0090] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0091] The testing method for pre-lithiated graphene materials is the same as in Example 1.

[0092] Example 8

[0093] 1) The disassembled lithium battery negative electrode material sheets were soaked in water for 2 hours and then vibrated using an ultrasonic device for 1 hour at an intensity of 40 kHz. After filtration, the resulting negative electrode carbon material slurry was dried. After drying, the moisture content was tested using the weight loss method and found to be ≤0.1%. The dried negative electrode carbon material was then subjected to low-temperature calcination at 400℃ for 4 hours with an air flow rate of 1.0 L / min. The resulting calcined negative electrode carbon material contained 1.5% lithium by mass.

[0094] 2) Add the calcined negative electrode carbon material to a 3 mol / L dilute nitric acid solution, stir thoroughly at a stirring speed of 120 r / min for 4 h, and add nitric acid to the metal impurities contained in the calcined negative electrode carbon material at a molar ratio of 3:1. Let stand for 4 h to obtain an acidic solution for recovering the negative electrode carbon material.

[0095] 3) Add the same strongly acidic cation exchange resin as in Example 1 to the acidic solution of the recovered negative electrode carbon material. The molar ratio of the total exchange capacity of the added strongly acidic cation exchange resin to the molar ratio of other metal impurities (excluding lithium) in the recovered negative electrode carbon material is 2:1. Stir to allow the reaction to proceed fully at a stirring speed of 120 r / min for 4 hours. Filter the solution using a PE filter with a mesh size of 100 mesh to obtain a solution containing Li. + And acidic slurry of purified negative electrode carbon material.

[0096] 4) Containing Li + Using a purified anode carbon material acidic slurry as a substrate, pre-lithium graphene was prepared by the Hummer redox method, as detailed below:

[0097] Equimolar amounts of concentrated sulfuric acid were slowly added to the acidic slurry while continuously stirring. The slurry temperature was controlled at 20-30℃. After stirring evenly, potassium permanganate solid with a molar mass ratio of 2.5:1 to concentrated sulfuric acid was slowly added. After stirring for 30 min, a 3% hydrogen peroxide solution with a molar mass ratio of 1:5 to potassium permanganate was added. After stirring for 30 min until no more bubbles were generated, the solution was heated to 80℃ using a water bath method. Hydrazine hydrate with a molar ratio of 1:400 to the recovered negative electrode carbon material was added. After stirring for 12 h, the solution was washed multiple times with methanol and water and then dried to obtain pre-lithium graphene.

[0098] The test results of the above embodiments are shown in Table 1 below.

[0099] Example 1 385.1 82.3 Example 2 387.6 82.5 Example 3 390.3 82.9 Example 4 391.5 84.2 Example 5 390.6 85.1 Example 6 391.7 86.3 Example 7 391.2 88.1 Example 8 390.9 91.2

[0100] Table 1

[0101] As can be seen, the pre-lithiated graphene prepared in the above embodiments of the present invention has the effects of high initial efficiency and high capacity as a negative electrode material for lithium-ion batteries.

[0102] The method for preparing pre-lithiated graphene by recycling carbon-based anode materials proposed in this invention has broad application prospects in lithium-ion battery material recycling and graphene material preparation.

[0103] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing pre-lithiated graphene by recycling carbon-based anode materials, characterized in that, The method includes: The disassembled carbon-based negative electrode sheet is immersed in water, and then ultrasonic vibration is performed using an ultrasonic device to separate the negative electrode material from the negative electrode current collector. After filtration, a negative electrode carbon material slurry is obtained. The negative electrode carbon material slurry is dried and then calcined at a low temperature below 400°C to obtain the sintered negative electrode carbon material. The sintered negative electrode carbon material was added to dilute nitric acid with a concentration of less than 6 mol / L, stirred, and allowed to stand to obtain a Li-containing material. + Acidic solutions containing other metal impurity ions; A cation exchange resin is added to the acidic solution, and the mixture is stirred. Other metal impurity ions are adsorbed by the cation exchange resin, and the solution is filtered to obtain a solution containing Li. + And the acidic slurry of purified negative electrode carbon material; Pre-lithiated graphene was prepared using the acidic slurry as a substrate via the Hummers redox method.

2. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, The soaking time is 2-4 hours, the ultrasonic duration is 0.5-1.5 hours, and the intensity is 30-50 kHz.

3. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, The low-temperature calcination temperature is 300-400℃, the holding time is 2-4h, and air is introduced during the calcination process at a gas flow rate of 0.5-1L / min.

4. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, In the preparation of the acidic solution, the concentration of the dilute nitric acid is 3 mol / L, the stirring speed is 100-150 r / min, the stirring time is 2-4 h, and the standing time is 2-4 h; the molar ratio of the added dilute nitric acid to the metal impurities contained in the recovered negative electrode carbon material is 2:1-3:

1.

5. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, The cation exchange resin is a strongly acidic cation exchange resin, wherein the strongly acidic cation exchange resin is a cation exchange resin whose main exchange group is a sulfonic acid group (-SO3H). The molar ratio of the acidic functional group used to replace metal ions in the cation exchange resin to the metal impurity ions other than lithium in the negative electrode carbon material is 1:1 to 2:

1.

6. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, In the preparation of the acidic slurry, the stirring speed is 100-150 r / min and the stirring time is 2-4 h; the filtration is carried out using a PE material filter screen with a mesh size of 100 mesh.

7. The method for preparing pre-lithiated graphene according to claim 1, characterized in that, The method further includes: soaking and rinsing the cation exchange resin after it has adsorbed other metal impurity ions in dilute nitric acid.

8. The method for preparing pre-lithiated graphene according to claim 7, characterized in that, The concentration of the dilute nitric acid is between 0.5 mol / L and 1 mol / L.

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