A method for preparing a graphene composite porous silicon-copper alloy negative electrode material by using waste lithium battery negative electrode powder as raw material

Abstract

The application relates to a method for preparing a graphene composite porous silicon-copper alloy negative electrode material by using waste lithium battery negative electrode powder as raw material, relates to a method for high-value utilization of waste lithium ion battery graphite negative electrode. The application aims to solve the technical problems that the waste lithium battery negative electrode graphite is treated as solid waste and the existing silicon-based negative electrode expands in volume. The waste lithium ion battery graphite negative electrode is prepared into a graphene composite porous silicon-copper alloy negative electrode material, resource recovery of the waste lithium ion battery graphite negative electrode is realized, and the production cost of the silicon-based negative electrode material is reduced, which is extremely significant for environmental protection and promotion of lithium ion battery negative electrode material update iteration. The application can realize high-value utilization of the waste lithium ion battery graphite negative electrode, and is of great significance for environmental protection and resource saving; the electrostatic adsorption packaging process is simple, and can be applied to industry on a large scale. The application provides a new idea and solution for solving the silicon-based volume expansion problem.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for high-value utilization of waste lithium ion battery graphite negative electrode. BACKGROUND

[0002] In recent years, with the depletion of fossil energy and the pressure of environmental protection, more and more new energy vehicles have been put into the market. New energy vehicles have developed rapidly in the past decade, such as the global new energy vehicle ownership reached 5 million in 2018, an increase of 63% compared with 2017. It is estimated that new energy vehicles will account for 11.28% of the total number of vehicles by 2040, which can be inferred that the demand for lithium ion batteries in the future automobile market will also increase sharply. Lithium ion batteries will have to face the problem of retirement after a certain period of use. If the retired lithium ion batteries are not properly disposed of, the heavy metals leached from the negative electrode material will continue to migrate with the atmosphere, water, and soil, or be converted into more toxic compounds, causing pollution of water bodies and soil. The decomposition and hydrolysis products of electrolyte solvents and binders will cause pollution of aldehydes, ketones, methanol and other organic substances. Heavy metals and organic substances entering the ecosystem are enriched in higher organisms through the food chain, causing great harm to the ecosystem and human health. Among the many negative materials of lithium batteries, graphite is considered an ideal negative material for lithium ion batteries due to its excellent rate capability and cycle stability. Its market share is increasing, and the amount of retired batteries is also increasing. The graphite negative electrode of the retired lithium ion battery is often not properly disposed of, and most of the copper foil left after the graphite is removed from the retired graphite negative electrode is recycled, while the graphite is treated as solid waste. In lithium ion batteries, the graphite negative electrode accounts for 25% to 35% of the total mass. If such a large amount of graphite negative electrode can be high-value utilized, it not only can make enterprises profitable, but also can protect the environment.

[0003] Silicon-based negative electrode (4200mAh / g) has a theoretical capacity far exceeding that of carbon-based negative electrode (372mAh / g), and is therefore considered as a negative material for the next generation of lithium ion batteries. However, due to the problem of volume expansion of silicon-based negative electrode during battery charging and discharging, it has not been widely popularized. At present, in order to solve the problem of volume expansion of silicon-based negative electrode, the common method is to use pitch and other carbon sources to coat the surface of silicon to alleviate the volume expansion, but this method has poor effect and high cost. SUMMARY

[0004] The present application is to solve the technical problems of the current waste lithium battery negative electrode graphite being treated as solid waste and the volume expansion of the existing silicon-based negative electrode, and to provide a method for preparing graphene composite porous silicon-copper alloy negative electrode material using waste lithium battery negative electrode powder as raw material.

[0005] The method for preparing graphene composite porous silicon-copper alloy negative electrode material using waste lithium battery negative electrode powder as raw material of the present application

[0006] is carried out according to the following steps:

[0007] I. Discharge the waste lithium ion battery to 3.2-3.7V through the battery charging and discharging system;

[0008] II. Disassemble the waste lithium ion battery obtained in step I, and take out the waste lithium-embedded graphite negative electrode;

[0009] III. Soak the waste lithium-embedded graphite negative electrode obtained in step II in an ethanol solution for 30min-1h, the lithium in the graphite reacts with the hydroxyl group of the ethanol solution to generate hydrogen gas, so that the graphite is freed from the interlayer force, and finally obtain a few-layer graphene slurry and a copper foil;

[0010] The volume concentration of ethanol in the ethanol solution is 1-99%;

[0011] IV. Add H2O2 solution to the few-layer graphene slurry obtained in step III and stir for 10-30min to obtain a graphene oxide dispersion;

[0012] The volume concentration of H2O2 in the H2O2 solution is 1-30%;

[0013] The mass of graphene oxide in the graphene oxide dispersion and the volume of water are 1mg:(3mL-4mL);

[0014] V. Crush the copper foil obtained in step III, and then use a high-energy ball mill to make copper powder; uniformly ball mill the copper powder and powdered nano-silicon, the ball milling time is 30min-35min; put the above mixture into a tube furnace, and under the inert atmosphere with a flow rate of 50mL / min-55mL / min and at room temperature, stand for 20min-25min, then calcine under the inert atmosphere and at 300℃-900℃ for 3h-8h, to obtain a silicon-copper alloy composed of Cu3Si and Cu 6.69 Si; wash the obtained silicon-copper alloy with concentrated nitric acid to remove CuSi3 and leave Cu 6.69 Si, then wash with clean water, and dry to obtain nano-porous Cu 6.69 Si silicon-copper alloy particles;

[0015] The mass ratio of the copper powder and the powdered nano-silicon is 3:(2-2.5);

[0016] VI. Ultrasonic dispersion of the nano-porous Cu 6.69 Si particles and a polydiallyldimethylammonium chloride (PDDA) aqueous solution in a solvent deionized water to obtain a porous Cu 6.69 Si / PDDA aqueous solution;

[0017] The mass fraction of the polydiallyldimethylammonium chloride aqueous solution is 20%-22%;

[0018] The nano-porous Cu obtained in step five 6.69 The mass of the Si particles to the volume of the aqueous polydiallyldimethylammonium chloride solution is (200mg-210mg):1mL;

[0019] The volume ratio of the aqueous polydiallyldimethylammonium chloride solution to the solvent deionized water is 1:(40-44);

[0020] Seven, the porous Cu obtained in step six 6.69 The Si / PDDA aqueous solution is poured into the graphene oxide dispersion obtained in step four and is uniformly dispersed by ultrasonic, to obtain the porous Cu 6.69 Si-PDDA-graphene oxide solution;

[0021] The graphene oxide dispersion and the porous Cu obtained in step six 6.69 Si / PDDA aqueous solution is equal in volume;

[0022] Eight, the porous Cu obtained in step seven 6.69 The Si-PDDA-graphene oxide solution is freeze-dried to obtain the porous Cu 6.69 Si-PDDA-graphene oxide powder, and then is placed into a tube furnace, is placed at room temperature for 20min-25min under an inert atmosphere at a flow rate of 50mL / min-55mL / min, and then is calcined at 300℃-900℃ under an inert atmosphere for 3h-8h, to obtain the porous Cu 6.69 Si / graphene powder.

[0023] The nano-porous Cu obtained in step five of the application 6.69 The Si particles have a silicon oxide layer on the surface, and the oxide layer makes the nano-porous silicon particles negatively charged, which provides conditions for subsequent combination of graphene with the nano-porous silicon particles by using the principle of electrostatic adsorption.

[0024] The porous Cu obtained in step eight of the application 6.69 The Cu in the Si / graphene powder can improve the conductivity of the particles, solve the problem of poor conductivity of pure silicon, and the electrochemically inert copper can also act as a skeleton to relieve the volume expansion problem of silicon during the charging and discharging process, and the outer graphene framework can also relieve the problem of volume expansion of silicon.

[0025] The application uses waste lithium ion battery graphite negative electrode to prepare porous Cu 6.69 Si / graphene negative electrode material, realizes the resource recycling of waste lithium ion battery graphite negative electrode, and reduces the production cost of silicon-based negative electrode material, which is of great significance for environmental protection and promoting the update iteration of lithium ion battery negative electrode material.

[0026] The present application has the following advantages and positive significance:

[0027] 1、 The present application can make the waste lithium ion battery graphite negative electrode high-value utilization, which is of great significance for environmental protection and resource saving;

[0028] 2、 The electrostatic adsorption packaging process adopted by the present application is simple and can be applied on a large scale in industry;

[0029] 3、 The present application provides a new idea and solution for solving the problem of silicon substrate volume expansion. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 XRD characterization diagram of the few-layer graphene obtained by freeze-drying of the graphene dispersion liquid obtained in step four of test one;

[0031] Figure 2 SEM diagram of the few-layer graphene oxide obtained by freeze-drying of the graphene dispersion liquid obtained in step four of test one;

[0032] Figure 3 Silicon copper alloy and nano-porous Cu prepared in step five of test one 6.69 XRD characterization diagram of Si silicon copper particles;

[0033] Figure 4 SEM characterization diagram of the silicon copper alloy prepared in step five of test one;

[0034] Figure 5 Nano-porous Cu prepared in step five of test one 6.69 TEM characterization diagram of Si particles.

[0035] Figure 6 SEM diagram of nano-porous Cu prepared in step five of test one 6.69 Si particles;

[0036] Figure 7 TEM diagram of porous Cu 6.69 Si / graphene powder prepared in step eight of test one. DETAILED DESCRIPTION

[0037] Specific implementation one: the present embodiment is a method for preparing graphene composite porous silicon copper alloy negative electrode material by using waste lithium battery negative electrode powder as raw material, which is specifically carried out according to the following steps:

[0038] I. Discharge the waste lithium ion battery to 3.2-3.7V through the battery charging and discharging system;

[0039] II. Disassemble the waste lithium ion battery obtained in step one, and take out the waste lithium-embedded graphite negative electrode;

[0040] III. soaking the waste lithium intercalated graphite negative electrode obtained in step II in an ethanol solution for 30 min to 1 h, so that lithium in the graphite reacts with hydroxyl groups in the ethanol solution to generate hydrogen gas, and the graphite is freed from interlayer forces, thereby obtaining a few-layer graphene slurry and a copper foil;

[0041] The volume concentration of ethanol in the ethanol solution is 1% to 99%;

[0042] IV. adding an H2O2 solution to the few-layer graphene slurry obtained in step III and stirring for 10 min to 30 min to obtain a graphene oxide dispersion;

[0043] The volume concentration of H2O2 in the H2O2 solution is 1% to 30%;

[0044] The mass of graphene oxide to the volume of water in the graphene oxide dispersion is 1 mg:(3 mL to 4 mL);

[0045] V. crushing the copper foil obtained in step III, and then using a high-energy ball mill to form copper powder; uniformly ball-milling the copper powder and powdered nanosilicon, for a ball-milling time of 30 min to 35 min; placing the mixture into a tube furnace, and allowing the mixture to stand in an inert atmosphere at a flow rate of 50 mL / min to 55 mL / min and at room temperature for 20 min to 25 min, and then calcining the mixture in an inert atmosphere at 300°C to 900°C for 3 h to 8 h, to obtain a silicon-copper alloy composed of Cu3Si and Cu 6.69 Si; washing the obtained silicon-copper alloy with concentrated nitric acid to remove Cu3Si and leave Cu 6.69 Si, and then washing with clean water and drying, to obtain nanometer porous Cu 6.69 Si silicon-copper alloy particles;

[0046] The mass ratio of the copper powder to the powdered nanosilicon is 3:(2 to 2.5);

[0047] VI. ultrasonically dispersing the nanometer porous Cu 6.69 Si particles and a polydiallyldimethylammonium chloride (PDDA) aqueous solution in a solvent, deionized water, to obtain a porous Cu 6.69 Si / PDDA aqueous solution;

[0048] The mass fraction of the polydiallyldimethylammonium chloride aqueous solution is 20% to 22%;

[0049] The mass of the nanometer porous Cu 6.69 Si particles obtained in step V to the volume of the polydiallyldimethylammonium chloride aqueous solution is (200 mg to 210 mg):1 mL;

[0050] The volume ratio of the polydiallyldimethylammonium chloride aqueous solution to the solvent deionized water is 1: (40-44).

[0051] Seven, taking the porous Cu obtained in step six 6.69 The Si / PDDA aqueous solution is poured into the graphene oxide dispersion obtained in step four and is uniformly dispersed by ultrasonic, to obtain porous Cu 6.69 Si-PDDA-graphene oxide solution;

[0052] The graphene oxide dispersion obtained in step six is added into the porous Cu 6.69 The Si / PDDA aqueous solution is added into the graphene oxide dispersion obtained in step four in an equal volume.

[0053] Eight, the porous Cu obtained in step seven 6.69 The Si-PDDA-graphene oxide solution is freeze-dried to obtain porous Cu 6.69 The Si-PDDA-graphene oxide powder is then placed into a tube furnace, and is allowed to stand at room temperature for 20-25 min under an inert atmosphere at a flow rate of 50-55 mL / min, and is then calcined under an inert atmosphere at 300-900°C for 3-8 h, to obtain porous Cu 6.69 Si / graphene powder.

[0054] Specific embodiment two: the embodiment is different from specific embodiment one in that the rotation speed of the copper powder and the powdered nanosilicon in step five is 8000 rpm. The other steps are the same as those in specific embodiment one.

[0055] The present application is verified by the following tests:

[0056] Test one: a method for preparing a graphene composite porous silicon copper alloy negative electrode material by using waste lithium battery negative electrode powder as raw material, which is specifically performed according to the following steps:

[0057] One, discharging the waste lithium ion battery to 3.7 V through a battery charging and discharging system;

[0058] Two, disassembling the waste lithium ion battery obtained in step one, and taking out the waste lithium-embedded graphite negative electrode;

[0059] Three, soaking the waste lithium-embedded graphite negative electrode obtained in step two in an ethanol solution for 30 min, so that lithium in the graphite reacts with hydroxyl groups in the ethanol solution to generate hydrogen gas, and the graphite is freed from interlayer forces, to finally obtain a few-layer graphene slurry and a copper foil.

[0060] The volume concentration of ethanol in the ethanol solution is 50%.

[0061] Four, adding an H2O2 solution to the few-layer graphene slurry obtained in step three and stirring for 10 min, to obtain a graphene oxide dispersion.

[0062] The volume concentration of H2O2 in the H2O2 solution is 20%;

[0063] The mass of graphene oxide to the volume of water in the graphene oxide dispersion solution is 1 mg:3 mL;

[0064] Five, the copper foil obtained in step three is crushed, and then copper powder is prepared by using a high-energy ball mill; the copper powder and the powdered nanometer silicon are uniformly ball milled for 30 min; the mixture is placed in a tube furnace, and is allowed to stand for 20 min under an inert atmosphere at a flow rate of 50 mL / min and at room temperature, and then is calcined under an inert atmosphere at 300°C for 3 h to obtain a silicon-copper alloy composed of Cu3Si and Cu 6.69 Si; the obtained silicon-copper alloy is washed with concentrated nitric acid to remove Cu3Si and leave Cu 6.69 Si, and then is washed with clean water and dried to obtain nanoporous Cu 6.69 Si silicon-copper alloy particles;

[0065] The mass ratio of the copper powder to the powdered nanometer silicon is 3:2;

[0066] Six, ①: the nanoporous Cu 6.69 Si particles obtained in step four and an aqueous solution of polydiallyldimethylammonium chloride (PDDA) are ultrasonically dispersed in a solvent, deionized water, to obtain a porous Cu 6.69 Si / PDDA aqueous solution;

[0067] The mass fraction of the aqueous solution of polydiallyldimethylammonium chloride is 20%;

[0068] The mass of the nanoporous Cu 6.69 Si particles obtained in step four to the volume of the aqueous solution of polydiallyldimethylammonium chloride is 200 mg:1 mL;

[0069] The volume ratio of the aqueous solution of polydiallyldimethylammonium chloride to the solvent, deionized water, is 1:40;

[0070] Seven, the porous Cu 6.69 Si / PDDA aqueous solution obtained in step six is poured into the graphene oxide dispersion solution obtained in step four and is ultrasonically dispersed to obtain a porous Cu 6.69 Si-PDDA-graphene oxide solution;

[0071] The volume of the graphene oxide dispersion solution is equal to that of the porous Cu 6.69 Si / PDDA aqueous solution obtained in step six;

[0072] Eight, the porous Cu 6.69Si-PDDA-graphene oxide solution was freeze-dried to obtain porous Cu 6.69 Si-PDDA-graphene oxide powder was then placed in a tube furnace, and was kept at room temperature for 20 min under an inert atmosphere at a flow rate of 50 mL / min, and was then calcined under an inert atmosphere at 300℃ for 3 h to obtain porous Cu 6.69 Si / graphene powder.

[0073] Figure 1 XRD characterization diagram of the directly scraped graphite in the waste lithium intercalated graphite negative electrode in step two of Test One and the few-layer graphene oxide obtained by freeze-drying of the graphene dispersion obtained in step four of Test One, SG is the separated graphite in step two of Test One, and GO is the few-layer graphene oxide obtained by freeze-drying of the graphene dispersion obtained in step four of Test One, it can be seen that the graphite is expanded due to the generated hydrogen, and the graphite layer spacing is increased after the H2O2 solution oxidation treatment, and single-layer or few-layer graphene oxide is gradually formed.

[0074] Figure 2 SEM diagram of the few-layer graphene oxide obtained by freeze-drying of the graphene dispersion obtained in step four of Test One, it can be seen that the prepared graphene oxide is single-layer and relatively complete.

[0075] Figure 3 XRD characterization diagram of the silicon-copper alloy and nano-porous silicon particles prepared in step five of Test One, it can be seen that the copper is completely removed after acid washing of the silicon-copper alloy prepared from nano-silicon powder and copper powder, and the silicon-copper alloy is mainly composed of Cu3Si and Cu6.69Si.

[0076] Figure 4 SEM characterization diagram of the silicon-copper alloy prepared in step five of Test One.

[0077] Figure 5 TEM characterization diagram of the nano-porous Cu6.69Si particles prepared in step five of Test One, it can be seen that there is a silicon oxide layer with a thickness of about 20 nm~40 nm on the surface of the nano-porous silicon particles, and this oxide layer makes the nano-porous silicon particles negatively charged, which provides conditions for subsequent combination of graphene and the nano-porous silicon particles by using the principle of electrostatic adsorption.

[0078] Figure 6 SEM diagram of the nano-porous Cu6.69Si particles prepared in step five of Test One, it can be seen that after the Cu3Si in the silicon-copper alloy is washed away with nitric acid, the silicon material presents a honeycomb-like porous structure, and these voids can provide a buffer space for the porous Cu 6.69 The volume expansion of the Si / graphene negative electrode material in the charging and discharging process provides a buffer space, and the Cu skeleton can also increase the conductivity and stability of the material.

[0079] Figure 7Porous Cu prepared for step eight of experiment one 6.69 TEM image of Si / graphene powder. It can be seen that a layer of graphene is wrapped on the surface of porous silicon. Due to the ductility and excellent mechanical properties of graphene, it provides a firm and tough skeleton for the internal porous silicon. This is another guarantee for the relief of volume expansion of silicon-based negative electrode materials during the charging and discharging process.

Claims

1. A method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material, characterized in that... The method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material is carried out according to the following steps:

1. Discharge used lithium-ion batteries to 3.2-3.7V using a battery charging and discharging system; 2. Disassemble the waste lithium-ion batteries obtained in step one and remove the waste lithium-intercalated graphite anode.

3. Immerse the waste lithium-intercalated graphite anode obtained in step 2 in an ethanol solution for 30 min to 1 h. The lithium in the graphite reacts with the hydroxyl groups in the ethanol solution to generate hydrogen gas, which allows the graphite to get rid of the interlayer forces and finally obtain a few-layer graphene slurry and copper foil. The ethanol solution has a volume concentration of 1-99%.

4. Add H2O2 solution to the few-layer graphene slurry obtained in step 3 and stir for 10-30 min to obtain graphene oxide dispersion; The volume concentration of H2O2 in the H2O2 solution is 1-30%; The mass ratio of graphene oxide to water in the graphene oxide dispersion is 1 mg: (3 mL~4 mL); 5. Crush the copper foil obtained in step 3, and then use a high-energy ball mill to produce copper powder; ball mill the copper powder and powdered nano-silicon evenly for 30-35 minutes; place the mixture in a tube furnace and let it stand for 20-25 minutes at room temperature under an inert atmosphere with a flow rate of 50-55 mL / min, and then calcine it at 300-900℃ for 3-8 hours under an inert atmosphere to obtain Cu3Si and Cu 6.69 A silicon-copper alloy composed of Si was obtained; the resulting silicon-copper alloy was washed with concentrated nitric acid to remove Cu3Si, leaving Cu. 6.69 Si was then washed with water and dried to obtain nanoporous Cu. 6.69 Si-copper alloy particles; The mass ratio of copper powder to powdered nano-silicon is 3:(2~2.5); VI. The nanoporous Cu obtained in step five 6.69 Porous Cu particles were obtained by ultrasonic dispersion of Si particles and polydiallyldimethylammonium chloride (PDDA) aqueous solution in deionized water. 6.69 Si / PDDA aqueous solution; The mass fraction of the polydiallyl dimethylammonium chloride aqueous solution is 20%~22%; The nanoporous Cu obtained in step five is described above. 6.69 The mass ratio of Si particles to the volume ratio of polydiallyldimethylammonium chloride aqueous solution is (200mg~210mg):1mL; The volume ratio of the polydiallyldimethylammonium chloride aqueous solution to the solvent deionized water is 1:(40~44); VII. Take the porous Cu obtained in step six. 6.69 The Si / PDDA aqueous solution was poured into the graphene oxide dispersion obtained in step four and ultrasonically dispersed until uniform, resulting in porous Cu. 6.69 Si-PDDA-graphene oxide solution; The graphene oxide dispersion and the porous Cu obtained in step six 6.69 Equal volumes of Si / PDDA aqueous solution; 8. The porous Cu obtained in step 7 6.69 Si-PDDA-graphene oxide solution was freeze-dried to obtain porous Cu. 6.69 Si-PDDA-graphene oxide powder was then placed in a tube furnace and allowed to stand for 20-25 minutes at room temperature under an inert atmosphere with a flow rate of 50-55 mL / min. Following this, it was calcined at 300-900℃ for 3-8 hours under an inert atmosphere to obtain porous Cu. 6.69 Si / graphene powder.

2. The method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material according to claim 1, characterized in that... In step five, the copper foil is broken using scissors or a shredder.

3. The method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material according to claim 1, characterized in that... In step five, the ball milling speed for copper powder and powdered nano-silicon is 8000 rpm.

4. The method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material according to claim 1, characterized in that... The inert atmosphere mentioned in step five is argon.

5. The method for preparing graphene composite porous silicon-copper alloy anode material using waste lithium battery anode powder as raw material according to claim 1, characterized in that... The inert atmosphere mentioned in step eight is argon.

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