A wet recycling method for waste lithium batteries based on crop straw

Abstract

This invention relates to the field of lithium battery recycling technology using biomass, and discloses a wet recycling method for waste lithium batteries based on crop straw, comprising the following steps: Step 1, crushing and sieving the crop straw, drying it to constant weight, then reacting it with dilute sulfuric acid, cooling and filtering to obtain filtrate; Step 2, pretreatment of the positive electrode powder of the waste lithium battery; Step 3, wet recycling of the positive electrode powder of the waste lithium battery: mixing the filtrate with the positive electrode powder, heating and stirring in an oil bath, filtering, and separating the filtrate for later use; Step 4, determining the lithium content and calculating its recovery rate. This invention employs the above-mentioned wet recycling method for waste lithium batteries based on crop straw, using the reducing sugars and acids in the acidic pretreatment hydrolysate of straw as reducing agents and leaching agents for waste lithium battery recycling. The lithium batteries are recycled through a wet-chemical precipitation method, which not only improves the recycling rate of agricultural waste but also reduces the environmental pollution caused by waste lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of biomass-based lithium battery recycling technology, and in particular to a wet recycling method for waste lithium batteries based on crop straw. Background Technology

[0002] Crop straw is a major raw material for biomass energy. my country's agricultural production generates approximately 900 million tons of straw annually, which can produce about 200 billion liters of biofuel. Currently, straw utilization is mainly based on simple return to the field as fertilizer, while also incorporating other uses such as feed, fuel, substrate, and raw materials. Although the ecological benefits of returning straw to the field are significant, the lack of high-value product conversion prevents the realization of both economic and ecological benefits. The energy and material conversion of straw as a raw material holds promise for enhancing its economic value, especially the conversion into bioenergy. This would not only improve the economic efficiency of straw utilization but also promote emission reduction and simultaneously achieve ecological benefits. However, despite this, straw conversion into bioenergy requires pretreatment to hydrolyze polysaccharide components such as cellulose into monosaccharides for fermentation to produce alcohols. This process also generates a large amount of fiber residue. Currently, the development of bioenergy faces challenges such as low sugar content in hydrolysate, difficulty in utilization, and high fiber residue with low utilization rates, resulting in low bioenergy conversion rates and limiting its vigorous development.

[0003] Lithium-ion batteries are batteries that use lithium metal or lithium alloy as the negative electrode material and a non-aqueous electrolyte solution. Among rechargeable battery technologies, they have high energy density and good overall performance, and their market share has been increasing year by year since their inception. Compared with other rechargeable batteries, lithium-ion batteries have advantages such as high energy density, high voltage, long lifespan, and fast charge / discharge speed, and currently occupy a major market share in batteries for electronic products such as mobile phones and laptops. With the widespread use of lithium batteries, the recycling and disposal of waste lithium batteries has become a major issue. Currently, there are roughly three internationally accepted methods for disposing of waste batteries: solidification and deep burial, storage in abandoned mines, and recycling. However, because batteries contain various toxic volatile substances, solidification and deep burial, and storage in abandoned mines will have unavoidable environmental impacts. Therefore, compared to the other two methods, battery recycling is the best way to dispose of waste batteries. Waste lithium battery recycling technologies mainly include three methods: physical separation, biochemical treatment, and chemical treatment. Physical separation includes flotation and grinding methods, which have good separation effects and high metal recovery rates. Biochemical treatment utilizes microorganisms to decompose battery materials and selectively leach certain elements, but this method is still immature and has no practical application. Chemical treatment methods are mainly divided into pyrometallurgical processes and hydrometallurgical processes.

[0004] The purpose of this invention is to use straw as a link to develop waste lithium battery recycling technology, construct a new system for clean energy conversion, achieve efficient recycling of waste lithium batteries, promote the development of bioenergy, and contribute to the development of a green circular economy. It provides a new solution for the recycling of waste lithium batteries and the high-value utilization of crop straw. Summary of the Invention

[0005] The purpose of this invention is to provide a wet recycling method for waste lithium batteries based on crop straw. The reducing sugars and acids in the acidic pretreatment hydrolysate of straw are used as reducing agents and leaching agents for recycling waste lithium batteries. The lithium batteries are recycled through a wet-chemical precipitation method, which not only improves the recycling rate of agricultural waste, but also reduces the environmental pollution caused by waste lithium batteries.

[0006] To achieve the above objectives, this invention provides a wet recycling method for waste lithium batteries based on crop straw, comprising the following steps:

[0007] Step 1: Crush the crop straw through a 40-80 mesh sieve, dry it to constant weight, and then react it with 1%-2% dilute sulfuric acid, dilute nitric acid, or dilute hydrochloric acid. After cooling to room temperature, filter to obtain the filtrate, which is then stored for later use. The resulting filter residue can be used for enzymatic hydrolysis to produce ethanol, thus achieving recycling.

[0008] Step 2, Pretreatment of waste lithium battery cathode powder:

[0009] ① Discharge the waste lithium battery with a saturated salt solution for 8-16 hours, then vacuum dry the treated waste lithium battery at 80-100℃ for 12-24 hours. After drying, manually disassemble and separate to obtain the positive electrode material.

[0010] ② The positive electrode material is vacuum pyrolyzed at 400-500℃ for 1-3 h to burn off the organic binder. After pyrolysis, the current collector and positive electrode powder are manually separated, and the positive electrode powder is passed through a 120-180 mesh sieve.

[0011] Step 3, wet recycling of waste lithium battery cathode powder: The filtrate from Step 1 is mixed with the cathode powder from Step 2 in a certain proportion, heated and stirred in an oil bath, and after filtration, the filtrate and filter residue are separated for later use; to ensure complete recovery of lithium, the filter residue is rinsed with ultrapure water 2 to 3 times, and then the filtrates from multiple rinses are combined.

[0012] Step 4, determine the lithium content and calculate its recovery rate: use an atomic absorption spectrometer to measure the filtrate from step 3 to obtain the lithium content and calculate the lithium recovery rate.

[0013] Step 5: Effective recovery of lithium using chemical precipitation method: Add saturated sodium carbonate solution to the filtrate from step 3 to recover the valuable metal in the form of precipitate, and then wash and dry it with water to obtain Li2CO3 powder.

[0014] Furthermore, the crop straw in step 1 includes one or more of the following: corn straw, rice straw, rapeseed straw, and cotton straw.

[0015] Furthermore, in step 1, the solid-liquid ratio of crop straw to dilute sulfuric acid is 1g:10mL-1g:25mL.

[0016] Furthermore, in step 1, the reaction conditions between crop straw and dilute sulfuric acid are a temperature of 60℃-140℃ and a time of 20-80 min.

[0017] Furthermore, the saturated salt solution in step 2 includes one or more of NaCl solution, FeSO4 solution, or Na2SO4 solution; the waste lithium battery is a waste lithium iron phosphate battery, a waste lithium cobalt oxide battery, or a waste ternary lithium battery.

[0018] Furthermore, in step 3, the solid-liquid ratio of the positive electrode powder to the filtrate is 10-30 g: 1L.

[0019] Furthermore, in step 3, the reaction conditions in the oil bath are a temperature of 50-100℃ and a time of 50-120 min.

[0020] The advantages and positive effects of the wet recycling method for waste lithium batteries based on crop straw described in this invention are as follows:

[0021] 1. This invention provides a method for recycling waste lithium batteries based on crop straw. The method involves pretreating the straw with dilute sulfuric acid. The pretreatment hydrolysate contains sulfuric acid, cellulose, and their degradation products. The monosaccharides obtained from the degradation (such as glucose) can be used as a reducing agent in the wet recycling of waste lithium batteries, and the dilute sulfuric acid can be used as a leaching agent. The lithium battery cathode material is recovered through a wet-chemical precipitation method, achieving a lithium recovery rate of 50%-80%. Simultaneously, the recovered lithium carbonate can be used for the remanufacturing of lithium batteries.

[0022] 2. This invention utilizes the low-concentration sugars in the acid pretreatment hydrolysate of crop straw, which are difficult to utilize, for the recycling of lithium battery cathode materials, thereby simultaneously achieving high-value utilization of crop straw and efficient recycling of waste lithium batteries, and promoting green and sustainable social development.

[0023] 3. This invention uses the reducing sugars and dilute sulfuric acid in the acidic pretreatment hydrolysate of straw as reducing agents and leaching agents for recycling waste lithium batteries. It recovers lithium battery cathode materials through a wet-chemical precipitation method, opening up a new path for high-value transformation of "waste treatment", while improving the recycling rate of agricultural waste and reducing the environmental pollution caused by waste lithium batteries.

[0024] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0025] The technical solution of the present invention will be further described below through embodiments.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0027] Unless otherwise defined, the instruments, equipment and reagents used in this invention are all commercially available.

[0028] Example 1

[0029] A method for recycling waste lithium batteries based on crop straw includes the following steps:

[0030] Step 1: Crush the straw through a 40-80 mesh sieve, dry it to constant weight, react it with 1%-2% dilute sulfuric acid at 60℃-140℃ for 20-80 min, cool it to room temperature, filter it, and store the filtrate for later use. The solid-liquid ratio of straw to dilute sulfuric acid is 1:10.

[0031] Step 2: Discharge spent lithium iron phosphate batteries, spent lithium cobalt oxide batteries, and spent ternary lithium batteries for 8-16 hours using saturated NaCl solution, FeSO4 solution, and Na2SO4 solution. Then, vacuum dry the treated spent lithium batteries at 80-100℃ for 12-24 hours. Next, transfer the spent lithium batteries to an operating box and manually disassemble and separate them to obtain the positive electrode material. Transfer the positive electrode material to a tube furnace and vacuum pyrolyze it at 400-500℃ for 1-3 hours to burn off the organic binder. After pyrolysis, manually peel off the current collector and positive electrode powder, and pass the positive electrode powder through a 120-180 mesh sieve.

[0032] Step 3: The filtrate from Step 1 and the positive electrode powder from Step 2 are mixed at a solid-liquid ratio of 15 g / L and heated and stirred in an oil bath at 60°C for 2 hours.

[0033] Step 4: Measure the solution from Step 3 using an atomic absorption spectrometer to determine the lithium content and calculate the lithium recovery rate.

[0034] Step 5: Add saturated sodium carbonate solution to the filtrate from Step 3 to recover the valuable metal in the form of a precipitate. Then, wash and dry the precipitate with water to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for the remanufacturing of lithium batteries.

[0035] Example 2

[0036] A method for recycling waste lithium batteries based on crop straw includes the following steps:

[0037] Step 1: Crush the straw through a 40-80 mesh sieve, dry it to constant weight, react it with 1%-2% dilute sulfuric acid at 60℃-140℃ for 20-80 min, cool it to room temperature, filter it, and store the filtrate for later use. The solid-liquid ratio of straw to dilute sulfuric acid is 1:15.

[0038] Step 2: Discharge spent lithium iron phosphate batteries, spent lithium cobalt oxide batteries, and spent ternary lithium batteries for 8-16 hours using saturated NaCl solution, FeSO4 solution, and Na2SO4 solution. Then, vacuum dry the treated spent lithium batteries at 80-100℃ for 12-24 hours. Next, transfer the spent lithium batteries to an operating box and manually disassemble and separate them to obtain the positive electrode material. Transfer the positive electrode material to a tube furnace and vacuum pyrolyze it at 400-500℃ for 1-3 hours to burn off the organic binder. After pyrolysis, manually peel off the current collector and positive electrode powder, and pass the positive electrode powder through a 120-180 mesh sieve.

[0039] Step 3: The filtrate from Step 1 and the positive electrode powder from Step 2 are mixed at a solid-liquid ratio of 25 g / L and heated and stirred in an oil bath at 70°C for 2 hours.

[0040] Step 4: Measure the solution from Step 3 using an atomic absorption spectrometer to determine the lithium content and calculate the lithium recovery rate.

[0041] Step 5: Add saturated sodium carbonate solution to the filtrate from Step 3 to recover the valuable metal in the form of a precipitate. Then, wash and dry the precipitate with water to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for the remanufacturing of lithium batteries.

[0042] Example 3

[0043] A method for recycling waste lithium batteries based on crop straw includes the following steps:

[0044] Step 1: Crush the straw through a 40-80 mesh sieve, dry it to constant weight, react it with 1%-2% dilute sulfuric acid at 60℃-140℃ for 20-80 min, cool it to room temperature, filter it, and store the filtrate for later use. The solid-liquid ratio of straw to dilute sulfuric acid is 1:20.

[0045] Step 2: Discharge spent lithium iron phosphate batteries, spent lithium cobalt oxide batteries, and spent ternary lithium batteries for 8-16 hours using saturated NaCl solution, FeSO4 solution, and Na2SO4 solution. Then, vacuum dry the treated spent lithium batteries at 80-100℃ for 12-24 hours. Next, transfer the spent lithium batteries to an operating box and manually disassemble and separate them to obtain the positive electrode material. Transfer the positive electrode material to a tube furnace and vacuum pyrolyze it at 400-500℃ for 1-3 hours to burn off the organic binder. After pyrolysis, manually peel off the current collector and positive electrode powder, and pass the positive electrode powder through a 120-180 mesh sieve.

[0046] Step 3: The filtrate from Step 1 and the positive electrode powder from Step 2 are mixed at a solid-liquid ratio of 30 g / L and heated and stirred in an oil bath at 80°C for 2 hours.

[0047] Step 4: Measure the solution from Step 3 using an atomic absorption spectrometer to determine the lithium content and calculate the lithium recovery rate.

[0048] Step 5: Add saturated sodium carbonate solution to the filtrate from Step 3 to recover the valuable metal in the form of a precipitate. Then, wash and dry the precipitate with water to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for the remanufacturing of lithium batteries.

[0049] Example 4

[0050] A method for recycling waste lithium batteries based on crop straw includes the following steps:

[0051] Step 1: Crush the straw through a 40-80 mesh sieve, dry it to constant weight, react it with 1%-2% dilute sulfuric acid at 60℃-140℃ for 20-80 min, cool it to room temperature, filter it, and store the filtrate for later use. The solid-liquid ratio of straw to dilute sulfuric acid is 1:25.

[0052] Step 2: Discharge spent lithium iron phosphate batteries, spent lithium cobalt oxide batteries, and spent ternary lithium batteries for 8-16 hours using saturated NaCl solution, FeSO4 solution, and Na2SO4 solution. Then, vacuum dry the treated spent lithium batteries at 80-100℃ for 12-24 hours. Next, transfer the spent lithium batteries to an operating box and manually disassemble and separate them to obtain the positive electrode material. Transfer the positive electrode material to a tube furnace and vacuum pyrolyze it at 400-500℃ for 1-3 hours to burn off the organic binder. After pyrolysis, manually peel off the current collector and positive electrode powder, and pass the positive electrode powder through a 120-180 mesh sieve.

[0053] Step 3: The filtrate from Step 1 and the positive electrode powder from Step 2 are mixed at a solid-liquid ratio of 25 g / L and heated and stirred in an oil bath at 90°C for 2 hours.

[0054] Step 4: Measure the solution from Step 3 using an atomic absorption spectrometer to determine the lithium content and calculate the lithium recovery rate.

[0055] Step 5: Add saturated sodium carbonate solution to the filtrate from Step 3 to recover the valuable metal in the form of a precipitate. Then, wash and dry the precipitate with water to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for the remanufacturing of lithium batteries.

[0056] The lithium recovery rate in this embodiment is shown in Table 1.

[0057] Table 1

[0058]

[0059] As can be seen from the test data in Table 1, under the same reaction time, the lithium leaching rate increases with increasing temperature, which significantly proves the effectiveness of the method.

[0060] Therefore, the present invention adopts the above-mentioned wet recycling method for waste lithium batteries based on crop straw, using the reducing sugars and acids in the acidic pretreatment hydrolysate of straw as reducing agents and leaching agents for recycling waste lithium batteries. The lithium batteries are recycled through a wet-chemical precipitation method, which not only improves the recycling rate of agricultural waste, but also reduces the environmental pollution caused by waste lithium batteries.

[0061] 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 them. 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 still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A wet recycling method for waste lithium batteries based on crop straw, characterized in that, Includes the following steps: Step 1: Crush the crop straw through a 40-80 mesh sieve, dry it to constant weight, then react it with 1%-2% dilute sulfuric acid, cool it to room temperature, filter it, and store the filtrate for later use. Step 2, Pretreatment of waste lithium battery cathode powder: ① Discharge the waste lithium battery with a saturated salt solution for 8-16 hours, then vacuum dry the treated waste lithium battery at 80-100℃ for 12-24 hours. After drying, manually disassemble and separate to obtain the positive electrode material. ② The positive electrode material is vacuum pyrolyzed at 400-500℃ for 1-3 h to burn off the organic binder. After pyrolysis, the current collector and positive electrode powder are manually separated, and the positive electrode powder is passed through a 120-180 mesh sieve. Step 3, wet recycling of waste lithium battery cathode powder: Mix the filtrate from Step 1 with the cathode powder from Step 2 in a certain proportion, heat and stir in an oil bath, and after filtration, separate the filtrate and filter residue for later use. Step 4, determine the lithium content and calculate its recovery rate: use an atomic absorption spectrometer to measure the filtrate from step 3 to obtain the lithium content and calculate the lithium recovery rate. Step 5: Effective recovery of lithium using chemical precipitation method: Add saturated sodium carbonate solution to the filtrate from step 3 to recover lithium in the form of precipitation, then wash and dry with water to obtain Li2CO3 powder; In step 1, the solid-liquid ratio of crop straw to dilute sulfuric acid is 1g:10ml - 1g:25ml; In step 1, the reaction conditions between crop straw and dilute sulfuric acid are: temperature 60℃-140℃, time 20-80 min; In step 3, the solid-liquid ratio of the positive electrode powder to the filtrate is 10-40 g / L; In step 3, the reaction conditions in the oil bath are a temperature of 50-100℃ and a time of 50-120 min.

2. The wet recycling method for waste lithium batteries based on crop straw according to claim 1, characterized in that: The crop straw in step 1 includes one or more of the following: corn straw, rice straw, rapeseed straw, and cotton straw.

3. The wet recycling method for waste lithium batteries based on crop straw according to claim 1, characterized in that: The saturated salt solution in step 2 includes one or more of NaCl solution, FeSO4 solution, or Na2SO4 solution; the waste lithium battery is a waste lithium iron phosphate battery, a waste lithium cobalt oxide battery, or a waste ternary lithium battery.

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