Waste lithium battery wet recovery method based on crop straw

Abstract

The invention relates to the technical field of recycling lithium batteries by utilizing biomass, and discloses a waste lithium battery wet-process recycling method based on crop straws, which comprises the following steps: step 1, crushing the crop straws, sieving, drying to constant weight, reacting with dilute sulphuric acid, cooling, and filtering to obtain filtrate; step 2, pretreatment of waste lithium battery positive electrode powder; 3, wet recovery of waste lithium battery positive electrode powder: mixing the filtrate with the positive electrode powder, heating and stirring in an oil bath pan, carrying out suction filtration, and separating the filtrate for later use; and 4, measuring the content of lithium and calculating the recovery rate. According to the waste lithium battery wet recycling method based on the crop straw, reducing sugar and acid in the straw acid pretreatment hydrolysate serve as a reducing agent and a leaching agent for recycling the waste lithium battery, the lithium battery is recycled through a wet-chemical precipitation method, the cyclic utilization rate of agricultural waste is increased, and the recycling rate of the waste lithium battery is increased. And the pollution of the waste lithium battery to the environment is also reduced.

Description

Technical Field

[0001] The invention relates to the technical field of recycling lithium batteries using biomass, and in particular to a wet recycling method for waste lithium batteries based on crop straws. Background Art

[0002] Crop straw is the main raw material for biomass energy. my country's agricultural production produces about 900 million tons of straw each year, which can produce about 200 billion liters of biofuel. At present, the utilization of straw is still mainly based on simple fertilizer utilization in the field, while it also has feed, fuel, base material, and raw material utilization modes. Although the ecological benefits of returning to the field are significant, the lack of high-value product conversion cannot achieve both the economic and ecological benefits of straw utilization. The energy and material conversion of straw as raw material is expected to increase the economic value of straw utilization, especially the conversion of straw into bioenergy, which can not only improve the economic benefits of straw utilization, but also promote emission reduction and achieve the ecological benefits of straw utilization at the same time. However, despite this, the conversion of straw into bioenergy requires pretreatment first, and the polysaccharide components such as cellulose in the straw are hydrolyzed into monosaccharides for fermentation and alcohol production. This process also produces a large amount of fiber residue. At present, the development of bioenergy faces difficulties such as low utilization of hydrolyzate sugar and low utilization rate of large fiber residues, resulting in low bioenergy conversion rate and limiting the vigorous development of bioenergy.

[0003] Lithium batteries are batteries that use lithium metal or lithium alloy as negative electrode materials and non-aqueous electrolyte solutions. They have high energy density and good comprehensive performance in secondary battery technology. Their market share has increased year by year since their birth. Compared with other rechargeable batteries, lithium-ion batteries have the advantages of high energy density, high voltage, long life, and fast charging and discharging speed. At present, they have occupied the main market of batteries for electronic products such as mobile phones and laptops. With the large-scale use of lithium batteries, the recycling and treatment of waste lithium batteries has also become a big problem. At present, there are roughly three ways to deal with waste batteries in the world: solidification and deep burial, storage in waste mines, and recycling. However, since the battery contains a variety of toxic volatiles, solidification and deep burial and storage in waste mines will have an irresistible impact on the environment. Therefore, compared with the other two methods, battery recycling is the best way to deal with waste batteries. The recycling technology of waste lithium batteries mainly includes three methods: physical separation, biochemical treatment, and chemical treatment. Physical separation includes flotation and grinding, which have good separation effect and high metal recovery rate. Biochemical treatment uses microorganisms to decompose battery materials and selectively leach certain elements, but it is still immature and has no practical application. Chemical treatment methods are mainly divided into pyrometallurgical processes and wet processes.

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

[0005] The purpose of the present invention is to provide a wet recovery method for waste lithium batteries based on crop straw, using reducing sugars and acids in the straw acid pretreatment hydrolyzate as reducing agents and leaching agents for recycling waste lithium batteries, and recycling lithium batteries through a wet-chemical precipitation method, which not only improves the recycling rate of agricultural waste, but also reduces the pollution of waste lithium batteries to the environment.

[0006] To achieve the above object, the present invention provides a wet recovery method for waste lithium batteries based on crop straw, comprising the following steps: Step 1, crushing the crop straw through a 40-80 mesh sieve, drying to constant weight, and then reacting with 1%-2% dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, cooling to room temperature and filtering to obtain a filtrate, which is stored for later use; the obtained filter residue can be used for enzymatic fermentation to produce bioethanol, so as to achieve recycling; Step 2: Pretreatment of waste lithium battery positive electrode powder: ① Use saturated salt solution to discharge the waste lithium battery 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 Pyrolyze the cathode material in a vacuum at 400-500℃ for 1-3 h to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and cathode powder, and pass the cathode powder through a 120-180 mesh sieve; Step 3, wet recovery of positive electrode powder of waste lithium batteries: the filtrate in step 1 is mixed with the positive electrode powder in step 2 in proportion, heated and stirred in an oil bath, and after suction filtration, the filtrate and filter residue are separated for standby use; to ensure complete recovery of lithium elements, the filter residue will be rinsed with ultrapure water 2 to 3 times, and then the filtrates of multiple times will be combined; Step 4, determining the lithium content and calculating its recovery rate: using an atomic absorption spectrometer to measure the filtrate of step 3, obtaining the lithium content, and calculating the lithium recovery rate; Step 5, using chemical precipitation method to effectively recover lithium: adding saturated sodium carbonate solution to the filtrate in step 3, recovering valuable metals in the form of precipitation, and then washing and drying to obtain Li2CO3 powder.

[0007] Furthermore, the crop straw in step 1 includes one or more of corn straw, rice straw, rape straw, and cotton straw.

[0008] Furthermore, in step 1, the solid-liquid ratio of the crop straw to the dilute sulfuric acid is 1 g:10 mL-1 g:25 mL.

[0009] Furthermore, in step 1, the reaction conditions of the crop straw and dilute sulfuric acid are a temperature of 60° C.-140° C. and a time of 20-80 min.

[0010] 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.

[0011] Furthermore, in step 3, the solid-liquid ratio of the positive electrode powder to the filtrate is 10-30 g:1L.

[0012] Furthermore, the reaction conditions of the oil bath in step 3 are a temperature of 50-100° C. and a time of 50-120 min.

[0013] The advantages and positive effects of the wet recycling method of waste lithium batteries based on crop straw described in the present invention are: 1. The present invention provides a method for recycling waste lithium batteries based on crop straw, wherein dilute sulfuric acid is used to pretreat the straw, and the pretreatment hydrolyzate contains sulfuric acid, cellulose and its degradation products, wherein the monosaccharide (such as glucose) obtained by degradation can be used as a reducing agent for wet recycling of waste lithium batteries, and dilute sulfuric acid can be used as a leaching agent for wet recycling of waste lithium batteries. The positive electrode material of lithium batteries is recovered by wet-chemical precipitation method, and the recovery rate of lithium obtained is 50%-80%, and the recovered lithium carbonate can be used for remanufacturing of lithium batteries.

[0014] 2. The present invention uses the difficult-to-use low-concentration sugar in the acid pretreated hydrolyzate of crop straw to recover the positive electrode material of lithium batteries, simultaneously realizing the high-value utilization of crop straw and the efficient recovery of waste lithium batteries, and promoting the green and sustainable development of society.

[0015] 3. The present invention uses reducing sugars and dilute sulfuric acid in the acid pretreatment hydrolyzate of straw as reducing agents and leaching agents for recycling waste lithium batteries, and recovers lithium battery positive electrode materials through a wet-chemical precipitation method, opening up a new high-value transformation path of "waste treatment with waste", while improving the recycling rate of agricultural waste and reducing the pollution of waste lithium batteries to the environment.

[0016] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further illustrated by the following examples.

[0018] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0019] Unless otherwise defined, the instruments, equipment and reagents used in the present invention are conventionally commercially available.

[0020] Example 1 A method for recycling waste lithium batteries based on crop straw comprises the following steps: Step 1, crush the straw through a 40-80 mesh sieve, dry to constant weight, react with 1%-2% dilute sulfuric acid at 60°C-140°C for 20-80 min, cool to room temperature and filter to obtain a filtrate, which is stored for later use, wherein the solid-liquid ratio of the straw to the dilute sulfuric acid is 1:10.

[0021] Step 2: Use saturated NaCl solution, FeSO4 solution, and Na2SO4 solution to discharge waste lithium iron phosphate batteries, waste lithium cobalt oxide batteries, and waste ternary lithium batteries for 8-16 hours, and then vacuum dry the treated waste lithium batteries at 80-100°C for 12-24 hours. Then, transfer the waste lithium batteries to the operating box, and obtain the positive electrode material by manual disassembly and separation. Transfer the positive electrode material to a tubular furnace and vacuum pyrolyze at 400-500°C for 1-3 hours to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and the positive electrode powder, and the positive electrode powder is sieved through a 120-180 mesh sieve.

[0022] Step 3: The filtrate in step 1 is mixed with the positive electrode powder in step 2 at a solid-liquid ratio of 15 g / L, and heated and stirred in an oil bath at 60° C. for 2 h.

[0023] Step 4, using an atomic absorption spectrometer to measure the solution of step 3, obtain the lithium content, and calculate the lithium recovery rate.

[0024] Step 5, adding saturated sodium carbonate solution to the filtrate in step 3, recovering the valuable metals in the form of precipitation, and then washing and drying to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for remanufacturing of lithium batteries.

[0025] Example 2 A method for recycling waste lithium batteries based on crop straw comprises the following steps: Step 1, crush the straw through a 40-80 mesh sieve, dry to constant weight, react with 1%-2% dilute sulfuric acid at 60°C-140°C for 20-80 min, cool to room temperature and filter to obtain a filtrate, which is stored for later use, wherein the solid-liquid ratio of the straw to the dilute sulfuric acid is 1:15.

[0026] Step 2: Use saturated NaCl solution, FeSO4 solution, and Na2SO4 solution to discharge waste lithium iron phosphate batteries, waste lithium cobalt oxide batteries, and waste ternary lithium batteries for 8-16 hours, and then vacuum dry the treated waste lithium batteries at 80-100°C for 12-24 hours. Then, transfer the waste lithium batteries to the operating box, and obtain the positive electrode material by manual disassembly and separation. Transfer the positive electrode material to a tubular furnace and vacuum pyrolyze at 400-500°C for 1-3 hours to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and the positive electrode powder, and the positive electrode powder is sieved through a 120-180 mesh sieve.

[0027] Step 3: The filtrate in step 1 is mixed with the positive electrode powder in step 2 at a solid-liquid ratio of 25 g / L, and heated and stirred in an oil bath at 70° C. for 2 h.

[0028] Step 4, using an atomic absorption spectrometer to measure the solution of step 3, obtain the lithium content, and calculate the lithium recovery rate.

[0029] Step 5, adding saturated sodium carbonate solution to the filtrate in step 3, recovering the valuable metals in the form of precipitation, and then washing and drying to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for remanufacturing of lithium batteries.

[0030] Example 3 A method for recycling waste lithium batteries based on crop straw comprises the following steps: Step 1, crush the straw through a 40-80 mesh sieve, dry to constant weight, react with 1%-2% dilute sulfuric acid at 60°C-140°C for 20-80 min, cool to room temperature and filter to obtain a filtrate, which is stored for later use, wherein the solid-liquid ratio of the straw to the dilute sulfuric acid is 1:20.

[0031] Step 2: Use saturated NaCl solution, FeSO4 solution, and Na2SO4 solution to discharge waste lithium iron phosphate batteries, waste lithium cobalt oxide batteries, and waste ternary lithium batteries for 8-16 hours, and then vacuum dry the treated waste lithium batteries at 80-100°C for 12-24 hours. Then, transfer the waste lithium batteries to the operating box, and obtain the positive electrode material by manual disassembly and separation. Transfer the positive electrode material to a tubular furnace and vacuum pyrolyze at 400-500°C for 1-3 hours to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and the positive electrode powder, and the positive electrode powder is sieved through a 120-180 mesh sieve.

[0032] Step 3: The filtrate in step 1 is mixed with the positive electrode powder in step 2 at a solid-liquid ratio of 30 g / L, and heated and stirred in an oil bath at 80° C. for 2 h.

[0033] Step 4, using an atomic absorption spectrometer to measure the solution of step 3, obtain the lithium content, and calculate the lithium recovery rate.

[0034] Step 5, adding saturated sodium carbonate solution to the filtrate in step 3, recovering the valuable metals in the form of precipitation, and then washing and drying to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for remanufacturing of lithium batteries.

[0035] Example 4 A method for recycling waste lithium batteries based on crop straw comprises the following steps: Step 1, crush the straw through a 40-80 mesh sieve, dry to constant weight, react with 1%-2% dilute sulfuric acid at 60°C-140°C for 20-80 min, cool to room temperature and filter to obtain a filtrate, which is stored for later use, wherein the solid-liquid ratio of the straw to the dilute sulfuric acid is 1:25.

[0036] Step 2: Use saturated NaCl solution, FeSO4 solution, and Na2SO4 solution to discharge waste lithium iron phosphate batteries, waste lithium cobalt oxide batteries, and waste ternary lithium batteries for 8-16 hours, and then vacuum dry the treated waste lithium batteries at 80-100°C for 12-24 hours. Then, transfer the waste lithium batteries to the operating box, and obtain the positive electrode material by manual disassembly and separation. Transfer the positive electrode material to a tubular furnace and vacuum pyrolyze at 400-500°C for 1-3 hours to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and the positive electrode powder, and the positive electrode powder is sieved through a 120-180 mesh sieve.

[0037] Step 3: The filtrate in step 1 is mixed with the positive electrode powder in step 2 at a solid-liquid ratio of 25 g / L, and heated and stirred in an oil bath at 90° C. for 2 h.

[0038] Step 4, using an atomic absorption spectrometer to measure the solution of step 3, obtain the lithium content, and calculate the lithium recovery rate.

[0039] Step 5, adding saturated sodium carbonate solution to the filtrate in step 3, recovering the valuable metals in the form of precipitation, and then washing and drying to obtain Li2CO3 powder. The recovered Li2CO3 powder can be used for remanufacturing of lithium batteries.

[0040] The recovery rate of lithium in this embodiment is shown in Table 1.

[0041] Table 1

[0042] It can be seen from the test data in Table 1 that, under the same reaction time, the lithium leaching rate increases with the increase of temperature, which significantly proves the effectiveness of this method.

[0043] Therefore, the present invention adopts the above-mentioned wet recovery method of waste lithium batteries based on crop straw, uses the reducing sugars and acids in the straw acid pretreatment hydrolyzate as reducing agents and leaching agents for the recovery of waste lithium batteries, and recovers lithium batteries through a wet-chemical precipitation method, which not only improves the recycling rate of agricultural waste, but also reduces the pollution of waste lithium batteries to the environment.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A wet recovery method for waste lithium batteries based on crop straw, characterized in that: The following steps are involved: Step 1, crush the crop straw through a 40-80 mesh sieve, dry to constant weight, and then react with 1%-2% dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, cool to room temperature and filter to obtain a filtrate, which is stored for later use; Step 2: Pretreatment of waste lithium battery positive electrode powder: ① Use saturated salt solution to discharge the waste lithium battery 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 Pyrolyze the cathode material in a vacuum at 400-500℃ for 1-3 h to burn off the organic binder. After the pyrolysis is completed, manually peel off the current collector and cathode powder, and pass the cathode powder through a 120-180 mesh sieve; Step 3, wet recovery of the positive electrode powder of waste lithium batteries: the filtrate in step 1 and the positive electrode powder in step 2 are mixed in proportion, heated and stirred in an oil bath, and after suction filtration, the filtrate and the filter residue are separated for later use; Step 4, determining the lithium content and calculating its recovery rate: using an atomic absorption spectrometer to measure the filtrate of step 3, obtaining the lithium content, and calculating the lithium recovery rate; Step 5, using chemical precipitation method to effectively recover lithium: adding saturated sodium carbonate solution to the filtrate in step 3, recovering lithium in the form of precipitation, and then washing and drying to obtain Li2CO3 powder.

2. The wet recovery method of 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 corn straw, rice straw, rape straw, and cotton straw.

3. The wet recovery method of waste lithium batteries based on crop straw according to claim 1, characterized in that: In step 1, the solid-liquid ratio of crop straw to dilute sulfuric acid is 1 g:10 ml-1 g:25 ml.

4. The wet recovery method of waste lithium batteries based on crop straw according to claim 1, characterized in that: In step 1, the reaction conditions of the crop straw and dilute sulfuric acid are a temperature of 60° C. to 140° C. and a time of 20 to 80 min.

5. The wet recovery method of 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.

6. The wet recovery method of waste lithium batteries based on crop straw according to claim 1, characterized in that: In step 3, the solid-to-liquid ratio of the positive electrode powder to the filtrate is 10-40 g / L.

7. The wet recovery method of waste lithium batteries based on crop straw according to claim 1, characterized in that: The reaction conditions of the oil bath in step 3 are a temperature of 50-100°C and a time of 50-120 min.

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