A method for leaching spent lithium battery cathode powder in a neutral environment by using intestinal flora

Abstract

The application discloses a method for leaching positive electrode powder of waste lithium battery in a neutral environment by using intestinal flora, and belongs to the technical field of resource recovery, and comprises the following steps: step 1: a pretreatment link, the pretreatment link comprises the following process links, and the links have no sequence: (1) preparation of battery powder, (2) acquisition of intestinal flora, and (3) preparation of culture medium; step 2: domestication of the flora; and step 3: leaching of valuable metals in the waste battery powder. The intestinal flora is applied to biological leaching of the positive electrode powder of the waste LIBs, breaks through the dependence of traditional strong acidophilic bacteria on extremely low pH conditions, and greatly reduces environmental hazards. In the application, inorganic acid does not need to be added, the pH of a reaction system is stably in a near-neutral range of 7.8-8.2, equipment loss caused by acid etching is reduced, reagent consumption in subsequent metal recovery and neutralization treatment is reduced, and remarkable economic benefits and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resource recycling, and particularly relates to a method for leaching spent lithium battery positive pole powder in a neutral environment by using intestinal flora. BACKGROUND

[0002] With the continuous growth of demand for power batteries and energy storage batteries, the application amount of lithium-ion batteries (LIBs) is increasing year by year, especially the high-energy-density batteries represented by lithium nickel cobalt manganese oxide batteries (NCM), lithium cobalt oxide batteries (LCO), lithium nickel cobalt aluminum oxide batteries (NCA) and lithium manganese oxide batteries (LMO) occupy an important position in the automobile and electronic industries. Since the spent batteries contain lithium, cobalt, nickel, manganese, aluminum and other metal elements, if the spent batteries are not properly treated after being discarded, not only the metal resources will be wasted, but also environmental pollution and health risks may be caused. Therefore, how to realize the efficient recovery of the spent battery positive pole material has become a technical problem to be solved at present.

[0003] Current recycling methods include direct regeneration, pyrometallurgy, and hydrometallurgy, etc. Direct regeneration method requires high integrity of battery materials, and has great process limitations; pyrometallurgy relies on high-temperature operation, has high energy consumption and emits toxic gases (Xu et al., 2023; Rajaeifar et al., 2021); hydrometallurgy requires the use of a large amount of chemical reagents, which can easily produce strong acidic or alkaline waste liquid, causing secondary pollution (Valdes et al., 2018). In recent years, bioleaching as an important branch of hydrometallurgy has attracted attention due to its low energy consumption and environmental friendliness. However, current research mainly focuses on a few strong acidophilic bacteria, whose metabolic products are single, and often need extremely low pH conditions to work. This not only leads to the generation of acidic wastewater, but also limits its application effect in complex battery systems. Although there have been attempts to use mild strains such as lactic acid bacteria and Gluconobacter oxydans to leach by secreting organic acids, these works still mainly use single strains, lacking the diversity and stability brought by the synergistic metabolism of microbial flora. The composition of waste LCO, NCM and NCA battery cathode materials is significantly different, and the dissolution mechanism of metal ions is different, which puts higher adaptability requirements on the adaptability and metabolic capacity of the leaching bacteria. Single strain is difficult to adapt to the complex reaction environment in multi-metal systems, so it is particularly important to explore new microbial resources.

[0004] Intestinal flora is a kind of microorganism community with wide sources and complex structure, and its metabolic network has high diversity (Bäckhed et al., 2004). Compared with traditional single strain, intestinal flora can produce multiple metabolic products at the same time, such as organic acids such as lactic acid, acetic acid, formic acid, and small molecules with reducing or chelating properties. These products can jointly act on the battery cathode material to accelerate the dissolution and release of metal elements. At the same time, intestinal flora has formed adaptability to environmental stress and metal ion toxicity in the long-term evolution process, so it still has stable metabolic activity in the system containing multiple metals and complex organic matter (Harris et al., 2020). In addition, the synergistic effect within the community can achieve effective leaching under near-neutral conditions, avoiding the defects of strong acidophilic bacteria relying on extreme environment. At present, the application of intestinal flora in waste battery field has not been reported.

[0005] Therefore, bioleaching based on intestinal flora provides a new idea for the recycling of waste LCO, NCM, NCA and other battery cathode materials. This method not only breaks through the limitations of traditional bioleaching relying on single strong acidophilic bacteria, but also relies on intestinal flora which has metabolic diversity, can improve the leaching efficiency while ensuring environmental friendliness, and provides a new technical path for green, low-carbon and efficient recycling of waste LIBs. SUMMARY

[0006] In view of the problems in the prior art, the present application aims to provide a method for leaching spent lithium battery cathode powder in a neutral environment by using intestinal flora, thereby improving the problems in the prior art, such as dependence on a few acidophilic bacteria species, single generation, need for an extreme acidic environment, and difficulty in adapting to complex battery systems. The method of the present application can achieve effective leaching under near-neutral conditions, providing a new technical means for microbial recovery of valuable metals.

[0007] The technical scheme provided by the present application comprises the following steps:

[0008] A method for leaching spent lithium battery cathode powder in a neutral environment by using intestinal flora, comprising the following steps:

[0009] Step 1: pretreatment link;

[0010] The pretreatment link comprises the following process links, which have no sequence: a. preparation of battery powder, b. acquisition of intestinal flora, c. preparation of culture medium;

[0011] a. Preparation of battery cathode powder:

[0012] The spent LIBs are fully immersed in a sodium chloride solution for constant voltage discharge treatment. Then, the discharged spent LIBs are dried at 40-60 DEG C under the condition of relative humidity ≤40%. After drying, the battery shell, separator, positive electrode sheet and negative electrode sheet are separated, the separated positive electrode sheet is cut into small pieces, and the pieces are placed in a sealed reaction kettle containing preheated N,N-dimethylformamide (DMF), and ultrasonic assisted treatment is started at the same time. The positive electrode sheet is taken out after soaking, washed with deionized water, and vacuum dried. Finally, the dried positive electrode sheet is crushed and ball milled, and sieved to obtain the battery cathode powder.

[0013] b. Acquisition of intestinal flora:

[0014] Under sterile conditions, fresh fecal samples are collected and stored at 4 DEG C. After gradient dilution of the samples with sterile normal saline, homogenate is prepared by vortex oscillation, and fecal residues are removed. The supernatant is inoculated into the intestinal flora special culture medium, and anaerobic culture is carried out at 37 DEG C to prepare bacteria preservation, which is stored in a-80 DEG C refrigerator.

[0015] c. Preparation of culture medium:

[0016] The intestinal flora basic culture medium is prepared, and the culture medium is a modified brain heart infusion broth, and the components are as follows: dehydrated beef heart infusion powder 5.0 g / L, sodium phosphate dibasic 2.5 g / L, sodium chloride 5.0 g / L, glucose 2.0 g / L, proteose peptone 10.0 g / L, dehydrated calf brain infusion powder 12.5 g / L, vitamin K 0.001 g / L, hematin 0.005 g / L, L-cystine 0.5 g / L, sodium lactate 10 mM, and sodium pyruvate 10 mM.

[0017] Step 2: acclimatization of bacterial community;

[0018] The battery positive electrode powder was added to the prepared intestinal flora basic medium to prepare an acclimatization medium. The intestinal flora was inoculated into the acclimatization medium and subjected to leaching acclimatization culture under aerobic conditions at 35-37°C. The OD value of the bacterial solution and the pH value of the medium were regularly monitored, and after 20-25 days of continuous acclimatization culture, the bacterial solution was collected in the late logarithmic growth phase, and the bacterial solution was washed with sterile normal saline. The washed bacterial solution was resuspended in sterile normal saline and inoculated into fresh intestinal flora basic medium without battery positive electrode powder, and subjected to propagation culture under the same aerobic culture conditions as the acclimatization stage. The OD value of the bacterial solution was monitored until it reached 1.0-1.2, and an intestinal flora with sufficient quantity and stable adaptation to the aerobic environment of the battery positive electrode powder was obtained, which was stored in a -80°C refrigerator. 600 600

[0019] Step 3: leaching of valuable metals from battery positive electrode powder;

[0020] The acclimatized and propagated intestinal flora obtained in Step 2 was inoculated into the intestinal flora basic medium of Step 1, c, and cultured at 37°C under aerobic conditions to activate the bacterial community. The battery positive electrode powder obtained in Step 1, a, was added to the intestinal flora basic medium of Step 1, c, to prepare a leaching medium, and the activated bacterial community was inoculated into the leaching medium to construct a bioleaching system. The bioleaching system was subjected to co-culture under aerobic conditions at 35-37°C, and the bacterial community metabolized and mediated the leaching of valuable metals from the battery positive electrode powder. Subsequently, the filtrate was obtained by filtering with a water-based microporous filter membrane with a pore size of 0.22 μm, and the metal ion concentration in the filtrate was determined and the leaching percentage was calculated.

[0021] The above method for leaching waste lithium battery positive electrode powder using intestinal flora in a neutral environment, wherein:

[0022] ​​In step 1 sub-step a, the waste LIBs are fully immersed in a sodium chloride solution with a mass concentration of 100 g / L for constant voltage discharge treatment, and the discharge duration is controlled to be 24-48 h. During the treatment, the electrode surface is stirred at a speed of 50 r / min every 8 h to ensure uniform reaction of the electrode surface. Finally, the voltage of the waste LIBs is stably reduced to 0-0.5 V, and the internal residual electric energy is completely released. Subsequently, the discharged waste LIBs are transferred to a forced air drying oven for gradient heat drying treatment under the conditions of 40-60°C and a relative humidity of ≤40%. First, the temperature is set to 40°C for drying for 22-24 h, and then the temperature is increased to 55°C for further drying for 24-36 h. The oven is kept ventilated throughout the process to efficiently remove the free water and crystal water attached to the pores inside the battery and the surface of the battery, thereby significantly reducing the safety hazards such as short circuit and thermal runaway caused by residual electric energy or moisture during the subsequent disassembly and crushing process. After drying, the battery shell, separator, positive electrode sheet and negative electrode sheet are separated in sequence using a disassembly device with insulation protection. The separated positive electrode sheet is cut into small pieces with a size of 5 cm x 5 cm or less, and then placed in a sealed reaction kettle containing preheated DMF at 60°C. At the same time, ultrasonic auxiliary treatment (power: 100-150 W, frequency: 40-60 kHz) is started. The positive electrode sheet is soaked at a constant temperature for 20-40 min. Ultrasonic vibration can produce a micro-jet effect, accelerate the separation of the binder and the positive electrode matrix, improve the dissolution efficiency and reduce the residual binder. After soaking, the positive electrode sheet is taken out and placed in deionized water for ultrasonic rinsing. Each ultrasonic treatment lasts for 10-15 min, and the rinsing process is repeated for 2-3 times until the pH of the washing liquid is stabilized at 7.0-7.5 (close to neutral), thereby ensuring that the residual DMF is completely removed. The washed positive electrode sheet is again placed in an oven for vacuum drying at 60-70°C for 8-12 h until the mass of the electrode sheet is constant and the water content is ≤0.5%. Finally, the dried positive electrode sheet is coarsely crushed to a particle size of ≤5 mm by a jaw crusher, and then transferred to a planetary ball mill for fine grinding. The ball-to-material ratio is 8:1, the rotation speed is 300-400 r / min, and the grinding time is 1-2 h. After grinding, the product is sieved through a 100-mesh standard sieve, and the undersize product is collected as the uniformly dispersed battery positive electrode powder. The powder is sealed and stored in a light-proof and dry (relative humidity ≤30%) environment to avoid moisture oxidation for subsequent use in the bioleaching process.

[0023] In step 1 sub-step b, under sterile conditions, fresh fecal samples are collected from healthy subjects and immediately placed in sterile sampling tubes and stored at 4°C. After gradient dilution of the samples with sterile normal saline, the homogenate is prepared by vortexing for 10-15 min to remove the fecal residue. The supernatant is inoculated into an intestinal flora special culture medium, and anaerobic culture is performed at 37°C for 24-48 h. Finally, the bacterial preservation is prepared and stored in a -80°C refrigerator for subsequent use.

[0024] In step 1c, the concentrations of vitamin K and heme are low, so a stock solution of a certain concentration should be prepared first to reduce weighing errors. Vitamin K is insoluble in water and should be dissolved in Tween-80 before preparing the culture medium. L-cysteine ​​has limited solubility under acidic conditions and should be dissolved in a small amount of 4M NaOH before being added to the culture medium.

[0025] In step 2, the battery positive electrode powder from step 1a is added to the intestinal flora basal culture medium prepared in step 1c to prepare an acclimatization culture medium. The intestinal flora from step 1b is inoculated into the acclimatization culture medium at an inoculation rate of 5%–10%, and then subjected to leaching acclimatization culture in a constant temperature and humidity incubator at 35℃–37℃ under aerobic conditions; simultaneously, the OD of the bacterial solution is monitored periodically. 600 The bacterial growth rate (OD) was measured once daily (once a day) and the pH of the culture medium was monitored. After 20–25 days of continuous acclimatization culture, when the bacterial culture was in the late logarithmic growth phase, the bacterial culture precipitate in the acclimatization culture medium was collected by centrifugation (centrifugation speed 4000 r / min–5000 r / min, centrifugation time 10 min–15 min). The precipitate was washed 2–3 times with sterile physiological saline to remove residual culture medium components and battery positive electrode powder particles. Subsequently, the washed bacterial culture precipitate was resuspended in sterile physiological saline and inoculated into fresh intestinal flora basal culture medium without battery positive electrode powder at an inoculation rate of 5%–8%. Propagation culture was carried out under the same aerobic culture conditions (35℃–37℃) as in the acclimatization stage, and the OD of the bacterial culture was monitored during the process. 600 The value was increased until it reached 1.0–1.2 (early stage of stabilization), ultimately obtaining a sufficient quantity of gut microbiota that could stably adapt to the aerobic environment of the battery cathode powder. Finally, a microbial preservative was prepared and stored at -80°C for later use.

[0026] In step 3, the domesticated and propagated intestinal flora cryopreserved material obtained in step 2 is inoculated into the intestinal flora basal culture medium of step 1c at an inoculation rate of 5% to 8%, and cultured at 37°C under aerobic conditions (stationary in a constant temperature and humidity shaker) for 12 to 16 hours. During the culture period, the OD of the bacterial solution is monitored in real time by turbidimetric method. 600 The bacterial flora is activated when its pH reaches approximately 1.2 (in the logarithmic growth phase) to eliminate the inhibitory effect of low-temperature preservation or preservation solution on bacterial metabolism and enhance its metabolic activity after inoculation. The battery cathode powder obtained in step 1(a) is added to the intestinal flora basal culture medium from step 1(c) to achieve a powder concentration of 2 g / L–5 g / L (consistent with the powder concentration during the acclimatization stage in step 2) to prepare the leaching medium. The activated bacterial flora is then inoculated into this leaching medium at an inoculation rate of 10%–15% to construct a bioleaching system. This bioleaching system is co-cultured at 35°C–37°C in an aerobic environment, with regular monitoring of the pH and OD of the bacterial culture.600 The pH value is measured by a pH meter, and then filtered by a water-based microporous filter with a pore size of 0.22 μm to obtain a filtrate, and the concentration of metal ions in the filtrate is measured and the leaching percentage is calculated.

[0027] The core of the present application is to provide a method for leaching valuable metals from waste lithium battery cathode by using intestinal flora, which can be widely applied to resource recycling of NCM, NCA and LCO type waste battery cathode powder. The method breaks through the dependence of traditional bioleaching on single acidophilic bacteria, and realizes efficient leaching in near neutral environment by virtue of the metabolic diversity of intestinal flora, which has the advantages of low energy consumption, no secondary pollution, and is suitable for various complex battery systems.

[0028] Compared with the prior art, the method has the following beneficial effects:

[0029] 1. The intestinal flora is applied to the bioleaching of waste LIBs cathode powder, which breaks through the dependence of traditional strong acidophilic bacteria on extremely low pH conditions, greatly reduces environmental hazards, and compared with single strain, the intestinal flora has metabolic diversity and colony stability, and can better adapt to the complex reaction environment of multi-metal system.

[0030] 2. No inorganic acid is added, the pH of the reaction system is stable in the near neutral range of 7.8-8.2, which not only reduces the equipment loss caused by acid etching, but also reduces the reagent consumption of subsequent metal recovery and neutralization treatment, and has significant economic and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the method flowchart of the present application for leaching waste lithium battery cathode powder in a neutral environment by using intestinal flora.

[0032] Figure 2 is the morphology (a) of NCM battery cathode powder before reaction and the morphology (b) of secondary minerals generated after reaction in Example 1 of the present application; wherein 01 to 08 are different detection points.

[0033] Figure 3 is the energy dispersive X-ray spectrum in Example 1 of the present application; wherein a, b, c, d are the initial NCM energy dispersive X-ray spectra corresponding to 01 to 04, e, f, g, h are the secondary mineral energy dispersive X-ray spectra corresponding to 05 to 08. DETAILED DESCRIPTION

[0034] The application provides a method for leaching spent lithium battery cathode powder in a neutral environment by using intestinal flora. The spent lithium battery is selected from high-energy-density batteries such as lithium nickel cobalt manganese oxide (NCM) batteries, lithium cobalt oxide (LCO) batteries, lithium nickel cobalt aluminum oxide (NCA) batteries, lithium manganese oxide (LMO) batteries, lithium-ion batteries (LIBs) and the like.

[0035] Embodiment 1

[0036] A method for leaching spent NCM battery cathode powder in a neutral environment by using intestinal flora, as shown in the specific operation steps are as follows: Figure 1

[0037] Step 1: pretreatment link;

[0038] The pretreatment link includes the following process links, and each link has no sequence: a. preparation of battery powder, b. acquisition of intestinal flora, c. preparation of culture medium;

[0039] a. Preparation of battery cathode powder:

[0040] ​The waste NCM523 battery is immersed in a sodium chloride solution with a mass concentration of 100 g / L for constant voltage discharge treatment. The discharge duration is controlled for 24-48 h, and the electrode surface is stirred at a speed of 50 r / min every 8 h to ensure uniform reaction. Finally, the voltage of the waste NCM battery is stably reduced to 0-0.5 V, and the internal residual electric energy is completely released. Then, the discharged waste NCM soft package is transferred to a blast drying oven for gradient heat drying treatment under the conditions of 40-60°C and a relative humidity of ≤40%. First, the temperature is increased to 40°C for drying for 24 h, and then the temperature is increased to 55°C for continuous drying for 24-36 h. The box is ventilated throughout the process to efficiently remove the free water and crystal water attached to the pores and surface of the battery, thereby significantly reducing the safety hazards such as short circuit and thermal runaway caused by residual electric energy or moisture during the subsequent disassembly and crushing process. After drying, the battery shell, separator, positive electrode sheet and negative electrode sheet are separated in sequence using disassembly equipment with insulation protection. The separated positive electrode sheet is cut into small pieces with a size of 5 cm x 5 cm or less, and is placed in a sealed reaction kettle containing 60°C preheated DMF. At the same time, ultrasonic assisted treatment is started (power 100-150 W, frequency 40-60 kHz) for constant temperature soaking for 30 min. Ultrasonic vibration can produce a microjet effect, accelerate the separation of the binder and the positive electrode matrix, improve the dissolution efficiency and reduce the residual binder. After soaking, the positive electrode sheet is taken out and placed in deionized water for ultrasonic rinsing, with each ultrasonic time being 10-15 min, and the rinsing is repeated for 2-3 times until the pH of the washing liquid is stable at 7.0-7.5 (close to neutral), so as to ensure that the residual DMF is completely removed. The washed positive electrode sheet is placed in an oven again for vacuum drying at 60-70°C for 8-12 h until the mass of the electrode sheet is constant and the water content is ≤0.5%. Finally, the dried positive electrode sheet is coarsely crushed to a particle size of ≤5 mm by a jaw crusher, and then is finely ground in a planetary ball mill with a ball-to-material ratio of 8:1 and a rotation speed of 300-400 r / min for 2 h. After grinding, the product is sieved through a 100-mesh standard sieve, and the undersize product is collected as the uniformly dispersed waste battery positive electrode powder. The powder is sealed and stored in a light-proof and dry (relative humidity ≤30%) environment to avoid oxidation caused by moisture, for use in subsequent bioleaching procedures.

[0041] The concentration of metal elements in the obtained positive electrode powder of the battery was analyzed using a chemical digestion method: 0.05 g of the powder was taken, 4.0 mL of a digestion solution (HNO3:HClO4:HF=2:1:2, v / v / v) was added, and the mixture was heated to 220°C in a crucible on an electric heating plate for digestion. After cooling, the solution was diluted to 10.0 mL with 1% dilute nitric acid, and the concentration of metal ions in the digestion solution was measured using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The lithium content in the waste NCM battery powder was calculated to be 37.2 mg / g, the nickel content was 289.7 mg / g, the cobalt content was 109.0 mg / g, and the manganese content was 149.2 mg / g.

[0042] b. Acquisition of intestinal flora:

[0043] Under sterile conditions, fresh fecal samples of 5g-10g from healthy adult subjects with informed consent were collected and immediately placed in sterile sampling tubes pre-filled with anaerobic transport solution, and transported to the laboratory at 4°C. The samples were diluted 1:10 (w / v) with pre-reduced sterile physiological saline in an anaerobic workstation, and 10 -1 to 10 -6 serial dilutions were prepared by ten-fold gradient dilution method. Each dilution was vortexed at 3000 rpm for 10-15 min, then passed through a 200-mesh sterile nylon filter to remove residues, and the filtrate was collected. 200 μL of the filtrate was inoculated into the intestinal flora base medium, and then placed in a 37°C anaerobic incubator for 24-48 h of culture. The logarithmic growth phase bacterial solution was mixed with sterile cryoprotectant containing 20% glycerol and 0.1% cysteine hydrochloride at a volume ratio of 1:1, and then aliquoted into cryogenic tubes. After programmed cooling (first reduced to -40°C at -1°C / min, then reduced to -80°C at -10°C / min), the samples were stored in a -80°C ultra-low temperature freezer.

[0044] c. Preparation of culture medium:

[0045] The intestinal flora base medium is prepared by using a modified brain heart infusion broth, and the components are as follows: dehydrated beef heart infusion powder 5.0 g / L, sodium phosphate dibasic 2.5 g / L, sodium chloride 5.0 g / L, glucose 2.0 g / L, proteose peptone 10.0 g / L, dehydrated calf brain infusion powder 12.5 g / L, vitamin K 0.001 g / L, hematin 0.005 g / L, L-cystine 0.5 g / L, sodium lactate 10 mM, sodium pyruvate 10 mM. The concentrations of vitamin K and hematin are relatively low, and a certain content of stock solution should be prepared in advance to reduce the weighing error. Vitamin K is insoluble in water and should be dissolved in Tween-80 before the preparation of the medium. L-cysteine is limitedly soluble in an acidic condition and should be dissolved in a small amount of 4M NaOH before being added to the medium.

[0046] Step 2: domesticating the intestinal flora to adapt to the NCM powder;

[0047] The intestinal flora base medium obtained in step 1 link c is gradually added with the battery positive electrode powder of step 1 link a, and the initial concentration is 0.5 g / L, and then the concentration is gradually increased to 5 g / L by increasing by 0.5 g / L at each stage, to prepare a domestication medium. The intestinal flora obtained in step 1 link b is inoculated into the domestication medium at an inoculation amount of 5% to 10%, and leaching domestication culture is carried out in an incubator under aerobic conditions at 35°C to 37°C. The OD 600 value and the pH value of the medium are monitored every 24 hours during the culture; after 22 days of continuous domestication, when the bacteria enter the late logarithmic growth phase, the bacteria are collected by centrifugation at a speed of 4000 r / min to 5000 r / min for 10 min to 15 min, washed with sterile normal saline for 2 to 3 times to completely remove the residual medium components and battery positive electrode powder particles; the washed bacteria are resuspended in sterile normal saline, and inoculated into fresh intestinal flora base medium without battery positive electrode powder at an inoculation amount of 5% to 8%, and expanded under the same aerobic conditions, and the OD 600 value is monitored to be within the range of 1.0 to 1.2, that is, to reach the early stationary phase, so as to obtain sufficient intestinal flora with stable adaptability to the battery positive electrode powder environment. Finally, the bacteria are mixed with a cryoprotectant at a volume ratio of 1:1, and stored in a -80°C ultra-low temperature refrigerator after being divided and cooled, for subsequent experiments.

[0048] Step 3: leaching valuable metals from the battery positive electrode powder;

[0049] The intestinal flora obtained in step 2 is activated before the leaching experiment: the bacteria preserved at low temperature are inoculated into the intestinal flora base medium of step 1 link c and cultured for 6 hours to 10 hours. During this period, the growth state is monitored by turbidimetry, and when the OD 600The logarithmic growth phase is reached at about 1.2, and then the leaching experiment is performed. 200 mL of intestinal flora basic medium is added to a 250 mL conical flask, and the activated intestinal flora is inoculated into the medium with a controlled inoculation amount of 10%-15% v / v. The positive electrode powder of the battery is added, and the solid-liquid ratio is controlled at 2 g / L. When the leaching experiment starts, it is recorded as 0 h, and it is placed in a 37°C incubator for static culture. The leaching experiment lasts for 22 days, and samples are taken every 1 day. The pH value changes in the range of 7.8-8.2 during the sampling process. The sample is filtered using a 0.22 μm water filter, and the concentrations of lithium ions, cobalt ions and nickel ions in the leaching solution are measured by ICP-OES. Then the leaching percentage is calculated. After 22 days, the percentage content of lithium ions in the leaching solution can reach 52.3%, the percentage content of nickel ions can reach 42.2%, the percentage content of cobalt ions is only 7.4%, and the percentage content of manganese ions is only 0.1%. In the absence of intestinal flora, the percentage content of lithium ions in the medium is 16.8%, the percentage content of nickel ions is 10.8%, the percentage content of cobalt ions is 10.4%, and the percentage content of manganese ions is 4.0%. During this process, the leaching percentage of manganese is the highest at about 7.8% on the 4th day, and then decreases. The results show that this kind of bacteria has selective leaching effect on lithium, nickel, cobalt and manganese in the positive electrode powder of waste NCM battery. At the same time, solid phase characterization tests show that cobalt / manganese secondary minerals are produced in the system Figure 2 、 Figure 3 ).

[0050] Example 2

[0051] A method for leaching waste LCO battery positive electrode powder in a neutral environment using intestinal flora, as shown in Figure 1 , the specific operation steps are as follows:

[0052] Step 1: As in step 1 part a of example 1, prepare the LCO battery positive electrode powder for bioleaching; as in step 1 part c of example 1, prepare the modified brain heart infusion broth medium (i.e. intestinal flora basic medium) for bioleaching;

[0053] Step 2: As in step 2 of example 1, acclimate the intestinal flora adapted to the LCO battery positive electrode powder;

[0054] Step 3: As in step 3 of example 1, leach the valuable metals in the LCO battery positive electrode powder.

[0055] The results of the intestinal flora leaching of the waste LCO battery cathode powder in Example 2 are as follows: the lithium content in the LCO battery cathode powder prepared in Step 1 is 34.5 mg / g, and the cobalt content is 550 mg / g; under the condition of 5 g / L for 14 days, the percentage content of lithium ions in the leaching solution can reach 42.6%, and the percentage content of cobalt ions can reach 23.6%, which shows that the intestinal flora has leaching effect on lithium and cobalt in the waste LCO battery cathode powder.

[0056] Example 3

[0057] A method for leaching waste NCA battery cathode powder by intestinal flora in a neutral environment, as shown in Figure 1 , the specific operation steps are as follows:

[0058] Step 1: as step 1 part a of Example 1, prepare the NCA battery cathode powder for bioleaching; as step 1 part c of Example 1, prepare the modified brain heart infusion broth medium for bioleaching;

[0059] Step 2: as step 2 of Example 1, domesticate the intestinal flora adapted to the NCA battery cathode powder;

[0060] Step 3: as step 3 of Example 1, leach the valuable metals in the NCA battery cathode powder.

[0061] The results of the intestinal flora leaching of the waste NCA battery cathode powder in Example 3 are as follows: the lithium content in the NCA battery cathode powder prepared in Step 1 is 34.1 mg / g, the nickel content is 355.0 mg / g, the cobalt content is 26.8 mg / g, and the aluminum content is 21.8 mg / g; under the condition of 5 g / L for 14 days, the percentage content of lithium ions in the leaching solution can reach 29.3%, the percentage content of nickel ions can reach 8.9%, the percentage content of cobalt ions can reach 27.1%, and the percentage content of aluminum ions is only 1.4%, which shows that the intestinal flora has selective leaching effect on lithium, nickel and cobalt in the waste NCA battery cathode powder. The above results show that the intestinal flora has material dependence on the leaching of waste batteries.

[0062] Example 4

[0063] A method for leaching waste LMO battery cathode powder by intestinal flora in a neutral environment, as shown in Figure 1 , the specific operation steps are as follows:

[0064] Step 1: as step 1 part a of Example 1, prepare the LMO battery cathode powder for bioleaching; as step 1 part c of Example 1, prepare the modified brain heart infusion broth medium for bioleaching;

[0065] Step 2: The gut flora adapted to the LMO battery cathode powder was domesticated as in Example 1, Step 2.

[0066] Step 3: The valuable metals in the LMO battery cathode powder were leached as in Example 1, Step 3.

[0067] The results of the gut flora leaching of the waste LMO battery cathode powder in Example 4 are as follows: the lithium content in the LMO battery cathode powder prepared in Step 1 was calculated to be 36.7 mg / g, and the manganese content was 598.4 mg / g; under the conditions of 5 g / L for 14 days, the percentage of lithium ions in the leachate was as high as 67.8%, while the percentage of manganese ions was 2.1%, indicating that the gut flora had a selective leaching effect on lithium in the waste NCA battery cathode powder. As in Example 1, solid-phase characterization showed that cobalt / manganese formed secondary minerals.

Claims

1. A method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment, characterized in that, Includes the following steps: Step 1: Pre-processing; The pretreatment process includes the following steps, which are in no particular order: a. preparation of battery powder, b. acquisition of intestinal flora, c. preparation of culture medium; a. Preparation of battery positive electrode powder: Waste LIBs were immersed in a sodium chloride solution for constant voltage discharge treatment. After discharge, the waste LIBs were dried at 40℃~60℃ and relative humidity ≤40%. After drying, they were disassembled, and their positive electrode sheets were placed in a sealed reactor containing preheated N,N-dimethylformamide for constant temperature immersion. After immersion, the positive electrode sheets were removed, washed with deionized water, and vacuum dried. Finally, they were crushed, ball-milled, and sieved to obtain battery positive electrode powder. b. Acquisition of gut microbiota: Under aseptic conditions, fresh fecal samples were collected, and after serial dilution with sterile physiological saline, the samples were vortexed to prepare homogenates. Fecal residues were removed, and the supernatant was inoculated into a special culture medium for intestinal flora. The samples were then anaerobically cultured at 37°C, and the culture medium was prepared and stored in a -80°C refrigerator. c. Preparation of culture medium: A basic culture medium for intestinal flora was prepared, with the following components: 5.0 g / L dehydrated bovine heart extract, 2.5 g / L disodium hydrogen phosphate, 5.0 g / L sodium chloride, 2.0 g / L glucose, 10.0 g / L peptone, 12.5 g / L dehydrated calf brain extract, 0.001 g / L vitamin K, 0.005 g / L heme, 0.5 g / L L-cysteine, 10 mM sodium lactate, and 10 mM sodium pyruvate. Step 2: Acclimatization of the microbial community; Battery positive electrode powder was added to the intestinal flora basal culture medium to prepare an acclimatization medium. Intestinal flora were inoculated into the acclimatization medium and subjected to leaching acclimatization culture at 35℃–37℃ under aerobic conditions. When the bacterial culture was in the late logarithmic growth phase, the bacterial precipitate was collected from the acclimatization medium and washed with sterile physiological saline. The washed bacterial precipitate was resuspended in sterile physiological saline and inoculated into fresh intestinal flora basal culture medium without battery positive electrode powder. Propagation culture was carried out under the same aerobic conditions as the acclimatization stage, and the OD of the bacterial culture was monitored. 600 The value was kept until it reached 1.0 to 1.2 to obtain the intestinal flora, and then stored in a refrigerator at -80°C. Step 3: Leaching out valuable metals from the battery's positive electrode powder; The cryopreserved intestinal flora obtained in step 2 after domestication and propagation was inoculated into the intestinal flora basal culture medium and cultured at 37°C under aerobic conditions to complete the activation of the flora. Battery cathode powder was added to the intestinal flora basal culture medium to prepare a leaching medium. The activated flora was then inoculated into the leaching medium to construct a bioleaching system. The bioleaching system was co-cultured at 35°C to 37°C under aerobic conditions. The flora metabolized and mediated the leaching of valuable metals from the battery cathode powder. The mixture was then filtered to obtain the filtrate. The concentration of metal ions in the filtrate was measured and the leaching percentage was calculated.

2. The method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment according to claim 1, characterized in that, In step 1a, the discharged waste LIBs are transferred to a forced-air drying oven and subjected to gradient thermal drying at 40℃~60℃ and relative humidity ≤40%: first, drying at 40℃ for 22h~24h, then raising the temperature to 55℃ and continuing drying for 24h~36h, with ventilation maintained throughout the process; after drying, the LIBs are disassembled and their positive electrode plates are placed in a sealed reactor containing preheated N,N-dimethylformamide, while ultrasonic assisted treatment is started at a power of 100W~150W and a frequency of 40kHz~60kHz, and the plates are soaked at a constant temperature for 20min~40min.

3. The method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment according to claim 1, characterized in that, In step 1a, the dried positive electrode sheet is first coarsely crushed to a particle size ≤5mm by a jaw crusher, and then finely ground in a planetary ball mill with a ball-to-material ratio of 8:1, a rotation speed of 300r / min~400r / min, and a grinding time of 1h~2h. After grinding, it is sieved through a 100-mesh standard inspection sieve, and the product under the sieve is the uniformly dispersed battery positive electrode powder.

4. The method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment according to claim 1, characterized in that, In step 1b, the sample is serially diluted with sterile physiological saline and vortexed for 10 to 15 minutes to prepare a homogenate to remove fecal residue. The supernatant is then inoculated into a special intestinal flora culture medium and anaerobically cultured at 37°C for 24 to 48 hours. Finally, a bacterial culture medium is prepared and stored in a -80°C refrigerator.

5. The method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment according to claim 1, characterized in that, In step 2, the intestinal flora from step 1b is inoculated into the acclimatization culture medium at an inoculation rate of 5%–10%, and then subjected to leaching and acclimatization culture in a constant temperature and humidity incubator at 35℃–37℃ under aerobic conditions; simultaneously, the OD of the bacterial solution is monitored periodically. 600 The pH of the culture medium was measured. After acclimatization culture for 20–25 days, when the bacterial culture was in the late logarithmic growth phase, the bacterial precipitate in the acclimatization culture medium was collected by centrifugation and washed 2–3 times with sterile physiological saline to remove residual culture medium components and battery positive electrode powder particles. Subsequently, the washed bacterial precipitate was resuspended in sterile physiological saline and inoculated into fresh intestinal flora basal culture medium without battery positive electrode powder at an inoculation rate of 5%–8%. Propagation culture was carried out under the same aerobic culture conditions as in the acclimatization stage, and the OD of the bacterial culture was monitored during the process. 600 The value is maintained until it reaches 1.0 to 1.2, ultimately obtaining a sufficient quantity of gut microbiota that can stably adapt to the aerobic environment of the battery cathode powder.

6. The method for leaching waste lithium battery cathode powder using intestinal flora under a neutral environment according to claim 1, characterized in that, In step 3, the cryopreserved intestinal flora that has been domesticated and propagated is inoculated into the intestinal flora basal culture medium at an inoculation rate of 5% to 8%, and cultured at 37°C under aerobic conditions for 12 to 16 hours. During the culture period, the OD of the bacterial culture is monitored. 600 Once the bacterial community reaches the logarithmic growth phase, its activation is complete. Battery positive electrode powder is added to the intestinal flora basal culture medium to achieve a powder concentration of 2 g / L–5 g / L to prepare the leaching medium. The activated bacterial community is then inoculated into this leaching medium at an inoculum concentration of 10%–15% to construct a bioleaching system. This bioleaching system is co-cultured at 35℃–37℃ under aerobic conditions, with regular monitoring of the system's pH and bacterial OD values. 600 The co-culture time was 14–22 days to ensure that the microbial community fully metabolized and mediated the leaching of valuable metals from the battery cathode powder. During the leaching experiment, pH changes were monitored, and the values ​​were in the range of 7.8–8.2.

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