18650 battery pack 12v

　　Dry goods | Lithium-ion battery recycling technology is composed of positive and negative plates, binders, electrolytes and diaphragms. In industry, manufacturers mainly use lithium cobalt oxide, lithium manganese oxide, nickel-cobalt lithium manganese oxide ternary materials, and lithium iron phosphate as positive electrode materials for lithium-ion batteries, and natural graphite and artificial graphite as negative electrode active materials. Polyvinylidene fluoride (PVDF) is

　　Lithium-ion batteries are composed of positive and negative electrodes, binders, electrolytes, and separators. In industry, manufacturers mainly use lithium cobaltate, lithium manganate, nickel-cobalt lithium manganate ternary materials and lithium iron phosphate as positive electrode materials for lithium-ion batteries, and natural graphite and artificial graphite as negative electrode active materials. Polyvinylidene fluoride (PVDF) is a widely used cathode binder with high viscosity, good chemical stability and physical properties. Industrially produced lithium-ion batteries mainly use lithium hexafluorophosphate (LiPF6) and an organic solvent solution as the electrolyte, and use organic membranes, such as porous polyethylene (PE) and polypropylene (PP), as the separator of the battery. Lithium-ion batteries are generally regarded as environmentally friendly and pollution-free green batteries, but improper recycling of lithium-ion batteries will also cause pollution. Although lithium-ion batteries do not contain toxic heavy metals such as mercury, cadmium, and lead, the positive and negative electrode materials and electrolytes of the battery still have a relatively large impact on the environment and human body. If ordinary waste treatment methods are used to dispose of lithium-ion batteries (landfill, incineration, composting, etc.), metals such as cobalt, nickel, lithium, manganese, and various organic and inorganic compounds in the battery will cause metal pollution, organic pollution, and dust pollution. , Acid-base pollution. Lithium-ion electrolyte machine conversion products, such as LiPF6, lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), hydrofluoric acid (HF), etc., solvents and hydrolysis products such as ethylene glycol dimethyl ether ( DME), methanol, formic acid, etc. are all toxic substances. Therefore, waste lithium-ion batteries should be recycled to reduce the harm to the natural environment and human health.

　　1. Production and use of lithium-ion batteries

　　Lithium-ion batteries have the advantages of high energy density, high voltage, small self-discharge, good cycle performance, safe operation, etc., and are relatively friendly to the natural environment, so they are widely used in electronic products such as mobile phones, tablets, laptops, and digital cameras wait. In addition, lithium-ion batteries are widely used in energy storage power systems such as water power, thermal power, wind power and solar power, and have gradually become the best choice for power lithium batteries. The emergence of lithium iron phosphate batteries has promoted the development and application of lithium-ion batteries in the electric vehicle industry. With the gradual increase of people's demand for electronic products and the gradual acceleration of the upgrading of electronic products, and the impact of the rapid development of new energy vehicles, the global market demand for lithium-ion batteries is increasing, and the growth rate of battery production is increasing year by year. increase.

　　The huge demand for lithium-ion batteries in the market, on the one hand, will lead to a large number of waste batteries in the future. How to deal with these waste lithium-ion batteries to reduce their impact on the environment is an urgent problem to be solved; on the other hand, in order to cope with the huge market Demand, manufacturers have to produce a large number of lithium-ion batteries to supply the market. At present, the positive electrode materials for the production of lithium-ion batteries mainly include lithium cobalt oxide, lithium manganese oxide, nickel-cobalt lithium manganese oxide ternary materials and lithium iron phosphate, etc. Therefore, waste lithium-ion batteries contain more cobalt (Co), lithium (Li), nickel (Ni), manganese (Mn), copper (Cu), iron (Fe) and other metal resources, which contain a variety of rare metal resources, cobalt is a scarce strategic metal in my country, mainly imported meet rising demand. Part of the metal content in waste lithium-ion batteries is higher than that in natural ores. Therefore, in the case of increasing shortage of production resources, recycling waste batteries has certain economic value.

　　2. Lithium-ion battery recycling technology

　　The recycling process of used lithium-ion batteries mainly includes pretreatment, secondary treatment and advanced treatment. Since there is still some electricity left in the used battery, the pretreatment process includes deep discharge process, crushing, and physical separation; the purpose of the secondary treatment is to realize the complete separation of positive and negative active materials from the substrate, and heat treatment and organic solvent dissolution are commonly used. , lye dissolution method and electrolysis method to realize the complete separation of the two; advanced treatment mainly includes two processes of leaching and separation and purification to extract valuable metal materials. Classified by extraction process,

　　Battery recycling methods can be mainly divided into three categories: dry recycling, wet recycling and biological recycling.

　　1. Dry recycling

　　Dry recycling refers to the direct recovery of materials or valuable metals without using a medium such as a solution. Among them, the important methods used are physical separation method and high temperature pyrolysis method.

　　(1) Physical sorting method

　　The physical separation method refers to the disassembly and separation of batteries, and the battery components such as electrode active materials, current collectors and battery casings are crushed, sieved, magnetically separated, finely crushed and classified to obtain valuable high-content substances. . A method proposed by Shin et al. using sulfuric acid and hydrogen peroxide to recover Li and Co from lithium-ion battery waste liquid includes two processes: physical separation of metal-containing particles and chemical leaching. Among them, the physical separation process includes crushing, screening, magnetic separation, fine crushing and classification. In the experiment, a group of crushers with rotating and fixed blades were used for crushing, and sieves with different apertures were used to classify the crushed materials, and magnetic separation was used for further processing to prepare for the subsequent chemical leaching process.

　　Based on the grinding technology and water leaching process developed by Zhang et al., Lee et al., and Saeki et al., Shu et al. developed a new method for recovering cobalt and lithium from lithium-sulfur battery waste using mechanochemical methods. The method uses a planetary ball mill to co-grind lithium cobaltate (LiCoO2) and polyvinyl chloride (PVC) in air to mechanochemically form Co and lithium chloride (LiCl). Subsequently, the milled product was dispersed in water to extract chlorides. Grinding promotes mechanochemical reactions. The extraction yields of both Co and Li were improved with the grinding progress. 30 min of grinding resulted in the recovery of more than 90% Co and nearly 100% Li. At the same time, about 90% of the chlorine in the PVC samples had been converted to inorganic chlorides.

　　The physical separation method is relatively simple to operate, but it is not easy to completely separate lithium-ion batteries, and mechanical entrainment losses are prone to occur during screening and magnetic separation, making it difficult to achieve complete separation and recovery of metals.

　　(2) High temperature pyrolysis method

　　The high-temperature pyrolysis method refers to the decomposition of lithium-ion battery materials that have undergone preliminary separation treatment such as physical crushing, and the organic binder is removed to separate the constituent materials of the lithium-ion battery. At the same time, the metals and their compounds in lithium-ion batteries can be oxidized, reduced and decomposed, volatilized in the form of steam, and then collected by condensation and other methods.

　　When Lee et al. used waste lithium-ion batteries to prepare LiCoO2, they used a high-temperature pyrolysis method. Lee et al. first heat-treated the LIB sample in a muffle furnace at 100-150 °C for 1 h. Second, the heat-treated battery is shredded to release the electrode material. The samples were disassembled with a high-speed pulverizer specially designed for this study, and classified according to size, ranging from 1 to 50 mm. Then, two steps of heat treatment are carried out in the furnace, the first heat treatment is at 100-500°C for 30 minutes, the second heat treatment is at 300-500°C for 1 hour, and the electrode material is released from the current collector through vibration screening. Next, by firing at a temperature of 500-900° C. for 0.5-2 hours, the carbon and the binder are burned off, and the cathode active material LiCoO2 is obtained. Experimental data show that carbon and binder are burned off at 800°C.

　　The high-temperature pyrolysis treatment technology has simple process, convenient operation, fast reaction speed and high efficiency in high-temperature environment, and can effectively remove binders; and this method does not have high requirements on the composition of raw materials, and is more suitable for processing a large amount or more complex Battery. However, this method requires high equipment; during the treatment process, the organic matter of the battery decomposes and produces harmful gases, which is not friendly to the environment. New purification and recovery equipment must be added to absorb and purify harmful gases to prevent secondary pollution. Therefore, the processing cost of this method is high.

　　2. Wet recycling

　　The wet recycling process is to crush and dissolve the waste batteries, and then use appropriate chemical reagents to selectively separate the metal elements in the leaching solution to produce high-grade cobalt metal or lithium carbonate, etc., for direct recycling. Wet recycling is more suitable for the recovery of waste lithium-ion batteries with a relatively single chemical composition, and its equipment investment cost is low, which is suitable for the recovery of small and medium-sized waste lithium-ion batteries. Therefore, this method is widely used at present.

　　(1) Alkali-acid leaching method

　　Since the positive electrode material of lithium-ion batteries will not dissolve in lye, but the base aluminum foil will dissolve in lye, this method is often used to separate aluminum foil. Zhang Yang et al. used alkali leaching to remove aluminum in advance when recovering Co and Li in batteries, and then soaked in dilute acid solution to destroy the adhesion of organic matter and copper foil. However, the alkaline leaching method cannot completely remove PVDF, which has adverse effects on subsequent leaching.

　　Most of the positive electrode active materials in lithium-ion batteries can be dissolved in acid, so the pre-treated electrode materials can be leached with acid solution to realize the separation of active materials and current collectors, and then combined with the principle of neutralization reaction to target metals Precipitation and purification are carried out to achieve the purpose of recovering high-purity components.

　　The acid solution used by the pickling method includes traditional inorganic acids, including hydrochloric acid, sulfuric acid and nitric acid. However, because harmful gases such as chlorine (Cl2) and sulfur trioxide (SO3) often appear in the process of leaching with inorganic strong acids, researchers try to use organic acids to treat waste lithium-ion batteries, such as lemon acid, oxalic acid, malic acid, ascorbic acid, glycine, etc. Li et al. used hydrochloric acid to dissolve the recovered electrodes. Since the efficiency of the acid leaching process may be affected by the hydrogen ion (H+) concentration, temperature, reaction time and solid-liquid ratio (S/L), in order to optimize the operating conditions of the acid leaching process, an experiment was designed to investigate the reaction time, H+ concentration and temperature effects. The experimental data show that when the temperature is 80°C, the H+ concentration is 4mol/L, and the reaction time is 2h, the leaching efficiency is the highest, in which 97% of Li and 99% of Co in the electrode material are dissolved. Zhou Tao et al. used malic acid as leaching agent and hydrogen peroxide as reducing agent to reduce and leaching the positive electrode active material obtained by pretreatment, and studied the influence of different reaction conditions on the leaching rate of Li, Co, Ni, and Mn in malic acid leaching solution, so as to find out the best reaction conditions. Research data show that when the temperature is 80°C, the malic acid concentration is 1.2mol/L, the liquid-to-liquid volume ratio is 1.5%, the solid-to-liquid ratio is 40g/L, and the reaction time is 30min, the leaching efficiency of malic acid is the highest, among which Li, The leaching rates of Co, Ni and Mn reached 98.9%, 94.3%, 95.1% and 96.4%, respectively. However, compared with inorganic acids, the cost of leaching with organic acids is higher.

　　(2) Organic solvent extraction method

　　The organic solvent extraction method utilizes the principle of "similar compatibility", and uses a suitable organic solvent to physically dissolve the organic binder, thereby weakening the adhesion between the material and the foil and separating the two.

　　Contestabile et al. used N-methylpyrrolidone (NMP) to selectively separate the components in order to better recover the active material of the electrode when recycling lithium cobalt oxide batteries. NMP is a good solvent for PVDF (solubility about 200g/kg) and has a relatively high boiling point of about 200°C. Treatment of the active material with NMP at approximately 100 °C for 1 h effectively achieved the separation of the film from its support and thus the recovery of Cu in metallic form by simply filtering it out of the NMP (N-methylpyrrolidone) solution. and Al. Another benefit of this method is that the recovered metals, Cu and Al, can be directly reused after adequate cleaning. In addition, recovered NMP can be recycled. Because of its high solubility in PVDF, it can be reused many times. Zhang et al. used trifluoroacetic acid (TFA) to separate the cathode material from the aluminum foil when recycling cathode waste for lithium-ion batteries. The waste lithium-ion battery used in the experiment used polytetrafluoroethylene (PTFE) as an organic binder, and the effects of TFA concentration, liquid-solid ratio (L/S), reaction temperature and time on the separation efficiency of cathode materials and aluminum foil were systematically studied . The experimental results show that in the TFA solution with a mass fraction of 15, the liquid-solid ratio is 8.0mL/g, and the reaction temperature is 40℃, the cathode material can be completely separated under proper stirring for 180min.

　　The experimental conditions of using organic solvent extraction to separate materials and foils are relatively mild, but organic solvents are toxic to a certain extent and may be harmful to the health of operators. At the same time, because different manufacturers have different processes for making lithium-ion batteries, the binders they choose are different. Therefore, for different manufacturing processes, manufacturers must choose different organic solvents when recycling waste lithium-ion batteries. In addition, cost is also an important consideration with regard to large-scale recycling operations at an industrial level. Therefore, it is very important to choose a solvent with wide sources, reasonable price, low toxicity and harmlessness, and wide applicability.

　　(3) Ion exchange method

　　The ion exchange method refers to the separation and extraction of metals by using the different adsorption coefficients of ion exchange resins to the metal ion complexes to be collected. After acid leaching the electrode material, Wang Xiaofeng et al. added an appropriate amount of ammonia water to the solution to adjust the pH value of the solution, and reacted with metal ions in the solution to generate [Co(NH3)6]2+, [Ni(NH3) 6] 2+ and other complex ions, and continue to pass pure oxygen into the solution for oxidation. Then, ammonium sulfate solutions of different concentrations are used to repeatedly pass through the weakly acidic cation exchange resin to selectively elute the nickel complex and the trivalent cobalt ammonium complex on the ion exchange resin respectively. Finally, 5% H2SO4 solution was used to completely elute the cobalt complex, and at the same time, the cation exchange resin was regenerated, and the cobalt and nickel metals in the eluent were respectively recovered by using oxalate. The ion exchange method has a simple process and is relatively easy to operate.

　　3. Biological recycling

　　Mishra et al. used inorganic acids and acidophilic Thiobacillus ferrooxidans to leach metals from waste lithium-ion batteries, and used S and ferrous ions (Fe2+) to generate metabolites such as H2SO4 and Fe3+ in the leaching medium. These metabolites help dissolve metals in spent batteries. The study found that cobalt biodissolves faster than lithium. As the dissolution process proceeds, ferric ions react with the metals in the residue to precipitate, resulting in a decrease in the concentration of ferrous ions in the solution, and as the concentration of metals in the waste sample increases, cell growth is prevented and the dissolution rate becomes slower. slow. In addition, a higher solid/liquid ratio also affects the rate of metal dissolution. Zeng et al. used acidic Thiobacillus ferrooxidans to bioleave cobalt metal in waste lithium-ion batteries. Unlike Mishra et al., this study used copper as a catalyst to analyze the effect of copper ions on acidophilic Thiobacillus ferrooxidans on LiCoO2 bioleaching . The results showed that almost all of the cobalt (99.9%) entered the solution after 6 days of bioleaching at a Cu ion concentration of 0.75 g/L, whereas only 43.1% of Cobalt dissolves. In the presence of copper ions, the cobalt dissolution efficiency of spent Li-ion batteries is enhanced. In addition, Zeng et al. also studied the catalytic mechanism and explained the use of copper ions to dissolve cobalt. LiCoO2 and copper ions undergo a cation exchange reaction to form copper cobaltate (CuCo2O4) on the surface of the sample, which is easily dissolved by iron ions.

　　The bioleaching method has low cost, high recovery efficiency, less pollution and consumption, less impact on the environment, and microorganisms can be reused. However, the cultivation of high-efficiency microbial fungi is difficult, the treatment period is long, and the control of leaching conditions is the main problem of this method.

　　4. Combined recycling method

　　Waste lithium-ion battery recycling processes have their own advantages and disadvantages. At present, there have been researches on recycling methods that combine and optimize multiple processes in order to give full play to the advantages of various recycling methods and maximize economic benefits.