AA rechargeable battery

release time:2024-06-18 Hits: Popular:AG11 battery

Analysis of recycling and processing technology of AA rechargeable battery

AA rechargeable battery are composed of positive and negative electrodes, binders, electrolytes and diaphragms. In industry, manufacturers mainly use lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese oxide ternary materials and lithium iron phosphate as positive electrode materials of AA rechargeable battery, and natural graphite and artificial graphite as negative electrode active materials. Polyvinylidene fluoride (PVDF) is a widely used positive electrode binder with high viscosity and good chemical stability and physical properties. Industrially produced AA rechargeable battery mainly use electrolyte lithium hexafluorophosphate (LiPF6) and organic solvents as electrolytes, and use organic membranes such as porous polyethylene (PE) and polypropylene (PP) polymers as battery diaphragms. AA rechargeable battery are generally considered to be environmentally friendly and pollution-free green batteries, but improper recycling of AA rechargeable battery will also cause pollution. Although AA rechargeable battery do not contain toxic heavy metals such as mercury, cadmium and lead, the positive and negative electrode materials and electrolytes of the batteries still have a great impact on the environment and human body. If AA rechargeable battery are treated by ordinary garbage disposal methods (landfill, incineration, composting, etc.), metals such as cobalt, nickel, lithium, and manganese in the batteries, as well as various organic and inorganic compounds, will cause metal pollution, organic pollution, dust pollution, and 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 AA rechargeable battery need to be recycled to reduce the harm to the natural environment and human health. 1. Production and use of AA rechargeable battery AA rechargeable battery have the advantages of high energy density, high voltage, low self-discharge, good cycle performance, safe operation, and are relatively friendly to the natural environment. Therefore, they are widely used in electronic products such as mobile phones, tablets, laptops, and digital cameras. In addition, AA rechargeable battery are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power, and are gradually becoming the best choice for power batteries. The emergence of lithium iron phosphate batteries has promoted the development and application of AA rechargeable battery in the electric vehicle industry. With the increasing demand for electronic products and the accelerated pace of electronic product replacement, and the impact of the rapid development of new energy vehicles, the global market demand for AA rechargeable battery is increasing, and the growth rate of battery production is increasing year by year. The huge market demand for AA rechargeable battery will lead to a large number of waste batteries in the future. How to deal with these waste AA rechargeable battery 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 need to produce a large number of AA rechargeable battery to supply the market. At present, the positive electrode materials for the production of AA rechargeable battery mainly include lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese oxide ternary materials and lithium iron phosphate. Therefore, waste AA rechargeable battery contain more cobalt (Co), lithium (Li), nickel (Ni), manganese (Mn), copper (Cu), iron (Fe) and other metal resources, including a variety of rare metal resources. Cobalt is a scarce strategic metal in my country, and it is mainly imported to meet the growing demand. The content of some metals in waste AA rechargeable battery is higher than that in natural ores. Therefore, in the case of increasing shortage of production resources, recycling and processing of waste batteries has certain economic value. 2. Lithium-ion battery recycling and processing technology The recycling and processing process of waste AA rechargeable battery mainly includes pretreatment, secondary treatment and deep treatment. Since there is still some electricity left in the waste batteries, the pretreatment process includes deep discharge process, crushing, and physical sorting; the purpose of secondary treatment is to achieve complete separation of positive and negative active materials from the substrate. Commonly used heat treatment, organic solvent dissolution, alkali solution dissolution and electrolysis are used to achieve complete separation of the two; deep treatment mainly includes leaching and separation and purification to extract valuable metal materials. According to the extraction process classification, battery recycling methods can be mainly divided into three major technologies: dry recovery, wet recovery and biological recovery. 1. Dry recovery Dry recovery refers to the direct recovery of materials or valuable metals without using media such as solutions. Among them, the main methods used are physical sorting and high-temperature pyrolysis. (1) Physical separation Physical separation refers to the disassembly and separation of batteries, and the crushing, screening, magnetic separation, fine grinding and classification of battery components such as electrode active materials, current collectors and battery shells to obtain valuable high-content substances. Shin et al. proposed a method for recovering Li and Co from lithium-ion battery waste liquid using sulfuric acid and hydrogen peroxide, which includes two processes: physical separation of metal-containing particles and chemical leaching. Among them, the physical separation process includes crushing, screening, magnetic separation, fine grinding and classification. The experiment used a set of rotating and fixed blade crushers for crushing, and used sieves with different apertures to classify the crushed materials, and used magnetic separation for further processing to prepare for the subsequent chemical leaching process. Shu et al. developed a new method for recovering cobalt and lithium from lithium-sulfur battery waste using a mechanochemical method based on the grinding technology and water leaching process developed by Zhang et al., Lee et al. and Saeki et al. This method uses a planetary ball mill to grind lithium cobalt oxide (LiCoO2) and polyvinyl chloride (PVC) together in air to form Co and lithium chloride (LiCl) in a mechanochemical manner. Subsequently, the ground product was dispersed in water to extract chloride. Grinding promoted mechanochemical reactions. As grinding progressed, the extraction yields of Co and Li increased. Grinding for 30 minutes resulted in the recovery of more than 90% of Co and nearly 100% of lithium. At the same time, about 90% of the chlorine in the PVC sample had been converted into inorganic chloride. The operation of the physical separation method is relatively simple, but it is not easy to completely separate AA rechargeable battery, 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 High-temperature pyrolysis method refers to the high-temperature calcination and decomposition of lithium battery materials that have undergone preliminary separation treatments such as physical crushing to remove organic binders and thus separate the constituent materials of lithium batteries. At the same time, the metals and their compounds in the lithium battery can also be oxidized, reduced and decomposed, volatilized in the form of steam, and then collected by condensation and other methods. Lee et al. used high-temperature pyrolysis to prepare LiCoO2 from waste AA rechargeable battery. Lee et al. first heat-treated the LIB sample in a muffle furnace at 100-150°C for 1 hour. Secondly, the heat-treated battery was shredded to release the electrode material. The samples were disassembled with a high-speed crusher designed for this study and classified by size, ranging from 1 to 50 mm. Then, two steps of heat treatment were carried out in the furnace, the first heat treatment was at 100 to 500 ° C for 30 min, and the second heat treatment was at 300 to 500 ° C for 1 h, and the electrode material was released from the current collector by vibration screening. Next, the cathode active material LiCoO2 was obtained by burning at a temperature of 500 to 900 ° C for 0.5 to 2 h to burn off the carbon and binder. Experimental data show that the carbon and binder were burned at 800 ° C. The high-temperature pyrolysis treatment technology is simple and easy to operate. It has a fast reaction speed and high efficiency under high temperature environment, and can effectively remove the binder; and this method does not require high components of raw materials, and is more suitable for processing large quantities or more complex batteries. However, this method has high requirements for equipment; during the treatment process, the decomposition of organic matter in the battery will produce harmful gases, which is not friendly to the environment. It is necessary to add purification and recovery equipment to absorb and purify harmful gases to prevent secondary pollution. Therefore, the processing cost of this method is high. 2. Wet recovery The wet recovery process is to crush and dissolve the waste battery, 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., which can be directly recycled. Wet recovery is more suitable for recycling waste lithium batteries with relatively simple chemical composition. Its equipment investment cost is low and it is suitable for the recycling of small and medium-sized waste lithium batteries. Therefore, this method is currently widely used. (1) Alkali-acid leaching method Since the positive electrode material of AA rechargeable battery will not dissolve in alkaline solution, while the base aluminum foil will dissolve in alkaline solution, this method is often used to separate aluminum foil. When Zhang Yang et al. recovered Co and Li in the battery, they used alkaline leaching to remove aluminum in advance, and then used dilute acid solution to destroy the adhesion of organic matter to copper foil. However, the alkaline leaching method cannot completely remove PVDF, which has an adverse effect on subsequent leaching. Most of the positive electrode active substances in AA rechargeable battery can be dissolved in acid. Therefore, the pre-treated electrode material can be leached with acid solution to achieve the separation of active substances and current collectors, and then the target metal can be precipitated and purified by combining the principle of neutralization reaction, so as to achieve the purpose of recovering high-purity components. The acid solution used in the acid leaching method includes traditional inorganic acids, including hydrochloric acid, sulfuric acid and nitric acid. However, since harmful gases such as chlorine (Cl2) and sulfur trioxide (SO3) that have an impact on the environment are often produced during the leaching process using inorganic strong acids, researchers have tried to use organic acids to treat waste lithium batteries, such as citric acid, oxalic acid, malic acid, ascorbic acid, glycine, etc. Li and other electrodes recovered by dissolving in hydrochloric acid. Since the efficiency of the acid leaching process may be affected by the concentration of hydrogen ions (H+), temperature, reaction time and solid-to-liquid ratio (S/L), in order to optimize the operating conditions of the acid leaching process, experiments were designed to explore the effects of reaction time, H+ concentration and temperature. Experimental data show that when the temperature is 80°C, the H+ concentration is 4 mol/L, and the reaction time is 2h, the leaching efficiency is the highest, among which 97% of Li and 99% of Co in the electrode material are dissolved. Zhou Tao et al. used malic acid as a leaching agent and hydrogen peroxide as a reducing agent to reduce and leach the positive electrode active material obtained by pretreatment, and studied the effects of different reaction conditions on the leaching rates of Li, Co, Ni, and Mn in the malic acid leaching solution to find the optimal reaction conditions. The research data showed that when the temperature was 80°C, the malic acid concentration was 1.2 mol/L, the liquid-liquid volume ratio was 1.5%, the solid-liquid ratio was 40 g/L, and the reaction time was 30 min, the efficiency of malic acid leaching was the highest, among which the leaching rates of Li, 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 uses the principle of "like dissolves like" 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 components in order to better recover the active materials of the electrode when recycling lithium cobalt oxide batteries. NMP is a good solvent for PVDF (solubility is about 200g/kg), and its boiling point is relatively high, about 200°C. The study used NMP to treat the active material at about 100°C for 1h, effectively achieving the separation of the film from its carrier, and thus recovering Cu and Al in metal form by simply filtering it out of the NMP (N-methylpyrrolidone) solution. Another benefit of this method is that the recovered Cu and Al metals can be directly reused after sufficient cleaning. In addition, the 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 AA rechargeable battery. The waste AA rechargeable battery used in the experiment used polytetrafluoroethylene (PTFE) as an organic binder, and the effects of TFA concentration, liquid-to-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 a TFA solution with a mass fraction of 15, a liquid-to-solid ratio of 8.0 mL/g, a reaction temperature of 40°C, and a reaction time of 180 min under appropriate stirring, the cathode material can be completely separated. The experimental conditions for separating materials from foils using organic solvent extraction are relatively mild, but organic solvents have certain toxicity and may be harmful to the health of operators. At the same time, due to the different processes of AA rechargeable battery produced by different manufacturers, the selected binders are different. Therefore, for different production processes, manufacturers need to choose different organic solvents when recycling waste lithium batteries. In addition, for large-scale recycling and processing operations at the industrial level, cost is also an important consideration. Therefore, it is very important to choose a solvent that is widely available, reasonably priced, low in toxicity and harmless, and widely applicable. (3) Ion exchange method The ion exchange method refers to the use of ion exchange resins to separate metals by different adsorption coefficients of the metal ion complexes to be collected to achieve metal separation and extraction. After the electrode material was treated with acid leaching, Wang Xiaofeng et al. added an appropriate amount of ammonia water to the solution, adjusted the pH value of the solution, reacted with the metal ions in the solution, generated complex ions such as [Co(NH3)6]2+, [Ni(NH3)6]2+, and continuously introduced pure oxygen into the solution for oxidation. Then, different concentrations of ammonium sulfate solution were repeatedly passed through the weakly acidic cation exchange resin to selectively elute the nickel complex and trivalent cobalt ammonia complex on the ion exchange resin. Finally, a 5% H2SO4 solution was used to completely elute the cobalt complex, while regenerating the cation exchange resin, and using oxalate to recover the cobalt and nickel metals in the eluent. The ion exchange method has a simple process and is relatively easy to operate. 3. Biological recovery Mishra et al. used inorganic acid and acidophilic ferrothiobacillus to leach metals from waste AA rechargeable battery, and used S and ferrous ions (Fe2+) to generate metabolites such as H2SO4 and Fe3+ in the leaching medium. These metabolites help dissolve the metals in the waste batteries. Studies have found that the biodissolution rate of cobalt is faster than that of lithium. As the dissolution process proceeds, iron ions react with metals in the residue and precipitate, resulting in a decrease in the concentration of ferrous ions in the solution. As the metal concentration in the waste sample increases, cell growth is arrested and the dissolution rate slows down. In addition, a higher solid/liquid ratio also affects the rate of metal dissolution. Zeng et al. used Acidithiobacillus ferrooxidans to bioleach metallic cobalt from spent AA rechargeable battery. Unlike Mishra et al., this study used copper as a catalyst to analyze the effect of copper ions on the bioleaching of LiCoO2 by Acidithiobacillus ferrooxidans. 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, while in the absence of copper ions, only 43.1% of the cobalt was dissolved after 10 days of reaction time. In the presence of copper ions, the efficiency of cobalt dissolution in spent AA rechargeable battery is improved. In addition, Zeng et al. also studied the catalytic mechanism and explained the dissolution effect of copper ions on cobalt, in which LiCoO2 reacts with copper ions to form copper cobaltate (CuCo2O4) on the surface of the sample, which is easily dissolved by iron ions. 4. Combined recycling method The recycling process of waste lithium batteries has its own advantages and disadvantages. At present, there has been research on recycling methods that combine and optimize multiple processes to give full play to the advantages of various recycling methods and maximize economic benefits.