Research and progress of metal recovery in waste lithium ion batteries

　　Author ：Iflowpower – Portable Power Station Supplier

The energy and environment is the two major issues that have been facing in the 21st century, the development of new energy development and resources is the basis and direction of human sustainable development. In recent years, lithium-ion batteries have been widely used due to light quality, small volume, self-discharge, no memory effect, wide operating temperature range, fast charge and discharge, long service life, environmental protection and other advantages. The earliest Whittingham made the first lithium-ion battery using the Li-TIS system, in 1990, it has developed more than 40 years since 1990, has made great progress.

According to statistics, the total amount of lithium-ion battery in my country in June 2017 was 8.99 billion, with a cumulative increase rate of 34.6%.

International, lithium-ion batteries in the aerospace power field have entered the engineering application stage, and some companies and military departments in the world have developed in space for lithium-ion batteries, such as the United States, National Aeronautics and Space Administration (NASA), EAGLE -Picher battery company, France SAFT, Japan's JAXA, etc. With the wide application of lithium ion batteries, there is more and more quantities of waste batteries. It is expected that before and after 2020, my country's only pure electric (including plug-in) passenger car and hybrid passenger vehicle power lithium battery is 12-77 million T.

Although the lithium-ion battery is called a green battery, there is no harmful element such as Hg, PB, but its positive material, electrolyte solution, etc., which causes great pollution to the environment, and also causes waste of resources. Therefore, review the process status of the recovery treatment of waste lithium-ion batteries at home and abroad, and summarizes the development direction of waste lithium-ion battery recovery process, it has important practical significance.

An important component of lithium-ion battery includes a housing, an electrolyte, anode material, a cathode material, an adhesive, a copper foil, and an aluminum foil, and the like. Among them, CO, Li, Ni mass fraction is 5% to 15%, 2% to 7%, 0.5% to 2%, as well as metal elements such as Al, Cu, Fe, and the value of important components, the anode The material and cathode materials account for about 33% and 10%, and the electrolyte and the diaphragm have accounted for 12% and 30%, respectively.

Important recovered metals in waste lithium ion batteries are Co and Li, important concentrated cobalt lithium film on anode material. Especially in my country's cobalt resources is relatively poor, development and utilization is difficult, and the mass fraction of cobalt in lithium-ion batteries accounts for about 15%, which is 850 times of accompanying cobalt mines. Currently, the application of LiCoO2 is a lithium ion battery of the positive material, which contains lithium cobalt organte, lithium hexafluorophosphate, organic carbonate, carbon material, copper, aluminum, etc.

, the important metal content is shown in Table 1. The use of wet process to treat waste lithium-ion batteries is currently studied more and more processes, and the process flow is shown in Figure 1. Important experience 3 stages: 1) Press the recovered relief lithium ion battery to completely discharge, simple splitting, etc.

The electrode material obtained after pre-treatment is dissolved, so that the various metals and its compounds into the form of ions into the leaching liquid; 3) Separation and recovery of the valuable metal in the leaching solution, this stage is the key to waste lithium ion battery treatment processes It is also the focus and difficulties of researchers for many years. At present, the method of separating and recovery is important with solvent extraction, precipitation, electrolysis, ion exchange method, salting and etiology. 1.

1, the pre-electric waste of the remaining electricity, the residual part of the ion battery, is thoroughly discharged before processing, otherwise the residual energy will concentrate on a large amount of heat, which may cause adverse effects such as safety hazards. The discharge method of waste lithium ion batteries can be divided into two types, which are physical discharge and chemical discharge. Among them, physical discharge is short-circuit discharge, usually using liquid nitrogen and other freezing liquids to be low-temperature freezing, and then press the hole forced discharge.

In the early days, Umicore, the US Umicore, TOXCO uses liquid nitrogen to discharge the waste lithium ion battery, but this method is high for equipment, not suitable for large-scale industrial applications; chemical discharge is in conductive solution (more Release residual energy in electrolysis in NaCl solutions. Early, Nan Junmin, etc., placed a monomer waste lithium ion battery in a steel container of water and electron conductive agent, but since the electrolyte of the lithium ion battery contained LiPF6, the reaction was reflected in contact with water.

HF, bringing harm to the environment and operators, so it is necessary to make alkaline immersion immediately after discharge. In recent years, Song Xiuling, etc. The concentration of 2g / L, discharge time is 8h, the final consolidation voltage is reduced to 0.

54V, meet green efficient discharge requirements. In contrast, the chemical discharge cost is lower, the operation is simple, can meet the application of large-scale discharge, but the electrolyte has a negative impact on the metal housing and equipment. 1.

2, the process of breaking separation and fragmentation is important to isolate the electrode material by multi-stage crushing, screening, etc. by multi-stage crushing, screening, etc. by multi-stage crushing, screening, etc.

, to facilitate subsequent use of fire. Method, wet method, etc. Mechanical separation method is one of the pretreatment methods that are generally used, easy to achieve large-scale industrial recovery treatment of waste lithium-ion batteries.

SHIN et al., By crushing, screening, magnetic separation, fine pulverizing and classification process to achieve LiCoO2 separation enrichment. The results show that the recovery of the target metal can be improved under better conditions, but since the lithium ion battery structure is complex, it is difficult to completely separate the components by this method; Li et al.

, Use a new type of mechanical separation method, improvement The recovery efficiency of CO reduces energy consumption and pollution. Regarding the electrode material split, it was rinsed and stirred in a 55 ¡ã C water bath, and the mixture was stirred for 10 min, and the resulting 92% electrode material was separated from the current fluid metal. At the same time, the current collector can be recovered in the form of a metal.

1.3, the process of heat treatment heat treatment is important to remove organic matter, toner, etc., toner, etc.

of waste lithium ion batteries, and separation for electrode materials and current fluids. The current heat treatment method is mostly high temperature conventional heat treatment, but there is a problem of low separation, environmental pollution, etc., in order to further improve the process, in recent years, the research has more and more.

SUN et al., A high-temperature vacuum pyrolysis, a waste battery material is picked up in a vacuum furnace before pulverizing, and the temperature is 10 ¡ã C to 600 ¡ã C for 30 min, and the organic matter is decomposed in a small molecule liquid or gas. It can be used for chemical raw materials separately.

At the same time, the LiCoO2 layer becomes loose and easy to separate from the aluminum foil after heating, which is advantageous for the final inorganic metal oxide. Pretreatment of waste lithium ion battery positive material. The results show that when the system is less than 1.

0 kPa, the reaction temperature is 600 ¡ã C, the reaction time is 30 min, the organic binder can be substantially removable, and most of the positive electrode active substance is detached from the aluminum foil, the aluminum foil is kept intact. Compared to conventional heat treatment techniques, high-temperature vacuum pyrolysis can be recovered separately, improve the comprehensive utilization of resources, while preventing the toxic gases from the organic material from decomposing to cause contamination on the environment, but the equipment is high, complex, industrialization Promotion has certain limitations. 1.

4. Often the PVDF on the dissolution electrode of the strongly polar organic solvent, so that the positive electrode material is detached from the current fluid aluminum foil. Liang Lijun selected a variety of polar organic solvents for dissolving the crushing positive electrode material, and found that the optimum solvent was N-methylpyrrolidone (NMP), and the positive electrode material active substance LIFEPO4 and carbon mixture can be made under optimal conditions.

It is completely separated from aluminum foil; Hanisch et al, uses the dissolution method to thoroughly select the electrode after heat treatment and mechanical pressure separation and screening process. The electrode was treated at 90 ¡ã C in NMP for 10 to 20 min. After repeating 6 times, the binder in the electrode material can completely dissolve, and the separation effect is more thorough.

The solubility is compared to other pre-treatment methods, and the operation is simple, and it can effectively improve the separation effect and recovery rate, and the industrialized application prospect is better. At present, the binder is mostly used by NMP, which is better, but due to lack of price, volatile, low toxicity, etc., to some extent, to a certain extent, its industrial promotion application.

The dissolution leaching process is to dissolve the electrode material obtained after pretreatment, so that the metal elements in the electrode material into the solution in the form of ions, and then selectively separated by various separation techniques and recovers important metal CO, Li et al. Methods of dissolved leaching Important include chemical leaching and biological leaching. 2.

1, chemical leaching conventional chemical leaching method is to achieve dissolution leaching of electrode materials by acid immersion or alkaline immersion, and it is important to include a step leaching method and two-step leaching method. One-step leaching method usually uses an inorganic acid HCl, HNO3, H2SO4, and the like to directly dissolve the electrode material directly to the electrode material, but such a method will have harmful gases such as CL2, SO2, so that the exhaust gas treatment. The study found that H2O2, Na2S2O3 and other reducing agents such as H2O2, Na2S2O3 were added to the leaching agent, and this problem can be effectively solved, and the CO3 + is also easier to dissolve CO2 + in the leaching liquid, thereby increasing the leaching rate.

Pan Xiaoyong et al. Adopts an H2SO4-Na2S2O3 system to leach electrode material, separating and recovering CO, Li. The results showed that the H + concentration of 3 mol / L, Na2S2O3 concentration of 0.

25 mol / L, liquid solid ratio 15: 1, 90 ¡ã C, CO, Li leaching rate was higher than 97%; Chen Liang et al, H2SO4 + H2O2 was leached Leaching the active substance. The results showed that the liquid solid ratio was 10: 1, H2SO4 concentration 2.5 mol / l, H2O2 added by 2.

0 ml / g (powder), temperature 85 ¡ã C, leaching time of 120 min, Co, Ni and Mn, 97%, respectively, 98% and 96%; Lu Xiuyuan et al. To leach the use of the H2SO4 + Raised agent system to leach the waste high-nickel lithium-ion battery positive electrode material (lini0.6CO0.

2Mn0.2O2), studied different reducing agents (H2O2, glucose and Na2SO3) on metal leaching effects. influence.

The results show that under the most suitable conditions, H2O2 is used as a reducing agent, and the leaching effect of the important metal is preferably 100%, 96.79%, 98.62%, 97%, respectively.

Comprehensive opinion, using acid-reducing agents as the leaching system, it is the mainstream leaching process of the current industrial treatment of waste lithium-ion batteries due to the advantages of direct acid immersion, higher leaching rate, faster reaction rate, etc. The two-step leaching method is to perform alkali leaching after a simple pre-treatment, so that Al in the form of NaAlO2 in the form of NaAlO2, and then adding a reducing agent H2O2 or Na2S2O3 as a leaching solution, obtained The leaching liquid is adjusted by adjusting the pH, selectively settle Al, Fe and collects the obtained mother liquor to further carry out the obtained mother liquor and separation and separation. Deng Chao Yong et al.

Was carried out using a 10% NaOH solution, and the Al leaching rate was 96.5%, 2 mol / L H2SO4 and 30% H2O2 were acid immersion, and the CO leaching rate was 98.8%.

The leaching principle is as follows: 2licoo2 + 3H2SO4 + H2O2→Li2SO4 + 2CoSO4 + 4H2O + O2 will be obtained by the obtained leaching solution, with a multi-stage extraction, and the final CO recovery reaches 98%. The method is simple, easy to operate, small corrosion, less pollution. 2.

2, Biological Leaching Law As the technology development, biometrial technology has better development trends and application prospects due to its efficient environmental protection, low cost. Biological leaching method is based on the oxidation of bacteria, so that the metal into the solution in the form of ions. In recent years, some researchers have studied the price-priced metal in the use of biological leaching methods.

MISHRA et al. Using inorganic acid and eosubric acid oxide oxide bacillus to leach the waste lithium ion battery, using elements S and Fe2 + as energy, H2SO4 and FE3 + and other metabolites in the leaching medium, and use these metabolites to dissolve the old lithium Ion battery. The study found that CO's biological dissolution rate is faster than Li.

Fe2 + can promote biota growth reproduction, FE3 + and metal in the residue. Higher liquid solid ratio, i.e.

, new growth of metal concentration, can inhibit the growth of bacteria, is not conducive to metal dissolution; MarcináKováEtOAc. The nutritious medium is composed of all the minerals required for bacterial growth, and the low nutrient medium is used as energy in H2SO4 and element S. The study found that in the rich nutritional environment, the biological leaching rates of Li and CO were 80% and 67%, respectively; in a low nutritional environment, only 35% Li and 10.

5% CO were dissolved. Biological leaching method compared to the traditional acid-reducing agent leaching system, has the advantage of low cost and green environmental protection, but the leaching rate of important metals (CO, Li et al.) Is relatively low, and the large-scale processing of industrialization has certain limitations.

3.1, solvent extraction method solvent extraction method is the current process of separation and recovery of metal elements of waste lithium ion batteries, which is to form a stable complex with a target ion in the leaching liquid, and use appropriate organic solvents. Separate, to extract target metal and compound.

Usually used extractants are important to Cyanex272, Acorgam5640, P507, D2EHPA and PC-88A, etc. Swain et al. Study the effect of CYANEX272 extractant concentration on CO, Li.

The results showed that the concentration of 2.5 to 40 mol / m3, CO was increased from 7.15% to 99.

90%, and Li's extraction increased from 1.36% to 7.8%; concentration of 40 to 75 mol / m3, CO extraction rate basis The extraction rate of Li is newly added to 18%, and when the concentration is higher than 75 mol / m3, the separation factor of CO reduces the concentration, the maximum separation factor is 15641.

After the two-step method of Wu Fang, after extracting the extract of the extractant P204, P507 was extracted from CO, Li, and then H2SO4 was reversed, and the recovered extract was added to Na2CO3 selective recovery Li2CO3. When the pH is 5.5, CO, Li separation factor reaches 1×105, CO recovery is above 99%; kang et al.

From zealic 5% to 20% CO, 5% ~ 7% Li, 5% ~ 10% Ni, 5% organic chemicals and 7% plastic waste lithium ions Cobalt sulfate is recovered in the battery, and the CO concentration is 28 g / L, the pH is adjusted to 6.5 settled metal ion impurities such as Cu, Fe and Al. Then selectively extract Co from the purified aqueous phase by Cyanex 272, when pH <6, the separation factor of CO / Li and CO / Ni is close to 750, and the total recovery of CO is about 92%.

It can be found that the concentration of the extractant has a large effect on the extraction rate, and the separation of important metals (CO and Li) can be achieved by controlling the pH of the extraction system. On this basis, the use of a mixed extraction system is treated with the waste lithium-ion battery, which can better achieve the selective separation and recovery of important metal ions. PRANOLO et al, a mixed extraction system selectively recovered Co and Li in waste lithium-ion battery leacals.

The results show that the 2% (volume ratio) ACORGAM 5640 is added to 7% (volume ratio) Ionquest801, and the pH of the extraction Cu can be reduced, and Cu, Al, FE will be extracted into the organic phase by the control system pH, and Implement Separation with Co, Ni, Li. The pH of the system was then controlled at 5.5 to 6.

0, and the Co selective extraction of CO selective extraction, Ni and Li in the extraction fluid were negligible; Zhang Xinle et al. Used to use acid immersion - extraction - precipitation Co in the ion battery. The results show that the acid dip is 3.

5, and the extractant P507 and the Cyanex272 volume ratio of 1: 1 are extracted, the CO extract is 95.5%. The subsequent use of H2SO4 reverse fitting, and the pelletion of the anti-extract pH is 4 min, and the precipitation rate of CO can reach 99.

9%. Comprehensive view, the solvent extraction method has the advantages of low energy consumption, good separation effect, acid immersion-solvent extraction method is currently the mainstream process of waste lithium ion batteries, but further optimization of extractants and extraction conditions It is the current research focus in this field to achieve more efficient and environmentally friendly and recyclable effects. 3.

2, the precipitation method is to prepare the waste lithium-ion battery. After dissolving, the CO, Li solution is obtained, and the precipitant is added to the precipitation, the important target metal Co, Li, etc., to achieve the separation of metals.

SUN et al. Emphasized using H2C2O4 as a leaching agent while precipitation of CO ions in the solution in the form of COC 2O4, and then the Al (OH) 3 and Li2CO3 were precipitated by adding precipitant NaOH and Na2CO3. Separation; Pan Xiaoyong et al around PH is adjusted to 5.

0, which can remove most of Cu, Al, Ni. After further extraction, 3% H2C2O4 and saturated Na2CO3 settlement COC2O4 and Li2CO3, CO recovery is higher than 99% The Li recovery rate is higher than 98%; Li Jinhui pretreated after preparation of waste lithium ion batteries, the particle size of less than 1.43 mm is screened with a concentration of 0.

5 to 1.0 mol / L, and the solid-liquid ratio is 15 to 25 g / L. 40 ~ 90min, resulting in COC2O4 precipitate and Li2C2O4 leaching solution, the final COC2O4 and Li2C2O4 recovery exceeded 99%.

The precipitation is high, and the recovery rate of important metals is high. The control pH can achieve the separation of metals, which is easy to achieve industrialization, but is easily interfered with impurities, which is relatively low. Therefore, the key to the process is to select a selective precipitation agent and further optimize process conditions, control the order of the privalent metal ion precipitation, thereby improving the purity of the product.

3.3. Electrolytic electrolytic method recovering the valvily metal in the waste lithium ion battery, is a method of chemical electrolysis in the electrode material leaching liquid, so that it is reduced to a single or sediment.

Do not add other substances, it is not easy to introduce impurities, can obtain high purity products, but in the case of multiple ions, a total deposition occurs, thereby reducing product purity, while consuming more electrical energy. Myoung et al. Waste lithium ion battery positive material leaching liquid for HNO3 treatment is a raw material, and cobalt is recovered with a constant potential method.

During the electrolysis process, O2 is reduced to NO3 - a reduction reaction, the OH-concentration is added, and CO (OH) 2 is generated on the surface of the Ti cathode, and the heat treatment is obtained by CO3O4. The chemical reaction process is as follows: 2H2O + O2 + 4E→4OHNO3- + H2O + 2E→NO2- + 2OHCO3 ++ E→CO2 + CO2 ++ 2OH- / TI→CO (OH) 2 / Ti3CO (OH) 2 / Ti + 1 / 2O2→CO3O4 / TI + 3H2OFREITAS, etc., using constant potential and dynamic potential technology to recover CO from the positive material of the waste lithium ion battery.

The results show that the charge efficiency of CO decreases as the pH is increased, pH = 5.40, potential -1.00V, charge density 10.

0c / cm 2, the charge efficiency is maximum, reaching 96.60%. The chemical reaction process is as follows: CO2 ++ 2OH-→CO (OH) 2 (S) CO (OH) 2 (S) + 2E→CO (S) + 2OH-3.

4, the ion exchange method ion exchange method is the difference in adsorption capacity of different metal ion complexes such as Co, Ni, realizing the separation and extraction of metals. FENG et al. Adding to the recovery of CO from the positive electrode material H2SO4 leaching liquid.

Study on the recovery rate of cobalt and the separation of other impurities from factors such as pH, cycle of the leach. The results showed that the TP207 resin was used to control the pH = 2.5, the circulation was 10 treated.

The removal rate of Cu reached 97.44%, and the recovery of cobalt reached 90.2%.

The method has a strong selectivity of the target ion, simple process and easy to operate, is extracted for the extraction of the price of the variable metal in the waste lithium ion battery, which has supplied new ways, but due to the high cost limit, industrial application. 3.5, saltingation of salinization is to reduce the dielectric constant of the leaching liquid by adding saturated (NH4) 2SO4 solution and low dielectric constant solvent in waste lithium ion battery leaching solution, thereby reducing the dielectric constant of the leaching liquid, and the cobalt salt is precipitated from the solution.

The method is simple, easy to operate and low, but under the conditions of a variety of metal ions, with the precipitation of other metal salts, thereby reducing the purity of the product. Jin Yujian et al, according to the modern theory of electrolyte solution, the use of salinated lithium ion batteries. A saturated (NH4) 2SO4 aqueous solution and anhydrous ethanol were added from the HCl leaching liquid from LiiCoO2 as a positive electrode, and when the solution, saturated (NH4) 2SO4 aqueous solution and anhydrous ethanol were 2: 1: 3, CO2 + precipitation rate More than 92%.

The resulting salted product is (NH4) 2CO (SO4) 2 and (NH4) Al (SO4) 2, which uses segmented salts to separate the two salt, thereby obtaining different products. About the extraction and separation of the valuable metal in the waste lithium ion battery leach, the above is a few ways to study more. Considering factors such as processing volume, operating cost, product purity and secondary pollution, Table 2 summarizes the technical method of comparing several metal separation extraction described above.

At present, the application of lithium-ion batteries in electrical energy and other aspects is more extensive, and the number of waste lithium-ion batteries cannot be underestimated. At this stage, the waste-free lithium-ion battery recovery process is important for pre-treatment - leaching-wet recycling. The former treatment includes discharging, crushing and electrode material separation, etc.

Among them, the dissolution method is simple, and it can effectively improve the separation effect and recovery rate, but the currently used significant solvent (NMP) is expensive to a certain extent, so that the application of more suitable solvent is worth researching in this field. One of the directions. The leaching process is important with acid-reducing agent as a leaching agent, which can achieve a preferred leaching effect, but there will be secondary pollution such as inorganic waste liquid, and the biological leaching method has an advantage of efficient, environmental protection and low cost, but there is an important metal.

The leaching rate is relatively high, and the optimization of the choice of bacteria and the optimization of leaching conditions can increase the leaching rate, one of the research directions of the future leaching process. Valentine metals in wet recovery leaching solutions are key links of waste lithium-ion battery recovery process, and the key points and difficulties of research in recent years, and important methods have solvent extraction, precipitation, electrolysis, ion exchange method, salt analysis Wait. Among them, the solvent extraction method is currently used in many ways, with low pollution, low energy consumption, high separation effect and product purity, and the choice and development of more efficient and low-cost extractants, effectively reducing operating costs, and Further exploration of various extractants synergies can be one of the directions of the focus of this field.

In addition, the precipitation method is also a key to another direction of its research due to its advantages of high recovery rate, low cost and high processing. At present, the important problem in the presence of the precipitation method is low, so, regarding the selection and process conditions of the sedimentation, it will control the sequence of privalent metal ion precipitation, thereby increasing product purity will have better industrial application prospects. At the same time, in the process of waste lithium-ion battery treatment, secondary pollution such as waste liquid, waste residue can not be prevented, and the harm of secondary pollution is minimized while resource is utilized to achieve waste lithium ion batteries.

Environmental, efficient and low cost rec.