Introduction of recycling technology of lithium ion battery

Lithium ion batteries across the electrodes by slice, binder, electrolyte and the diaphragm, etc. In industry, mainly using the cobalt acid lithium, manganese acid lithium cobalt, nickel manganese acid lithium and lithium iron phosphate ternary material for lithium ion battery cathode material, with natural graphite and artificial graphite as the cathode active material. Polyvinylidene fluoride has loose (PVDF) is a widely used anode binder, viscosity, good chemical stability and physical properties. Six industrial production of lithium ion battery mainly adopts electrolyte lithium fluoride phosphate (LiPF6) and the configuration of the organic solvent solution as electrolyte, using organic membrane, such as cellular polyethylene (PE) and polypropylene (PP) as polymer battery diaphragm. Lithium ion battery is widely considered to be environmental pollution-free green batteries, but lithium ion battery recycling also will produce pollution.Although lithium ion batteries are not contained toxic heavy metals such as mercury, cadmium, lead, but the battery is anode materials and electrolyte still larger impact on the environment and human body.If using the method of ordinary garbage treatment to treat the lithium ion battery (landfill, incineration, composting, etc.), a battery of cobalt, nickel, lithium, manganese and other metal, metal and various organic and inorganic compounds will cause pollution, organic pollution, dust pollution, acid and alkali pollution.Lithium ion electrolyte machine transformations, such as LiPF6, six lithium fluoride and arsenic acid (LiAsF6), three lithium fluoride mesylate (LiCF3SO3), hydrofluoric acid (HF), solvent and hydrolysis products such as ethylene glycol dimethyl ether (DME) and methanol, formic acid and so on are toxic substances.Waste lithium ion battery, therefore, need to go through recycling, reduce the harm to natural environment and human health.

First, the production and use of lithium ion batteries

Lithium ion batteries with high energy density, high voltage, low self-discharge, loop performance is good, the advantages of the operation safety, and relatively friendly to the natural environment, therefore they are widely used in electronic products, such as mobile phones, tablets, laptops and digital cameras, etc.In addition, the lithium ion battery in water, fire, such as wind and solar energy storage power system has broad application, and gradually becomePower batteryThe best choice.lithium iron phosphate batteries, promote the development of the lithium-ion batteries in electric vehicle industry and application.As people demand for electronic products gradually increases and the electronic products renewal speed gradually accelerated, and the influence of the rapid development of new energy vehicles, the global market demand for lithium ion batteries is more and more big, the battery production rate increased year by year.

The huge demand for the lithium ion battery, on the one hand, in the future there will be a large number of used batteries, how these waste lithium ion battery processing to reduce the impact on the environment, is the problem to be solved;On the other hand, in response to the huge demand of market, manufacturers need to produce a large number of lithium ion battery to supply market.At present, the production of lithium ion battery anode materials mainly include cobalt acid lithium, manganese acid lithium cobalt, nickel manganese acid lithium ternary material and lithium iron phosphate, so waste lithium ion battery contains more cobalt (Co), lithium (Li), nickel (Ni), manganese (Mn), copper (Cu), iron (Fe), such as metal resources, includes a variety of rare metal resources, cobalt in our country is belong to the scarce strategic metals, mainly in the form of imports to meet growing demand.Parts of the waste lithium ion battery metal content than natural minerals in the high metal content, in the case of production resources increasingly scarce, therefore, recycling of waste batteries has certain economic value.

Second, the lithium ion battery recycling technology

Waste lithium ion battery recycling process including pretreatment, secondary processing and deep processing.Due to waste batteries still remain part of the electricity, so the pretreatment process includes deep discharge process, crushing, physical separation;Secondary processing is to realize the purpose of the is the cathode active material and the complete separation of base, commonly used heat treatment method, dissolved organic solvent method, alkali dissolution method and electrolysis method to realize the complete separation of the two;Deep processing mainly includes the leaching process of separation and purification of 2, extract the valuable metal material.Classified by extraction technology, battery recycling method can be mainly divided into: dry recovery and recovery at wet and biological recovery 3 categories of technology.

1. The dry process

Dry medium, such as recycling is the solution directly implement material or the recovery of valuable metals.Among them, the main methods are physical separation method and high-temperature pyrolysis method.

(1) physical separation method

Physical separation method is to point to separate the battery apart, the electrode active material, set fluid and battery shell battery components through crushing, sieving, magnetic separation, fine grinding and classification, and the high content of valuable materials.Shin, and put forward a kind of using sulfuric acid and hydrogen peroxide to lithium ion battery recycling Li, Co in the waste liquid, including physical separation contain two metal particles and chemical leaching process.Among them, the physical separation process includes crushing, sieving, magnetic separation, fine grinding and classification.Experiment using a set of rotating and stationary blade crusher broken, broken material with different aperture sieve classification, and USES magnetic separation and further processing, in preparation for the subsequent chemical leaching process.

Shu, such as Zhang, Lee and Saeki grinding technology research and development and water in addition to the process, on the basis of the development of a lithium sulfur batteries scrap from using mechanochemical method and a new method of recovery of cobalt and lithium.The method using the planetary ball mill in air common grinding cobalt acid lithium (LiCoO2) and polyvinyl chloride (PVC), mechanical chemical way to form Co and lithium chloride (LiCl).Subsequently, scatter grinding product to extract chloride in water.Grinding promoted the mechanical chemical reaction.As you progress through the grinding, Co and Li extraction yield were improved.30 min grinding make recovery more than 90% of Co and nearly 100% of lithium.At the same time, the PVC samples about 90% of the chlorine has been converted into inorganic chloride.

Physical separation method of the operation is simple, but not easy to complete separation of lithium ion battery, and when the sieving and magnetic separation, easy mechanical entrainment loss, difficult to achieve the complete separation of the metal recycling.

(2) high temperature pyrolysis

High temperature pyrolysis is through physical broken preliminary separation processingThe lithium batteryMaterial, high temperature burning decomposition, remove organic adhesives, and separation of lithium battery materials.At the same time can also make the lithium battery of metals and their compounds oxidation reduction and decomposition of volatile in the form of steam, and then use methods of condensation collection.

Lee using waste lithium ion battery, such as the preparation of LiCoO2, adopted high temperature pyrolysis method.Lee first LIB to sample in muffle furnace such as 100 ~ 150 ℃ under the environment of 1 h heat treatment.Second, cut up by the heat treatment of the battery electrode material release.Samples with a specially designed for the study of high speed grinder and dismantling, classified according to size, size range is 1 ~ 50 mm.Then, in step 2 heat treatment furnace, for the first time in 100 ~ 500 ℃ heat treatment under 30 min, the second heat treatment for 1 h under 300 ~ 500 ℃, through vibration screening electrodes materials released from the collection of fluid.Next, in 500 ~ 900 ℃ temperature 0.5 ~ 2 h burning, burning carbon and adhesives, obtain LiCoO2 cathode active material.Experimental data show that carbon and adhesive is burned off at 800 ℃.

High temperature pyrolysis processing technology is simple, easy to operate, under the environment of high temperature reaction speed, high efficiency, can effectively remove adhesive;And requirements for the composition of raw material is not high, this method is suitable for processing large or complex cells.But the method of equipment demand is higher;In the process, the battery will produce harmful gases, organic matter decomposition is not friendly to the environment, the need to increase the purification recycling equipment, absorb the harmful gas purification, prevent to produce secondary pollution.Therefore, the method of processing cost is higher.

2. Wet recovery

Wet method is dissolved after the waste battery recycling technology, and then use suitable chemical reagent, selective separation of metal elements in the leaching solution, output the high grade of cobalt metal or lithium carbonate, etc., directly to recycle.Wet method is suitable for recycling recycling waste lithium batteries chemical composition is relatively single, the equipment investment cost is low, suitable for small and medium-sized discarded li-ion batteries.Therefore, this method is widely used at present.

(1) alkaline acid leaching method

As a result of the lithium ion battery cathode material not soluble in alkali liquor in the basement of aluminum foil, dissolve in lye, so this method is used to separate the aluminum foil.Zhang Co and Li in the recycling batteries, such as with alkali leaching in addition to the aluminum in advance, and then use diluted acid soaking destruction of organic matter and copper foil adhesive.But alkali leaching method do not completely remove PVDF, leaching has negative impact on the follow-up.

Most of the lithium ion battery cathode active material can be dissolved in acid, so can be processed in advance of electrode material with acid solution leaching, separation of implementation and active materials, combined with the principle of the neutralization reaction for the purpose of metal precipitation and purification, so as to achieve the purpose of the recovery of high purity components.

Acid leaching method using acid solution with the traditional inorganic acid, such as hydrochloric acid, sulfuric acid and nitric acid.But because in the process of using inorganic acid leaching, often produces chlorine (Cl2) and sulfur trioxide (SO3) and so on have an effect on environment of harmful gases, so the researchers try to deal with waste lithium-ion batteries, using organic acid such as citric acid, oxalic acid, malic acid, ascorbic acid, glycine, etc.Li using hydrochloric acid to dissolve the recycling, etc.The efficiency of the pickling process could be hydrogen ions (H +) concentration, temperature, reaction time and solid-liquid ratio (S/L), in order to optimize the operating conditions of acid leaching process, designed the experiments to explore the reaction time, the influence of H + concentration and temperature.Experimental data show that when the temperature is 80 ℃, the H + concentration in 4 mol/L, the reaction time of 2 H, the leaching efficiency highest, among them, 97% of Li and 99% of Co in the electrode material is dissolved.LLLDD, malic acid as leaching agent and hydrogen peroxide as reducing agent for the positive active material obtained by pretreatment of reduction leaching, and through the study of different reaction conditions on the malic acid leach liquor Li leaching rate, Co, Ni, Mn, thus find out the best reaction conditions.Research data show that when the temperature is 80 ℃, is 1.2 mol/L malic acid concentration, liquid fluid volume ratio is 1.5%, the solid liquid than 40 g/L, the response time of 30 min, the use of malic acid leaching efficiency highest, Li, Co, Ni, Mn, leaching rate reached 98.9%, respectively, 94.3%, 95.1% and 96.4%.However, compared with inorganic acid, use organic acid leaching high cost.

(2) organic solvent extraction

Organic solvent extraction method by using the principle of "similarity", using a suitable organic solvent, to physical dissolve organic binder, thus less material and foil adhesive force, to separate the two.

Contestabile in recycling, etc. cobalt acid lithium batteries in order to better recovery of electrode active material, using N - methyl pyrrolidone (NMP) for selective separation of components.NMP is a good solvent for PVDF (solubility is about 200 g/kg), and its high boiling point, about 200 ℃.Research using NMP in about 1 h under 100 ℃ to active material processing, effectively realized the separation of the film and its carrier, and therefore through from the NMP (N - methyl pyrrolidone) in the solution simply filtered out, thereby recycling metal forms of Cu and Al.Another benefit of recycling the method of Cu and Al two metals in full can be directly reused after cleaning.In addition, the recycling of NMP can be recycled.Due to their high solubility in PVDF, so can be reused many times.Zhang, etc in the lithium ion battery cathode in recycling waste materials, using trifluoroacetic acid (TFA) to separate the cathode material and aluminum foil.Waste lithium-ion batteries used in the experiment using polytetrafluoroethylene (PTFE) as an organic binder, systematically studied the concentration of TFA, liquid-solid ratio (L/S), reaction temperature and reaction time on the influence of the cathode materials and aluminum foil separation efficiency.The experimental results show that the mass fraction of 15 TFA solution in liquid-solid ratio 8.0 mL/g, reaction temperature of 40 ℃, under a proper stirring reaction 180 min, cathode materials can be completely separated.

Organic solvent extraction method is used to separate materials and foil experiment condition is mild, but have certain toxic organic solvent, the operator may produce harm body health.At the same time, due to the different manufacturer production of lithium ion battery technology, the choice of adhesive, so according to different production process, factory in recycling waste lithium battery, need to choose a different organic solvents.In addition, for the industrial level of large-scale recycling operation, the cost is also an important consideration.Therefore, a choice of sources harmless, suitable price, low toxicity, wide applicability of solvent is very important.

(3) the ion exchange method

Ion exchange method refers to using ion exchange resin to metal ion complex adsorption coefficient should be collected to achieve different metal extraction.Wang xiaofeng, such as the electrode material after treated with acid leaching, adding suitable amount of ammonia in aqueous solution, and adjust the pH value of solution, react with metal ions in solution, generated [Co (NH3) 6] 2 +, [Ni (NH3) 6] 2 + complex ions, and continuously to the solution into the pure oxygen oxidation.Then, using different concentrations of ammonium sulphate solution by repeatedly weak acid cation exchange resin, respectively on the selectivity of the ion exchange resin trivalent cobalt nickel complex compound and ammonia complex elution.Finally using 5% - H2SO4 solution to cobalt complex elution completely, at the same time make the cation exchange resin regeneration, and by using oxalic acid salt respectively eluent of cobalt, nickel metal recycling.Process of ion exchange method is simple, easy to operation.

3. The biological recycling

Mishra, such as using inorganic acid and acidophilic thiobacillus ferrous oxide leaching metal from waste lithium ion battery, and use (Fe2 +) S and ferrous ions, generated in leaching medium - H2SO4, Fe3 + and other metabolites.The metal in these metabolites help dissolve dead batteries.The study found that the cobalt biological dissolve faster than lithium.As the dissolution process of iron ions react with the metal residue and precipitation, causes the ferrous ion concentration in the solution decreases, and with the increase of waste metal concentration in the sample, the growth of cells is prevented, dissolution rate, slow down.In addition, the high solid/liquid ratio also affects the rate of metal dissolution.Zeng, such as use of acidophilic thiobacillus ferrous oxide cobalt metal in biological leaching waste lithium ion battery, unlike Mishra, etc, with copper as a catalyst for the study, analysis of acidophilic thiobacillus ferrous oxide copper ions influence on LiCoO2 biological leaching.Results show that almost all of the cobalt (99.9%) in Cu ion concentration is 0.75 g/L, the creature is put into solution leaching after 6 days, and in the absence of copper ions, after 10 days of reaction time, only 43.1% of the cobalt dissolved.In the presence of copper ions, waste lithium ion battery of the cobalt leaching efficiency.In addition, such as Zeng also studied the catalytic mechanism, explains the copper ion solution effect of cobalt, LiCoO2 and cation exchange reaction occurred in the copper ion, formed on the surface of cobalt acid copper (CuCo2O4), iron ion could easily dissolved.

Biological leaching method of low cost, high recovery efficiency, less pollution and consumption, are small impact on the environment, and microbes can use again.But efficient microbial bacteria cultivation, processing cycle is long, leaching condition of control is the method needs a few big difficult problem.

4. Joint recycling method

Old lithium battery recycling process each have advantages and disadvantages, there are joint, research methods and optimize various process of recycling, in order to give full play to the advantages of the method of recycling, maximize economic benefits.

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