1 echelon use and the raw material recovery retired power lithium battery, take the Echelon to use the road, is the Echelon uses after the material recovery, the direct material recovery is the batch is too small, has no history to check, the safety monitoring unqualified and so on. The pursuit of economic efficiency is the driving force of enterprise and social behavior. According to the rationale, Echelon utilization, to the battery can be used to reduce the value of the maintenance costs below, and then do the recycling of raw materials, is the maximum battery value. But the actual situation is that the early power battery traceability is poor, quality, models are uneven. Early battery echelon use risk, eliminate the risk of high cost, so it can be said, in the power of battery recovery in the early stage, the battery to the approximate rate of raw material recovery. 2 positive material valuable metal extraction method The current power lithium battery recycling, in fact, did not do all kinds of materials on the entire battery of the comprehensive recovery and reuse. The main types of cathode materials include: lithium cobalt oxide, lithium manganese oxide, ternary lithium, lithium iron phosphate and so on. Battery cathode material cost of more than 1/3 of the cost of a single battery, and because the cathode currently uses graphite and other carbon materials, lithium titanate li4ti5o12 and silicon carbon negative s I/C application is less, so the current battery recovery technology is mainly for battery cathode material recovery. The recovery methods of waste lithium batteries mainly include physical, chemical and biological methods. Compared with other methods, Hydrometallurgy is considered as an ideal recovery method because of its low energy consumption, high recovery efficiency and higher purity of products. 2.1 The physical method uses physical chemical reaction to process lithium ion batteries.
The most common methods of physicochemical treatment are crushing flotation and mechanical lapping method.
1 The crushing flotation method is a method of separating the physical and chemical properties of the material surface, that is, firstly, after crushing and sorting the complete waste lithium ion battery, the obtained electrode material powder is treated to remove the organic binder. Finally, the cobalt-lithium compound powder was recovered by flotation separation according to the hydrophilic difference between lithium cobalt oxide and graphite surface in the electrode material powder. The technology of crushing flotation is simple, which can effectively separate the lithium cobalt and the carbon material, and the recovery rate of lithium and cobalt is high. However, the separation and recovery of copper foil, aluminum foil and metal shell are difficult because all kinds of materials are broken and mixed. And because the breakage easily causes the electrolyte LiPF6 and the H2O reaction to produce HF and so on the volatile gas to cause the environmental pollution, needs to pay attention to the crushing method. 2 Mechanical lapping method is to use the thermal energy generated by the mechanical grinding of the electrode materials and abrasive reaction, so that the electrode materials in the original bonding in the set of fluid lithium compounds into salts of a method. The recovery rate of different kinds of abrasive additives is difference, and higher recovery rate can be achieved: 98%,li recovery rate of Co recovery is 99%. The mechanical lapping method is also an effective method for recovering cobalt and lithium in waste lithium-ion batteries, the process is simpler, but the requirements are high, and it is easy to cause the loss of cobalt and the difficulty of recovery of aluminum foil. 2.2 Chemical method is the process of chemical reaction of lithium-ion battery processing methods, generally divided into fire-metallurgy and wet-process metallurgy 2 kinds of methods. 1 Fire metallurgy, also known as incineration or dry metallurgy, is to remove the organic binder in the electrode material through high temperature incineration, at the same time make the metal and its compounds redox reaction, in the form of condensation recovery of low boiling metal and its compounds, the slag in the metal using sieving, pyrolysis, Magnetic separation or chemical methods such as recycling. Fire metallurgy to the composition of raw materials is not high, suitable for large-scale processing of more complex batteries, but combustion will inevitably produce some of the waste gas pollution environment, and high-temperature treatment of equipment requirements are also higher, but also need to increase the purification and recovery equipment, processing costs higher. 2 Wet Metallurgy is a method of selectively dissolving the cathode material in the waste lithium ion battery and separating the metal elements in the leaching solution with suitable chemical reagent.
Hydrometallurgical process is more suitable for recycling chemical composition of the relatively single waste lithium batteries, can be used alone, can also be combined with high-temperature metallurgy, the equipment is not high, low processing costs, is a very mature treatment, suitable for small and medium-sized waste lithium-ion battery recycling.
2.3 Biological method of biological metallurgy is currently being studied, which utilizes the metabolic process of microbial fungi to realize selective leaching of metal elements such as cobalt and lithium. The biological method is low in energy consumption, low in cost, and can be reused by microorganisms, and the pollution is very small. However, the cultivation of microbial fungi requires harsh conditions, long culture time, low leaching efficiency, and the process needs to be further improved. 2.4 Lithium iron phosphate recovery partial unpopular in a variety of power lithium batteries, only lithium iron phosphate battery cathode material does not contain precious metals, but mainly by aluminum, lithium, iron, phosphorus and carbon components. For this reason, companies are not enthusiastic about the recycling of lithium iron phosphate. There are few targeted studies on the recovery of lithium iron phosphate batteries. The general treatment of lithium iron phosphate, the whole of the battery after mechanical crushing, the use of polar organic solvents NMP or alkali dissolved in the separation of aluminum, the remaining materials are LiFePO4 and toner mixtures. Into the mixture by introducing Li, Fe, P to adjust the mole ratio of the three elements in the material, and then by the ball mill, inert atmosphere under high temperature calcination can be LiFePO4 material, but compared with the first synthesis of lithium iron phosphate battery cathode material, the material's capacitance, charge and discharge performance decreased. The recovery of lithium, iron, phosphorus, carbon, and reuse of the anode material from the failed lithium iron phosphate battery is the recycling path. Though the study is small, someone is still doing it. such as Hong. A method was developed to extract lithium, iron, phosphorus and carbon by leaching the anode material of the failure lithium iron phosphate battery by phosphoric acid system, and by the method of high efficiency, low cost and 0 waste discharge. 3 Hydrometallurgy is the main application technology at home and abroad through the study of lithium ion battery recovery technology, we can see that the recovery rate of lithium ion battery using physicochemical method is low. The study of chemical method is universal, and its application is wide and relatively feasible. Although the biological method is environmentally friendly, it takes too long to be studied. Many studies on chemical methods show that the electrochemical performance of recycled materials obtained by single Fire metallurgy is not as good as that through Hydrometallurgy, but a large number of reagents are needed through single hydrometallurgy, which is not suitable for large-scale industrialized treatment. In comparison, Hydrometallurgy is one of the most important methods in the present extraction method, and acid leaching is the most significant part. The main aim is to transfer the target metal in the pretreated active substance into the leaching solution, which is convenient for the subsequent separation and recovery process. Traditional inorganic acids (HCl, HNO3 and H2SO4) have been widely used in leaching processes. However, in the leaching process will be accompanied by the production of toxic gases such as CL2, SO3 and NX and other environmental hazards. Therefore, in recent years, researchers have begun to pay attention to the role of organic acids (citric acid, oxalic acid, ascorbic acid, etc.) in the leaching process. Compared with the traditional inorganic acid, organic acid leaching can reduce the environmental pollution by two times while satisfying the high efficiency.
Typical wet extraction of the main steps: Pretreatment → acid solution leaching → leaching liquid impurity removal → separation extraction → element precipitation.
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