Recycling of used lithium-ion batteries is imminent

"Reuse of waste materials" is a new proposition accompanied by the rapid consumption of natural resources and the rapid increase of waste materials. Lithium-ion batteries (LIB) as an energy supply from mobile phones to electric vehicles (EVs) are increasing at an alarming rate. It is predicted that more than 11m tonnes of lithium-ion batteries will be scrapped globally by 2030, compared with less than 5 per cent of obsolete batteries that can be recycled
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. If the waste battery is not solved well, it will not only be harmful to the healthy development of human beings, but also destroy the natural ecological environment. Heavy metals such as Co, Mn and Ni can wreak havoc on soil and groundwater, and reactions between electrolytes (mainly LiPF6) and water molecules in the air produce harmful hydrogen fluoride (HF) gases. At the same time, the shortage of raw materials for lithium-ion batteries has also caused a more critical sense of urgency in the trend of recycling waste materials.
To facilitate the recycling process, many countries have enacted laws requiring battery manufacturers to collect and dispose of used batteries free of charge for consumers, so companies such as Umcore, Toxco, Batrec AG, Inmetco, SNAM, Sumitomo-Sony are now implementing tonnage recycling of waste LIBs around the world. In general, the recovery of waste lithium-ion batteries is a combination of physical and chemical means.
Physical means mainly include mechanical separation, heat treatment, mechanical chemistry and dissolution process, mechanical separation is a pre-treatment process, according to the different properties of used battery materials, such as density, conductivity, magnetism, such as the separation of waste battery materials, but the disadvantage of the process is that it can not be completely separated; To purify the gas produced by combustion, mechanical chemistry increases the surface area of the positive material through grinding technology, thereby increasing the leaching efficiency of the metal, and in general, polyfluoroethylene (PVDF) binders in electrode active substances hinder the leaching efficiency of the metal, using organic solvents such as N-methyl plutane (NMP), N, N-dimetethyl acetylamide and dimetethylate dissolved PVDF. In chemical means, due to the advantages of low energy consumption, minimal waste water and high recovery rate of high pure metals, researchers mostly prefer to use wet metallurgy to recover waste LIB, including acid/alkali/biofiltration, chemical precipitation, solvent extraction and electrochemical processes.
in the near future, the recycling of used batteries will be an urgent and arduous task. Therefore, Professor Vanchiappan Aravindan of the Department of Chemistry of the Indian Institute of Science Education and Research (IISER) published a review article entitled "Burgeoning Prospects of Spent Lithium-Ion Batteriesin Multifarious Applications", which for the first time discusses the reuse of used LIBs/recycled materials in various fields, including LIB, supercapacitors, oxygen reactions (ER), adsorption, photodynalysis studies, etc. This article was published in advancedEnergy Materials, a top international journal, at 10.1002/aenm.201802303.
the main content of the
1. The global overall demand for lithium batteries
LiCoO2 (LCO) has the advantages of high theoretical ratio capacity (137mAh/g), high volume capacity (1363mAh/cm3), good cycle performance and low self-discharge, and still dominates the LIB market. However, the high price of cobalt and the urgency of battery performance development in recent years have opened the way for the exploration of other new lithium-ion battery materials, including LiNi0.33Co0.33Mn0.33O2 (NCM), LiMn2O4 (LMO), LiNi0.8Co0.15Al0.05O2 and LiFeFE4 (LFP).
Asia, Africa, North America, South America and Australia provide the world's leading sources of lithium, of which South America holds 66% of the world's reserves, and countries such as Argentina, Bolivia and Chile account for two-thirds of the world's lithium reserves and have higher quality sources than the United States and China. Lithium prices have been on the rise in recent years, for example in China, when the cost of battery-grade Li2CO3 and LiOH soared by 190% and 196%, respectively, between 2015 and 2016 due to supply shortages. In addition, the salt water production method, which accounts for 50% of the global lithium supply, is no longer sufficient for the market, and the use of lithium in other applications such as aluminum smelting, glass and ceramics, air treatment, health products, industrial greases, medical applications, primary batteries and casting powders is leading to greater lithium barrenness in the future. In addition to lithium, shortages of other raw materials such as cobalt and nickel are beginning to emerge; In addition, Indonesia's ban on nickel exports has led to price increases of nearly 50 per cent, and
2. battery failure
there are many reasons for the exponential growth of used LIBs, whether due to the normal end of life, or due to other factors, such as battery expansion, internal short-circuit heating, deterioration of performance, electrolyte leakage and other reasons, have caused an immeasurable burden on recyclers. The solid electrolyte interface (SEI) layer formed on the negative surface during charge and discharge is one of the main reasons for the extended life of lithium-ion batteries, including Li2O, ROCO2Li, LiF, Li2CO3 and ROLi. The gas formed during the electrolyte decomposition increases the pressure in the battery, triggering heat to lose control, and when overcharged and over-discharged, the accumulation of the neural sprigs causes a short circuit between the electrodes and eventually causes the LIB to explode. In addition, the reaction between the electrolyte and residual moisture forms an HF that dissolves manganese, leading to positive degradation, and the structure of graphite becomes disorderly due to the severe impact of mechanical strain on the reversible capacity of the negative pole during charge and discharge.
3. Lithium battery waste materials
recovery of metals from used LIBs has been extensively studied, but most of these processes have significant disadvantages, such as high solvents, high gas emissions, complex cycle routes, chemical reagent consumption, etc., making these processes difficult to implement on an industrial scale; As a result, the researchers developed an effective leaching-resynthetic technique that avoids multistage step-by-step separation of metal ions by synthesizing materials from leachate, minimizing secondary contamination.
Generally speaking, the high purity of acid-immersed recrystable metal products can be achieved by short routes such as co-precipitation, sol-gel or solid gel, in the solution-gel method, the waste battery recovered positive material (NCM or LCO) dissolved in organic or inorganic acidic media, and added a certain molar ratio of metal ion leachate for a step co-precipitation to form a gel.
In the solid opposite should, first of all, the leachate as raw material, co-precipitation legal system prepared Co/Ni-Mn-Co pre-driven body, industrial recovery of Li2CO3 or LiNO3 and recycled pre-drive mixed calcination regenerative positive material.
3.1 NCM positive regeneration
compared the performance of NCM regenerative positive materials with two different organic acid leachates and found that shunbutyl diacin (NCM-Ma) has a higher processing capacity than acetic acid (NCM-Ac) because of the greater chelation capacity between NCM and shunbutyl diacin. In addition to organic acids, inorganic acids can have the same effect, such as H2SO4, the most commonly used leaching agent, although the use of sulphuric acid releases harmful gases causing air pollution, difficulty in recycling after leaching, and harmful effects on the environment, however, the cost of leaching lithium from inorganic acids is low.
it should be noted that impurities such as aluminum may exist in the process of separation from positive materials, which can also affect material performance when they reach a certain level.
Figure6. NCM-V2O5 positive material through different drying methods after a) cycle performance and b) multiply performance. The c) cycle performance of waste NCM and NCM-V2O5 materials, d) multiplied performance, e) cycle VM curve and f) AC impedance graph are obtained by spray drying.
High-performance positive materials, such as NCM-V2O5 positive materials obtained through solid-state reactions, can be obtained from waste lithium batteries and slag-containing waste liquids, and solid-state synthesis is the most widely used strategy for preparing polycrystalline solids from solid source material mixtures at higher temperatures.
3.2 LCO Positive Regeneration
At the beginning, much of the research focused on the separation of Li and Co in waste LCO materials, not on recycled active materials; During the regeneration process, the high concentration of positive active materials after mechanical and heat treatment is leached with nitric acid, and then LCO is produced from the leachate by sol-gel method, and the regenerated positive material has a discharge capacity of 140mAh/g after 30 cycles.
figure7. Regenerative LiCoO2 positive material at 25 degrees C electrochemical performance: a) 0.2 C, b) multiply performance.
through the system's organic acid leaching, chemical precipitation and solidification should be three steps, from the LCO powder can be extracted about 100% Li and 99.8% Co, to obtain the regenerative positive material at 0.2C current density after 50 cycles of discharge capacity of 105 mAh/g.
3.3 LFP positive regeneration
　　Figure8. Electrochemical properties of recycled LFP and waste LFP materials in the 2.0-4.2 V voltage range: a) Regenerative LFP and b) Regenerative LFP materials at different current densities from 0.1 to 20 C charge and discharge curves. c) The multiplied and circulating properties of the two materials at different charging rates. d) The cycling properties of the two materials at a 5 C current density.
in the process of exploring new positive materials, the representative material of olivine structure, lithium iron phosphate LFP, has been paid more and more attention by researchers, because of its excellent thermal stability and low cost, LFP has been widely commercialized in recent years. Phosphoric acid, as an immersion aid and sedimentation agent, can first synthesize FePO4.2H2O, and then recover Li2CO3 by carbon thermal reduction to prepare a recycled LFP-C positive material.
3.4 graphite/carbon negative
　　Figure9. a) Cycle performance of commercial graphite (CG), waste graphite (SG), recycled graphite (RG), amoear carbon coated graphite (AC@G) electrode at 0.1 C. b) AC@G performance of the electrode at 0.5 C. c) CG, SG, RG, AC@G multiply performance of the electrode at different current densities. d) RG and e) AC@G current charge discharge curve at 0.1 C. CG, SG, RG, andAC@G electrode at 0.1 C f) 100th charging platform and g) 100th charge and discharge platform.
There are usually two methods of regeneration of high-volume graphite negative materials, the first of which is to add waste graphite to glycol to form a mixture and microwave it off, and then to obtain recycled graphite by spray drying, which results in a regenerative negative material that can be obtained at 0.1 The discharge capacity of 409 mAh/g is obtained from 100 laps under the C cycle, and the second method is to prepare amoear-coated graphite through the sol-gel process, which can produce different kinds of carbon materials from waste graphite.
addition, recycled materials obtained from waste lithium-ion batteries can also be used in other applications, such as super capacitor electrode materials, electrochemical oxygen reaction catalysts, magnetic evaluation and other fields.
Figure10. a) AC impedance results for four electrodes (Al rGO-RT, SS rGO-70, SS rGO-RT, Al rGO-70). b) Four electrodes (Al rGO-RT, SSrGO-70, SS rGO-RT, Al rGO-70) cycle THE curve at a speed of 5 mV/s. c) The al rGO-RT electrode cycles the VU curve at different sweep speeds (5-125 mV/s). d) Four electrodes (Al rGO-RT, SSrGO-70, SS rGO-RT, Al rGO-70) at 0.5 A/g constant current charge discharge curve.
Figure11. a) Pure CC, Recycled Sharpstone MnCo2O4, Regenerative LiCoO2, Regenerative LixMnOx1, c-Co3O4, c-MnO2, c-RuO2 LSV Curve at 5 mV/s sweep. b) Current density - over-the - likely toe curve of various catalysts. c) The over-the -mass activity curve of various catalysts. d) The Talfield slope curve of various catalysts.
Figure12. a) CoCexFe2-xO4, b) CoCexFe2-xO4,c) CoCexFe2-xO4 (x s0.025, 0.05, and 0.1) sintering material hysteresis curve at room temperature.

From the perspective of high-value metal recovery and environmental protection, waste lithium battery recycling, recent research and development is undoubtedly ground-breaking, waste LIB positive materials recycled Li, Co, Mn, Ni, etc., not only for energy storage applications, but also for other environmentally friendly applications, such as supercapacitors, oxygen reaction and magnetic evaluation and other fields. In order to avoid secondary pollution when recycling, it is necessary to adopt some new strategies with acid-free leaching, short recovery steps, low material loss, high economy, low energy consumption and strong commercial feasibility, so as to promote the rapid development of industrialization. In addition, current research is devoted to regenerating NCM from a mixture of commercial positive materials LCO, LFP, NCM and LMO, both governments and businesses