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Recycling of spent lithium-ion batteries (LIBs) is of great importance for both critical metal supply and environmental protection. Although the physical chemistry is still focused on pyrometallurgy, hydrometallurgy and electrometallurgy, state-of-the-art recycling technologies are a trend that is turning towards being more material/energy efficient in line with the principles of green chemistry. For instance, selective recycling of specified metals and direct regeneration of battery materials are being trialled to develop short-cut processes that prevent secondary pollution generation and improve the atomic economy during the whole recycling process. In this review, a number of technologies for recycling spent LIBs are overviewed, especially at different recycling stages to stepwise recover battery materials. It is clearly understood that extraction of critical metals and subsequent regeneration of materials are only part of the recycling process, while pretreatment to obtain black mass powder from battery cells and pollution control, in view of the recycling process to minimise environmental impact, are also extremely important. Furthermore, green design of batteries, as well as process design in view of the whole life cycle of LIBs, are topping the list of the research which requires profound and elaborate efforts. It is expected that this review could provide a guideline for implementing green chemistry principles into spent LIB recycling and stimulate further discussions on improving the green degree of the process. [ABSTRACT FROM AUTHOR]

• Reuse of coagulation sludge for electro-Fenton process to treat wastewater. • Sludge-based electrode containing humic acid and iron salt coagulant was fabricated. • The whole life cycle environmental impacts of recycling processes were compared. • A trade-off between high electro-Fenton performance and low carbon emissions. To address aggravating environmental and energy problems, the harmless treatment and resource utilization of waste has become an inevitable choice. In this study, we report a highly efficient and low-carbon reuse approach of coagulation sludge waste based catalysts for electro-Fenton(EF) process to treat wastewater. The results showed that the relative amount of iron element in flocs increase gradually along with the growth in coagulant dosage, the main composition of floc is iron-HA complex and the interaction force acting between them was weak complexation. According to evaluation by electrochemical characterization, the selectivity of sludge electrodes for hydrogen peroxide in Oxygen Reduction Reaction (ORR) process was more than 40%. Without add additional Fe2+, the as-prepared cathode material is able to achieves 98.7% bisphenol A (BPA) pollutant removal from wastewater within 130 min treatment due to its highly active two-electron reduction of oxygen (O 2). Based on life cycle assessment (LCA) results, compared to traditional sludge disposal, the raw sludge used for EF could reduce fossil resource consumption by 73.7% and carbon emissions by more than 97.1%. The coagulation sludge applied in the field of EF in this paper proposes a novel and reliable way of collaborative treatment of sludge and sewage pollutants, and has certain guiding significance in environmental treatment and sludge recycling. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the rapid expanding of plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs) and electric vehicles (EVs), the projectfed demand for lithium-ion batteries (LIBs) is huge and might result in supply risks for natural lithium-containing reserves. After the service life, spent LIBs continuously accumulate in the market, and they are excellent secondary resources for lithium recovery. To alleviate resource shortage and to decrease potential environmental pollution caused by improper solid waste disposal, recycling of spent LIBs is motivated world widely in recent years. Previous studies have usually focused on the recovery of cobalt and nickel, which create high economic benefit. Recovery of lithium, however, has not been highlighted. In this article, state-of-the-art on spent LIBs recycling is discussed with emphasis on lithium recovery. In addition to understanding underlying mechanisms and physiochemistry features of various recycling methods, the possibility for industrial realization of each method is also evaluated. The complex processing steps limit the industrial implementation of hydrometallurgy-dominant methods, which usually reclaim lithium in the last step, resulting in a poor recovery efficiency of lithium. The pyrometallurgy-dominant approach is readily to scale up but lithium is lost in the slag phase. Therefore, the mild recycling (cleaner production) methods are recommended for future study since they take advantages of traditional pyrometallurgy and hydrometallurgy, and could decrease treatment temperature as well as acid/alkaline usage. Image 1 • More efforts are appealed to recycle electrolyte with respect to lithium recovery. • Lithium is usually the last metal to recycle in hydrometallurgical methods. • Pyrometallurgical methods should decrease lithium lost and energy consumption. • External field assisted pyro combined with hydro methods are promising. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A process to directly regenerate spent LiNi 1/3 Co 1/3 Mn 1/3 O 2 is demonstrated. • This process incorporates mechanochemical activation and solid-state sintering. • This method can restore the layered structure and improve lithium ion diffusion. • Secondary pollution will not be introduced in this regeneration process. • The economic viability of this method is better than a metallurgical process. Abstract The production of lithium-ion battery is around 9100 million sets in 2016 and is believed to further increase consecutively. This fact triggers the generation of spent cathode materials which contain metals of both valuable and hazardous. Their recycling corresponding to life cycle sustainability of lithium-ion battery has attracted significant attention. However, most technologies for recycling waste lithium-ion batteries are dependent on metallurgical based processes where secondary pollution is inevitable. This research demonstrates a process to directly regenerate LiNi 1−x−y Co x Mn y O 2 cathode material by incorporating methods of mechanochemical activation and solid-state sintering, which can restore the layered structure and improve the lithium ion diffusion without introducing extra impurities. By understanding the effects of sintering temperature, the optimal conditions for direct regeneration of cathode materials with obvious improvement on electrochemical performance can be obtained. As a result, this research proves the possibility of direct regeneration of nickel-containing waste cathode materials with minimized chemical consumption. [ABSTRACT FROM AUTHOR]

Recovery of valuable metals from spent lithium-ion battery (LIB) is of both environmental and economic importance. Acidic leaching usually encounters issues of low selectivity or slow kinetics with considerable secondary waste generation during further purification. In this research, a closed-loop process with improved leaching selectivity for recycling of spent LiNi x Co y Mn 1-x-y O 2 battery using weak acidic leachant was demonstrated. To obtain optimal conditions of the leaching process, the effects of acid concentration, solid to liquid (S/L) ratio, temperature and reductant content were systematically investigated. Almost all Co, Li, Mn and Ni could be effectively recovered into the solution while Al remained in the residue as metallic form, after one-step leaching. The role of reductant during leaching was further evaluated which was found to be critical for the leaching kinetics. It is clear that the addition of reductant could alter the rate-controlling step of leaching from the ion diffusion in the residue layer to the surface chemical reactions. With high selectivity against impurities, this research proposed and verified a process to recover high purity Li 2 CO 3 from the cathode scrap of LIBs, and more than 90% of the global recovery rate of valuable metals can be achieved. [ABSTRACT FROM AUTHOR]

To solve the recycling challenge for aqueous binder based lithium-ion batteries (LIBs), a novel process for recycling and resynthesizing LiNi 1/3 Co 1/3 Mn 1/3 O 2 from the cathode scraps generated during manufacturing process is proposed in this study. Trifluoroacetic acid (TFA) is employed to separate the cathode material from the aluminum foil. The effects of TFA concentration, liquid/solid ( L / S ) ratio, reaction temperature and time on the separation efficiencies of the cathode material and aluminum foil are investigated systematically. The cathode material can be separated completely under the optimal experimental condition of 15 vol.% TFA solution, L / S ratio of 8.0 mL g − 1 , reacting at 40 °C for 180 min along with appropriate agitation. LiNi 1/3 Co 1/3 Mn 1/3 O 2 is successfully resynthesized from the separated cathode material by solid state reaction method. Several kinds of characterizations are performed to verify the typical properties of the resynthesized LiNi 1/3 Co 1/3 Mn 1/3 O 2 powder. Electrochemical tests show that the initial charge and discharge capacities of the resynthesized LiNi 1/3 Co 1/3 Mn 1/3 O 2 are 201 mAh g − 1 and 155.4 mAh g −1 (2.8–4.5 V, 0.1 C), respectively. The discharge capacity remains at 129 mAh g −1 even after 30 cycles with a capacity retention ratio of 83.01%. [ABSTRACT FROM AUTHOR]

The recovery of waste lithium-ion batteries (LIBs) is an intensively studied worldwide because of environmental pollution and the risk of undersupply of a strategic raw material. Traditional technologies have poor selectivity for lithium recovery from waste LIBs. Metallic Ni, Co, and Mn are usually recovered by leaching, precipitation, and solvent extraction. These recycling methods are costly and have a long recycling route and high potential for secondary waste generation. In this paper, a mechanochemical activation approach was proposed for the selective recycling of lithium and recovery of Ni 0.5 Mn 0.3 Co 0.2 (OH) 2 from spent LiNi 0.5 Mn 0.3 Co 0.2 O 2 batteries. The leaching efficiency and Li selectivity were found to be 95.10% and 100%, respectively. The structure of Ni 0.5 Mn 0.3 Co 0.2 (OH) 2 was investigated using various characterisation techniques. The selective reaction mechanism of mechanochemical activation was identified. High-purity Li 2 CO 3 (99.96 wt%) was obtained. Electrochemical tests showed that the performance of Ni 0.5 Mn 0.3 Co 0.2 (OH) 2 was comparable to that of a commercial oxygen evolution reaction catalyst (IrO 2). This research demonstrates an effective and shorter route from waste to a functional material during recycling spent LIBs that incorporates the principles of green chemistry and shows great potential for practical application. Image 1 • The high leaching efficiency and selectivity of Li are obtained using. Mechanochemical reaction. • The selective reaction mechanism of mechanochemical activation is identified. • The high-purity Li 2 CO 3 is recovered. • The recovered Ni 0.5 Mn 0.3 Co 0.2 (OH) 2 exhibits high OER activity. [ABSTRACT FROM AUTHOR]

Recycling of spent lithium-ion batteries has attracted wide attention because of their high content of valuable and hazardous metals. One of the difficulties for effective metal recovery is the separation of different metals from the solution after leaching. In this research, a full hydrometallurgical process is developed to selectively recover valuable metals (Ni, Co and Li) from cathode scrap of spent lithium ion batteries. By introducing ammonia-ammonium sulphate as the leaching solution and sodium sulphite as the reductant, the total selectivity of Ni, Co and Li in the first-step leaching solution is more than 98.6% while it for Mn is only 1.36%. In detail understanding of the selective leaching process is carried out by investigating the effects of parameters such as leaching reagent composition, leaching time (0–480 min), agitation speed (200–700 rpm), pulp density (10–50 g/L) and temperature (323–353 K). It was found that Mn is primarily reduced from Mn 4+ into Mn 2+ into the solution as Mn ( NH 3 ) x 2 + while it subsequently precipitates out into the residue in the form of (NH 4 ) 2 Mn(SO 3 ) 2 ·H 2 O. Ni, Co and Li are leached and remain in the solution either as metallic ion or amine complexes. The optimised leaching conditions can be further obtained and the leaching kinetics is found to be chemical reaction control under current leaching conditions. As a result, this research is potentially beneficial for further optimisation of the spent lithium ion battery recycling process after incorporating with metal extraction from the leaching solution. [ABSTRACT FROM AUTHOR]

Critical metal sustainability is a worldwide issue whose extraction relies on hydrometallurgy mostly. The significance of metal ion species evolution in critical metal hydrometallurgy-extraction has got more and more attention. Here, the importance of the metal ion species during the whole vanadium recycling process has been evaluated quantitatively for the first time. Metal ion species as the key parameter was investigated through efficiency, material and energy accounting, and emission accounting to illustrate the effect of the metal ion species, which donated as ion species contribution (ISC). Specifically, 7 types of vanadium ion species were assessed in the process of V 2 O 5 production from leachate, including H 2 VO 4 −, HV 2 O 6 −, V 4 O 12 4−, H 2 V 5 O 14 −, V 10 O 28 6−, HVO 4 2− and VO2+. The results demonstrated that different vanadium ion species were closely related to recovery efficiency and purity, and they impact separation section, materials and energy consumption mostly in whole process. Consequently, V 4 O 12 4− occupied the highest ISC which was 1.11 times than V 10 O 28 6−, 1.37 times than VO2+ and 4.85 times than H 2 VO 4 −. Correspondingly, control of V 4 O 12 4− as dominant species appeared to be the most potential in the vanadium extraction process, which showed the feasibility of whole process optimization. With this research, ISC can help to point out dominant ion species in holistic critical metals supply chain, thus promote sustainability of critical metals in a new perspective. • Evaluating in detail the contribution of ion species to the whole V 2 O 5 production. • Covering comprehensive indicators related to ion species evolution. • An effective method for ion species regulation in critical metal resources recovery. [ABSTRACT FROM AUTHOR]

The essence behind metal solvent extraction is the interaction between metal species and organic extractants. Aqueous metal species tuning at the molecular level is critical to improve the extraction efficiency and selectivity of the target metal. Herein, we demonstrate a quantitative metal species tuning strategy which is capable of extracting the most critical metals (e.g., V, W, and Mo) in extraction systems constructed by amines. We reveal the superior activities of V 4 and V 10 species among various V and Cr species by calculations and experiments. In addition, the contribution of various V n species was quantitatively evaluated via Ion Species Contribution Evaluation (ISCE). Our tuning strategy is rationally designed by bridging species characteristics and routine aqueous conditions with extraction activities. Consequently, a three-dimensional model of V and Cr solvent extraction is established for the prediction of reaction regions, and the reactivities of nearly 20 kinds of typical metal species are compared and predicted. Our strategy serves for industrial solvent extraction, and may provide inspiration for the traditional hydrometallurgical revolutionary. [Display omitted] • Metal species tuning is significant for improvements of critical metal recovery. • A quantitative tuning strategy of metal species for solvent extraction is designed. • Superior activities of V 4 and V 10 species in extraction is confirmed and evaluated. • Extraction activities of several metal species (V, Cr, W, Mo) by amines is predicted. [ABSTRACT FROM AUTHOR]

[Display omitted] • The paired electrolysis reduces energy consumption in the recycling of spent LIBs. • Synchronously recovering Co2+ as cobalt metal and synthesizing persulfate. • Simultaneous desalting in the recycling process of spent LIBs. The application of electrochemical methods on the recycling of valuable metals from spent lithium-ion batteries, and the removing of pollutant from wastewater by persulfate have attracted widespread attention in recent years. However, high energy consumption resulting from side electrochemical reactions constrains its application. Herein, a paired electrolysis method was designed to achieve the recycling of valuable metals from the spent LIBs and the synthesis of persulfate synchronically. In the process, high purity cobalt metal (>99.9%) was obtained from the leachate (catholyte) of the spent LIBs, and valuable persulfate were synchronically synthesized anolyte through a diaphragm electrolyzer. The prepared persulfate was directly thermally activated for pollutant degradation. Two important synthesis process are conducted in one step. About 30% energy consumption is reduced through paired electrolysis to produce valuable products of equal quality and the cathodic current efficiency is also enhanced about 4% compared with the single cobalt electrolysis system at same stage. Additionally, Li+ is recycled as Li 2 CO 3 through precipitation from the electrolyte. As a green method, paired electrolysis will own a wide application prospects in the waste recycling and other hydrometallurgical fields because of low energy consumption and high valuable products. [ABSTRACT FROM AUTHOR]