3.1 Annual distribution of publications and publication sources
From 2001 to 2021, 4,810 records were collected by manual screening and proof reading in Scopus database. Figure 2(a) shows the relative contribution of articles, reviews, meeting abstracts, proceeding papers, and other types of documents produced. The highest number of publications were in engineering about 40.2%, energy 18.4%, computer science 9.3%, environmental science 8.6%, and social science 5.6%, and least publications about 0.1% in nanoscience, nursing, and veterinary journal.
Figure 2(b) shows the annual publication of EVBs from 2000 to 2021. In this graph both linear and exponential trend lines illustrate the consecutively increasing the number of publications in ascending order. Between 2001 and 2011, there was a steady rise in the number of publications concerning employed EVBs, according to the study. While from 2012 to 2018 was the quite similar number of publications. On the other side, a slight increase from 2019, but not exponentially.
This trend can be described in part by the point that some countries introduced recycling laws for the metals sector between 2011 and 2012. Due to the recycling technologies of EVBs, academics became more interested in the topic. As a result, the number of publications has grown steadily over time, reaching 472 in 2020. Despite the fact that the data for 2021 is still being updated, 437 articles were recorded yet. This suggests that the Li-ion recycling market is expanding and that ongoing research into these related technologies is becoming more and more efficient.
3.2 Geographical distribution
The managed data was imported into VOSviewer software in order to examine and comprehend the condition of wasted Li-ion batteries & recycling technologies research in various nations throughout time. The findings are shown in Fig. 3, respectively. China, with 645 scientific documents, has the most publications among the participating nations. The second and third places, respectively, went to the Germany with 635 publications and the United States with 634 publications. Italy with 306 documents and UK has 249 publications securing fourth and fifth rank, respectively. India, Japan, France, Netherlands, and South Korea 214, 204, 164, 118, and 106 documents, respectively, were ranked 6th to 10th place, respectively.
Currently, the advantage of batteries are produced in Asia, particularly China’s massive dominance supply of raw material, manufacturing of battery parts, material refinery, and cell productions. The WSJ claims that China alone presently manufactures 75% of all lithium-ion battery cells.
That’s why most of recycling firms are placed in China with the help of manufacturing partner companies. According to the Ph.D scholar (power battery and materials analyst)“Shalu Agarwal from Yole”: He says, “ Most automakers are currently comparing various recycling businesses and looking for the finest battery recycling partners for their companies, since they are required to recycle their end-of-life batteries (Sudheesh & Gochhait, 2020), such as the alliance between Honda and SNAM and the collaboration between Audi’s and MG Motors and Umicore. One of the most crucial evaluation criteria is the environmental criteria connected to the recycling technologies (pyrometallurgical, hydrometallurgical), various recycling stages, recycling capability, and chemicals used”.
Moreover, U.S.A and some European countries such as Poland, Switzerland, Germany, France, Norway, and U.K established the recycling plants as well. For instance, redwood Materials led by Tesla co-founder J.B. Straubel said, it will build its battery materials manufacturing (100 GWh per year of cathode active materials), and recycling facility in the United States for one million EVs by 2025.
Some recycling companies such as in China Brunp, Huayou Cobalt, and GEM are functionally operating. While, in U.S.A and Europe, Umicore group (UMICY), American Battery Technology Company (ABML), Heritage Group, Akkuser, and Accurec companies are functional. The Major LIBs Recycler in North America is retrieve Technologies Combines company with Heritage Battery Recycling, while Chinese recycling businesses are in a better position. They receive a lot of governmental assistance, and have easy access to the vast amount of recyclable materials.
German government strives for establishing Germany as a lead for the recycling of Li-ion EVBs in Germany and Europe. For these purposes planning responsibilities for starting a recycling network for LIBs and provide the specific location area, recycling technologies, incentives, facilities, policies, benefits, flexibility in laws are providing by the federal and local government. Thus, Germany set the good example by investment into new, specialized small and mediums-size recycler companies.
3.3 Parameter Analysis of most prolific Author, Institution, and Journal
A journal has more influence if it publishes more papers and receives more citations. This section examines the most relevant characteristics in the most productive journals on used LIBs, as seen in Fig. 4. (a). The journals shown in the figure such as World electric vehicle journal, Energies, and Transportation research part D: transport and environment, suggesting that wasted LIBs has cover different research fields separately and received attention from several environment-related fields as compared to other journals.
The journal analysis graph is made by VOSviewer software for check the most successful journals on EVBs and assess their most important research factors. The different colors and groups clusters shows the different research collaborations interest.
Total citations and TLS attribute are two of the basic weight attributes to analysis for a given published papers. The total number of citations and TLS represent the quality and quantity of the published articles in a journal. Moreover, the importance of journals and a researcher's performance are judged on the number of publications, citations as well as they appear. For example, a total of 174 articles, 498 citations and 6 TLS, Journal of “SAE technical papers” is the one with the greatest journal for spent Li-ion batteries and demonstrate that it is more influential than other journals in this field of study.
The 2nd journal, “World electric vehicle journal”, has a total of 85 articles 858 citations, and 52 TSL on wasted LIBs, “Energies” is the 3rd journal in this arrangement, higher the citations and TLS which demonstrated that they are reliable journals for article publications related to recycling waste Li-ion batteries research. In addition, the performance of other journals can be asses in the figure.
Collaborating shares resources across academic institutions and researchers, fosters collaborations, identifies cutting-edge research, facilitates problem-solving, introduces innovations in research, enhances research methodology, and facilitates the exchange of ideas and research. We may discover the concepts of the most cooperative institutions in SLB usage and recycling technologies of used LIBs by institutional and author analysis, as well as how much they have engaged with one another individually or collectively. Additionally, we can discover whether certain institutions have chosen to focus on this issue or whether government financing or a chance from private sectators was involved.
For institution performance in figure, 4(b) we select the criteria for co-authorship of organization or institutions minimum number of publications is five and at least four citations collectively we extracted the ten top institutions which meet this criterion. unfortunately, there is no collaboration among these institutions, they might be with other institution in the whole data. Higher number of publications and citations of institutions present the higher research interest in than other institution. So, State key laboratory of automotive safety and energy, Tsinghua university come on first position with 18 publications and with 1052 citation, secondly IEEE comes on second with 10 publication and with 177 citations. Thirdly, Fraunhofer Institute for Systems and Innovation research, Fraunhofer ISI, Karlsruhe, Germany, and Polytechnic di Torino, Italy with equal seven publications and different citations 175 and 27, respectively. While other remaining institutions has published same five articles and gained lower than 30 citations on this publication so far.
In Fig. 4(c), there are different four-color groups brown, purple, green and yellow shows the author collaborations and cited the articles by other authors. The start describes the number of published document and yellow triangle describe the total number of citations gained by whole publications. Li y has highest 36 publication and his papers cited 589 times by other authors, on recycling technologies of Used LIBs. Second author whose name is “an mierlo j.” has 35 publications and 80 citations but here is no author who collaborated and cited his papers, might be his papers cited by other authors in our research data or other researchers, that’s why he is alone in his group. Thirdly, Li J with 33 publications and 44 citations he scored very least citation may be the low quality of research or not wide assess of his research for other researchers. Moreover, Wang z has highest citation 1707 on 23 publications which show that wang z has innovative and good research stream. Hence, we can assess other remaining authors’ role and performance in the field of recycling technologies of used LIBs.
In conclusion of this section all journals, institutions and authors publication show the importance of research on SLB and end life using of EVBs. The segments of the Journal illustrate the most creative journals on spent LIBs besides evaluates their utmost significant research impact.
The journal section lists the publications with the highest productivity based on spent LIBs and assesses their biggest research effect.
While the institution analysis stated the three most important and typical goals of study among the institution, whether the institution is studied (exploration, description, and explanation) individually or collectively. Finally, the authors analysis concluded the similar research intertest, help and communication channel among other authors, importance of research effort, recognitions mechanism for researcher and institutions
3.4 Keyword co-occurrence analysis
It's vital to go deep into each document and identify the key terms in order to confirm the subject matter and core themes of study on wasted LIBs. This study is crucial for finding patterns in developing topics and hotspots that might be relevant for areas of research, development, and innovation in the domain of wasted LIBs. Out of a total of 4,810 articles, 28,860 results were produced by the analysis of keywords connected to wasted LIBs.
Furthermore, we extracted the most famous and closed to our research keywords on wasted LIBs about 178 to 200 words which reached the limits focus on research direction. Among them, we divided our data in main two parts 2001 to 2010 and 2011 to 2021, and then this data further classified on the behalf of their terms and conditions for understanding of the research trend, progress, development, and research gap. Mainly research information data or term types from 2001 to 2010 of EVBs: “battery technology”, “theory”, “cost and benefits”, “energy analysis”, and "chemical component analysis mostly has been used.
The first segment of Keywords section from 2001 to 2010, show that researchers, scholars, companies, and research organizations mainly focus on Research and development (R&D) of EVBs, which is initial stage of improvement and development in different sections of E-car battery parts. Mainly R&D cover the three parts or types of research: basic, applied, and development research.
Basic research is experimental or theoretical work started primarily from: theory, modeling, comparative study, and control scheme to acquire new knowledge and technologies for bring improvement and innovation in the research field without any particular application or use experimental tools. Some examples of R&D are energy storage capacity analysis, battery design and weight analysis, life cycle assessment, and end life assessment etc. While in R&D the applied research discusses to scientific study and research that seeks to solve and find the practical solution of problems.
For instance, the usage of toxic substances such chemicals, metals, electrolytes, binders, and polymers results in the toxicity of LIBs; each of these substances is risky and endangers the environment, the ecosystem, and human health. Researcher needs practical solution to find alternative solutions for save environment and human health.
Another classification of research direction during 2001 to 2010 is battery technology which included some important keywords for instant, battery lifetime, battery capacity which is basically depend on the battery components such as cell, electrolyte, anode, and separator. Furthermore, battery technology and performance also directly and indirectly interconnected to the chemical component such as, Li, C, Ni, Hg, H+, graphite, Zn, high density manganese oxide analysis of the LIBs for batter, storage, performance, and lifetime of the battery.
In section 2011 to 2021 the mainly research trend changed from basic and applied research to development research. The definition of developmental research is "systematic study of creating, producing, and assessing products that must fulfill standards of internal consistency and efficacy of LIBs research."
The core research keywords in this section which are mainly focusing on development research are following: “components and material”, “size and cell engineering”, energy storage”, “second life use”, “stationary use”, “recycling technologies”, “impediments of recycling”, “Environmental benefits”, “pollution control”, “role of countries contribution”, and “economic benefits”. are all crucial keywords in EVBs research field.
It has been seen that in last some years scholars and researchers paying more attention R&D in second life and recycling of LIBs for recovery of Li- and other precious metals as well as the minimize the burden of waste batteries because it is spreading the pollution and very dangerous for our environment. Recycling saves resources, promotes the economy, and creates employment. Sustainable Materials Management (SMM) emphasizes the productive and sustainable use of resources throughout their entire life cycle, while minimizing environmental effects and preventing waste and increased exploitation of natural raw materials.
Moreover, there are some impediments during recycling of LIBs for instance, removal of batteries from vehicles, material collection issues, transport cost and logistics, recycling policy and regulatory issues, fire risk during transfer and disassembly, and design for recycling. During transportation some issues of transfer rules and policy regulations such as permission from one place to another place, risks of over loading, battery leakage, un complete wrappings, toxic chemical leaking cause of fire. the transportations problem can be solved by providing soft policies, rules, and adopting safety precaution.
A cost-benefit analysis compares the expected or estimated costs and benefits (or opportunities) connected with a project choice to evaluate if it makes business sense. Cost benefit of recycling used LIBs helps to calculate the gap between new and recycled product that it is profitable and beneficial for the government, market, company, and consumers.
Many developed countries such as the U.S.A, China, and European countries: Germany, France, Italy, Denmark, Hungary, Switzerland, and Poland are taking interest and good incitive for recycling of waste LIBs. Moreover, these countries are providing basic facilities, convenience, policies and regulation issues, and opportunities for recycling companies and organizations.
The majority of recycling industries are currently found in China, including Brunp, Huayou Cobalt, and GEM, While Umicore, Akkuser, Accurec companies found in Europe
Chinese recycling businesses have an advantage because of wide funding and support by the government. So, the majority of recycling businesses are steadily expanding their recycling capability to manage the growing amount of end-of-life batteries.
Currently, there are some valuable and convenient recycling technologies such as pyrometallurgical, hydrometallurgical, bio-hydro metallurgical, electrochemical are being used by recycling companies, organizations, and researchers. These recycling technologies are being briefly discussed in section (3.5 recycling process) their steps, efficiencies, and advantage in details as well.
Metals from used LIBs were also extracted using citrus fruit juice, which includes citric and malic acids as well as certain citrus flavonoids. These flavonoids have the ability to lower the valency of metals. Another recent study discovered that used fruit peels may be utilized as a green reductant to recover metal from used LIBs. In recycling procedure of batteries, the carbon, harm full gases, heat, water and air, health safety, respiratory, production hazardous waste are generated.
A LIB's parts have value and may all be recovered and used again. Currently, the majority of recyclers just recover the metals. Resulting, they offer significant economic advantages by reducing the requirement for additional mineral extraction and boosting resilience against supply and vulnerable threats.
In the fuzzy or game theory, we estimate and calculate those which components of the battery will be profitable and safe during the recycling, and emissions are mostly caused by the power utilized in the recycling process as well as by the recycling of the materials in the electrodes and container.
The keywords co-occurrence analysis concluded the whole research on EVBs, how to move from basic research to development research during last 20 years. Researcher and scholars pay attention the improvement on battery internal structure (anode, cathode, electrolyte, etc.), external structure (size, body cover), storage capacity, first life-time use age, environmental and economic benefits, second life time to end life time, recycling technologies, and recovery of metals.
3.5 Second life of used EVBs
Second life battery (SBL) are used for domestic and commercial energy storage purposes for short term peak power, minimize the chance of power outages and secondary services (Burggräf et al., 2020). Some of the applications are mentioned in Fig. 6. The storage of solar, wind, and tidal energy, this energy storage system can be used where there is no direct access of electricity from the gride station such as top of the mountains and long-distance houses and cabins (Zhang et al., 2020). Moreover, operation of protective devices, emergency lighting at generating stations, e-bikes and ricksha (Schulz et al., 2020), for starting ignition and lighting of automobiles, aircrafts, steam engine and diesel railways train (Quan et al., 2022), as well as small cars and train which run in the picknick parks etc. It might be dangerous to repurpose an EVBs at home. The battery packs are large and can explode if they are damaged (Lai et al., 2022).
Some economic benefits of application of SLBs to prevent the mining the natural resources, reinforces country economy and produces jobs. Apart from the economic perspective, the use of SLBs will also have an impact as of an environmental viewpoint (Zhu et al., 2021b). The concept of zero waste management is applied by using SLBs to prevent the creation of waste as well as, will reduce the demand of environmental harmful material extraction which need for new batteries, water for mining (Gao et al., 2020), CO2 emission and electricity for cell manufacturing (Wang et al., 2022). Also a second life batterie also a sustainable business opportunity (Miao et al., 2019). The cost of a 2nd reused battery is approximately $50/kWh, compared to $200–300 for new battery construction today, and could stay competitive at least until 2025, when the price of a new battery is expected to reach $90/kWh (Tao et al., 2022).
(1) Advantages and disadvantages of second life batteries
some advantages of application of used batteries are half of the price of new batteries, new companies established for reconditing of discarded batteries resulting new jobs opportunities creates, increases the growth of the recycling companies, circular economy and zero waste concept, less demand of new batteries resulting less mining of raw material, mining and CO2 emission.
while some disadvantages such as no standard and guarantee of the battery (Koh et al., 2021), new qualified and experienced jobs required that will impact on the cost benefits of applications of used batteries (Dai et al., 2019), the reconditioning and assessment will require, SLBs will influence the cost-benefits of new batteries (Koroma et al., 2022).
(2) Challenges of second life batteries
Notwithstanding the potentials advantages of the SLBs, the implementation needs to overcome some obstacles and challenges: Regarding implementation, standards and automatization will speed up their industrialization, having a positive contribution in terms of safety and cost. As explained earlier, the dismantling process will require highly qualified professionals that can have an impact on the cost-benefit of SLBs (Zackrisson et al., 2010b),. In addition, the battery comes in different shapes and forms together with different voltages and chemistries. This is a real challenge for the reconditioning process and might require additional assessment. Thus, it can further increase the reconditioning cost.
The finding a similar cell and matching the good battery together is an important factor for the performance and lifespan of SLBs (Canals Casals et al., 2019). The commitment is that the full implementation of the SLBs impacts the price of new li-ion batteries and their cost-benefit balance positively. Moreover, the critical challenge is to extend the life cycle of these SLBs more than 5–10 years in response to what the customer may have in mind compared to new batteries (Casals et al., 2019).
3.6 S-Curve analysis of treatment technologies
S-Curves are used to visualize the progress of present treatment technologies over time. They plot either cumulative research, based on time mean years, or publication over time. In S-Curve maturity means any project or research pass through the emerging, initial, or growing stage to developed, grownup, advanced or progressive stage, and this maturity phase make the upper part of the S-cure.
To simulate the overall trend of treatment technologies of used LIBs, we utilized the S-curve. To additional discover the certain treatment mechanisms progress and movement, we divided the treatment technology into four Hydrometallurgy, Pyrometallurgy, Electrochemical, and Biometallurgy technologies. Figure 7 depicts their progress trends.
The S-curves generated from the publications which demonstrated the effectiveness of the technologies in hydrometallurgy, pyrometallurgy, electrochemical, and biometallurgy. The maturity stage of treatment approaches was reached in 2018, 2019, 2020, and 2024, respectively. Biometallurgical technology is showing very slow as compare to other three technologies, because this emerging technology and nonfunctional (open loop) at industrial level cause of slow process of extracting of metals. The whole publications of hydrometallurgical treatment technology were 1361, higher than pyrometallurgical (1114), electrochemical (969), and biometallurgical (743).
Hydrometallurgy and Pyrometallurgy treatment technologies would significantly longer time period prior to deteriorating and a bigger possibility for innovation and development. In Hydrometallurgical technology the direct extraction steps and classical approaches of LiOH and Hypothetical research and innovation might advance Li2CO3 in 5 to 10 years. While Pyrometallurgical technology’s main cause is emit or GHGs and required additional steps for extracting of pure Li. So, it is seeing that researcher start to more focus on other technologies for using at commercial and industrial level instead of using this technology.
Otherwise, hydrometallurgical treatment technology is nearing saturation and will mature around 2023-27, while pyrometallurgical and electrochemical will mature around 2025-30.
Mutually S-curve and publication flow demonstrated the reputation and status of hydrometallurgical treatment process. Hydrometallurgical treatments technologically advanced quickly in the previous ten years, hydrometallurgical treatment process had the advantages of high proficiency, cheap price, environmental friendly and suitable process, and have played a vital part in used LIBs recycling industry.
In comparison to pyrometallurgy and electrometallurgy processes, hydrometallurgical treatment methods have matured quickly due to the researchers' intense focus and enormous number of studies. However, further study on biometallurgy is required for a quick process and functioning at an industrial level.
3.7 Recycling Processes of LIBs
Mainly treatment of Li-ion batteries consists of two main parts disassembly and recycling. Disassembly or pre-treatment is a most important and critical step before recycling in which massive batteries packs are separate from the vehicle body, because it is very heavy and connected to the vehicle with electric wires. The separation of battery from vehicle is called disassembly.
Treatment or recycling means not to recover of material but also keep the good quality control by using high recycling technologies (Roy, Cao, et al., 2021). However, batteries recycling all are not the same. Four different processes are following: (1) pyrometallurgy: cobalt, nickel and copper recovery only, graphite and solvents burned, high energy requirement (1,500°C), Loss of lithium in slag is expensive, toxic-waste by product also increase the carbon footprint. (Horeh et al., 2016), (2) hydrometallurgy: high recovery rate, Co, Ni, Cu, and Li is recycled (Arya & Kumar, 2020). Moreover, Options for manganese and graphite recycled at moderate temperature, low energy requirement, no toxic waste by-product. However, expensive initial investment, rigid procedures, and substantial byproduct waste are needed. Both approaches need a rise in lithium output, either in terms of product or cost savings (Biswal et al., 2018).
(3), Electrochemical technology is a alternate for the extraction of Li and metals. The main benefits of this technology are that it doesn't harm the environment, is flexible, saves energy, is safe, can be used selectively, can be automated, and is cheaper than other technologies (Kato et al., 2014). (4), Biometallurgy or bio-hydrometallurgy technology as an substitute technique of removal and recovery of treasured metals than other treatment technologies (Hu et al., 2020). This technology is more feasible than traditional ones since it can offer a greater recovery yield even at low metal concentrations. The bioleaching process can function with a simpler setup, less energy and water use, and less toxic byproducts. Currently, this technology not functional at industrial scale, due to lowest technology readiness level, and slow kinetics.
3.7.1 Pre-treatment methods of wasted Li-ion battery
In pre-treatment process firstly, the whole electric wires must be unplugged and disconnected, Secondly, separate the pack by using chain pulley up and put in the yard for further separation. There are some problems for disassembly of batteries are following: high voltage and wiring, different size and shapes of battery and Evs, pack formations and settings, fixings and tooling essential, head of bolts and position not always the same. Cells trapped together in modules with gums chemistries not always identified, Deficiency of labelling and identifying symbols related of battery conditions and life (Burchart-Korol & Folęga, 2020).
Some precautions and skills are needed to take things apart, like high-voltage training and safe tools to keep the battery pack from short-circuiting. The qualified employees are required for such dismantling of weight and high voltage of electric battery. This is a difficulty for an evolving sector with a skills gap. In addition, computerize robotic system can be used for disassembly of battery pack for remove the risk of human employs, as well as reduce the cost. this system is economically feasible for automotive industries (Brückner et al., 2020).
After dismantling of battery from the Evs there are mainly three processes (a) Mechanical treatment, (b) Solvent treatment, and (c) Calcination treatment for extraction a key intermediate product, here is so called “black mass”. This black mass is a product of used batteries, this yield is black mass. These all three different processes and their steps can be seen in Fig. 8. These three techniques have different economical, and environmental benefits. Black mass conation of Co 6%, Mn 6%, Ni 20%, Li 3.5%, but also carbon and many contaminants such as plastic etc. C 40%, F 3%, P 0.5%, Cu 2%, Al 2%, Fe 1%, Zn 0.1%, Ca 0.1% (Gaines et al., 2018). Chemical treatment is necessary to remove the valuable metals from “black mass”. This black mass contains active material of the battery. they also include carbon or graphite from the anode and the valuable material from the cathode (Ellingsen et al., 2014).
Here we particular focus on Li, Ni, and Co metals. As we can see there is a lot of other products. we have a large number of contaminations with other metals this is due to the fact that sorting step is not overly precise or clean. In addition, we have elements such as Fluorine it is used in the binder that is needed to assemble battery and it’s also the part of electrolyte. you can imagine we cannot take that material and turn it into the new battery no instead the black mass will have to be processed chemically in such a way as to enable meaning full separation and recycling of individual materials.
3.7.2 Hydrometallurgical process
The pre-treat the black mass apply heat treatment to it. organic component destroyed as it a part of fluoride (J. Peters et al., 2016). In the second step metals are leached with the help of H2SO4.H2O2 and as result you have sulfuric (H2SO4) solution containing all those metals that can be further processes and metals can be processes individually (Majeau-Bettez et al., 2011). The chemist among you may remember the universities studies the underlying the processes and steps. throughout the end of the chain, we picked out the cathodic material Co, Ni, and at the very end Li. Now this process chain up to Co, and Ni exist in many places around the globe namely in metal refinery. This is how Co, and Ni from the mine treated and purify as well. there are a lot of technologies around the world reliable testing and trail processes that we can base on the processes. But for the Li is extracted in the as a carbonate which however, not easy to solve but it is best way to precipitating Li from our H2SO4 solution (Moazzam et al., 2021). If you precipitate Lithium carbonate (Li2CO3) you have 10tone of sodium sulphate (Na2SO4) and other by product for each tone of lithium. So, this is not very efficient, but if you use this process to produce cathodic material all ready to lower the carbon footprint about 25%, so this good for researcher, environment and customers in automotive industry because they keep looking out waste improvement via carbon footprint (B. Liu et al., 2019).
In the classical approach you have finally Li2CO3 and Na2SO4 as by product. but modern batteries material does not want use Li2CO3, you want lithium hydroxide (LiOH) to make a modern car battery. lithium carbonate can be converted into LiOH but this mean yet additional step and investment (Roy, Madhavi, et al., 2021). it’s mean additional chemical required that mean your carbon footprint is increases. our research tackles this problem, and we have developed the processes to extract the LiOH directly. The side effect you can extract Li first at the very front of the chain and this give the more flexibility in the building of value chain. This is what processes look like in the figure. 9 which are divided into two parts. In the first step we mobilize (active) Li in the “black mass” while, in the second step we leach the Li selectively in its format of LiOH. what remain is a black mass containing everything that was as before minus Li. This black mass can then be put into hydrometallurgical plant for further isolation of Co, Ni, and other metals. Due to this direct LiOH extraction processes Sodiumsulphate (Na2SO4) formation is avoiding completely and we save the additional steps required to turn Li2CO3 into LiOH. By picking the Li out at the very beginning we have the chance of coupling this process with classical refinery processes and this is turn in table enables us to build the value chain in simplest easy way and flexible way of reducing the carbon footprint via classical hydrometallurgical considerably. It is quite and simple as its sound the devils in the details. We do not want to produce just any kind of (LiOH); we want to have battery grade Lithium hydroxide (Yun et al., 2018).
So, we have to remove contaminations to 2ppm level, because if we leave the contamination the material the quality, operations, and the life of the battery will be impaired and that’s a no go (Leskes et al., 2013).
we have to do something about these if chemist want to purify it, the chemist crystalizes this LiOH crystalize carefully out of the solution and contaminants they back in the solution. it will look very well for most elements that we see here but it doesn’t work well for Fluoride (F). Because F can be removed by crystallization but on the certain point (Efremova et al., 2022). From this point onward the F is made Parten parcel of the crystal structure of LiOH, then it’s more F than we will see in our battery materials (Needell et al., 2016). There are some challenges for lithium recycling required. Yield inadequate (high adjustable cost). Insufficient Li quality (low value) (Jiang et al., 2017).
3.7.3 Pyrometallurgical process
In pyrometallurgy, reactions take place in the cathode and anode, which makes Li soluble in water and allows organic material to be removed by evaporation at high temperatures (Windisch-Kern et al., 2022), then Lithium is recycle from the aqueous solution. The pre-treated active material is in powder form and put in to calcination methods. At temperatures higher than 700°C (C. Liu et al., 2019), Metal oxides and Li2CO3 are produced when the lithium metal oxide of the cathode and anode react (Hung et al., 2021). The reactions that occur are shown in eqs (1) to (5).
$$\text{C}+12\text{L}\text{i}\text{M}{\text{O}}_{2}\to 6{\text{L}\text{i}}_{2}\text{O}+4{\text{M}}_{3}{\text{O}}_{4}+\text{C}{\text{O}}_{2} \left(1\right)$$
$$\text{C}+4\text{L}\text{i}\text{M}{\text{O}}_{2}\to 2{\text{L}\text{i}}_{2}\text{O}+4\text{M}\text{O}+\text{C}{\text{O}}_{2} \left(2\right)$$
$$2{\text{M}}_{3}{\text{O}}_{4}+\text{C}\to 6\text{M}\text{O}+\text{C}{\text{O}}_{2} \left(3\right)$$
$${\text{L}\text{i}}_{2}\text{O}+\text{C}{\text{O}}_{2}\to {\text{L}\text{i}}_{2}\text{C}{\text{O}}_{3} \left(4\right)$$
$$2\text{M}\text{O}+\text{C}\to 2\text{M}+\text{C}{\text{O}}_{2} \left(5\right)$$
For lithium recycling the major drawback in pyrometallurgy technique is that extra steps are necessary after calcination. This additional step typically involves melting the material in water or a solvent and breaking it. However, the less solubility of Li2CO3 (13g/L− 1) requires a huge quantity of solvent (Cabeza et al., 2020).
The lithium (Li2CO3) is subsequently dissolved in the water via water leaching on the calcinated powder. The metal oxide doesn't break down in water. Figure 10 illustrates the process of water leaching through filtration, the separation of the aqueous solution and the undissolved metal oxide to create a Li2CO3 solution, and the subsequent water evaporation to generate Li2CO3. This technique is straightforward and can handle a lot of waste lithium. Utilizing pyrometallurgy to recycle lithium involves complex calcination technology and has the potential to emit hazardous gases (Tan et al., 2020).
3.7.4 Electrochemical process
This method is use for extraction of Li from pre-treated active material “black mass” of wasted li-ion batteries (Bae & Kim, 2021). The black mass put into the water and separated the Li by using L-ion conductive ceramic solid electrolyte (Hoyer et al., 2015). The complete process of extracting of Li can be seen in Fig. 11. When the black mass put into the water the Li in the cathode does not dissolve while Li in the anode dissolve in the water and form the LIOH (aq).
when solution put into the electrochemical device and applied charge, by using the solid ceramic electrolyte the dissolved and undissolved Li can be extracted.
The dissolved Li+ can be extracted by oxygen transformation reaction (OTR), the reaction process is shown in Eq. (6). The charging potential varies according to the cathode material in the wasted material.
$$2\text{L}\text{i}\text{O}\text{H}\left(\text{a}\text{q}\right)\to 2{\text{L}\text{i}}^{+}+{2\text{e}}^{-}+1/2{\text{O}}_{2}+{\text{H}}_{2}\text{O} \left(6\right)$$
In cathode powder the undissolved Li+ can be separated by applying same technique as delithiation in cathode material (eqs (7) and (8)).
$$\text{L}\text{i}{\text{M}\text{O}}_{2}\to {\text{L}\text{i}}_{+}+{\text{e}}_{-}+{\text{M}\text{O}}_{2}(\text{M}=\text{C}\text{o}, \text{M}\text{n}, \text{N}\text{i}) \left(7\right)$$
$$\text{L}\text{i}{\text{F}\text{e}\text{P}\text{O}}_{4}\to {\text{L}\text{i}}_{+}+{\text{e}}_{-}+{\text{F}\text{e}\text{P}\text{O}}_{4} \left(8\right)$$
The aqueous solution converted a strong base due to the LiOH influence. OTR reaction occur on charging lower 3.6V, and powerful base pH (pH > 11). In some conditions Li+ is directly extracted from the cathode powder due the delithiation potential is 3.5V such as, cathode powder of Li.Fe.PO4, which is lower than the voltage of OTR reaction. While, LiNi0.3Mn0.3Co0.3O2 (3.7 V), LiCoO2 (3.9 V), and LiMn2O4 (4.0 V), Li+ extraction from the solution, rather than from the cathode powder, because of delithiation potential is higher than that of the strong base OTR reaction.
However, according to the features of the OTR reaction, the pH of the aqueous solution lowers during charging, and the operating voltage of the OTR reaction steadily increases. The Li+ can be separated and extraction in both conditions powder and solution, and when Li+ can no longer be extracted, automatically, the charging of the system is done.
Following the charging process the separated Li+ ions are start to travel another solid electrolyte, and start new reaction with H2O and electron (2e−), and form an aqueous solution of LiOH which can be express in Eq. 9. This reaction is called oxygen reduction reaction (ORR). The Li2CO3 is form when LiOH react with CO2 because it is very strong base and highly reactive with CO2 during the reaction. The formation process of Li2CO3 can be seen in Eq. 10.
$$2{\text{L}\text{i}}^{+}+ 2{\text{e}}^{-}+1/ {2\text{O}}_{2}+{\text{H}}_{2}\text{O} \to 2\text{L}\text{i}\text{O}\text{H} \left(9\right)$$
$$2\text{L}\text{i}\text{O}\text{H} + {2\text{C}\text{O}}_{2}\to {2\text{L}\text{i}}_{2}{\text{C}\text{O}}_{3}+{\text{H}}_{2}\text{O} \left(10\right)$$
Electrochemical extraction allows Li2CO3 powder to be obtained without the requirement for drying or precipitation, because Li2CO3 powder precipitates spontaneously when the system is discharged continually. When a discharge happens, the level of Li2CO3 in the water progressively rises, Furthermore, because of the ORR, H2O is consumed, and the concentration of Li2CO3 rises in relative to the reduction in solvent amount. This reasons Li2CO3 to naturally precipitate (Zhou et al., 2020).
3.7.5 Bio metallurgical process
As a bio-hydrometallurgy technology, bioleaching employs microorganisms such as fungus, chemo-lithotrophic, and acidophilic bacteria (microbial metabolites) as leaching agents employing ferrous ion and sulfur as the source of energy to form metabolites in the leaching medium in order to recover Li and precious metals (Thompson et al., 2020).
However, compared to other traditional processes, bioleaching offers a number of advantages including higher recovery, simplicity, cost-effectiveness, and reduced energy consumption procedure without the requirement for severe environmental conditions or specialized industrial equipment (Bahaloo-Horeh et al., 2018).
Figure 12 illustrates three fundamental solid waste bioleaching techniques: (a) one-step bioleaching: The bioleaching procedure is finished in a single phase, Microorganisms and solid waste are added to the medium simultaneously, and the bioleaching process is carried out as the microorganisms are being cultivated. (b) Bioleaching in two steps: Two phases comprise bioleaching. After bacteria achieve logarithmic phase without solid waste, solid waste is introduced to start bioleaching, and (c) Spent-medium bioleaching: Without solid waste, organisms can grow and make leaching agents. After centrifuging and filtering the mixture, solid waste is added to the cell-free medium to start the bioleaching process.
Two-step bioleaching yields more than one-step. Compared to one-step and two-step bioleaching, wasted medium bioleaching is faster and easier. Because leaching and metabolite production are separated, Both chemical and biological processes can be improved on their own. Higher temperatures and lower pH can increase metal recovery from black matter. The spent-medium approach requires extra bioreactor tanks due to microbial fermentation and two-stage use of metabolites.