Advance review on the exploitation of the prominent energy-storage element Lithium. Part II: From sea water and spent lithium ion batteries (LIBs)
Introduction
The fascinating growth in clean and renewable energy to every corner of the world is essential for the global sustainability. The LIBs with their unique technical features (of: specific energy density 100–265 W h/kg, specific power 250–340 W/kg, life span cycles 400–1200) have potentially revolutionized the market supply and demand of the renewable energy (Wagner, 2006, Choubey et al., 2016). Moreover, the development of parallel sectors such as, the direct plug-in hybrid vehicles, consumer electronics, and space, military and medical applications are creating new opportunities to cut down the cost of rechargeable LIBs and presenting them to be the suitable candidates in off-grid renewable energy for a common storage purpose (Diouf and Pode, 2015).
The vital role of lithium in LIBs due to being a low density (0.534 g/cm3) metal with very high electrochemical potential (−3.045 V) is therefore, accounted for their high economic and strategic importance while placing the lithium among “energy-critical elements” (Critical Materials Strategy, 2010, ECEs-Energy Critical Elements, 2011). As projected, lithium will witness a shortage in commodity market in near five years and would be required 498 kilo tons of Li2CO3 in 2025 as compared to 265 kilo tons in 2015 (Fox-Davies Resources Specialist, 2013, Choubey et al., 2016). Over the last one year, the price of Li2CO3 per ton has already risen (in US dollar) from $4900 to $5900, and is predicted to rise further 20% by 2018 (Ker, 2015). The situation for the lithium in commodity market would be more critical with Tesala Giga factory planning to produce 5 Lacs electrical vehicles per year which alone requires the entire global production of LIBs at present (https://www.teslamotors.com/gigafactory), and the launching pad for cheaper LIBs (EV price may cut down up to 10 folds) set by the Indian Space Research Organization (ISRO) (http://www.autocarpro.in/news-national/lithium-ion-battery-capability-developing-india-9979). The huge gap between the market supplies against demand cannot be actualized without pushing the metallurgical recovery of lithium from all possible resources. Among the conventional resources, lithium production from minerals has been recorded to approximately 4420 tons in the year 2015 (U.S, 2015, Choubey et al., 2016) whereas, the contribution of brine remained nearly to 18,000 tons (U.S, 2014, U.S, 2015). Although the reserves are sufficient to fulfil the market demands, commissioning of newer processing units and the enhanced product yield are urgently required (Choubey et al., 2016). The lithium production from brine is not easy due to already maximum production; whereas processing of minerals to produce lithium requires high cost investment. The non-availability of primary resources of lithium in every corner of the globe is also a major bottleneck.
In contrast, sea water has been accounted for 230,000 million tons of lithium reserves which is thousands fold higher than that of the combined minerals and brine resources (Yoshizuka et al., 2006). The concentration of lithium in various Oceans and sea water is presented in Table 1. At the same time, the usage of LIBs in most of the rechargeable gadgets everywhere is generating a large amount of wastes after completion of their life-cycle. It can be depicted from Fig. 1 that the contribution of LIBs in overall lithium consumption would be 65% in 2025 which was 35% in 2015. The consumption of LIBs in the year 2010 has increased from 4.6 billion units to 7 billion units in 2015 containing 5–7% lithium therein, which can be considered as a huge reservoir of lithium post usage of the LIBs (Li et al., 2010a, Li et al., 2010b, Li et al., 2011, Li et al., 2013).
The most advantageous aspect relating to such non-conventional resources of lithium is that they are not limited to a geographic boundary. Plenty of sea water is available across the country/region while the consumer country of LIBs is the owner of the spent LIBs as a potential resource of lithium, if recycled properly. However, the processing of sea water is very complicated largely due to low lithium contents, as low as 0.1–0.2 ppm (Yoshizuka et al., 2006), whereas the problem remains associated with steps like physical beneficiation of spent LIBs has been identified to be critical. The aqueous solutions, either sea water or leach liquor in different media of the treated LIBs often containing high amount of impurities, are fraught with much difficulties during the downstream processing. Therefore, in order to explore new methodologies by seeking the improvement on separation and recovery of lithium values, on the both economic and technological front, it is vital to review the previous processing methods already in vogue or in the developmental stage.
It is worthy to mention here that to-date several review articles dealing with the processing of such non-conventional resources are not up to the mark as per the criticality of lithium. The traditional separation and recovery processes of sea water using modified adsorbent are considered to be non-sustainable and therefore, it needs discussion on the processes that ensure the process sustainability such as, the electro-dialysis, which has been emphasized in this review. The recycling processes of spent LIBs have been reviewed more frequently in recent times (Xu et al., 2008, Thyabat et al., 2013, Meshram et al., 2014, Ordonez et al., 2016, Swain, 2017). However, not a single article is focused on lithium recovery instead they have reviewed the extraction processes of high market value metal, cobalt. Moreover, a multi-disciplinary feature defining the recovery procedures with emphasized on understanding the process fundamentals and chemistry has also been discussed. Subsequent to part-I of our review on the extraction of lithium from conventional/ primary resources such as ores and minerals (Choubey et al., 2016), this state-of-the-art review (Part II) can additionally be helpful to the further researches in the area while providing a way forward with the tacit aim of developing the sustainable technologies for lithium recovery from its non-conventional resources that would ultimately serve to achieve the sustainable, clean and renewable energy.
Section snippets
Processes for lithium recovery from sea water
Seawater has been recognized as a promising resource to achieve a sustainable water-energy materials-food nexus (Diallo et al., 2015). Approximately 5 × 1016 tons of salt dissolved in 1.3 × 1018 tons of sea water which reserves approximately 40 elements in the form of ions or salts (Yoshizuka et al., 2006, Lee, 2005, Bardi, 2010). Concentration of ions in seawater can vary significantly from one location to another depending on the geography, climate conditions, and surface water runoff. Some of the
Processes for lithium recovery from the spent LIBs
Spent LIBs are a valuable source of critical metals like cobalt (5–33%), lithium (5–7%), manganese (15–20%) and nickel (0.02–0.3%), and therefore, they have been identified as one of the potential resources for lithium production in near future. Numerous works have been carried out in this area to recover the contained metals and recycle the spent LIBs. It may be noted that some of the developed processes are commercialized, but few of them recover lithium (Shin et al., 2005, Xu et al., 2008).
Perspective and recommendations
As projected the increasing demand of energy storage devices will continue to be critical for lithium in the near future and therefore, the efficient exploitation of the non-conventional resources is important. The exploitation of sea water has ocean of opportunities if commercialized properly. However, even the most explored adsorption process is yet to be found fit for the commercial application. For this, the enhancement in sorption capacity of the designed sorbent/s, low cost of their
Conclusions
A number of adsorbents like manganese oxide, titanium oxide, alumina, and activated carbon have been used for the lithium enrichment from sea water. The spinel manganese oxides have shown the higher adsorption capacity. The suitable pH for adsorption has been found to be in the alkaline range (pH 8–12), while desorption by dil. HCl (of pH ∼ 2) has yielded greater recovery of lithium. Electro-dialysis is an emerging technology that can adequately upgrade the lithium contents from the lean
Acknowledgements
This research was supported by the national research project titled “The Development of Technology for Extraction of Resources Dissolved in Seawater” of the Korea Institute of Geoscience and Mineral Resources (KIGAM) funded by the Ministry of Oceans and Fisheries, Republic of Korea.
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