# Lithium Metal: The Key to Green Transportation
## 4 Discussion
### Lithium Recycling  
The transition to renewable energy technologies would result in a massive amount of spent LIBs that would need to be recycled. [PERSON] et al. 's [121] estimation shows that the spent LIBs may surpass 25 billion units, equivalent to 5 \(\times\) 10\({}^{5}\) tons in 2020. According to the LIB cathode technology [122], the end-of-life LIBs account for an important lithium concentration of about 2-15% [3]. The recycling of rechargeable batteries should not only be for recovering economic metals but also for saving the environment. There are other types of rechargeable batteries, like NiCd and NiMH, that are composed of hazardous chemical elements (Cu, Zn, Co, Mn, and Ni) and toxic elements (Hg, Pb, and Cd) [123; 124; 125; 126] that should not be thrown in the environment. Fortunately, the high demand expectations for lithium and cobalt may prioritize the recycling of LIBs [3] over disposal. Due to several processing obstacles and challenges, the rate of LIB recycling is still low. Since the spent LIBs contain toxic materials and have a complex layered structure, manual dismantling (the separation of useful from non-useful components) is highly challenging. Additionally, due to the lack of systematic collection and sorting systems, mixing different types of spent LIBs complicates the process and reduces the effectiveness of recycling. Due to these challenges, the cost of recycled lithium may be more expensive than that from branes [3; 127]. Some researchers, like [PERSON] et al. [3], labeled sorting end-of-life LIBs as the major challenge for recycling companies, and urged that mixing different types of batteries (LIB, NiCd, NiMH, and others) reduces the effectiveness of the process. He suggested a battery-tagging system as one of the policies that can facilitate the segregation and collection of batteries with similar properties based on the available recycling technologies. Fortunately, the technologies that can deal with complex or mixed battery wastes are still underway, and they are being developed with a critical cost comparison of manufacturing new materials over reusing, recovering, and recycling LIBs [43; 128]. Apart from lithium, spent LIBs have higher concentrations of other important metals than natural ones, including cobalt (5-30%), copper (7-25%), nickel (0.2-10%), aluminum (3-14%), and iron (20%) [121]. Considering a large numbers of metals to be recovered from LIB recycling, it is gradually becoming an interesting project for private firms and government institutions to fund [129]. Though electrification is becoming popular in developing countries, industrial-scale recycling seems to be almost impossible for those countries because of huge capital costs for plant infrastructure and the lack of viable economics to make recycling operations stand alone. Currently, industrial recycling facilities are only in developed countries, where they use methods like pyrometallurgy, hydrometallurgy or a hybrid system for recycling [3]. Moreover, the unclear supply channel of spent batteries to recycling companies still hinders significant global recycling progress. Currently, the cost of the exploitation of primary lithium resources and reserves is low [40] and is hindering the use of secondary source lithium. As a result, the recycling rate remains insignificant compared to the total lithium supply [130]. According to [PERSON] et al. [43], the recovered spent LIBs are less than 2%, and the remaining 98% go for disposal, leading to the potential for serious damage to the ecosystem because of their hazardous and toxic chemicals. The hope of recycling growth relies on the price of lithium from primary sources, which has been increasing since 2002 (from $1590/ton in 2002 [43] to $16,500/ton in 2022 [131]) and is expected to continue growing due to increasing future demand for EVs and larger grid or off-grid energy storage devices.