Recovery of Valuable Metals from Lithium-Ion Batteries

Recovery of Valuable Metals from Lithium-Ion Batteries Article Series / Part 1 Introduction With advancing technology and increased consumption, there has been a rise in the use of electrical and electronic equipment. This generally leads to increased battery consumption. Depending on the device and sector in which they are used, batteries vary in type, and in terms of working principle they are divided into two categories: primary (non-rechargeable) batteries and secondary (rechargeable) batteries. The reactions that occur in primary batteries are one-directional, while the reactions in secondary batteries can be reversed by applying electrical energy from an external source. As the use of disposable batteries increases, the problem of battery waste emerges. At the same time, because rechargeable lithium-ion batteries have a wide range of applications, the amount of waste generated is also increasing. The most well-known types of lithium-ion batteries are lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium nickel cobalt manganese (LiNiCoMnO2), lithium iron phosphate (LiFePO4), lithium nickel cobalt aluminium (LiNiCoAlO2), and lithium titanate (Li4Ti5O12) batteries. Lithium-ion batteries contain graphite, cobalt, and lithium, as well as aluminium, nickel, manganese, copper, titanium, certain rare earth elements, and plastics. The recovery of these elements, known as critical and strategic raw materials, is extremely important. Advancing technology, economic reasons, and the growing need for certain critical raw materials make the recovery of valuable metals from lithium-ion batteries a necessity. Lithium-ion batteries generally consist of three parts: an anode, a cathode, and an electrolyte. The cathode is composed of metal oxides and the most commercially widely used is LiCoO2. The anode consists of a porous carbon structure, and the primary material used for this purpose is graphite. The electrolyte generally consists of organic solvents such as LiPF6 containing lithium ions (Vıcıl, 2011). Figure 1 shows the components of the battery and their material contents (Ellingsen and Hung, 2018). Lithium-ion battery technology is advancing every day. With these developments, applications are expanding and consequently usage quantities are increasing in parallel. Lithium-ion batteries, which became widespread with the use of mobile phones and laptops, are now also being used in larger-capacity solar energy storage systems, electric vehicles, and buses. Their use in nearly every technological device has significantly increased the size of the lithium-ion battery market (Pillot, 2019). Lithium-ion batteries can create dangerous situations such as burning and flashing when exposed to high temperatures. For this reason, from the past to the present, many studies have been conducted and technologies developed on the safe use of lithium-ion batteries. In particular, battery cooling systems are found in high-capacity battery-containing technological devices such as electric vehicles. Devices without cooling systems, such as mobile phones, should not be exposed directly to sunlight. New-generation lithium-ion batteries provide much safer operating conditions compared to their predecessors. Thus, lithium-ion batteries can be easily used in electric vehicles. At the same time, their low cost and easy maintenance make them a preferred choice. Due to their long lifespan and extended storage capability, the advantage of lithium-ion batteries is quite significant (Prabhakar, 2008). Lithium cobalt oxide (LCO) type lithium-ion batteries have high specific energy. Having high specific energy means that the ratio of the amount of energy stored relative to the battery size is quite high. For this reason, LCO type lithium-ion batteries are most commonly used in portable technological devices such as mobile phones and laptops (Akkuş, 2011). Lithium-ion batteries mainly consist of an anode and a cathode. Graphite is located on the copper anode, while lithium cobalt oxide is located on the aluminium cathode. When energy is consumed, lithium ions move from the anode to the cathode, while during charging this movement occurs in the opposite direction (Şahan and Patat, 2014). Despite their high specific energy, LCO type batteries have a low cycle number. For this reason, they must be changed frequently. Depending on their application, the type of lithium-ion battery varies, but they are used in small hand tools, electric vehicles, and as high-energy storage sources. While Figure 2 shows the structure and components of lithium-ion batteries used in mobile phones, Reactions 1 and 2 show the anodic and cathodic reactions in LCO batteries (Gülbeyaz, 2019). Chemical changes occur to a large extent in the active cathode material. This change, which creates different types within lithium-ion batteries, directly influences usage requirements. With the use of different raw materials, increases in capacity, power, and lifespan can be achieved in lithium-ion batteries (Miao et al., 2019). The anode and cathode can generally be referred to as electrodes, and these electrodes can have layered and spinel structures. The cathode, through its layered structure, enables the cell to charge and discharge. During charging and discharging, lithium ions exchange positions between the positive and negative electrodes. The displacement reactions of lithium ions as mentioned are called topotactic (Bolat et al., 2012). In the chemical reaction occurring within the battery, the anode and cathode are active materials. As seen in Figure 3, lithium transitions between the active materials (Şahan and Patat, 2014; Gülbeyaz, 2019). According to prepared reports, the market volume of lithium-ion batteries is projected to reach USD 1 billion in 2017, USD 36 billion in 2020, and USD 75 billion in 2030 (Pillot, 2019). Lithium-ion batteries, used only in devices such as laptops and mobile phones in the early 2000s, have reached quite high gigawatt values in the 2020s due to their use in higher-technology-demanding fields such as electric vehicles. The change in the total amount of waste lithium-ion batteries over a ten-year period is shown in Figure 4 (Melin, 2020). The volume of 1,000 gigawatt hours in 2020 is expected to show approximately a threefold increase towards 2025. According to analytical reports, considering the accelerating increase in numbers in the electric vehicle sector, which will be the area of greatest use, this figure is expected to increase tenfold by 2030 (Melin, 2020). Research Assistant Zeynep Üçerler Istanbul Technical University Faculty of Mining, Ore Preparation Engineering Department Research Assistant Nazlım İlkyaz Dinç Istanbul Technical University Faculty of Mining, Ore Preparation Engineering Department Associate Professor Fırat Burat Istanbul Technical University Faculty of Mining, Ore Preparation Engineering Department