Graphite Recycling from End‐of‐Life Lithium‐Ion Batteries: Processes and Applications

Abstract

resistance), is suitable for a wide range of industrial applications, depending on its form. [1] The world has consumed resources exceeding 800 million tons of recoverable Gr. Although more than 20 countries are producing natural graphite (NGr), in 2019, as shown in Figure 1a, the world production was controlled by China, Mozambique, and Brazil. [4] Total production of NGr in 2019 was estimated to be 1 130 000 tons, and China is the largest producer of Gr with 62% (about 700 000 tons). The NGr products contain both amorphous Gr (microcrystalline) and flake Gr (crystalline), however, about 1% of NGr is vein (lump) Gr (interlocking aggregates of flake Gr crystals), which is produced in Sri Lanka. [1,[5][6][7][8] Another type of Gr is synthetic (artificial) Gr (SGr), which is synthesized by heat treatment of a coke-based precursor at very high temperature of more than 2500 °C. [9,10] The production of SGr is costly from both an energy and a time perspective. The process of preparation, heating and cooling takes several weeks to several months. [11] Table 1 reports the characteristics of different types of NGr and SGr. Although the chemical structure is similar for both NGr and SGr, they differ in electrochemical behavior and price. In 2018, the price for the NGr and SGr as anode material were between 4 and 8 $ kg −1 , and 12 and 13 $ kg −1 , respectively. [12] Due to the high melting point of 3900 °C, [13] the largest amount of Gr produced is used in the reactors and furnaces of steel and refractory industries. [14] However, emerging Li-ion battery (LIBs) industries could substantially increase world demand for Gr (forecasted to rise by 10-12% per year). [2] Gr is the state-of-the-art anode material in both primary (non-rechargeable), and secondary (rechargeable) batteries with approximately 18% of flake NGr worldwide used in batteries. [15] The market shares of various anode materials are illustrated in Figure 1b,c for years of 1995 and 2010, which mainly is dominated by Gr-based materials. Despite its higher price, the market share of SGr for automotive batteries is growing over time, as the quality fluctuates less than for NGr, and SGr demonstrates extremely high levels of purity. [12,16] In 2018, the SGr had a market share of about 56% in comparison to 35% for NGr as an anode material (which are almost similar to percentages of 2010 (Figure 1c), and the rest consisted of amorphous carbon, silicon composites or lithium titanate. [12] The Gr market, in general, is growing fast due to the replacement of fuel-driven cars by electric vehicles (EVs) (the number of EVs cars produced in 2020 was about 3.24 million cars) [18] and The number of lithium-ion batteries (LIBs) from hybrid and electric vehicles that are produced or discarded every year is growing exponentially, which may pose risks to supply lines of limited resources. Thus, recycling and regeneration of end-of-life LIBs (EoL-LIBs) is becoming an urgent and critical task for a sustainable and environmentally friendly future. In this regard, much attention, esp...

Sustainable Reuse and Recycling of Spent Li‐Ion batteries from Electric Vehicles: Chemical, Environmental, and Economical Perspectives

“…In addition to the aforementioned methods, electrolysis, supercritical extraction, and microwave treatment are being explored to find a more efficient and economical method for graphite recovery. [40] Industrial demonstration of graphite recovery can be seen in the process developed by the OnTo technology LLC., where graphite is recovered under supercritical condition followed by thermal treatment and the obtained graphite with the same size and morphology as the commercial graphite. The process, however, needs to be further developed for large scale operation in terms of environmental impact and cost.…”

“…[ 9 ] Generally, graphite is recovered via washing, thermal treatment, and a hybrid process using acid leaching and thermal treatment processes. [ 40 ] Ideally, the anode sheet should be separated from the rest of the LIB components and graphite particles are delaminated from the Cu current collector by crushing, solvent washing, and mild thermal treatment owing to weak binding between graphite and Cu. [ 43 ] However, the anode is usually crushed together with the cathode and other component, generating the black mass, in most processes.…”

“…For instance, an average EV LIB contains ≈25 wt% or roughly 25–70 kg of graphite that either ends up in landfill or incinerated after use. [ 9 , 40 , 41 ] Moreover, ≈70% of the global graphite production for EVs is controlled by China, which contributes to the risk of supply instability as a result of increasingly concerning geopolitical conflicts. [ 30 ] Furthermore, graphite purification process requires usage of strong acids and hence is not environmentally friendly.…”

“…[ 41 ] Recovered graphite can be reused as an active material in LIB anode after processing or converted to high value materials such as graphene and reduced graphene oxide that can be utilized in several applications including sensors, catalysts, and supercapacitors. [ 9 , 40 ] Additionally, it has been shown that exfoliation of graphite from spent LIBs can be done with milder conditions compared to natural graphite due to the expanded interlayer spacing from Li‐intercalation and the presence of structural defects. [ 42 ] In addition to graphite, ≈5–7 wt% of anode consists of Li, which could further accelerate the recycling of anode given the quickly increasing price of battery‐grade Li 2 CO 3 and LiOH.…”

“…In addition to the aforementioned methods, electrolysis, supercritical extraction, and microwave treatment are being explored to find a more efficient and economical method for graphite recovery. [ 40 ]…”