ACS Energy Letters
The use of lithium-ion batteries (LIBs), has grown exponentially since their discovery in the 1970s and until the 2019 Nobel Prize. (1-4). The world has come to depend on LIBs for their power and convenience. As a result, both manufacturing and disposal of LIBs have become increasingly political and environmentally sensitive. (5.3.6) The world’s reserves of cobalt and lithium are small and unevenly distributed. Their mining, however, is labor-intensive and produces significant pollution. (7.8) Congo produces more than 70% of the world’s cobalt (9) and no other country produces more than 5%. Mozambique and China produce 70% of the world’s natural graphite. This is an important material for anodes. (10) Natural disasters, war, or resource allocation decisions can also affect the availability of these materials.
Due to the short life span of smartphones, resource scarcity and supply are especially important. Most LIBs that are discarded end up being landfilled or stored, which can pollute the environment and waste energy as well as non-renewable resources. There were more than 5.6 million electric cars (EVs) worldwide as of February 2019, a 64% increase over 2018. (11) 58% of all cars worldwide will be electric by 2040. (12). Due to the explosive growth of EV numbers and the enormous size of their batteries (Tesla Model 3 Long Range’s 4416 cell battery weighs 480kg and a Tesla Model 3 Long Range’s battery weighs 480kg), significant LIB waste will continue to be generated every year. This will have huge environmental and economic impacts on the environment and accelerate the decline of mineral resources. LIBs, which are complex structures that include one of five common cathodes (an anode, electrolyte, and separator), as well as current collectors, packaging components, and Table S1, add to the difficulty in recycling. According to the International Energy Agency, electric vehicles generated around 500,000 tons of LIB-related waste in 2019. The total amount of LIB waste produced by 2040 could reach 8 million tons.
This article will compare and summarize different LIB recycling methods. We analyze the types of materials that were recycled using data from CAS Content Collection. These analyses give a comprehensive view of the progress made in LIB recycling both in academia and industry. These analyses also discuss the economic and environmental benefits and challenges of LIB Recycling. We provide a comprehensive overview of all existing and planned recycling facilities, as well as their reported capacities.
The CAS Content Collection is the world’s largest repository of chemistry-related information and is particularly useful for quantitative analysis of publications against variables such as time, country, and research area, as well as their substance details. Here, we searched for publications related to LIB recycling (see Supporting Information (SI) for full methods and limitations). A pool of 3596 documents was analyzed based on their publication type and publication year ( Figure 1 ). While the global scientific publication volume has been steadily increasing in the past decade, we found that the annual volume growth in publication on this topic (32%) far exceeds that of overall scientific publications (4% annually), (19) suggesting an emerging interest in recycling, especially in the last 4 years. We also found that patent applications account for 74% of the Li-ion battery recycling literature, whereas patents are outnumbered by journal articles 2:1 in the entire CAS Content Collection, showing the high commercial value of technologies and discoveries around LIB recycling. An analysis of the countries/regions associated with the affiliated organization of these documents shows that China has the highest publication volumes by far in both journals and patents ( Figure S1 ). Further analysis of patent assignees revealed the top organizations by volume of patent applications on LIB recycling ( Table S2 ) are primarily located in China, Japan, and France.
Figure 1. Journal articles and patent publications on Li-ion battery recycling (data for 2021 is partial). Inset shows relative publication volumes of journal articles and patents in Li-ion battery recycling (left) and in the chemical literature as a whole (right).
Industrially Implemented and LIB Recycling Methodologies
Due to the complex structure and number of materials in LIBs, they must be subjected to a variety of processes prior to reuse/recycling. LIBs must be first classified and most often pretreated through discharge or inactivation, disassembly, and separation after which they can be subjected to direct recycling, pyrometallurgy, hydrometallurgy, or a combination of methods, as shown in Figure.
Figure 2. Typical direct, pyrometallurgical, and hydrometallurgical recycling methods for recovery of Li-ion battery active materials. From top to bottom, these techniques are used by OnTo, (15) Umicore, (20), and Recupyl (21) in their recycling processes (some steps have been omitted for brevity).
Direct methods require the disassembly and recycling of cathode materials (22 ). Reconditioning used batteries will also require the disassembly of LIB, (22) . Many of the failure mechanisms in LIB require the replacement of battery components. For stationary applications, LIB will need to be classified and determined by charge state and capacity. Table 1 shows the most commonly used cathode materials LCO, and LFP. However, methods for automated battery disassembly remain limited in their scope and volume.
Pyrometallurgy is the use of heating to convert metal oxides in battery materials into metals or metal compounds. (25) After pretreatment, the battery materials are heated in an atmosphere of vacuum or inert air to transform the metal oxides into a mixed alloy. This can contain, depending on the battery composition, cobalt, nickel, copper, and iron. Pyrometallurgical methods use simpler pretreatment (mostly shredding or crushing), to prepare batteries for recycling. There are fewer methods to recycle LIB in different compositions, shapes, and sizes, and these methods require less pretreatment. (26) Some pyrometallurgical techniques can make lithium recyclable, but these methods are best for precious metals like cobalt.
Hydrometallurgical methods use mainly aqueous solutions for extracting and separating metals from LIBs. Pretreated battery materials with Al and Cu current collectors removed are usually extracted using H2SO4 or H2O2, but HCl, HNO3, and organic acids such as citric and oxalic acid are also common.
To understand how recycling may be able to decrease the effects and costs of battery recycling, the materials used in batteries and their costs should be defined, and the cost of new materials and recycled materials compared. Mining and refining of virgin materials and recycling used materials for batteries are exact environmental costs. As an example, 1 ton of virgin lithium requires 250 tons of ore or 750 tons of brine. (43) While refining brine requires less energy than refining spodumene, it requires 18–24 months, yields lower-grade lithium and recovers less of the lithium present in brine than is recovered from the ore. (44) In addition, water use is a concern; 65% of the water in Chile (one of the major sources of lithium) is consumed by the mining industry.
There are also environmental costs associated with recycling, such as transportation and preparation. Kim et. al. noted, for instance, that “the most widely used or researched techniques are also environmentally hazardous.” (26 Pyrometallurgical techniques are relatively simple, but they can have significant environmental and energy costs for combustion and calcination. Hydrometallurgical processes require less energy than pyrometallurgical ones, but they still require many reagents and must be purified.
LIB Recycling Facilities in the Future
Given an annual LIB production volume projected to exceed 1 million tons by 2025, (18) additional LIB recycling facilities will be needed. As shown in Figure 5 and Table 2, there are at least 32 established or planned facilities for LIB recycling with roughly 322,500 tons of recycling capacity (as of late 2021) and approximately 70,000 tons of planned recycling capacity (although the capacities of 4 of the 12 planned facilities are not known).