ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 20 with recycling helping to reduce the gap between supply and demand for battery manufacturing. To recover spent LIB material and help provide more sustainable production of strategic materials in the U.S., there is first an urgent need to address the transportation of EOL batteries from collection sites to recycling facilities. The risks involved with transporting large quantities of LIBs include thermal runaway, electrical hazards, and chemical instability of the electrode and electrolyte materials in air. For this reason, spent LIBs have been classified as Category 9 hazardous materials and restricted to ground transport only with highly regulated packaging requirements[3]. These regulations make transporting end-of-life LIBs over long distances a high-cost endeavor. In an ideal scenario, spent LIBs would be rendered inert or recycled locally at collection sites. Thus, there is a significant need to develop novel, cost-effective methods to place cells, modules, and packs in a safe state. LIB RECYCLING TECHNOLOGIES When a battery has degraded too significantly to function in an electric vehicle, it may still have enough remaining useful life to be applied in a less demanding, second use application, such as stationary storage. However, all batteries have a finite lifetime and will eventually need to be disposed of, preferably through a recycling process. Three main battery recycling technologies can be applied to end-of-life LIBs from electric vehicles: pyrometallurgy, hydrometallurgy, and direct recycling. Figure 2 captures the stage at which these different recycling processes can be applied to LIBs and the point at which the recovered material would be reinserted in the typical life cycle of an LIB for electric vehicles[4]. The most common recycling strategies commercially employed today are pyrometallurgical and hydrometallurgical processes. A typical recycling process using these techniques includes an initial pyrometallurgical treatment, in which EOL batteries are disassembled and reduced to a metallic alloy through high-temperature smelting, followed by hydrometallurgical recovery of the resulting metal alloys. Generally, strong acids are used in the hydrometallurgical process to leach valuable metals into an aqueous solution followed by chemical precipitation or electrolysis to separate multiple metal elements. The purpose of both hydrometallurgical and pyrometallurgical recycling techniques is to recover individual elements that can be resynthesized into new cathode materials. However, these techniques have a number of drawbacks including high energy input requirements, toxic gas production, and acidic aqueous waste generation. These outputs require introducing post-treatment processes to mitigate any environmentally negative impacts, which leads to higher costs for recycling[5]. These methods are more economically viable for cells that contain elements with high inherent value like Co and Ni. Uncertainty remains with regard to how economical these processes are for cells employing lithium iron phosphate (LFP batteries), for instance. An emerging alternative recycling process called direct recycling aims to recover cathode materials from EOL batteries without sacrificing their chemical composition or morphology. Direct recycling could lead to lower costs to recover materials, reduced energy consumption, decreased water consumption, and fewer greenhouse gas emissions by avoiding additional refining and cathode material synthesis steps. The concept of direct recycling was first introduced and patented by Steven Sloop in 2010. Since then, several direct recycling start-up companies have been established in the U.S. including OnTo Technology, Li-Cycle, Farasis Energy, and Princeton NuEnergy, all of which are developing different direct recycling methods[6]. Ongoing research in the field of direct recycling Fig. 2 – Diagram of the lithium-ion battery life cycle with different recycling options generated by the ReCell Center[4].
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