Optimizing the battery recycling loop

As the world shifts towards green technologies and renewable energy sources, the demand for batteries is growing rapidly. This is especially true for lithium-ion (Li-ion) batteries, which power a vast array of components, including smartphones, electric vehicles (EVs) and energy storage systems. However, this increasing reliance on Li-ion batteries necessitates a sustainable battery supply chain and a strategy to manage the resulting waste material as more batteries reach end-of-life.

Li-ion batteries can be recycled via three main methods: pyrometallurgy, hydrometallurgy or direct recycling, and parts of these processes can also be combined. In most cases, these techniques require pretreatment steps before a battery can be recycled, consisting of discharge or inactivation, disassembly and separation.

An electrical discharge is achievable when a Li-ion battery’s residual energy can be stored economically. Otherwise, inactivation by immersion in an inert aqueous solution is required to prevent combustion. Discharged or inactivated batteries can be manually disassembled to preserve their components. However, this process is time-consuming and it exposes workers to hazardous materials. The simplest method for disassembly is to shred or crush batteries into small fragments, often performed in a vacuum or inert atmosphere. This, however, precludes the intact separation of current collectors and battery casing, leading to higher downstream recycling costs.

After pretreatment, the Li-ion batteries undergo further processing to extract valuable metals, such as lithium, cobalt, manganese, copper, nickel and iron.

Pyrometallurgical processes require subjecting the materials to high temperatures in an inert environment to avoid combustion. This process is straightforward, scalable and efficient for recovering cobalt, manganese, copper, nickel and iron. However, it requires large amounts of energy, resulting in a lower yield of extracted lithium than other techniques. Higher purity of recovered metals can be achieved by combining pyrometallurgical with hydrometallurgical processes.

Hydrometallurgy leverages aqueous dissolution to ionize active materials, whereby metals are removed via leaching with acids, alkalis or bioorganic materials. This method provides precise recovery, higher product purity and significantly lower energy consumption than pyrometallurgy. However, the use of hazardous chemicals introduces safety risks, both to personnel and the environment. Therefore, careful management of waste solutions and toxic gas capture are necessary to mitigate these risks.

Unlike traditional methods that break down the cathode material into its elements, direct recycling, or "cathode to cathode recycling," focuses on separating and rejuvenating the used material. This approach is used to restore the capacity of Li-ion batteries.

Direct recycling requires fewer pretreatment steps and chemical solvents compared to pyrometallurgy and hydrometallurgy. This method produces higher-purity products, reducing the demand for mined materials and contributing to a more sustainable circular battery economy. A significant limitation of direct recycling is its reliance on a single cathode type. Due to the lack of standardization in battery design and cell chemistry, meticulous component separation is critical for the successful implementation of the process.

Bioleaching is an emerging recycling method, but its large-scale viability remains uncertain. In this process, specific battery minerals are recovered using bacteria. Bioleaching has been successfully used in the mining industry and it can serve as a complementary process to hydrometallurgy and pyrometallurgy.

Robotic disassembly of used batteries is a rapidly evolving technology with promising potential. This method automates the process of dismantling batteries to increase efficiency and reduce the hazards of human exposure to toxic battery materials. Despite significant advancements, robotic disassembly of used batteries still faces challenges posed by variations in battery construction and non-standard components, such as flexible cabling located in different areas from one battery to the next. Advanced algorithms capable of adaptive and intelligent operation are essential to address these complexities. Automation optimization is necessary to solve these and other complex disassembly problems, especially as battery recycling needs continue to escalate.

More efficient disassembly techniques and the ability to salvage whole components reduce the need for new materials to construct new batteries. This subsequently lowers battery manufacturing’s carbon footprint while increasing the overall capacity of the battery supply chain.

While these battery recycling processes are effective for recovering Li-ion battery minerals, environmental and safety concerns remain. For example, the chemical processes used in hydrometallurgical recycling involve the use of acids, strong solvents, toxic chemicals and other potentially hazardous substances. They must be carefully managed to prevent human harm or environmental contamination. Additionally, certain mechanical and chemical recycling methods require high temperatures and energy consumption. This contributes to the overall carbon footprint of the recycling process, raising concerns about its net sustainability.

Furthermore, most lithium-ion batteries are classified as hazardous waste at end-of-life for several reasons related to their chemistry, potential for fire and negative environmental impact. Worker safety is paramount during battery disassembly and processing. Exposure to toxic materials and the risk of fires or explosions necessitate adherence to stringent safety protocols. Addressing these challenges is critical to making battery recycling more efficient, safer, environmentally friendly and economically viable over the long term.

Achieving a circular battery economy requires a nearly complete recovery of active materials, plastics and metallic foils used in battery construction. This extends beyond traditional recycling, demanding a rethink of battery design, usage and disposal. Sustainable battery management is critical for establishing a closed-loop system and maximizing its repurposing or recycling.

One approach is second-life applications, where used batteries are repurposed for less demanding applications, such as energy storage systems for renewable energy. This extends battery life and reduces the need for new batteries, thereby decreasing the demand for processed minerals.

Policy and regulations also play a crucial role in completing the battery loop. Governments and regulatory bodies need to establish standards and incentives that encourage proper battery disposal, recycling and utilization of recycled materials in new batteries. Developing reasonable statutes requires collaboration among policymakers, industry stakeholders and end users to foster a sustainable battery ecosystem.

Electric car batteries, predominantly Li-ion, can be recycled using the described processes. However, the large size, weight and complexity of EV batteries multiply the challenges of mineral recovery.

Despite facing capacity challenges, EV battery recycling effectiveness is rapidly improving due to innovations mentioned previously. Large-scale battery recycling is becoming an increasingly important area of research because of the rapidly-growing number of batteries requiring future recycling. This figure is growing commensurately as record numbers of EVs take to the road and as battery-based energy storage systems proliferate.

Li-ion battery recycling powder plants recover valuable materials from used batteries by converting them into powder form. These facilities are becoming increasingly common for reuse in new batteries. They reduce the resulting “black mass” powder from broken-down batteries into its constituent elements for increased mineral recovery. This is typically achieved through high-intensity heat treatment, such as smelting or roasting (pyrometallurgy), or by chemical leaching (hydrometallurgy). While heat treatment is more straightforward, it results in lower-purity component yield compared to leaching. Therefore, combining both methods is often used, leveraging the benefits of each.

Li-ion battery recycling powder plants demonstrate the potential for advanced recycling technologies to close the loop in the battery supply chain. Recovery of high-purity materials in reusable forms helps reduce the need for mined materials, lessening the environmental impact of battery production.

Battery recycling is essential for the sustainable management of resources in a world increasingly dependent on non-fossil fuel energy sources. Although the process and related technologies are advancing rapidly, challenges persist. However, through continuous innovation and collaboration, the industry is moving closer to achieving closed-loop systems that maximize the value of used batteries. In the meantime, this approach minimizes the environmental impact of new battery production.