Market and product

Compiled by Bao Hien

Recovering nickel, cobalt, manganese and lithium from spent lithium-ion batteries has so far relied mainly on two approaches: high-temperature smelting or leaching in concentrated inorganic acids. Both recover metals effectively, but they come with high energy costs, occupational safety risks and corrosive waste that is hard to treat. A research team in Australia has now published an alternative process that uses a “gentler” solvent yet still achieves metal recovery rates above 95%.

The “black mass”: where every recycling process starts

When spent lithium-ion batteries enter industrial recycling, the first step is usually to shred the whole battery – anode, cathode, electrolyte and casing – into a fine powder called “black mass.” This is a complex mixture of graphite, aluminum and copper together with the valuable metals to be recovered, such as nickel, cobalt, manganese and lithium, and it requires further chemical extraction to separate and refine each metal.

Conventional extraction methods typically recover only some of these metals. Strong inorganic acids also bring the risk of equipment corrosion, toxic gas release and highly acidic wastewater that is costly to treat.

The solution: combining deep eutectic solvents with electrochemical extraction

The team developed an integrated process that combines a deep eutectic solvent (DES) with chemical and electrochemical extraction steps. A deep eutectic solvent is formed from a mixture of two or more compounds and has a melting point considerably lower than that of each individual component. This property allows it to dissolve certain metals selectively under far milder conditions than concentrated inorganic acids.

According to the developers, combining the solvent with electrochemistry delivers high selectivity even for black mass of complex composition. In other words, each target metal can be separated individually, rather than yielding a mixture contaminated with impurities as some earlier methods do.

Results: recovery above 95%, with potential for electronic waste

Tests on industrial-scale black mass showed the new process achieving metal recovery above 95%, separating nickel, cobalt, manganese and lithium at high purity. Compared with existing methods, which the team describes as “limited in scope and efficiency, able to separate only certain materials,” the integrated process is considered more comprehensive.

Notably, the team believes the approach is not limited to lithium-ion batteries and could also be applied to recover valuable metals from other electronic waste and from mining tailings. These secondary resources are drawing growing interest as demand for metals used in batteries and electronics continues to rise.

Still at laboratory scale

Despite the promising early results, the team confirms the technology remains at laboratory scale and needs further development and assessment before commercial deployment. This is also a common challenge for many deep eutectic solvent technologies in battery recycling. Although they offer advantages in safety and lower emissions compared with conventional acids, several questions still need answers before the technology can compete at large scale: scaling up solvent production, whether the solvent can be reused over many processing cycles, and operating costs relative to acid processes already optimized in industry.