Breakthrough Tech Yields 99% Pure Nickel, Cobalt

Abstract

Electrochemical recovery presents a sustainable route for battery recycling, yet it is hindered by a trade-off between achieving purity and yield. This challenge arises because, as the target metal depletes during electrodeposition, mass transport limitations reduce its availability, thereby shifting the electrochemical environment in favor of co-deposition of competing metal - particularly during prolonged deposition intended for near-complete recovery. Here, we report a strategy that leverages a multifunctional deep eutectic solvent (DES), ethaline, where ethylene glycol preferentially coordinates with nickel while chloride stabilizes cobalt as tetrachlorocobaltate complexes. Even at elevated temperatures, where nickel undergoes a partial thermochromic transition to chloride coordination, the system maintains a broadened Ni-Co separation window of ∼0.3 V at 85 °C. By fine-tuning the applied potential and utilizing the intrinsic chlorine redox activity of the DES, self-purification was achieved during electrodeposition, yielding a Ni/Co separation factor >3000 and >97 % nickel recovery in a single-step electrodeposition from a synthetic Ni/Co mixture. Building upon this binary separation, we developed a sequential strategy to recover nickel, cobalt, and manganese from real battery leachates. Applied to real NMC leachates, our process enabled the sequential recovery of nickel, cobalt, and manganese with purities of 99.1 %/96.3 % (NMC111) and 99.2 %/98.8 % (NMC811) for nickel and cobalt, respectively, all with >95 % recovery. For NMC111, >97 % nickel purity and >93 % cobalt purity were retained over repeated reuse of the DES, enabling minimal wastewater discharge, with Cl₂-assisted refining enhancing purity to >99.9 %. A technoeconomic analysis validated the economic feasibility and revealed further potential through thermal optimization.

A research team, affiliated with UNIST has unveiled an innovative recycling technology, capable of recovering over 95% of nickel and cobalt from waste batteries with a purity exceeding 99%. This advanced method addresses the limitations of conventional wet recycling processes, which often involve complex chemical procedures and generate large volumes of harmful wastewater. The new approach promises a more sustainable, high-efficiency solution that could transform the battery recycling industry.

Professor Kwiyong Kim and his research team from the Department of Civil, Urban, and Earth Environmental Engineering successfully demonstrated a selective electrochemical separation process utilizing a multifunctional special solvent. This breakthrough enables efficient recovery of nickel and cobalt from spent batteries through a single, environmentally friendly step.

Waste batteries are often called 'Urban Mines' due to their abundance of critical metals, such as nickel, cobalt, and manganese. However, the coexistence of multiple metals makes their separation challenging. Conventional methods rely on strong acids, like sulfuric acid and chemical extractants, which produce hazardous wastewater and involve multi-stage, energy-intensive processes.

The new electrochemical process minimizes chemical usage and wastewater production while enhancing both purity and recovery efficiency. By applying a controlled voltage to a liquid mixture containing crushed battery material, metal ions are selectively deposited as solid metals. This technique leverages the different voltages at which each metal ion reduces, enabling precise separation.

Specifically, the team overcame the common challenge of simultaneous co-deposition of nickel and cobalt-usually occurring at similar voltages-by employing a specialized co-solvent. Ethylene glycol in the solvent preferentially binds with nickel ions, while chloride ions stabilize cobalt as tetrachlorocobaltate complexes. This differential coordination shifts the reduction voltages, allowing nickel to be deposited at -0.45 V and cobalt at -0.9 V, effectively separating the two metals.

Figure 1. Schematic representation illustrating the key findings of the study.

An added advantage of this process is the natural formation of chlorine by-products, which selectively dissolve cobalt impurities. This in-situ self-purification enhances the purity of recovered nickel without the need for additional refining steps. The chlorine-containing solution can be safely vented, as it forms inert ions, and the solvent's hydrochloric acid content can be regenerated and reused, minimizing environmental impact.

When applied to real NCM (Nickel-Cobalt-Manganese) battery leachates, the process achieved recovery rates exceeding 95%, with separation purity surpassing 99.9% for both nickel and cobalt. Notably, the special solvent maintained performance over at least four reuse cycles, further reducing waste.

Professor Kim stated, "By overcoming the long-standing trade-off between purity and recovery rate in electrochemical separation, our method offers a sustainable and cost-effective solution. It minimizes chemical use and wastewater, contributing to a more sustainable battery recycling ecosystem."

The findings of this research have been published in the October 2025 issue of Energy Storage Materials and supported by the Ministry of Education, the National Research Foundation of Korea, and UNIST.

Journal Reference

Seongmin Choi, Kenta Motobayashi, Kwiyong Kim, et al., "Highly selective and near-complete electrochemical recovery of cobalt and nickel from spent batteries through multifunctional deep eutectic solvent," Energy Storage Mater., (2025).