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South Korean researchers develop new battery recycling process

South Korean researchers have developed a process that could overcome one of the major obstacles in directly recycling used batteries by completely separating current collectors from cathode material.

The Korea Institute of Energy Research said Tuesday that a team led by researchers at its Gwangju Clean Energy Research Center developed the new separation technology.

A current collector is a conductive component that helps electricity flow through a battery.

It is bonded tightly to electrode materials so that it does not separate during repeated charging and discharging.

That strong adhesion, however, creates difficulties during recycling. Conventional processes can require specialized solvents containing hazardous chemicals to dissolve the bonding material.

Residues from the process can also be absorbed into recycled material and reduce the performance of reconstructed electrodes.

As the adoption of electric vehicles (EVs) continues to grow, the disposal of spent EV batteries is emerging as a major social and environmental challenge. Wastewater generated during conventional battery recycling processes can contain high concentrations of heavy metals, posing risks of soil and groundwater contamination.

Cathode materials*, which play a key role in determining battery capacity, also contain significant amounts of costly critical metals such as cobalt, whose extraction can cause environmental damage. As a result, direct recycling technologies for spent batteries, which can preserve the existing structure of battery materials while recovering valuable resources, are gaining increasing attention.

* Cathode material: A key battery component that stores and releases lithium ions during charging and discharging, playing an essential role in the generation of electrical energy

Against this backdrop, a research team led by Dr. Jung-Je Woo of the Gwangju Clean Energy Research Center at the Korea Institute of Energy Research (KIER) has developed a technology that completely separates current collectors, one of the major technical challenges in the direct recycling of spent batteries. The team also succeeded in simultaneously regenerating spent cathode materials to a performance level comparable to that of pristine materials.

The key to the newly developed technology lies in the complete separation of the current collector from the cathode material. Current collectors facilitate the flow of electricity within batteries and are strongly bonded to cathode materials so that they remain firmly attached during repeated charging and discharging. During battery recycling, however, this strong adhesion has traditionally required the use of specialized solutions containing hazardous chemicals to dissolve the bonding components. In addition, residual substances generated during this process can remain on the cathode material, potentially degrading the performance of the regenerated electrodes. As a result, current collector separation has remained a major challenge in direct battery recycling.

Researchers discuss the technology developed by the team(image above). Credit:KOREA INSTITUTE OF ENERGY RESEARCH

To overcome this limitation, the research team developed a solution-based recycling process. When spent cathode materials are immersed in a diethylene glycol solution and heated to 130°C, the diethylene glycol undergoes oxidation to form glycolaldehyde. Because glycolaldehyde readily interacts with other molecules, it weakens the adhesion between the cathode material and the current collector, enabling complete separation of the current collector. At the same time, electrons generated during the oxidation of diethylene glycol facilitate the replenishment of lithium ions in the cathode material, enabling delamination and regeneration occur simultaneously in a single step.

Using the developed process, the researchers regenerated NCM and LFP cathode materials, both widely used in electric vehicles. The regenerated NCM cathode recovered 99.1% of the capacity of pristine material, while the regenerated LFP cathode recovered 99.7%, demonstrating performance nearly equivalent to that of pristine cathode materials.

* NCM: A lithium-ion battery cathode material containing nickel, cobalt, and manganese.

* LFP: A lithium-ion battery cathode material containing lithium, iron, and phosphate (lithium iron phosphate).

The researchers also applied the technology to degraded cathode material from a 50-ampere-hour (Ah) EV battery and fabricated it to a small pouch cell using the regenerated material. The discharge capacity increased from 30.6 milliampere-hours (mAh) to 34.6 mAh, demonstrating the potential of the technology for regenerating cathode materials recovered from actual EV batteries.

Dr. Jinju Song of KIER, who led the study, said, “This technology enables spent battery cathode materials to be recycled without dissolving the active material, making it an environmentally friendly approach that can reduce both wastewater-related pollution and energy consumption.” She added, “The process is simple and does not require specialized sealed processing environments, giving it strong potential for industrial application.”

To address the problem, the researchers developed a solution-based recycling method using diethylene glycol.

When used cathode material is immersed in diethylene glycol and heated to 130 degrees Celsius, or 266 degrees Fahrenheit, oxidation converts part of the solution into glycolaldehyde.

Because glycolaldehyde readily bonds with other molecules, it weakens adhesion between the cathode material and the current collector, allowing the collector to be completely separated, the institute said.

At the same time, electrons released as the diethylene glycol oxidizes can help recharge lithium ions into the cathode material.

Tests using nickel-cobalt-manganese, or NCM, cathodes and lithium iron phosphate, or LFP, cathodes used in electric vehicles showed that the process restored the NCM material to 99.1% of the capacity of new material and the LFP material to 99.7%.

Researchers also restored degraded cathode material taken from a 50-ampere-hour electric vehicle battery and tested it in a small cell.

Discharge capacity increased from 30.6 milliampere-hours to 34.6 milliampere-hours, demonstrating potential application to batteries used in electric vehicles, according to the institute.

"This technology allows used battery cathode materials to be recycled without dissolving them, reducing environmental pollution from wastewater while also lowering energy consumption," researcher Song Jin-joo said.

"The process is simple and does not require a sealed operating environment, giving it strong potential for industrial application," Song said.

Korea Institute of Energy Research