Eco-friendly upcycling: Turning spent batteries into high-voltage energy storage systems

As electric vehicles and energy storage systems (ESS) become increasingly widespread, the management and recycling of spent lithium-ion batteries has emerged as a pressing global issue. Traditional recycling methods, such as energy-intensive smelting or chemically aggressive wet processes, require significant energy and pose environmental risks.

A research team led by Dr. Yosep Han at the Korea Institute of Geoscience and Mineral Resources (KIGAM) has successfully developed an eco-friendly electrochemical process to upcycle lithium manganese oxide (LiMn₂O₄, LMO), a common cathode material in spent lithium-ion batteries. This process was directly integrated into a zinc–manganese redox flow battery (Zn–Mn RFB), a promising next-generation energy storage system, demonstrating its practical feasibility.

The paper is published in the journal Small.

Unlike conventional recycling that focuses on metal recovery, this method electrochemically converts LMO into manganese ions (Mn²⁺), which are then used as electrolytes for redox flow batteries. The team’s innovation represents a substantial shift toward value-added recycling, moving beyond simple resource recovery, enabling a circular battery ecosystem.

This approach also allows manganese and lithium to be selectively separated by simply adjusting the electrolyte’s pH, further facilitating material reuse. The technology enables spent batteries to serve as a direct source of electrolyte and subsequently be reconverted into precursor materials for new batteries—laying the groundwork for a sustainable, closed-loop battery lifecycle.

Traditional recovery processes typically rely on high-temperature (over 900 °C) smelting or strong-acid-based hydrometallurgy, which require substantial energy and pose environmental risks. In contrast, the new method developed by KIGAM eliminates the need for thermal or chemical extremes, significantly reducing both energy consumption and ecological impact.

Rather than decomposing the LMO material, the researchers guided it through an electrochemical conversion into Mn²⁺ ions and integrated it into the battery’s electrolyte. The result: comparable initial performance to commercial MnSO₄-based electrolytes, and over 70% energy efficiency retained after 250 charge/discharge cycles.

Moreover, the team applied a dual-membrane hybrid redox flow battery architecture to achieve high operating voltage and extended cycle life—key requirements for the commercialization of large-scale, long-duration energy storage systems.

“This research overcomes the complexity and environmental drawbacks of existing battery recycling technologies,” said Dr. Yosep Han. “We aim to further enhance battery resource circularity and energy storage efficiency, contributing to carbon neutrality and a recycling-oriented society.”