Blocking Oxygen Extends EV Battery Life by 2.8x

Abstract

High-voltage operation of Ni-rich layered cathodes in lithium-ion batteries (LIBs) induces oxygen redox reactions, leading to singlet oxygen evolution, interfacial degradation, and electrolyte decomposition. While cathode engineering has been extensively explored to mitigate these challenges, electrolyte-based strategies for directly regulating oxygen redox remain limited. To address this limitation, an anthracene-functionalized cyanoethyl polyvinyl alcohol (An-PVA-CN) gel polymer electrolyte (GPE) is developed, offering dual functionalities: anchoring oxidized surface oxygen and scavenging singlet oxygen. The anthracene moiety binds to oxidized lattice oxygen prior to O-O dimer formation, forming a stable Ni─O─C bridging structure that suppresses singlet oxygen release. It also acts as an effective scavenger for any singlet oxygen generated. Simultaneously, the electron-rich nitrile groups coordinate with transition metals, suppressing over-oxidation of Ni during charging. Spectroscopic and computational analyses confirm the suppression of oxygen redox and stabilization of surface oxygen species. By regulating charge compensation via transition metal redox while inhibiting oxygen redox, oxygen gas evolution and transition metal dissolution are effectively mitigated. As a result, An-PVA-CN GPE enables 81% capacity retention over 500 cycles at 4.55 V in full-cell configurations. This work demonstrates a rare electrolyte-centered approach to oxygen redox regulation and offers a promising design strategy for stabilizing high-voltage LIBs.

A research team, affiliated with UNIST has introduced a groundbreaking gel-like material that could extend the lifespan and enhance the safety of high-voltage electric vehicle (EV) batteries designed for long-distance driving. This innovative electrolyte actively prevents the generation of reactive oxygen species (ROS), the primary cause of battery aging, resulting in a 2.8-fold increase in battery lifespan and a reduction in swelling by one-sixth.

Led by Professor Hyun-Kon Song from the School of Energy and Chemical Engineering at UNIST, in collaboration with Dr. Seo-Hyun Jung of the Korea Research Institute of Chemical Technology (KRICT) and Dr. Chihyun Hwang of the Korea Electronics Technology Institute (KETI), the research team developed an anthracene-based semi-solid gel electrolyte (An-PVA-CN) gel polymer electrolyte (GPE) that fundamentally blocks the release of ROS from the electrodes during high-voltage charging.

High-voltage lithium-ion batteries (LIBs), charged above 4.4V, enable greater energy storage, but also pose risks. The increased voltage destabilizes oxygen in the nickel-rich cathode, converting it into ROS that produce gases, heightening the risk of explosions and shortening battery life.

Figure 1. Schematic features of the anthracene moiety: surface oxygen anchoring and singlet oxygen scavenging.

The new electrolyte's anthracene component binds with unstable surface oxygen, preventing it from forming ROS, called single oxygen (¹O₂), which act as seeds for further degradation. Additionally, anthracene captures and removes existing reactive oxygen, providing a dual layer of protection.

Another key component, the nitrile (-CN) group, stabilizes nickel metal in the cathode, preventing dissolution and structural deformation during charging.

First author Jeongin Lee explained, "What sets this research apart is that it directly prevents the formation of ROS at the source," adding, "Previous approaches either neutralized ROS after they formed or manipulated the electrode to suppress oxygen release."

Batteries equipped with this electrolyte maintained 81% of their initial capacity after 500 charge-discharge cycles at a high voltage of 4.55V, whereas conventional batteries dropped below 80% capacity after only 180 cycles. This indicates a nearly threefold increase in lifespan. Furthermore, gas evolution-and consequently, swelling-was significantly reduced; the gel electrolyte limited expansion to approximately 13 micrometers, compared to 85 micrometers in conventional batteries, achieving about a sixfold reduction.

Professor Song stated, "This study demonstrates that oxygen reactions in high-voltage batteries can be controlled at the electrolyte design stage," and added, "This principle could be applied to develop lightweight LIBs for aerospace applications and large-scale energy storage systems."

The findings of this research have been published in the online version of Advanced Energy Materials on October 5, 2025. The study was supported by the InnoCore program of Hydro*Studio at UNIST, the KEIT, and the KRICT.

Journal Reference

Jeongin Lee, Jihyun Kim, Daehyun Kim, et al., "Electrolyte-Driven Suppression of Oxygen Dimerization and Oxygen Evolution in High-Voltage Li-Ion Batteries," Adv. Energy Mater., (2025).