Technology has been developed to create a battery that can travel 1,000 km without worrying about explosion by suppressing the generation of oxygen gas from lithium cathode materials, and it is expected that the development of long-distance driving batteries will become visible in the future.

UNIST announced on the 18th that Professor Hyunwook Lee's team from the Department of Energy and Chemical Engineering has identified the cause of oxygen generation in lithium, a new battery cathode material, and presented a material design principle to resolve this.

Lithium-ion batteries are theoretically capable of storing 30% to 70% more energy than conventional batteries through high-voltage charging of 4.5 V or higher.

In terms of electric vehicle driving range, it can travel up to 1,000 km on a single charge.

On the other hand, this material has a problem in that the risk of explosion increases as the oxygen (O-2) trapped inside the material is oxidized and released in gaseous form (O2) during the actual high-pressure charging process.

The research team analyzed that partial structural deformation occurs when oxygen is oxidized around 4.25 V, releasing oxygen gas, and proposed a design method for electrode materials that fundamentally prevents this oxygen oxidation.

Some of the transition metals in lithium materials have lower electronegativity.This is a strategy of substituting this metal element.

When the electronegativity difference between the two metal elements causes electrons to gather around the element with higher electronegativity, the number of available electrons in the transition metal increases, preventing oxygen from being oxidized.

On the other hand, in situations where the number of available electrons of the transition metal is insufficient, oxygen donates electrons instead and is oxidized and emitted in gaseous form.

“While previous studies focused on stabilizing oxidized oxygen to prevent it from being emitted as a gas, the difference in this study is that it focuses on preventing the oxidation of oxygen itself,” explained first author Dr. Minho Kim of UNIST (currently a postdoctoral researcher at UCLA, USA).

In addition, this change in electron density can increase the charging voltage through the inductive effect, thereby achieving high energy density.

Since energy density is proportional to the number of available electrons and the charging voltage, strategies that substitute transition metals allow batteries to store more energy per unit weight.

It is a similar principle to how the more water there is in a dam and the greater the drop, the more energy is stored.

The research team experimentally confirmed the oxygen oxidation inhibition effect of the transition metal substitution strategy.

Accelerator-based X-ray analysis results showed that when some of the ruthenium was replaced with nickel, oxygen gas production was significantly reduced. In addition, we theoretically proved that charge redistribution occurs using density functional calculations (DFT).

This study was conducted in collaboration with Professor Dong-Hwa Seo of KAIST, Chung-Ang University, Pohang Accelerator Laboratory, Professor Yuzhang Li of UCLA, UC Berkeley, and Lawrence Berkeley National Laboratory.

The accelerator-based X-ray analysis was conducted by Professor Jang Hae-seong of Chung-Ang University (joint first author), and the DFT theoretical calculations were led by Dr. Eun-ryeol Lee (joint first author) of Lawrence Berkeley National Laboratory in the United States.

Professor Lee Hyun-wook said, “We have presented the direction of material development to cathode material researchers by compiling the technology into a library through various experiments and theoretical analyses,” and “It will be helpful in developing long-distance driving battery materials that do not explode and have high energy density.”

This study was conducted with the support of the Korea Foundation for Advanced Studies' International Cooperation Development Program, and the results were published online on February 19 in Science Advances, a sister journal of Science, an internationally renowned journal published by the American Association for the Advancement of Science (AAAS).