“A single molecular layer” makes lithium batteries safer and longer-lasting

A team of Korean scientists has developed a breakthrough separator technology that dramatically reduces the explosion risk of lithium batteries while doubling their lifespan. Like an ultra-thin bulletproof vest protecting both sides, this molecularly engineered membrane stabilizes both the anode and cathode in next-generation lithium-metal batteries.

The joint research, led by Professor Soojin Park and Dr. Dong-Yeob Han from the Department of Chemistry at POSTECH, together with Professor Tae Kyung Lee of Gyeongsang National University and Dr. Gyujin Song of the Korea Institute of Energy Research (KIER), was recently published in Energy & Environmental Science, one of the world’s leading journals in energy materials.

Conventional lithium-ion batteries, which power today’s electric vehicles and energy storage systems, are approaching their theoretical energy limits. In contrast, lithium-metal batteries can store about 1.5 times more energy within the same volume, potentially extending an electric vehicle’s driving range from 400 km to approximately 700 km per charge. However, their practical use has been hindered by serious safety issues.

During charging, lithium tends to deposit unevenly on the anode surface, forming sharp, tree-like structures called dendrites. These needle-like growths can pierce the separator between electrodes, causing internal short circuits, fires, and even explosions.

To address this, the research team engineered the separator at the molecular level. They chemically grafted fluorine (-F) and oxygen (-O) functional groups onto the surface of a conventional polyolefin separator. These polar groups regulate interfacial reactions between the electrodes and electrolyte, promoting stable and uniform behavior on both sides.

As a result, a uniform layer of lithium fluoride (LiF) forms on the anode, suppressing dendrite growth, while harmful hydrofluoric acid (HF) formation is prevented at the cathode side, preserving its structural integrity. This single functional membrane acts as a dual protective layer, simultaneously stabilizing both electrodes within the battery.

Under realistic operating conditions, high temperature (55 °C), low electrolyte content, and a thin lithium anode, the newly developed batteries maintained 80% of their initial capacity after 208 charge–discharge cycles. In pouch-type full cells, the technology achieved impressive energy densities of 385.1 Wh kg⁻¹ and 1135.6 Wh L⁻¹, approximately 1.5–1.7 times higher than today’s commercial lithium-ion batteries (250 Wh kg⁻¹, 650 Wh L⁻¹).

Professor Soojin Park of POSTECH stated, “This study demonstrates an innovative approach that stabilizes both electrodes of lithium-metal batteries through molecular-level design. It improves lifespan, safety, and energy density while remaining compatible with existing lithium-ion battery manufacturing processes.”

Professor Tae Kyung Lee of Gyeongsang National University added, “Using density functional theory (DFT) and molecular dynamics (MD) simulations, we identified how functional groups in the separator influence electronic structures and interfacial reactions at the atomic scale.”

Dr. Gyujin Song of KIER commented, “This technology offers high durability and safety suitable for large-scale energy storage systems (ESS) and represents a major step toward the commercialization of eco-friendly, high-energy batteries.”

This research was supported by the Ministry of Science and ICT (MSIT) and Ministry of Trade, Industry and Energy of Korea.