Just as a pinch of salt can transform a dish's flavor, adding a tiny amount of material to a battery can simultaneously enhance both safety and lifespan, according to new research. The finding has drawn particular attention for its potential to address the biggest weakness of lithium metal batteries, considered a next-generation energy storage technology.
A research team led by Professor Kim Won-bae at POSTECH (Pohang University of Science and Technology) announced they successfully stabilized the internal structure of lithium metal batteries by adding trace amounts of aluminum salt (AlCl₃) to the liquid electrolyte. The findings were recently published in the international journal Advanced Science.
Lithium metal batteries can store far more energy than the lithium-ion batteries widely used today. In theory, they could dramatically extend electric vehicle driving range and power high-output transportation such as urban air mobility (UAM) vehicles. This is why lithium metal batteries are called "dream batteries." However, a critical weakness has blocked commercialization. During charging, metallic lithium accumulates unevenly on the surface, growing sharp crystals called "dendrites." Dendrites can penetrate the battery's interior, causing short circuits and potentially leading to fires or explosions. At the same time, electrolyte decomposition rapidly shortens battery lifespan.
The research team traced the root of these problems to the electrolyte's liquid state. In a liquid environment, lithium cannot accumulate evenly, making dendrite growth more likely. Rather than completely replacing the electrolyte, they chose a strategy of adding small amounts of additives to induce the electrolyte to restructure itself.
Experimental results showed that when trace amounts of aluminum salt were added to the electrolyte solvent 1,3-dioxolane, a polymer reaction occurred internally, transforming the liquid into a gel. This gel electrolyte formed a structure that reduced flow while maintaining pathways for lithium ion movement. In effect, it combined the fluidity of liquid with the stability of solid.
During this process, a protective layer (SEI) naturally formed on the lithium surface. Analysis revealed that a composite protective layer containing lithium fluoride, lithium chloride, and lithium-aluminum compounds suppressed dendrite growth. The team confirmed this mechanism through electrochemical experiments and molecular-level calculations.
Performance also improved. In battery tests using lithium iron phosphate (LFP) cathodes, the cells retained approximately 93% of initial capacity after 280 charge-discharge cycles. Stable operation was maintained even under fast-charging conditions 20 times faster than normal. This means the technology simultaneously achieved safety, longevity, and fast-charging performance.
The key to this research lies not in complex structural changes but in fine-tuning. The approach is highly regarded for its industrial scalability because it allows the internal environment to self-organize without significantly altering existing battery systems. "The critical factor was that small amounts of aluminum salt simultaneously drove gel electrolyte formation and interface stabilization," the research team said. "This could accelerate commercialization of high-energy lithium metal batteries."