POSTECH: Making Explosion-Free Batteries with Lithium Nitrate Protective Film

The demand for electric vehicles is increasing in line with the global movement to strengthen carbon emission regulations. Global automakers such as BMW, Volkswagen, Tesla, Volvo, and GM have announced their plans to increase the production of electric vehicles one after another. However, there are still safety concerns over battery explosion.

Recently, a research team led by Professor Soojin Park, Dr. Jung-In Lee, and Ph.D. candidate Sungjin Cho of POSTECH’s Department of Chemistry has succeeded in fabricating a lithium metal protective film with a simple manufacturing method without changing the existing battery manufacturing system. In addition, the team proposed a new method for producing a lithium metal battery capable of stably achieving high energy density even in a commonly used carbonate-based electrolyte. The findings from this research were recently introduced in the online edition of Energy Storage Materials, an international academic journal.

Lithium metal is a battery cathode that can achieve high energy density. However, it has an inherent disadvantage of causing unpredictable reactions against carbonate-based electrolytes due to its high reactivity, and consequently greatly reducing the stability of the battery.
To this, the research team produced a lithium metal battery that exhibits high stability and performance even in carbonate-based electrolytes by fabricating a micelle*1 block copolymer (poly(styrene-block-2-vinylpyridine)) protective film in which ionized lithium nitrate is bound by electrostatic attraction.

The micelle protective film formed a solid electrolyte interface with high ion conductivity while preventing direct contact between the lithium metal and the electrolyte, and stably induced a model of lithium that is initially electrodeposited*2. In addition, it has been shown to maintain stable high-efficiencies over 100 cycles at high temperatures even when using the common carbonate-based electrolyte.

Additionally, in an evaluation conducted under severe conditions using a thin lithium anode (40μm), high area capacity (4.0 mAh cm−2), and high current density (4.0 mA cm−2), the battery showed long-stable cycling over 300 cycles and showed similar performance in the pouch-type full cell.

“The lithium metal anode is a material that is in the spotlight as a next-generation anode material due to its high energy density, but due to its poor stability, it has been difficult to commercialize,” explained Professor Soojin Park. “In general, lithium anode batteries are relatively unstable in carbonate-based electrolytes, but this study solved that issue.”

“It looks promising to lithium metal battery system that is suitable for large areas, such as manufacturing a pouch cell, and operates stably even at high temperatures.” It is expected to realize a lithium metal battery system that is suitable for large areas like pouch cell fabrication and stably operates even at high temperatures.

This research was conducted with support from the Basic Science Research Program, President Post-Doc. Fellowship Program, and the Technology Development Program to Solve Climate Changes funded by the Ministry of Science and ICT.

1. Micelle
Microcrystalline particles that constitute amorphous materials such as polymer materials

2. Electrodeposition
Placing an electrode plate in a solution and applying a direct current voltage to attach a substance to the electrode surface. A type of plating method.

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