Korean researchers recently discovered that the performance of lithium-air batteries is related to the carbon dioxide content. The researchers believe that the Li2CO3 in the battery can be selectively used as the final product of the discharge reaction depending on the dielectric properties of the electrolyte in the lithium air battery. In addition, they also verified that Li2CO3 is capable of reversible reactions in the lithium-oxygen/carbon dioxide cell cycle.
According to the report of China Nonferrous Metals Net on June 26, relevant papers have been published in the Journal of the American Chemical Society. Researchers believe that understanding the chemical properties of CO2 in lithium-air batteries and the role of carbon dioxide in the dissolution of electrolytes are important for the development of lithium-air batteries. In addition, the possibility of exploring a rechargeable lithium-oxygen/carbon dioxide battery based on Li2CO3 has one of the biggest advantages - minimizing adverse reactions.
The highest theoretical energy density of lithium-air batteries is approximately 3,500 Wh/kg, which is a good power source for the next generation of electric vehicle energy storage systems, enabling electric vehicles to achieve longer range mileage. The structure of the lithium air battery is based on a pair of intercalation electrodes. During charging, lithium ions move from the cathode to the electrolyte and then into the anode; during discharge, the process reverses.
Lithium-air batteries are still faced with many technical and engineering challenges in the commercialization stage, including insufficient understanding of the battery reaction mechanism, unstable electrolyte electrolyte properties, short cycle life, and low ion transmission rates. To a large extent, the battery is overloaded.
The researchers pointed out: “It is not yet known what happens when lithium-air batteries are tested in an oxygen-free environment because most of the previous research was conducted under aerobic conditions and other components in the air were The impact of performance is negligible, so to prove the impact of CO2 on lithium-air batteries, we must create a greenhouse environment and study the effects of other components of the air (nitrogen, argon, water, and carbon dioxide) on battery performance.â€
Assuming that moisture can be removed through the waterproof membrane (the main substance that causes deterioration of the electrolyte and the anode), carbon dioxide should have the most significant influence on the chemical characteristics of the lithium-air battery, exceeding the influence of other components in the air. The cathode voltage of a traditional lithium-air battery is 3 volts. When the surrounding environment contains argon and nitrogen, the 3 volt voltage cannot activate the electrochemical reaction, and carbon dioxide can withstand the electrochemical reaction due to its strong inertness.
The difference in chemical stability means that the final product, Li2O2, is always converted to Li2CO3 by carbon dioxide, and this irreversible reaction limits the cycling performance of the lithium-air battery.
In addition, although the proportion of carbon dioxide in air is not high, because carbon dioxide has high solubility (50 times higher than oxygen), it is applied to battery reactions. In order to further develop lithium-air battery technology, the impact of carbon dioxide and Li2CO3 on the performance of lithium-air batteries must be taken into account.
Researchers at the Korea Advanced Institute of Science and Technology and Seoul National University have studied lithium-oxygen/carbon dioxide batteries under various electrolyte conditions using quantum mechanical simulation and experimental verification. The reaction mechanism.
They found that a low-dielectric electrolyte forms Li2O2, and the high dielectric electrolyte activates carbon dioxide to produce Li2CO3. However, the unexpected result was that they found that high dielectrics such as dimethyl sulfoxide (DMSO) could make Li2CO3 reversible.
The researchers said that this discovery is very important because in the environment containing carbon dioxide, the formation of Li2CO3 in lithium-air batteries is unavoidable. However, substances that can promote reversible reactions have been discovered so that the cycle performance of the batteries can be improved. stable.
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