Improve the energy density of EV lithium battery-Lithium - Ion Battery Equipment

A New Method to Improve the Energy Density of EV Lithium Battery -Lithium - Ion Battery Equipment

Recently, South Korean researchers found that the performance of lithium air battery is closely related to the content of carbon dioxide. Related papers have been published in the Journal of the American Chemical Society. Researchers believe that Li2CO3 in the battery can be selectively used as the final product of the discharge reaction according to the dielectric properties of the electrolyte in the lithium air battery. In addition, they also verified that Li2CO3 can react reversibly in the lithium oxygen/carbon dioxide battery cycle.

Researchers believe that it is important to understand the chemical characteristics of CO2 in lithium air batteries and the use of CO2 in electrolyte dissolution for the development of lithium air batteries. In addition, based on Li2CO3, exploring the possibility of rechargeable lithium oxygen/carbon dioxide batteries has one of the greatest advantages - minimizing adverse reactions.

The maximum theoretical energy density of the lithium air battery is about 3500 watt hours/kg, which is a good power source for the energy storage system of the next generation of electric vehicles and can enable electric vehicles to achieve longer mileage. The structure of lithium air battery is based on a pair of intercalation electrodes. During charging, lithium ion moves from cathode to electrolyte and then anode; When discharging, the process is reversed.(Lithium - Ion Battery Equipment)

In order to reach the commercialization stage, lithium air battery still faces many problems in science and technology and engineering, including insufficient understanding of the reaction mechanism of the battery, unstable chemical performance of the electrolyte, short cycle life, low ion transfer rate and other factors, which to a large extent lead to the phenomenon of excessive battery load.

The researcher pointed out: "It is still unclear what will happen when lithium air batteries are tested in an oxygen free environment, because most of the previous studies were conducted in an oxygen free environment, and the impact of other components in the air on battery performance was ignored. Therefore, to prove the impact of carbon dioxide on lithium air batteries, it is necessary to create a greenhouse environment and study other components in the air one by one (Nitrogen, argon, water, carbon dioxide) on battery performance. "

Assuming that water can be removed through waterproof membrane (an important substance leading to electrolyte and anode degradation), carbon dioxide should have the most significant impact on the chemical characteristics of lithium air battery, which is more influential than other components in the air. The cathode voltage of traditional lithium air battery is 3V. When the surrounding environment contains argon and nitrogen, the 3V voltage cannot activate the electrochemical reaction, while carbon dioxide can withstand the electrochemical reaction due to its strong inertia.

The difference in chemical stability means that the final product Li2O2 will always be converted into Li2CO3 through carbon dioxide, and this irreversible reaction limits the cycle performance of lithium air batteries.

In addition, although the proportion of carbon dioxide in the air is not high, carbon dioxide is used in battery reaction because of its high solubility (50 times higher than oxygen). In order to further develop the lithium air battery technology, the impact of carbon dioxide and Li2CO3 on the performance of lithium air batteries must be taken into account.

The Korea Advanced Institute of Science and Technology and Seoul National University research team studied the reaction mechanism of lithium oxygen/carbon dioxide battery under various electrolyte conditions by using quantum mechanical simulation and experimental verification.

They found that a low dielectric electrolyte will form Li2O2, while a high dielectric electrolyte will activate carbon dioxide and produce Li2CO3. However, the unexpected result was that they found that high dielectrics such as dimethyl sulfide (DMSO) could make Li2CO3 react reversibly.

The researchers said that this discovery is very important because the formation of Li2CO3 in lithium air batteries cannot be prevented in the environment containing carbon dioxide. However, substances that can promote its reversible reaction have been found, which can make the cycle performance of batteries more stable.



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