Yuan Yang, an assistant professor in Columbia University's School of Materials Science and Engineering, has developed an entirely new approach to improving the energy density of lithium-ion batteries. His three-layer structure electrode is stable in the bare air environment, thus making the battery more durable and further reducing the cost of manufacturing. The research, which could increase the energy density of lithium-ion batteries by 10-30%, was published in the journal NanoLetters in early October.
"When Li-ion batteries are charged for the first time, they lose up to 5-20% of their energy in the first cycle," said Yang Yuan. "Through structural improvements, we have been able to prevent this loss. At the same time, we The method has great potential for increasing battery life, with potential applications in portable electronics and electric vehicles."Also read:48v lithium ion battery 200ah
During the first charge after being produced, a portion of the electrolyte in a lithium-ion battery changes from liquid to solid due to a reduction reaction and attaches to the battery's negative electrode. This process is irreversible and reduces the battery's stored energy.
Under the existing electrode manufacturing technology, the loss caused by this process is about 10%, but for next-generation anode materials with high capacity, such as silicon, the loss will reach 20-30%, which will greatly reduce the battery actual available capacity.
To compensate for this initial loss, the traditional approach is to incorporate certain lithium-rich materials into the electrodes. However, since most of these materials are unstable in the air environment, they must be fabricated in dry air that is completely devoid of moisture, which greatly increases the manufacturing cost of the battery.
Comparison of graphite/PMMA/Li trilayer electrodes before (left) and after (right) soaking in battery electrolyte for 24 hours.
The three-layer electrode was stable in air before being immersed in the electrolyte. After soaking, lithium reacts with graphite and turns yellow in color.
The three-layer electrode structure developed by Yang Yuan ensures that the electrode can be completely fabricated in ordinary air environment.
First, he used a layer of "PMMA" (a common plexiglass material) to isolate lithium from contact with air and moisture; then a layer of active materials such as artificial graphite or silicon nanoparticles was added to the PMMA polymer; finally, He let the PMMA polymer layer dissolve in the battery electrolyte, which conducts the lithium to the electrode material.Also read:48v lithium ion battery 400ah
"In this way, we can prevent the air contact between the unstable lithium and lithiated electrodes," Yang Yuan explained. "The electrodes with this structure can be completed in a normal air environment, making it easier to achieve mass production of battery electrodes."
The production process of the three-layer structure electrode: PMMA in the initial state ensures that the lithium does not react with moisture in the air. After the PMMA is dissolved by the battery electrolyte, the graphite contacts the lithium to compensate for the initial loss due to the reduction of the electrolyte. :Columbia University
Yang Yuan's method reduces the loss of the existing graphite electrode from 8% to 0.3%, and the loss of the silicon electrode from 13% to -15% (a negative number indicates that the capacity of the battery is taught in the initial state due to the addition of new lithium materials. also added). The excess lithium can compensate for the capacity loss in subsequent cycles, thus further enhancing the cycle life of the battery.Also read:odm 300ah lifepo4 battery supplier
The energy density (or capacity) of lithium-ion batteries has maintained an annual increase rate of 5-7% in the past 25 years, and Yang Yuan's research results provide a feasible way to further increase this rate of increase. His team is now working to reduce the thickness of the PMMA coating to lower its proportion in lithium-ion batteries and strive for industrial production.
Hailiang Wang, assistant professor of chemistry at Yale University, said: "The three-layer electrode structure is very ingeniously designed to produce electrodes containing lithium metal in ordinary air environments. The initial Coulombic efficiency of electrodes has always been a major problem in the lithium-ion battery industry, so This simple and effective compensation technique is bound to be of great interest."