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10/08/2018 HYU News > Academics > 이달의연구자

Title

[Researcher of the Month] Increasing Charging Efficiency in Lithium-ion Battery

Professor Park Won-il (Division of Materials Science and Engineering)

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When a new phone launches, one can visibly notice that one of the main improvements are longer battery life with a faster charging speed. Needless to say, batteries are a crucial part of an electronic device and there are continuous developments made in order to increase their efficiency. Likewise, Professor Park Won-il (Division of Materials Science and Engineering) carried out experiments and research on the negative electrodes of lithium-ion batteries to improve the efficiency of battery charging. Along with various others, Park wrote a thesis with the title “Controlling electric potential to inhibit solid-electrolyte interphase formation on nanowire anodes for ultra fast lithium-ion batteries.”

Professor Park Won-il (Division of Materials Science and Engineering) talks about how the experiments were carried out on the lithium-ion batteries.

The lithium-ion battery is well-known as it is included in most wireless devices such as electric cars. The lithium-ion battery contains both a cathode, which is the positively charged electrode for batteries and an anode electrolyte, a negatively charged electrode. Park’s research was focused on the materials of the anode electrolyte. When a battery is running, a potential drop occurs between the cathode and electrolyte anode. Due to this drop, a solid-electrolyte interphase layer forms on the active material surface. Park focused on researching the active material that goes in the anode electrolyte in order to increase battery charging efficiency. Originally, the basic material utilized was graphite, which has the capacity of 360 mAh/g (milliampere hours per gram). However, to follow the demand of a higher capacity material, Park decided to implement Nickel Silicide, the capacity of which is 1300 mAh/g, four times that of graphite.
 

Figure C shows how Nickel Silicide (NiSi) was utilized in order to inhibit solid-electrolyte interphase.
(Photo Courtesy of Park)

In the thesis, a three-dimensional macro graphite nano tube model to control the electric potential and prevent solid-electrolyte interphase utilizing Nickel Silicide was introduced. Solid-electrolyte interphase occurs when the  potential drop, established between cathode and anode, drives to decompose the electrolyte and form a solid-electrolyte interphase layer. This enabled the potential drop to take place on the potential sheath instead of the active material surface. After countless experiments, up to two thousand, utilizing Nickel Silicide showed outstanding performance under 20C, taking less than a minute to fully charge. The capacity of a battery is generally rated at 1C, which means that it takes one hour to fully charge. 
 

(From left) Chang Won-jun (Division of Materials Science and Engineering, '16) and Professor Park Won-il (Division of Materials Science and Engineering) mentioned that the experiment was carried out more than two thousand times.

When asked how long it took to complete the experiments, Chang Won-jun (Division of Materials Science and Engineering, ’16), who led the majority of experiments, said that they began in June of 2017, and their thesis submission and revision started at the end of December that year. Although the repetitive experiment proved that the performance of lithium-ion batteries utilizing Nickel Silicide was outstanding, deriving the precise evidence proving that solid-electrolyte interphase took place outside the surface was the task that took seven to eight months.
 

Park concluded more research is still needed. In the current state, it will take more time for the newly developed structure to work. However, he hopes for the concept to be utilized on the betterment of lithium-ion batteries and become a breakthrough for battery charging in the future.



Seok Ga-ram
       carpethediem@hanyang.ac.kr
Photos by Park Kuen-hyung

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