세미나안내

[2014 04 17] 특별세미나 (BK21PLUS)

High-performance electrochemical energy systems from a mechanical perspective

MSE Graduate Students and Researchers

관리자 | 2014.04.02 11:30 | 조회 2601


Reception: MSE Graduate Students and Researchers

Reference: MSE Professors

Subject: [기계공학과] BK21+ Mechanical Eng. SEMINAR

 

■ Date: April. 17th(Thu) 17:00~

■ Place: #108 at 5th Engineering Bldg.

■ Title: High-performance electrochemical energy systems from a mechanical perspective

■ Speaker: Dr. Seok Woo Lee (Geballe Laboratory for Advanced Materials, Stanford Univ.)

■ Host of a Seminar. Dong Sung Kim (279-2183)
■ Language : Korean

 

In this talk, I will discuss how mechanical engineering can contribute to the development of electrode materials for high-density Li-ion batteries and high-efficiency electrochemical systems for thermal energy harvesting.
A battery is one of the representative electrochemical systems studied widely for energy storage applications. Specifically, Li-ion batteries are becoming an essential component in mobile electronic devices and electric vehicles, as smaller, lighter, and longer energy storage is required. Silicon is considered as one of the most promising anode materials for Li-ion batteries because of its exceptional specific capacity of 4200 mAh g-1, which is about ten times that of commercial graphite anodes. However, conventional Si anodes typically suffer from rapid capacity decay due to mechanical fracture caused by large volume changes (300%) during repeated electrochemical lithium insertion and extraction. In the first part of the talk, the fracture behavior of crystalline Si nanostructures during electrochemical lithiation will be shown, and the influence of volume expansion and stress on pillar fracture will be discussed. Lithiation of crystalline silicon nanopillars reveals anomalous anisotropic expansion and corresponding fracture behavior, and the observed behavior is explained by numerical analysis. In-situ TEM studies show how the mechanical interaction of silicon nanopillar structures during lithiation can affect volume expansion and fracture behavior when the pillars are placed in confined media, which is representative of electrode materials in actual (close-packed) battery cell configurations.
Efficient and low-cost thermal energy harvesting systems are needed to utilize the tremendous amount of energy stored in low-grade heat sources (< 100 °C). Although thermoelectric devices are attractive, the system efficiency is low due to the relatively low figure-of-merit and low temperature difference, which also challenges thermal management in addition to limiting the Carnot efficiency. A different approach is to explore thermodynamic cycles as is common in thermomechanical engines. The thermogalvanic effect, the dependence of an electrode’s electrochemical potential on temperature, can be used for such cycles. In the second part of the talk, the electrochemical thermodynamic cycle for thermal energy harvesting will be introduced. By utilizing novel electrode materials, this system can achieve very high efficiencies at low temperature ranges.

 

 

Division of Mechanical Engineering for Creative Emerging Technologies / MSE BK21+





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