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RISS 인기검색어
- 검색키워드
- 저자 : Wooseok Go (검색결과 1 건)
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Improvement of Mechanical Strength of NASICON Ceramic for its Application in Seawater Battery
Wooseok Go Ulsan National Institute of Science and Technology 2022 국내박사
While renewable energy is attracting attention, energy storage systems (ESSs) have been used to compensate for energy fluctuations in renewable energy. Currently, lithium-ion batteries (LIBs) are used as ESSs, but high prices and limited lithium sources are potential risks for LIBs. Seawater battery (SWB) have been developed as an alternative ESS. SWB utilizes sodium ions in natural seawater as an active material, providing the advantages of abundant raw materials, low price, and eco-friendliness. NASICON ceramic has been used as a solid electrolyte for the SWB, which exhibits good cycle performance. To improve the power output, the active area of the solid electrolyte should be increased. To form a large active area, small rectangular NASICON (4 cm2) ceramics are clustered using a polymer sealant and metal frame. Since the clustering induces a substantial inactive area (31%), a strategy to minimize the inactive area is required. A large-area NASICON (100 cm2) ceramic instead of clustering small NASICON ceramics is a prominent method. Then, the metal frame is not required, and the inactive area from the polymer sealant is minimized. However, the mechanical strength of the large-area ceramic becomes an important property, because the more amount of area is exposed to the potential mechanical force without metal frame. The mechanical strength of NASICON ceramic is determined by the largest defect which is determine by pore and fracture toughness. In this study, I improved mechanical properties of the NASICON ceramic by controlling size of defects and decreasing amount of ZrO2 phase so that the large-area NASICON ceramic can be a mechanically stable solid electrolyte for the seawater battery. In Chapter 2, the size of defect in the NASICON ceramic is controlled using spray-dried powder. The resulting large area NASICON ceramic exhibits improved mechanical strength and reliability, and its practical operation in an SWB is demonstrated. In Chapter 3, ZrO2-deficient NASICON ceramic is investigated to reduce amount of ZrO2 phase. The resulting reduced ZrO2 contents in microstructure of NASICON ceramic enhanced mechanical strength. Improved electrochemical performance of the SWB is also demonstrated. In Chapter 4, a tubular NASICON ceramic is developed for improving mechanical stability of the large-area NASICON ceramic. Owing to its shape, the NASICON ceramic endures higher external force. This demonstrates possibility of geometrical strategy for the large-area NASICON ceramic. Based on these results, the NASICON can be used as a mechanically stable solid electrolyte in the SWB. This research will contribute to the practical use and commercialization of SWB.
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