Development and characterization of tungstates and molybdates for li-ion batteries

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2016

Öğrenci: BURÇİN KAYGUSUZ

Danışman: MEHMET KADRİ AYDINOL

Özet:

In recent years, the need for portable power, lithium ion batteries dominate the markets because of their advantages. Metal tungstates and molybdates (Metals: Fe, Ni, Co, Mn, Zn, Mg) are two important families of inorganic materials and have found many applications in various fields, such as catalysis, magnetic applications, humidity sensors, and photoluminescence. However, their use in energy storage applications is almost none. The tungstates and molybdates adapt monoclinic crystal structure and crystallize in P2/c and C2/m space group, respectively. Both structures have tunnels along certain crystal directions. Due to this unique crystal feature they are suitable for Li ion transport and intercalation, which has importance in Li-ion battery development. In this study, metal molybdates and tungstates were produced by sol-gel method. The structure of the obtained powders was investigated with X-Ray Diffraction and Scanning Electron Microscopy. These materials were used as active material against metallic lithium in a battery cell and the cells were characterized by using galvanostatic charge-discharge tests and electrochemical impedance spectroscopy. According to results, metal tungstates and molybdates have high capacity for few cycles and then capacity loss was observed. It needs further intensive investigation to understand the lithium insertion mechanisms underlying, so as to improve cycle life to make it a commercially available material.