การสังเคราะห์และการหาลักษณะเฉพาะทางไฟฟ้าเคมีของลิเทียม (M= V, Fe) ซิลิเกตจากซิลิกาบริสุทธื์และเถ้าแกลบ

Abstract

The synthesis of lithium metal silicate compounds can be performed by the solid-state reaction and heated by a microwave using lithium nitrate, vanadium (III, IV, V) oxide or iron (II) oxalate, pure silica and silica from rice husk ash (RHA) as precursors in the mole ratio of LiNO3: metal: sillica of 1:2:7. The conditions were studied by varying the grinding time for 1-6 hr and microwave heating at 400 and 600 watts for 5 and 10 min. Fourier transform infrared spectroscopy and resonance Raman spectroscopy were used to investigate of the vibration of Si−O, Fe−O, Li−O, V−O−V, V=O and Si−O−Si bonds. X-ray diffractometry technique confirmed the formation of a crystalline phase. When using lithium nitrate, vanadium oxide and pure silica as a precursor, The products were found to be Li2(VO)SiO4 and Li3.6Si0.6V0.4O4. Li3.6Si0.6V0.4O4 was only obtained when using RHA-based silica.The analysis of the product by X-ray absorption near-edge structure indicated that the oxidation of vanadium was V4+ and V5+. Also, the oxidation state of iron was Fe3+. The specific capacitance was calculated from the results of cyclic voltammetric measurements. The phase of Li3.6Si0.6V0.4O4 was found to have a specific capacitance greater than Li2(VO)SiO4 phase. Moreover, the product synthesized from pure silica precursor exhibited a specific capacitance of 375 F/g. While the product from RHA-based, the specific capacitance was 613 F/g.