| Summary: | 碩士 === 國立中央大學 === 材料科學與工程研究所 === 104 === Hydrogenated transition metal oxides (TMOs) prepared via a hydrogenation treatment process have attracted increasing attention as electrodes in lithium ion batteries and supercapacitors, which is attributed to the improved electronic conductivity and electrochemical reactions kinetics. In this work, three different TiO2 phases including anatase (TiO2-A), bronze (TiO2-B), and rutile (TiO2-R) and their hydrogenated products (denoted with a prefix “H”) are investigated as electrodes in Li-, Na-, and Mg/Li-ion battery. We demonstrate, for the first time, the effects of hydrogenation treatment on electrochemical performances of TiO2 in Na- and Mg/Li-ion battery.
Our experimental results shows that hydrogenation treatment improves the capacity of anatase TiO2 in MLIBs up to 240 mAh/g (at 8.4 mA/g), which is 2 times higher than the raw TiO2. Furthermore, the high rate capabilities of anatase TiO2 (HTiO2-A) in LIBs (34 mAh/g at 10A/g), NIBs (94 mAh/g at 10A/g), and MLIBs (95 mAh/g at 1.68A/g) are enhanced as compared to the raw TiO2-A. Regarding the cycle stabilities of HTiO2-A, 74% capacity is retained after 500 cycles for LIBs, while 60% after 4300 cycles for NIBs and 83% after 200 cycles for MLIBs. All these results indicate the significant benefits of hydrogenation treatment on the anatase TiO2.
The enhanced performances might be explained by oxygen vacancies, disordered surface and Ti3+ ions created by hydrogenation process. The introduction of oxygen vacancies improves the electronic conductivity of materials, while the disordered surface may provide more active sites for electrochemical reactions. The combined effects of the disordered surface and Ti3+ induce pseudocapacitive lithium storage on the HTiO2 surface, which features much faster kinetics. However, hydrogenation treatment improves the electrochemical performances of the bronze and rutile phases only for NIBs, which is possibly attributed to phase transformation of the bronze phase and the larger particle size of the rutile phase.
Conclusively, hydrogenation treatment enhances electrochemical performances of transition metal oxides not only in LIBs but also in SIBs and MLIBs although the simultaneous phase transformation and particle size are needed to be concerned. In the future, the developed hydrogenation technique potentially extends to a variety of metal oxide electrodes in lithium, sodium, magnesium, and aluminum ion battery applications.
The experimental results show that the enhanced effect of hydrogenated treatment on transition metal oxides not only in lithium ion batteries but also in sodium ion battery and magnesium-lithium ion battery. Therefore, the developed hydrogenation technique potentially extends to a variety of metal oxide electrodes in lithium, sodium, magnesium, and aluminum ion battery applications.
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