A study on the electrochemical properties of vanadium borate for negative electrode application of lithium Ion battery = 리튬 이온 이차전지의 음극재용 바나듐 붕산염의 전기화학적 특성에 대한 연구

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$VBO_3$ was recently introduced as an attractive negative electrode material with high gravimetric and volumetric capacity ($420mAhg^{-1}$ and $1533mAhml^{-1}$, respectively). However, $VBO_3$ is difficult to synthesize due to the easy oxidation of $V^{3+}$ to $V^{4+}$ or $V^{5+}$. Presently, $VBO_3$ fabrication requires calcinations and annealing in reductive gas flow at temperatures greater than 1200°C for a few days. In order to reduce the energy consumption, cost, and processing time, two simple and economic processes were introduced as alternative synthesis method for amorphous vanadium borate (α-vanadium borates) and for crystalline $VBO_3$, respectively. Melting and quenching method is used to prepare α-vanadium borates. And ball-milling and subsequent microwave heating process is used to obtain crystalline $VBO_3$. Vanadium borates of amorphous structure were tried to be synthesized using melt and quenching method by the addition of Li precursor as network modifier. Because of high vanadium content in α-vanadium borate, rapid quenching methods were used: water quenching (WQ) and air quenching (AQ), which resulted in cooling rates of about 1000 and 300 °C/s, respectively. α-vanadium borate were successfully synthesized from mixtures of $V_2O_3:B_2O_3:Li_2CO_3=1:1:x(x=1,2by mol)$ using water quenching method within one hour. With increase in Li precursor contents, $C_{out}$ of WQ α-vanadium borates increased up to 592 mAh $g^{-1}$ more than $C_{in}$ did. Therefore, $C_{in}$ was decreased from 472 to 430 mAh $g^{-1}$. This suggests that Li precursor occupied the part of the irreversible $Li^+$ insertion sites related to structural transformation, such as amorphization process of crystalline $VBO_3$ during $1^{st} Li^+$ insertion process. α-vanadium borate were successfully synthesized from mixtures of $V_2O_3$ : $B_2O_3:Li_2CO_3:AB(acetyleneBlack)=1:1:1:y(y=0,1,and 5 by mol.)$ using air quenching method within one hour. With increase in AB contents, ...
Advisors
Kwon, Hyuk-Sangresearcher권혁상researcher
Description
한국과학기술원 : 신소재공학과,
Publisher
한국과학기술원
Issue Date
2007
Identifier
268709/325007  / 020015811
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 신소재공학과, 2007. 8, [ xi, 135 p. ]

Keywords

Lithium ion battery; negative electrode material; microwave heating; ball-milling; vanadium borate; 리튬 이온 전지; 음극재; 마이크로 파 가열; 볼밀링; 바나듐 붕산염

URI
http://hdl.handle.net/10203/49648
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=268709&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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