A study on the electrochemical properties of vanadium borate for negative electrode application of lithium Ion battery

Abstract

$VBO_3$ 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, ...