Yongli Cui

Electrochemical behavior of α-MoO3 nanobelts as cathode material for lithium ion batteries

Abstractα-MoO3 nanobelts were synthesized by simple hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV) and galvanostatic charge/discharge testing techniques were employed to evaluate electrochemical behaviors of α-MoO3 materials. Results showed that α-MoO3 nanobelts with about 80 nm in diameter and 5–12 μm in length were grown in the orthorhombic system. Electrochemical characterisation confirmed that in lithium ion insertion/extraction process, the first intercalation of lithium ion in α-MoO3 at about 2.8 V was irreversible, corresponding to LixMoO3 (0 < x ≤ 0.25) and the parent MoO3 materials coexisting, the second lithium ion inter-calation was reversible at the potential range of 2.2–2.4 V followed by LixMoO3 (0.25 < x ≤ 0.5), and below 1.0 V the mechanism of lithium ion storage changed from lithium ion intercalation reaction into lithium alloying reaction. The α-MoO3 nanobelts showed better electrochemical performance, 319 mA h g−1 initial discharge capacity, around 52% capacity retention after 20 cycles than that of α-MoO3 bulk.

Enhanced charge storage of Li3FeF6 with carbon nanotubes for lithium-ion batteries

Due to stability in the air, easy preparation process, lower cost and high reaction potential, Li3FeF6 is a promising cathodic material in lithium-ion batteries. However, the poor electronic conductivity of Li3FeF6 limits its performance in lithium-ion batteries. Conductive agent addition can improve the electronic conductivity of Li3FeF6 composite electrodes. The specific capacity of the Li3FeF6/C electrode is around 80 mA h g−1 (the highest value), corresponding to 0.57 Li+ embedding. While a specific capacity of the Li3FeF6/CNTs electrode of 120 mA h g−1 can be achieved, which is close to the theoretical capacity (140 mA h g−1), and the reversible capacity can be maintained at above 100 mA h g−1 after 50 cycles, with a capacity retention of 83%, which indicates greater electrochemical activity for such a CNT containing electrode. The enhanced performance of the Li3FeF6/CNTs electrode is due to the lower interface resistance and improved electrochemical activity of the Li3FeF6 active material.