Facile Synthesis of MoO3 Nanobelts with Carbon Dispersed Structure and Its Application As Anode of Lithium Ion Batteries

Lithium ion batteries (LIBs) have been successfully regarded as excellent power sources for energy conversion and storage technology, due to their high energy density, long lifespan, no memory and environmental benignity ^[1]. Transition metal oxides have been regarded as promising candidates for anode materials of LIBs due to their high theoretical capacity ^[2]. Molybdenum oxides (MoO₃ or MoO₂) have attracted enormous interest in recent decades, owing to their high thermal chemical stabilities and high theoretical capacity (e.g. 1117 mAh g^-1 for MoO₃ and 838 mAh g^-1 for MoO₂) ^[3]. In this paper, we design and fabricate a carbon dispersed structured α-MoO₃ nanobelts by a facile hydrothermal method. The addition of activated carbon is in an attempt to address the poor conductivity and also prevent the aggregation of the α-MoO₃, consequently improve the rate capability and cycling stability of α-MoO₃ anode materials.

The prepared MoO₃/C nanobelts are systematically characterized by XRD, FTIR, TGA, SEM, TEM, and EDS techniques, and the electrochemical performance is investigated by CV and constant current discharge-charge test techniques.

XRD analysis reveals that the as-synthesized material is α-MoO₃. The addition of activated carbon has no influence on the crystal structure of α-MoO₃. The peak positions of MoO₃/C are as same as the pure MoO₃, indicating that the existence of carbon does not affect the lattice structure of MoO₃. FTIR analysis confirms the presence of carbon in the composite. The carbon content in MoO₃/C composite was determined to be about 7.85% on the basis of the TGA analysis. The MoO₃ and MoO₃/C samples are investigated as anode materials for LIBs. When tested at a current density of 100 mA g^-1 between 0.01-3.0 V, the MoO₃/C anode exhibits a much better cycling performance than the MoO₃ anode, delivering a higher discharge capacity of ~1000 mAh g^-1 after 50 cycles. In contrast, the capacity of pure MoO₃ decreased continuously with the increasing number of cycles, only remains 632 mAh g^-1 after 50 cycles. The improved cycling performance of MoO₃/C can be attributed to the presence of activated carbon, which improves electronic conductivity. Moreover, the activated carbon prevents MoO₃ nanobelts agglomeration and acts as a sponge for relieving the large volume change during cycling, thus further enhance the structural stability.

In summary, α-MoO₃ nanobelts with carbon dispersed structure can be fabricated through a one-pot hydrothermal method. When evaluated as anode materials for LIBs, the MoO₃/C exhibit exceptional high specific capacity and outstanding rate capability The results suggested this kind of composite could become a promising candidate for anode materials of high-performance lithium ion batteries.

References

[1] Zhou X, Wan L J, Guo Y G. Advanced Materials, 2013, 25(15): 2152-2157.

[2] Armand M, Tarascon J M. Nature, 2008, 451(7179): 652-657.

[3] W. Wen and J. Wu, Appl. Mater. Interfaces (2011) 4112.