Nanostructured V 2 O 5 /Nitrogen-doped Graphene Hybrids for High Rate Lithium Storage
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.424
Nanostructured V2O5/Nitrogen-doped Graphene Hybrids for High Rate Lithium Storage Yiqun Yang, Kayla Strong, Gaind P. Pandey, Lamartine Meda
Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125
ABSTRACT Vanadium Pentoxide (V2O5) has been identified as a potential cathode material owning to its high specific capacity, theoretically, 441 mAh g-1 for 3Li+ ions insertion/extraction. However, the intrinsic drawbacks of V2O5, i.e. structural instability and poor electronic and ionic conductivity, greatly inhibit its application as a cathode. Here, we report a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal reaction to synthesize V2O5 nanoclusters. Unique aggregated fiber structure was obtained after annealing. To achieve a porous structure and increase the conductivity, nitrogen-doped Graphene (NG) suspended in ethylene glycol was added to the reaction mixture. The obtained spherical V2O5 nanoparticles and NG sheets were randomly dispersed in the matrix of the V2O5 spheres. As a cathode material for lithium-ion batteries, the V2O5/NG hybrids demonstrate better rate performance compared to the bundle-like V2O5 fibers, delivering higher specific capacity of ~ 300 and 150 mAh g-1 at a rate of C/10 and 5C, respectively. The enhanced performance in lithium storage are attributed to the synergistic effect of the nanostructured V 2O5/NG composites.
INTRODUCTION Vanadium pentoxide (V2O5) is considered as a promising cathode material for lithium-ion batteries (LIBs) owing to its high specific capacity. Theoretically, crystalline V2O5 can achieve a specific capacity of 294 mAh g-1 when storing 2Li+ ions per mol. of V2O5 and 440 mAh g-1 when storing 3Li+ ions, which is extremely high compared to current cathode materials, such as LiCoO2 (140 mAh g-1), LiMn2O4 (150 mAh g-1), and LiFePO4 (170 mAh g-1) [1]. However, bulk V2O5 exhibits inferior electronic conductivity (≈10−3 to 10−5 S cm−1) and very low lithium ion diffusion coefficient (≈10 −15 to 10−12 cm2 s−1). These drawbacks drastically affect the cycle and rate performances of this material. To overcome the intrinsic limitations, efforts have been taken to shorten the lithium diffusion pathway through synthesis of nanostructured V2O5 [2, 3], enhance the electron transport with conductive carbon additives such as amorphous carbon, carbon nanotubes (CNTs), graphene and reduced graphene oxide [4-8]. A more effective strategy is to combine the two efforts to prepare nanostructured V2O5/C composites [9-11]. Various preparation methods of nanostructured V 2O5 composites have been developed, such as sol-gel, physical deposition, solution method [12-15]. Among these, hydrothermal synthesis is found to be a simple one-pot method to attain nanostructured V2O5 or V2O5/C composites with different morphologies. In addition, a variety of
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