Synthesis And Electrochemical Properties Of Vanadium Based Nanomaterials For Lithium- And Sodium-ion Batteries

Rechargeable lithium-ion batteries（LIBs）and sodium-ion batteries（SIBs）are regarded as the most promising electrochemical energy storage systems because of the high energy densities,long cycle life,and environmental friendliness.The charge storage performance of batteries depends on the electrode materials and so development of high-performance electrode materials is imperative.Vanadium-based oxides are promising anode materials in LIBs and SIBs due to their high oxidation state,variable valence and high theoretical capacity.However,the low electrical conductivity and poor electrochemical stability of the V-based oxides limit its electrochemical performance.To improve its electrical conductivity and electrochemical utilization ratio,we synthesized V₂O₃/NG hybrid nanobelts and Li₃VO₄/NC nanobelts and investigated their electrochemical properties.The main contents and highlights in our paper are summarized as follows:（1）First of all,we prepared VO_x/3-phenylpropylamine hybrid nanobelts via hydrothermal treatment using V₂O₅ and 3-phenylpropylamine as raw materials.Then,the hybrid V₂O₃/NG nanobelts were synthesized by one-step controlled pyrolysis of inorganic-organic hybrid VO_x/3-phenylpropylamine nanobelts under Ar.The intercalated 3-phenylpropylamine molecules were in situ carbonized into NG layers and sandwiched VO_x layers were converted into 10-20 nm V₂O₃ nanoparticles which were intercalated into the formed NG layers forming lamellar V₂O₃/NG hybrid nanobelts.The V₂O₃ nanoparticles intercalated NG nanobelts possess several advantages.First of all,the small V₂O₃nanoparticles offer a large electrode/electrolyte contact area and short path lengths for Li or Na ions diffusion.Secondly,conductive NG matrix provide favorable electron transport channels thus lowering the charge transfer resistance.Thirdly,the NG layers buffer the strain produced by the volume change of the V₂O₃ nanoparticles during cycling.Consequently,the V₂O₃/NG hybrid nanobelts exhibit excellent properties in lithium-and sodium-ion batteries.According to our investigation,The V₂O₃/NG nanobelts exhibited excellent Li-ion storage properties such as high reversible capacities of 435 mAh g^-11 at 100 mA g^-1 for over 250 cycles and 201 mAh g^-1 at 2000 mA g^-11 for over 500 cycles.Moreover,the V₂O₃/NG nanobelts exhibited a high capacity of 154 mAh g^-1 at 500 mA g^-1 for over 500 cycles for Na-ion storage.Our study suggests a promising electrode design and general strategy to prepare V₂O₃/NG nanobelts and the protocol can be extended to the production of high-performance metal oxides electrode.（2）Li₃VO₄/NC nanobelts were prepared by mixing VO_x/3-phenylpropylamine nanobelts with the lithium salt LiOH and then treated by solid-state lithiation reaction,in which 3-phenylpropylamine molecules were carbonized into NC and VO_x were converted into 10-30nm Li₃VO₄ nanoparticles.The Li₃VO₄/NC nanobelts possess several advantages.First of all,1D nanobelts possess large surface-to-volume ratio,facile strain relaxation,and restricted self-aggregation.Secondly,the small Li₃VO₄ nanoparticles offer a large specific surface area and short path lengths for Li ions diffusion.Thirdly,conductive NC provide favorable electron transport channels and improve the electronic conductivity.Fourthly,NC layers buffer volume change of the V₂O₃ nanoparticles during cycling.As a result,The Li₃VO₄/NC nanobelts presented excellent capability of 301 mAh g^-1 at 500 mA g^-1 after 120 cycles and long cyclic performance(83%capacity retention after 1000 cycles at 2000 mA g^-1)in lithium-ion batteries.