Lithium intercalation in Na1+xV3O8 synthesized by a solution technique

Impact of Electrical Conductivity on the Electrochemical Performances of Layered Structure Lithium Trivanadate (LiV3-x M x O8, M= Zn/Co/Fe/Sn/Ti/Zr/Nb/Mo, x = 0.01-0.1) as Cathode Materials for Energy Storage

Pristine trivanadate (LiV₃O₈) and doped lithium trivanadate (LiV_3-x M _x O₈, M = Zn/Co/Fe/Sn/Ti/Zr/Nb/Mo, x = 0.01/0.05/0.1 M) compounds were prepared by a simple reflux method in the presence of the polymer, Pluronic P123, as the chelating agent. For comparison, pristine LiV₃O₈ alone was also prepared in the absence of the chelating agent. The Rietveld-refined X-ray diffraction patterns shows all compounds to exist in the layered monoclinic LiV₃O₈ phase belonging to the space group of P2₁/m. Scanning electron microscopy analysis shows the particles to exhibit layers of submicron-sized particles. The electrochemical performances of the coin cells were compared at a current density of 30 mA/g in the voltage window of 2-4 V. The cells made with compounds LiV_2.99Zr_0.01O₈ and LiV_2.95Sn_0.05O₈ show a high discharge capacity of 245 ± 5 mA h/g, with an excellent stability of 98% at the end of the 50th cycle. The second cycle discharge capacity of 398 mA h/g was obtained for the compound LiV_2.99Fe_0.01O₈, and its capacity retention was found to be 58% after 50 cycles. The electrochemical performances of the cells were correlated with the electrical properties and the changes in the structural parameters of the compounds.

Synthesis of Na(1.25)V(3)O(8) nanobelts with excellent long-term stability for rechargeable lithium-ion batteries

Sodium vanadium oxide (Na1.25V3O8) nanobelts have been successfully prepared by a facile sol-gel route with subsequent calcination. The morphologies and the crystallinity of the as-prepared Na1.25V3O8 nanobelts can be easily controlled by the calcination temperatures. As cathode materials for lithium ion batteries, the Na1.25V3O8 nanobelts synthesized at 400 °C exhibit a relatively high specific discharge capacity of 225 mA h g(-1) and excellent stability at 100 mA g(-1). The nanobelt-structured electrode can retain 94% of the initial capacity even after 450 cycles at the current density of 200 mA g(-1). The good electrochemical performance is attributed to their nanosized thickness and good crystallinity. The superior electrochemical performance demonstrates the Na1.25V3O8 nanobelts are promising cathode materials for secondary lithium batteries.

Dehydration and Lithium Insertion Studies in Phyllomanganates

Layered oxides AxMnO≈2,yH20 (A = Na, K, NH4, Cs or Mn2+) have been dehydrated and intercalated by lithium. Dehydration is accompanied by a shrinking of the interlayer space height depending on the size of A. The valence of Mn is reduced to +2 by reaction with n-butyllithium. Electrochemical studies of cells AxMnO≈2-graphite | LiClO4-PC|I Li showed two main reaction peaks at ca. 3V and below 2 V. The first reaction is a reversible reduction to a disordered Mn3+ phased. Capacities at the third cycle are ca. 300 Wh/kg. No marked difference was found as a function of A or of the degree of order of the starting compound.