No abstract

Nanocrystalline Li3V2(PO4)3 has been prepared by the oxalic dihydrazide assisted combustion (ODHAC) method, and the corresponding Li3V2(PO4)3/C composites containing different concentrations of super P carbon, viz. 10, 20 and 30 wt% have been explored individually as anodes for lithium batteries.

A first attempt has been made to prepare Li 3 M x V 22x (PO 4 ) 3 /C (M=Fe, Co) composite solutions by adopting a novel oxalic dihyrazide assisted combustion (ODHAC) method. The pillaring effect of Fe in Li 3 Fe x V 22x (PO 4 ) 3 /C and the possible electrochemical activity of the Co 3+/4+ redox couple of Li 3 Co x V 22x (PO 4 ) 3 /C at a 4.8 V limit increases the structural and cycling stability of the native Li 3 V 2 (PO 4 ) 3 /C cathode respectively, thereby ultimately improving the electrochemical behaviour of Li 3 M x V 22x (PO 4 ) 3 /C solid solutions. An extended solubility limit of x = 0.10 for Fe dopant has been achieved for the first time through the present study against the reported value of x = 0.05 in Li 3 Fe x V 22x (PO 4 ) 3 /C compounds. The study demonstrates the suitability of the ODHAC synthesis approach in preparing a wide variety of phase pure Li 3 M x V 22x (PO 4 ) 3 /C cathodes. Further, the superiority of Li 3 Co 0.10 V 1.90 (PO 4 ) 3 /C in exhibiting the highest capacity (178 mAh g 21) and negligible fade (4%) and the demonstrated cyclability under the influence of 10 C rate has been understood as a function of the synergistic effect of the ODHAC synthesis method and the optimum concentration of Co dopant chosen for the study.

A novel oxalic dihydrazide (ODH) has been identified as a fuel for solution combustion synthesis to prepare LixMy(PO4)z compounds as a cathode material for lithium battery applications. These compounds have been synthesized at 850°C using a mixture of Ar:H2 (90:10) atmosphere, wherein oxalic dihydrazide acts both as a combustible fuel and a carbon source. This resulted in a higher carbon content weighing ca. 12 and 8% for poly (Li3V2(PO4)3/C) and pyrophosphate (LiVP2O7/C) composites as opposed to the in-situ added super P carbon was only 5 wt.%. The electrochemical behavior of these cathodes showed reversible intercalation and de-intercalation of lithium ions while exhibiting specific capacities of 168 and 100 mAh/g with good capacity retention. The role of ODH assisted combustion synthesis (ODHAC) on the physical and electrochemical behavior of the title compounds has been demonstrated.