pavan srinivas | IIT Bombay (original) (raw)

Papers by pavan srinivas

Journal of Power Sources, 2015

ABSTRACT A two step approach for synthesis of porous α-Fe2O3 nanostructures has been realized via... more ABSTRACT A two step approach for synthesis of porous α-Fe2O3 nanostructures has been realized via polyol method by complexing iron oxalate with ethylene glycol. Crystalline Fe2O3 samples with different porosities are obtained by calcination of Fe-Ethylene glycol complex at various temperatures. The as-prepared porous Fe2O3 structures exhibit promising lithium storage performance at high current rates. It is observed that the calcination temperature and the resultant porosity have a significant effect on capacity and cycling stability. Samples calcined at high temperature (600 °C) demonstrates stable cycle life with capacity retention of 1077 mAh g−1 at 500 mA g−1 current rate after 50 charge-discharge cycles. Samples calcined at temperatures of 500 and 600 °C display stable cycle life and high rate capability with reversible capacity of 930 mAh g−1 and 688 mAh g−1 at 5 A g−1, respectively. Impregnation of electrodes with electrolyte before cell fabrication shows enhanced electrochemical performance. The viability of Fe2O3 porous nanostructures as prospective anode material examined against commercial LiFePO4 cathode shows promising electrochemical performance.

Central European Journal of Biology, 2013

In the current study, haloarchaea Halobacterium salinarum cells were transformed individually wit... more In the current study, haloarchaea Halobacterium salinarum cells were transformed individually with each of the modified archaellin genes (flaA1, flaA2 and flaB2) containing an oligonucleotide insert encoding the FLAG peptide (DYKDDDDK). The insertion site was selected to expose the FLAG peptide on the archaella filament surface. Three types of transformed cells synthesizing archaella, containing A1, A2, or B2 archaellin modified with FLAG peptide were obtained. Electron microscopy of archaella has demonstrated that in each case the FLAG peptide is available for the specific antibody binding. It was shown for the first time that the B2 archaellin, like archaellins A1 and A2, is found along the whole filament length.

ChemElectroChem, 2014

ABSTRACT We introduce a process of making high-capacity and rate-capable metal-ferrite-based conv... more ABSTRACT We introduce a process of making high-capacity and rate-capable metal-ferrite-based conversion anodes for lithium-ion batteries. Cobalt ferrite (CoFe2O4) exhibits a discharge capacity that is two-times higher compared to the state-of-the-art graphite anode, but at the same time it shows high volume change (ca. 95 %) during conversion reaction with lithium in an electrochemical environment. This large volume expansion is responsible for the particle–particle and conductive-carbon particles–active materials detachment, which leads to cyclic instability during subsequent cycles. As observed in our earlier work, any kind of weak or strong chemical interaction between active materials and binder is necessary to achieve excellent electrochemical performance in case of conversion or alloying reactions. To compare the electrochemical activity of CoFe2O4 nanoparticles against lithium, we use conventional polyvinylidene fluoride and sodium alginate binder to fabricate electrodes. Fourier-transform infrared measurements reveal weak hydrogen-bond formation between surface OH groups of CoFe2O4 and COOH groups of the alginate binder. Indentation tests further confirm the increased hardness of the alginate/CoFe2O4-based electrode films. CoFe2O4–alginate–carbon anode exhibits a high specific capacity of 890 mAh g−1 at 0.1 C rate (91.4 mA g−1) after 50 charge–discharge cycles. Even at high rate cycling with current densities such as 18280 mA g−1 (20 C), the same electrode material exhibits a specific capacity of 470 mAh g−1, which is much higher than that of conventional graphite anode at the same electrochemical conditions.

RSC Advances, 2013

Enhanced high rate performance of a-Fe 2 O 3 nanotubes with alginate binder as a conversion anode3

Electrochimica Acta, 2014

ABSTRACT Rich electrochemistry of vanadium based compounds in terms of high lithium storage capab... more ABSTRACT Rich electrochemistry of vanadium based compounds in terms of high lithium storage capability along with low cost prompted us to study NH 4 V 4 O 10 as cathode material for lithium ion batteries. Herein, we report for the first time, a high rate and high energy density cathode based on intercalated ammo-nium vanadate. The present strategy of making such high rate cathode is mainly based on the use of interactive binder like carboxy methyl cellulose (CMC) or alginate binder instead of poly(vinylidene difluride) (PVDF) binder along with 2D morphology. A detailed study shows the dependency of morphology , reaction pH and binder selection on electrochemical performance. In brief, we have demonstrated NH 4 V 4 O 10-CMC/alginate based cathode as superior candidate for next generation lithium-ion batteries. The as synthesized NH 4 V 4 O 10 along with CMC/alginate binder delivers discharge capacity of 200 mAh g −1 at very high current rate of 1000 mA g −1 and completely retains its original discharge state at low current rate of 100 mA g −1 rate, whereas PVDF-based cathode delivers discharge capacity of 125 mAh g −1 at same current rate. Based on morphological and FT-IR studies, we have revealed interactions between active materials and binder particles (CMC and alginate) which play a crucial role in determining the electrochemical performance.

Scientific Reports, Jan 13, 2015

Designing a new generation of energy-intensive and sustainable electrode materials for batteries ... more Designing a new generation of energy-intensive and sustainable electrode materials for batteries to power a variety of applications is an imperative task. The use of biomaterials as a nanosized structural template for these materials has the potential to produce hitherto unachievable structures. In this report, we have used genetically modified flagellar filaments of the extremely halophilic archaea species Halobacterium salinarum to synthesize nanostructured iron oxide composites for use as a lithium-ion battery anode. The electrode demonstrated a superior electrochemical performance compared to existing literature results, with good capacity retention of 1032 mAh g 21 after 50 cycles and with high rate capability, delivering 770 mAh g 21 at 5 A g 21 (,5 C) discharge rate. This unique flagellar filament based template has the potential to provide access to other highly structured advanced energy materials in the future. B reakthroughs in high energy and power density lithium battery technology are strongly reliant on the development of new nanostructured electrode materials 1,2. A new and promising trend in the creation of such materials is the use of bio-polymers for the directional assembly of inorganic components into structures of greater hierarchical complexity 3,4. This approach was first demonstrated by Belcher and co-workers to create lithium-ion battery electrode materials based on a genetically modified, filamentous M13 virus as a biotemplate 5-7. In the present work, we demonstrate the use of flagella as promising, and much more easily handled, bio-templates for materials synthesis. The standard capacity of a graphite anode in commercial batteries is only 250-300 mAh g 21 with the theoretical limit of 372 mAh g 21 8. Moreover, the rate performance of graphite is still well below the levels demanded for high power lithium ion batteries in advanced applications such as electric vehicles. Oxides of transition metals (such as Co, Fe, Ni, Cu, etc.) have attracted great attention in this regard because of their potential to deliver high theoretical specific capacity 9. Among the metal oxides, iron oxide (Fe 2 O 3) is one of the most promising materials because of its high theoretical specific capacity (1007 mAh g 21), abundance, low cost and environmental acceptability 1,9,10. At present, the fabrication and performance (in terms of cycle stability) of Fe 2 O 3 based anodes still remains a great challenge 10. It is known that under discharge/charge cycling Fe 2 O 3 based electrode materials degrade and their capacity fades quickly 11. In addition, the active surface area of such materials reduces because of agglomeration 12,13. One of the ways to overcome these imperfections is to fabricate hybrid nanostructures, where Fe 2 O 3 is embedded into a conductive matrix or covered with coating layers via intermolecular interactions or to synthesize nanostructured Fe 2 O 3 or nanoparticles, nanowires etc. 13-18. Viruses and other biological structures that can function as scaffolds can stabilize such nanosized metal oxide particles and prevent their agglomeration 5,6. Bacterial and archaeal flagella are structures that have attractive properties for this use 19-23. These are extracellular protein filaments used by unicells as motility organelles. The Archaea constitute a domain of microorganisms mostly composed of cells that live in extreme environments. Many archaeal biopolymers, including flagella, are able to preserve their structural integrity in a wide range of external conditions. As such they may be promising candidates as synthetic templates in nanobiotechnology 24. Archaeal flagella are typically long (,10 mm) filaments with thickness of 10-15 nm 25. Being totally protein-based structures, they offer a number of benefits over DNA-containing viruses in nano-technology applications. Halophilic archaea are safe to humans and quite un-demanding in terms of growth environment (advanta

Interactive binders are of current interest to the lithium-ion battery community because they are... more Interactive binders are of current interest to the lithium-ion battery community because they are beneficial for alloy-based anodes. They can accommodate the extra stress generated during the reaction with lithium well and alleviate the pulverization problem associated with the alloying-dealloying process. One of the best examples of an interactive binder is sodium alginate, which has recently being used in silicon-based anodes. The silicon-alginate binder combination has exhibited excellent electrochemical reactivity and stability. Herein, we have utilized the interactive properties of the alginate binder along with the hollow nanostructural features of a-Fe 2 O 3 nanotubes in order to achieve an excellent conversion-based anode for lithium-ion batteries. In this regard, a-Fe 2 O 3 is synthesized using a simple hydrothermal method and the hollow nanostructured a-Fe 2 O 3 nanotubes have shown a stable high capacities of about 800 mAh g 21 at 503 mA g 21 for 50 cycles with alginate binder. Even at a high current rate of 1007 mA g 21 (y1C), high capacity of 732 mAh g 21 and 600 mAh g 21 has been achieved after 50 and 100 cycles respectively. The same electrode assembly has shown an excellent high rate capability and delivered a capacity of 400 mAh g 21 even at a very high current density of 10 A g 21 . In this report we propose that weak hydrogen bonding between the surface hydroxyl groups on the metal oxide (Fe 2 O 3 ) and the carboxylic functional groups on the alginate binder is responsible for the enhanced battery performance at very high current rates.