Optical properties in Mn-doped ZnS thin films: Photoluminescence quenching

Inamdar, A.I.,Cho, S.,Jo, Y.,Kim, J.,Han, J.,Pawar, S.M.,Woo, H.,Kalubarme, R.S.,Park, C.,Kim, H.,Im, H. North-Holland 2016 Materials letters Vol.163 No.-

Mn-doped ZnS thin films are synthesized on soda-lime glass substrates using magnetron co-sputtering technique. X-ray diffraction and atomic force microscopy measurements indicate that of the as-obtained films including the highest Mn (~11% relative to the Zn concentration) in the lattice of ZnS are amorphous with a granular morphology. X-ray photoelectron spectroscopy reveals the presence of Zn<SUP>2+</SUP>, Mn<SUP>2+</SUP> and S<SUP>2-</SUP> chemical states in the films. The undoped ZnS film exhibits photoluminescence (PL) peaks at energies around 3.26eV (wavelength ~379nm) and 2.95eV (~420nm), which originate from the interplay between excited electron, defect (sulfur vacancy) states and the valence band. For the Mn-doped ZnS films, the band-to-band emission peak is quenched and shifts toward to higher energies at a rate of 11.7+/-2meV/Mn%. We propose that Mn dopant-mediated structural phases and non-radiative deep traps in ZnS cause the modification in the optical transition.

Investigations on silver/polyaniline electrodes for electrochemical supercapacitors

Patil, Dipali S.,Shaikh, J. S.,Pawar, S. A.,Devan, R. S.,Ma, Y. R.,Moholkar, A. V.,Kim, J. H.,Kalubarme, R. S.,Park, C. J.,Patil, P. S. The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.34

<P>Polyaniline (PANI) and silver doped polyaniline (Ag/PANI) thin films were deposited on stainless steel substrates by a dip coating technique. To study the effect of doping concentration of Ag on the specific capacitance of PANI the concentration of Ag was varied from 0.3 to 1.2 weight percent. Fourier transform-infrared and Fourier transform-Raman spectroscopy, and energy dispersion X-ray techniques were used for the phase identification and determination of the doping content in the PANI films, respectively. The surface morphology of the films was examined by Field Emission Scanning Electron Microscopy, which revealed a nanofiber like structure for PANI and nanofibers with bright spots of Ag particles for the Ag/PANI films. There was decrease in the room temperature electrical resistivity of the Ag/PANI films of the order of 10<SUP>2</SUP> with increasing Ag concentration. The supercapacitive behavior of the electrodes was tested in a three electrode system using 1.0 M H<SUB>2</SUB>SO<SUB>4</SUB> electrolyte. The specific capacitance increased from 285 F g<SUP>−1</SUP> (for PANI) to 512 F g<SUP>−1</SUP> for Ag/PANI at 0.9 weight percent doping of Ag, owing to the synergic effect of PANI and silver nanoparticles. This work demonstrates a simple strategy of improving the specific capacitance of polymer electrodes and may also be easily adopted for other dopants.</P> <P>Graphic Abstract</P><P>The presence of Ag nanoparticles on PANI nanofibers provides a least resistance path to electron transportation. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41757j'> </P>

Nickel-titanium oxide as a novel anode material for rechargeable sodium-ion batteries

Kalubarme, R.,Inamdar, A.,Bhange, D. S.,Im, H.,Gosavi, S.,Park, C. J. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.44

<P>Nickel-titanium oxide (NiTiO3; NTO) of an ilmenite structure that comprises a layered transition-metal octahedral structure, wherein the zigzag open tunnels are possible routes for Na intercalation, can be a potential anode material for sodium (Na) ion batteries (SIBs). In this study, nanocrystalline NTO particles that are of sizes 3 to 5 nm were prepared using a simple hydrothermal process followed by annealing, and the particles were then tested for SIB applications. The pure-NTO electrode that comprises a hexagonal crystal structure and mesoporous morphology demonstrated a reversible capacity of approximately 521 mA h g(-1) that corresponds to a coulombic efficiency of 67% in the first cycle, which further improved to similar to 98% in the following cycles, at an applied specific current of 50 mA g(-1), and stable cycling performance for 200 cycles. Further, due to the synergetic effect of the porous network structure and high surface area, the NTO electrode exhibited an exceptional rate capability, delivering a capacity of 192 mA h g(-1) at a high specific current of 4000 mA g(-1). The excellent cyclability and rate capability of the NTO electrode are attributed to the improved electronic conductivity and highly porous microstructure of the NTO material, whereby fast charge transfer and facile diffusion of the Na-ions to the active sites are enabled.</P>

Nickel titanate lithium-ion battery anodes with high reversible capacity and high-rate long-cycle life performance

Inamdar, A.,Kalubarme, R.,Kim, J.,Jo, Y.,Woo, H.,Cho, S.,Pawar, S. M.,Park, C. J.,Lee, Y. W.,Sohn, J. Royal Society of Chemistry 2016 Journal of materials chemistry. A, Materials for e Vol.4 No.13

<P>We demonstrate the impressive performance of sparsely studied nickel titanate anode materials for Li-ion batteries (LIBs). The nickel titanate anode delivers a high reversible discharge capacity of 435 mA h g(-1) at a current density of 35 mA g(-1), high-rate performance and excellent cycling retention of 96% with a long-term cycling stability at 1500 mA g(-1) over 300 cycles. The coulombic efficiency is obtained as high as 98%. This superior nickel titanate electrode material could be used as a safe, low-cost, long cycle life anode material for next-generation LIBs with a high power capability.</P>

Highly stable bilayer of LiPON and B₂O₃ added Li_1.5Al_0.5Ge_1.5(PO₄) solid electrolytes for non-aqueous rechargeable Li-O₂ batteries

Jadhav, H.S.,Kalubarme, R.S.,Jadhav, A.H.,Seo, J.G. Pergamon Press 2016 ELECTROCHIMICA ACTA Vol.199 No.-

Lithium ion conducting membranes are barely studied, although they are essentially indispensable for building Li-air batteries composed of aqueous and non-aqueous electrolytes for long-term operation. Lithium phosphorous oxynitride (LiPON) thin films were deposited by RF-sputtering technique on B<SUB>2</SUB>O<SUB>3</SUB>-added lithium aluminum germanium phosphate (B-LAGP). Compact thin amorphous LiPON layer could act as a protective interlayer for B-LAGP by separating it from Li metal electrode and mitigate the reaction between them. Large electrochemical stability window (0-5V) of LiPON/B-LAGP solid electrolyte shows promising feasibility for applications in all lithium based batteries. The aprotic Li-O<SUB>2</SUB> cell with protected lithium electrode configuration employing LiPON/B-LAGP solid electrolyte has exhibited reasonable cycling stability with long-life of 52 cycles at a limited capacity of 1000mAhg<SUP>-1</SUP>.

Mechanism for the Degradation of MmNi_3.9Co_0.6Mn_0.3Al_0.2 Electrode and Effects of Additives on Electrode Degradation for Ni-MH Secondary Batteries

In-Su Jang,R. S. Kalubarme,Dong-Cheol Yang,Tae-Sin Kim,Choong-Nyeon Park,류현욱,Chan-Jin Park 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.6

Electrode degradation can affect the lifetime and safety of Ni-MH secondary batteries. This study examined the factors responsible for the degradation of metal hydride (MH) electrodes. The charge-discharge characteristics and cycle life of an MmNi_3.9Co_0.6Mn_0.3Al_0.2 (Mm: misch metal) type MH electrode were examined in a cell with a KOH electrolyte. After the charge-discharge cycles, the surface morphology of the electrodes was analyzed to monitor the extent of degradation. Electrochemical impedance spectroscopy provided information on the conductivity of the electrode. X-ray photon spectroscopy (XPS) was used to quantify the degradation of the electrode in terms of its composition. The MH electrodes degraded with cycling. This phenomenon was more prominent at higher C-rates and temperatures. The electrode degradation was attributed to the loss of active material from the current collector by the repeated absorption and desorption of hydrogen and the formation of an Al_2O_3 oxide layer on the electrode surface with cycling. In addition, the effects of the addition of Co nano and Y_2O_3 powder on the degradation of the MmNi_3.9Co_0.6Mn_0.3Al_0.2 electrode were examined. The addition of the Y_2O_3 and Co nano powder significantly improved the performance of the MH electrode by increasing the cycle life and initial activation rate.

Effect of Alloying Elements on the Electrochemical Characteristics of an Al Alloy Electrode for Al-air Batteries in 4M NaOH solution

( Yun Il Choi ),( R. S. Kalubarme ),( Hee Jin Jang ),( Chan Jin Park ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.11

We examined the effects of alloying elements such as Fe, Ga, In, Sn, Mg, and Mn on the electrochemical characteristics of Al-based alloys for Al-air batteries by potentiodynamic polarization tests and electrochemical impedance spectroscopy. The corrosion potential of an Al anode was lowered by the addition of Ga and Sn, resulting in an increase in the cell voltage compared with a pure Al electrode. Fe was not beneficial to improve the electrochemical properties of the Al anode in that it caused a decrease in the cell voltage and reduced corrosion rate slightly. In, Mn, Sn, and Mg decreased the corrosion rate of the Al alloys, while Ga enhanced corrosion significantly and accelerated consumption of the anode.

Supercapacitive Characteristics of Electrodeposited Polyaniline Thin Films Grown on Indium-doped Tin-oxide Substrates

A. I. Inamdar,임현식,김영삼,손재상,김형상,R. S. Kalubarme,박찬진,김대영 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1

Polyaniline (PANI) thin films were successfully synthesized using the electrodeposition (ED) technique from a mixed solution of 0.2M aniline and 0.2M H2SO4. PANI films with thicknesses of 220 and 250 nm were synthesized. The formation of compact and amorphous PANI films was confirmed with scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The electrochemical supercapacitor properties of the PANI films were examined using cyclic voltammetry and galvanostatic charge-discharge measurements. A specific capacitance of ∼473 Fg^(−1) at 1 mAcm^(−2) in a 0.5 M H_2SO_4 electrolyte was obtained for the PANI electrodes. The electrochemical stability of the PANI electrodes was investigated using cyclic voltammetry and charge-discharge measurements. Both the films were quite stable with 16% capacitance loss after a few initial charge-discharge cycles.

Synthesis and enhanced electrochemical supercapacitive properties of manganese oxide nanoflake electrodes

Inamdar, A.I.,Jo, Y.,Kim, J.,Han, J.,Pawar, S.M.,Kalubarme, R.S.,Park, C.J.,Hong, J.P.,Park, Y.S.,Jung, W.,Kim, H.,Im, Hyunsik Elsevier 2015 ENERGY Vol.83 No.-

<P><B>Abstract</B></P> <P>MnO<SUB>2+δ</SUB> (Manganese oxide) nanoflakes were synthesized for use as electrode material in electrochemical supercapacitors. The nanoflakes were produced via RF-magnetron sputtering with various excess oxygen contents (δ), and the electrochemical supercapacitive properties of the MnO<SUB>2+δ</SUB> nanoflakes were investigated as a function of δ with the use of a Na<SUB>2</SUB>SO<SUB>4</SUB> electrolyte. The excess oxygen (δ) induces the MnO<SUB>2+δ</SUB> nanoflakes to form a thin open structure, and μ-Raman measurements revealed that the MnO<SUB>2+δ</SUB> nanoflakes formed a birnessite phase with a layered structure. X-ray photoelectron spectroscopy was used to obtain quantitative information on both the oxidation state and the chemical composition of the nanoflake electrodes. The crystallinity of the nanoflakes improved when the oxygen partial pressure increased during sputtering. At an optimal δ ∼ 0.6, the electrochemical stability and the capacity retention significantly improved, and electrochemical impedance spectroscopy revealed that easy access of Na<SUP>+</SUP> ions into the nanoflakes at an optimal δ value resulted in a low diffusion resistance, playing a key role in determining the improvement in the supercapacitor characteristics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MnO<SUB>2+δ</SUB> nanoflakes are grown using RF-magnetron sputtering. </LI> <LI> Excess oxygen (δ) endorses the formation of a porous and open structure. </LI> <LI> At δ ∼ 0.6, the stability and capacity retention are significantly improved. </LI> <LI> Low diffusion resistance plays a key role in determining supercapacitor characteristics. </LI> </UL> </P>