N. Munichandraiah

Indian Institute of Science, Bengalore, State of Karnataka, India

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Publications (146)327.48 Total impact

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    ABSTRACT: The partially exfoliated and reduced graphite oxide (PE-RGO) is prepared by low temperature thermal exfoliation of graphite oxide under air atmosphere. A symmetric carbon/carbon supercapacitor is studied in a Na2SO4 aqueous electrolyte. The discharge capacitance is 92 F g−1, when symmetric cell is cycled between the potential ranges from 0 to 1.6 V. This system demonstrates a stable charge/discharge cycle behavior up to 3000 cycles when the cell is operated at a voltage window of 1.6 V. The utilization ratio of potential window is 90% for this system is attributed to the more negative value of electrodes potential when the cell voltage is set to 0 V. The low-temperature exfoliation approach is convenient for mass production of graphenes at low cost and it can be used as electrode material for energy storage applications.
    Solid State Communications 12/2014; · 1.53 Impact Factor
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    ABSTRACT: Pore size distribution (BJH) curves of 0.5Li2MnO3-0.5LiMn0.35Ni0.55Fe0.1O2 samples heated at 500 °C (i), 600 °C (ii), 700 °C (iii), 800 °C (iv) and 900 °C (v).
    Electrochimica Acta 10/2014; 143:152–160. · 4.09 Impact Factor
  • Surender Kumar, Selvaraj C, L G Scanlon, N Munichandraiah
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    ABSTRACT: Silver nanoparticles-anchored reduced graphene oxide (Ag-RGO) is prepared by simultaneous reduction of graphene oxide and Ag+ ions in an aqueous medium by ethylene glycol as the reducing agent. Ag particles of average size of 4.7 nm are uniformly distributed on the RGO sheets. Oxygen reduction reaction (ORR) is studied on Ag-RGO catalyst in both aqueous and non-aqueous electrolytes by using cyclic voltammetry and rotating disk electrode techniques. As the interest in non-aqueous electrolyte is to study the catalytic performance of Ag-RGO for rechargeable Li-O2 cells, these cells are assembled and characterized. Li-O2 cells with Ag-RGO as the oxygen electrode catalyst are subjected to charge-discharge cycling at several current densities. A discharge capacity of 11,950 mAh g-1 (11.29 mAh cm-2) is obtained initially at low a current density. Although there is a decrease in capacity on repeated discharge-charge cycling initially, a stable capacity is observed for about 30 cycles. The results indicate that Ag-RGO is a suitable catalyst for rechargeable Li-O2 cells.
    Physical Chemistry Chemical Physics 08/2014; · 4.20 Impact Factor
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    ABSTRACT: Li-ion battery thin film battery TiN anode electrochemical performance a b s t r a c t TiN thin films with (200) fibre texture are deposited on Cu substrate at room temperature using reactive magnetron sputtering. They exhibit a discharge capacity of 172 ␮Ah cm −2 ␮m −1 (300 mAh g −1) in a non-aqueous electrolyte containing a Li salt. There is a graded decrease in discharge capacity when cycled between 0.01 and 3.0 V. Electron microscopy investigations indicate significant changes in surface morphology of the cycled TiN electrodes in comparison with the as deposited TiN films. From XPS depth profile analysis, it is inferred that Li intercalated TiN films consist of lithium compounds, hydroxyl groups, titanium sub oxides and TiN. Lithium diffusivity and reactivity decrease with increase in depth and the major reaction with lithium takes place at film surface and grain boundaries.
    Electrochimica Acta 05/2014; 125:282-287. · 4.09 Impact Factor
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    Sthitaprajna Dash, N Munichandraiah
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    ABSTRACT: Nanodendritic Pd electrodeposited on poly(3,4-ethylenedioxythiophene) (PEDOT) modified Pd nanodendrite electrodes has been studied for electroanalysis of As(iii) in 1 M HCl solution. The Pd nanodendrites are grown on a porous thin film of PEDOT by electrodeposition process. Pd-PEDOT/C electrodes are characterized by physicochemical and electrochemical studies. Cyclic voltammetry studies show that Pd-PEDOT/C electrodes exhibit greater electrocatalytic activity towards As(iii)/As(0) redox reaction than the Pd/C electrodes. Differential pulse anodic stripping voltammetry (DPASV) is performed for analysis of As(iii) ion at pH 1.0. The Pd-PEDOT/C electrode is highly sensitive towards As(iii) detection with sensitivity of 1482 μA cm(-2) μM(-1). A wide detection range up to 10 μM and low detection limit of 7 nM (0.52 ppb) are obtained with a pre-deposition time of 120 s under optimum conditions. High sensitivity and low detection limit obtained on Pd-PEDOT/C, for the first time in the literature, are attractive from a practical view point. Interference studies of Cu(ii) ions are investigated and it is observed that Cu(ii) ions do not interfere.
    The Analyst 02/2014; · 4.23 Impact Factor
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    ABSTRACT: Detailed analysis of alternating current impedance data of LiMn2O4 electrodes measured at several temperatures and potentials was carried out. The Nyquist plots generally consisted of semicircles corresponding to two time constants. However, at low temperatures (−10 to 10 °C) and potential region between 3.90 and 4.20 V, three time constants were present. The third semicircle present at the middle to high frequency range was attributed to electronic resistance of LiMn2O4. Impedance parameters were evaluated using appropriate electrical equivalent circuits. From the temperature dependence of resistive parameters, activation energy values for the corresponding processes were calculated.
    Journal of Applied Electrochemistry 01/2014; 44(1). · 1.84 Impact Factor
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    S. Shivakumara, Tirupathi Rao Penki, N. Munichandraiah
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    ABSTRACT: Porous α-Fe2O3 nanostructures have been synthesized by a simple sol–gel route. The α-Fe2O3 nanostructures are poorly crystalline and porous with BET surface area of 386 m2 g−1. The high discharge capacitance of α-Fe2O3 electrodes is 300 F g−1 when the electrodes are cycled in 0.5 M Na2SO3 at a current density of 1 A g−1. The capacitance retention after 1000 cycles is about 73% of the initial capacitance at a current density of 2 A g−1. The high discharge capacitance of α-Fe2O3 in comparison with the literature reports are attributed to high surface area and porosity of the iron oxide prepared in the present study. As the iron oxides are inexpensive, the capacity of α-Fe2O3 is expected to be of potential use for supercapacitor application.
    Materials Letters 01/2014; 131:100–103. · 2.27 Impact Factor
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    S Shivakumara, Tirupathi, Rao Penki, N Munichandraiah
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    ABSTRACT: Porous α-Fe 2 O 3 nanostructures have been syn-thesized by sol–gel route. The effect of preparation temperature on the morphology, structure, and electro-chemical stability upon cycling has been studied for supercapacitor application. The discharge capacitance of α-Fe 2 O 3 prepared at 300 °C is 193 F g −1 , when the electrodes are cycled in 0.5 M Na 2 SO 3 at a specific current of 1 A g −1 . The capacitance retention after 1,000 cycles is about 92 % of the initial capacitance at a current density of 2 A g −1 . The high discharge capacitance as well as stability of α-Fe 2 O 3 electrodes is attributed to large surface area and porosity of the material. There is a decrease in specific capacitance (SC) on increasing the preparation temperature. As iron oxides are inexpensive, the synthetic route adopted for α-Fe 2 O 3 in the present study is convenient and the SC is high with good cycling stability, the porous α-Fe 2 O 3 is a potential material for supercapacitors.
    Journal of Solid State Electrochemistry 12/2013; · 2.28 Impact Factor
  • P. Ragupathy, H. N. Vasan, N. Munichandraiah
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    ABSTRACT: Polygon shaped nanoparticles of molybdenum dioxide (MoO2) have been synthesized by reducing commercial molybdenum trioxide (MoO3) with ethylene glycol (EG) under N2 atmosphere at 400 °C. The synthesized products have been characterized using various techniques such as powder XRD pattern, thermal analysis (TGA/DTA) and infrared (IR) spectroscopy. XRD data confirms the formation MoO2 monoclinic phase with space group P21/c. The morphological studies have been investigated by employing SEM and TEM techniques. MoO2 facilitates reversible insertion/extraction of Li+ ions between 0.25 to 3.0 V versus Li/Li+. Cyclic voltammetry (CV) and galvanostatic charge-discharge cycling have been conducted on this anode material.
    Journal of Nano Energy and Power Research. 12/2013; 2(2).
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    ABSTRACT: A porous layered composite of Li 2 MnO 3 and LiMn 1/3 Co 1/3 Ni 1/3 O 2 (composition: Li 1.2 Mn 0.53 Ni 0.13 Co 0.13 O 2) is prepared by reverse microemulsion method employing a soft polymer template and studied as a positive electrode material. The precursor is heated at several temperatures between 500 and 900 • C. The product samples possess mesoporosity with broadly distributed pores of about 30 nm diameters. There is a decrease in pore volume as well as in surface area by increasing the temperature of preparation. Nevertheless, the electrochemical activity of the composite increases with an increase in temperature. The discharge capacity values of the samples prepared at 800 and 900 • C are about 250 mAh g −1 at a specific current of 40 mA g −1 with an excellent cycling stability. A value of 225 mAh g −1 is obtained at the end of 30 charge-discharge cycles. Both these composite samples possess high rate capability, but the 800 • C sample is marginally superior to the 900 • C sample. A discharge capacity of 100 mAh g −1 is obtained at a specific current of 1000 mA g −1 . The high rate capability is attributed to porous nature of the composite samples. At present, LiCoO 2 , LiMn 2 O 4 and LiFePO 4 either in their pure states or with partial substitutions of the transition metals, are em-ployed as the positive electrode materials in Li-ion batteries. 1,2 The practical discharge capacity values of LiCoO 2 , LiMn 2 O 4 and LiFePO 4 are 140, 130 and 170 mAh g −1 , respectively at low rates (C/10 or lower rates). 3 Li-ion batteries with greater energy density than the present batteries need the positive electrode materials of greater discharge capacity. Compounds with a high atomic ratio of extractable lithium to transition metal are expected to provide high discharge capacity values. Li 2 MnO 3 with a theoretical capacity of 456 mAh g −1 belongs to this category of materials. 4 Li 2 MnO 3 is a layered compound and can also be represented as Li(Li 0.33 Mn 0.67)O 2, which is similar to the layered LiCoO 2 . One third of the octahedral sites meant for Mn in the crystal lattice are occupied by Li atoms. However, Li 2 MnO 3 is not electrochemically active because of the oxidation state of Mn is +4 and it cannot increase to +5 when Li is extracted from the structure. Nevertheless, several publications have appeared with dif-ferent procedures for activation of Li 2 MnO 3 and with varying capacity values. 5–14 The initial discharge capacity values are generally high for the activated phases of Li 2 MnO 3 , but cycling instability is observed in all reports. In order to enhance the cycling stability, composites of Li 2 MnO 3 with other layered lithiated transition metal oxides such as LiCoO 2 are studied. 15–19 Namata et al., 15 intended to substitute Co in LiCoO 2 by Mn and Li together (1 Co by 0.67 Mn + 0.33 Li) in a wide range of compositions. When cycled between 3.00 and 4.30 V, there was a decrease in discharge capacity with an increase in con-centration of Mn and Li substituted for Co. Pure phase of LiCoO 2 provided the highest capacity among several compositions studied. 15 Composites of Li 2 MnO 3 and LiMn 0.5 Ni 0.5 O 2 were studied by Thack-eray group. 16 It was reported that the cations in the transition metal layers were distributed in an irregular manner in domains with short range order. 16 Electrochemical activity was induced in Li 2 MnO 3 com-ponent of the composite by a loss of Li 2 O. A composite of Li 2 MnO 3 and a layered oxide consisting of Mn, Ni and Co was also stud-ied by Thackeray group. 17 On cycling between 2.00 and 4.60 V, a steady capacity of about 180 mAh g −1 was obtained. Electrochemical characterization of Li 2 MnO 3 -Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 -LiNiO 2 compos-ite was reported by Lim et al. 18 A discharge capacity of about 250 mAh g −1 at a specific current of 20 mA g −1 was obtained. Synthesis of Li 2 MnO 3 .LiMn 1/3 Ni
    Journal of The Electrochemical Society 10/2013; 161:33-39. · 2.86 Impact Factor
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    ABSTRACT: Lithium manganese oxide (Li 2-x MnO 3-y) thin films have been deposited from activated Li 2 MnO 3 powder by radio frequency magnetron sputtering for the first time in the literature and subjected to electrochemical characterization. Physicochemical charac-terization by X-ray diffraction has revealed the formation of the thin films with crystallographic phase identical to that of the powder target made of Li 2-x MnO 3-y . The Li:Mn atomic ratio for the powder and film are calculated by X-ray photoelectron spectroscopy and it is found to be 1.6:1.0. From galvanostatic charge discharge studies, a specific discharge capacity of 139 μAh μm −1 cm −2 was obtained when cycled between 2.00 and 3.50 V vs Li / Li + . Additionally the rate capability of the thin film electrodes was studied by subjecting the cells to charge-discharge cycling at different current densities in the range from 10 μA cm −2 to 100 μA cm −2 . The search for high performance thin film electrodes and elec-trolytes for all solid state thin film batteries (TFB) has attracted at-tention in recent years. The inherent benefits of thin films together with safety and design flexibility have accelerated their applications in micro energy storage for potable electronics. 1,2 The binder-free thin film electrodes offer an additional advantage of studying pure active materials excluding conductive additives when compared to its bulk counter parts. Several groups have reported 3–8 on cobalt based thin films as cathodes for TFBs with good discharge capacity in the range of 60–80 μAh μm −1 cm −2 . But toxic nature and high cost of cobalt limit their use toward commercialization. Manganese based thin films are more attractive alternatives because of their low cost and en-vironmental friendliness. LiMn 2 O 4 thin film cathodes were studied by pulsed laser deposition (PLD), 9–11 sol-gel, 12,13 spin coating 14,15 and sputtering. 16–20 Recently another Mn based layered compound, Li 2 MnO 3 has invoked greater attention among the research commu-nity because of its high theoretical capacity. 21–26 But Li 2 MnO 3 is electrochemically inactive since Mn cannot be further oxidized from its present oxidation state of +4 when Li + ion is extracted from it. Nevertheless, Li 2 MnO 3 can be converted to electrochemically active form by acid treatment and discharge capacity values in the range 200–250 mAh g −1 are reported. 21–26 Acid treated Li 2 MnO 3 powder was studied in the potential range 2.00–4.40 V vs Li/Li + for electro-chemical activity and discharge capacity values of 240 mAh g −1 at C/10 rate and 130 mAh g −1 at 10 C rate were reported. 26 To the best of authors' knowledge, there are no studies reported on thin films of activated Li 2 MnO 3. In the present study, acid treated Li 2 MnO 3 pow-der was used as a target to deposit thin films of Li 2-x MnO 3-y by radio frequency (rf) magnetron reactive sputtering for the first time in the literature. A high discharge capacity with an excellent cycling stabil-ity of Li 2-x MnO 3-y films is obtained. Thus, the thin films are expected to be useful for high capacity thin film batteries.
    Journal of The Electrochemical Society 10/2013; 161(1):28-32. · 2.86 Impact Factor
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    ABSTRACT: Carbon has been prepared by pyrolysis of grated, milk-extracted coconut kernel at 600 º C under nitrogen atmosphere. The disordered carbon has sheet like morphology. The carbon exhibits a high reversible Li + intercalation capacity in a non-aqueous electrolyte. The initial charge and discharge capacities are 990 and 400 mAh g -1 , thus resulting in an irreversible capacity loss of 590 mAh g -1 . Nevertheless, subsequent discharge capacity is stable over a large number of charge-discharge cycles. The electrodes withstand charge-discharge currents as high as 1257 mA g -1 and they deliver discharge capacity of 80 mAh g -1 . Diffusion coefficient of Li + obtained from galvanostatic intermittent titration is 6.7 x 10 -12 cm 2 s -1 . Thus the coconut kernel derived carbon is a suitable anode material for Li-ion batteries. Copyright © 2014 VBRI press.. At present he is pursuing his doctoral degree at Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore under the supervision of Prof N. Munichandraiah in the field of nanostructure materials for Li-ion battery.. His field of interest is materials for Li-ion batteries, thin film batteries and supercapacitors. N. Munichandraiah obtained his M.Sc. degree from Sri Venkateswara University, Tirupati and Ph.D. degree from Indian Institute of Science, Bangalore. He is presently Professor in the Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore. His research of interests is mainly Li-ion and Li-air batteries, supercapacitors, conducting polymers, electrocatalysis and photoelectrolysis.
    09/2013; 5(5):184-190.
  • Anirudha Jena, N. Munichandraiah, S.A. Shivashankar
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    ABSTRACT: Carbonaceous nickel oxide powder samples have been synthesized from an adducted nickel β-ketoester complex used as a “single source precursor” through a solution-based microwave-assisted chemical route. Comprehensive analysis of the resulting powder material has been carried out using various characterization techniques. These analysis reveal that, depending on the solvent used, either NiO/C or Ni/NiO/C composites are formed, wherein Ni and/or NiO nanocrystals are enveloped in amorphous carbon. As the components emerge from the same molecular source, the composites are homogeneous on a fine scale, making them promising electrode materials for supercapacitors. Electrochemical capacitive behavior of these oxide composites is studied in a three-electrode configuration. With a specific capacitance of 113 F g−1, Ni/NiO/C is superior to NiO/C as capacitor electrode material, in 0.1 M Na2SO4 electrolyte. This is confirmed by impedance measurements, which show that charge-transfer resistance and equivalent series resistance are lower in Ni/NiO/C than in NiO/C, presumably because of the presence of metallic nickel in the former. The cyclic voltammograms are nearly rectangular and the electrodes display excellent cyclability in different electrolytes: Na2SO4, KOH and Ca(NO3)2·4H2O. Specific capacitance as high as 143 F g−1 is measured in Ca(NO3)2·4H2O electrolyte.
    Journal of Power Sources 09/2013; 237:156–166. · 5.26 Impact Factor
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    Surender Kumar, C Selvaraj, N Munichandraiah, L G Scanlon
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    ABSTRACT: Gold nanoparticles decorated reduced graphene oxide (Au–RGO) catalyst for O 2 electrode is prepared by in situ reduction of Au 3+ ions and graphene oxide dispersed in water. The Au nanoparticles are uniformly distributed on the two-dimensional RGO layers. Li–O 2 cells assembled in a non-aqueous electrolyte using Au–RGO catalyst exhibit an initial discharge capacity as high as 5.89 mA h cm À2 (5230 mA h g À1) at a current density of 0.1 mA cm À2 . The voltage gap between the charge and discharge curves is less for Li– O 2 (Au–RGO) cell in comparison with Li–O 2 (RGO) cell. The Li–O 2 (Au–RGO) cells are cycled over about 120 charge–discharge cycles. The results suggest that Au–RGO is a promising catalyst for rechargeable Li–O 2 cells.
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    Surender Kumar, C Selvaraj, N Munichandraiah, L G Scanlon
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    ABSTRACT: Gold nanoparticles decorated reduced graphene oxide (Au–RGO) catalyst for O 2 electrode is prepared by in situ reduction of Au 3+ ions and graphene oxide dispersed in water. The Au nanoparticles are uniformly distributed on the two-dimensional RGO layers. Li–O 2 cells assembled in a non-aqueous electrolyte using Au–RGO catalyst exhibit an initial discharge capacity as high as 5.89 mA h cm À2 (5230 mA h g À1) at a current density of 0.1 mA cm À2 . The voltage gap between the charge and discharge curves is less for Li– O 2 (Au–RGO) cell in comparison with Li–O 2 (RGO) cell. The Li–O 2 (Au–RGO) cells are cycled over about 120 charge–discharge cycles. The results suggest that Au–RGO is a promising catalyst for rechargeable Li–O 2 cells.
    RSC Advances 08/2013; · 3.71 Impact Factor
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    ABSTRACT: Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge–discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g−1 is obtained. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g−1. The rate capability study suggests that the sample provides about 150 mAh g−1 at a specific discharge current of 1.25 A g−1. Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.
    Journal of Solid State Electrochemistry 08/2013; · 2.28 Impact Factor
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    C. Selvaraj, Surender Kumar, A. R. Raju, N. Munichandraiah
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    ABSTRACT: Large area electrodes of MnO2 + polyaniline (PANI) composites of several compositions are fabricated with high specific mass of the active materials. Laboratory scale symmetric capacitors consisting of two similar electrodes separated by absorbent glass mat soaked in aqueous Mg(NO3)2 electrolytes are assembled. The capacitor made with a composite of MnO2+5 wt% PANI provides high capacitance and low equivalent series resistance. The results of long cycle life test conducted for the capacitors suggest that the capacitance of MnO2+5 wt% PANI capacitor is stable over 1000 charge-discharge cycles and the capacitance is greater than that of MnO2 capacitor. Ac impedance data suggest that the charge-transfer resistance (Rct) associated with Mn4+/Mn3+ redox process, which is noticeable at high frequency region is associated with build-up of pseudocapacitance, which is noticed at low frequency region. There is a gradual increase in Rct during the initial stages of cycling and thereafter it remains unchanged. MnO2+5 wt% PANI composite is found to be suitable for development of commercial capacitors.
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    ABSTRACT: Poorly crystalline porous d-MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 �C and the reaction time of 24 h. The as-synthesized sample and also the sample heated at 300 �C have nanopetals morphology with large surface area. On heating at temperatures P400 �C, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. Furthermore, the poorly crystalline d-MnO2 converts into well crystalline a-MnO2 phase. The electrochemical lithium intercalation and de-intercalation studies in a non-aqueous electrolyte provide a high discharge specific capacity (275 mAh g�1) at a specific current of 40 mA g�1 for the poorly crystalline d-MnO2 samples. The rate capability is also high. There is a decrease in capacity on repeated charge–discharge cycling. The specific capacity values of the crystalline a-MnO2 samples are considerably less than the values of poorly crystalline d-MnO2 samples. Thus, the hydrothermal route facilitates preparation of poorly crystalline electrochemically active porous MnO2.
    Journal of Electroanalytical Chemistry 06/2013; 703:126–134. · 2.58 Impact Factor

Publication Stats

621 Citations
327.48 Total Impact Points

Institutions

  • 1995–2010
    • Indian Institute of Science
      • • Department of Solid State and Structural Chemistry Unit
      • • Department of Inorganic and Physical Chemistry
      Bengalore, State of Karnataka, India
  • 2003
    • University of Southern California
      • Department of Chemistry
      Los Angeles, CA, United States