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Dive into the research topics where S. Gopukumar is active.

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Featured researches published by S. Gopukumar.


Chemsuschem | 2013

Reduced graphite oxide/nano Sn: a superior composite anode material for rechargeable lithium-ion batteries.

C. Nithya; S. Gopukumar

The electrochemical performance of reduced graphite oxide (RGO) anchored with nano Sn particles, which are synthesized by a reduction method, is presented. The Sn nanoparticles are uniformly distributed on the surface of the RGO matrix and the size of the particles is approximately 5-10 nm. The uniform distribution effectively accommodates the volume expansion experienced by Sn particles during cycling. The observed electrochemical performance (97 % capacity retention) can be ascribed to the flexible RGO matrix with uniform distribution of Sn particles, which reduces the lithium-ion diffusion path lengths; therefore, the RGO matrix provides more stability to the Sn particles during cycling. Such studies on Sn nanoparticles anchored on RGO matrices have not been reported to date.


Physical Chemistry Chemical Physics | 2013

High quality NMP exfoliated graphene nanosheet–SnO2 composite anode material for lithium ion battery

Raman Ravikumar; S. Gopukumar

A graphene nanosheet-SnO(2) (GNS-SnO(2)) composite is prepared using N-methylpyrrolidone as a solvent to exfoliate graphene from graphite bar with the aid of CTAB by single phase co-precipitation method. The synthesized composites has been characterised physically by powder XRD which confirms the formation of the composite tetragonal SnO(2) crystal system with the low intense broad 002 plane for GNS. The sandwiched morphology of GNS-SnO(2) and the formation of nanosized particles (around 20 nm) have been confirmed by SEM and TEM images. The presence of sp(2) carbon in the GNS is clear by the highly intense G than D band in laser Raman spectroscopy analysis; furthermore, a single chemical shift has been observed at 132.14 ppm from solid-state (13)C NMR analysis. The synthesized composite has been electrochemically characterized using charge-discharge and EIS analysis. The capacity retentions at the end of the first 10 cycles is 57% (100 mA g(-1) rate), the second 10 cycles is 77.83% (200 mA g(-1)), and the final 10 cycles (300 mA g(-1)) is 81.5%. Moreover the impedance analysis clearly explains the low resistance pathway for Li(+) insertion after 30 cycles when compared with the initial cycle. This superior characteristic of GNS-SnO(2) composite suggests that it is a promising candidate for lithium ion battery anode.


ACS Applied Materials & Interfaces | 2012

High-Performing LiMgxCuyCo1–x–yO2 Cathode Material for Lithium Rechargeable Batteries

C. Nithya; R. Thirunakaran; Arumugam Sivashanmugam; S. Gopukumar

Sustainable power requirements of multifarious portable electronic applications demand the development of high energy and high power density cathode materials for lithium ion batteries. This paper reports a method for rapid synthesis of a cobalt based layered cathode material doped with mixed dopants Cu and Mg. The cathode material exhibits ordered layered structure and delivers discharge capacity of ∼200 mA h g(-1) at 0.2C rate with high capacity retention of 88% over the investigated 100 cycles.


Journal of The Electrochemical Society | 2004

Thermal Stability of Electrolytes with Mixtures of LiPF6 and LiBF4 Used in Lithium-Ion Cells

Eui Sun Hong; Shigeto Okada; Takaki Sonoda; S. Gopukumar; Jun-ichi Yamaki

Thermal stability studies of electrolytes with mixtures of LiPF 6 and LiBF 4 were carried out using differential scanning calorimetry. The solvent was a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in the volume ratio of 3:3:1, respectively. We expected the occurrence of two independent exothermic peaks associated with LiPF 6 at the lower temperature and lithium LiBF 4 at the higher temperature, due to decomposition reactions resulting in the Lewis acids PF 5 and BF 3 . Instead, the mixed salt electrolyte exhibited a single exothermic peak. We deduced that the HF produced by the reaction of LiPF 6 with solvent was the reason for the existence of one exothermic reaction peak. The HF may react with LiBF 4 to give HBF 4 , which is very unstable and decomposes easily to HF and BF 3 at a lower temperature than the decomposition temperature of LiBF 4 itself. By comparison, a thermal study of a mixed salt electrolyte including LiPF 6 and LiN(SO 2 CF 3 ) 2 showed that the exothermic reaction of LiN(SO 2 CF 3 ) 2 with solvents is also influenced by HF produced in the reaction of LiPF 6 with solvents but that the strength of the influence is small compared with its effect on an electrolyte mixture including LiBF 4 .


Chemistry-an Asian Journal | 2012

LiCoxMn1‐xPO4/C: A High Performing Nanocomposite Cathode Material for Lithium Rechargeable Batteries

C. Nithya; R. Thirunakaran; Arumugam Sivashanmugam; S. Gopukumar

Pristine and Co-doped LiMnPO(4) have been synthesized by the sol-gel method using glycine as a chelating agent and the carbon composites were obtained by the wet ball mill method. The advantage of this method is that it does not require an inert atmosphere (economically viable) and facilitates a shorter time for synthesis. The LiCo(0.09)Mn(0.91)PO(4)/C nanocomposites exhibit the highest coulombic efficiency of 99 %, delivering a capacity of approximately 160 mAhg(-1) and retain a capacity of 96.3 % over the investigated 50 cycles when cycled between 3-4.9 V at a charge/discharge rate of 0.1 C.


Journal of The Electrochemical Society | 2006

Glycine-Assisted Sol-Gel Combustion Synthesis and Characterization of Aluminum-Doped LiNiVO4 for Use in Lithium-Ion Batteries

A. Sivashanmugam; R. Thirunakaran; Meijing Zou; Masaki Yoshio; Jun-ichi Yamaki; S. Gopukumar

Phase-pure inverse spinel LiNiVO 4 and LiAl x Ni 1-x VO 4 have been synthesized with good surface morphology by a sol-gel method using glycine as a chelating agent. The product was characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and galvanostatic cycling studies. Surface morphology examinations of the undoped LiNiVO 4 particles showed micrometer-sized, cube-shaped grains, while that of aluminum-doped particles showed uniform spherical particles. As compared to the solid-state synthesis route, the sol-gel combustion process greatly reduces the temperature (250°C) for preparing LiNiVO 4 and LiAl x Ni 1-x VO 4 . Subsequent calcination between 650 and 850°C significantly enhances the crystallinity of the synthesized LiNiVO 4 and LiAl x Ni 1-x VO 4 powder. The discharge capacity and cycling performance of the LiAl 0.1 Ni 0.99 VO 4 was found to be superior at a calcination temperature of 250°C.


Journal of The Electrochemical Society | 2009

Electrochemical Behavior of LiM0.25Ni0.25Mn1.5O4 as 5 V Cathode Materials for Lithium Rechargeable Batteries

S. Rajakumar; R. Thirunakaran; A. Sivashanmugam; Jun-ichi Yamaki; S. Gopukumar

Glycine-assisted sol-gel-synthesized multiple-doped spinels, LiM 0.25 Ni 0.25 Mn 1.5 O 4 (M = Cr, Fe, and Co) have been studied as 5 V cathode materials. The sol-gel technique provides homogeneity, high purity, lower processing temperature, controlled particle size, and morphology. The synthesized samples were subjected to physical characterization studies, viz., thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical charge-discharge studies. Galvanostatic charge-discharge studies of the samples reveal that LiFe 0.25 Ni 0.25 Mn 1.5 0 4 using glycine as a chelating agent delivers a stable capacity of 120 mAh g -1 even after 20 cycles when cycled between 3 and 5 V.


Journal of The Electrochemical Society | 2008

Sol-Gel Synthesis of 5 V LiCu x Mn2 − x O4 as a Cathode Material for Lithium Rechargeable Batteries

A. Sulochana; R. Thirunakaran; A. Sivashanmugam; S. Gopukumar; Jun-ichi Yamaki

Spinel LiCu x Mn 2-x O 4 (0.025 < x ≤ 0.1) has been synthesized using oxalic acid as the chelating agent using a sol-gel method to obtain submicrometer-sized particles, good surface morphology, homogeneity, agglomeration, and high crystallinity involving short heating time. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis were carried out for the physical characterization of the synthesized powder. The XRD patterns of LiCu x Mn 2-x O 4 show the single-phase spinel product, which is in good agreement with the JCPDS card (35-782). SEM images show that the particles, on the average, are of 50 nm in size and are present as agglomerated clusters at all dopant levels. Electrochemical cycling studies of the compound were carried out between 3 and 5 V to understand the redox behavior of Cu 2+ ions. The charge-discharge cycling studies of spinel material with Cu stoichiometry of x=0.1 calcined at 850°C exhibit an initial discharge capacity of 130 mAh g -1 and stabilized at 120 mAh g -1 .


Journal of The Electrochemical Society | 2010

Synthesis, Characterization, and Electrochemical Properties of LiCr x Ni y Mn2 − x − y O4 Spinels as Cathode Material for 5 V Lithium Battery

S. Rajakumar; R. Thirunakaran; A. Sivashanmugam; S. Gopukumar

Sol-gel assisted spinel LiCrxNiyMn2�xyO4 0 x 0.4 and 0 y 0.4 has been synthesized. The thermal study of the precursor was carried out by thermogravimetric and differential thermal analyses. Furthermore, the material has been subjected to X-ray diffraction, scanning electron microscopy, Fourier transform IR spectroscopy analysis, X-ray photoelectron spectroscopy, cyclic voltammetry studies, and electrochemical charge-discharge studies. The X-ray diffraction of LiCrxNiyMn2�xyO4 matches well with the Joint Committee on Powder Diffraction Standard card no. 35-782, confirming the formation of a single-phase spinel. Charge-discharge studies were carried out between 3 and 5 V to understand the electrochemical behavior of the undoped and doped spinels. LiCr0.25Ni0.25Mn1.5O4 calcined at 850°C possesses a particle size of around 70 nm and exhibits an initial discharge capacity of 105 mAh g�1 stabilizing at 98 mAh g�1 over the investigated 20 cycles. However, maleic acid derived LiCr0.25Ni0.25Mn1.5O4 delivers a stable higher discharge capacity of 115 mAh g�1 over the investigated 20 cycles and is a promising 5 V cathode material. In this present study, LiCrxNiyMn2�xyO4 0 x 0.4 and 0 y 0.4 using glycine or maleic acid as chelating agents has been synthesized by a sol-gel technique. The physical and electro- chemical studies of the synthesized material have been done, and the experimental results are discussed. Experimental Figure 1 shows the flow chart for the synthesis of LiCrxNiyMn2�xyO4 by a sol-gel method using glycine or maleic acid as chelating agents. Stoichiometric amounts of nitrates of lithium, manganese, chromium, and nickel were uniformly mixed and dissolved in triple-distilled water. This solution was continu- ously stirred for some time with mild heating to obtain a homoge- neous solution. The solution was added drop by drop into an aque- ous solution of 3 M glycine o r1Mm aleic acid solution, which is used as chelating agent. The pH of the solution was adjusted be- tween 5 and 7.5 using ammonia solution. The process of stirring and heating was continued until a solid gel was obtained. Furthermore, the gel was initially heated overnight at 110°C. The thermal behav- ior of the gel precursors was characterized by thermogravimetry TG and differential thermal analysis DTA in a PL Thermal Sci- ences Instrument model STA 1500. All experiments were carried out in air at a heating ramp of 20°C/min with typically 50 mg samples. Furthermore, this gel mass was calcined at different temperatures, viz., 250, 400, 600, and 850°C fo r8hi nalumina crucibles. The resulting calcined samples are physically characterized using an X-ray diffractometer XRD, JEOL 8030 with nickel filtered Cu K radiation, a scanning electron microscope SEM, Hitachi S-3000 H, a Fourier transform infrared FTIR spectroscope Perkin-Elmer, model paragon-500 spectrophotometer, and an X-ray photoelectron spectroscope XPS, VG electron spectroscope X-ray source Al K radiation with a scan range of 0-1200 eV binding energy. The col-


ACS Applied Materials & Interfaces | 2017

High rate performing in-situ nitrogen enriched spherical carbon particles for Li/Na-ion cells

Vadivel Selvamani; Sivalingam Gopi; Venkatachalam Rajagopal; Murugavel Kathiresan; Suryanarayanan Vembu; D. Velayutham; S. Gopukumar

Nitrogen rich, porous spherical carbon particle with the large surface area was synthesized by simple pyrolysis of the amorphous covalent organic framework. The obtained mesoporous spherical carbon particles with dilated interlayer distance (0.377 nm), large surface area (390 m2 g-1) and high level nitrogen doping (10.9%) offer eminent electrochemical performance as an anode for both lithium ion (LIBs) and sodium ion batteries (SIBs). In LIB applications, the synthesized material delivers an average reversible capacity of 820 mAh g-1 after 100 cycles at 0.1 A g-1, superior rate capability of 410 and 305 mAh g-1 at 4.0 and 8.0 A g-1 respectively. In SIBs, the material shows the stable reversible capacity of about 238 mAh g-1 for the studied 500 cycles at 0.5 A g-1. The rate and steady state cycling performance at high current densities are impressive, being as high as 165 mAh g-1 even after 250 cycles at 2.0 A g-1.

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R. Thirunakaran

Council of Scientific and Industrial Research

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A. Sivashanmugam

Council of Scientific and Industrial Research

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C. Nithya

National Institute of Technology

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Arumugam Sivashanmugam

Council of Scientific and Industrial Research

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D. Velayutham

Council of Scientific and Industrial Research

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Raman Ravikumar

Council of Scientific and Industrial Research

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Bhanu Pratap Singh

Council of Scientific and Industrial Research

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Indu Elizabeth

National Physical Laboratory

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