Browsing by Author "Thirunakaran R"

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EFFECT OF MG DOPING ON THE LOCAL STRUCTURE OF LIMGYCO1−YO2 CATHODE MATERIAL INVESTIGATED BY X-RAY ABSORPTION SPECTROSCOPY
(Elsevier, 2014-04-15) Cheng H; Pan C J; Nithya C; Thirunakaran R; Gopukumar S; Chen C H; Lee J F; Chen J M; Sivashanmugam A; Hwang B J
A higher capacity and better cyclability are apparent when magnesium is introduced into the structure of LiCoO2 (y = 0.15). XRD analysis of LiMgyCo1−yO2 (y = 0, 0.1, 0.15), synthesized at 800 °C using a microwave assisted method, shows that the material is in the R-3m space group and to have a slightly expanded unit cell that increases with greater magnesium doping. Structural analysis by X-ray absorption spectroscopy (XAS) at the Co K-edge, L-edge and O K-edge shows that the magnesium is located in the transition metal layer rather than in the lithium layer and the charge balance results from the formation of oxygen vacancies rather than Co4+, while cobalt remains in the 3+ oxidation state. Interestingly, oxygen is found to participate in the charge compensation. Both magnesium, in the transition metal layer, and the Co-defect structure are attributed to the contribution towards structural stabilization of LiCoO2, thereby resulting in its enhanced electrochemical performance.
HIGH-CAPACITY SOL−GEL SYNTHESIS OF LINIXCOYMN1−X−YO2 (0 ≤ X, Y ≤ 0.5) CATHODE MATERIAL FOR USE IN LITHIUM RECHARGEABLE BATTERIES
(American Chemical Society, 2009-10-15) Nithya C; Thirunakaran R; Sivashanmugam A; Kiruthika G V M; Gopukumar S
Succinic acid assisted sol−gel synthesized layered LiNixCoyMn1−x−yO2 (0 ≤ x, y ≤ 0.5) materials have been studied as cathode materials for lithium rechargeable batteries. TG/DTA studies were performed on the gel precursor and suggest the formation of a layered phase around 400 °C. The gel precursor was calcined at 850 °C and characterized by means of X-ray diffraction and FT-IR analyses and reveals that all of the synthesized materials are found to be well-crystallized with an α-NaFeO2 layered structure. The effect of Co content on the surface morphology has been examined by scanning electron microscopy, and X-ray photoelectron spectroscopy studies indicate that the oxidation states of nickel, cobalt, and manganese are +2, +3, and +4, respectively. The electrochemical galvanostatic charge/discharge cycling behavior of the synthesized layered materials has been evaluated in the voltage range of 2.7–4.8 V at C/10 and C/5 rates. LiCo0.1Ni0.4Mn0.5O2 cathode material delivered the highest average discharge capacity of ~175 mAh/g at C/10 rate over the investigated 50 cycles.
MICROWAVE ASSISTED SYNTHESIS AND ELECTROCHEMICAL BEHAVIOUR OF LIMG0.1CO0.9O2 FOR LITHIUM RECHARGEABLE BATTERIES
(Elsevier, 2009-01-04) Zaheena C N; Nithya C; Thirunakaran R; Sivashanmugam A; Gopukumar S
Layered LiMg0.1Co0.9O2 has been synthesized using microwave assisted solution technique. The precursorhas been subjected to thermo-gravimetric/differential thermal analysis (TG/DTA) and calcined at 850◦C.The precursor and the calcined powders were characterized by X-ray diffraction (XRD) to confirm theformation of single-phase layered material. Fourier transform infrared (FTIR) studies were carried out to understand the nature of the metal–ligand bond and the observations were consistent with the XRDspectrum. Scanning (SEM) and transmission electron microscope (TEM) images have been obtained tounderstand the surface morphology and the grain orientation of the synthesized material. Coin cells of2016 type have been assembled using the synthesized layered material as the cathode active material,lithium foil as the counter and reference electrodes and 1M LiPF6 in 1:1 EC/DEC as the electrolyte. Coincellswere assembled and crimp sealed inside an argon filled glove box. The charge/discharge characteristicsof the coin cellswere evaluated galvanostatically in the potential range 2.7–4.3 V. Results indicate thatLiMg0.1Co0.9O2 delivers an average discharge capacity of∼135mAhg−1 over the investigated 20 cycles andis a potential candidate for use as cathode material in lithium rechargeable cells
MICROWAVE SYNTHESIS OF NOVEL HIGH VOLTAGE (4. 6V), HIGH CAPACITY LICUXCO1-XO2±Δ CATHODE MATERIAL FOR LITHIUM RECHARGEABLE CELLS
(Elsevier, 2011-08-15) Nithya C; Thirunakaran R; Sivashanmugam A; Gopukumar S
Layered LiCuxCo1−xO2±δ (0.0 ≤ x ≤ 0.3) has been synthesized using microwave method. This method possesses many advantages such as homogeneity of final product and shorter reaction time compared to other conventional methods. The structure and electrochemical properties of the synthesized materials are characterized through various methods such as XRD, SEM, FTIR, XPS and galvanostatic charge/discharge studies. The XRD patterns of LiCuxCo1−xO2±δ confirm the formation of single-phase layered material. SEM images show that the particles are agglomerated and the average particle size decreases with increasing amount of copper. Electrochemical cycling studies are carried out between 2.7 and 4.6 V using 1 M LiPF6 in 1:1 EC/DEC as electrolyte. The charge/discharge cycling studies of layered material with LiCu0.2Co0.8O1.9 exhibit an average discharge capacity of ∼150 mAh g−1 over the investigated 50 cycles..
SOLAR POWERED NEW LITHIUM ION BATTERY INCORPORATING HIGH PERFORMING ELECTRODE MATERIALS
(Royal Society of Chemistry, 2012-10-01) Gopukumar S; Nithya C; Thirunakaran R; Sivashanmugam A; Dhawan S K; Mathur R B; Maheshwari P H
The development of portable electronic communities requires high performing and high power lithium rechargeable batteries. Herein, we explore a new lithium ion battery combined with a new carbon based anode and cobalt based cathode which delivers an energy output of 280 Wh kg−1 and cycling efficiency of 97% over the investigated 500 cycles (1 C rate) of the lithium ion cell.