Browsing by Author "Gopukumar S"

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CHAPTER FIFTEEN - NANOSTRUCTURED TRANSITION METAL CHALCOGENIDES FOR RECHARGEABLE BATTERIES
(Elsevier, 2021-01-29) Nithya C; Gopukumar S
Rechargeable lithium/sodium-ion batteries and emerging potassium-ion batteries are considered as the promising energy storage devices for potential high-current rate applications. It has been considered that transition metal chalcogenides (mono- and di-) are a class of two-dimensional compounds (metal sulfides and metal selenides) attracting growing research interest as an anode materials for rechargeable batteries. They have shown efficient energy storage properties owing to their unique physiochemical properties. In this chapter, we systematically discussed and summarized the recent research progress on the nanostructured transition metal chalcogenides (TMCs) for LIBs, NIBs, and KIBs. Here, we presented the electrochemical reaction kinetics, challenging issues, and effective strategies toward the improvement of TMCs for rechargeable batteries. To the end the remaining challenges and outlooks for the further development of TMCs in the field of rechargeable batteries are proposed.
DIAMONDOID-STRUCTURED CU–DICARBOXYLATE-BASED METAL–ORGANIC FRAMEWORKS AS HIGH-CAPACITY ANODES FOR LITHIUM-ION STORAGE
(WILEY‐VCH Verlag, 2014-11-10) Senthikumar R; Nithya C; Gopukumar S; AnbuKulandainathan M
A versatile electrochemical synthetic route is proposed for the preparation of [Cu2(C8H4O4)4]n metal–organic frameworks. The synthesized composites are characterized by using XRD, SEM, FTIR, and Brunauer–Emmett–Teller (BET) surface analysis. The average particle size was measured to be 8.27 nm and the pore size determined to be 14.06 nm. Here, for the first time, we demonstrate the Cu‐based metal–organic frameworks [Cu2(C8H4O4)4]n as a new class of porous crystalline materials that have the ability to reversibly store Li+ ions. Galvanostatic charge/discharge studies suggest that the terephthalate network reversibly reacts with Li and shows high capacity retention (≈84 % over 50 cycles). The best reversible capacity of 227 mAh g−1 (approximately 95 % of the theoretical capacity) has been achieved in the first cycle at a current density of 24 mA g−1. An easily scalable electrochemical synthesis of the [Cu2(C8H4O4)4]n metal–organic frameworks is an attractive candidate for use with lithium‐ion batteries.
EFFECT OF MG DOPANT ON THE ELECTROCHEMICAL PERFORMANCE OF LINI0.5MN0.5O2 CATHODE MATERIALS FOR LITHIUM RECHARGEABLE BATTERIES
(IOP Publishing, 2010-06-16) Nithya C; Lakshmi R; Gopukumar S
Positive electrode materials, LiMg x Ni0.5−x Co0.5O2 (x = 0 < x < 0.5), have been successfully synthesized by microwave-assisted solution technique. The precursor has been analyzed by TG/DTA and the powder was calcined at 850 °C. The XRD patterns reveal that the synthesized materials exhibit hexagonal layered structure corresponding to R3-m space group. Coin cells of 2016 type have been fabricated using the synthesized layered material as cathode active material and lithium foil used as counter and reference electrode. Test cells were operated in the potential limits between 2.7 and 4.3 V using 1 M LiPF6 in 1:1 EC/DEC as electrolyte. LiMg0.2Ni0.3Co0.5O2 material delivers an average discharge capacity of around 165 mA hg−1 at 0.1 C rate over the investigated 20 cycles.
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 PERFORMANCE NAXCOO2 AS A CATHODE MATERIAL FOR RECHARGEABLE SODIUM BATTERIES
(Royal society of Chemistry, 2015-07-24) Venkata Rami Reddy B; Ravikumar R; Nithya C; Gopukumar S
Sodium cobalt oxide (NCO) has been synthesized by a glycine assisted sol–gel combustion method. XRD studies confirm the P2 phase formation of NCO. Na exists in two different environments in the NCO crystallite structure, which is confirmed by 23Na Nuclear Magnetic Resonance spectra (NMR). Morphological studies confirm that the particles are unique with a stacked hexagonal shape. Galvanostatic charge/discharge studies performed at different current rates (0.1, 0.2 and 0.5) deliver reversible specific capacities of 126, 108 and 77 mA h g−1 respectively. Further, cycle life performance of the fabricated cells after 50 cycles at 0.1 C rate exhibits an average discharge capacity of ~121 mA h g−1 with a capacity retention of ~86% (Coulombic efficiency ~99.9%). The investigated NCO's superior performance suggests its suitability as a cathode material for Na-ion batteries.
HIGH PERFORMING SNXSBYCUZ COMPOSITE ANODES FOR LITHIUM ION BATTERIES
(Elsevier Masson, 2013-05-01) Nithya C; Sowmiya T; VijayaBaskar K; Selvaganeshan N; Kalaiyarasi T; Gopukumar S
To increase the volumetric discharge capacity of negative electrode for rechargeable lithium batteries, a composite anode SnxSbyCuz has been synthesized by using high energy mechanical ball milling method. The synthesized composite anode materials have been characterized by X-ray diffraction and SEM analysis. The charge/discharge characteristics of the fabricated coin cells have been evaluated galvanostatically in the potential range 0.01–2 V using 1 M LiPF6 in 1:1 EC/DEC as electrolyte. Results indicate that the composition with 90 wt% Sn, 8 wt% Sb and 2 wt% Cu delivers an average discharge capacity of 740 mAh g−1 over the investigated 50 cycles which is a potential candidate for use as an anode material for lithium rechargeable cells.
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..
A MN3O4NANOSPHERES@RGO ARCHITECTURE WITH CAPACITIVE EFFECTS ON THE HIGH POTASSIUM STORAGE CAPABILITY
(Royal Society of Chemistry, 2019-09-10) Nithya C; Vishnuprakash P; Gopukumar S
A two dimensional (2D) Mn3O4@rGO architecture has been investigated as an anode material for potassium-ion secondary batteries. Herein, we report the synthesis of a Mn3O4@rGO nanocomposite and its potassium storage properties. The strong synergistic interaction between high surface area reduced graphene oxide (rGO) sheets and Mn3O4 nanospheres not only enhances the potassium storage capacity but also improves the reaction kinetics by offering an increased electrode/electrolyte contact area and consequently reduces the ion/electron transport resistance. Spherical Mn3O4 nanospheres with a size of 30–60 nm anchored on the surface of rGO sheets deliver a high potassium storage capacity of 802 mA h g−1 at a current density of 0.1 A g−1 along with superior rate capability even at 10 A g−1 (delivers 95 mA h g−1) and cycling stability. A reversible potassium storage capacity of 635 mA h g−1 is retained (90%) after 500 cycles even at a high current density of 0.5 A g−1. Moreover, the spherical Mn3O4@rGO architecture not only offers facile potassium ion diffusion into the bulk but also contributes surface K+ ion storage. The obtained results demonstrate that the 2D spherical Mn3O4@rGO nanocomposite is a promising anode architecture for high performance KIBs.
REDUCED GRAPHENE OXIDE/SNNANO COMPOSITE: A SUPERIOR ANODE FOR LITHIUM ION BATTERIES
(WILEY‐VCH Verlag, 2013-02-05) Nithya C; Gopukumar S
The electrochemical performance of reduced graphite oxide (RGO) anchored with nanoSn 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.
RGO /NANOSB COMPOSITE: A HIGH PERFORMING ANODE MATERIAL FOR NA+ ION BATTERIES AND EVIDENCE FOR FORMATION OF NANORIBBONS FROM NANO RGO SHEET DURING GALVANOSTATIC CYCLING
(Elsevier, 2014-05-08) Nithya C; Gopukumar S
Lithium ion batteries exhibit high energy and power densities, thereby making them a promising power sources for multifarious applications. However, the abundance of lithium (Li) is one of the major critical issues for using Li battery technologies. Therefore, for large-scale applications a sodium (Na) ion battery is one of the apt alternatives for portable electronics instead of expensive Li ion batteries. One of the challenging issues in Na+ ion batteries is the difficulty to understand the chemistry involved in view of the large size of the Na+ ion as compared to the Li+ ion, which makes the alloying/dealloying difficult during cycling. Hence, in this present work, we explore an innovative concept of storing Na+ ions in reduced graphene oxide/antimony (Sb) metal composites. Such a concept of storing Na+ in the rGO/Sb composite is one of the simplest ways to enhance the electrochemical performance of metal-based anodes for sodium ion batteries. Furthermore, it is seen that the nanorGO sheet transforms to nanoribbons upon galvanostatic cycling, as evidenced by TEM.
ROLE OF MG DOPANT ON THE ELECTROCHEMICAL PERFORMANCE OF LICO0.5NI0.5O2 CATHODE MATERIALS FOR LITHIUM RECHARGEABLE BATTERIES
(Springer US, 2012-01-10) Nithya C; Bharathi Devi S; Gopukumar S
Positive electrode materials, LiMg x Ni0.5−x Co0.5O2 (x = 0 < x < 0.5), have been successfully synthesized by microwave-assisted solution technique. The precursor has been analyzed by TG/DTA and the powder was calcined at 850 °C. The XRD patterns reveal that the synthesized materials exhibit hexagonal layered structure corresponding to R3-m space group. Coin cells of 2016 type have been fabricated using the synthesized layered material as cathode active material and lithium foil used as counter and reference electrode. Test cells were operated in the potential limits between 2.7 and 4.3 V using 1 M LiPF6 in 1:1 EC/DEC as electrolyte. LiMg0.2Ni0.3Co0.5O2 material delivers an average discharge capacity of around 165 mA hg−1 at 0.1 C rate over the investigated 20 cycles.
SB2O4@RGO NANOCOMPOSITE ANODE FOR HIGH PERFORMANCE SODIUM-ION BATTERIES
(American Chemical Society, 2017-06-05) Kiruthiga R; Nithya C; Bindhya K P; Nitesh Kumar; Gopukumar S
Research on high performance electrode materials is significant for further development of sodium ion batteries (NIBs). The Sb2O4 anode can be employed as a promising anode material for NIBs owing to its high theoretical capacity of 1227 mAhg–1. In this paper, we report the Sb2O4@rGO nanocomposite anode for NIBs which exhibit good cyclability and rate capability due to the formation of wrinkled rGOnanosheets during cycling. Well-formed nanowrinkles act as a template for anchoring Sb2O4 particles during cycling and effectively alleviate the strain due to the volume expansion. The improved electrochemical performance is attributed to the shorter Na+ ion diffusion path length from the small nanoparticles and good electrons as well as ion transport from the intimate contact between the active Sb2O4 particles and rGO matrix. At a current density of 0.1 Ag–1, it retains the 94.2% (890 mAhg–1) of initial reversible capacity after 100 cycles. Over prolonged cycling (after 500 cycles), the Sb2O4@rGO electrode still delivers a reversible capacity of 626 mAhg–1 at a current density of 0.6 Ag–1. These significant results offer hope for the exploration of making high capacity anodes combined with a reduced graphene oxide matrix to alleviate the strain during cycling.
SODIUM ION BATTERIES: A NEWER ELECTROCHEMICAL STORAGE
(Wiley Periodicals, Inc., 2015-07-24) Nithya C; Gopukumar S
Vehicle electrification is one of the most significant solutions that address the challenges of fossil fuel depletion, global warming, CO2 pollution, and so on. To mitigate these issues, recent research mainly focuses on finding clean energy storage devices such as batteries, supercapacitors, fuel cells, and so forth. Owing to the outstanding energy and power density, lithium‐ion batteries (LIB) have captured the market for portable electronics, hybrid electric vehicles, plug‐in hybrid electric vehicles, and so on. During 1970–1980s, electrode materials for both LIBs and sodium‐ion batteries (NIBs) were investigated but higher energy and power density of LIBs have made it a popular candidate for portable electronics. Issues arise on the availability of lithium reserves, so it is high time we take a look at finding alternative energy storage system without compromising on the energy and power density of the state‐of‐the‐art LIBs. Therefore, researchers have revisited NIBs and recent developments have contributed towards discovering new electrode materials to match the energy and power density of LIBs at low cost. While a variety of positive and negative electrode materials have been investigated for NIBs so far, the influence of voltage, capacity, cycle life, and volume expansion of negative electrodes on Na+ ion extraction and insertion are more as compared with LIBs. This affects the energy and power density of NIBs but cost‐effective partial replacement of LIBs is viable and is widely pursued.
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.
SYNTHESIS OF HIGH VOLTAGE (4.9 V) CYCLING LINIXCOYMN1-X-YO2 CATHODE MATERIALS FOR LITHIUM RECHARGEABLE BATTERIES
(Royal Society of Chemistry, 2011-02-24) Nithya C; SyamalaKumari V S; Gopukumar S
Layered mixed oxides LiNixCoyMn1−x−yO2 (0 ≤ x, y ≤ 0.5) synthesized by a sol–gel method using tartaric acid as a chelating agent, and their structural and electrochemical properties are investigated by thermal analysis, XRD, SEM, FT-IR and XPS studies. The higher composition of Co leads to cation disorder and shrinks the cell volume. Electrochemical behaviour of the synthesized materials is evaluated by Galvanostatic charge/discharge studies using 2016 type coin cells. The cycling studies are carried out in the voltage limits of 2.7 to 4.6, 4.8 and 4.9 V at current rates of C/10 and C/5 respectively. The composition LiNi0.4Co0.1Mn0.5O2 exhibits an average discharge capacity of 192 mA h g−1 at the current density of 0.612 mA cm−2 (C/5) in the voltage range of 2.7–4.9 V as compared to the discharge capacity of 155 and 175 mA h g−1 in the potential range of 2.7–4.6 and 2.7–4.8 V over the 50 investigated cycles. The effect of higher charge voltage at 4.9 V on the electrochemical performance of LiNixCoyMn1−x−yO2oxide materials has not previously been reported.
THERMODYNAMIC ANALYSIS OF LITHIUM-ION BATTERY STORAGE SYSTEM
(Elsevier, 2022) Nithya C; Gopukumar S
The most promising energy storage systems are lithium-ion batteries (LIBs) owing to its high energy and power density. The electrochemical lithium storage in LIB is investigated in terms of thermodynamic functions such as free energy, entropy, enthalpy and heat capacities. These thermodynamic functions are influenced by various factors such as temperature, porosity, defects in electrode materials, solvation of Li+ ions by electrolyte solvents, double layer formation between electrode/electrolyte, phase transition during cycling and coexistence of Li intercalation reaction in single-phase and multiphase etc. Herein, we have analyzed the thermodynamics of overall electrochemical lithium storage and this analysis helpful to explore the stable electrode and electrolyte materials for next generation of LIBs and beyond.