Browsing by Author "Ramakrishnan, Kalai Selvan"

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IMPROVED ELECTROCHEMICAL PERFORMANCES OF LIMNPO4 SYNTHESIZED BY A HYDROTHERMAL METHOD FOR LI-ION SUPERCAPATTERIES
(Springer, 2018-09-10) Natarjan, Priyadharsini; Amirthalingam, Shanmugavani; Subramani, Surendran; Baskar, Senthilkumar; Leonid, Vasylechko; Ramakrishnan, Kalai Selvan
Developing high-performance positrode materials are essential to attain high energy supercapatteries. In this regard, the electrochemical performances of the hydrothermally synthesized LiMnPO4 are studied. The crystal structures of the materials are elucidated using Full-profile XRD Rietveld refinement. The LiMnPO4 particles showed uniform elongated spherical shape with rice-like morphology. The rice-like LiMnPO4 showed a higher specific capacity of 492 C g−1 at 2 mV s−1 than highly agglomerated particles synthesized through sol–gel thermolysis method (191 C g−1) in 1 M LiOH aqueous electrolyte. The supercapattery is fabricated with rice-like LiMnPO4 and activated carbon (AC) as positrode and negatrode, respectively. The supercapattery (AC||LMP-H) delivered a higher capacitance around 99 F g−1 along with an improved energy density of 31 Wh kg−1. On the other hand, the LiMnPO4 prepared by sol–gel thermolysis method exhibited a very low capacitance of 35 F g−1 at 0.6 mA for the fabricated device (AC||LMP-S) with the lesser energy density about 11 Wh Kg−1 at a power density of 198 W kg−1. The reason behind the improved performance is explained based on the crystal structure as well as lower charge transfer resistance.
IMPROVED ELECTROCHEMICAL PERFORMANCES OF LIMNPO4 SYNTHESIZED BY A HYDROTHERMAL METHOD FOR LI-ION SUPERCAPATTERIES
(Springer Link, 2018-09-10) Natarjan, Priyadharsini; Amirthalingam, Shanmugavani; Subramani, Surendran; Baskar, Senthilkumar; Leonid, Vasylechko; Ramakrishnan, Kalai Selvan
Developing high-performance positrode materials are essential to attain high energy supercapatteries. In this regard, the electrochemical performances of the hydrothermally synthesized LiMnPO4 are studied. The crystal structures of the materials are elucidated using Full-profile XRD Rietveld refinement. The LiMnPO4 particles showed uniform elongated spherical shape with rice-like morphology. The rice-like LiMnPO4 showed a higher specific capacity of 492 C g−1 at 2 mV s−1 than highly agglomerated particles synthesized through sol–gel thermolysis method (191 C g−1) in 1 M LiOH aqueous electrolyte. The supercapattery is fabricated with rice-like LiMnPO4 and activated carbon (AC) as positrode and negatrode, respectively. The supercapattery (AC||LMP-H) delivered a higher capacitance around 99 F g−1 along with an improved energy density of 31 Wh kg−1. On the other hand, the LiMnPO4 prepared by sol–gel thermolysis method exhibited a very low capacitance of 35 F g−1 at 0.6 mA for the fabricated device (AC||LMP-S) with the lesser energy density about 11 Wh Kg−1 at a power density of 198 W kg−1. The reason behind the improved performance is explained based on the crystal structure as well as lower charge transfer resistance.
MORPHOLOGY-DEPENDENT ELECTROCHEMICAL PROPERTIES OF SOL-GEL SYNTHESIZED LICOPO4 FOR AQUEOUS HYBRID CAPACITORS
(Elsevier, 2018-11-01) Natarajan, Priyadharsini; Sathyanarayanan, Shanmugapriya; Palanisamy, Rupa Kasturi; Subramani, Surendran; Ramakrishnan, Kalai Selvan
Featured with superior structural stability and highest redox potential, the olivine LiCoPO4 parades itself as a conceit battery-type material. To deploy its foot in the field of hybrid supercapacitors a series of LiCoPO4 with three contrasting morphologies were achieved. The evolution of morphology from clustered microspheres to elongated rods and multifaceted submicronic particles has an appreciative effect on the particle size and electrochemical properties. Endowed with distinct qualities such as high crystallinity, and multifaceted morphology, LiCoPO4 prepared at alkaline pH provides a superior specific capacity of 381 C g−1 (1060 F g−1) at 1 mV s−1 and a maximum discharge specific capacity of 253 C g−1 (631 F g−1) at 0.6 mA cm−2. The fabricated hybrid supercapacitor using prepared LiCoPO4 at the pH-12 condition as a battery type positive electrode and Fe2O3 as the negative electrode provides a grander energy density of 18 Wh kg−1 at an enhanced power density of 443 W kg−1 with a sustained cyclic performance for about 5000 cycles.
SYNTHESIS AND ELECTROCHEMICAL PERFORMANCES OF Γ-KCOPO4 NANOCRYSTALS AS PROMISING ELECTRODE FOR AQUEOUS SUPERCAPATTERIES
(Chemistry Europe, 2019) Natarajan, Priyadharsini; Subramani, Surendran; Baskar, Senthilkumar; Leonid, Vasylechko; Ramakrishnan, Kalai Selvan
Herein, discrete γ-KCoPO4 nanocrystals were prepared by a facile, green and fast sol-gel route. The lattice parameters as well as positional and displacement parameters of atoms in the average γ-KCoPO4 structure with a space group of P21/n were calculated using full profile Rietveld refinement. Monodispersed quadrangular γ-KCoPO4 nanocrystals with improved phase purity and crystallinity were found through XRD patterns and HRTEM images. Subsequently, the prepared γ-KCoPO4 nanocrystals were tested as electrode material for supercapatteries in aqueous electrolytes. The γ-KCoPO4 electrode shows superior specific charge capacity of 309 C g−1 at 1 mV s−1 in 1 M KOH, compared to 1 M NaOH (222 C g−1) and 1 M LiOH (77 C g−1). Further, it exhibits improved electrochemical activity by delivering an impressive specific charge capacity of 100 C g−1 at a current of 0.6 mA cm−2 in an aqueous electrolyte medium with acceptable capacity retention. A lab-scale supercapattery was assembled resembling the commercial device. The fabricated device delivered an enhanced specific energy of 28 W h kg−1 and a specific power of 1600 W kg−1 and prolonged cycle life of about 5000 cycles.