We report the synthesis of TiNb 2 O 7 /Graphene (TNO-TG) hybrid nanomaterial by simple solvotherm... more We report the synthesis of TiNb 2 O 7 /Graphene (TNO-TG) hybrid nanomaterial by simple solvothermal process, with TiNb 2 O 7 nanoparticles anchored on the reduced graphene oxide (rGO) sheets. TNO-TG hybrid nanomaterial showed excellent electrochemical performance when studied as anode for Lithium-ion battery, with an exceptionally high rate capability (capacity retention of 80% at 16 C rate) along with high discharge capacity (~ 230 mAhg-1 after 50 cycles at 0.1 C). A full cell Li-ion battery has been fabricated with TNO-TG as anode and LiNi 1/3 Mn 1/3 Co 1/3 O 2 :LiNi 0.5 Mn 0.5 O 2 (wt% of 75:25) as cathode, which delivered an average cell voltage of ~2.5 V with an initial anode-specific discharge capacity of 211 mAhg-1 , when cycled in the voltage range of 1.5-3.5 V at 0.1 C. The obtained results are very promising and we believe the current findings will lead to new directions in the ongoing search for safe and high performance anodes for rechargeable lithium-ion batteries.
Li-rich layered oxides are the most attractive cathodes for lithium-ion battery due to high capac... more Li-rich layered oxides are the most attractive cathodes for lithium-ion battery due to high capacity (>250 mAh g-1). However, its application in electric vehicles are hampered by low power density and poor cycle life. To address these, layered Li2Ru0.75Ti0.25O3 (LRTO) were synthesized and the influence of electroinactive Ti4+ on the electrochemical performance of Li2RuO3 were investigated. LRTO exhibited reversible capacity of 240 mAh g-1 under 14.3 mA g-1 with 0.11 moles of Li loss after 100 cycles compared to 0.22 moles of Li for Li2Ru0.75Sn0.25O3. More Li+ can be extracted from LRTO (0.96 moles of Li) even after 250 cycles at 143 mA g-1 than Li2RuO3 (0.79 moles of Li). High reversible Li extraction and long cycle life were attributed to structural stability of LiM2 layer in the presence of Ti4+, facilitating the lithium diffusion kinetics. The versatility of Li2MO3 structure may initiate exploration of Ti based Li-rich layered oxides for vehicular applications.
ABSTRACT We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that... more ABSTRACT We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that mimics diurnal natural daylight with the newly designed phosphor blend in the color temperature (CCT) 2700–6000 K for health benefits. Natural daylight (sunlight) spectrum possesses broad emission in the visible region and closely approximates black body radiator, with color rendition index (CRI) of 100 under wide CCT (2500–6500 K). Current white light LEDs although are efficient and durable, they are not broad enough compared to daylight. We report new phosphor blend based on Sr3MgSi2O8:Eu2+ blue phosphor with broad emission and high CRI ≥ 96 under both near UV and blue excitation. The fabricated WLED has exhibited ∼91% spectral resemblance with natural daylight compared to 39.2% for YAG:Ce3+ white LED at 4500 K. The developed phosphor blend tunes the spectrum in wider CCT and would be a prospective candidate for full spectrum daylight WLED.
ABSTRACT White light emitting alkali metal ion co-doped single host lattice phosphors Sr2.955B2O6... more ABSTRACT White light emitting alkali metal ion co-doped single host lattice phosphors Sr2.955B2O6:0.02Ce3+, 0.005Eu2+, 0.02A+ [A=Li, Na and K] were synthesized by high temperature solid state reaction. The synthesized phosphors were characterized by powder X-ray diffraction and Fourier transform infrared spectroscopic techniques. The optical properties were studied using diffuse reflectance UV-vis reflectance spectroscopy and photoluminescence (PL) spectroscopy. The role of Ce3+ as a sensitizer of Eu2+ was found from PL excitation results. The PL white light emission depends on the nature of co-doped alkali metal ion charge compensator.
We report the synthesis of TiNb 2 O 7 /Graphene (TNO-TG) hybrid nanomaterial by simple solvotherm... more We report the synthesis of TiNb 2 O 7 /Graphene (TNO-TG) hybrid nanomaterial by simple solvothermal process, with TiNb 2 O 7 nanoparticles anchored on the reduced graphene oxide (rGO) sheets. TNO-TG hybrid nanomaterial showed excellent electrochemical performance when studied as anode for Lithium-ion battery, with an exceptionally high rate capability (capacity retention of 80% at 16 C rate) along with high discharge capacity (~ 230 mAhg-1 after 50 cycles at 0.1 C). A full cell Li-ion battery has been fabricated with TNO-TG as anode and LiNi 1/3 Mn 1/3 Co 1/3 O 2 :LiNi 0.5 Mn 0.5 O 2 (wt% of 75:25) as cathode, which delivered an average cell voltage of ~2.5 V with an initial anode-specific discharge capacity of 211 mAhg-1 , when cycled in the voltage range of 1.5-3.5 V at 0.1 C. The obtained results are very promising and we believe the current findings will lead to new directions in the ongoing search for safe and high performance anodes for rechargeable lithium-ion batteries.
Li-rich layered oxides are the most attractive cathodes for lithium-ion battery due to high capac... more Li-rich layered oxides are the most attractive cathodes for lithium-ion battery due to high capacity (>250 mAh g-1). However, its application in electric vehicles are hampered by low power density and poor cycle life. To address these, layered Li2Ru0.75Ti0.25O3 (LRTO) were synthesized and the influence of electroinactive Ti4+ on the electrochemical performance of Li2RuO3 were investigated. LRTO exhibited reversible capacity of 240 mAh g-1 under 14.3 mA g-1 with 0.11 moles of Li loss after 100 cycles compared to 0.22 moles of Li for Li2Ru0.75Sn0.25O3. More Li+ can be extracted from LRTO (0.96 moles of Li) even after 250 cycles at 143 mA g-1 than Li2RuO3 (0.79 moles of Li). High reversible Li extraction and long cycle life were attributed to structural stability of LiM2 layer in the presence of Ti4+, facilitating the lithium diffusion kinetics. The versatility of Li2MO3 structure may initiate exploration of Ti based Li-rich layered oxides for vehicular applications.
ABSTRACT We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that... more ABSTRACT We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that mimics diurnal natural daylight with the newly designed phosphor blend in the color temperature (CCT) 2700–6000 K for health benefits. Natural daylight (sunlight) spectrum possesses broad emission in the visible region and closely approximates black body radiator, with color rendition index (CRI) of 100 under wide CCT (2500–6500 K). Current white light LEDs although are efficient and durable, they are not broad enough compared to daylight. We report new phosphor blend based on Sr3MgSi2O8:Eu2+ blue phosphor with broad emission and high CRI ≥ 96 under both near UV and blue excitation. The fabricated WLED has exhibited ∼91% spectral resemblance with natural daylight compared to 39.2% for YAG:Ce3+ white LED at 4500 K. The developed phosphor blend tunes the spectrum in wider CCT and would be a prospective candidate for full spectrum daylight WLED.
ABSTRACT White light emitting alkali metal ion co-doped single host lattice phosphors Sr2.955B2O6... more ABSTRACT White light emitting alkali metal ion co-doped single host lattice phosphors Sr2.955B2O6:0.02Ce3+, 0.005Eu2+, 0.02A+ [A=Li, Na and K] were synthesized by high temperature solid state reaction. The synthesized phosphors were characterized by powder X-ray diffraction and Fourier transform infrared spectroscopic techniques. The optical properties were studied using diffuse reflectance UV-vis reflectance spectroscopy and photoluminescence (PL) spectroscopy. The role of Ce3+ as a sensitizer of Eu2+ was found from PL excitation results. The PL white light emission depends on the nature of co-doped alkali metal ion charge compensator.
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Papers by Arunkumar Paulraj