H. Nithya, S. Selvasekarapandian, D. Arun Kumar, A. Sakunthala, M. Hema, J. Kawamura, R. Baskaran... more H. Nithya, S. Selvasekarapandian, D. Arun Kumar, A. Sakunthala, M. Hema, J. Kawamura, R. Baskaran, P. Christopher Selvin DRDO – BU, Center for Life Sciences, Bharathiar University, Coimbatore, Tamil Nadu, India Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, India Kalasalingam University, Krishnankoil, Srivilliputhur, Tamil Nadu, India Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan Department of Physics, NGM College, Pollachi, Tamil Nadu, India
Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysi... more Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysis. The resultant particles had well-developed facet planes in a transmission electron microscopy (TEM) image and electron diffraction pattern from a single particle also showed clear diffraction spots, indicating that the prepared particles were highly crystalline. The mean crystallite size estimated from X-ray diffraction peaks was ca. 18 nm, which was in good agreement with the diameter of the particles observed in the TEM image. These particles were gathered on platinum mesh and their electrochemical properties were investigated. The mean crystallite size increased with an increase in annealing temperature, which influenced the electrochemical lithium insertion/extraction properties of the particles. In particular, samples annealed at 773 K showed different kinds of lithium extraction/insertion properties in the cyclic voltammogram (CV), and only a couple of broad redox peaks were observed at around 0.8 V (versus Ag/AgCl) between 0.4 and 1.0 V. It is suggested that lithium distribute randomly in the sample annealed at 773 K sample due to the effects of grain boundaries, which resulted in different kinds of phase transition reactions.
Diffusion coefficient of lithium ions in Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) single crystal is... more Diffusion coefficient of lithium ions in Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) single crystal is measured using 7 Li pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy in the temperature range from 298 K to 353 K. The Li diffusion coefficient in LLZTO is evaluated to be 1.9 × 10 −13 m 2 s −1 at 298 K with the activation energy of 0.43 eV. The ionic conductivity of LLZTO single crystal is measured by impedance spectroscopy, which gives 7 × 10 −4 S cm −1 at 298 K with the activation energy of 0.43 eV. The diffusion coefficient obtained by PFG-NMR is lesser than the diffusion coefficient calculated from ionic conductivity using Nernst-Einstein relation. The small discrepancy gives the Haven ratio of 0.4, which suggests a correlated migration of the lithium ions in the tetrahedral and octahedral sites in LLZTO. To compare the present result with previous reports, the diffusion time (Δ) dependence is carefully checked in PFG-NMR not only for the single crystal but also the crushed powdered samples, which revealed no significant dependence in the single crystal but small dependence in the crushed samples which may be due to the restricted diffusion in the powder grains.
1． Introduction Thin-film solid-state batteries have attracted attention due to their low risk of... more 1． Introduction Thin-film solid-state batteries have attracted attention due to their low risk of fire and explosion, reduced environmental impact, and high energy density. Amorphous lithium phosphate (a-Li3PO4) is used as a solid electrolyte for thin-film batteries because of its wide electrochemical window and negligible interface resistance. Lithium diffusion is an important factor affecting the characteristics of solid-state batteries. However, the technique for measuring lithium self-diffusion in solid-state batteries is limited because the lifetime of lithium radioactive isotope, 8Li, is too short to measure the diffusion coefficient. Stable isotopes, 6Li and 7Li, are applied to measure the trace diffusion of lithium. Secondary ion mass spectrometry (SIMS) is useful as it is able to distinguish the isotopes of 6Li and 7Li. In this study, we intended to measure the tracer diffusion coefficient of lithium (D* Li) directly using secondary ion mass spectrometry (SIMS) with isotope...
AC conductivity σ(ω) of single crystals of Ag β-alumina and Na β-alumina has been studied in the ... more AC conductivity σ(ω) of single crystals of Ag β-alumina and Na β-alumina has been studied in the temperature range from approximately 100 K to room temperature. The DC regime of σ(ω), which had a close relation to the ion dynamics for the long-range diffusion, was found to have the small power-law dependence σ(ω) ∝ ω n with frequency exponent n = 0.11-0.15, not σ(ω) ∝ ω 0 = const. In higher frequencies, the σ(ω) was monotonically increasing with Log-frequency and was put into Jonscher's universal law (σ(ω) ∝ ω 0.6). The β-alumina is an ideal two-dimensional super ionic conductor. Its low-dimensionality and the scaling theory for a random walk enable us to understand the small power-law dependence of ionic conductivity. We suggested that a "scaleinvariance" would hold true behind the super ionic conduction in the self-similarity point of view.
New organic-inorganic hybrid superionic conductor glasses were developed, which consisted of silv... more New organic-inorganic hybrid superionic conductor glasses were developed, which consisted of silver iodide (AgI) and alkylbis-trimethylammonium diiodides. The glasses were prepared from low-temperature molten salts of them by melt quenching method, which were confirmed in glassy state by X-ray diffraction (XRD), DSC and optical microscope observation. The ionic conductivity of these glasses are about 10 22 V 21 cm 21 at room temperature which is the best in the organicinorganic hybrid superionic conductor glasses obtained so far. Ag-109 NMR spectra of the glasses showed a motionally narrowed peak at about 800 ppm regardless of their compositions, which is almost equal to the value of AgI crystals. These results are in good agreement with the prediction of the percolation model, where the silver cations are assumed to diffuse through the conduction channels of face-sharing iodide tetrahedra, which are randomly blocked by organic substances.
We have developed a nanoscale diffusion measurement method using an α-emitting radioactive 8Li tr... more We have developed a nanoscale diffusion measurement method using an α-emitting radioactive 8Li tracer. In this method, while implanting a pulsed 8 keV 8Li beam, the α particles emitted at a small angle (10°) relative to the sample surface were detected as a function of time. The method has been successfully applied to measuring lithium diffusion coefficients for an amorphous Li4SiO4–Li3VO4 (LVSO) thin film with a thickness of several hundred nanometers, demonstrating that the present method is sensitive to diffusion coefficients down on the order of 10−12 cm2/s, which is more sensitive by about two orders of magnitude than that previously achieved.
All solid-state thin film batteries consisting of an amorphous Li-V-Si-O (LVSO) solid electrolyte... more All solid-state thin film batteries consisting of an amorphous Li-V-Si-O (LVSO) solid electrolyte, layered rocksalt LiCoO 2 and spinel phase LiMn 2 O 4 cathodes, and amorphous SnO anode were fabricated only by sequential pulsed laser deposition (PLD) technique. The crystal structure of the cathode films was characterized by XRD. The post-annealed cathode films exhibit the characteristic crystal structures while as-deposited cathode films are amorphous or partially crystallized. The rough surface is observed for the post-annealed films. The thin-film battery was characterized by a FE-SEM, charge-discharge measurements and cyclic voltammmetry. As well as the LiCoO 2 , the new cathode film of LiMn 2 O 4 can be utilized for allsolid-state batteries, and their electrochemical properties are reported. The capacities of the thin-film batteries with annealed cathode films are 10 times larger than that of the as-deposited films. The as-deposited film shows a very low capacity even in the liquid electrolyte cell system.
The correlation between the ionic conductivity and the nano-crystallization processes of (CuI) x-... more The correlation between the ionic conductivity and the nano-crystallization processes of (CuI) x-(Cu 2 MoO 4) 1−x superionic conducting glasses has been systematically investigated by X-ray diffraction and high-resolution transmission electron microscopy (HREM). In x = 0.52, CuI crystal precipitates as a primary phase. On the other hand, in x = 0.40, crystallization from homogeneous glass into CuI crystal and other phase has been observed. Nano-crystallization processes depend on CuI content. The difference of the nano-crystallization processes influences the electrical conductivity.
ABSTRACT Solid polymer proton conductors comprising of poly(vinyl alcohol), ammonium acetate and ... more ABSTRACT Solid polymer proton conductors comprising of poly(vinyl alcohol), ammonium acetate and water have been prepared by solution cast method for different NH4+/OH− ratios. The XRD spectra for the electrolyte indicate that the amorphous nature of PVA increases with the concentration of ammonium acetate. The DSC curves show the low glass transition temperature for the ratio (NH4+/OH−)=0.25 which relates to higher conductivity of the sample. The ionic conductivity at room temperature depends strongly on NH4+/OH− ratios. The variation of electrical conductivity with temperature showed two regions of activation above and below glass transition temperature. The optical absorption studies show the similar trend for pure PVA and salt-doped PVA with different absorption intensity. The direct and indirect band gap energy is observed to be constant for pure PVA and salt-doped PVA samples and found to be 5.4eV and 4.8eV, respectively. The dc polarization measurement shows that the conductivity is mainly due to ions.
H. Nithya, S. Selvasekarapandian, D. Arun Kumar, A. Sakunthala, M. Hema, J. Kawamura, R. Baskaran... more H. Nithya, S. Selvasekarapandian, D. Arun Kumar, A. Sakunthala, M. Hema, J. Kawamura, R. Baskaran, P. Christopher Selvin DRDO – BU, Center for Life Sciences, Bharathiar University, Coimbatore, Tamil Nadu, India Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, India Kalasalingam University, Krishnankoil, Srivilliputhur, Tamil Nadu, India Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan Department of Physics, NGM College, Pollachi, Tamil Nadu, India
Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysi... more Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysis. The resultant particles had well-developed facet planes in a transmission electron microscopy (TEM) image and electron diffraction pattern from a single particle also showed clear diffraction spots, indicating that the prepared particles were highly crystalline. The mean crystallite size estimated from X-ray diffraction peaks was ca. 18 nm, which was in good agreement with the diameter of the particles observed in the TEM image. These particles were gathered on platinum mesh and their electrochemical properties were investigated. The mean crystallite size increased with an increase in annealing temperature, which influenced the electrochemical lithium insertion/extraction properties of the particles. In particular, samples annealed at 773 K showed different kinds of lithium extraction/insertion properties in the cyclic voltammogram (CV), and only a couple of broad redox peaks were observed at around 0.8 V (versus Ag/AgCl) between 0.4 and 1.0 V. It is suggested that lithium distribute randomly in the sample annealed at 773 K sample due to the effects of grain boundaries, which resulted in different kinds of phase transition reactions.
Diffusion coefficient of lithium ions in Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) single crystal is... more Diffusion coefficient of lithium ions in Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) single crystal is measured using 7 Li pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy in the temperature range from 298 K to 353 K. The Li diffusion coefficient in LLZTO is evaluated to be 1.9 × 10 −13 m 2 s −1 at 298 K with the activation energy of 0.43 eV. The ionic conductivity of LLZTO single crystal is measured by impedance spectroscopy, which gives 7 × 10 −4 S cm −1 at 298 K with the activation energy of 0.43 eV. The diffusion coefficient obtained by PFG-NMR is lesser than the diffusion coefficient calculated from ionic conductivity using Nernst-Einstein relation. The small discrepancy gives the Haven ratio of 0.4, which suggests a correlated migration of the lithium ions in the tetrahedral and octahedral sites in LLZTO. To compare the present result with previous reports, the diffusion time (Δ) dependence is carefully checked in PFG-NMR not only for the single crystal but also the crushed powdered samples, which revealed no significant dependence in the single crystal but small dependence in the crushed samples which may be due to the restricted diffusion in the powder grains.
1． Introduction Thin-film solid-state batteries have attracted attention due to their low risk of... more 1． Introduction Thin-film solid-state batteries have attracted attention due to their low risk of fire and explosion, reduced environmental impact, and high energy density. Amorphous lithium phosphate (a-Li3PO4) is used as a solid electrolyte for thin-film batteries because of its wide electrochemical window and negligible interface resistance. Lithium diffusion is an important factor affecting the characteristics of solid-state batteries. However, the technique for measuring lithium self-diffusion in solid-state batteries is limited because the lifetime of lithium radioactive isotope, 8Li, is too short to measure the diffusion coefficient. Stable isotopes, 6Li and 7Li, are applied to measure the trace diffusion of lithium. Secondary ion mass spectrometry (SIMS) is useful as it is able to distinguish the isotopes of 6Li and 7Li. In this study, we intended to measure the tracer diffusion coefficient of lithium (D* Li) directly using secondary ion mass spectrometry (SIMS) with isotope...
AC conductivity σ(ω) of single crystals of Ag β-alumina and Na β-alumina has been studied in the ... more AC conductivity σ(ω) of single crystals of Ag β-alumina and Na β-alumina has been studied in the temperature range from approximately 100 K to room temperature. The DC regime of σ(ω), which had a close relation to the ion dynamics for the long-range diffusion, was found to have the small power-law dependence σ(ω) ∝ ω n with frequency exponent n = 0.11-0.15, not σ(ω) ∝ ω 0 = const. In higher frequencies, the σ(ω) was monotonically increasing with Log-frequency and was put into Jonscher's universal law (σ(ω) ∝ ω 0.6). The β-alumina is an ideal two-dimensional super ionic conductor. Its low-dimensionality and the scaling theory for a random walk enable us to understand the small power-law dependence of ionic conductivity. We suggested that a "scaleinvariance" would hold true behind the super ionic conduction in the self-similarity point of view.
New organic-inorganic hybrid superionic conductor glasses were developed, which consisted of silv... more New organic-inorganic hybrid superionic conductor glasses were developed, which consisted of silver iodide (AgI) and alkylbis-trimethylammonium diiodides. The glasses were prepared from low-temperature molten salts of them by melt quenching method, which were confirmed in glassy state by X-ray diffraction (XRD), DSC and optical microscope observation. The ionic conductivity of these glasses are about 10 22 V 21 cm 21 at room temperature which is the best in the organicinorganic hybrid superionic conductor glasses obtained so far. Ag-109 NMR spectra of the glasses showed a motionally narrowed peak at about 800 ppm regardless of their compositions, which is almost equal to the value of AgI crystals. These results are in good agreement with the prediction of the percolation model, where the silver cations are assumed to diffuse through the conduction channels of face-sharing iodide tetrahedra, which are randomly blocked by organic substances.
We have developed a nanoscale diffusion measurement method using an α-emitting radioactive 8Li tr... more We have developed a nanoscale diffusion measurement method using an α-emitting radioactive 8Li tracer. In this method, while implanting a pulsed 8 keV 8Li beam, the α particles emitted at a small angle (10°) relative to the sample surface were detected as a function of time. The method has been successfully applied to measuring lithium diffusion coefficients for an amorphous Li4SiO4–Li3VO4 (LVSO) thin film with a thickness of several hundred nanometers, demonstrating that the present method is sensitive to diffusion coefficients down on the order of 10−12 cm2/s, which is more sensitive by about two orders of magnitude than that previously achieved.
All solid-state thin film batteries consisting of an amorphous Li-V-Si-O (LVSO) solid electrolyte... more All solid-state thin film batteries consisting of an amorphous Li-V-Si-O (LVSO) solid electrolyte, layered rocksalt LiCoO 2 and spinel phase LiMn 2 O 4 cathodes, and amorphous SnO anode were fabricated only by sequential pulsed laser deposition (PLD) technique. The crystal structure of the cathode films was characterized by XRD. The post-annealed cathode films exhibit the characteristic crystal structures while as-deposited cathode films are amorphous or partially crystallized. The rough surface is observed for the post-annealed films. The thin-film battery was characterized by a FE-SEM, charge-discharge measurements and cyclic voltammmetry. As well as the LiCoO 2 , the new cathode film of LiMn 2 O 4 can be utilized for allsolid-state batteries, and their electrochemical properties are reported. The capacities of the thin-film batteries with annealed cathode films are 10 times larger than that of the as-deposited films. The as-deposited film shows a very low capacity even in the liquid electrolyte cell system.
The correlation between the ionic conductivity and the nano-crystallization processes of (CuI) x-... more The correlation between the ionic conductivity and the nano-crystallization processes of (CuI) x-(Cu 2 MoO 4) 1−x superionic conducting glasses has been systematically investigated by X-ray diffraction and high-resolution transmission electron microscopy (HREM). In x = 0.52, CuI crystal precipitates as a primary phase. On the other hand, in x = 0.40, crystallization from homogeneous glass into CuI crystal and other phase has been observed. Nano-crystallization processes depend on CuI content. The difference of the nano-crystallization processes influences the electrical conductivity.
ABSTRACT Solid polymer proton conductors comprising of poly(vinyl alcohol), ammonium acetate and ... more ABSTRACT Solid polymer proton conductors comprising of poly(vinyl alcohol), ammonium acetate and water have been prepared by solution cast method for different NH4+/OH− ratios. The XRD spectra for the electrolyte indicate that the amorphous nature of PVA increases with the concentration of ammonium acetate. The DSC curves show the low glass transition temperature for the ratio (NH4+/OH−)=0.25 which relates to higher conductivity of the sample. The ionic conductivity at room temperature depends strongly on NH4+/OH− ratios. The variation of electrical conductivity with temperature showed two regions of activation above and below glass transition temperature. The optical absorption studies show the similar trend for pure PVA and salt-doped PVA with different absorption intensity. The direct and indirect band gap energy is observed to be constant for pure PVA and salt-doped PVA samples and found to be 5.4eV and 4.8eV, respectively. The dc polarization measurement shows that the conductivity is mainly due to ions.
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