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Papers by pulak pal

Research paper thumbnail of A Silver-Based Integrated System Showing Mutually Inclusive Super Protonic Conductivity and Photoswitching Behavior

Research paper thumbnail of High Ionic Conduction and Polarity-Induced Piezoresponse in Layered Bimetallic Rb4Ag2BiBr9 Single Crystals

Research paper thumbnail of Onset of vacancy-mediated high activation energy leads to large ionic conductivity in two-dimensional layered Cs2PbI2Cl2 Ruddlesden-Popper halide perovskite

Physical Review Materials

We report the dielectric properties of a two-dimensional layered Ruddlesden-Popper halide perovsk... more We report the dielectric properties of a two-dimensional layered Ruddlesden-Popper halide perovskite Cs 2 PbI 2 Cl 2 synthesized via a simple mechanochemical process to explore fundamental aspects of ionic conduction and relaxation mechanism over a wide temperature and frequency range. Several experimental techniques, such as complex impedance spectroscopy, alternating current (AC) conductivity spectroscopy, and complex electric modulus spectroscopy, have been employed to investigate the nuances of ionic conduction and relaxation mechanisms, and the results have been corroborated using different theoretical models, such as the Maxwell-Wagner equivalent circuit model, the modified Jonscher power law, the Havrilliak-Negami (HN), and the Kohlrausch-Williams-Watts (KWW) model. The contribution of the grains and grain boundaries to the total impedance in the system is estimated by the analysis of the Nyquist plots. In temperature-dependent AC conductivity spectra, a critical temperature (413 K) is observed, beyond which the conductivity increases abruptly. This critical temperature also defines two distinct temperature ranges: the low-temperature (303-413 K) and the high-temperature (423-463 K) regimes, where the ionic transport mechanism switches from the normal ionic transport to a vacancy-mediated ionic transport mechanism. A substantially high activation energy ∼1.82 (±0.02) eV is calculated from the Arrhenius plot of the ionic conductivity in the high-temperature region, while at the low-temperature region, the activation energy is found to be ∼0.48 (±0.02) eV. The abrupt jump in the ionic conductivity beyond the critical temperature is attributed to the onset of the anionic vacancy-mediated enhanced ionic conductivity. Polaronic models have been used to interpret the AC conductivity and its power-law exponent. The activation energy obtained from ionic conductivity measurements is consistent with those calculated from relaxation time using the HN and KWW models. The presence of two master curves in time-temperature superposition scaling of AC conductivity and modulus loss spectra specifies the validity of two different conduction mechanisms.

Research paper thumbnail of Ion Transport and Segmental Dynamics in Cross-linked Poly(ethylene glycol) Diacrylate-Based Solid-like Polymer Electrolytes

The Journal of Physical Chemistry C, 2022

Research paper thumbnail of CCDC 1872174: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872172: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872171: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872170: Experimental Crystal Structure Determination

Research paper thumbnail of Ion transport and relaxation in phosphonium poly(ionic liquid) homo‐ and co‐polymers

Journal of Polymer Science, 2021

Research paper thumbnail of Three-Dimensional CsPbCl3 Perovskite Anode for Quasi-Solid-State Li -Ion and Dual-Ion Batteries: Mechanism of Li+ Conversion Process in Perovskite

Physical Review Applied, 2020

In this article, three-dimensional cubic phase CsPbCl 3 perovskite is implemented in a quasi-soli... more In this article, three-dimensional cubic phase CsPbCl 3 perovskite is implemented in a quasi-solid-state lithium-ion battery and dual-ion battery as the anode material. A half-cell lithium-ion battery developed using a gel polymer electrolyte and CsPbCl 3 anode achieves specific discharge capacities of 275.2, 362.4, 508.7 and 612.3 mA h/g at current rates of 250, 200, 100 and 50 mA/g, respectively, with an average Coulombic efficiency of 88% via the conversion process. A lithium-metal-free dual-ion battery, assembled using conventional graphite powder as a cathode and a high capacity CsPbCl 3 anode utilizing the same electrolyte, represents a potential battery concept for energy storage technologies. The operating voltage of the dual-ion battery is 0 to 4.0 V and delivers specific discharge capacities of 44.7, 59.3, 78.4 and 96.8 mA h/g at current rates of 400, 200, 100, and 50 mA/g, respectively, providing 70% Coulombic efficiency and an average voltage of 2.53 V.

Research paper thumbnail of A supramolecular hydrogel derived from a simple organic salt capable of proton conduction

Chemical Communications, 2020

The supramolecular hydrogel of a simple organic salt derived from a primary amine and a mono-sulf... more The supramolecular hydrogel of a simple organic salt derived from a primary amine and a mono-sulfonic acid displayed a proton conductivity of 1.2 × 10−4 S cm−1.

Research paper thumbnail of Robust Succinonitrile Plastic Crystal-Based Ionogel for All-Solid-State Li-Ion and Dual-Ion Batteries

ACS Applied Energy Materials, 2020

We have synthesized highly conducting and electrochemically stable solid-like ionogels based on p... more We have synthesized highly conducting and electrochemically stable solid-like ionogels based on poly(vinylidene fluoride-hexafluoropropylene) P(VdF-HFP) copolymer matrix, succinonitrile (SN) plastic crystal plasticizer, lithium trifluromethanesulfonate (LiOTf) salt and 1-butyl-1-methylpyrrolidinium trifluromethanesulfonate (BMPyrrOTf) ionic liquid. It is observed that the presence of the SN in the ionogels enhances the ionic conductivity. The composition SN/BMPyrrOTf/P(VdF-HFP) with ratio 40:40:20 (w/w) containing 0.5 M LiOTf (ionogel-3) exhibits the highest ionic conductivity (~12.18 mS cm-1) and Li +-ion transference number (~ 31%). The ionogel-3 has shown long-term stability performance in lithium plating and stripping experiments at several current densities and improved electrochemical compatibility with electrodes at 30 ºC. The Li-ion battery fabricated with the ionogel-3 has delivered high specific discharge capacities of 86, 120, 139, 144, and 150 mAh g-1 at current densities of C/3, C/5, C/8, C/10, and C/12 respectively at 30 C. The fabricated Li-graphite dualion battery has also delivered high specific discharge capacities of 126, 89 and 51 mAh g-1 at 100, 300 and 500 mA g-1 current densities respectively maintaining high average discharge voltage of  4.5 V.

Research paper thumbnail of A Silver-Based Integrated System Showing Mutually Inclusive Super Protonic Conductivity and Photoswitching Behavior

Research paper thumbnail of High Ionic Conduction and Polarity-Induced Piezoresponse in Layered Bimetallic Rb4Ag2BiBr9 Single Crystals

Research paper thumbnail of Onset of vacancy-mediated high activation energy leads to large ionic conductivity in two-dimensional layered Cs2PbI2Cl2 Ruddlesden-Popper halide perovskite

Physical Review Materials

We report the dielectric properties of a two-dimensional layered Ruddlesden-Popper halide perovsk... more We report the dielectric properties of a two-dimensional layered Ruddlesden-Popper halide perovskite Cs 2 PbI 2 Cl 2 synthesized via a simple mechanochemical process to explore fundamental aspects of ionic conduction and relaxation mechanism over a wide temperature and frequency range. Several experimental techniques, such as complex impedance spectroscopy, alternating current (AC) conductivity spectroscopy, and complex electric modulus spectroscopy, have been employed to investigate the nuances of ionic conduction and relaxation mechanisms, and the results have been corroborated using different theoretical models, such as the Maxwell-Wagner equivalent circuit model, the modified Jonscher power law, the Havrilliak-Negami (HN), and the Kohlrausch-Williams-Watts (KWW) model. The contribution of the grains and grain boundaries to the total impedance in the system is estimated by the analysis of the Nyquist plots. In temperature-dependent AC conductivity spectra, a critical temperature (413 K) is observed, beyond which the conductivity increases abruptly. This critical temperature also defines two distinct temperature ranges: the low-temperature (303-413 K) and the high-temperature (423-463 K) regimes, where the ionic transport mechanism switches from the normal ionic transport to a vacancy-mediated ionic transport mechanism. A substantially high activation energy ∼1.82 (±0.02) eV is calculated from the Arrhenius plot of the ionic conductivity in the high-temperature region, while at the low-temperature region, the activation energy is found to be ∼0.48 (±0.02) eV. The abrupt jump in the ionic conductivity beyond the critical temperature is attributed to the onset of the anionic vacancy-mediated enhanced ionic conductivity. Polaronic models have been used to interpret the AC conductivity and its power-law exponent. The activation energy obtained from ionic conductivity measurements is consistent with those calculated from relaxation time using the HN and KWW models. The presence of two master curves in time-temperature superposition scaling of AC conductivity and modulus loss spectra specifies the validity of two different conduction mechanisms.

Research paper thumbnail of Ion Transport and Segmental Dynamics in Cross-linked Poly(ethylene glycol) Diacrylate-Based Solid-like Polymer Electrolytes

The Journal of Physical Chemistry C, 2022

Research paper thumbnail of CCDC 1872174: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872172: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872171: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1872170: Experimental Crystal Structure Determination

Research paper thumbnail of Ion transport and relaxation in phosphonium poly(ionic liquid) homo‐ and co‐polymers

Journal of Polymer Science, 2021

Research paper thumbnail of Three-Dimensional CsPbCl3 Perovskite Anode for Quasi-Solid-State Li -Ion and Dual-Ion Batteries: Mechanism of Li+ Conversion Process in Perovskite

Physical Review Applied, 2020

In this article, three-dimensional cubic phase CsPbCl 3 perovskite is implemented in a quasi-soli... more In this article, three-dimensional cubic phase CsPbCl 3 perovskite is implemented in a quasi-solid-state lithium-ion battery and dual-ion battery as the anode material. A half-cell lithium-ion battery developed using a gel polymer electrolyte and CsPbCl 3 anode achieves specific discharge capacities of 275.2, 362.4, 508.7 and 612.3 mA h/g at current rates of 250, 200, 100 and 50 mA/g, respectively, with an average Coulombic efficiency of 88% via the conversion process. A lithium-metal-free dual-ion battery, assembled using conventional graphite powder as a cathode and a high capacity CsPbCl 3 anode utilizing the same electrolyte, represents a potential battery concept for energy storage technologies. The operating voltage of the dual-ion battery is 0 to 4.0 V and delivers specific discharge capacities of 44.7, 59.3, 78.4 and 96.8 mA h/g at current rates of 400, 200, 100, and 50 mA/g, respectively, providing 70% Coulombic efficiency and an average voltage of 2.53 V.

Research paper thumbnail of A supramolecular hydrogel derived from a simple organic salt capable of proton conduction

Chemical Communications, 2020

The supramolecular hydrogel of a simple organic salt derived from a primary amine and a mono-sulf... more The supramolecular hydrogel of a simple organic salt derived from a primary amine and a mono-sulfonic acid displayed a proton conductivity of 1.2 × 10−4 S cm−1.

Research paper thumbnail of Robust Succinonitrile Plastic Crystal-Based Ionogel for All-Solid-State Li-Ion and Dual-Ion Batteries

ACS Applied Energy Materials, 2020

We have synthesized highly conducting and electrochemically stable solid-like ionogels based on p... more We have synthesized highly conducting and electrochemically stable solid-like ionogels based on poly(vinylidene fluoride-hexafluoropropylene) P(VdF-HFP) copolymer matrix, succinonitrile (SN) plastic crystal plasticizer, lithium trifluromethanesulfonate (LiOTf) salt and 1-butyl-1-methylpyrrolidinium trifluromethanesulfonate (BMPyrrOTf) ionic liquid. It is observed that the presence of the SN in the ionogels enhances the ionic conductivity. The composition SN/BMPyrrOTf/P(VdF-HFP) with ratio 40:40:20 (w/w) containing 0.5 M LiOTf (ionogel-3) exhibits the highest ionic conductivity (~12.18 mS cm-1) and Li +-ion transference number (~ 31%). The ionogel-3 has shown long-term stability performance in lithium plating and stripping experiments at several current densities and improved electrochemical compatibility with electrodes at 30 ºC. The Li-ion battery fabricated with the ionogel-3 has delivered high specific discharge capacities of 86, 120, 139, 144, and 150 mAh g-1 at current densities of C/3, C/5, C/8, C/10, and C/12 respectively at 30 C. The fabricated Li-graphite dualion battery has also delivered high specific discharge capacities of 126, 89 and 51 mAh g-1 at 100, 300 and 500 mA g-1 current densities respectively maintaining high average discharge voltage of  4.5 V.