Earth abundant Fe and Mn based novel P3-type Na-ion layered oxide cathode material with sufficien... more Earth abundant Fe and Mn based novel P3-type Na-ion layered oxide cathode material with sufficient Na content for full cell application.
A tricarboxylate‐based organic compound for Na storage at low voltage, trisodium‐1,3,5‐benzene tr... more A tricarboxylate‐based organic compound for Na storage at low voltage, trisodium‐1,3,5‐benzene tricarboxylate (Na3BTC) is reported. The effect of increasing the number of carboxyl redox active groups on the aromatic system versus previously reported dicarboxylate‐based Na electrodes is explored. Sodiation and desodiation of this material occur at average voltages of 0.4 and 0.5 V, respectively, suitable for anode application. The galvanostatic profile of desodiation consists of two plateaus at 0.5 and 0.2 V. The material delivers a capacity of 250 mAh g−1 at a C/5 rate, with a retention of 80% after 100 cycles. It also has an excellent rate capability, delivering 100 mAh g−1 with a 75% retention after 1500 cycles at a 10 C rate. Ex situ attenuated total reflection Fourier‐transform infrared spectroscopy (ATR‐FTIR), ex situ 1H NMR studies, and first principles calculations are performed to understand the sodium storage mechanism. The mechanism is found to be different from those pre...
Journal of the American Ceramic Society, Jun 12, 2006
The synthesis and densification of fairly dense nanocrystalline SrTiO3 and its characterization a... more The synthesis and densification of fairly dense nanocrystalline SrTiO3 and its characterization are described in this paper in detail. Significant grain growth was avoided by the application of a two‐stage sintering process using hot pressing. High‐resolution transmission electron microscopy and electron energy loss spectroscopy characterizations indicate pure material with no detectable chemical inhomogeneities. The electrical measurements indicate the disappearance of bulk contribution to the electrical conduction due to the overlap of depleted space charge layers if the grain size is below 100 nm. Owing to the overlap, the capacitance appears as bulk‐like rather than due to space charge polarization. Non‐contact sub‐millimeter optical spectroscopy measurements reveal strong suppression of the dielectric constant values at low temperature.
Journal of The Electrochemical Society, Aug 1, 2022
In this manuscript, the impact of operating conditions such as voltage window, and operating temp... more In this manuscript, the impact of operating conditions such as voltage window, and operating temperature on electrochemical performance and cycle life of Zn-substituted Na3.2V1.8Zn0.2(PO4)3 (NVZP) vs hard carbon (HC) coin cells filled with 1 mol dm−3 NaBF4 in tetraglyme is presented. Initially, the cells are cycled for 500 times at C/2 charge and 1 C discharge in three different voltage windows (4.20–1.00 V, 4.05–1.00 V and 4.05–1.50 V) and at two temperatures (28 °C and 40 °C) and are subjected to periodic internal resistance and impedance measurements. The elemental composition of the electrodes harvested after cycling reveals that vanadium dissolution with accompanying deposition on the HC electrode and irreversible loss of sodium causes increased cell impedance. The identified degradation mechanisms, which causes severe capacity fade, are found to be accelerated in the cells cycled over wider voltage windows, particularly at elevated temperature. The best cycling performance and lowest impedance are recorded for the cells cycled within 4.05–1.50 V at 28 °C owing to negligible vanadium dissolution. Under these optimized testing conditions, a prototype 18650 cell, shows impressive capacity retention of 77% after 1000 cycles.
Earth abundant Fe and Mn based novel P3-type Na-ion layered oxide cathode material with sufficien... more Earth abundant Fe and Mn based novel P3-type Na-ion layered oxide cathode material with sufficient Na content for full cell application.
A tricarboxylate‐based organic compound for Na storage at low voltage, trisodium‐1,3,5‐benzene tr... more A tricarboxylate‐based organic compound for Na storage at low voltage, trisodium‐1,3,5‐benzene tricarboxylate (Na3BTC) is reported. The effect of increasing the number of carboxyl redox active groups on the aromatic system versus previously reported dicarboxylate‐based Na electrodes is explored. Sodiation and desodiation of this material occur at average voltages of 0.4 and 0.5 V, respectively, suitable for anode application. The galvanostatic profile of desodiation consists of two plateaus at 0.5 and 0.2 V. The material delivers a capacity of 250 mAh g−1 at a C/5 rate, with a retention of 80% after 100 cycles. It also has an excellent rate capability, delivering 100 mAh g−1 with a 75% retention after 1500 cycles at a 10 C rate. Ex situ attenuated total reflection Fourier‐transform infrared spectroscopy (ATR‐FTIR), ex situ 1H NMR studies, and first principles calculations are performed to understand the sodium storage mechanism. The mechanism is found to be different from those pre...
Journal of the American Ceramic Society, Jun 12, 2006
The synthesis and densification of fairly dense nanocrystalline SrTiO3 and its characterization a... more The synthesis and densification of fairly dense nanocrystalline SrTiO3 and its characterization are described in this paper in detail. Significant grain growth was avoided by the application of a two‐stage sintering process using hot pressing. High‐resolution transmission electron microscopy and electron energy loss spectroscopy characterizations indicate pure material with no detectable chemical inhomogeneities. The electrical measurements indicate the disappearance of bulk contribution to the electrical conduction due to the overlap of depleted space charge layers if the grain size is below 100 nm. Owing to the overlap, the capacitance appears as bulk‐like rather than due to space charge polarization. Non‐contact sub‐millimeter optical spectroscopy measurements reveal strong suppression of the dielectric constant values at low temperature.
Journal of The Electrochemical Society, Aug 1, 2022
In this manuscript, the impact of operating conditions such as voltage window, and operating temp... more In this manuscript, the impact of operating conditions such as voltage window, and operating temperature on electrochemical performance and cycle life of Zn-substituted Na3.2V1.8Zn0.2(PO4)3 (NVZP) vs hard carbon (HC) coin cells filled with 1 mol dm−3 NaBF4 in tetraglyme is presented. Initially, the cells are cycled for 500 times at C/2 charge and 1 C discharge in three different voltage windows (4.20–1.00 V, 4.05–1.00 V and 4.05–1.50 V) and at two temperatures (28 °C and 40 °C) and are subjected to periodic internal resistance and impedance measurements. The elemental composition of the electrodes harvested after cycling reveals that vanadium dissolution with accompanying deposition on the HC electrode and irreversible loss of sodium causes increased cell impedance. The identified degradation mechanisms, which causes severe capacity fade, are found to be accelerated in the cells cycled over wider voltage windows, particularly at elevated temperature. The best cycling performance and lowest impedance are recorded for the cells cycled within 4.05–1.50 V at 28 °C owing to negligible vanadium dissolution. Under these optimized testing conditions, a prototype 18650 cell, shows impressive capacity retention of 77% after 1000 cycles.
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Papers by Palani Balaya