Department of Physics
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Item New generation Li+ NASICON glass-ceramics for solid state Li+ ion battery applications(AIP, 2018-04) Dalvi, AnshumanLithiumion conducting NASICON glass-ceramics have been prepared by a novel planetary ball milling assisted synthesis route. Structural, thermal and electrical investigations have been carried out on the novel composites composed of LiTi(PO4)3 (LTP) and 50[Li2SO4]-50[Li2O-P2O5] ionic glass reveal interesting results. Composites were prepared keeping the concentration of the ionic glass fixed at 20 wt%. X-ray diffraction and diffe rential thermal analysis confirm the glass-ceramic formation. Moreover, the structure of LTP remains intact during the glass -ceramic formation. Electrical conductivity of the glass-ceramic composite is found to be higher than that of the pristine glass (50LSLP) and LTP. The bulk and grain boundary conductivities of LTP exhibit improvement in composite. Owing to high ionic conductivity and thermal stability, novel glass -ceramic seems to be a promising candidate for all solid-state battery applications.Item Novel hybrid composites NaCF3SO3–PEO–NASICON for sodium ion battery applications(AIP, 2019-07) Dalvi, AnshumanNa+ ion based hybrid solid polymer electrolyte with high ionic conductivity and appreciable electrochemical stability has been reported. Addition of nano NASICON ceramic fillers [NaTi2(PO4)3] in polymer electrolyte matrix leads to significant ionic conductivity enhancement. These composites have been prepared in wide composition range and exhibit thermal stability at least upto 100°C for compositions with large amount of NASICONs. A maximum ionic conductivity of 3×10−5 Ω−1cm−1 is obtained at 40°C for a typical composition 10NaCF3SO390[0.7NTP0.3PEO]. The hybrid polymer composites are potential candidates for Na+ ion based solid-state battery applicationsItem Electrical, structural and thermal characterization of Cu2O substituted AgI–(Cu2O)x (Ag2O)1 − x–V2O5 glassy superionic system(Elsevier, 2012-10) Dalvi, AnshumanEffect of Cu2O substitution in 50AgI–33.33[(Cu2O)x (Ag2O)1 − x]–16.67V2O5 glass matrix is discussed. Glassy nature of the samples is confirmed by differential scanning calorimetry and X-ray diffraction. The electrical conductivity of these samples is found to be increasing with Cu2O content and approaches a maximum value of ~ 2 × 10− 2 Ω− 1 cm− 1 for x = 0.3 at room temperature. Ionic mobility, measured using transient ionic current technique, increases with Cu2O content significantly. These samples are found to be predominantly Ag+ ion conducting in nature. High Cu2O content samples (x ≥ 0.3) though exhibit nanocomposite nature as revealed by scanning electron microscopy, the conductivity enhancement is found to be due to compositional changes that eventually lead to ionic mobility rise.Item Electrical Characterization of PVA-MgSO4 and PVA-Li2SO4 Polymer Salt Composite Electrolytes(Elsevier, 2019) Dalvi, AnshumanPolymer composite films of two types have been prepared by dissolving (i) MgSO4 and (ii) Li2SO4 in polyvinyl alcohol (PVA) matrix. Electrical conductivity exhibits enhancement with salt addition. Preliminary studies suggest that salt ions contribute to electrical transport. In case of PVA:[MgSO4], upto 10 wt % of salt could be dissolved in the polymer matrix. Whereas, in case of PVA:[Li2SO4] free standing composite films can be formed at least with ∼ 20 wt % of salt. Composite films have been found to be partially crystalline in nature and may be useful for Li+/Mg+ ion battery applicationsItem Preparation and characterization of novel solid electrolytes based on [EMIM] BF4 and lithium nitrate confined silica gels(Elsevier, 2019-11) Sivasubramanian, S.C.; Dalvi, AnshumanNovel ionic liquid ([EMIM]BF4) and lithium nitrate confined silica gel composites have been prepared via hydrolytic sol-gel process and found to exhibit electrical conductivity up to 10−4 Ω−1cm−1 in the temperature range 150–300 °C. The composites are thermally stable at this temperature range and measurements are repeatable. Powder X-ray diffraction patterns suggest that the composites are amorphous in nature. FE-SEM (EDS elemental mapping) and DSC measurements further confirm IL confinement in the matrix. Electrical conductivity (150–300 °C) has been studied as a function of IL and Li+ ion content. The samples with no IL content are essentially electronic in nature. Addition of IL in small amounts (1 mol%) enhances the total conductivity at least by an order of magnitude. Further addition of salt (LiNO3) enhances ionic transport by orders of magnitude. The electronic conductivity and ionic mobility along with OCV measurements on cells of type Li/composite/LiCoO2 suggests facilitation of Li+ ion transport in presence of IL in small amount. However, further increasing the content of IL in the composition while keeping the salt ion concentration same, does not improve conductivity, rather reduces it. This complex behavior may be due to possibility of Li+ ions forming complex with IL anion and further investigations are required in this regard. Preliminary findings suggest that these materials have good potential for their applications in all-solid-state supercapacitors.Item Structural and electrical transport studies in CuI substituted AgI-oxysalt glass-ceramic nanocomposites formed during crystallization(NISCAIR, 2013-05) Dalvi, AnshumanElectrical transport in CuIxAgI1-x-Ag2O-V2O5 glassy system has been studied for temperatures Tg ≤ T ≤ Tc. The XRD and DSC results suggest multiple crystallizations in this system. The electrical conductivity-temperature cycles are obtained for all the compositions and the conductivity behaviour for T ≥ Tc is explained using a crystallite by pass model.Item Crystallization in Li2SO4–Li2O–P2O5 glassy ionic system: An assessment through electrical transport(Elsevier, 2014-10) Dalvi, AnshumanThe electrical transport during the crystallization of ternary Li2SO4–Li2O–P2O5 glassy ionic system reveals interesting results. Electrical conductivity isotherms recorded at the crystallization temperature are found to be of immense importance, especially, in the understanding of phase transformation. The electrical conductivity falls rapidly during crystallization of LiPO3 compound and saturates at its completion. Such studies on conductivity isotherms further confirm the suppression of crystallization with addition of Li2SO4 in the glass matrix. A systematic variation of the Cole–Cole plots and conductivity spectra during crystallization further suggests a slow and predetermined process of glass–ceramic formation. The mechanism of electrical transport during crystallization is also explained using a crystallite bypass model. It is further revealed that the samples remain purely ionic during and after crystallization.Item Electrical transport in Li2SO4-Li2O-B2O3 glass-ceramic composites(NISCAIR, 2013-05) Dalvi, AnshumanLithium ion conducting glass-ceramic composites have been synthesized in Li2SO4-Li2O-B2O3 system by annealing the glass above its crystallization temperature. The electrical, structural and thermal characterization of these glass-ceramics reveals interesting results. The conductivity of the glass-ceramic increases with Li2SO4 content and exhibits a maximum of ~ 10-4 at 200°CItem Li+-NASICON crystallites in PEO-LiCF3SO3 matrix: Characterization of a novel hybrid electrolyte(Elsevier, 2017-11) Dalvi, AnshumanStructural, thermal and electrical transport in PEO-LiCF3SO3 solid polymer electrolyte dispersed with Li+-NASICON crystallites has been assessed. Fine submicron crystallites of LiTi2(PO4)3 (LTP) were added in appropriate amount during solution casting of the polymer films. Thus the compositions 95[PEO1 − x-LTPx]-5LiCF3SO3 have been synthesized for a wide range of LTP content (x = 0–0.9). Electrical conductivity increases with LTP content monotonically. Highest room temperature conductivity of ~ 7 × 10− 5 Ω− 1 cm− 1 has been obtained for the sample with x = 0.9 of LTP which is ~ 43 times higher than that of the sample with no LTP content. FE-SEM investigations performed on pellets with higher LTP content suggest uniform distribution of LTP particles in the polymer matrix. Preliminary investigations reveal that mechanism of electrical transport in SPE-LTP hybrid composites is greatly influenced by LTP content.Item Ionic liquid dispersed Li+ ion oxide glasses and glass-ceramics: Assessment of electrical transport and thermal stability(Elsevier, 2015) Dalvi, AnshumanEffect of ionic liquid (BMIM BF4) dispersion on Li+ ion oxide glass and glass-ceramics has been investigated. Addition of ionic liquid in a very small amount (0.5–5 wt.%) enhances the ionic conductivity significantly. For a typical glass composition 60Li2SO4-40(0.5Li2O–0.5P2O5), with grain size of ~ 50 nm, dispersion of ~ 5 wt.% ionic liquid leads to a conductivity rise of ~ 2–4 orders of magnitude. Structure of ionic liquid dispersed glass and glass-ceramic composites has been investigated by X-ray diffraction and FE-SEM, and thermal properties by DSC. It has been revealed by a galvanic cell method, impedance spectroscopy and dc polarization technique that these composites are essentially ionic in nature. Based on these investigations, a model for electrical transport has been proposed according to which Li+ ions are the majority charge carriers in these composites. The model suggests that ionic liquid acts like a filler between the glass/glass-ceramic grains and Li+ ions mainly migrate through these channels. These composites appear promising for Li+ ion battery applications.