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    Ionic liquid composites with garnet-type Li6. 75Al0. 25La3Zr2O12: Stability, electrical transport, and potential for energy storage applications
    (Elsevier, 2024-04) Dalvi, Anshuman; Sivasubramanian, S.C.
    Garnet composites with ionic liquid dispersion have been prepared for electrolytic applications. Various ionic liquids (ILs) in small amounts were added to garnet type Li6.75Al0.25La3Zr2O12 (LALZO) to improve its ionic conductivity and electrode-electrolyte interfacial compatibility. The optimal composition having ∼6 wt% EMIM BF4 in LALZO showed a high ionic conductivity of 6 × 10-4 Ω-1cm-1 at room temperature, which is almost two orders of magnitude higher than the pristine garnet pellet. Such a high conductivity is attributed to the alteration of the ionic liquid-garnet interface by a weak non-uniform chemisorption. The thermal stability of the composites was confirmed by high-temperature X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry (DSC), and dynamic electrical transport measurements, which suggested their stability at least up to 200 °C. The electrochemical performance of the composite was evaluated by assembling 2032-type LFP//LALZO-IL//Li cell, which displayed promising candidature for energy storage applications.
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    Electrical transport in li2so4-li2o-p2o5 glassy ionic system in thermally unstable region
    (Centre for Info Bio Technology, 2023) Dalvi, Anshuman
    The electrical, structural and thermal characterization of Li2SO4-Li2O-P2O5 glassy system reveals interesting results. Scanning electron microscopy reveals the phase separation and formation of nanocomposites structure during crystallization. The electrical conductivity of Li2SO4-Li2O-P2O5 is studied above the crystallization. Differential scanning calorimetry scans confirm the glassy nature and exhibits well separated glass transition and crystallization temperatures that are clearly evident on conductivitytemperature cycles as well. The conductivity increases with Li2SO4 content for T< Tg and T> Tc.
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    Preparation and characterization of novel solid electrolytes based on [EMIM] BF4 and lithium nitrate confined silica gels
    (Elsevier, 2019-11) Sivasubramanian, S.C.; Dalvi, Anshuman
    Novel 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.
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    Vanadium substituted Li+-NASICON systems: Tailoring electronic conductivity for electrode applications
    (Elsevier, 2021-04) Dalvi, Anshuman
    Mixed ionic-electronic NASICON structured systems namely, LiTi2(PO4)3-x(VO4)x and Li1.3Al0.3Ti1.7(PO4)3-x(VO4)x, for x = 0.1–0.4 have been prepared by partial substitution of V5+ in place of P5+ in LiTi2(PO4)3 (LTP) and Li1.3Al0.3Ti1.7(PO4)3 (LATP), respectively. A systematic investigation has been carried out to understand the mechanism of mixed electrical transport by varying the amount of Vanadium in subsequent steps. The structural features of these systems have been studied using XRD and FESEM that suggest Vanadium acceptability in the NASICON type network structure atleast up to x = 0.4 without any notable precipitation. High temperature in situ XRD studies suggest stability of the structure at least up to ∼500 °C. The electronic conductivity in these composites have been attributed to polaron hopping that could be tailored systematically as suggested by dc conductivity studies. The highest total conductivity and electronic conductivity values have been found to be 2 × 10−4 Ω−1cm−1 and 9 × 10−5 Ω−1cm−1, respectively for LTP with x = 0.4 at 100 °C. In order to test their potential as electrodes, symmetric cells of the type MIE|LiPF6/Li2SO4|MIE have been fabricated and charged/discharged at different current densities. These materials exhibit appreciable capacity and have been found to be suitable for EDLC/pseudo supercapacitor electrode applications.
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    Dispersion of Li2SO4-LiPO3 glass in LiTi2(PO4)3 matrix: Assessment of enhanced electrical transport
    (Elsevier, 2019-04) Dalvi, Anshuman
    A novel mechanical milling assisted synthesis route has been used to prepare new generation Li+ ion glass-ceramic composites using (i) glassy system 60[Li2SO4]-40[LiPO3] (60LSLP) and (ii) Li+ NASICON, i.e., LiTi2(PO4)3 known as LTP. Effect of compositional alterations, sintering conditions and cooling process on electrical transport has been investigated. Preparation conditions along with compositional alterations have yielded in reporting the best conducting composition. The ionic glass content was varied in (60LSLP)y-(LTP)100-y matrix for y = 5–20 wt %. It has been observed that various parameters viz. milling time, composition, annealing temperature, time and cooling conditions have a significant impact on ionic transport. The highest in-grain (∼2 × 10−4 Ω−1 cm−1) and grain boundary (∼1 × 10−5 Ω−1 cm−1) Li+ ion conductivity values at 100 °C have been obtained for y = 20 wt%. These have been found to be significantly higher than that of the pristine LTP prepared with similar preparation conditions. Electrical response (Z″-ω) and dielectric relaxation (tan δ - ω) investigations suggest that mobile Li+ ions from glassy phase significantly contribute to conductivity. The elemental distribution investigations using Energy Dispersive X-ray Spectroscopy (EDS) mapping on fractured surface suggests homogeneous distribution of LTP and glassy phase in the composite. Cyclic Voltammetry (CV) results reveal no degradation in the electrochemical stability in 20 cycles, and that these composites are potential candidates for Li+ ion all-solid-state battery applications.
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    Enhanced electrical transport in ionic liquid dispersed TMAI-PEO solid polymer electrolyte
    (AIP, 2015-02-17) Kumar, Anil; Dalvi, Anshuman
    A polymer composite is prepared by dispersing ionic liquid [Bmim][BF4] in Polyethylene oxide-tetra methyl ammonium iodide composite and subsequent microwave treatment. X-ray diffraction patterns confirm the composite nature. To explore possibility of proton conductivity in these films, electrical transport is studied by impedance spectroscopy and DC polarization. It is revealed that addition of ionic liquid in host TMAI-PEO solid polymer electrolyte enhances the conductivity by ∼ 2 orders of magnitude. Polarization measurements suggest that composites are essentially ion conducting in nature. The maximum ionic conductivity is found to be ∼2 × 10−5 for 10 wt % ionic liquid.
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    Li2SO4⎯Li2O⎯P2O5 ionic glass dispersed with [Bmim] [PF6] ionic liquid: Electrical transport and thermal stability investigations
    (AIP, 2014-02-17) Kumar, Anil; Dalvi, Anshuman
    A fast ionic composite is prepared by dispersion of Ionic liquid [Bmim][PF6] in Li2SO4⎯Li2O⎯P2O5 glass matrix by mixing and through grinding. Amorphous/glassy nature of the samples is confirmed by X-Ray diffraction (XRD). Surprisingly, the electrical conductivity of the samples is found to be increasing by ∼ 2 orders of magnitude and exhibits typical Arrhenius behavior with low activation energy. DC polarization and impedance spectroscopy measurements suggest that samples are essentially ionic in nature. The conductivity isotherms were also obtained at different temperatures (T < 100 °C) and found to be appreciably stable at least for ∼ 10 days.