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Tuning the Capacitance Properties of Nanocrystalline MnCO3 by the Effect of a Carbonizing Agent – Acceptance for publication

An article titled “Tuning the Capacitance Properties of Nanocrystalline MnCO3 by the Effect of a Carbonizing Agent” authored by P. Vishnu Vardhan, M.B. Idris, H.Y. Liu, S.R. Sivakkumar, P. Balaya, and S. Devaraj, has been accepted for publication in Journal of The Electrochemical Society.

[DOI: 10.1149/2.1271809jes]

Abstract

Nanocrystalline MnCO3 is synthesized by hydrothermal reduction of KMnO4 using different amounts of pyrrole. The effect of molar ratio of KMnO4:pyrrole on the phase purity, size of the particle, textural and capacitance properties of MnCO3 is studied systematically using various physico-chemical and electrochemical techniques. While X-ray diffraction studies confirm decline in the phase purity of MnCO3, FTIR, Raman spectroscopic and thermogravimetric studies reveal an increase in the amount of adsorbed water and residual carbon content on increasing the pyrrole concentration during the synthesis. An increase in the size of the particles and reduction in the number of mesopores are observed from the morphological and sorption studies on increasing the pyrrole concentration during the synthesis. A highest specific capacitance value of 296 F g−1 is obtained at a current density of 0.16 A g−1 for the nanocrystalline MnCO3, and this capacitance value found to decrease on increasing the concentration of pyrrole during the synthesis of nanocrystalline MnCO3 (166 and 140 F g−1 for the KMnO4:pyrrole ratio of 1:1 and 1:2, respectively).

NASICON-type La3+substituted LiZr2(PO4)3 with improved ionic conductivity as solid electrolyte – Acceptance of publication

An article titled “NASICON-type La3+substituted LiZr2(PO4)3 with improved ionic conductivity as solid electrolyte” authored by V. Ramar, S. Kumar, S.R. Sivakkumar and P. Balaya, has been accepted for publication in Electrochimica Acta[DOI: 10.1016/j.electacta.2018.03.115]

Abstract

NASICON-structured Li1+xZr2-xLax(PO4)3 (x = 0–0.2) solid electrolytes are prepared by sol-gel method. The influence of substitution of La3+ for Zr4+ on the ionic conductivity, morphology, and structure of the parent compound LiZr2(PO4)3 (LZP) is investigated. Rietveld refinement of powder x-ray diffraction data reveals that the La3+ substitution stabilizes the LZP in the highly conducting rhombohedral Rc phase at room temperature. La3+ substituted LZP display enhanced ionic conductivity, showing the highest ionic conductivity of 0.72 × 10−4 S/cm at room temperature for the composition Li1.1Zr1.9La0.1(PO4)3. The improvement in conductivity of LZP with another aliovalent substituent, Mg2+, whose ionic radii is similar to Zr4+ (0.72 Å) is also investigated. Further, the activation energy decreases from 0.53 eV for the parent LZP to 0.42 eV for x = 0.1 La3+ substituted LZP. Lithium-ion transference number obtained by direct current polarization for Li1.1Zr1.9La0.1(PO4)3 is 0.99, confirming the high ionic conducting nature of the solid electrolyte. Cyclic voltammetry recorded for Li1.1Zr1.9La0.1(PO4)3 shows electrochemical stability window up to ∼4.0 V vs. Li. In particular, La3+ substituted NASICON-type LZP (x = 0.1) exhibits good chemical and structural stability after exposing to air, water, Li metal, acidic and basic solutions.

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