Improvement in fast Na-ion conduction in Na3+xCr xTi2−x(PO4)3 glass–ceramic electrolyte material for Na-ion batteries

Abstract

Abstract: In this report, efforts were made to investigate and characterize a variety of compositions in a glass system of general formula Na3+xCrxTi2−x(PO4)3 (x = 0, 0.25, 0.5 and 0.75 mol%, designated as NCTPx) to optimize their properties for use in Na-ion batteries. Several crystalline phases such as Na3Ti2(PO4)3 (COD-4106515) (NASICON), Cr2O3 (ICSD-25781) and Cr(PO3)3 (ICSD-39410) are precipitated during the process of crystallization. The microstructures of all the glass and glass–ceramic samples are analyzed using SEM and are correlated with powder XRD to explain the ionic conductivity for a given glass–ceramic sample. Single semicircle in the complex impedance plots clearly suggests that the present NCTPx glass samples exhibit a predominantly single-ion conduction mechanism. Electrical conductivity data follow the Arrhenius equation. The power-law exponent ‘s’ is observed to be the lowest (0.70) for the best conducting glass–ceramic sample NTCP0.5 (4.24 × 10−4 S/cm). The electrical modulus study proves that the conductivity relaxation of NCTPx glass–ceramic samples is temperature independent. Scaling behavior in the normalized spectra indicates that frequency-dependent relaxation behavior is unaffected by the temperature. Graphic abstract: [Figure not available: see fulltext.].