Effect of Nb substitution on structural, electrical and electrochemical properties of LiTi₂(PO₄)₃ as electrolyte materials for lithium ion batteries

Abstract

The NASICON (Na Super Ionic CONductors)-type materials are good ionic conductors when serving as solid electrolytes for lithium-ion batteries. In this paper, Nb-doped LiTi 2 (PO 4) 3 has been synthesized by solid-state reaction method and the structural, vibrational and dielectric studies are systematically investigated. The X-ray diffraction conforms that the Nb-doped LiTi 2 (PO 4) 3 compound has NASICON structure, i.e. rhombohedral with space group R-3c. The average crystallite size and lattice constant are increased with dopant concentration. The grain sizes of the synthesized compounds are investigated by scanning electron microscope and it is found to be in the range of 5 μm. From Fourier-transform infrared spectroscopy spectra, stretching vibrations of P-O-P bond are identified in the region of 700-750 cm −1. AC electrical study is carried out by exploiting the impedance and dielectric spectroscopy. The activation energy increases with dopant concentration since ion diffusion becomes easy as the volume fraction of the grain increases. Non-Debye behavior of conductivity relaxation is reflected in the modulus analysis.

The Role of Sintering Temperature and Dual Metal Substitutions (Al3+, Ti4+) in the Development of NASICON-Structured Electrolyte

“…More energy loss is observed as more ionic collision occurs. The pattern of dielectric constant and loss in this study is similar to other NASICON-based solid electrolyte works [ 28 , 38 ]. These authors stated that their NASICON-based electrolytes have the behavior of an ionic conductor.…”

“…The highest conductivity achieved is 4.74 × 10 −6 S cm −1 when x = 0.4 ( Table 2 ). Rao et al [ 28 ] stated that the differences in conductivity are typically related to the connectivity between grains, which have a higher concentration of imperfections near the grain boundary. The authors reported a similar trend of conductivity variation where the highest conductivity value is 4.25 × 10 −6 S cm −1 for LiTi 2 (PO 4 ) 3 system.…”

“…As observed in Figure 8 , the value of ′ is low at high frequency region (Log f > 3) while high at low frequency region [ 36 ]. Rao et al [ 28 ] reported that polarization happens at low frequency as ions can form proper charge double layers at the surface of the electrode. ′ is observed to approach zero as Log f is more than 3.…”

Influence of Substrates on the Photoelectrochemical Performances of Ag2ZnSnSe4 Thin Films

“…62 It is observed from the films that the diameter of the arc decreases for the films deposited on Al and Ag substrates, which results in an increase in the electrical conductivity due to the reduction in resistance of the samples. 33 The results are well reflected in our PEC analysis where the film deposited on the Ag substrate shows higher open-circuit voltage and efficiency. The Nyquist plot is well fitted using ZSimpWin 3.21 software.…”

“…The presence of larger particle size in Ag/AZTSe is then expected to be beneficial to conductivity. 33 As the particle size of the thin films increases, this implies that the amount of grain boundary decreases. The extent of grain boundary scattering decreases because of the decrease in the amount of grain boundary.…”