Electrical and electrochemical properties of molten-salt-synthesized 0.05 mol Zr- and Si-doped Li₄Ti₅O₁₂ microcrystals

This work emphasizes the structural, morphological, electrical, and electrochemical properties of 0.05 mol Zr- and Si-doped Li₄Ti ₅O₁₂ synthesized using the molten salt method and applied to negative electrodes in Li-ion batteries. Formation of the spinel phase with face-centered cubic structure in the nominally pure and Zr- and Si-doped samples are revealed from X-ray powder diffraction technique. Lattice parameters refined by full-profile Rietveld method are in accordance with the literature data for the Li₄Ti₅O₁₂ (Li _1.333Ti_1.667O₄) spinel structure. The presence of possible functional groups is identified using Fourier transform infra red spectroscopy. The field emission scanning electron microscopic images indicate the formation of micron-sized (1.5-2 μm) randomly distributed polyhedral-shaped particles. The electrical conductivity studies demonstrate the grain-conducting behavior of the material. The maximum DC conductivity of 2 × 10^-5 S cm^-1 is observed for Zr-doped Li ₄Ti₅O₁₂ at room temperature. The galvanostatic charge-discharge studies show that Zr-doped Li₄Ti₅O ₁₂ exhibits a high discharge capacity of about 325 mAh g^-1 at 0.01°C, higher than Si-doped Li₄Ti₅O₁₂ (200 mAh g^-1), and also that the cycling stability of Zr-doped Li₄Ti₅O₁₂ is enhanced.