No abstract

No abstract

The effect of Ti substitution for Mn on the structure and electrochemical properties of the LiNi 0.5 Mn 1.5Ϫx Ti x O 4 was studied. The LiNi 0.5 Mn 1.5Ϫx Ti x O 4 (x ϭ 0-1.0) was successfully synthesized at 900°C by solid-state reaction method. Additional annealing was used for the ordering of transition metals in octahedral sites. X-ray diffraction ͑XRD͒ and selected-area electron diffraction study clearly showed that Ti substitution leads to the disordering of the transition metals and consequently lowers the symmetry from primitive simple cubic structure ( P4 3 32) to face-centered spinel (Fd3 ¯m). Electron diffraction patterns of the LiNi 0.5 Mn 1.5Ϫx Ti x O 4 showed stacking faults which came from the localized incorporation of Ti atoms in the lattice. LiNi 0.5 Mn 1.5Ϫx Ti x O 4 exhibited higher operating voltages, faster lithium ion diffusion, and better rate capability than Ti-free LiNi 0.5 Mn 1.5 O 4 confirmed by electrochemical tests including galvanostatic intermittent titration technique measurement. In addition, ex situ XRD data of the delithiated LiNi 0.5 Mn 1.5Ϫx Ti x O 4 (x ϭ 0, 0.3, and 0.5͒ showed that phase transition was suppressed with increasing Ti content. A large amount of Ti substitution in LiNi 0.5 Mn 1.5Ϫx Ti x O 4 , however, exhibited low discharge capacity, which would be due to the blocking migration pathway of electrons by the Ti 4ϩ (d 0 ) ions in octahedral sites.

No abstract

No abstract

No abstract

No abstract

No abstract