Nickel doped spinel lithium manganate - some insights using opto-impedance

Opto-impedance studies on spinel type pristine and Ni-doped LiMn2O4, an important cathode system for Li-ion batteries, have revealed the difference in electronic structure arising out of the Ni-substitution. The opto-impedance spectra of Ni-doped LiMn2O4 even under dark condition exhibit a more complex structure (two semicircles with some skewed structure) suggesting the presence of the defect structure(s) remaining dormant which upon UV shining gets merged to form a single semicircle. Qualitatively, this aliovalent substitution modifies the charge transfer state and activates a defect initiated Warburg diffusion process with a time scale of ∼50 μs.