Mn-substituted spinel Li4Ti5O12 materials studied by multifrequency EPR spectroscopy

Abstract

In this contribution we report on the influence of Mn doping on various physical properties of Li₄Ti_5−xMn_xO₁₂ (x = 0, 0.005, 0.025, 0.01, 0.05, 0.075, 0.1 and 0.2). Spinel-type (space group Fd3m, a = 0.8358 nm) Li₄Ti_5−xMn_xO₁₂ was produced as highly uniform and polyhedral shaped powder in a size range between 200 and 400 nm. The crystal structure of Li₄Ti_5−xMn_xO₁₂, the morphology and the Mn-ion distribution have been investigated by X-ray diffraction (XRD) and scanning and transmission electron microscopies (SEM and TEM). The oxidation state of Mn and the conductivity behavior of Mn-substituted Li₄Ti_5−xMn_xO₁₂ samples have been studied using multi-frequency electron paramagnetic resonance (EPR). Mn is incorporated as Mn²⁺, and these ions increase the conductivity of Li₄Ti₅O₁₂; a conductivity value of 0.48 × 10⁻⁸ S cm⁻¹ was measured for Li₄Ti_5−xMn_xO₁₂ with x = 0.075, which is ten-fold larger than that of undoped Li₄Ti₅O₁₂.