Li diffusion properties of mixed conducting TiO2-B nanowires

LixTiO2-B nanowires (0 < x < 0.9) are considered to act as promising anode materials in secondary Li-ion batteries. Li self-diffusion parameters in mixed conducting nanowires of the composition Li0.3TiO2 are directly determined by mixing time (t(m))-dependent two-time Li-7 spin-alignment echo (SAE) nuclear-magnetic-resonance (NMR) correlation spectroscopy between 330 and 500 K. SAE NMR reveals extremely slow Li self-diffusion processes in LixTiO2-B. Li jump rates tau(-1) range from 5 to 2.5x10(3) s(-1). The corresponding hopping correlation functions F-2 can be well parametrized with stretched exponentials, F-2 proportional to exp[-(t/t(m))(gamma)], with an exponent gamma=0.35(2) being independent of temperature. The influence of spin-diffusion effects on the echo amplitude is elaborated by evolution time-dependent Li-7 SAE-NMR experiments. The results are compared with those obtained by conventional Li-7 NMR spin-lattice relaxation measurements.