Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1·9Li0·1Ti3O7 ceramics

Abstract

The manganese doped layered ceramic samples (Na 1·9 Li 0·1 )Ti 3 O 7 : XMn(0·01≤X≤0·1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn 3+ at Ti 4+ sites, whereas for higher percentage of doping Mn 2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na 1·9 Li 0·1 Ti 3 O 7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electronhopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space.

Preparation and characterization of W-doped Li4Ti5O12 anode material for enhancing the high rate performance

“…As shown in Fig. 7, the charge-discharge curves of doped and undoped LTO electrodes display distinct potential plateaus around 1.5 V (vs. Li/Li + ) at 0.5 C, 1 C and 3 C, corresponding to the two-phase insertion reaction between Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 [18]. As can be seen, the voltage plateaus during lithium insertion process are nearly identical when the current rate was below 5 C. However, the discharge plateau decreased with increasing current density and even no obvious discharge plateau can be found for LTO at 20 C, while an 2) electrodes at different cycling rates: 1st to 10th cycles at 0.5 C, 11th to 20th at 1 C, 21st to 30th at 3 C, 31st to 40th at 5 C, 41st to 50th at 10 C, 51st to 60th at 20 C. obvious discharge plateau was observed for the Li 4 2) electrodes at different rates of 0.5 C, 1 C, 3 C, 5 C, 10 C and 20 C. The charge-discharge processes of the electrodes were taken for 10 cycles at each rate.…”

“…However, electrodes made from LTO without any materials modifications usually show poor rate performance, which mainly results from the poor electronic conductivity [6]. To enhance the electronic conductivity of this material, three methods were mainly proposed, including synthesis of nanosized particles [7][8][9][10][11], deposition of metal powder or carbon on LTO particle surface [12][13][14][15][16], substituting Li or Ti by doping it with metal ions (such as AI 3+ [6], Ag + [17], Na + [18], Mg 2+ [19], V 5+ [19,20], Zr 4+ [21], Ni 2+ [22], Nb 5+ [23], La 3+ [24] and Ru 4+ [25][26][27]). Doping can have a direct impact on the structure and stability of LTO during lithium intercalation and deintercalation.…”