Xuejiang Wang

Renewable and Superior Thermal-Resistant Cellulose-Based Composite Nonwoven as Lithium-Ion Battery Separator

A renewable and superior thermal-resistant cellulose-based composite nonwoven was explored as lithium-ion battery separator via an electrospinning technique followed by a dip-coating process. It was demonstrated that such nanofibrous composite nonwoven possessed good electrolyte wettability, excellent heat tolerance, and high ionic conductivity. The cells using the composite separator displayed better rate capability and enhanced capacity retention, when compared to those of commercialized polypropylene separator under the same conditions. These fascinating characteristics would endow this renewable composite nonwoven a promising separator for high-power lithium-ion battery.

Effects of Ca doping on the oxygen ion diffusion and phase transition in oxide ion conductor La2Mo2O9

Abstract The effects of Ca doping on the oxygen ion diffusion and phase transition in oxide ion conductors La 2 Mo 2 O 9 has been investigated by low frequency internal friction measurement and X-ray diffraction. It is found that the two relaxation subpeaks at lower temperature, which are associated with the oxygen ion diffusion, and the phase transition peak at higher temperature were affected seriously by Ca doping. With the increase of Ca doping content, the peak height of the relaxation peak decreases, but the activation energy increases at first and then decreases. From the influence of Ca doping on the peak height and activation energy of the relaxation peaks, it is deduced that Ca doping can make the oxygen ion diffusion easier in some doping content. As for the phase transition around 833 K, substituting La 3+ cation in some degree with divalent Ca 2+ can suppress it and maintain the high temperature phase to lower temperature, which help to improve the oxygen ions conducting property.

Dielectric relaxation studies on the submicron crystalline La2Mo2O9 oxide-ion conductors

Abstract Submicron crystalline La 2 Mo 2 O 9 bulk samples with grain size of about 0.3 μm were successfully synthesized by sol–gel method and sintering process assisted by phase transformation. In the dielectric measurement, two prominent relaxation peaks with almost the same height (P d1 at lower-temperature and P d2 at higher-temperature) are observed in temperature spectrum as well as in frequency spectrum, which are associated with the short-distance diffusion of oxygen vacancies. The activation energies and relaxation times at infinite temperature of these two peaks are deduced as (1.22 eV, 3.3×10 −16 s) and (1.35 eV, 5.9×10 −16 s), respectively. The DC conductivity of the submicron crystalline samples, which is about 0.02 S/cm when extrapolated to 800 °C, is much smaller than that of the macrocrystalline samples. The reciprocal of the peak height for P d1 peak is linearly proportional to temperature, while that for P d2 peak is temperature independent. The reason for the co-appearance and the possible relaxation dynamics of the two peaks are discussed.

Dielectric relaxation study of Pb1−xLaxMoO4+δ (x = 0–0.3) oxide-ion conductors

DC conductivity and dielectric relaxation measurements are exploited to study the influence of La substitution on the dielectric properties and oxygen-ion transportation in PbMoO4 samples. The DC conductivity of La-doped samples is about 10−3 S cm−1 around 1073 K. A dielectric loss peak with activation energy of 0.6–0.8 eV is observed in the temperature spectrum as well as in the frequency spectrum for all La-doped PbMoO4 samples. With increasing La doping content, this peak becomes higher and shifts to higher temperature or lower frequency, and the activation energy becomes larger. It is suggested that this dielectric loss peak is associated with the short-distance diffusion of oxygen ions (or oxygen vacancies) between the 16f and 8e sites of the scheelite structure type with I41/a symmetry.