ABSTRACT
The thermal stability of the polyethylene (PE) separator is of utmost importance for the safety of lithium-ion batteries. Although the surface coating of PE separator with oxide nanoparticles can improve thermal stability, some serious problems still exist, such as micropore blockage, easy detaching, and introduction of excessive inert substances, which negatively affects the power density, energy density, and safety performance of the battery. In this paper, TiO2 nanorods are used to modify the surface of the PE separator, and multiple analytical techniques (e.g., SEM, DSC, EIS, and LSV) are utilized to investigate the effect of coating amount on the physicochemical properties of the PE separator. The results show that the thermal stability, mechanical properties, and electrochemical properties of the PE separator can be effectively improved via surface coating with TiO2 nanorods, but the degree of improvement is not directly proportional to the coating amount due to the fact that the forces inhibiting micropore deformation (mechanical stretching or thermal contraction) are derived from the interaction of TiO2 nanorods directly "bridging" with the microporous skeleton rather than those indirectly "glued" with the microporous skeleton. Conversely, the introduction of excessive inert coating material could reduce the ionic conductivity, increase the interfacial impedance, and lower the energy density of the battery. The experimental results show that the ceramic separator with a coating amount of ~0.6 mg/cm2 TiO2 nanorods has well-balanced performances: its thermal shrinkage rate is 4.5%, the capacity retention assembled with this separator was 57.1% under 7 C/0.2 C and 82.6% after 100 cycles, respectively. This research may provide a novel approach to overcoming the common disadvantages of current surface-coated separators.
ABSTRACT
CaSnO3: Pr3+ phosphor for new application in temperature sensing was investigated. CaSnO3: 0.3%Pr3+ had distorted orthorhombic perovskite structure and Pr3+ occupied Ca2+ sites due to their similar ionic radii. CaSnO3: 0.3%Pr3+ had spherical particles with mean size of 0.816 µm. The electric dipole-dipole interaction could explain the concentration quenching mechanism. The chromaticity coordinates were (0.1324, 0.3847), located in greenish-blue region and the average afterglow decay time was 60.2 s for CaSnO3: 0.15%Pr3+, which had potential applications for LED and emergency lighting. CaSnO3: 0.3%Pr3+ had the activated energy of 0.380 eV. The maximum relative temperature sensitivity for CaSnO3: 0.3%Pr3+ was 7.57% K-1 at 298 K and relative sensitivity was as high as 6722.76/T2 K-1, which was better than that of most Pr3+ doped phosphors and had potential application in temperature sensing. Moreover, the possible luminescence and long afterglow mechanisms and thermal quenching process of 3P0 level through IVCT state were proposed.
ABSTRACT
The authors synthesised porous GdF3:Er3+,Yb3+-COOH core-shell structured bi-functional nanoparticles through a one-step hydrothermal route during which ethylene diamine tetraacetic acid) was bound to the surface of the nanoparticles. It has high up-conversion emission intensity for monitoring the drug release process and magnetisation saturation value (10.2â emu/g) for drug targeting under foreign magnetic fields. Moreover, porous GdF3:Er3+,Yb3+ as drug carriers with a high drug-loading efficiency. cis-Dichlorodiammineplatinum(II) (cisplatin, CDDP)-loaded GdF3:Er3+,Yb3+ nanoparticles (GdF3:Er3+,Yb3+-CDDP) were characterised by the Fourier transform infrared spectra, and CDDP was loaded in the form of electrostatic interaction and hydrogen bonds. Compared with CDDP alone, GdF3:Er3+,Yb3+-CDDP nanoparticles increase concentration of CDDP in the target site and enhance its anticancer efficiency. Therefore, the as-prepared GdF3:Er3+,Yb3+-COOH nanoparticles allow simultaneous targeted drug delivery and monitoring as promising anti-cancer theranostic agents.
