Electrochemical Properties of LLTO/Fluoropolymer-Shell Cellulose-Core Fibrous Membrane for Separator of High Performance Lithium-Ion Battery
A superfine Li0.33La0.557TiO3 (LLTO, 69.4 nm) was successfully synthesized by a facile solvent-thermal method to enhance the electrochemical properties of the lithium-ion battery separator. Co-axial nanofiber of cellulose and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was prepared by a co-axial electrospinning technique, in which the shell material was PVDF-HFP and the core was cellulose. LLTO superfine nanoparticles were incorporated into the shell of the PVDF-HFP. The core–shell composite nanofibrous membrane showed good wettability (16.5°, contact angle), high porosity (69.77%), and super electrolyte compatibility (497%, electrolyte uptake). It had a higher ionic conductivity (13.897 mS·cm−1) than those of pure polymer fibrous membrane and commercial separator. In addition, the rate capability (155.56 mAh·g−1) was also superior to the compared separator. These excellent performances endowed LLTO composite nanofibrous membrane as a promising separator for high-performance lithium-ion batteries.
Interface reaction and its effect on the performance of a CO2 gas sensor based on Li0.35La0.55TiO3 electrolyte and Li2CO3 sensing electrode
Abstract A new potentiometric CO 2 gas sensor using lithium–lanthanum–titanate (Li 0.35 La 0.55 TiO 3 , LLTO) electrolyte, Li 2 CO 3 sensing electrode, and Li 2 TiO 3  + TiO 2 reference electrode was investigated. The microstructure and electrical properties of the optimized solid electrolyte were examined and the measured conductivity values were found consistent with those reported in literature. The performance of the sensor depended both on the fabrication temperature and the sensor operation temperature. Sensors with the sensing electrode fabricated above 500 °C performed poorly. For sensing electrodes fabricated at 500 °C, as the sensing temperature increased from 300 to 450 °C, the performance of the sensor improved (near Nernstian response), but above 450 °C, the sensor degraded. The proposed hypothesis for the degradation beyond 450 °C is that at low levels of CO 2 (ppb in the background), Li 2 CO 3 reacts with LLTO resulting in insertion of Li + into LLTO that causes changes in the electrical properties of the electrolyte. Poor performance of sensors fabricated at 700 °C was due to formation of a new phase, LaLi 1/3 Ti 2/3 O 3 . Thermodynamic calculations combined with X-ray diffraction of the reaction products are used to support the hypothesis. Introduction of high concentrations of CO 2 (~99.99%) during sensor fabrication (650 °C) eliminated the reaction between Li 2 CO 3 and LLTO, and also facilitated the bonding between the electrode and the electrolyte. As for long-term device performance, it is shown that the sensor can measure changes in CO 2 concentrations reproducibly below temperatures of 450 °C, as long as it is operated in conditions where there is a background of CO 2 , such as in ambient atmosphere or combustion environments. The sensor exhibits minimal interference toward oxygen, but significant interference to humidity.
Regional strategies for the minerals industries of the states of the SADCC
The SADCC has been in existence for eleven years but little progress has been made in regional coordination of the minerals sector even though this sector is the most important exporter of the region. There is however scope for minerals development at the regional level.