A novel PPESK fibrous membrane separator based on electrospinning technique for lithium-ion battery
In order to improve the low porosity, poor thermal stability and insufficient electrolyte wettability of commercial polyolefin separator, the novel PPESK fibrous membrane separator has been fabricated via electrospinning for the use of lithium-ion batteries. By the use of high-speed collection drum, the tensile strength of the electrospinning oriented PPESK fiber membranes increase significantly and reaches 18.9 MPa. Hot oven testing shows that oriented PPESK fiber membranes are thermally size stable at a high temperature of 220 °C. The oriented PPESK fiber membrane exhibits high level of porosity (83%) and excellent electrolyte uptake (720%). Moreover, the ionic conductivity increases to 1.85 mS cm -1 compared with the 0.41mS cm -1 of commercial Celgard 2400 separator. In addition, the lithium-ion battery assembled with electrospinning oriented PPESK fiber membrane shows high capacity retention, stable cycle performance and excellent rate capability. Therefore, the electrospinning oriented PPESK fiber membrane is likely to be a promising candidate of high-power lithium-ion battery owing to its comprehensive outstanding characteristics.
Membranes
This review evaluates the characteristics and advantages of employing polymer electrolytes in lithium/sulfur (Li/S) batteries. The main highlights of this study constitute detailed information on the advanced developments for solid polymer electrolytes and gel polymer electrolytes, used in the lithium/sulfur battery. This includes an in-depth analysis conducted on the preparation and electrochemical characteristics of the Li/S batteries based on these polymer electrolytes.
Brauer groups of genus zero extensions of number fields
We determine the isomorphism class of the Brauer groups of certain nonrational genus zero extensions of number fields. In particular, for all genus zero extensions E of the rational numbers Q that are split by Q(√2), Br(E) ≅ Br(Q(t)).