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.
Flexible, Heat-Resistant, and Flame-Retardant Glass Fiber Nonwoven/Glass Platelet Composite Separator for Lithium-Ion Batteries
A new type of high-temperature stable and self-supporting composite separator for lithium-ion batteries was developed consisting of custom-made ultrathin micrometer-sized glass platelets embedded in a glass fiber nonwoven together with a water-based sodium alginate binder. The physical and electrochemical properties were investigated and compared to commercial polymer-based separators. Full-cell configuration cycling tests at different current rates were performed using graphite and lithium iron phosphate as electrode materials. The glass separator was high-temperature tested and showed a stability up to at least 600 °C without significant shrinking. Furthermore, it showed an exceptional wettability for non-aqueous electrolytes. The electrochemical performance was excellent compared to commercially available polymer-based separators. The results clearly show that glass platelets integrated into a glass fiber nonwoven performs remarkably well as a separator material in lithium-ion batteries and show high-temperature stability.
Effect of polydopamine surface coating on polyethylene separators as a function of their porosity for high-power Li-ion batteries
Abstract This study demonstrates the effect of polydopamine coating on separator membranes used in liquid electrolyte batteries as a function of membrane porosity. We select two typical separators that differed only in porosity. High-porosity (16H) and low-porosity (16L) separators are coated with polydopamine by simple dip-coating. Their properties are evaluated via scanning electronic microscopy (SEM) and determining the water contact angle, Gurley number, ionic conductivity, and uptake volume of liquid electrolyte. In addition, the effect of polydopamine coating on electrochemical properties is tested using CR2032 coin-type half-cells (LiMn2O4/Li metal). With enhanced hydrophilic properties of surfaces as keeping pore structures, both of polydopamine coated high and low porous separators show enhanced rate capability and cell performance compared to uncoated versions. The effect of polydopamine coating is greatly enhanced in the low-porosity separators, with up to 40% increase in power capability (at 5 C rate) and a 290% increase in cycle performance (after 500 cycles, at C/2 rate), compared to the high-porosity type (13% increase in power capability, 43% increase in cycle performance).