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.
Porous PAN micro/nanofiber membranes with potential application as Lithium-ion battery separators: physical, morphological and thermal properties
The porous PAN micro/nanofiber membranes with an average diameter of 700–800 nm were produced in one step by electrospinning a ternary system of PAN/DMF/H2O with phase separation mechanism. Also, non-porous PAN micro/nanofiber membranes with a similar diameter were prepared. Physical, morphological, mechanical and thermal properties of the porous PAN micro/nanofiber membranes were characterized and compared with those of non-porous PAN membranes. Thermal shrinkage of the porous PAN micro/nanofiber membranes and the Celgard PP separators were examined to be 15% and 95%, respectively, after treating for 45 min at 200 °C. The porosity impacts of porous PAN micro/nanofiber membranes were explored on some of the effective properties in battery performance. The results revealed that the porous PAN micro/nanofiber membranes had a higher air permeability value than the Celgard PP separators, indicating that the porosity, interconnected pores and ionic conductivity were higher. The porous PAN micro/nanofiber membranes had an enhanced electrolyte wettability, small contact angle and large electrolyte uptake leading to be the most promising candidate for Li-ion battery (LIB) separators.
Improved performance of PVdF-HFP/PI nanofiber membrane for lithium ion battery separator prepared by a bicomponent cross-electrospinning method
Abstract Poly(vinylidene fluoride-co-hexafluoropropylene)/polyimide (PVdF-HFP/PI) composite nanofiber membrane used for lithium ion battery separator was prepared by an electrospinning apparatus equipped with four needles. Two needles were fed with PVdF-HFP solution and the rest with PI solution and the two types of polymer solutions were arrayed alternately, in a straight line to form a composite membrane, which could be referred to as cross-electrospinning, followed by thermal calendering process to improve the mechanical property of the composite membrane via fusing the PVdF-HFP component which has lower melting temperature. PVdF-HFP/PI composite membrane showed positive results in terms of physical properties. Additionally, the cells assembled with the composite separators exhibited better electrochemical stability, lower interfacial resistance and higher ionic conductivity, compared with Celgard 2400 PP separator. Conspicuously, the improved performance of lithium ion battery separator indicated that bicomponent cross-electrospinning method could be potentially applied for designing future lithium ion battery separator.