Plasma Processing of Electrospun Li‐Ion Battery Separators to Improve Electrolyte Uptake

Abstract

Atmospheric pressure non‐equilibrium plasma treatments of poly(vinylidene fluoride) (PVdF) solutions and electrospun Li‐ion separators are implemented to improve fiber morphology and increase electrolyte uptake. Plasma pre‐treatment of PVdF solutions increased the viscosity and induced a morphological change of polymer chains, enabling the production of defect‐free mats with improved mechanical properties compared to those produced from non pre‐treated solutions. The post‐treatment of the electrospun separator induced a chemical modification of the PVdF surface and an increase of electrolyte uptake. A synergistic effect between the plasma treatments is reported: the electrolyte uptake of the pre&post‐treated separators is about 1200%, ten times larger than that of commercial Celgard separators.

Investigation of plasma‐induced chemistry in organic solutions for enhanced electrospun PLA nanofibers

“…The mechanisms of plasma‐liquid interactions are investigated by many research groups because they present paramount importance in systems with liquid solutions . A very novel application of this promising research field is the use of non‐thermal plasma technology for the treatment of pre‐electrospinning polymer solutions …”

“…Recently, pre‐electrospinning plasma treatment (PEPT) has been shown to improve the electrospinnability of different polymer solutions . PEPT has been found to enhance the electrospinnability, and helped obtaining thinner and bead‐free nanofibers at significantly lower polymer concentrations . However, further research is required as attention has been mostly paid to examining the nanofibers without a detailed investigation of the gas phase plasma and the plasma‐induced changes in the liquid solvents.…”

PVDF/TiO2/graphene oxide composite nanofiber membranes serving as separators in lithium‐ion batteries

“…To do so, the pore perimeter was measured by means of the Digimizer software. The electrolyte uptake was measured based on the following equation: where W dry is the weight of the completely dry membrane, and W wet is the weight of the membrane after immersion in the electrolyte solution (1 M solution of LiClO 4 ) …”

White paper on the future of plasma science and technology in plastics and textiles

“…Cold atmospheric pressure plasma (CAP) can be used in combination with the electrospinning process: pre‐treatment of polymeric solutions has recently emerged as a suitable tool to avoid beads formation in electrospun nanofibers. Indeed different studies demonstrated the possibility to improve electrospinnability of poly(ethylene oxide), poly(l‐lactic acid) and poly (vinylidene fluoride), PEO, PLLA and PVDF, respectively.…”

“…Reactive species together with charged molecules produced during the CAP treatment, play a crucial role in the improvement of electrospinnability induced in the polymeric solution. Finally, an increase of the solution viscosity and a “light” crosslinking (or increase of the average molecular weight) of the chains can be achieved performing a pretreatment of PVDF electrospinning solution, thus enabling the production of defect‐free nanofibers, with an improvement of both mechanical properties and electrolyte uptake …”