Paper-Supported Sodium Alginate Composite Separator\nPrepared by Polymer-Assisted Phase Separation for Lithium Ion Batteries

Ecofriendly and renewable properties\nare highly desirable for \nseparators of lithium batteries, apart from the notorious safety issues.\nAs a natural polysaccharide material, sodium alginate (SA) has outstanding\nbiodegradability and biocompatibility and has usually been used for\nthe binder of electrodes due to its high ionic conductivity. Herein,\nSA porous separators were initially prepared by a facile polymer-assisted\nphase separation in which polyethylene glycol (PEG) and acetonitrile\nacted as a pore-forming agent and an extraction solvent, respectively.\nThe influence of PEG content on the pore formation was systematically\ninvestigated, and the uniform and continuous pore structures were\nsuccessfully realized at the PEG content of 200–500 wt %. Additionally,\nthe cellulose-based paper support (KP) and poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) porous coating (PVH) were adopted\nfor the decent mechanical integrity of SA porous membranes. The prepared\nSA composite separators showed excellent thermal dimensional stability,\nhigh porosity, and good electrolyte wettability. Moreover, the polar\nfeatures of SA endowed the composite separators with high ionic conductivity\n(4.8 mS cm<sup>–1</sup>) and lithium ion transference number\n(0.62). The strong depression capacity of lithium dendrites and a\ncomparable electrochemical performance were also observed for the\nSA-based separators compared with the pure KP and commercial polyolefin\nseparators.