Thermally stable, nano-porous and eco-friendly sodium alginate/attapulgite separator for lithium-ion batteries

Traditional polyolefin separators are widely used in lithium-ion batteries. However, they are subject to thermal shrinkage which may lead to failure at elevated temperatures, ascribed intrinsically to their low melting point. And besides, recycling of spent lithium-ion batteries mainly focuses on precious metals, like cobalt, while other components such as separators are usually burnt or buried underground, causing severe hazards for the local environment, such as "white pollution". Therefore, to solve the aforementioned problems, we incorporated attapulgite (ATP) nanofibers, a natural mineral, into sodium alginate (SA), a biodegradable polysaccharide extracted from brown algae, through a phase inversion process, whereby a porous separator was prepared. The resulting SA/ATP separator is endowed with high thermal and chemical stability, enhanced retardancy to fire, and excellent wettability with commercial liquid electrolyte (420% uptake). Attractive cycling stability (82% capacity retention after 700 cycles) and rate capability (115 mAh g(-1) at 5 C) in LiFePO4/Li cells are achieved with such separator, additionally. Moreover, as both ingredients are nontoxic, this eco-friendly separator can degrade in soil without inducing any contamination. This work offers a viable choice to process a thermally stable, eco-friendly separator and open up new possibilities to improve the safety of batteries while alleviating the "white pollution".