Toward Safe and High-Performance Lithium–Sulfur Batteries via Polyimide Nanosheets-Modified Separator

Abstract

Lithium−sulfur batteries (LSBs) have broad application prospects in high density energy storage. Nevertheless, LSBs present serious safety concerns and rapid capacity decay due to the flammability and contractility of commercial separators at high temperatures and lithium polysulfide (LiPSs) dissolution. In view of this, a multifunctional modified separator is developed by combining a commercial polypropylene (PP) separator with a polyimide (PI)-Super P functional coating and a rigid nonflammable PI matrix. This PI/PP/PI-Super P separator provides multiple advantages: (i) strong physical blocking and chemical trapping/conversion ability for LiPSs, (ii) high flame-retardancy and dimensional stability, and (iii) superior electrolyte wettability and high efficiency lithium dendritic growth inhibition. As a result, the LSBs assembled with PI/PP/PI-Super P separators and pure sulfur cathodes exhibit an ultrahigh discharge specific capacity of 1611.8 mAh/g and excellent cycling performance (the average capacity attenuation within 100 cycles at 1 C is 0.469%) at 80 °C, which exceed the advanced results reported previously. More importantly, even when sulfur and organic electrolyte are adsorbed on PI/ PP/PI-Super P, the modified separator still shows good flame retardancy. Additionally, this modified separator is also suitable for LSBs with high sulfur loading. This work offers an innovative design concept for safe and high-performance LSBs.

Polyimide Compounds For Post‐Lithium Energy Storage Applications

“…In a following study, Luo and co‐workers, [79] fabricated a trifluoromethyl functionalized PI membrane using the electrospinning method. The presence of the negatively charged −CF 3 group on the membrane results in electrostatic repulsion of the polysulfide species, and therefore excellent cyclability of the Li−S cells which showed capacity retention of 95.6 % (from an initial value of 1512 mAh g −1 ) after 500 cycles at 1 C. The beneficial use of PI as an active separator that avoids a free transport of Li‐sulfide species to the Li anode in Li−S cells was also demonstrated in a recent study by Zhu et al [80] who synthesized 2D PI nanosheets and used them as a coating for commercial polypropylene separators. Similar to the previous studies, Li−S cells with PI‐based active separators show a substantially improved performance (initial capacity of 1125 mAh g −1 and nearly 86 % capacity retention after 200 cycles) outperforming the capacity and the cycling stability of conventional, commonly studied cells.…”

Polyimide Compounds For Post‐Lithium Energy Storage Applications

“…fore excellent cyclability of the LiÀ S cells which showed capacity retention of 95.6 % (from an initial value of 1512 mAh g À 1 ) after 500 cycles at 1 C. The beneficial use of PI as an active separator that avoids a free transport of Lisulfide species to the Li anode in LiÀ S cells was also demonstrated in a recent study by Zhu et al [80] who synthesized 2D PI nanosheets and used them as a coating for commercial polypropylene separators. Similar to the previous studies, LiÀ S cells with PI-based active separators show a substantially improved performance (initial capacity of 1125 mAh g À 1 and nearly 86 % capacity retention after 200 cycles) outperforming the capacity and the cycling stability of conventional, commonly studied cells.…”

Advanced Separator Materials for Enhanced Electrochemical Performance of Lithium–Sulfur Batteries: Progress and Prospects

“…These separators were designed to enhance the thermal stability and exhibited excellent self−extinguishing properties, superior thermal stability, and mechanical strength, as confirmed by combustion experiments. Zhu et al 183 Furthermore, to explore the intricate solid−liquid−solid reactions and material transformation mechanisms of Li−S batteries, particularly the behavior of polysulfides in the electrolyte, advanced characterization methods are required. 167 These may include in situ transmission electron microscopy, in situ XRD, in situ Raman spectroscopy, and in situ visualization of optical images.…”

“…These separators were designed to enhance the thermal stability and exhibited excellent self–extinguishing properties, superior thermal stability, and mechanical strength, as confirmed by combustion experiments. Zhu et al fabricated multilayer modified separators by combining PP separators with Super P and two layers of PI. These separators exhibited high flame retardancy and excellent electrolyte wettability.…”