Decoration of Silica Nanoparticles on Polypropylene Separator for Lithium–Sulfur Batteries

Abstract

A SiO nanoparticle decorated polypropylene (PP) separator (PP-SiO) has been prepared by simply immersing the PP separator in the hydrolysis solution of tetraethyl orthosilicate (TEOS) with the assistance of Tween-80. After decoration, the thermal stability and the electrolyte wettability of the PP-SiO separator are obviously improved. When the PP-SiO separator is used for lithium-sulfur (Li-S) batteries, the cyclic stability and rate capability of the batteries are greatly enhanced. The capacity retention ratio of the Li-S battery configured with the PP-SiO separator is 64% after 200 cycles at 0.2 C, which is much higher than that configured with the PP separator (45%). Moreover, the rate capacity of the Li-S batteries using the PP-SiO separator reaches 956.3, 691.5, 621, and 567.6 mAh g at the current density of 0.2, 0.5, 1, and 2 C, respectively. The reason could be ascribed to that the polar silica coating not only alleviates the shuttle effect but also facilitates Li-ion migration.

Preparation of 4A zeolite coated polypropylene membrane for lithium‐ion batteries separator

“…Rate cells capability containing the neat PP and the PPA8 coated separators are shown in Figure at various current densities. Discharge capacity of the separators significantly decreased as the current density increased . As it can be observed, capacity of the neat PP separator was clearly lower than that of the PPA8 coated separator.…”

“…Figures and present cycling performance and rate capability of the neat PP and PPA8 coated separators at the room temperature and constant charge/discharge current density ranging from 2.5 to 4.2 V. As observed in Figure , equipped cell with the coated separator's discharge capacity was slightly reduced in the cycling experiments. The same results have also been observed in the literature . This reduction can be attributed mainly to physical changes in active materials and interfacial properties and also gradually increment in the cell internal resistance during cycling …”

“…After 100 cycles, the discharge capacity retention of the PPA8 coated separator was 96.2%, which was much higher than that of the neat PP separator as 83.4%. This discharge capacity reduction can be attributed to the unavoidable decreased active materials loss of the PPA8 coated separator …”

“…Generally, good cycling performance can be due to two reasons: first, porous structure of the coated PPA8 separator including intrinsic porosity of its internal cavities and also added interstitial cavities of the coated zeolites particles result in the enhanced liquid electrolyte wettability and ion transport . Second, higher capacity of the coated PPA8 separator to maintain more liquid electrolyte compared with the neat hydrophobic PP separator results in leakage prevention of the liquid electrolyte during cycling and then the separator improved cyclability …”

Separator Membranes for Lithium–Sulfur Batteries: Design Principles, Structure, and Performance

“…Yttrium, one of the transition metals, is chemically similar to the lanthanides, exhibits similar polysulfide‐binding properties, and is effective in the catalytic reduction of polysulfides. Li et al directly decorated silica nanoparticles on a commercial polypropylene membrane by immersing it in an hydrolysis solution of tetraethyl orthosilicate. The modification provided thermal and mechanical stability to the composite separator.…”