Enhanced wettability and thermal stability of polypropylene separators by organic–inorganic coating layer for lithium‐ion batteries

Abstract

Organic–inorganic coating polypropylene separators were developed by introducing SiO2 nanoparticles through sol–gel process, where polydopamine was used as an intermediate layer. Scanning electron microscopy results showed the coating layers have highly porous structure, which was beneficial for liquid electrolyte uptake. Compared with pristine polypropylene separator, the ceramic separators showed improved thermal stability, higher ionic conductivity, and lower interfacial impedance. The cells employing the ceramic separators delivers excellent discharge capacity (retention = 75%) and coulombic efficiency up to 98% at 2 °C rate after 100 cycles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46478.

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

“…Higher ion conductivities of the coated separators are suitable for discharge rate capability enhancement where could be approved experimentally. Rate cells capability containing the neat PP and the PPA8 coated separators are shown in Figure at various current densities.…”

“…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 …”

“…It is noteworthy that difference in the discharge capacity of the neat PP and the PPA8 coated separators at higher current densities becomes sharper. This can be attributed to the fact that high current densities have greater effect on the ion transfer under ohmic polarization and the lithium ion penetration rate was reduced at the higher current densities . This founding reveals that the 4A zeolite is a suitable selection for the neat PP separator coating for usage in the lithium‐ion batteries.…”