The second half of the 20th century saw a new clay material named montmorillonite (MMT) with stratified structure, high surface area, and cation exchange capacity (CEC) that creates fabulous properties used in polymers, fuel cell, as well as adsorbent. MMT layers, encompassing an aluminium hydroxide octahedral sheet sandwiched two fused siloxane tetrahedral sheets, retain platelet structure and stack up together recurrently, forming a book-like structure with a regular space between the lamellar structures, which is called interlayer spacing or galleries with about 1 nm height. The isomorphic substitution within the clay layers, where Si4+ is substituted by Al3+ in the tetrahedral sheet and Al3+ is replaced by Mg2+ in the octahedral layer, results in excess negative charges in the interlayer spacing of MMT possesses. That results in the attraction of counter-cations, such as Na+ and Ca2+ to compensate for the extra charges. On the other hand, the hydrophilic feature of the MMT surface permits water and other polar molecules to intercalate into the galleries within clay layers. The lamellar structure of MMT can facilitate ionic conductivity by forming conductive highways for active ion species in hydrogel electrolytes.<br/>In this study, the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was modified with MMT and ILs to increase the ionic conductivity and wide window of electrochemical stability.<br/>The electrolyte membrane was prepared based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hybridized with montmorillonite (MMT). First, small quantities of PVDF-HFP were added to an intermediate casting solvent, acetone, at 50 oC during magnetic stirring to avoid agglomeration. When the desired amount of the polymer had been added, the solution was stirred for two hours before MMT was added to the solution. To prepare the IL-MMT, the MMT was immersed in [EMIM][NTf2] for 24 hours to obtain the IL-MMT. Then the IL-MMT was added into the PVDF-HFP solution at the ratio of 1:1, 2:1, and 3:1. This solution was stirred for 24 h to become homogenous.

Fabrication and electrochemical properties of MMT/PVDF-HFP composite electrolytes for supercapacitor

ACS Spring Meeting 2021

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