Performance enhancement of gel polymer electrolytes using sulfonated poly(ether ether ketone) for supercapacitors

Abstract

Gel polymer electrolytes (GPEs) with reasonable mechanical properties are highly favorable for flexible/stretchable solid‐state supercapacitors. However, the widely explored poly(acrylic acid) (PAA)‐based GPEs provide unsatisfactory mechanical performance. Herein, a useful strategy is adopted to improve the performance of PAA‐based GPEs by incorporating sulfonated poly(ether ether ketone) (SPEEK) chains. The optimum SPEEK‐enhanced PAA GPE shows an ionic conductivity of 100 ± 1.57 mS cm−1, ultimate tensile strength of 4.2 ± 0.24 kPa and elongation at break of 858%, which are larger than those of the plain PAA GPE. A supercapacitor developed using such a SPEEK‐enhanced GPE also delivers higher specific capacitance, larger energy density and comparable cycling stability compared to a supercapacitor using a PAA GPE. This work suggests that rigid ionic polymers are suitable for improving the performance of GPEs with inferior mechanical properties. © 2021 Society of Chemical Industry

Functionalized Metallic 2D Transition Metal Dichalcogenide-Based Solid-State Electrolyte for Flexible All-Solid-State Supercapacitors

“…Compared to gel ones, SPEs typically show superior dimensional stability and mechanical strength. , Examples of SPEs are proton-conducting polymers, such as Nafion (brand name for sulfonated tetrafluoroethylene based fluoropolymer-copolymer) and sulfonated poly­(ether ether ketone) (SPEEK), , which are also widely exploited in the form of proton-exchange membranes (PEMs) for several energy storage and conversion applications. , Despite its high proton conductivity (σ, around 90 mS cm –1 at 25 °C) and its satisfactory mechanical and thermal stabilities, , Nafion has a high cost (∼$200 USD, 30 × 30 cm –2 for Nafion 117) that may limit its application in practical FSSSCs, whose market uptake is still at its infancy. Alternatively, SPEEK is a hydrocarbon-based thermoplastic polymer with mechanical strength (tensile strength ∼37 MPa, i.e., 80% higher than Nafion 117), thermal stability (up to 300 °C), , commercial availability of the polymeric precursor (i.e., poly­(ether ether ketone) -PEEK-), and σ (up to 40 mS cm –1 at 25 °C) adequate for the massive development of solid-state electrolytes for FSSSCs. , Furthermore, SPEEK has been extensively established as PEM material for fuel cells, − electrolyzers, , and redox-flow batteries. − Importantly, the physical/electrical/(electro)­chemical properties of SPEEK, including σ, water uptake (WU), and membrane swelling (MS), are determined by its degree of sulfonation (DS). , More in detail, the presence of acidic functional groups, i.e., −HSO 3 – , attached to the hydrophobic backbone of the polymer, form hydrophilic domains that have ion transferring capabilities . Although σ increases with increasing DS, excessive sulfonation deteriorates the mechanical strength of SPEEK.…”

“…Alternatively, SPEEK is a hydrocarbon-based thermoplastic polymer with mechanical strength (tensile strength ∼37 MPa, i.e., 80% higher than Nafion 117), 59 thermal stability (up to 300 °C), 60 , 61 commercial availability of the polymeric precursor (i.e., poly(ether ether ketone) -PEEK-), 62 and σ (up to 40 mS cm –1 at 25 °C) adequate for the massive development of solid-state electrolytes for FSSSCs. 54 , 63 Furthermore, SPEEK has been extensively established as PEM material for fuel cells, 64 − 66 electrolyzers, 67 , 68 and redox-flow batteries. 69 − 72 Importantly, the physical/electrical/(electro)chemical properties of SPEEK, including σ, water uptake (WU), and membrane swelling (MS), are determined by its degree of sulfonation (DS).…”