Bis(2,2′‐biphenoxy)borates for Electrochemical Double‐Layer Capacitor Electrolytes

Abstract

Fluorine makes the difference! Bis(2,2'-biphenoxy)borates decorated with fluorine substituents have been synthesized and studied in supercapacitor test cells (see scheme). A clear trend towards higher electrochemical stability with the increase of the fluorine content has been observed. For a maximum performance, only two fluorine substituents per benzene moiety are required.

Halogen-free water-stable aluminates as replacement for persistent fluorinated weakly-coordinating anions

“…The most prominent and most stable WCAs are presented in Fig. 1, namely the borates BArF 20 and BArF 24 , 4 Waldvogel's fluorinated bis(2,2′-biphenoxy)borates with increased redox-stability, 5 Krossing's perfluoroalkylated Al(OR F ) 4 − , 6 Willner's B(CF 3 ) 4 − , 7 Lacour's tris(tetrachlorobenzenediolato)phosphate(V), 8 and halogenated or trifluoromethylated carboranates [CB 11 X n H 12−n ] − (n = 1 to 12; X = F, Cl, Br, I, CF 3 ). 9 Halogen substituents promote a high solubility in organic solvents and chemical inertness towards electrophiles and oxidants.…”

Substituent effect on supercapacitive performances of conducting polymer‐based redox electrodes: Poly(3′,4′‐bis(alkyloxy) 2,2′:5′,2″‐terthiophene) derivatives

“…Especially, the fast advancement of portable and flexible consumer electronic products such as roll‐up displays, electronic papers, wearable sensors, smart phones, and touch screens makes it necessary to develop low‐cost, lightweight, thin and flexible energy storage systems. In this context, supercapacitors, also commonly known as electrochemical capacitors or ultracapacitors, are considered as new generation energy storage devices in terms of their energy and power densities …”

Scalable and Selective Preparation of 3,3′,5,5′-Tetramethyl-2,2′-biphenol

“…Additionally, 3,3′,5,5′-tetramethyl-2,2-biphenol can be transformed into sodium­[bis­(3,3′,5,5′-tetramethyl-2,2′-biphenoxy)­borate] . This product is extraordinarily stable at electrochemical conditions and applicable in electrochemical double-layer capacitor electrolytes for capacitive energy storage. , …”

“…21 This product is extraordinarily stable at electrochemical conditions and applicable in electrochemical double-layer capacitor electrolytes for capacitive energy storage. 22,23 The conversion of 2,4-dimethylphenol (1) to the desired 3,3′,5,5′-tetramethyl-2,2′-biphenol turned out to be challenging. 24,25 The direct C−H activation led to polycyclic byproducts with a high structural diversity.…”