A Water-in-Salt Electrolyte for Room-Temperature Fluoride-Ion Batteries Based on a Hydrophobic–Hydrophilic Salt

Realizing room-temperature, efficient, and reversible fluoride-ion redox is critical to commercializing the fluoride-ion battery, a promising post-lithium-ion battery technology. However, this is challenging due to the absence of usable electrolytes, which usually suffer from insufficient ionic conductivity and poor (electro)chemical stability. Herein we report a water-in-salt (WIS) electrolyte based on the tetramethylammonium fluoride salt, an organic salt consisting of hydrophobic cations and hydrophilic anions. The new WIS electrolyte exhibits an electrochemical stability window of 2.47 V (2.08–4.55 V vs Li+/Li) with a room-temperature ionic conductivity of 30.6 mS/cm and a fluoride-ion transference number of 0.479, enabling reversible (de)fluoridation redox of lead and copper fluoride electrodes. The relationship between the salt property, the solvation structure, and the ionic transport behavior is jointly revealed by computational simulations and spectroscopic analysis

Shape-Tailorable Graphene-Based Ultra-High-Rate Supercapacitor for Wearable Electronics

With the bloom of wearable electronics, it is becoming necessary to develop energy storage units, <i>e</i>.<i>g</i>., supercapacitors that can be arbitrarily tailored at the device level. Although gel electrolytes have been applied in supercapacitors for decades, no report has studied the shape-tailorable capability of a supercapacitor, for instance, where the device still works after being cut. Here we report a tailorable gel-based supercapacitor with symmetric electrodes prepared by combining electrochemically reduced graphene oxide deposited on a nickel nanocone array current collector with a unique packaging method. This supercapacitor with good flexibility and consistency showed excellent rate performance, cycling stability, and mechanical properties. As a demonstration, these tailorable supercapacitors connected in series can be used to drive small gadgets, <i>e</i>.<i>g</i>., a light-emitting diode (LED) and a minimotor propeller. As simple as it is (electrochemical deposition, stencil printing, <i>etc</i>.), this technique can be used in wearable electronics and miniaturized device applications that require arbitrarily shaped energy storage units

Schematic illustration of the preparation of the NNA@PEDOT electrode.

<p>Schematic illustration of the preparation of the NNA@PEDOT electrode.</p

FTIR spectra of EDOT and NNA@PEDOT.

<p>FTIR spectra of EDOT and NNA@PEDOT.</p

Comparison of the major features and merits of NNA@PEDOT with previously reported PEDOT-based electrodes in terms of areal/specific capacitance and cycling performance.

<p>Comparison of the major features and merits of NNA@PEDOT with previously reported PEDOT-based electrodes in terms of areal/specific capacitance and cycling performance.</p