Microscopic-Level Anion & Diluent Chemistry in Electrolyte for Aqueous Supercapacitors Operating at High Voltage and Low Temperature.
basic_science · Level V
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- Record sourced from PubMed, PMID 40528715.
- Also identified by DOI 10.1002/adma.202503157.
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Abstract
Aqueous supercapacitors, serving as safe and green high-power energy storage devices, hold significant potential in various applications. Exploring advanced electrolytes beyond traditional electrolytes is essential for achieving stable high-voltage and low-temperature operations. Herein, a hybrid electrolyte with a high electrochemical stability window (3.29 V) and sufficient ionic conductivity (1.5 mS cm<sup>-1</sup> at -50 °C) is developed via hybridizing 8 m Ca(ClO<sub>4</sub>)<sub>2</sub>/H<sub>2</sub>O with acetonitrile (AN) diluent. The charged Ca<sup>2+</sup> cations anchor the oxygen atoms in H<sub>2</sub>O molecules, preventing them from being hydrogen acceptors. Meanwhile, the ClO<sub>4</sub> <sup>-</sup> anions weakly interact with hydrogen atoms, which ensures strong intramolecular O─H bonds in 8 m Ca(ClO<sub>4</sub>)<sub>2</sub>/H<sub>2</sub>O. The used AN can contribute to decreased salt dosage, without any compromise to electrochemical stability and safety. Furthermore, the AN with a higher donor number than ClO<sub>4</sub> <sup>-</sup> can replace the ClO<sub>4</sub> <sup>-</sup> in Ca<sup>2+</sup> solvation sheaths, which reduces Ca<sup>2+</sup>-ClO<sub>4</sub> <sup>-</sup> clusters, accordingly suppressing salt precipitation even at -50 °C. Resultantly, a symmetric supercapacitor assembled with 4.2 m Ca(ClO<sub>4</sub>)<sub>2</sub>/H<sub>2</sub>O-AN electrolyte presents high-voltage and temperature-adaptability features, with excellent rate capability and high long-term cycling stability from 25 to -50 °C at 2.3 V.