Dilute Aqueous-Aprotic Hybrid Electrolyte Enabling a Wide Electrochemical Window through Solvation Structure Engineering

Shuilin Wu, Bizhe Su, Mingzi Sun, Shuai Gu, Zhouguang Lu, Kaili Zhang, Denis Y.W. Yu, Bolong Huang, Pengfei Wang, Chun Sing Lee, Wenjun Zhang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

7 Citations (Scopus)

Abstract

The application of superconcentrated aqueous electrolytes has shown great potential in developing high-voltage electrochemical double-layer capacitors (EDLCs). However, the broadening of the electrochemical window of such superconcentrated electrolytes is at the expense of their high cost, low ionic conductivity, high density, and narrow operating temperature range. Herein, the electrochemical window of water (>3 V) at low salt concentration (3 m) is expanded by using an aprotic solvent, i.e., trimethyl phosphate (TMP), to regulate the solvation structure of the electrolyte. Benefiting from the low salt concentration, such electrolyte is simultaneously featured with high ionic conductivity, low density, and wide temperature compatibility. Based on the dilute hybrid electrolyte, EDLCs constructed by using porous graphene electrodes are able to operate within an enlarged voltage range of 0–2.4 V at a wide range of temperatures from −20 to 60 °C. They also present excellent rate capability and cycle stability, i.e., 83% capacitance retention after 100 000 cycles. Density functional theory calculations verify that TMP induces a significant electronic modulation for the bonding environment of the electrolyte. This enables the stronger binding of Na+–H2O with freely migrating TMP to expand the voltage window to exceed the potential limitation of aqueous electrolytes.

Original languageEnglish
Article number2102390
JournalAdvanced Materials
Volume33
Issue number41
DOIs
Publication statusPublished - 14 Oct 2021

Keywords

  • aqueous supercapacitors
  • hybrid electrolytes
  • solvation structures

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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