Eutectogel with (NH₄)₂SO₄-Based Deep Eutectic Solvent for Ammonium-Ion Supercapacitors

Abstract

The ammonium-ion supercapacitor (AISC) with nonmetal charge carriers exhibits merits of element abundance and compatibility with aqueous electrolytes. However, it still suffers from severe performance degradation at low temperatures. Herein, a novel deep eutectic solvent (DES) containing H2O, ethylene glycol, and (NH4)2SO4 is designed and shows a freezing point of −46.3 °C. The DES is further incorporated in poly­(vinyl alcohol)/gelatin gels to prepare a eutectogel that demonstrates favorable mechanical flexibility and a high ionic conductivity of 45.6 mS cm–1 at room temperature. Furthermore, the eutectogel also shows an excellent self-extinguishing property. The AISC consisting of an optimized eutectogel and carbon electrodes indicates remarkable cycling stability with ∼100% capacitance retention and ∼100% Coulombic efficiency after 30 000 charge–discharge cycles. Moreover, the flexible AISC also exhibits excellent electrochemical performance under harsh conditions, such as bending deformation, a damaged state, and low-temperature environments. Therefore, this work provides an innovative DES and a promising eutectogel platform for next-generation electrochemical energy storage systems.

A Comprehensive Review of Ammonium Ion Hybrid Supercapacitors: Exploring Recent Breakthroughs and Future Horizons

“…Current research on NH 4 + energy storage materials mainly includes several categories, including metal oxides, metal sulfides, MXene, LDH, and MOFs. These materials often possess advantageous traits such as open framework-type structures, layered diffusion channels, reversible redox chemistry, multiple chemical valence states, and distinctive morphological features. ,, While various electrode materials have been explored, they often exhibit shortcomings that can be mitigated through specialized modifications to enhance performance. Thus, a comprehensive review of existing research from both material science and electrochemical perspectives is crucial for gaining insights and driving future advancements in this field.…”