Advances in Ammonium Ion Supercapacitors Based on Two‐Dimensional Electrode Materials: A Comprehensive Review

Supercapacitors (SCs) are rapidly emerging as an essential class in future energy storage devices (ESDs) because of their exceptional power density, rapid charge–discharge kinetics, extended cycle life, and environmental sustainability. Among various electrolyte innovations, ammonium (NH 4 + ) ions have recently garnered significant attention due to their inherent safety, fast transport properties, and sustainable resources. However, the development of high‐performance NH 4 + ‐based SCs remains in its early stages. The strategic selection and design of compatible two‐dimensional (2D) electrode materials, such as MXenes, graphene, transition metal dichalcogenides (TMDs), and metal–organic frameworks (MOFs), etc., are critical to unlocking their full potential. This review provides a comprehensive analysis of NH 4 + ion electrolytes and their synergy with 2D electrode materials for advanced SCs. We systematically summarize recent advances in the rational design of 2D materials and evaluate their compatibility with NH 4 + electrolytes to enhance charge storage performance. Furthermore, we offer critical insights into material engineering strategies aimed at achieving superior electrochemical properties in NH 4 + ‐based SCs. Ultimately, this work aims to serve as a foundational reference for guiding the selection and optimization of 2D materials and NH 4 + electrolytes, thereby accelerating the development of next‐generation high‐performance SCs.