Electrolyte design strategies for next-generation supercapacitors and metal-ion batteries

Electrolytes, as the lifeblood of energy storage systems, play a pivotal role in determining the performance metrics of supercapacitors and metal-ion batteries, including energy density, power output, cycle life, and safety. This review presents a comprehensive analysis of composition–performance relationships across aqueous, organic, ionic liquid, and solid-state electrolyte systems, with particular emphasis on their adaptability challenges and innovative solutions for electric double-layer capacitors, pseudocapacitors, and lithium/sodium/potassium/zinc-ion batteries. For supercapacitor applications, the breakthroughs have been achieved through high-concentration electrolytes (e.g., Water-in-Salt systems), by which the voltage window is extended to 3.0 V, and through solid-state electrolytes that enable flexible device integration. Regarding metal-ion batteries,the synergistic effects of novel fluorinated solvents, multifunctional additives, and composite solid-state electrolytes are elucidated in enhancing interfacial stability and energy density, with energy densities exceeding 500 Wh/kg being achieved and capacity retention rates > 90% being maintained after 200 cycles. Furthermore, the transformative impact of AI-driven high-throughput screening on accelerating electrolyte molecular design is analyzed and forward-looking perspectives are provided on emerging technologies, including all-solid-state devices, biodegradable electrolytes, and multivalent ion transport systems. This work offers both theoretical foundations and practical design guidelines for next-generation energy storage systems with superior safety and energy density.