Electrochemical power sources enabled by multi-ion carriers

The pursuit of high-performance, sustainable, and adaptable energy storage systems stands at the forefront of addressing the ever-growing demands of our modern world. Among the most compelling frontiers in this endeavour are electrochemical technologies empowered by multi-ion carriers, which transcend the intrinsic limitations of conventional single-ion systems. By harmonizing the transport and redox behaviour of diverse cations and anions, these systems give rise to novel mechanisms of charge balance, extended electrochemical stability windows, and cooperative redox pathways. This review offers a panoramic exploration of recent advances in multi-ion carrier-enabled electrochemical energy technologies, with a particular focus on hybrid batteries, capacitors, fuel cells, and redox flow batteries. Through these case studies, we elucidate how the interplay of multiple ions governs structure-function relationships and enhances overall electrochemical performance. Central to this discussion are the underlying working principles, representative device architectures, and the latest innovations in electrode and electrolyte materials. Special attention is devoted to the way multi-ion transport phenomena unlock new electrochemical landscapes, accelerating ion kinetics, stabilizing interphases, and enabling emergent pathways unavailable to single-ion systems. We further highlight forward-looking trends in hybrid ionic configurations, such as the integration of cations, co-transport of cation-anion pairs, and the engineering of aqueous-nonaqueous hybrid systems. In closing, we provide a critical assessment of the electrochemical advantages, scalability prospects, and practical challenges that lie ahead, ranging from kinetic harmonization across multiple ions to scalable device fabrication and the mitigation of complexity-driven safety concerns. By weaving together insights from materials science, electrochemistry, and systems engineering, this review lays a foundation for the rational design of next-generation multi-ion electrochemical energy devices that promise to redefine the limits of performance and versatility.