Emerging non-carbon cathodes for advanced mild aqueous Zn-ion capacitors

Conventional Zn-ion capacitors (ZICs) predominantly utilize carbonaceous cathodes in carbon//Zn configurations, leveraging surface-dominated ion adsorption/desorption to deliver high power density and prolonged cycle life. As carbon-based systems approach their performance ceiling, cathode evolution is increasingly pivoting toward non-carbon materials. While prior reviews have acknowledged their existence, a comprehensive review remains absent. Herein, this review systematically charts the paradigm shift to non-carbon cathodes, dissecting their Zn-ion storage mechanisms and performance landscapes. Emerging non-carbon cathodes are categorized as pseudocapacitive-type (MXenes, transition metal compounds, organics, etc.) and battery-type (V/Mn-based compounds, Prussian blue analogs), with rigorous evaluation of voltage window, specific capacitance, energy/power density, rate capability, and cycle stability. Persistent scientific challenges, including restricted theoretical capacitance, suboptimal electrolyte compatibility, material dissolution, structural degradation, and sluggish storage kinetics, are critically discussed. The review further analyzes optimization strategies across material design, structural modulation, and electrolyte formulation refinement to solve these challenges. Looking forward, we propose targeted research priorities to propel non-carbon cathodes beyond current constraints. This review underscores the translational potential of non-carbon cathodes in redefining the performance frontiers of mild aqueous ZICs, ultimately harmonizing high energy/power density, ultrafast storage kinetics, and robust durability.