Harmonizing Graphene Laminate Spacing and Zinc‐Ion Solvated Structure toward Efficient Compact Capacitive Charge Storage

Abstract Aqueous Zn‐ion hybrid capacitors (ZIHCs) present prominent potentials in flexible wearable electronics application scenarios due to their inherent high safety and low cost. Simultaneously, volumetric energy density is one of the crucial parameters to determine the lifespan of the wearable electronics, in which lightweight and miniaturization is a cardinal prerequisite for realistic application. In this work, an aqueous ZIHC is constructed by harmonizing interlayer spacing of the laminate graphene film and Zn‐ion solvation structure to improve the electrode space utilization. Laminate graphene film interspacing has been customized in the range of 0.72–0.81 nm via regulating the ratio of crumple graphene mediator, thereby optimizing the transport kinetics of large size hydrated Zn ions. Zn‐ion solvation structure is further tailored by introducing ZnCl 2 electrolyte salt to accouple such regulated laminar ionic transport channel. In a result, the thus‐derived ZIHC demonstrates an ultralong cycling lifespan of 100 000 cycles (93.9% capacitance retention), a preeminent volumetric capacitance (235.4 F cm −3 ), and a remarkable specific area capacitance contribution ( C ssa ≈ 72 µF cm −2 ). Quasi‐solid‐state ZIHC is assembled with ZnCl 2 solution‐filled polyacrylamide gel electrolyte to concurrently achieve a superior areal capacitance of 1227 mF cm −2 and great mechanical flexibility toward practical wearable application.