4D printing strategies for adaptive flexible supercapacitors: Materials design, mechanisms and electrochemical performance

초록

The increasing demand for efficient, sustainable, and multifunctional energy storage systems has intensified research on advanced supercapacitors, particularly those based on four-dimensional (4D) printing electrodes. Unlike conventional 3D-printed supercapacitors, 4D-printed devices incorporate time-dependent structural adaptation in response to external stimuli, enabling dynamic shape reconfiguration during operation. State-ofthe-art devices have achieved an areal capacitance of 3.32 F cm-2, energy density of 92.88 mu Wh cm-2, and capacitance retention exceeding 90% after 5000 charge-discharge cycles. This review provides a comprehensive and mechanism-oriented assessment of recent advances in 4D-printed flexible supercapacitors-based nano-composites for next-generation energy storage devices. Unlike earlier reviews, this work explicitly correlates material design strategies with charge-transport mechanisms, ion-diffusion pathways, and interfacial and structural stability. The selection of functional materials including carbon-based nanomaterials, metal oxides and conductive hydrogels is key as they provide the desirable mechanical flexibility, balance flexibility with elec-trochemical function. Emerging directions, such as AI-assisted materials design, additive manufacturing, multi-material integration and long-term durability under cyclic transformations, and sustainable 4D-derived printing systems, are also discussed. This review highlights key achievements, identifies current limitations and discusses future directions in the interdisciplinary development of 4D-printed flexible supercapacitors, providing a foun-dation for next-generation intelligent energy storage systems.

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