3D printing aqueous batteries for flexible electronics: From materials and components to integrated devices

Benefiting from the intrinsically high safety, overall performance, and environmental compatibility in targeted applications, aqueous batteries have emerged as promising power sources for next-generation flexible and wearable electronics. However, their application potential remains largely constrained by insufficient electrochemical performance, inadequate mechanical compliance, and limited design freedom. 3D printing enables programmable, multi-material, and architecturally complex battery construction, offering a powerful route to address these limitations. Nevertheless, applying efficient 3D-printed aqueous batteries into flexible electronics requires a clear understanding on the interplays among the printing processes, materials, and structural design, as well as the end performance. In this review, a systematic framework is established to correlate 3D printing techniques with material selection, structural engineering, and integration of aqueous batteries in flexible electronics. First, representative 3D printing techniques are examined in terms of their key characteristics and applicability. The impacts of functional materials and components, including current collectors, electrolytes, and electrodes, together with 1D, 2D, and 3D structural designs enabled by 3D printing, on the electrochemical performance and mechanical adaptability are comprehensively discussed. Finally, integration strategies and representative applications of 3D printed aqueous batteries in flexible electronics are reviewed, and the remaining challenges and potential future directions are outlined.