Porosity and Conductivity Dual‐Gradient Design on Ultrathin 3D Nanofibrous Anode for Flexible Zn‐Ion Batteries

Abstract Flexible Zn‐ion batteries (ZIBs) have been regarded as a promising energy storage solution for flexible electronics. However, the challenges of dendrite growth due to uneven current density distribution and limited anode flexibility have impeded their practical application. Herein, a flexible 3D zinc anode with a dual gradient in porosity and conductivity is presented. This dual‐gradient nanofibrous anode exhibits exceptional flexibility and durability, showing less than a 10% change in resistance after 15 000 bending cycles. The vertical gradient distribution in conductivity promotes preferential zinc deposition at the bottom section, while the gradient in porosity facilitates Zn 2 ⁺ ion migration and ensures timely replenishment of the inner space of the membrane. The combination of the 3D structure and dual‐gradient design fosters bottom‐up zinc deposition, effectively preventing dendrite formation. Symmetric cells with this dual‐gradient anode demonstrate outstanding cycling stability, maintaining more than 410 h of operation at a current density of 1 mA cm −2 for 1 mA h cm −2 , surpassing reference samples and most previously reported 3D zinc anodes. The quasi‐solid‐state ZIBs assembled with this dual‐gradient anode exhibit excellent stability under various mechanical deformations. These 3D nanofibrous anodes with dual‐gradient designs hold great promise for advancing the practical application of flexible Zn‐ion batteries.