Synergistic Gradient Design of a Sandwich‐Structured Heterogeneous Anode for Improved Stability in Aqueous Zinc‐Ion Batteries

Abstract Aqueous Zn‐ion batteries provide a low‐cost energy storage solution but face challenges such as dendrite formation and interface instability, which become more pronounced at high currents and capacities. Herein, a scalable sandwich‐structured heterogeneous anode is proposed for aqueous zinc batteries that integrate three functionally synergistic layers. A robust 3D ZnO@C substrate (from calcined Bio‐MOF‐100, BMC) with dense nucleation sites guides orderly Zn deposition, while a controllable pre‐deposited Zn intermediate layer precisely regulates Zn 2 ⁺ flux. An artificial indium‐based protective top‐layer that chemically isolates the active Zn from the electrolyte, effectively suppresses interfacial corrosion, and enhances interlayer contact to minimize impedance while maintaining structural integrity during cycling. The structural synergies endow the symmetric cell with an ultra‐long cycle life exceeding 2000 h and stable Zn plating/stripping at a remarkable depth of discharge (76%) under high current/areal capacity conditions (6 mA cm −2 /12 mAh cm −2 ). Additionally, the BMC@Zn@In//(NH 4 ) 2 V 10 O 25 ·8H 2 O full battery achieves a stable lifespan of 5000 cycles, while the BMC@Zn@In//activated carbon hybrid supercapacitor demonstrates an impressive cycle life of 16 000 cycles. This study identifies a synergistic mechanism for an ultra‐stable Zn anode with promising applications in aqueous Zn‐ion batteries.