3D Carbon Fiber Skeleton Film Modified with Gradient Cu Nanoparticles as Auxiliary Anode Regulates Dendrite‐Free, Bottom‐Up Zinc Deposition

Abstract Achieving stable Zn plating/stripping under high current density and large area capacity remains a major challenge for metal Zn anodes. To address this issue, common filter paper is utilized to construct 3D carbon fiber skeleton film modified with gradient Cu nanoparticles (CFF@Cu). The original zincophobic hydrophilic CFF is transformed into gradient zincophilic and reversed gradient hydrophilic composite, due to the gradient distribution of Cu nanoparticles. When CFF@Cu is placed above Zn foil as an auxiliary anode, Zn foil anode exhibits stable, reversible, and dendrite‐free Zn plating/stripping for 1200 h at 10 mA cm −2 and 2 mAh cm −2 , 2000 h at 2 mA cm −2 and 2 mAh cm −2 , 340 h at 10 mA cm −2 and 10 mAh cm −2 . Additionally, nucleation barrier of Zn, Zn 2+ transport and deposition kinetics are improved. The deposits on the Zn foil anode become homogeneous, dense, and fine. Side reactions and by‐products are effectively inhibited. The excellent performance is mainly attributed to the gradient zincophilic field in 3D CFF. A portion of Zn 2+ is captured by Cu and deposited within CFF@Cu from bottom to top, which reduces and homogenizes Zn 2+ flux on Zn foil, as well as weakens and homogenizes electric field on Zn foil.