Electrical conductivity, mechanical flexibility, and large electroactive surface areas are the most important factors in determining the performance of various flexible electrodes in energy storage devices. Herein, a layer‐by‐layer (LbL) assembly‐induced metal electrodeposition approach is introduced to prepare a variety of highly porous 3D‐current collectors with high flexibility, metallic conductivity, and large surface area. In this study, a few metal nanoparticle (NP) layers are LbL‐assembled onto insulating paper for the preparation of conductive paper. Subsequent Ni electroplating of the metal NP‐coated substrates reduces the sheet resistance from ≈103 to <0.1 Ω sq−1 while maintaining the porous structure of the pristine paper. Particularly, this approach is completely compatible with commercial electroplating processes, and thus can be directly extended to electroplating applications using a variety of other metals in addition to Ni. After depositing high‐energy MnO NPs onto Ni‐electroplated papers, the areal capacitance increases from 68 to 811 mF cm−2 as the mass loading of MnO NPs increases from 0.16 to 4.31 mg cm−2. When metal NPs are periodically LbL‐assembled with the MnO NPs, the areal capacitance increases to 1710 mF cm−2.

Highly flexible and porous metallic papers with bulk metallic conductivity and large surface areas are prepared using a metal nanoparticle (NP) assembly‐induced electroplating approach by Seung Woo Lee, Jinhan Cho, and co‐workers in article number 2007579. High‐energy pseudocapacitive NPs and conductive metal NPs are also layer‐by‐layer‐assembled onto the 3D porous metallic paper, which significantly increases the areal capacitance of metallic paper‐based supercapacitor electrode.