Thin-Film Electrode Design for High Volumetric Electrochemical Performance Using Metal Sputtering-Combined Ligand Exchange Layer-by-Layer Assembly

The design of electrode with high volumetric performance in energy storages still remains as a significant challenge because it simultaneously requires a high packing density of active materials for high energy density and a conductive porous structure for facile charge transfer. Here, a novel assembly process is introduced for thin-film anodes for Li-ion battery with a high volumetric energy density and rate performance by systematically controlling the interfacial structure between metal-oxide nanoparticles and/or metal clusters. For this study, oleic-acid-stabilized Fe₃O₄ nanoparticles are layer-by-layer assembled with small organic molecules through a ligand exchange reaction, which enable a high packing density. During layer-by-layer deposition, periodic Pt-sputtering onto multilayers significantly reduces the internal resistance of the electrodes but maintains the nanopores formed among the nanoparticles. The resulting anode exhibits an extremely high volumetric capacity of ≈3195 mA h cm⁻³ and rate performance, which are far superior to that reported for Li-ion battery anodes. Additionally, all components in the electrodes have a stable covalent bond network between the metal atom and the amine group of organic molecule linker, allowing good cycle retention. This approach can be widely applied to the fabrication of various nanoparticle-based electrodes, enabling maximum charge storage performance in confined volumes.