A one-step room-temperature synthesis of Ni-based layered double hydroxide (Ni-LDH) thin films with intercalated ions and water molecules is achieved via O2 non-thermal plasma (NTP) processing of sol–gel precursors. This method directly yields a phase-pure hydrotalcite-like structure with high specific surface area and favorable ion transport pathways, eliminating conventional heating and activation steps. Electrochemical analyses reveal that the NTP-derived LDH films exhibit large charge storage capacity, rapid ion diffusion kinetics, low surface charge-transfer resistance, and competitive OER electrocatalytic performance. This low-temperature plasma-assisted route offers a scalable, low-carbon footprint strategy for fabricating high-performance LDH functional coatings for energy and OER applications.