Hierarchically assembled plasmonic Ni/Cu particles enabling highly conductive nickel current collectors for high-voltage all-printed microsupercapacitors

A printable metallic current collector is an indispensable requirement for on-chip integration of microsupercapacitors into electrical circuitry layouts. Yet, achieving high electrical conductivity and electrochemical stability simultaneously remains highly challenging. Here, we present a hierarchically assembled Ni/Cu particle architecture that enables highly efficient laser-based photothermal annealing, achieving a record-high electrical conductivity of 178,860 S m⁻¹ in printed Ni current collectors. The hierarchically structured Ni/Cu core/shell particles (H-NiCu Ps) enhance optical absorptivity and ensure loss-free thermal transport, thereby collectively promoting interparticle coarsening, Ni−Cu solid-solution formation, NiO nanocluster generation, and polymer graphitization. The resulting surface-conformal biphasic NiO/carbon passivation layer surrounding the fully interconnected metallic Ni framework affords exceptional electrochemical stability up to 2.5 V in ionic liquid-based microsupercapacitors (MSCs). The critical effectiveness of H-NiCu Ps in laser-driven photothermal annealing was verified through photothermal simulations supported by comparative experimental results. The H-NiCu MSC exhibits superior electrochemical performance in terms of capacitance, energy density, and power density, surpassing conventional, costly noble metal-based devices, including printed Ag-based and vacuum-deposited Au/Cr MSCs. This study presents a chemical design strategy for cost-effective, high-performance printable metallic current collectors, providing a practical route toward next-generation energy-storage-unit-integrated electronic systems.