Su8000

The microstructure, morphology and crystallinity of the as-prepared CuO and CuO/NiO nanowires were analyzed by transmission electron microscopy (TEM, JEM-2100F CS STEM, JEOL, Japan), scanning electron microscopy (SEM, SU8000, JEOL, Tokyo, Japan), and X-ray diffraction (XRD), respectively. The CuO/NiO nanowires were assembled into coin cells as the anode for testing LIB performance. The assembling sequence from bottom to top is as follows: bottom stainless steel case, Li metal cathode, separator, CuO/NiO nanowires, spring, and top stainless steel case; the electrolyte is ethylene carbonate (EC)/diethyl carbonate (DEC) with 1 M LiPF6. The cycle tests of the anode materials were performed between 0.1–3 V under a constant current of 0.1 C (70 mA g⁻¹) at room temperature. For comparison, evolution of the morphology and microstructure of the CuO/NiO nanowires upon cycling were studied by TEM, where a constant current of 1 µA was employed for the formation process in the 1st cycle by Keithley 2400.

Characterization of the grown nanowires was conducted with FE-SEM (Hitachi SU8000, Tokyo, Japan), HR-TEM (JEOL JEM-2100F CS STEM, Tokyo, Japan), grazing angle XRD (Bruker D8 discover, Fitchburg, WI, USA), and XPS (PHI 5000 Versaprobe, ULVAC-PHI, Chigasaki, Japan). For the optical properties, PL (Horiba LabRam-HR, Longjumeau, France) measurements were conducted. For the electrical properties, we measured resistivity using a special method reported by Gu et al. [25 (link)]; this accurate method was designed for the resistivity of a single nanowire, eliminating possible errors, including contact resistances or Schottky contacts existing in two-probe measurements and four-probe measurements, respectively. To fabricate the nanodevice for the electrical measurements, the as-grown ITO NWs substrate was sonicated in deionized water for the separation of nanowires from the substrate; then droplets of solution containing ITO NWs were dripped on a previously prepared Si/SiO₂ wafer with four independent Ag electrodes. Each nanowire was linked to four independent electrodes with Pt via selective deposition by a focused ion beam (FIB, FEI Nova-200 NanoLab Compatible, Hillsboro, OR, USA). The fabrication process is shown in Supplementary Materials Figure S2.