Instantaneous vapor-liquid-solid growth of amorphous SiO2 nanowires within a local-equilibrium plasma and the optimized lithiation/delithiation activity

Highlights: • Random Ni@a.-SiO2 NWs are synthesized through an instantaneous VLS growth. • The energy state of working arc plasma are diagnosed by real-time OES. • Ni@NiO@a.-SiO2 NWs is obtained by controlling Ni to convert to Ni@NiO in air. • Optimal Ni@NiO@SiO2 a.-NWs exhibit better cycling stability and rate capability. Amorphous SiO2 (a.-SiO2) species is a promising anode material for lithium ion batteries (LIBs) due to its high theoretical capacity (1965 mAh g⁻¹) and abundant resource. One-dimensional a.-SiO2 nanowires (NWs) can provide efficient pathways for charge transport/diffusion and fast strain release during reciprocating lithiation/delithiation. Herein, an instantaneous vapor–liquid-solid (VLS) growth of a.-SiO2 NWs was performed in a high-temperature DC arc plasma using metal Ni as the catalyst. The Ni@a.-SiO2 NWs contain a high content of Ni (26.68 wt%) at the tips of NWs, allowing the synthesis of two derived products of Ni@NiO@a.-SiO2 NWs and NiO@a.-SiO2 NWs via an oxidation treatment in flowing air. A real-time optical emission spectroscopy (OES) diagnosis was carried out on the working arc plasma. This indicates the electron temperature (Te) of 8088.3 K and electron density (ne) of 1.7 × 10¹⁴ cm⁻³ within the local-equilibrium plasma. Electrochemical properties of typical products show the optimization available by control of the core-shell structure attached at the tip of nanowire. In other words, the Ni@NiO@a.-SiO2 NWs exhibited a higher specific capacity of up to 996.8 mAh g⁻¹ after 200 cycles with Coulombic efficiency of 99.5%, and a better rate capability at an intense current of 2.0 A·g⁻¹.