Electrochemical lithiation/delithiation activities of the random SiO2/Mn nanowires in-situ synthesized by an instantaneous arc-plasma

Abstract

Catalyst (Mn)-induced growth of random SiO2 nanowires (NWs) was in-situ accomplished by direct current (DC) arc-discharge plasma. An instantaneous vapor-liquid-solid (VLS) mechanism was proposed for the formation of the SiO2/Mn NWs, evidenced by optical emission spectroscopy (OES) diagnoses on the high-temperature plasma and analyses of Gibbs free energies on the basis of Ellingham diagram. Electrochemical behaviors of SiO2/Mn NWs electrode showed a specific capacity of 1333.6 mAh⋅g−1 at the current density of 0.1 A g−1, with a Columbic efficiency of 98.1% after 100 cycles. The diffusion of Li+ ions in the SiO2/Mn NWs electrode was further promoted by consecutive cycling, which was attributed to the ionically conductive products of Li2O and lithium silicate in the SEI layer, revealed by the Li+ diffusion coefficient (2.64 × 10−17 cm2 s−1) in the initial electrode and a varied value of 8.97 × 10−17 cm2 s−1 in the subsequently cycled electrode. The excellent cycling stability of the SiO2/Mn NWs electrode was ascribed to the random SiO2 nanowires with one-dimensional structure, the uniformly embed Si species in the buffer matrix by cycling, and the positive contribution from the residual catalyst of Mn nanoparticles. The unique morphology and composition of the SiO2/Mn NWs brought in an excellent rate capability, i.e. the reversible capacity of 1076.4 mAh⋅g−1 at a current density of 0.1 A g−1 was adequately recovered after suffering from intense current impacts up to 2.0 A g−1.