Nanoscaling and alloying techniques for silicon-based materials are widely recognized as vital technological approaches to effectively address the challenges associated with volume expansion and poor conductivity in silicon anodes. Developing short process, cost-effective preparation methods and shape controllable silicon-based materials is expected to improve their cyclability. Herein, utilizing the superior electrical conductivity of copper metal and its stable alloy interaction with silicon, the present study introduced a simple synthetic process by incorporating nanoscale Cu 2 O into a SiO 2 dioxide matrix under a combination of hydrothermal reaction with Cu(NO 3 ) 2 as the copper source and further sintering treatment. Under the conditions of a Cu:Si molar ratio to 3:8 under 850 °C by 2.6 V of constant electrolsyis for 3 h, straight silicon nanowires with a cross-sectional distribution were obtained. The Cu 3 Si alloy particles were enriched around silicon nanowires. Experimental testing was conducted to evaluate the electrochemical storage capabilities of Cu 3 Si/Si nanowires, resulting in an initial specific capacity of 2630.7 mAh g -1 and an initial coulombic efficiency of 88.94%. After 100 charge-discharge cycles, the discharge specific capacity reached 1675.4 mAh g -1 , with a capacity retention rate of 66.20%. This work demonstrates the effectiveness of constructing a Cu 3 Si conductive network for solving the volume expansion and conductivity problems of Si and the distinctive Cu 3 Si/Si architecture offers an exemplary model for the design of silicon-based composite anodes for advanced lithium-ion batteries.
Molten salt electrolytic synthesis of silicon is identified as a potential industry method due to its thorough deoxidization of oxide and short-flow synthetic progress. However, figuring out a more efficient and sustainable strategy for the increase of the reduction process as well as the control of product morphology still needs endless research. In this study, benefiting from the high electrical conductivity of metallic silver and the easy separation of silver from silver-silicon alloys during the electrolysis of SiO 2 , metallic silver was introduced to electric-catalyze the production of silicon. Firstly, metallic silver was introduced into the silica matrix by a simple silver mirror reaction. Secondly, the mixed Ag\SiO 2 precursor was located at the cathode for molten salt electrolysis . Finally, silicon nanowires were herein achieved in molten NaCl–CaCl 2 . Mechanisms of metal Ag played during the electric-polarization process of silica and the electrochemical nucleation of silicon were further analyzed by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Field-Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra . The results demonstrate that Ag helps construct Si nanowires via a classic Ag-Si binary alloy-droplet process and provided quantitative guidance for the large-yield production of silicon nanowires via adding 0.08–0.17 g Ag versus 1 g SiO 2 , controlling the temperature at 850–900 °C and electrolysis voltage at 2.6–2.8 V (2.6V at first 1 h and 2.8V at last 5 h). The synthesized silicon nanowires present two types of linear structures based on two three-phase interlines (3PIs) models and a streamed long-straight nanowire is observed.
Xianwei Su,Xiaojia Shang,Yusi Che,Shaolong Li,Jianxun Song,Jilin He
Homogenous ZrC x O y powders have been successfully synthesized by in-situ electro-reduction of solid ZrO 2 –C composite precursors in molten CaCl 2 . The effect of applied cell voltage and molar ratio of ZrO 2 to C on preparation of ZrC x O y were investigated. The reduction pathway of the composite electrode was studied based on the analysis of intermediate products using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that ZrO 2 is firstly converted to CaZrO 3 . The resulting CaZrO 3 is then reduced to ZrC x O y . The ZrC x O y formation is dramatically influenced by electrolysis voltage and molar ratio of ZrO 2 to C: a higher cell voltage and lower molar ratio of the ZrO 2 to C are more preferable for the formation of ZrC x O y powder. Homogenous ZrC x O y powders with particle size of ~100 nm are synthesized by ZrO 2 /C starting elemental powders in CaCl 2 molten salt at 1123 K for more than 3 h, when the cell voltage is 3.0 V and the molar ratio of the ZrO 2 to carbon starting materials is 1:1.0.
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