Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

Zhuk, Sergey I.; Isaev, Vladimir A.; Grishenkova, Olga V.; Исаков, А. А.; Apisarov, P Alexey; Zaykov, P Yurii

doi:10.2298/jsc160712109z

Cited by 20 publications

(19 citation statements)

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“…However, due to the similar values of the bond energy, this transformation is likely to be retarded. Such a chemical reaction was reported 21 during the cathode process when studying the mechanism of the silicon electroreduction in KF−KCl−K 2 SiF 6 melts, which was assigned to SiO 2 dissolution.…”

Section: The Silicon Complexes In Kf−kcl−k 2 Sif 6 −Siomentioning

confidence: 75%

DFT-based calculations of silicon complex structures in the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts

Vorob’ev

Исаков

Галашев

et al. 2019

JSCS

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The length and energy of bonds in the complex anions of silicon formed in KF−KCl−K 2 SiF 6 and KF−KCl−K 2 SiF 6-SiO 2 melts were evaluated using the method of first-principles molecular dynamics, accomplished by means of the Siesta program. The effect of K + (from the second coordination sphere) on the stability of these complexes was studied. The bond lengths in the silicon complexes was found to change with increasing amount of the potassium ions. It was established that the following complexes [SiO 4 ] 4-, [SiO 3 F] 3and [SiF 6 ] 2are the most stable in KF−KCl−K 2 SiF 6 and KF−KCl-K 2 SiF 6-SiO 2 melts. The [SiO 4 ] 4and [SiF 6 ] 2complexes are thermally stable in the molten salt in the temperature range of 923-1073 K, whereas the [SiF 7 ] 3structure, which is typical for the lattice of crystalline K 3 SiF 7 , is unstable in this temperature range. In the KF−KCl−K 2 SiF 6 −SiO 2 melts, conditions above 1043 K were created allowing the transformation of [SiО 3 F] 3into [SiO 4 ] 4-. Within the studied temperature mode, the Si-F bond length is in the range 1.5-1.9 Å and the Si-O bond lengths is 1.5-1.7 Å. The obtained results are in a good agreement with in situ data of Raman spectroscopy for the KF−KCl−K 2 SiF 6 and KF-KCl-K 2 SiF 6-SiO 2 melts.

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Section: The Silicon Complexes In Kf−kcl−k 2 Sif 6 −Siomentioning

confidence: 75%

DFT-based calculations of silicon complex structures in the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts

Vorob’ev

Исаков

Галашев

et al. 2019

JSCS

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“…One of the cheapest and promising methods for producing nanosized silicon is electrolytic reduction from molten salts. To date, many studies have been carried out aimed at the electrolytic production of silicon from various molten electrolytes with K 2 SiF 6 , Na 2 SiF 6 , SiO 2 , and SiCl 4 additives in a temperature range mainly from 550 • C to 750 • C [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. All these studies show the fundamental possibility of using electroreduction for the production of silicon deposits of various morphologies, including continuous coatings up to 1 mm thick, submicron films (0.5-1 µm), micro-sized dendrites, nano-and micro-sized disordered fibers.…”

Section: Introductionmentioning

confidence: 99%

“…One of the most promising electrolytes for silicon production is the KCl-KF melt with a KF molar fraction of up to 66% [27][28][29][30][31], which is a good solvent for K 2 SiF 6 and SiO 2 and is water soluble. However, this system also has a number of disadvantages, including relatively high aggressiveness of KF to reactor materials, the need to remove impurities such as H 2 O and HF from KF when preparing a molten KCl-KF mixture, and a good solubility of oxides.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Synthesis of Nano-Sized Silicon from KCl–K2SiF6 Melts for Powerful Lithium-Ion Batteries

et al. 2021

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Currently, silicon and silicon-based composite materials are widely used in microelectronics and solar energy devices. At the same time, silicon in the form of nanoscale fibers and various particles morphology is required for lithium-ion batteries with increased capacity. In this work, we studied the electrolytic production of nanosized silicon from low-fluoride KCl–K2SiF6 and KCl–K2SiF6–SiO2 melts. The effect of SiO2 addition on the morphology and composition of electrolytic silicon deposits was studied under the conditions of potentiostatic electrolysis (cathode overvoltage of 0.1, 0.15, and 0.25 V vs. the potential of a quasi-reference electrode). The obtained silicon deposits were separated from the electrolyte residues, analyzed by scanning electron microscopy and spectral analysis, and then used to fabricate a composite Si/C anode for a lithium-ion battery. The energy characteristics of the manufactured anode half-cells were measured by the galvanostatic cycling method. Cycling revealed better capacity retention and higher coulombic efficiency of the Si/C composite based on silicon synthesized from KCl–K2SiF6–SiO2 melt. After 15 cycles at 200 mA·g−1, material obtained at 0.15 V overvoltage demonstrates capacity of 850 mAh·g−1.

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“…5-8. Electrodeposition from molten salts is a promising method for producing thin silicon films due to the simplicity of the process, low capital and operating costs. [9][10][11][12][13][14][15][16][17][18][19] In addition, high deposition rates of continuous silicon layers and the ability to control the structure and morphology of films are advantages of this technique.…”

Section: Introductionmentioning

confidence: 99%

Electrodeposition of aluminum-doped thin silicon films from a KF-KCl-KI-K2SiF6-AlF3 melt

et al. 2021

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Cyclic voltammetry, chronoamperometry, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy were used to study the regularities of silicon and aluminum co-deposition on glassy carbon from KF-KCl (2:1) - 75 mol% KI - 0.15 mol% K2SiF6 - (up to 0.15 mol%) AlF3 melts at 998 K. Cyclic voltammograms demonstrated the presence of only one cathodic peak (or nucleation loop at a low reverse potential) and the corresponding anodic peak. The cathodic peak shifted in the cathodic direction with a decrease in the concentration of aluminum ions in the melt or an increase in the scan rate. The Scharifker - Hills model was used to analyze potentiostatic current density transients and estimate the values of the apparent diffusion coefficient and the number density of nuclei. The morphology and elemental analysis of the samples obtained during potentiostatic and galvanostatic deposition for 30-60 s were studied. Continuous thin silicon films doped with aluminum were obtained under galvanostatic conditions.

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Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

Cited by 20 publications

References 1 publication

DFT-based calculations of silicon complex structures in the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts

DFT-based calculations of silicon complex structures in the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts

Electrochemical Synthesis of Nano-Sized Silicon from KCl–K2SiF6 Melts for Powerful Lithium-Ion Batteries

Electrodeposition of aluminum-doped thin silicon films from a KF-KCl-KI-K2SiF6-AlF3 melt

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