Electrolytic production of silicon

Elwell, D.; Rao, Gopalakrishna M.

doi:10.1007/bf01016199

Cited by 80 publications

(50 citation statements)

References 33 publications

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“…The corresponding peak current densities for Si deposition are -1.742 A cm -2 and -1.521 A cm -2 in the solid curve (SiCl 4 ) and the broken curve (K 2 SiF 6 ), respectively. Since the peak current density is proportional to the Si ion concentration, 13 we estimated that the concentration of SiF 6 2-ions was 2.30 mol%. Thus, a melt with the optimum Si ion concentration (2.0-3.5 mol%) for the electrodeposition of compact films was successfully prepared.…”

Section: Injection Of Siclmentioning

confidence: 99%

“…The standard Gibbs energy changes for the reactions of chlorides and F 2 gas to form fluorides and Cl 2 gas. 17 ) unless CC License in place (see abstract These thermodynamic calculations suggest that the SiCl 4 gas introduced into the KF-KCl melt is expected to dissolve to produce SiF 6 2− complex ions, which are highly stable in molten salts.…”

Section: Thermodynamic Calculationmentioning

confidence: 99%

“…Conventionally, either K 2 SiF 6 or the anodic dissolution of a Si rod was utilized as the supply of Si ions. However, the low-cost preparation of K 2 SiF 6 and Si rods of solar-grade purity is difficult.…”

mentioning

confidence: 99%

“…The electrodeposition of crystalline Si using high-temperature molten salts has been reported by several researchers since the 1970's. [1][2][3][4][5][6][7][8][9][10] The use of fluoride-based molten salts, such as LiF-KF and LiF-NaF-KF, is effective for obtaining compact and smooth Si films. 1,2,5,9,10 However, previous investigations that employed fluoride-based molten salts found that the low solubility of LiF and NaF in water makes the removal of the salt that adheres to the deposited Si a major problem.…”

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confidence: 99%

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Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source

Yasuda

Maeda

Hagiwara

et al. 2016

J. Electrochem. Soc.

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The electrodeposition of Si was investigated in a molten KF–KCl salt mixture (eutectic composition, 45:55 mol%) after the introduction of SiCl4 to demonstrate a new production method for solar cell substrates. Gaseous SiCl4 was introduced directly into the molten salt at 1023 K by a vapor transport method using Ar as a carrier gas. The dissolution efficiency of SiCl4 exceeded 80% even when a simple tube was used for bubbling. Galvanostatic electrolysis was conducted at 923 K on a Ag substrate at 155 mA cm−2 for 20 min in the molten KF–KCl salt mixture after the dissolution of 2.30 mol% SiCl4. Although a compact Si layer was formed, its smoothness was inferior to that obtained from the melt after the addition of K2SiF6. The molar fraction of the fluoride anion is suggested as one of the factors affecting the morphology of the deposits.

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Section: Injection Of Siclmentioning

confidence: 99%

Section: Thermodynamic Calculationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source

Yasuda

Maeda

Hagiwara

et al. 2016

J. Electrochem. Soc.

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“…Among the processes under investigation, molten salt electrolysis is one of the most extensively investigated ones, [2][3][4][5][6][7][8][9][10][11][12][13] which allows reduction of the economic cost and energy consumption, and basically has a sufficient productivity. In most of these investigations, however, Si was electrodeposited in the solid state, which tends to causes contamination from the melt component.…”

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confidence: 99%

Electrorefining of Silicon Using Molten Salt and Liquid Alloy Electrodes

Oishi

Koyama

Tanaka

2016

J. Electrochem. Soc.

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A new Si refining process, which employs molten salt electrolysis and precipitation steps, is proposed and tested. In this process, impure Si is added to a Cu-Si liquid alloy anode, and the electrorefining of Si is conducted using an Al-Si liquid alloy cathode in a fluoride-based molten salt. From the obtained Si-enriched Al-Si alloy, purified Si is obtained by precipitation. A glow discharge mass spectrometry analysis revealed that the proposed process can effectively remove the dominant impurities such as Fe, Mn, Ti and V from metallurgical grade Si (98-99% purity). A preliminary electrolysis using Si cells recovered from a commercial photovoltaic module, of which the dominant impurities are Ag, Al and Na, showed that the present process is also applicable for Si recycling from waste photovoltaic modules. In the past few decades, demands for photovoltaic (PV) cells have significantly increased. Although many types of PV cells have been invented and/or produced, crystalline silicon PV cells account for most of the produced PV cells at present, because of their high energy conversion efficiency, stability and safety. In addition, silicon is the second most abundant element in the earth's crust by mass, which is really important when one considers the rapid spread of PV cells today and in the near future. On the other hand, one of the disadvantages of the crystalline silicon PV cells is economic cost, especially, the cost to produce pure silicon; solar-grade silicon (SoG-Si, 6N:99.9999% purity) is regarded as one of the most serious problems. So far, SoG-Si has been supplied from the semiconductor industry which uses higher purity silicon (SEG-Si, 11N:99.999999999% purity) commonly produced by the so-called Siemens process. Currently, SoG-Si is also produced independently by the Siemens-based process, which is specialized for the SoG-Si production. Although this process is advantageous for the purity of the Si product, it is rather costly and energy consuming. Thus, a more cost and energy-effective process to produce SoG-Si is required.One of the other important issues we need to consider is how to handle the waste PV modules in the near future.1 As already mentioned, silicon itself is an abundant element, and the recycling of normal grade silicon might not seem to be important. The SoG-Si, however, requires huge economic and energy costs to produce, and it is better to recycle from this view point as well as the point of reducing environmental pollution due to the hazardous metals contained in the PV modules like Pb. Another aspect the authors focused on is the potential utilization of the Si cells recovered from waste PV modules as secondary resources for the SoG-Si production. Since the impurities in the Si cells are basically limited to intentionally added ones during the production steps, target elements which should be removed are also limited compared to that in the metallurgical grade Si (MG-Si, the feed material for the conventional SoG-Si production).Based on this background, a number of new processes f...

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Electrochemical Formation of Compounds with Si‐Si Bonds (Including Elemental Silicon)

Hengge¹

1991

Inorganic Reactions and Methods

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Electrolytic production of silicon

Cited by 80 publications

References 33 publications

Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source

Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source

Electrorefining of Silicon Using Molten Salt and Liquid Alloy Electrodes

Electrochemical Formation of Compounds with Si‐Si Bonds (Including Elemental Silicon)

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Electrolytic production of silicon

Cited by 80 publications

References 33 publications

Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl4as Si Source

Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl4as Si Source

Electrorefining of Silicon Using Molten Salt and Liquid Alloy Electrodes

Electrochemical Formation of Compounds with Si‐Si Bonds (Including Elemental Silicon)

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Product

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Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source

Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl₄as Si Source