Highly productive production method for solar grade silicon using direct electrochemical reduction of silica and liquid alloy cathodes

2020 Fiscal Year Final Research Report

• Project/Area Number: 16H02410
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Metal making/Resorce production engineering
• Research Institution: Kyoto University
• Principal Investigator: Nohira Toshiyuki 京都大学, エネルギー理工学研究所, 教授 (00303876)
• Co-Investigator(Kenkyū-buntansha): 安田 幸司 京都大学, 工学研究科, 特定准教授 (20533665)
• Project Period (FY): 2016-04-01 – 2021-03-31
• Keywords: 太陽電池 / 溶融塩 / 電解還元 / シリコン / 液体合金カソード

Outline of Final Research Achievements

We studied a low-energy, low-cost, and high-productivity method to produce silicon for solar cells from high-purity silica. The electrochemical reduction method in molten salt was adopted as an alternative to the conventional carbothermic reduction, and the following results were obtained. (1) The mechanism of electrochemical reduction of SiO2 on liquid Zn electrode in molten CaCl2 was investigated. As the results of electrochemical measurement and sample analysis, we found that there existed a potential region where Zn-Si alloy was formed directly and a potential region where Zn-Si alloy was formed indirectly via Zn-Ca alloy. (2) Si precipitation from liquid Zn-Si alloy was investigated, which revealed that metallic impurities could be efficiently removed.

Free Research Field

溶融塩電気化学

Academic Significance and Societal Importance of the Research Achievements

溶融塩化カルシウム中におけるシリカの電解還元については、新規な太陽電池用シリコン製造法への応用が期待されてきたが、従来の固体電極を用いる方法では「低生産性」および「不純物混入しやすい」という課題があった。本研究により、どちらの課題も解決できる可能性が示された。特に、液体Zn-Si合金からのSi析出における金属不純物除去を実証したことは重要である。本研究がさらに発展すれば、社会的にニーズの高い太陽電池用シリコンの新規製造法の確立が期待できる。