A method for preparing silicon by molten salt electrolysis

Abstract

The invention relates to a method for preparing silicon by molten salt electrolysis. According to the method, carbon, silicon or metal is used as a cathode, a carbon anode or inert anode is utilized to carry out electrolysis in a molten salt system. The invention is characterized in that silicon dioxide can be directly dissolved in the molten salt system, thereby being convenient for continuous electrolysis of silicon. The product of electrolysis can be a simple substance silicon or a silicon composite material. The silicon or silicon composite material obtained by electrolysis can be used as a negative pole material of a battery, and can also be used in the fields of electronics, semiconductors and the like. Besides, the method can also be used for removing impurity silicon in aluminum electrolysis.

Description

Technical field

[0001] The present invention relates to a production method of Si, which uses dissolved SiO 2 The molten salt system is directly electrolyzed to obtain Si, which is characterized by 2 It has good solubility and can be used for continuous electrolysis in industrial production. It has the advantages of simple and convenient process, controllable Si production speed and product morphology, high purity of obtained Si, and reduced process flow. The prepared silicon can be used in various fields such as battery anode materials, electronics, light-emitting devices, photovoltaics, etc., and belongs to the technical field of non-metal molten salt electrolysis. (Especially related to various technical fields such as chemical industry, metallurgical industry and molten salt electrolysis) Background technique

[0002] As a negative electrode material for lithium-ion batteries, silicon has the advantage of high capacity and broad application prospects. In addition, the produc...

Examples

Embodiment 1

[0032] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (55%) KF (42%) AlF 3 (3%)SiO 2 ; The electrolysis temperature is 720℃; carbon is the cathode and anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.5A / cm 2 . The cell voltage in the electrolysis process is stable at 1.4V, according to the SiO in the molten salt 2 Replenish SiO in time 2 , SiO 2 Dissolve quickly. A silicon wire with a purity of 98.9 wt% is obtained by electrolysis, the silicon wire has a morphological diameter of 150 nm, a length of 3-10 μm, and contains 1 wt% of linear micron silicon carbide. The SEM image of the silicon obtained by electrolysis in Example 1 is as figure 1 Shown, where, figure 1 A: ×10000 times; figure 1 B: ×20000 times; figure 1 C: ×90000 times. The cell voltage change in the silicon electrolysis process in Example 1 is as follows figure 2 Shown.

Embodiment 2

[0034] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (55%) NaF (42%) AlF 3 (3%)SiO 2 ; The electrolysis temperature is 750℃; carbon is the cathode, alloy is the inert anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.2A / cm 2 . During the electrolysis process, the cell voltage was stable at 1.4V, and silicon nanowires and silicon nanofibers were obtained by electrolysis, with a purity of 99.2% by weight.

Embodiment 3

[0036] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (60%) KF (38%) AlF 3 (2%)SiO 2 ; The electrolysis temperature is 800℃; carbon is the cathode and anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.5A / cm 2 . During the electrolysis process, the cell voltage was stable at 1.4V, and nano silicon particles were obtained by electrolysis, with a purity of 99.8 wt%.

Technical field

[0001] The present invention relates to a production method of Si, which uses dissolved SiO 2 The molten salt system is directly electrolyzed to obtain Si, which is characterized by 2 It has good solubility and can be used for continuous electrolysis in industrial production. It has the advantages of simple and convenient process, controllable Si production speed and product morphology, high purity of obtained Si, and reduced process flow. The prepared silicon can be used in various fields such as battery anode materials, electronics, light-emitting devices, photovoltaics, etc., and belongs to the technical field of non-metal molten salt electrolysis. (Especially related to various technical fields such as chemical industry, metallurgical industry and molten salt electrolysis) Background technique

[0002] As a negative electrode material for lithium-ion batteries, silicon has the advantage of high capacity and broad application prospects. In addition, the produc...

Examples

Embodiment 1

[0032] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (55%) KF (42%) AlF 3 (3%)SiO 2 ; The electrolysis temperature is 720℃; carbon is the cathode and anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.5A / cm 2 . The cell voltage in the electrolysis process is stable at 1.4V, according to the SiO in the molten salt 2 Replenish SiO in time 2 , SiO 2 Dissolve quickly. A silicon wire with a purity of 98.9 wt% is obtained by electrolysis, the silicon wire has a morphological diameter of 150 nm, a length of 3-10 μm, and contains 1 wt% of linear micron silicon carbide. The SEM image of the silicon obtained by electrolysis in Example 1 is as figure 1 Shown, where, figure 1 A: ×10000 times; figure 1 B: ×20000 times; figure 1 C: ×90000 times. The cell voltage change in the silicon electrolysis process in Example 1 is as follows figure 2 Shown.

Embodiment 2

[0034] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (55%) NaF (42%) AlF 3 (3%)SiO 2 ; The electrolysis temperature is 750℃; carbon is the cathode, alloy is the inert anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.2A / cm 2 . During the electrolysis process, the cell voltage was stable at 1.4V, and silicon nanowires and silicon nanofibers were obtained by electrolysis, with a purity of 99.2% by weight.

Embodiment 3

[0036] A method for preparing silicon by molten salt electrolysis, characterized in that the composition of the molten salt system is (60%) KF (38%) AlF 3 (2%)SiO 2 ; The electrolysis temperature is 800℃; carbon is the cathode and anode, the pole distance is 2cm; the electrolysis current density is controlled at 0.5A / cm 2 . During the electrolysis process, the cell voltage was stable at 1.4V, and nano silicon particles were obtained by electrolysis, with a purity of 99.8 wt%.

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