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A system for in-situ electrocatalytic molten salt electrolysis synthesis of silicon nanofibers by diaphragm method

A molten salt electrolysis and silicon nanotechnology, applied in diaphragms, electrolysis components, electrolysis processes, etc., can solve the problems of difficulty in obtaining high-purity silicon nanofibers, difficulty in controlling the growth of silicon nanofibers, and reducing the purity of nanofibers, and achieve production costs. Low, easy to industrialize production, high conversion rate

Active Publication Date: 2022-01-18
ZHEJIANG UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although silicon nanofibers are electrolytically grown under the protection of nitrogen or argon atmosphere, the anode reaction is an oxygen evolution reaction, and the evolved oxygen will affect the growth of silicon nanofibers at the cathode, reduce the purity of nanofibers, and reduce the length of nanofibers
Using a catalyst to compact the silica electrode, a large number of catalysts with large particles makes the growth of silicon nanofibers difficult to control, and it is difficult to obtain high-purity silicon nanofibers

Method used

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  • A system for in-situ electrocatalytic molten salt electrolysis synthesis of silicon nanofibers by diaphragm method
  • A system for in-situ electrocatalytic molten salt electrolysis synthesis of silicon nanofibers by diaphragm method
  • A system for in-situ electrocatalytic molten salt electrolysis synthesis of silicon nanofibers by diaphragm method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] refer to figure 1 ,Such as figure 1 It is a system in which molybdenum in situ catalyzes and electrochemically generates controllable silicon nanofibers. The anode is a spiral molybdenum electrode 7, the cathode is a graphite electrode 6, and the composition of the diaphragm 8 is 0.94Al 2 o 3 0.02CaO 0.03SiO 2 0.01MgO, the pore size is 0.8-1.0μm, the porosity is 38%, the molten salt electrolyte is CaCl 2 , the precursor silicon source is 2.0wt% CaSiO 3 , the electrolysis temperature is 900°C, and the electrode distance is 2cm. The electrolyte CaCl 2 and precursor CaSiO 3 Under the protective atmosphere of fluid argon, heat up to 900°C at 5°C / min and hold for 1h, the initial voltage U 1 = Pre-electrolysis t at 2V 1 = 10 min. U is then applied between the cathode and anode 2 = 2.2V constant voltage electrolysis, electrolysis time t 2 = 4h. After the electrolysis, the product obtained at the cathode is washed and dried with dilute hydrochloric acid and deionize...

Embodiment 2-8

[0027] According to the method of embodiment 1, the molten salt electrolyte CaCl in 1 in the embodiment 2 Adjust the composition and replace it with NaCl+CaCl 2 (molar ratio 1:1), the melting point of the molten salt is reduced, and the electrolysis temperature is reduced to 800°C, and all the other parameters are consistent with Example 1. After the electrolysis, the obtained product was washed and dried. The electrolysis product obtained at the cathode undergoes such as Figure 4 According to SEM characterization, the obtained product is a silicon nanofiber with a diameter of about 15 nm.

[0028] After the molten salt composition of the electrolyte in Example 1 was adjusted, the electrolysis temperature changed accordingly. Other process parameters are the same as in Example 1, and the results are as shown in Table 1.

[0029]Table 1 Effect of molten salt composition on the synthesis of silicon nanofibers

[0030]

[0031]

[0032] Adjusting the composition of th...

Embodiment 9-14

[0034] According to the method for embodiment 1, change the electrolysis time t in 1 in the embodiment 1 and t 2 , voltage U 1 and U 2 After the electrolysis, the obtained product was washed and dried, and the morphology of the product was characterized by SEM, and the current efficiency and the proportion of silicon nanofibers were calculated. The results are shown in Table 2.

[0035] Table 2 Effect of electrolysis time and electrolysis voltage on Heheng silicon nanofibers

[0036] Example t 1 / min

[0037] The results in Table 2 represent the electrolysis time t 2 The longer the silicon nanofiber, the coarser the size of the nanofiber, the lower the purity of the nanofiber, and the lower the current efficiency; when it is lower than the minimum decomposition voltage of the molten salt component, the electrolysis voltage U 2 The larger the Si nanofibers obtained, the thicker the t 2 and U 2 is the main factor to regulate the size and length of silicon nan...

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Abstract

The invention relates to the field of electrochemically synthesized silicon nanofiber materials, in particular to a system for silicon nanofibers synthesized electrochemically and controllably by diaphragm method molybdenum in situ catalysis. The electrochemical reduction method synthesizes silicon nanofibers from silicon dioxide or silicate. A ceramic diaphragm electrolytic cell is used, the metal electrode molybdenum is used as the anode, and the graphite electrode is used as the cathode; MCl is used x (M=Li, Na, K, Mg, Ca) is a molten salt electrolyte, and silicate or silicon dioxide is used as a precursor; a small amount of molybdenum ions electrochemically dissolved at the anode is deposited as molybdenum nanoparticles at the cathode as a catalyst. The voltage, temperature and time of electrolysis can controlly synthesize silicon nanofibers, and the prepared silicon nanofibers have a diameter of 10-50nm, a length of more than 500nm, and a purity of more than 85%. The silicon nanofiber preparation system of the invention has the characteristics of simple process, high yield, high product purity, low production cost and easy industrial production.

Description

technical field [0001] The invention relates to the field of electrochemically synthesized silicon nanofiber materials, in particular to an electrocatalytic and controllable synthesis technology of silicon nanofibers. Background technique [0002] Silicon nanofibers (SiNWs), a typical one-dimensional semiconductor nanomaterial, play an important role in nanoelectronic devices, biochemical sensors, and lithium-ion batteries. In particular, silicon materials are expected to replace graphite anodes for lithium-ion batteries as the next-generation anode material due to their extremely high specific capacity; however, silicon has problems such as serious volume expansion and poor conductivity during charge and discharge. Nanosizing silicon materials is an effective way. Synthesizing silicon nanomaterials with different microstructures can effectively balance the volume expansion stress during cycling, shorten the diffusion distance of lithium ions in active materials, and improve...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C25B1/33C25B9/19C25B13/02C25B13/07C25B11/02C25B11/042C25B15/02B82Y30/00B82Y40/00
CPCC25B15/02B82Y30/00B82Y40/00
Inventor 甘永平于哲黄辉张文魁梁初夏阳张俊贺馨平
Owner ZHEJIANG UNIV OF TECH
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