Nanoscale silicon material and preparation method thereof, negative electrode and lithium ion battery
A lithium-ion battery, silicon material technology, applied in nanotechnology, battery electrodes, secondary batteries, etc., can solve the problems of repeated growth of SEI film, large internal stress of volume change, and pulverization of silicon-based materials. Electrochemical performance and effect on cycling performance
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[0030] An embodiment of the present invention provides a method for preparing a nanoscale silicon material, comprising the following steps:
[0031] S1, providing sodium silicate solution and ammonium chloride solution, wherein the sodium silicate solution and the ammonium chloride solution are formed by dissolving sodium silicate and ammonium chloride in a mixed solvent of deionized water and ethanol respectively ;
[0032] S2, slowly titrating the sodium silicate solution and the ammonium chloride solution during high-speed stirring to obtain a white precipitate;
[0033] S3, separating the white precipitate after washing with ethanol;
[0034] S4, drying the separated white precipitate and reacting at a high temperature of 465-475°C to obtain SiO 2 ;
[0035] S5, the SiO 2 With Mg according to the molar ratio of 1:1.05~1.2, completely react at 640~660℃ under the protection of nitrogen;
[0036] S6, dissolving the reacted Mg and MgO, centrifuging, washing and drying to ...
Embodiment 1
[0057] 1. Weigh 5g of sodium silicate and dissolve it in 192ml of deionized water and absolute ethanol 1; 1 solution, and dissolve 1.4g of ammonium chloride in 192ml of deionized water and absolute ethanol 1:1 solution. 2.192ml of ammonium chloride solution was slowly titrated to the sodium silicate solution for 3h and 4h under high-speed stirring. A milky white substance was obtained. 3. Use ethanol for multiple high-speed centrifugation washes. A white precipitate was obtained. 4. Obtain the white substance and dry it at 80°C, and react at a high temperature of 470°C to obtain SiO 2 . 5. SiO 2 React with Mg at a stoichiometric ratio of 1:1.1 at 650°C (heating rate of 5°C / min) under argon protection for three hours. 6. Dissolve unreacted Mg and MgO with 10% hydrochloric acid, and perform centrifugal washing. 7. The obtained yellow-brown substance was dried in a drying oven at 80°C. Finally got Si. The prepared samples were divided into 3h-Si and 4h-Si according to the...
Embodiment test example 1
[0059] 2.1 X-ray diffraction analysis (XDR)
[0060] The X-ray diffraction figure of embodiment sample is as Figure 7 , the crystalline nature of silicon can be seen from the figure. And in the intensity diagram of the diffraction pattern of 4h-Si, it can be seen that there is also a small SiO 2 peak, which shows that the crystal grains of 4h-Si are smaller than those of 3h-Si, making the SiO 2 The mass ratio of SiO to Mg is 1:1.1, which is not enough to completely combine SiO 2 Reduced to Si. Therefore, for SiO with smaller particles 2 It should be appropriate to increase a certain proportion that is to increase the quality of Mg, so that SiO 2 Can be completely reduced to Si.
[0061] 2.2 Scanning electron microscope analysis (SEM)
[0062] The microscopic morphology characterization of embodiment sample is as Figure 8 , it can be clearly seen from the figure that as the addition rate of absolute ethanol slows down, the morphology of the formed silicon sample chang...
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