Preparation method of formicary-shaped porous silicon for lithium ion battery

Abstract

The invention discloses a preparation method of formicary-shaped porous silicon for a lithium ion battery. The preparation method comprises the following steps: (1) enabling a magnesium silicide raw material to react for 2 to 24h in an ammonia gas atmosphere at a temperature of 600 to 900 DEG C, and obtaining a crude product containing porous silicon (3Mg2Si+4NH3 to 3Si+2Mg3N2+6H2), wherein a particle size of the magnesium silicide raw material is 0.2 to 10 micrometers; and (2) acid pickling the crude product containing the porous silicon to obtain the formicary-shaped porous silicon for the lithium ion battery. By improving an overall process flow of the porous silicon key preparation method and parameters and conditions of various reaction steps, compared with the prior art, the preparation method has the advantage of simplicity and easiness, a great number of porous micrometer silicon can be obtained by directly heating the obtained magnesium silicide in ammonia gas (or mixed gas of the ammonia gas and inert gas), and the yield is high.

Description

technical field [0001] The invention belongs to the field of components related to lithium-ion batteries, and more specifically relates to a method for preparing ant-nest-shaped porous silicon for lithium-ion batteries. Background technique [0002] The theoretical lithium storage capacity of silicon (Si) is as high as 4200mA h / g, which is 11 times the theoretical capacity of commercial graphite anodes, and the voltage platform of Si is slightly higher than that of graphite, which is not easy to cause the phenomenon of lithium precipitation on the surface during charging, and has excellent safety performance Based on graphite-based C anode materials, silicon is expected to replace graphite as the anode material for next-generation high-energy lithium-ion batteries. Compared with bulk Si materials, due to the reduction of absolute expansion volume, nano-Si can reduce the damage to the material structure caused by the stress generated in the lithium-deintercalation process, an...

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Problems solved by technology

However, the current methods for preparing porous silicon materials not only have harsh conditions, high cost, and complicated steps, but also cause serious pollution, involve many toxic substances, and are very harmful to humans.

For example, in the patent "Nanoporous silicon-lithium battery negative electrode material and its preparation method and application" (CN104701491A), the silicon substrate material is ball-milled and put into a liquid containing hydrofluoric acid and nitric acid for chemical corrosion to form porous nano-silicon , the hydrofluoric acid used in this method is extremely corrosive, the operation difficulty coefficient is large, and the pore structure is difficult to effectively control

Another example is the patent "A Preparation Method for Nanoporous Silicon" (CN105399100A), which uses the method of physical dissolution or chemical corrosion to remove another component in the alloy to prepare porous silicon. In this patent, metal chloride molten salt is used For magnesium silicide dealloying, the porous silicon obtained by this method is piled up by silicon nanoparticles, and the overall structure is unstable. As the negative electrode material of lithium-ion batteries, the capacity will be rapidly attenuated due to volume expansion during repeated cycles, which limits the Its application, in addition, metal chloride molten salt is easy to absorb water at high temperature, has strong corrosiveness, and pollutes the atmosphere

In the literature, another method for preparing porous silicon by dealloying magnesium silicide is to dissolve the magnesium atoms in magnesium silicide at high temperature with a melt of noble metal bismuth, and then wash off the excess bismuth with nitric acid solution to obtain porous silicon, such as Document "BulkNanoporous Silicon Negative Electrode with Extremely High Cyclability for Lithium-Ion Batteries Prepared Using a Top-Down Process" (Nano Lett.2014, 14, 4505-4510), this method requires high reaction requirements to use expensive helium, bismuth melting The overall price is also very expensive, and the requirements for equipment are relatively high, so it cannot be widely used on a large scale

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