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A kind of porous silicon/silicon carbon composite material and its preparation method and application

A technology of silicon-carbon composite materials and porous silicon, applied in silicon compounds, chemical instruments and methods, nano-carbon, etc., can solve problems that affect product performance, poor performance, and failure to meet needs

Active Publication Date: 2021-03-16
XIAMEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Materials with high specific capacity will have mechanical problems locally due to volume expansion. A series of basic studies have proved that it will crack and cause serious shedding
The second problem is that the SEI film on the silicon surface is relatively thick and uneven, which is greatly affected by temperature and additives, which will affect the specific energy of the lithium-ion battery.
However, the above-mentioned preparation method still has sintering and agglomeration phenomena when preparing porous silicon, which cannot maintain the shape of the precursor well, which further affects the performance of the product. At the same time, the product performance of the existing porous silicon or silicon-carbon composite materials is poor. , cannot meet the demand

Method used

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  • A kind of porous silicon/silicon carbon composite material and its preparation method and application
  • A kind of porous silicon/silicon carbon composite material and its preparation method and application
  • A kind of porous silicon/silicon carbon composite material and its preparation method and application

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Example 1: Preparation of mesoporous silica spheres

[0034]Step 1: Dissolve 0.6g of cetyl ammonium bromide in a solution mixed with 100mL of absolute ethanol and 240mL of deionized water, and stir for 30min;

[0035] Step 2: Add 4 mL of tetraethyl orthosilicate dropwise to the mixed solution in Step 1, and stir for 2 hours;

[0036] Step 3: Centrifuge the sample in step 2 at 4000rpm, wash it with absolute ethanol three times, then disperse it in 640mL deionized water at 85°C and let it stand for 24h, then dry it at 25°C for 48h to get Mesoporous silica ball 1.0g;

Embodiment 2

[0037] Embodiment 2: prepare magnesium silicide

[0038] Mix 2.8g of 325-mesh commercial metal silicon powder with 5.04g of 325-mesh metal magnesium powder, put them in a 20mL stainless steel tank after mixing evenly, keep warm at 600°C for 6h under an argon atmosphere, take it out after cooling, and obtain magnesium silicide of about 7.6g.

Embodiment 3

[0039] Embodiment 3: Preparation of porous silicon

[0040] Step 1: Get the mesoporous silica ball 0.3g (precursor) obtained in Example 1 and the magnesium silicide 0.39g obtained in Example 2 and place them in the crucible of the reaction vessel at a distance of 1cm (such as figure 1 Shown), wherein the magnesium silicide is close to the gas inlet end of the inert gas of the reaction vessel, and the mesoporous silica ball is located at the opposite end;

[0041] Step 2: Fill the reaction vessel with inert gas argon, and at the same time, heat the reaction vessel to generate magnesia thermal reaction. The heating method is 1-10°C / min heating rate to 750-950°C, and the holding time is 1-6h. The reaction process is:

[0042] Mg 2 Si(s)=2Mg(g)+Si(s), 2Mg+SiO 2 =Si+2MgO

[0043] Porous silicon crude product after completion of the reaction;

[0044] Step 3: The porous silicon crude product obtained in step 2 was washed with 1 mol of hydrochloric acid to remove by-products, wa...

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Abstract

The invention discloses a preparation method of a porous silicon / silicon carbon composite material, which comprises the following steps of 1, placing magnesium silicide and a precursor in a reaction vessel at a certain distance, and arranging the magnesium silicide and the precursor along the inert gas inlet gas flow direction of the reaction vessel, 2, introducing inert gas into the reaction container, heating the reaction container to carry out a magnesiothermic reaction, and obtaining a porous silicon / silicon carbon composite material crude product after the reaction is completed, and 3, carrying out acid washing, water washing and drying on the porous silicon crude product obtained in the step 2 to obtain the porous silicon / silicon carbon composite material. The invention also comprises the porous silicon or silicon carbon composite material prepared by the preparation method and application of the porous silicon or silicon carbon composite material as a lithium ion negative electrode material. The porous silicon or silicon carbon composite material prepared by the invention shows excellent cycle performance and rate capability in the lithium ion battery, and also has the advantages of simple and feasible preparation method, facilitation of batch preparation and the like.

Description

technical field [0001] The invention relates to the field of porous silicon and its composite materials, in particular to a porous silicon / silicon-carbon composite material and its preparation method and application. Background technique [0002] Silicon is the anode material of lithium ion battery with the highest specific capacity (4200mAh / g) discovered so far by human beings, and it is the most potential anode material. However, the application of silicon as the negative electrode of lithium-ion batteries also encounters some bottlenecks. The first problem is the huge volume expansion of silicon during the reaction. Through theoretical calculations and experiments, it can be proved that lithium intercalation and delithiation will cause volume changes, and this volume change is 300%. Therefore, no matter what kind of material is made, microscopically, at the atomic scale or nanoscale of silicon, its expansion is the same. 300%. Large volume changes must be considered in ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/36H01M4/38H01M4/62H01M10/0525C01B33/023C01B32/184
CPCC01B33/023C01B32/184H01M4/366H01M4/386H01M4/625H01M4/628H01M10/0525H01M2004/021H01M2004/027Y02E60/10
Inventor 张桥保陈慧鑫项奔安威力
Owner XIAMEN UNIV