Method for preparing porous silicon carbon nanotube composite negative electrode material of lithium ion battery by diatomite

Abstract

The invention relates to a method for preparing a porous silicon carbon nanotube composite negative electrode material of a lithium ion battery by diatomite. The method is characterized in that the diatomite is a silicon source, comprises the steps of preparing porous silicon, preparing a porous silicon matrix surface supported catalyst precursor and preparing a porous silicon carbon nanotube composite material, has the advantages of availability in raw material, low cost, clearness in morphology of the prepared porous silicon, high capacity of the silicon carbon composite material, cycle stability, high production efficiency, low cost and the like, and is suitable for industrial production. Under the test in which current density is 100mA / g, the initial reversible specific capacity of a negative electrode, prepared from the material, of the lithium ion battery reaches 1,529.1mAh / g, the reversible specific capacity reaches 885.4mAh / g after circulation of 40 times, and the subsequent cycle capacity is almost unchanged; and through the rate performance test, the reversible specific capacity is restored to about 800mAh / g when the current density is restored to 100mA / g, and the test shows that the material is high in connection tightness performance.

Description

technical field [0001] The invention belongs to the field of negative electrode materials for lithium ion batteries, in particular to a method for preparing porous silicon carbon nanotube composite negative electrode materials for lithium ion batteries from diatomite. Background technique [0002] The lithium storage capacity of negative electrode materials is a key factor restricting the application range of lithium-ion batteries. The theoretical specific capacity of current commercialized graphite-based carbon negative electrode materials is only about 372mAh / g, and the theoretical lithium storage capacity of silicon is as high as 4200mAh / g. The lithium intercalation platform is slightly higher than that of graphite, and the safety hazard is small. It shows a volume change of up to 300%, which leads to the pulverization of material particles, the destruction of the conductive network inside the electrode, and the poor conductivity. Therefore, the above-mentioned shortcomin...

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Problems solved by technology

[0003] Chinese Invention Patent Publication (Announcement) No. CN102208636A discloses a porous silicon-carbon composite material prepared from diatomite and its application. The preparation method is to reduce diatomite to obtain silicon with a porous structure by using a metal thermal reduction method. The precursors of porous silicon and carbon are dissolved in the corresponding solvents, and the dispersed mixed solution is carbonized under a protective atmosphere to prepare coated porous silicon / carbon composites, but this type of coated silicon-carbon composites are used with lithium ions During the preparation of the negative electrode of the battery, the carbon layer is easily broken during the cycle, resulting in poor cycle stability of the composite material. The first cycle can only reach 1500mAh / g, and no more cycles

[0004] China Invention Patent Publication (Notice) No. CN102185128A discloses a silicon-carbon composite material, which uses porous silicon as a substrate to directly grow one-dimensional carbon nanomaterials on its surface, and wraps the one-dimensional carbon nanomaterials and porous silicon substrates. Covered with amorphous carbon, the composite material is applied to the preparation of lithium-ion battery anode materials, and has stable cycle performance. The constant current charge and discharge test is carried out at a current density of 300mA / g, and the composite material shows the first time of 1149mAh / g. Reversible capacity, after 100 cycles, the reversible capacity is 10871149mAh / g, and the capacity retention rate is as high as 95%. However, there are disadvantages such as high price of porous silicon materials used as raw materials, complicated preparation process, and low production efficiency.

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