Silicon-carbon composite microsphere anode material and preparation method thereof

A technology of composite microspheres and silicon-carbon composites, applied in the direction of negative electrodes, battery electrodes, active material electrodes, etc., can solve the problems of unstable negative electrode material structure, insufficient isolation of electrolyte, unfavorable large-scale production, etc., and achieve low cost , easy to operate, reduce the effect of stress damage

Active Publication Date: 2015-02-18
SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the porous carbon matrix of the silicon-carbon composite material is an open structure, and the electrolyte can penetrate into the composite material through the pores, and the preparation cost is high, which is not conducive to large-scale production.
Li et al. (Journal of Power Sources 248 (2014) 721.) spray-dried the mixture of graphite, nano-silicon particles and citric acid to obtain graphite as the inner core and a composite of Si and porous carbon as the shell. Granular composite materials, when used as the negative electrode of lithium-ion batteries, exhibit goo

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  • Silicon-carbon composite microsphere anode material and preparation method thereof
  • Silicon-carbon composite microsphere anode material and preparation method thereof
  • Silicon-carbon composite microsphere anode material and preparation method thereof

Examples

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Example Embodiment

[0026] The embodiment of the present invention provides a method for preparing a silicon-carbon composite microsphere negative electrode material, which includes the following steps: firstly mixing nano-silicon particles and a first polymer solution, spray drying, and forming the first composite microsphere; A composite microsphere is mixed with a second polymer solution to coat the surface of the first composite microsphere. After the solvent is volatilized, a second composite microsphere with a core-shell structure is formed; and finally the second composite microsphere is The ball is oxidized and carbonized to form a silicon-carbon composite microsphere anode material.

[0027] In a preferred embodiment of the present invention, the first polymer solution includes a polyvinyl alcohol solution, and the second polymer solution includes a polyacrylonitrile solution.

[0028] In the following, a more specific example is used to illustrate the silicon-carbon composite microsphere ano...

Example Embodiment

[0029] Example 1:

[0030] The first step: solution preparation. This example uses polyvinyl alcohol (PVA) with a molecular weight of about 20000 g / mol, polyacrylonitrile (PAN) with a molecular weight of about 15000 g / mol, and nano silicon particles (Si) with a diameter of less than 100 nm. First, weigh a certain amount of PVA, add it to a certain amount of deionized water, stir for 2 hours at 90°C to dissolve, prepare a 1% mass fraction of PVA aqueous solution; weigh according to the mass ratio of nano-silicon particles to PVA of 1:10 A certain amount of nano silicon particles is added to the PVA aqueous solution, stirring is continued for 2 hours at 80° C., and ultrasonically dispersed for 2 hours to make the nano silicon particles uniformly dispersed in the PVA aqueous solution to obtain a PVA-Si dispersion mixture. Weigh a certain amount of PAN, add it to a certain amount of N,N-dimethylformamide (DMF), stir for 5 hours at 80°C to dissolve, and prepare a PAN / DMF solution wit...

Example Embodiment

[0043] Example 2:

[0044] The difference between this example and example 1 is that the mass fraction of the PVA aqueous solution prepared in this example is 3%. The electrochemical performance test of the silicon-carbon composite microsphere anode material prepared in this example is as in Example 1. The test result is: when the cycle performance test is performed at a current of 0.1A / g, the first reversible capacity is 939mAh / g, and the coulombic efficiency It is 62%, the reversible capacity after 100 cycles is 763mAh / g, and the capacity retention rate is 81%; in the rate performance test, the reversible capacity at 2.0A / g current is 537mAh / g.

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Abstract

The invention discloses a silicon-carbon composite microsphere anode material and its preparation method. the preparation method comprises the following steps: firstly, nano-silicon particles and a first macromolecular solution are mixed, and first composite microspheres are formed after spray drying; then, the first composite microspheres and a second macromolecular solution are mixed to carry out surface coating on the first composite microspheres, and second composite microspheres with a core-shell structure are formed after solvent evaporation; and finally, the second composite microspheres undergo oxidation and carbonization treatments to form the silicon-carbon composite microsphere anode material. By the preparation method which has a simple technology, is low-cost and is easy to operate, the silicon-carbon composite microsphere anode material is prepared. In addition, no etching operation for pore-forming is required by the preparation method. Raw materials used in the preparation method can be selected from a number of sources. According to the silicon-carbon composite microsphere anode material obtained, advantages of nano-silicon and a carbon substrate are combined effectively. Thus, electrochemical performance of the silicon-carbon composite microsphere anode material used as a negative electrode of a lithium ion battery is enhanced.

Description

technical field [0001] The invention relates to a silicon-carbon composite microsphere negative electrode material for a lithium ion battery and a preparation method thereof. Background technique [0002] The negative electrode material of lithium-ion batteries is generally carbon material. The theoretical lithium storage capacity of the existing widely used graphite negative electrode is 372mAh / g, which is difficult to meet the increasing requirements of high-capacity lithium-ion batteries for electrode materials. Therefore, research and The development of high-capacity anode materials has become a key factor in improving the performance of lithium-ion batteries. The theoretical lithium storage capacity of silicon material is 4200mAh / g, which is an ideal material to increase the capacity of the negative electrode. However, the structure of silicon materials is unstable, and the volume expansion can reach 400% during the lithium intercalation process, and the volume shrinks...

Claims

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Application Information

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IPC IPC(8): H01M4/36H01M10/0525
CPCH01M4/1393H01M4/1395H01M4/362H01M4/386H01M4/583H01M10/0525H01M2004/027Y02E60/10
Inventor 秦显营李硕李宝华贺艳兵杜鸿达康飞宇
Owner SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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