How to design the silicon-based anode material for lithium-ion batteries to meet the commercial requirement

Silicon-based anode materials are considered as one of the alternative products of commercial carbon anode materials. However, due to the large volume effect in the charge-discharge process, they can not be commercialized. Therefore, researchers have carried out a lot of modification research. Based on both theoretical and experimental studies, it is hoped that the study of new alloy anode materials will be promoted.

The structure design

To change the performance of silicon monomer to a certain extent, reduce the volume expansion coefficient of silicon, but due to the volume effect still exists, and the electrical conductivity of the silicon itself is insufficient to support the rapid transport of lithium ion, so before silicon-based anode materials for commercial, still need a large number of structural design, to meet the requirements of commercial application.

1, the core-shell structure

Core-shell structure lies in the purpose of through the basic characteristic of the shell for silicon or silicon alloy volume expansion with buffer layer, to control the volume effect of silicon or silicon alloy core-shell structure. The researchers conducted a large study of core-shell structure. Figure 4 for Si/NiSi2 / Ni/C core-shell structure the structure diagram and circular curve of the sample.

Deng and others with nanometer Si as the kernel, NiSi2 / shell coated nanometer Si Ni, cover carbon layer, and preparation of silicon-based anode materials with core-shell structures. Experimental samples has 1194 MAH/g of the reversible specific capacity, 105 weekly cycle capacity remain at a rate of 98%.The preparation method has the characteristics of simple process and low cost.

Wu and others by electrostatic spinning technology in the nano silicon particles into the hollow carbon fiber preparation of Si/C cathode materials with core-shell structures.0.2 A/g, under the current density of the sample of the reversible specific capacity is 903 MAH/g, 100 weekly cycle capacity retention rate of 89%;When the current density increased to 2 a/g, samples of the reversible specific capacity reached 743 MAH/g, has good performance ratio. Hollow carbon fiber not only inhibits the volume expansion of nano silica, and improve the conductivity of the material.

2, the sandwich structure

Sun and others in industrial silicon powder, graphite, and sucrose as raw material, adopts the mechanical method of high-energy ball mill will drop of the scale of the industrial silicon powder, and mix industrial silicon powder and graphite ball mill, the sandwich structure are formed by sucrose high temperature pyrolysis carbon coated @ MS - G C composite cathode materials. Samples in 0.5 C under the reversible specific capacity is 830 MAH/g, 100 weekly cycle capacity attenuation of only 0.02%, a week has good cycle stability. Advanced structure design provides high conductive network on one hand, on the other hand, hindered the Si in the process of charging and discharging pulverization effect.

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