Hollow-wrapped structure helps silicon anode -Lithium - Ion Battery Equipment

Hollow-wrapped structure helps silicon anode material -Lithium - Ion Battery Equipment

In recent years, with the country's strong support for new energy vehicles, the sales of clean and non-polluting electric vehicles have achieved a blowout rise. However, the current commercial lithium battery anode material graphite can only reach a capacity of 300~340mAh/g in practical applications, and it is difficult to improve, which is far from meeting the urgent needs of new market users for high-performance lithium batteries.

Therefore, more and more people are devoted to developing battery materials with high energy density. Silicon anode material is favored by scientific researchers due to its high theoretical specific capacity (3752mAh/g), environmental friendliness and low cost, and is expected to become the main force of next-generation battery systems.

However, there are still many problems in the research and development of silicon anode materials. For example, the volume expansion effect of elemental silicon during the charging and discharging process is as high as 300%, which causes structural collapse and pulverization, which seriously restricts the development and application of silicon as a lithium battery anode material. . To solve the above problems, the key to research is to suppress the volume expansion effect in the electrode reaction and improve the poor conductivity of elemental silicon.(Lithium - Ion Battery Equipment)

In view of this, the research group of Professor Wang Xianyou of Xiangtan University successfully prepared a double-layered hollow spherical Si@TiO2@C anode material by a one-step method.

In this work, hollow Si spheres were prepared by a template-free method and magnesium thermal reduction method, and then the hollow spheres HN-Si were double-coated with butyl titanate and glucose to prepare Si@TiO2@@TiO2@ with abundant pore structure and high stability. C negative electrode material.

First, the Si nanospheres with hollow structure can self-regulate the huge volume expansion during the charge and discharge process; second, the TiO2 shell can improve the lithium ion transport rate (volume expansion rate is only 4%) due to its own structural advantages (volume expansion rate is only 4%), and The volume expansion of the bound Si active material is further transferred to the inner cavity instead of outward; finally, the outer C layer further improves the electrical conductivity and structural stability of the composite.

This result points out that the traditional single-layer coating strategy cannot meet the current requirements for the structural stability of electrode materials when facing the huge volume expansion effect of Si anode materials, while this new double-coated-hollow strategy It can effectively improve the volume expansion effect of silicon and improve its conductivity.

The results show that the hollow Si@TiO2@C nanospheres anode material with bilayer stability synthesized by magnesium thermal reduction method and sol-gel method, at a current density of 0.2A/g and an operating voltage of 0.01-2.5V, for the first time The discharge specific capacity is 2557.1mAh/g, and the coulombic efficiency is 86.06%. At a current density of 1 A/g, the reversible specific capacity of the Si@TiO2@C anode material is still 1270.3 mAh/g after 250 cycles. The first discharge specific capacity of the uncoated HN-Si anode material is 2264mAh/g, and the Coulomb efficiency is only 67.3%.

This double-layer clad-hollow structure design can shorten the transport paths of Li+ and electrons, and the abundant pore structure can also promote the full infiltration of the electrolyte and improve its rate performance, while the uniform TiO2 shell and C layer greatly improve Si Structural stability and electrical conductivity of @TiO2@C anode materials.

In conclusion, the bistable cavity structure design in this study can promote the further research and development of silicon-based anode materials, and also provides a reference for the study of anode materials with severe volume expansion and poor conductivity.





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