Xi'an Jiaotong University publishes major research results on silicon anodes for lithium-ion batteries

　　Recently, Professor Zheng Xiaoquan’s research group from the State Key Laboratory of Power Equipment and Electrical Insulation, School of Electrical Engineering, Xi’an Jiaotong University, and Professor Cui Yi from the School of Materials Science and Engineering of Stanford University and Professor Li Ju from the Department of Nuclear Engineering of the Massachusetts Institute of Technology worked together to produce a high-pressure solid density The Si@TiO2 structure silicon anode full battery has achieved two times the volume specific capacity (1100 mAh/cm3) and twice the mass specific capacity (762 mAh/g) of the traditional graphite anode.

　　Lithium-ion batteries have been widely used in portable electronic devices, electric vehicles and energy storage. However, due to the specific capacity of the positive and negative active materials, currently commercial lithium-ion batteries are only used for low-level power requirements. Silicon is expected to be the next-generation lithium-ion battery high-capacity anode material, with a theoretical specific capacity of 4200mAh/g, which is more than ten times that of traditional graphite anodes (340mAh/g). However, the volume of the silicon negative electrode changes more than 300% during the charging and discharging process, which causes the active material to separate from the current collector and lose its activity, as well as the generation of unstable solid electrolyte interface (Solidelectrolyte interface) SEI, which makes the coulombic efficiency of the silicon negative electrode low, which affects its use in the full battery. Use in. Nano-silicon anode has always been a research hotspot. By coating the nano-silicon anode with a layer of artificial SEI, the problems of silicon expansion and contraction and SEI stability can be effectively solved. However, the nano-structured silicon negative electrode also faces engineering problems such as low powder tap density, and the inability to roll compaction leads to low electrode compaction density. How to coat the nano-silicon negative electrode with a layer of artificial SEI that has high mechanical strength and can withstand the rolling pressure of the battery industry is an important direction to solve the commercialization of the nano-silicon negative electrode.

　　Recently, Professor Zheng Xiaoquan’s research group from the State Key Laboratory of Power Equipment and Electrical Insulation, School of Electrical Engineering, Xi’an Jiaotong University, and Professor Cui Yi from the School of Materials Science and Engineering of Stanford University and Professor Li Ju from the Department of Nuclear Engineering of the Massachusetts Institute of Technology worked together to produce a high-pressure solid density The Si@TiO2 structure silicon anode full battery has achieved two times the volume specific capacity (1100mAh/cm3) and twice the mass specific capacity (762mAh/g) of the traditional graphite anode. The doctoral student Jin Yang in the research group uses cheap glucose as raw material. First, a uniform carbon layer is coated on the surface of nano-silicon particles by the glucose hydrothermal method, and then a layer of titanium source is soaked and adsorbed in a titanium isopropoxide solution. After calcination in the air, the carbon layer is removed, and the outer surface of the nano-silicon anode is coated with an artificial titanium dioxide nano-layer to synthesize a high mechanical strength Si@TiO2yolk-shell structure anode. The in-situ TEM mechanical test shows that its titanium dioxide The mechanical strength of the shell is 5 times that of amorphous carbon. After experimental testing, the Si@TiO2 electrode sheet can withstand high-strength roller pressure to increase the compaction density of the electrode sheet, and through the self-repair of SEI, the outer surface of Si forms a dense artificial SEI + natural SEI, which can make it stable The coulombic efficiency of 99.9% is above 99.9%, which meets industrial application standards, and will effectively promote the commercial application of silicon-based anodes in the battery industry.