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The use of silicon-based anode materials for lithium-ion batteries. Compared with the traditional graphite anode, silicon has a very high theoretical specific capacity (4200 mAh/g) and a lower desulfurization potential (<0.5 V), and the voltage platform of silicon is slightly higher than that of graphite, making it. It is difficult to create a surface during charging. Lithium analysis, better safety performance. Silicon has become one of the potential options for upgrading carbon-based lithium-ion battery anodes.
The use of silicon-based anode materials for lithium-ion batteries
The application of silicon-based materials in lithium-ion batteries mainly involves two aspects. The first is to add nano-silicon to the negative electrode material to form a negative silicon electrode, and the second is to add organic silicon compounds to the electrolyte to improve the performance of the electrolyte. Compared with traditional anode materials, silicon anode materials have higher energy density and lower electrochemical potential. The theoretical capacity of silicon anode material is 4200 mAh/g, which is 2 to 10 times that of graphite anode material and 4 to 20 times of spinel structure lithium titanate (Li4Ti5O12) material.
Nano-silicon is widely used in various fields.
Silicon-carbon composite material is formed by graphite material. It is used as the negative electrode material of lithium-ion battery and can significantly increase the capacity of lithium-ion battery.
Used to produce high-temperature coatings and refractory materials.
③It is mixed with diamond under high pressure to form a composite material of silicon carbide and diamond, which is used as a cutting tool.
It can react with organic matter and be used as a raw material for organosilicon polymer materials.
⑤ Polysilicon is obtained by purifying metal silicon.
⑥ Semiconductor microelectronic packaging materials.
The problem of EtK's metal surface has been solved.
Disadvantages of silicon anode materials for lithium-ion batteries
In the process of inserting and removing lithium-ion batteries, silicon will expand the volume of Si by 100% to 300%, which will cause a large internal stress in the material, which will damage the material structure. The electrode material will fall on the copper foil and silicon surface. The SEI film is continuously formed and broken, which together reduces the conductivity and cycle stability of the electrode.
Silicon is a kind of semiconductor, and its conductivity is much worse than that of graphite. This leads to a large degree of irreversibility in the deintercalation process of lithium ions, which further reduces its first coulomb. efficient. Therefore, it is necessary to solve the volume expansion of silicon during the charging and discharging process and the low efficiency of the first charging and discharging.
Silicon material selection and structure design
1. Amorphous silicon and silicon dioxide
(1) Amorphous silicon
Amorphous silicon has a higher capacity at low potential. As a negative electrode material for lithium-ion batteries, its safety performance is higher than that of graphite electrode materials. However, amorphous silicon materials can only alleviate particle cracking and pulverization within a limited range. Its cycle stability still cannot meet the requirements for anode materials for large-capacity batteries.
(2) White carbon black
As a negative electrode material for lithium-ion batteries, SiO has a high theoretical specific capacity (higher than 1200 mAh/g), good cycle performance and low lithium extraction potential. Therefore, it is also a potential high-capacity anode material for lithium-ion batteries. However, the difference in silica oxygen content also affects its stability and reversibility: as the silica oxygen content increases, the cycle performance increases, but the reversibility decreases.
Due to the limited energy storage capacity, lithium-ion batteries using traditional graphite anodes can no longer meet the needs of emerging markets. Due to its high theoretical relevance, silicon-based materials have become an ideal choice for the next generation of lithium-ion battery anode materials. Specific capacity. However, limited by the huge volume change and poor conductivity during lithium storage, the large-scale and commercialization of silicon-based anode materials is still full of challenges.