The application of nano silicon powder on the anode material in lithium battery

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The function mechanism of nano silicon powder

As nano silicon has high absorptivity to lithium battery, it can greatly increase the capacity of lithium battery (it can reach 4000mA/h in theory). By replacing nano carbon powder with nano silicon powder and graphite and using them as the anode material of lithium battery, it can produce silicon/graphite compound with mechanical milling method. XRD, SEM, electrochemical testing and other methods can be used in the structural characterization and performance test of this is kind of compound. After ball milling of silicon and graphite under different mass ratios as well as after the charge-discharge test of the compounds, the optimal proportion between silicon and graphite can be obtained, which is 1:9. By composing silicon and graphite into Si-C composite, it can effectively reduce expansion when silicon is absorbing lithium ions as well as can increase the affinity between silicon and electrolyte, will be easy to disperse and can increase cycle performance. By using silicon nanowire that made by nano silicon powder in the anode material of rechargeable lithium battery or using nano silicon powder that coated by graphite, the capacitance and charge-discharge cycles of rechargeable lithium battery can be increased by 3 times. Experiment results show that silicon and graphite composite not only has higher cycle performance than nano silicon, but also has higher reversible capacity than graphite. Besides, it can greatly increase the capacity of lithium battery.

high purity silicon powderWhen the mass ratio between silicon and graphite has reached 4:6, the capacitance will reduce sharply. After 25 charge-discharge cycles, the capacitance will reduce to 200mA.h/g. Therefore, the silicon content should be controlled in a low level in the compound. If the silicon content is too high, silicon cannot be dispersed evenly by graphite, thus nano silicon will contact more with each other as well as will agglomerate, as a result, the coulombic efficiency and cyclicity will reduce accordingly. When the mass ratio between silicon and graphite has reached 3:7, although the reversible capacity will be larger than that of 4:6 after 25 charge-discharge cycles, the capacitance still reduces sharply according to the curve. It can be seen that when the mass ratio between silicon and graphite has respectively reached 1:9 and 2:8, it will have good cycle performance. Especially when the mass ratio has reached 1:9, it will have best cycle performance. Besides, as nano silicon is much more expensive than graphite, when the mass ratio has reached 1:9, it will save more production cost in the practical production. Compared with pure graphite, composite that has the mass ratio of 1:9 will have twice as much as reversible capacity in the first charge-discharge cycle. Meanwhile, it also will have good cycle performance as well as the capacitance can reach 310mA.h/g after 30 charge-discharge cycles.

Silicon and silicon containing material will have high specific capacity when they are used as anode material of lithium battery. The theoretical capacity of silicon can reach 4200mA.h/g. Besides, nano silicon/graphite composite that made by mechanical milling method can be used as anode material of lithium battery. This kind of composite will reflect high lithium storage performance of silicon as well as good cycle performance, low volume effect of graphite and other characteristics. The experiment results show that the best mass ratio between silicon and graphite will be 1:9. Electrochemical performance test shows that the cycle performance of composite will be improved a lot compared with pure silicon electrode as well as the reversible capacity will be higher than graphite. Therefore, it is expected to replace graphite and become the anode material of new generation lithium ion battery.

Brief introduction to nano silicon powder product

Nano silicon powders that provided by tttmetalpowder.com have following characteristics: high purity, good dispersing performance, small particle size, uniform particle size distribution, large specific area, high surface activity and low apparent density. Besides, this kind of product is also non-toxic, odourless as well as will have high activity. Nano silicon powder can be regarded as the new generation optoelectronic semiconductor material, which has very wide indirect gap semiconductor.

Main applications of nano silicon powder

a. Nano silicon powder can be made into silicon nanowire and used in the anode material of rechargeable lithium battery, or graphite can be coated on nano silicon powder surface before being used as the anode material, thus the capacitance and charge-discharge cycles of rechargeable lithium battery can be increased by more than 3 times.

b. Nano silicon powder can be used in high temperature coating and fireproofing material.

c. Nano silicon powder can be mixed with diamond under high temperature and can be made into silicon carbide/diamond composite. This kind of material can be used as cutting tool.