金属硅的储锂性能

Lithium Storage Property of Metallic Silicon

金属硅是硅矿石经过还原反应后含有金属元素(铁、铝、钙等)的不纯的硅粉,金属硅粉中硅的含量为60%～99.9%,价格远远低于纯硅粉。用廉价的金属硅作为锂离子电池的负极材料,研究了其电化学储锂性能。结果表明:对于不同的导电剂添加量,金属硅首次放电和充电比容量均高于纯硅;金属硅首次不可逆容量占70%,纯硅为85%,其循环性能比纯硅提高一倍以上;充放电电流密度越小,金属硅的容量衰减越慢;随着循环次数的增多,不同充放电电流所对应的容量逐渐趋近相同;金属硅和纯硅的储锂机理相近,在充放电循环过程中金属硅不断形成不可逆的Li13Si4、Li12Si7,这些不可逆相的存在消耗了材料中的Si,从而导致容量衰减。随着充放电的进行,晶态Si逐渐非晶化。

Metallic silicon contains metal elements （iron, aluminum, calcium, etc.）. Compared to pure silicon, the content of silicon in low-cost metallic silicon is from 60% to 99.9%. Metallic silicon is used as an anode material of lithium ion batteries. The electrochemical lithium storages of metallic silicon and pure silicon were investigated. The results show that for different contents of electrical conductors, the first discharge and charge specific capacity of metallic silicon is greater than that of pure silicon. The irreversible specific capacity of metallic silicon is 70% while that of pure silicon is 85%, and the cycle property of metallic silicon is one time greater than that of pure silicon. Also, the experiments were performed at different charging and discharging currents for metallic silicon and pure silicon, respectively. The lithium storage property of metallic silicon is better at a lower charging and discharging current, and the discharge and charge specific capacity of metallic silicon is similar after several cycles, compared to pure silicon. The process of charging and discharging results show that the lithium storage character of metallic silicon is similar to that of pure silicon. The structural transformation after the silicon material alloying and de-alloying reaction with Li was also analyzed by X-ray diffraction. It was indicated that metal silicon formed the irreversible Li13Si4 and Li12Si7 phases in the recharge cycles process. These irreversible phases could consume Si in the material, leading to the capacity attenuation. During charging and discharging, the crystalline Si became amorphous gradually.