Fe2O3改性复合材料Si/SiO2的电化学性能

Electrochemical performance of Fe2O3-modified composite Si/SiO2

摘要:

硅材料由于比容量(4200 mA h/g)是商用石墨负极(372 mA h/g)10倍以上,因此成为最有前途的高能量密度负极材料。但硅负极材料在充放电过程中产生的巨大体积变化,导致不可逆容量损失和低的库仑效率,使得硅负极的实际应用受到限制。为了缓解体积变化效应,本研究将微米Si与纳米非晶型SiO₂(Nano-SiO₂)以无水乙醇为砂磨剂,通过砂磨机合成了微纳Si/SiO₂复合材料(SNSO),并通过机械球磨的方式引入纳米Fe₂O₃,制备了Fe₂O₃改性Si/SiO₂复合材料(SNSO@Fe₂O₃)。采用XRD、XPS、SEM、TEM对改性复合材料进行表征,测试其电化学性能。结果表明,SNSO与Fe₂O₃在高能球磨的作用下呈现规则的球形核壳结构,外壳为非晶层,经改性的样品展现出优异的循环性能,在110 mA/g的电流密度下,经100次循环后,可逆比容量仍稳定在986 mA h/g以上,较SNSO提升约43%。其稳定的循环性能归因于球磨过程中FeSi相的生成以及非晶SiO_x和Fe₂O₃原位反应在Si表面形成的非晶层外壳结构,有效的缓解了Si的体积膨胀。

Abstract:

Silicon material is the most promising high energy density anode material because its specific capacity (4200 mA h/g) is more than 10 times higher than that of commercial graphite anode (372 mA h/g). However, the huge volume change of silicon anode materials during charging and discharging, resulting in irreversible capacity loss and low initial coulombic efficiency, makes the practical application of silicon anode limited. In order to reduce the volume change effect, in this research, micron Si and nano-amorphous SiO₂ (Nano-SiO₂) were synthesised by sand milling with anhydrous ethanol as the abrasive agent to form micro-nano Si/SiO₂ composites (SNSO), and nano-Fe₂O₃ was introduced to prepare Fe₂O₃-modified Si/SiO₂ composites (SNSO@Fe₂O₃) by mechanical ball milling. XRD, XPS, SEM and TEM were used to characterise the modified composites and test their electrochemical properties. The results show that SNSO and Fe₂O₃ present a regular spherical core-shell structure with an amorphous layer in the outer shell under the action of high-energy ball milling, and the modified samples exhibit excellent cycling performance, with the reversible specific capacity remaining stable above 986 mA h/g after 100 cycles at a current density of 110 mA/g, which is an enhancement of about 43% compared with that of SNSO. Its stable cycling performance is attributed to the generation of FeSi phase during ball milling and the amorphous layer shell structure formed on the Si surface by the in-situ reaction of amorphous SiO_x and Fe₂O₃, which effectively mitigates the volume expansion of Si.