Development of new iron fluoride materials and their application as positive electrode materials in secondary batteries

锂二次电池被广泛用作能量存储装置。尽管氟化铁（III）被认为是一种有趣的高容量正极材料，但其在使用三电子反应的循环过程中的性能需要改进。采用氟解法合成了具有高比表面积的氟化铁（III），并对其电化学行为进行了研究。它们是无定形的并且具有高BET表面积（最高值为140 m2 g-1）。充放电测试表明，FeF 3产物在从Fe（III）Fe（II）还原的电压区域中显示出小容量，但在从Fe（II）还原到Fe（0）的电压区域中显示出高容量，导致总容量接近FeF 3的理论容量。

Lithium secondary batteries are widely used as energy storage devices. Although iron fluoride (III) is considered to be an interesting positive electrode material with high capacity, its performance during the cycling using the three-electron reaction requires improvement. In this study, iron fluoride (III) with high surface area has been synthesized by a fluorolysis method and itselectrochemical behavior was investigated.Properties of the FeF3 products depend on the Fe/HF ratio in preparation and fluorination temperature. They are amorphous and have high BET surface areas (the highest value of 140 m2 g-1). The charge-discharge tests demonstrated that the FeF3 products show a small capacity in the voltage region of the reduction from Fe(III) Fe (II) but a high capacity in the voltage region of the reduction from Fe(II) to Fe(0), resulting in a total capacity near the theoretical capacity for FeF3.