Novel synthesis of FeF3·0.33H2O@hollow acetylene black nanosphere and its long-life electrochemical properties as a cathode for lithium-ion batteries

Abstract

Iron (III) fluoride (FeF3), characterized by high voltage and high specific capacity and emerges as a promising candidate for the forthcoming generation of cathode materials in lithium-ion batteries. This study employs a novel methodology by introducing Fe3+ sources into hollow acetylene black particles through a vacuum impregnation method. This innovative approach results in the synthesis of a composite material comprising FeF3∙0.33H2O encapsulated within hollow acetylene black nanospheres, denoted as the FeF3∙0.33H2O @hollow acetylene black nanosphere composite material (FF@HCN). The composite exhibits a shell composed of highly graphitized carbon and a core containing FeF3∙0.33H2O particles in the range of 10–20 nm. The proportion of active materials is 75.56 %. The acetylene black has chain-like structure and high specific surface area, significantly enhances the material's conductivity, contributing 74.4 % to the pseudocapacitance at a scan rate of 1 mV s−1. The cavity graphite shell plays a crucial role in restricting the expansion and pulverization decay of FeF3∙0.33H2O nanoparticles, thereby markedly improving the cycle stability. The initial capacity of the FF@HCN composite is 224.4 mAh g−1, and after 1000 cycles at 0.1 C, it maintains a capacity of 162.3 mAh g−1, resulting in a capacity retention rate of 72.3 % and decay per cycle of 0.027 %.