Synergistic anode materials based on crystalline Fe3O4 nanoparticles supported over different carbon matrix

GUILLERMINA LUQUE; DANIEL C. BARRACO; M. VICTORIA BRACAMONTE; EMILIANO PRIMO; PAULA BERCOFF; LISANDRO VENOSTA

San Salvador de Jujuy

Congreso; 3rd International Workshop on Lithium, Industrial Minerals and Energy; 2016

To fulfil the rapidly growing demand for lithium-ion batteries (LIB) with higher energy density and long cycle life, transition-metal oxides have been investigated as promising high-capacity anodes [1]. Among them, magnetite (Fe3O4) is a natural occurring mineral found in the earth?s crust and is also easy to synthesize through simple and non-hazardous techniques. Complete reduction of Fe3O4 involves the transfer of 8 electrons, providing a theoretical capacity of 925 mAhg-1 [2]. As the complete utilization of the electroactive metal centers can be challenging for a densely structured material as Fe3O4, which doesn?t have well defined layers or tunnel for facile Li+ insertion, the utilization of nano-sized Fe3O4 hybrid structures is almost mandatory.In this work, we report a study of cabon materials (C), with different particle sizes, used as support for magnetite nanoparticles (NPs) to obtain Fe3O4-C hybrids. The obtained hybrids were characterized as a function of the carbon support and were used for the development of anodes for LIBs. The cyclability and charge-discharge profiles were compared taking into advantage the capacity of lithiation of both Fe3O4 NPs and carbon. The carbon samples used (C1 and C2) were of different sizes; and Fe3O4 NPs (12 nm) are mainly located at the edges of the structures; as determined by SEM micrographs and Raman analysis. Hysteresis loops obtained through magnetometric measurements showed that the Fe3O4 wt% of e3O4-C1 hybrid was 16% while of Fe3O4-C2 was 9%.When used as anode materials, Fe3O4-C1 and Fe3O4-C2 samples exhibit 2 different regions when cycling them between 3.000 and 0.010 V. The first one (around 0.700 V) corresponds to the lithiation of Fe3O4 NPs and the formation of Li2O and metallic Fe. The second one (around 0.100 V) arises from the intercalation of Li ions in the graphitic planes. As a consequence, both constituents play a synergistic role in the lithium uptake and observed capacity profile.Fe3O4-C1 anode retains its specific capacity after cycling the battery several times while Fe3O4-C2 loses its capacity up to half of the initial one in the first cycles. This suggests that the differences in Fe3O4 content and carbon material size play a major role in the performance of the LIB.In conclusion, Fe3O4-C hybrid materials were synthesized, producing Fe3O4 NPs which are uniformly dispersed over the carbon surfaces. The Fe3O4-C hybrids with different sizes were employed for the development of anodes for LIB. A synergistic effect between the magnetite lithiation conversion reaction and the graphite lithium intercalation was observed. We also concluded that Fe3O4 loading and carbon material size determines the LIB cyclability.