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

M. VICTORIA BRACAMONTE; PAULA BERCOFF; EMILIANO N. PRIMO; LISANDRO VENOSTA; GUILLERMINA L. LUQUE; DANIEL E. BARRACO

San Salvador de Jujuy

Workshop; II WLiME 2016: 3rd International Workshop on Lithium, Industrial Minerals and Energy; 2016

UNju

To fulfil the rapidly growing demand for lithium-ion batteries (LIB) with higher energy density andlong cycle life, transition-metal oxides have been investigated as promising high-capacity anodes[1]. Among them, magnetite (Fe 3 O 4 ) is a natural occurring mineral found in the earth?s crust and isalso easy to synthesize through simple and non-hazardous techniques. Complete reduction of Fe 3 O 4involves the transfer of 8 electrons, providing a theoretical capacity of 925 mAhg -1 [2]. As thecomplete utilization of the electroactive metal centers can be challenging for a densely structuredmaterial as Fe 3 O 4 , which doesn?t have well defined layers or tunnel for facile Li + insertion, theutilization of nano-sized Fe 3 O 4 hybrid structures is almost mandatory.In this work, we report a study of cabon materials (C), with different particle sizes, used as supportfor magnetite nanoparticles (NPs) to obtain Fe 3 O 4 -C hybrids. The obtained hybrids werecharacterized as a function of the carbon support and were used for the development of anodes forLIBs. The cyclability and charge-discharge profiles were compared taking into advantage thecapacity of lithiation of both Fe 3 O 4 NPs and carbon.The carbon samples used (C1 and C2) were of different sizes; and Fe 3 O 4 NPs (12 nm) are mainlylocated at the edges of the structures; as determined by SEM micrographs and Raman analysis.Hysteresis loops obtained through magnetometric measurements showed that the Fe 3 O 4 wt% ofe 3 O 4 -C1 hybrid was 16% while of Fe 3 O 4 -C2 was 9%.When used as anode materials, Fe 3 O 4 -C1 and Fe 3 O 4 -C2 samples exhibit 2 different regions whencycling them between 3.000 and 0.010 V. The first one (around 0.700 V) corresponds to thelithiation of Fe 3 O 4 NPs and the formation of Li 2 O 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 constituentsplay a synergistic role in the lithium uptake and observed capacity profile.Fe 3 O 4 -C1 anode retains its specific capacity after cycling the battery several times while Fe 3 O 4 -C2loses its capacity up to half of the initial one in the first cycles. This suggests that the differences inFe 3 O 4 content and carbon material size play a major role in the performance of the LIB.In conclusion, Fe 3 O 4 -C hybrid materials were synthesized, producing Fe 3 O 4 NPs which areuniformly dispersed over the carbon surfaces. The Fe 3 O 4 -C hybrids with different sizes wereemployed for the development of anodes for LIB. A synergistic effect between the magnetitelithiation conversion reaction and the graphite lithium intercalation was observed. We alsoconcluded that Fe 3 O 4 loading and carbon material size determines the LIB cyclability.