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Understanding Structure–Function Relationship in Hybrid Co3O4–Fe2O3/C Lithium-Ion Battery Electrodes

Sultana, Irin, Rahman, Md Mokhlesur, Ramireddy, Thrinathreddy, Sharma, Neeraj, Poddar, Debasis, Khalid, Abbas, Zhang, Hongzhou, Chen, Ying, Glushenkov, Alexey M.
ACS Applied Materials & Interfaces 2015 v.7 no.37 pp. 20736-20744
anodes, electrochemistry, graphene, lithium, lithium batteries, oxides, structure-activity relationships
A range of high-capacity Li-ion anode materials (conversion reactions with lithium) suffer from poor cycling stability and limited high-rate performance. These issues can be addressed through hybridization of multiple nanostructured components in an electrode. Using a Co₃O₄–Fe₂O₃/C system as an example, we demonstrate that the cycling stability and rate performance are improved in a hybrid electrode. The hybrid Co₃O₄–Fe₂O₃/C electrode exhibits long-term cycling stability (300 cycles) at a moderate current rate with a retained capacity of approximately 700 mAh g–¹. The reversible capacity of the Co₃O₄–Fe₂O₃/C electrode is still about 400 mAh g–¹ (above the theoretical capacity of graphite) at a high current rate of ca. 3 A g–¹, whereas Co₃O₄–Fe₂O₃, Fe₂O₃/C, and Co₃O₄/C electrodes (used as controls) are unable to operate as effectively under identical testing conditions. To understand the structure–function relationship in the hybrid electrode and the reasons for the enhanced cycling stability, we employed a combination of ex situ and in situ techniques. Our results indicate that the improvements in the hybrid electrode originate from the combination of sequential electrochemical activity of the transition metal oxides with an enhanced electronic conductivity provided by percolating carbon chains.