Engineering P2W18 and GO synergistically supported octahedral Fe2O3 anode for lithium-ion batteries

Abstract

By employing polyoxometalate (POMs) with high ion-conductivity and graphene oxide (GO) with high electron-conductivity, series of Fe2O3@P2W18-x@GO composites were successfully designed and fabricated to upgrade the performance of Fe2O3 anode for lithium-ion batteries (LIBs), where (NBu4)6[P2W18O62] (P2W18) clusters are uniformly confined in octahedral Fe2O3 framework. In the work, the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV) under different scan rates were employed to explore the lithium storage contribution of P2W18 and GO to Fe2O3. Compared with 734.5 mAh g−1 of octahedral Fe2O3 at 30 cycles, the capacity of Fe2O3@P2W18-x (x =1, 2, 3) decreases rapidly to 255.5 mAh g−1, indicating that P2W18 alone has a negative effect on the electrochemical performance of Fe2O3, maybe due to the intense Li+ conductivity of P2W18. After coating GO, the Fe2O3@P2W18–2@GO anode shows relatively stable electrochemical performance with specific capacity of 642.1 mAh g−1 after 400 cycles at 0.1 A g−1, and a very long lifetime of 1000 cycles with ca. 375.4 mAh g−1 at 1.0 A g−1. Numerous repeated/controlled experiments indicate that both P2W18 and GO are indispensable for ameliorating the electrochemical performances of Fe2O3.