Reduced Graphene Oxide (rGO)‐Supported and Pyrolytic Carbon (PC)‐Coated γ‐Fe₂O₃/PC‐rGO Composite Anode Material with Enhanced Li Storage Performance

Abstract

As a high‐capacity anode material for lithium ion batteries, γ‐Fe2O3 is a promising alternative to conventional graphite among multifarious transition metal oxides owing to its high theoretical specific capacity (1007 mAh g−1), abundant reserves, good safety and low cost. However, improving the electrical conductivity and overcoming the morphological damage caused by the severe volume expansion during cycling are still the tricky problems to be solved. Herein, a three‐dimensional heterostructure composite (γ‐Fe2O3/PC‐rGO60) was prepared by a facile solvothermal reaction followed by heat treatment in inert atmosphere. This composite material exhibits a reversible charge specific capacity of 1035 mAh g−1 at the current density of 0.1 A g−1. After 100 cycles at 0.2 A g−1, the capacity is increased from 966.2 to 1091.1 mAh g−1. Even cycled for 200 cycles at 1 A g−1, the capacity is only decreased from 751.4 to 670.6 mAh g−1, giving capacity retention of 89.3%. The rGO network supported flexible composite architecture is beneficial for accommodating the volume expansion of the γ‐Fe2O3 active material during the lithiation/delithiation process. Besides, the conductive rGO network and the in‐situ formed pyrolytic carbon (PC) can provide a smooth electron transmission path and a favorable lithium ion transport channel.

In situencapsulation of iron oxide nanoparticles into nitrogen-doped carbon nanotubes as anodic electrode materials of lithium ion batteries

“…5b, the high frequency intercept, medium frequency semicircle and low frequency Warburg straight line in the curve represent the series resistance ( R s ), charge transfer resistance ( R ct ) and the Li + diffusion behavior, respectively. 36 The simulated R s value of the Fe 2 O 3 @NCNT electrode (2.8 Ω) is quite a lot smaller than the corresponding value of Fe 2 O 3 /CB (4.6 Ω), indicating that the metallic NCNT substrate significantly improved the electronic conductivity of Fe 2 O 3 . Importantly, Fe 2 O 3 @NCNTs show an R ct of 148.2 Ω while Fe 2 O 3 /CB exhibits a much larger R ct of 223.8 Ω, verifying the enhanced charge transfer and Li + diffusion processes in Fe 2 O 3 @NCNTs.…”

Cactus-like iron oxide/carbon porous microspheres lodged in nitrogen-doped carbon nanotubes as anodic electrode materials of lithium ion batteries

“…5b, the Nyquist plots of both samples exhibited a depressed semicircle in the high-frequency region and a sloping line in the low frequency region, corresponding to a charge transfer resistance in the SEI membrane and a Li + semi-infinite Warburg diffusion resistance in electrode material, respectively. 37 After the second cycle, it can be observed that the R ct for the Fe 2 O 3 /C@NCNT electrode (150 O) is significantly smaller than that of Fe 2 O 3 /CB (262 O), which illustrates the superior electrochemical activity of the Fe 2 O 3 /C@NCNT anode. The diameters of the Fe 2 O 3 /C@NCNT anode show no obvious changes after the 2nd and 30th cycles, indicating that the robust NCNT network wrapped cactus-like Fe 2 O 3 porous microspheres effectively alleviate the pulverization and suppress the formation of excessive SEI layers, which promote the charge transfer and Li + transmission in the SEI and increase the kinetic rate.…”