Size‐Controlled Hollow Spheres of C/α‐Fe₂O₃ Prepared through the Quasiemulsion‐Templated Method and Their Electrochemical Properties for Lithium‐Ion Storage

Abstract

In this paper, α‐Fe2O3 hollow spheres in different sizes were successfully synthesized through a glycerol emulsion template method for use as efficient electrode materials in lithium‐ion batteries. The sizes of α‐Fe2O3 hollow sphere could be easily controlled by adjusting the amount of glycerol over the Fe precursor during the hydrothermal synthesis process. A thin carbon layer was subsequently coated on the surface of α‐Fe2O3 hollow spheres through hydrothermal treatment with glucose for the carbonization process, in which the carbon phases could serve as a conductive layer for the efficient charge transfer, but also as a buffer layer for the accommodation of volume vibration of the electrode material during cycling. The carbon‐coated α‐Fe2O3 hollow sphere electrode showed a high discharge capacity of approximately 1452 mAh g−1 with a capacity increase of at least 32 % compared to that of α‐Fe2O3 hollow spheres without the carbon coating at the 50th cycle. The stability and cycling performance were also significantly improved by the presence of the carbon layer, indicating that the C/α‐Fe2O3 hollow sphere could be a promising metal‐oxide anode material for lithium‐ion batteries.

Facile Fabrication of Fe2O3 Nanoparticles Anchored on Carbon Nanotubes as High‐Performance Anode for Lithium‐Ion Batteries

“…Initial columbic efficiency is 66.8 %. The irreversible capacity is due to decomposition of electrolytes and consequent formation of solid electrolyte interface (SEI) layer . As shown in Figure S6, the GCD curves under different current densities keep a similar shape and delivered high capacity, suggesting the good rate performance of the Fe 2 O 3 ‐NPs@CNT composite.…”

“…reported an ultrahigh reversible capacity of 2071 mAh g −1 for the encapsulated Fe 2 O 3 nanoparticles in CNTs at 0.05 A g −1 . It should be mentioned that the reported 2545 mAh g −1 by this research occupies the highest lithium storage capacities reported for Fe 2 O 3 at present, which can be attributed to the above‐mentioned capacity enhancing mechanism ,,,…”

“…As shown by Figure , in the initial negative scan for the Fe 2 O 3 ‐NPs@CNT anode, there are two cathodic peaks at 1.3 and 0.75 V (vs. Li + /Li), corresponding to the electrochemical reactions of Equation (1) and (2), respectively. Unlike many of the previous reports,,,,, both the two cathodic peaks appear in the following negative scan and no irreversible cathodic peak can be found, indicating that Equation (1) and (2) maybe reversible for the Fe 2 O 3 ‐NPs anchored on CNTs. Thus, during the discharge/delithiation process, Fe 0 is expected to fully oxidise to Fe III , rather than to Fe II , leading to high theoretical lithium storage capacity of 1007 mAh g −1 .…”

“…However, specific capacity decreases from 569 to 532 mAh g −1 in the 2nd‐20th cycles and then showed a monotonic increase from 532 to 1231 mAh g −1 in the 20th–750th cycles. This capacity enhancement is not unusual and has been frequently observed for previously reported Fe 2 O 3 based anode ,,,,, Such phenomenon can be attributed to three possible mechanism: 1) the electrochemical milling effect due to repeated volume expansion during cycling, which could reduce size of electroactive materials and thus enlarge contact area between the active sites and electrolytes; 2) interfacial lithium storage at two‐phase boundary of metal/Li 2 O; or 3) extra lithium storage via reversible formation/dissolution of SEI layer ,…”

Flute‐like Fe2O3 Nanorods with Modulating Porosity for High Performance Anode Materials in Lithium Ion Batteries

“…To overcome the intrinsic disadvantages of Fe 2 O 3 , intensive efforts have been devoted to the fabrication of novel micro/nano‐structures and synthesis of various nanocomposites. In particular, the fabrication of porous structural electrodes has proven to be a suitable strategy for LIBs . Recently, many studies have reported the synthesis of Fe 2 O 3 with hierarchical porosity and unique microstructure, such as hollow spheres and cubes,, Fe 2 O 3 @N−C hollow nanoparticles, hollow nanobarrels α‐Fe 2 O 3 /rGO, 3DG/Fe 2 O 3 aerogel, 3D hierarchical porous α‐Fe 2 O 3 nanosheets, and porous Fe 2 O 3 @C rods .…”