Hierarchical flower-like Fe2O3 mesoporous nanosheets with superior electrochemical lithium storage performance

Synthesis of Flower-Like Nb2Se9 as High-Performance Anode Materials for Lithium-Ion and Sodium-Ion Batteries

“…The three-dimensional (3D) micro–nano structure of F-Nb 2 Se 9 endows it with a shorter ion transport path than R-Nb 2 Se 9 . In addition, the staggered stacked structure can provide extra space to alleviate the volume changes during the repeated charge and discharge process, which is conducive to improving cycle stability . In addition, according to the HRTEM results of prepared F-Nb 2 Se 9 (Figure e), the lattice spacing of 0.277 nm corresponded to the (−213) plane of Nb 2 Se 9 (PDF card number 71-0607).…”

“…Notably, there was a significant capacity rising phenomenon, which is probably due to improved Li diffusion kinetics by the gradual activation process and the reversible formation of a gel-like polymeric layer through a “pseudo-capacitance-type behavior” during cycling, leading to more electrochemically active surfaces . The cycling capacity enhancement is common for various nanostructured metal oxide/chalcogenides. ,,, Meanwhile, the high reversible capacities of 681, 536, 501, 463, 425, 380, 318, and 285 mAh g –1 were achieved at 50, 100, 200, 500, 1000, 2000, 4000, and 5000 mA g –1 for F-Nb 2 Se 9 , respectively, demonstrating outstanding rate performance (Figure b). It can be seen that, even though a high current density of 5 A g –1 , the capacity of F-Nb 2 Se 9 could still reach up to 285 mAh g –1 .…”

“…Figure a shows the initial three CV curves of F-Nb 2 Se 9 at the scanning rate of 0.1 mV s –1 and voltage range of 0.01–3.0 V. The cathode peak (1.72 V) in the first discharge process may be due to the insertion of Li ions into Nb 2 Se 9 to form Li x Nb 2 Se 9 . , The next broad cathode peak at 0.53 V is attributed to the formation of Li 2 Se and metallic Nb through further conversion of Li x Nb 2 Se 9 accompanied by the solid electrolyte interphase (SEI) formation. , Another strong cathode peak at about 0.01 V corresponds to the storage of Li ions by the interface reaction . During the discharge process of the second and third cycles, the two main peaks move to 1.83 and 0.89 V, respectively, which is presumably attributed to the structural change and the activation of the F-Nb 2 Se 9 electrode material. , With regard to the anodic scan, the reversible anodic peaks appear at 1.83 and 2.20 V, and the peaks remain in the same position in the subsequent cycles, suggesting good electrochemical reaction reversibility. The peak at 1.83 V represents the conversion of Nb to Nb 4+ with the removal of lithium ions and Li 2 Se to Se during the delithiation process .…”

“…The Nyquist plots (panels e and f of Figure ) of the two samples (F-Nb 2 Se 9 and R-Nb 2 Se 9 ) were similar. Each curve consists of a semicircle in the high-frequency region and a slanted line in the low-frequency region, representing charge transfer resistance ( R ct ) and diffusive-related impedance, respectively . In addition, the corresponding equivalent circuit was also provided in Figure S2 of the Supporting Information.…”

Study of TiO2-Coated α-Fe2O3 Composites and the Oxygen-Defects Effect on the Application as the Anode Materials of High-Performance Li-Ion Batteries

“…In order to overcome these obstacles, many creative and effective strategies have been adopted to increase the cycling stability and rate performance, including various nanostructures and hybridization of two active materials in synergy . The strategies of various nanostructure designs, such as nanoparticles, , nanosheets, nanorods, hollow nanospheres, nanotubes, and so forth, are studied by many researchers. Pan et al synthesized submicron-sized α-Fe 2 O 3 by direct annealing method, and the capacity was 970 mA h·g –1 at 400 mA·g –1 after 300 cycles.…”