Ordered Mesoporous α‐Fe₂O₃ (Hematite) Thin‐Film Electrodes for Application in High Rate Rechargeable Lithium Batteries

Abstract

Herein is reported the synthesis of ordered mesoporous α-Fe(2)O(3) thin films produced through coassembly strategies using a poly(ethylene-co-butylene)-block-poly(ethylene oxide) diblock copolymer as the structure-directing agent and hydrated ferric nitrate as the molecular precursor. The sol-gel derived α-Fe(2)O(3) materials are highly crystalline after removal of the organic template and the nanoscale porosity can be retained up to annealing temperatures of 600 °C. While this paper focuses on the characterization of these materials using various state-of-the-art techniques, including grazing-incidence small-angle X-ray scattering, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and UV-vis and Raman spectroscopy, the electrochemical properties are also examined and it is demonstrated that mesoporous α-Fe(2)O(3) thin-film electrodes not only exhibit enhanced lithium-ion storage capabilities compared to bulk materials but also show excellent cycling stabilities by suppressing the irreversible phase transformations that are observed in microcrystalline α-Fe(2)O(3).

Morphology, Microstructure, and Magnetic Properties of Ordered Large-Pore Mesoporous Cadmium Ferrite Thin Film Spin Glasses

“…[3,8,18] During this research, we found that the use of hydrated cadmium and ferric nitrate salts gives the best results in terms of pore structure and material homogeneity. Synthesis carried out using other precursor combinations such as chlorides and acetylacetonates failed or produced illdefined materials (not shown) likely due to both the different sol-gel behavior and interactions with the KLE diblock copolymer.…”

“…This result is in line with our previous work on α-Fe 2 O 3 . [3] Therein, we showed that high-quality mesoporous thin films can be synthesized through facile polymer templating of hydrated ferric nitrate.…”

“…We note that this type of polymer has been shown to produce materials with comparatively thick walls that typically allow for uniform nucleation and growth of the crystalline phase in such way that the pore-solid architecture is only affected to a limited extent. [3,8,18] Cadmium ferrite belongs to the spinel-type oxides with space group 3 ̅ ( magneto-optical devices and as semiconducting sensing material. [19][20][21] In general, spinel ferrites exhibit a variety of interesting electrical, optical, and magnetic properties which is why they are widely used in applications such as magnetic recording.…”

“…Furthermore, many such materials have been shown to be able to outperform their bulk counterparts which is particularly evident in the fields of electrochemical energy storage, catalysis, and information technology. [1][2][3][4][5] Advances in both polymer templating and processing of sol-gel derived coatings have enabled the preparation of a range of different metal oxides with ordered pore cavities ranging from a few nanometers to almost 40 nanometers in diameter. [5][6][7][8][9][10] Their formation relies on the coassembly of molecular precursors with an amphiphilic polymer using an evaporation-induced self-assembly (EISA)…”

High-power lithium ion microbatteries from interdigitated three-dimensional bicontinuous nanoporous electrodes

“…For conventional lithium ion batteries, typical volumetric energy and power densities are around 10-60 mW h cm À 2 mm À 1 and 1-100 mW cm À 2 mm À 1 . It is possible to achieve higher power density, up to 1,000 mW cm À 2 mm À 1 , by using porous battery electrodes that reduce ion diffusion through the active anode and cathode materials, as well as designs that reduce ion diffusion time in the electrolyte and decrease electrical resistance in the electrodes [5][6][7][8][9][10][11] . Most publications on high-power batteries focus on either anode or cathode half cells, and show improved power density at the expense of energy density.…”