Abstract
New iron-oxide-based anodes are prepared by an environmentally-friendly and low-cost route. The analysis of the composition, structure, and microstructure of the samples reveals the presence of a major hematite phase, which is accompanied by a certain concentration of an oxyhydroxide phase, which can act as a “lithium-reservoir”. By using sodium alginate as a binder, the synthesized anodes display superior electrochemical response, i.e., high specific capacity values and high stability, not only versus Li but also versus a high voltage cathode in a full cell. From these bare materials, clay-supported anodes are further obtained using sepiolite and bentonite natural silicates. The electrochemical performance of such composites is improved, especially for the sepiolite-containing one treated at 400 °C. The thermal treatment at this temperature provides the optimal conditions for a synergic nano-architecture to develop between the clay and the hematite nanoparticles. High capacity values of ~2500 mA h g−1 after 30 cycles at 1 A g−1 and retentions close to 92% are obtained. Moreover, after 450 cycles at 2 A g−1 current rate, this composite electrode displays values as high as ~700 mA h g−1. These results are interpreted taking into account the interactions between the iron oxide nanoparticles and the sepiolite surface through hydrogen bonds. The electrochemical performance is not only dependent on the oxidation state and particle morphology, but the composition is revealed as a key feature.
Highlights
In recent years, the development of new oxide- and carbon-based active materials in the field of energy storage has attracted much attention, especially concerning their potential application in lithiumand sodium-based devices [1,2,3]
Having in mind the above considerations, we have focused our attention in obtaining new nano-architectured anodes through a sustainable process, which could significantly increase the electrochemical performance of these anodes based on bare iron oxides
The iron-oxide anodes contain an oxyhydroxide phase, which is revealed as a key component regarding the delivery of this excellent behavior, versus Li and versus a high voltage cathode in a full cell. This response is further optimized for the clay-supported composites, for sepiolite-containing electrodes
Summary
The development of new oxide- and carbon-based active materials in the field of energy storage has attracted much attention, especially concerning their potential application in lithiumand sodium-based devices [1,2,3]. Iron-based compounds (e.g., oxides, oxohydroxides) have concentrated the interest of many researchers in the field of lithium ion batteries (LIBs) for their use as anodes in these devices, since they display competitive capacity values [3,4,5] These materials are abundant in nature, practically innocuous, and low cost. In order to surpass these deficiencies, different strategies have been described in recent literature: to obtain nanomembranes [6], to modify the synthesis routes [3], to prepare composites with diverse carbon materials [7], and to optimize the materials response by nano-architecturing them with diverse clays as supports [8] It is worth mentioning several recent strategies implying the use of carbon fibers obtained from different precursors, leading to a significant improvement of conductivity and structural stability through the discharge-charge processes [9]
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