Debye Temperature Evaluation for Secondary Battery Cathode of α-Sn<i><sub>x</sub></i>Fe<sub>1−<i>x</i></sub>OOH Nanoparticles Derived from the <sup>57</sup>Fe- and <sup>119</sup>Sn-Mössbauer Spectra
Debye temperatures of <i>α</i>-Sn<i><sub>x</sub></i>Fe<sub>1−<i>x</i></sub>OOH nanoparticles (<i>x</i> = 0, 0.05, 0.10, 0.15 and 0.20, abbreviated as Sn100<i>x</i> NPs) prepared by hydrothermal reaction were estimate...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-02-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/25/5/2488 |
| Summary: | Debye temperatures of <i>α</i>-Sn<i><sub>x</sub></i>Fe<sub>1−<i>x</i></sub>OOH nanoparticles (<i>x</i> = 0, 0.05, 0.10, 0.15 and 0.20, abbreviated as Sn100<i>x</i> NPs) prepared by hydrothermal reaction were estimated with <sup>57</sup>Fe- and <sup>119</sup>Sn-Mössbauer spectra measured by varying the temperature from 20 to 300 K. Electrical properties were studied by solid-state impedance spectroscopy (SS-IS). Together, the charge–discharge capacity of Li- and Na-ion batteries containing Sn100<i>x</i> NPs as a cathode were evaluated. <sup>57</sup>Fe-Mössbauer spectra of Sn10, Sn15, and Sn20 measured at 300 K showed only one doublet due to the superparamagnetic doublet, while the doublet decomposed into a sextet due to goethite at the temperature below 50 K for Sn 10, 200 K for Sn15, and 100 K for Sn20. These results suggest that Sn10, Sn15 and Sn20 had smaller particles than Sn0. On the other hand, 20 K <sup>119</sup>Sn-Mössbauer spectra of Sn15 were composed of a paramagnetic doublet with an isomer shift (<i>δ</i>) of 0.24 mm s<sup>−1</sup> and quadrupole splitting (∆) of 3.52 mm s<sup>−1</sup>. These values were larger than those of Sn10 (<i>δ</i>: 0.08 mm s<sup>−1</sup>, ∆: 0.00 mm s<sup>−1</sup>) and Sn20 (<i>δ</i>: 0.10 mm s<sup>−1</sup>, ∆: 0.00 mm s<sup>−1</sup>), suggesting that the Sn<sup>IV</sup>-O chemical bond is shorter and the distortion of octahedral SnO<sub>6</sub> is larger in Sn15 than in Sn10 and Sn20 due to the increase in the covalency and polarization of the Sn<sup>IV</sup>-O chemical bond. Debye temperatures determined from <sup>57</sup>Fe-Mössbauer spectra measured at the low temperature were 210 K, 228 K, and 250 K for Sn10, Sn15, and Sn20, while that of <i>α</i>-Fe<sub>2</sub>O<sub>3</sub> was 324 K. Similarly, the Debye temperature of 199, 251, and 269 K for Sn10, Sn15, and Sn20 were estimated from the temperature-dependent <sup>119</sup>Sn-Mössbauer spectra, which were significantly smaller than that of BaSnO<sub>3</sub> (=658 K) and SnO<sub>2</sub> (=382 K). These results suggest that Fe and Sn are a weakly bound lattice in goethite NPs with low crystallinity. Modification of NPs and addition of Sn has a positive effect, resulting in an increase in DC conductivity of almost 5 orders of magnitude, from a <i>σ</i><sub>DC</sub> value of 9.37 × 10<sup>−7</sup> (Ω cm)<sup>−1</sup> for pure goethite Sn (Sn0) up to DC plateau for samples containing 0.15 and 0.20 Sn (Sn15 and Sn20) with a DC value of ~4 × 10<sup>−7</sup> (Ω cm)<sup>−1</sup> @423 K. This non-linear conductivity pattern and levelling at a higher Sn content suggests that structural modifications have a notable impact on electron transport, which is primarily governed by the thermally activated via three-dimensional hopping of small polarons (SPH). Measurements of SIB performance, including the Sn100<i>x</i> cathode under a current density of 50 mA g<sup>−1</sup>, showed initial capacities of 81 and 85 mAh g<sup>−1</sup> for Sn0 and Sn15, which were larger than the others. The large initial capacities were measured at a current density of 5 mA g<sup>−1</sup> found at 170 and 182 mAh g<sup>−1</sup> for Sn15 and Sn20, respectively. It is concluded that tin-goethite NPs are an excellent material for a secondary battery cathode and that Sn15 is the best cathode among the studied Sn100<i>x</i> NPs. |
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| ISSN: | 1661-6596 1422-0067 |