On the cause of conductivity degradation in sodium strontium silicate ionic conductor

Jee, Youngseok; Zhao, Xuan; Huang, Kevin

doi:10.1039/c5cc02638e

Cited by 25 publications

(27 citation statements)

References 9 publications

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“…After exposing to H 2 at 500°C for 100 h, the undoped sample (blue curve) begins to show very small crystalline peaks but still with a majority of amorphous composition similar to the as-prepared one. In contrast, the air-treated sample (red) shows a significant amount of crystalline phase, which is consistent with our early reports [14,15]. The comparison between samples annealed in H 2 and air suggests that reducing atmosphere can alleviate the crystallization process.…”

Section: Solid-state Nmr Characterizationsupporting

confidence: 91%

“…Recently, the amorphous Na 2 Si 2 O 5 exhibiting an ionic conductivity of 0.01 S/cm 2 at 500°C has also been identified as a Na + -conductor. [12,13] A further study of this material revealed that the amorphous Na 2 Si 2 O 5 phase was unstable at elevated temperatures, transforming into a poorly conducting crystalline phase of the same composition and leading to a fast degradation of conductivity [14,15]. How to retain the conducting amorphous phase and thus a high ionic conductivity becomes a key for this material to be practically meaningful.…”

Section: Introductionmentioning

confidence: 99%

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Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

et al. 2016

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The Na 2 Si 2 O 5 in the amorphous state exhibits a fast Na + -conduction at elevated temperatures.However, it is metastable, gradually transforming into the insulating Na 2 Si 2 O 5 in the crystalline state with temperatures. The present work shows that the presence of H 2 and Al-doping can suppress the harmful amorphous-to-crystalline transformation in Na 2 Si 2 O 5 . A systematic investigation was carried out to understand the fundamental aspects of the amorphous-to-crystalline transformation through a suite of advanced experimental techniques including X-ray diffraction (XRD), differential scanning calorimetry (DSC) analysis, electrochemical impedance spectroscopy (EIS), Raman spectroscopy and multi-nucleus nuclear magnetic resonance spectroscopy (NMR).

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Section: Solid-state Nmr Characterizationsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

et al. 2016

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“…30 Table 2 also compares the measured conductivity of amorphous Na 2 Si 2 O 5 with the simulated one at different temperatures. It is also noted that, while D Na increases in general with temperature, a peculiar sudden increase is observed at 773 K, implying that a possible phase transition occurred at this temperature.…”

Section: The Simulation Methodsmentioning

confidence: 99%

Amorphous Na₂Si₂O₅ as a fast Na⁺ conductor: an ab initio molecular dynamics simulation

2015

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The present work uses the ab initio molecular dynamics (AIMD) methodology to simulate ionic transport in amorphous and crystalline Na 2 Si 2 O 5 from 573 to 973 K. The results suggest that amorphous Na 2 Si 2 O 5 is primarily a Na + conductor with negligible O 2À and Si 4+ contributions to ionic conduction, whereas crystalline Na 2 Si 2 O 5 is virtually an electrical insulator. The favorable pathway for Na + transport in amorphous Na 2 Si 2 O is along the two-dimensional channels formed by the SiO 4 tetrahedral layers. The disrupted Na-O coulombic attraction by the long-range disorder in amorphous Na 2 Si 2 O 5 contributes to the enhanced Na + conduction.

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“…Recently, amorphous Na 2 Si 2 O 5 has been identified as a Na + conductor by both experimental observations and theoretical simulations. [19][20][21][22] With a similar crystal structure to Na 2 Si 2 O 5 , amorphous Li 2 Si 2 O 5 would also be expected to exhibit Li + mobility in a similar manner. However, no one has reported to the best of our knowledge the conductivity of amorphous Li 2 Si 2 O 5 ; early studies on Li 2 Si 2 O 5 have mainly focused on the synthesis, 23,24 crystal structure, [25][26][27][28][29][30] and mechanical and electronic properties of the crystalline phase.…”

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Fast Li-Ion Transport in Amorphous Li₂Si₂O₅: An Ab Initio Molecular Dynamics Simulation

Lei

Wang

Huang

2016

J. Electrochem. Soc.

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The present study reports an ab-initio molecular dynamics (AIMD) simulation of ionic diffusion in the amorphous Li 2 Si 2 O 5 in a temperature range of 573-823 K. The results show that the amorphous Li 2 Si 2 O 5 is primarily a Li + conductor with negligible O 2− and Si 4+ contributions. The obtained activation energy of 0.47 eV for Li + diffusion is higher than Na + in the analogue amorphous Na 2 Si 2 O 5 , but close to other types of Li + conductors. The predicted Li + conductivity is on the order of 10 −2 S·cm −1 at 623-823 K. Our simulations also reveal that Li + in the amorphous Li 2 Si 2 O 5 diffuses via a hopping mechanism between the nearest sites in the channels formed by two adjacent SiO 4 layers. © The Author Solid-state lithium-ion batteries (SSLIBs) are envisioned to be the next-generation high-power and high-capacity energy storage devices with far less safety and temperature stability issues experienced by the conventional liquid-based counterparts.1-18 As a key component of SSLIBs, the electrolyte should possess a high Li + conductivity (σ) at room temperature and low activation energy (E a ) for use over a broad range of operating temperatures. In the meanwhile, properties such as electrochemical stability over a wide working voltage window and chemical stability against electrodes (layered cathode and Li metal anode) should also be preferred. So far, a broad range of materials have been investigated as potential solid Li 6-8 and sulfide-based compounds with higher ionic conductivities such as the thio-LISICON group (Li 7 P 3 S 11 , σ = 3.2-17 × 10 −3 Scm −1 at 25 Therefore, the aim of the present study is to investigate the ionic transport property, in particularly Li + conductivity, in the amorphous Li 2 Si 2 O 5 that is a close analogue to the known Na + -conductoramorphous Na 2 Si 2 O 5 via a theoretical ab-initio molecular dynamics (AIMD) approach. We selected 573-823 K as the temperature range for the simulation because we have experimentally observed reasonably high conductivity from the amorphous Li 2 Si 2 O 5 in this temperature range. With the help of this AIMD simulation, we will be able to gain the insights into the nature of the observed conductivity. We believe that the outcome of this work is not only important to the understanding of ionic conduction mechanism in solid-state amorphous Li 2 Si 2 O 5 , but also to the identification of new solid-state electrolytes for future solid-state Li-ion batteries. 2 ) valence electrons with a plane wave cutoff energy of 500 eV. The atomic positions were optimized to the level of the maximum ionic force ≤0.02 eV Å −1 . A Verlet algorithm was integrated with Newton's equations of motion at a time step of 2 fs for a total simulation time of 50 ps, i.e., 25,000 steps performed on an NVT ensemble. The frequency of the temperature oscillations was controlled by the Nosé mass during the simulations. A supercell of 2 × 1 × 2 unit cell containing 144 atoms was chosen for a k-point sampling at the -point.Initial configurations.-The simulations started...

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On the cause of conductivity degradation in sodium strontium silicate ionic conductor

Abstract: Here we present strong experimental evidence that elucidates the fundamental cause for the conductivity degradation observed in Na-SrSiO3 ionic conductor.

Cited by 25 publications

References 9 publications

Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

Amorphous Na₂Si₂O₅ as a fast Na⁺ conductor: an ab initio molecular dynamics simulation

Fast Li-Ion Transport in Amorphous Li₂Si₂O₅: An Ab Initio Molecular Dynamics Simulation

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On the cause of conductivity degradation in sodium strontium silicate ionic conductor

Abstract: Here we present strong experimental evidence that elucidates the fundamental cause for the conductivity degradation observed in Na-SrSiO3 ionic conductor.

Cited by 25 publications

References 9 publications

Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

Amorphous Na2Si2O5 as a fast Na+ conductor: an ab initio molecular dynamics simulation

Fast Li-Ion Transport in Amorphous Li2Si2O5: An Ab Initio Molecular Dynamics Simulation

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Amorphous Na₂Si₂O₅ as a fast Na⁺ conductor: an ab initio molecular dynamics simulation

Fast Li-Ion Transport in Amorphous Li₂Si₂O₅: An Ab Initio Molecular Dynamics Simulation