Restoration of long range order of Na ions in NaxCoO2 at high temperatures by sodium site doping

Assadi, M. Hussein N.; Katayama‐Yoshida, Hiroshi

doi:10.1016/j.commatsci.2015.07.043

Cited by 11 publications

(11 citation statements)

References 34 publications

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“…these dopants reside in different lattice sites depending on the O partial pressure during the synthesis. The insight obtained here complements our previous work that demonstrated that the location of dopants such as Cu and Au also depends on the Na content of Na 1−x CoO 2 [34]. One of the main conclusions that we draw in this work is that the location of cationic dopants in Na 1−x CoO 2 needs to be investigated critically and the simplistic assumption based on matching ionic radii in determining dopant location can be misleading at times.…”

Section: Introductionsupporting

confidence: 78%

“…Furthermore, we can approximate the conductivity as a function of Co 4+ concentration by assuming that the carrier mobility remains 1.0 cm 2 V −1 s −1 for doped Na 1−x CoO 2 [52] for which full details are provided in table S4. This approximation is somehow conservative as dopants in Na layer are generally expected to improve carrier mobility slightly [34]. This approximation gives a conductivity value of 1.03 × 10 3 Ω −1 cm −1 for Na 0.75 CoO 2 and 2.06 × 10 3 Ω −1 cm −1 for Na 0.50 CoO 2 .…”

Section: Resultsmentioning

confidence: 99%

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Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants

Assadi

2019

J. Phys.: Condens. Matter

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Doping is considered to be the main method for improving the thermoelectric performance of layered sodium cobaltate (Na1−xCoO2). However, in the vast majority of past reports, the equilibrium location of the dopant in the Na1−xCoO2's complex layered lattice has not been confidently identified. Consequently, a universal strategy for choosing a suitable dopant for enhancing Na1−xCoO2's figure of merit is yet to be established. Here, by examining the formation energy of Gd and Yb dopants in Na0.75CoO2 and Na0.50CoO2, we demonstrate that in an oxygen poor environment, Gd and Yb dopants reside in the Na layer while in an oxygen rich environment these dopants replace a Co in CoO2 layer. When at Na layer, Gd and Yb dopants reduce the carrier concentration via electron-hole recombination, simultaneously increasing the Seebeck coefficient (S ) and reducing electric conductivity (σ). Na site doping, however, improves the thermoelectric power factor (PF) only in Na0.50CoO2. When replacing a Co, these dopants reduce S and PF. The results demonstrate how thermoelectric performance critically depends on the synthesis environment that must be fine-tuned for achieving any thermoelectric enhancement.

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Section: Introductionsupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants

Assadi

2019

J. Phys.: Condens. Matter

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“…尽管如此, 从另一方面看, 该限制也为提升正极材料性能提供了指导方向: 在充放电循环过程中增大 Na ＋的可逆利用对电池性能的改善将非常有利. 目前已有研究通过元素掺杂/取代的策略来提升 Na ＋的可逆利用率, 提高钠离子电池性能 [44][45][46][47] . 2018 年 Mun 等 [48] 设计了 P2-Na 0.67 Co 与锂离子电池中常见的层状 LiCoO 2 [49][50][51] 相比(如图 3b 所示), Na x CoO 2 在充放电曲线上表现出了多个电压平台, 表明随着 Na ＋的嵌入和脱出, Na x CoO 2 经历了非常复杂的相变过程 [52] , 可能是层内 Na ＋ /空位复杂的有序情况所导致的 [53] .…”

Section: 钴酸钠的电化学性能研究unclassified

Research Progresses of Sodium Cobalt Oxide as Cathode in Sodium Ion Batteries

Xie¹,

Xiao²,

Zuo³

et al. 2021

Acta Chimica Sinica

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Sodium ion batteries have regained widespread attention in the field of large-scale electrochemical energy storage by virtue of their widely distributed and low-cost sodium resources. Among many of the cathode materials (layered, tunnel-like, polyanionic type and Prussian-blue type, etc.), layered transition metal oxide materials have received extensive research attention due to the features of high specific capacity, relatively good electrochemical reversibility, and rich and adjustable chemical composition. Sodium cobalt oxide is one of the most typical layered transition metal oxides. A lot of research has been done about sodium cobalt oxide since the 1980s. Although compared with other energy storage systems (such as lithium cobalt oxide materials which has the similar composition), sodium cobalt oxide does not take more advantage in electrochemical performance (like rate performance, cycle performance, etc.), but it can be observed from the charge and discharge curve that sodium cobalt oxide has undergone complex electrochemical processes, which means that it has a bunch of information on the degradation mechanisms during the charge and discharge processes. The correlation studies of the failure mechanism during the charging and discharging processes of sodium cobalt oxide (including the structure changes and the charge compensation mechanisms) are of great significance for the deep understanding of the layered oxide systems in sodium ion batteries. Therefore, on the basis of introducing the common crystal structure types and the synthesis phase diagram of sodium cobalt oxides, this article focuses on reviewing the structure changes (including phase transition and Na ＋ / vacancy ordering) and charge compensation mechanisms of sodium cobalt oxides with different crystal structures during the charging and discharging. At the same time, the correlation between the mechanisms above and electrochemical performance is discussed. This review aims to provide support for the in-depth study and establishment of the structure-activity relationship in the electrochemical processes of layered transition metal oxide cathode materials.

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“…Computational screening has recently emerged as a novel tool in the discovery of brand-new thermoelectric materials. − Subsequently, through computational survey into uncharted materials’ territory, one may find a desirable oxide alternative to the common thermoelectric materials, at least for those applications where exposure to elements is inevitable. More specifically, our study was motivated by the recent prediction and observation of spinel oxides with high Seebeck coefficient and high-performance thermoelectric cubic oxides .…”

Section: Introductionmentioning

confidence: 99%

High-Performance Thermoelectric Oxides Based on Spinel Structure

Assadi

Moreno

Fronzi

2020

ACS Appl. Energy Mater.

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High-performance thermoelectric oxides could offer a great energy solution for integrated and embedded applications in sensing and electronics industries. Oxides, however, often suffer from low Seebeck coefficient when compared with other classes of thermoelectric materials. In search of highperformance thermoelectric oxides, we present a comprehensive density functional investigation, based on GGA+U formalism, surveying the 3d and 4d transition-metal-containing ferrites of the spinel structure. Consequently, we predict MnFe 2 O 4 and RhFe 2 O 4 have Seebeck coefficients of ∼ ±600 µV K −1 at near room temperature, achieved by light hole and electron doping. Furthermore, CrFe 2 O 4 and MoFe 2 O 4 have even higher ambient Seebeck coefficients at ∼ ±700 µV K −1 . In the latter compounds, the Seebeck coefficient is approximately a flat function of temperature up to ∼ 700 K, offering a tremendous operational convenience. Additionally, MoFe 2 O 4 doped with 10 19 holes /cm 3 has a calculated thermoelectric power factor of 689.81 µW K −2 m −1 at 300 K, and 455.67 µW K −2 m −1 at 600 K. The thermoelectric properties predicted here can bring these thermoelectric oxides to applications at lower temperatures traditionally fulfilled by more toxic and otherwise burdensome materials.

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Restoration of long range order of Na ions in NaxCoO2 at high temperatures by sodium site doping

Cited by 11 publications

References 34 publications

Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants

Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants

Research Progresses of Sodium Cobalt Oxide as Cathode in Sodium Ion Batteries

High-Performance Thermoelectric Oxides Based on Spinel Structure

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Restoration of long range order of Na ions in NaxCoO2 at high temperatures by sodium site doping

Cited by 11 publications

References 34 publications

Na site doping a pathway for enhanced thermoelectric performance in Na1−x CoO2; the case of Gd and Yb dopants

Na site doping a pathway for enhanced thermoelectric performance in Na1−x CoO2; the case of Gd and Yb dopants

Research Progresses of Sodium Cobalt Oxide as Cathode in Sodium Ion Batteries

High-Performance Thermoelectric Oxides Based on Spinel Structure

Contact Info

Product

Resources

About

Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants

Na site doping a pathway for enhanced thermoelectric performance in Na_1−xCoO₂; the case of Gd and Yb dopants