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Your search keyword '"Ortiz, Gregorio F."' showing total 262 results
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262 results on '"Ortiz, Gregorio F."'

38. Engineering Na+-layer spacings to stabilize Mn-based layered cathodes for sodium-ion batteries.

Author

Zuo, Wenhua, Liu, Xiangsi, Qiu, Jimin, Zhang, Dexin, Xiao, Zhumei, Xie, Jisheng, Ren, Fucheng, Wang, Jinming, Li, Yixiao, Ortiz, Gregorio F., Wen, Wen, Wu, Shunqing, Wang, Ming-Sheng, Fu, Riqiang, and Yang, Yong

Subjects
TRANSITION metal oxides, CATHODES, PHASE transitions, ENGINEERING, STORAGE batteries
Abstract

Layered transition metal oxides are the most important cathode materials for Li/Na/K ion batteries. Suppressing undesirable phase transformations during charge-discharge processes is a critical and fundamental challenge towards the rational design of high-performance layered oxide cathodes. Here we report a shale-like NaxMnO2 (S-NMO) electrode that is derived from a simple but effective water-mediated strategy. This strategy expands the Na+ layer spacings of P2-type Na0.67MnO2 and transforms the particles into accordion-like morphology. Therefore, the S-NMO electrode exhibits improved Na+ mobility and near-zero-strain property during charge-discharge processes, which leads to outstanding rate capability (100 mAh g−1 at the operation time of 6 min) and cycling stability (>3000 cycles). In addition, the water-mediated strategy is feasible to other layered sodium oxides and the obtained S-NMO electrode has an excellent tolerance to humidity. This work demonstrates that engineering the spacings of alkali-metal layer is an effective strategy to stabilize the structure of layered transition metal oxides. Suppressing phase transitions is crucial for the layered lithium/sodium transition metal oxide cathodes in batteries. Here, the authors report a water-mediated strategy to mitigate the phase transitions and boost electrochemical performances of manganese-based layered cathodes for cost-effective Na-ion batteries. [ABSTRACT FROM AUTHOR]

Published
2021
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44. Insight into the Electrochemical Sodium Insertion of Vanadium Superstoichiometric NASICON Phosphate

Author

Aragón, María J., Lavela, Pedro, Ortiz, Gregorio F., Alcántara, Ricardo, and Tirado, José L.

Abstract

A slight deviation of the stoichiometry has been introduced in Na3–3xV2+x(PO4)3(0 ≤ x≤ 0.1) samples to determine the effect on the structural and electrochemical behavior as a positive electrode in sodium-ion batteries. X-ray diffraction and XPS results provide evidence for the flexibility of the NASICON framework to allow a limited vanadium superstoichiometry. In particular, the Na2.94V2.02(PO4)3formula reveals the best electrochemical performance at the highest rate (40C) and capacity retention upon long cycling. It is attributed to the excellent kinetic response and interphase chemical stability upon cycling. The electrochemical performance of this vanadium superstoichiometric sample in a full sodium-ion cell is also described.

Published
2024
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45. Exploring the high-voltage Mg2+/Na+ co-intercalation reaction of Na3VCr(PO4)3 in Mg-ion batteries.

Author

Rubio, Saál, Liu, Rui, Liu, Xiangsi, Lavela, Pedro, Tirado, José L., Li, Qi, Liang, Ziteng, Ortiz, Gregorio F., and Yang, Yong

Abstract

Na3VCr(PO4)3 has attracted great attention due to its high energy density and stable structure. The substitution of vanadium with chromium led to an increase in the redox potential from 3.4 to 4.2 V (vs. Na+/Na). In this work, the electrochemical performance of Na3VCr(PO4)3 (NVCP) in Mg cells is successfully investigated. Reversible multielectron Mg2+/Na+ extraction/insertion is observed. Upon charging, NVCP exhibits two plateaus at 1.75 V and 2.3 V vs. Mg2+/Mg0 achieving a maximum reversible capacity of 85 mA h g−1 (a 1.45 electron reaction) enabling oxidation to VV as determined by 51V NMR and XPS, and accompanied by extraction of sodium from Na2 sites according to 23Na NMR. During the subsequent cycles Mg2+/Na+ ions react at 2.3 and 1.7 V, and an additional peak of Mg2+ at 1.2 V is observed. Alternatively, electrochemical cells were also assembled with activated carbon in a 0.1 M Mg(TFSI)2 electrolyte, leading to similar profiles and capacity even at higher current density. Finally, the chemical desodiation of NVCP using I2, Cl2 and NO2BF4 is performed to avoid mobile sodium ions. XRD, XPS and 51V NMR confirmed the contraction of the cell and the oxidation to VIV and VV. Iodine was not capable of full sodium extraction. Despite this fact, the ability of this sample to retain 65 mA h g−1 during a few cycles evidences the reversibility of magnesium insertion. The use of stronger oxidants such as Cl2 or NO2BF4 allowed the increase of the initial OCV and resulted in a plateau at 4 V. The chemical desodiation was also accompanied by an enhanced capacity decrease which could be correlated with the structural degradation. [ABSTRACT FROM AUTHOR]

Published
2019
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