196,149 research outputs found
Transport Properties and SEI Stability of Na2Ti3O7 electrodes for Na-Ion Batteries: An EIS Study
No full textNa2Ti3O7 is a promising negative electrode for Na-ion batteries (NIBs) with a very low insertion voltage (0.3 V vs. Na+/Na) and high specific capacity (178 mAh/g) [1, 2]. However, Na2Ti3O7 shows poor capacity retention when synthesized from Na2CO3 as sodium precursor, reaching only 50-70% of capacity retention after 10 cycles [3, 4, 5]. The capacity fading is correlated, among other factors, with the presence of Na2CO3 on the particles [3], which is originated by the interaction of Na2Ti3O7 particles with atmospheric H2O and CO2. Another important factor to take into account is the formation of a stable solid-electrolyte interphase (SEI) layer. In fact, the reversible Na+ insertion/extraction reaction occurs at low potential and, therefore, electrolyte reduction occurs. The stability and composition of this SEI layer has been previously studied by X-ray photoelectron spectroscopy (XPS) [6], concluding that the SEI layer formed upon Na+insertion is partially dissolved during extraction.
In order to better understand the reasons behind the poor capacity retention, an electrochemical impedance spectroscopy (EIS) study was carried out to determine the electronic and ionic transport properties of Na2Ti3O7 electrodes. An interesting change of transport properties, and particularly of electron conductivity, during Na+ insertion/extraction process is revealed for Na2Ti3O7negative electrodes by EIS.
Na2Ti3O7 was synthesized via a ceramic route from precursors: TiO2 anatase and Na2CO3·H2O in excess. Three electrode Swagelok type cells were tested using metallic sodium disks as counter and reference electrodes; electrochemical measurements were performed at room temperature in the voltage window 0.05-1.6 V vs. Na+/Na. EIS measurements were performed by controlling the electrode potential through PITT (potentiostatic intermittent titration technique).
The EIS study here presented is the first experimental demonstration of a transition from electronic insulator to conductor in Na2Ti3O7 electrodes for NIBs [Fig. 1]. This reversible transition is originated by Na+ insertion/extraction and was recently predicted by DFT calculations. Moreover, the instability of the SEI layer has been also observed, in agreement with previous XPS studies, contributing to the capacity fading widely reported for this material. This confirms that prior to Na+ insertion the Na2Ti3O7 is an insulator and the ionic transport kinetics are limited by the electronic conductivity, but when the intercalated Na+ increases the Na2Ti3O7behaves as a metallic conductor and the kinetics are limited by the interfacial charge-transfer step.
Acknowledgments
M. Zarrabeitia thanks the Government of the Basque Country for funding through a PhD Fellowship. Financial support from the Basque Government (Etortek 10 CIC Energigune) and from the Ministerio de Economía y Competitividad of the Spanish Government (ENE2013-44330-R) is also acknowledged.
References
[1] P. Senguttuvan, G. Rousse, V. Seznec, J.M. Tarascon, M. R. Palacín. Chem. Mater. 23, 4109 (2011).
[2] G. Rousse, M.E. Arroyo y De Dompablo, P. Senguttuvan, A. Ponrouch, J.M. Tarascon, M.R. Palacín. Chem. Mater. 25, 4946 (2013).
[3] M. Zarrabeitia, E. Castillo-Martínez, J.M. López Del Amo, A. Eguía-Barrio, M.A. Muñoz-Márquez, T. Rojo, M. Casas-Cabanas. Acta Materialia, doi: 10.1016/j.actamat.2015.11.033.
[4] H. Pan, X. Lu, X. Yu, Y.S. Hu, H. Li, X.Q. Yang, L. Chen. Adv. Energy Mater. 3, 1186 (2013).
[5] J. Xu, C. Ma, M. Balasubramanian, Y.S. Meng. Chem. Comm. 50, 12564 (2014).
[6] M.A. Muñoz-Márquez, M. Zarrabeitia, E. Castillo-Martínez, A. Eguía-Barrio, T. Rojo, M. Casas-Cabanas. ACS Appl. Mater. Interfaces 7, 7801 (2015
Understanding the electrode – electrolyte interphase of high voltage positive electrode Na4Co3(PO4)2P2O7 for rechargeable sodium-ion batteries
No full textSodium-ion batteries (SIBs) have been postulated as a potential solution for large-scale stationary applications and light electromobility. Among positive electrode materials for SIBs, Na4Co3(PO4)2P2O7 attracted significant attention due to its high voltage and good specific capacity even at very high current densities. However, details of the formed electrode – electrolyte interphase (EEI) are still uncertain, being this of extreme importance considering that the high operating voltage of this electrode material is around the stability edge of most of the conventional electrolytes which, in some cases, already display side reactions above 3.0 V vs. Na/Na+. In this work, the EEI of Na4Co3(PO4)2P2O7 is analyzed in half-cell configuration using 1 M NaPF6 in EC:DEC as electrolyte. Conventional and high energy X-ray photoelectron spectroscopy (XPS) has been used so as to understand the stability and the chemical composition of the EEI. The results reveal that a bilayer EEI is formed at full Na+ extracted state of charge (SOC - 4.7 V vs. Na/Na+), with semi-organic-rich species found in the subsurface region close to the electrode while more organic species are formed in the outermost surface region close to the electrolyte. Meanwhile, after full Na+ insertion (SOC - 3.0 V vs. Na/Na+) an additional outermost inorganic overlayer is formed which is composed of sodium carbonate and sodium fluorophosphate. Additionally, this inorganic-rich EEI is dissolving upon oxidation / charge process - affecting the outermost ~10 nm of the EEI. Despite this dynamic behavior of the EEI, the Na4Co3(PO4)2P2O7 positive electrode delivers excellent cyclability (94% capacity retention after 100 cycles at 0.2C), proving that it can be a good candidate as positive electrode material for SIBs
Influence of the Current Density on the Interfacial Reactivity of Layered Oxide Cathodes for Sodium‐Ion Batteries
No full textThe full commercialization of sodium-ion batteries (SIBs) is still hindered by their lower electrochemical performance and higher cost ($ W−1 h−1) with respect to lithium-ion batteries. Understanding the electrode–electrolyte interphase formation in both electrodes (anode and cathode) is crucial to increase the cell performance and, ultimately, reduce the cost. Herein, a step forward regarding the study of the cathode–electrolyte interphase (CEI) by means of X-ray photoelectron spectroscopy (XPS) has been carried out by correlating the formation of the CEI on the P2-Na0.67Mn0.8Ti0.2O2 layered oxide cathode with the cycling rate. The results reveal that the applied current density affects the concentration of the formed interphase species, as well as the thickness of CEI, but not its chemistry, indicating that the electrode–electrolyte interfacial reactivity is mainly driven by thermodynamic factors
sj-tif-2-lup-10.1177_09612033221091401.tif – Supplemental Material for Treatment with low-dose prednisone in refractory obstetric antiphospholipid syndrome: A retrospective cohort study and meta-analysis
No full textSupplemental Material, sj-tif-2-lup-10.1177_09612033221091401.tif for Treatment with low-dose prednisone in refractory obstetric antiphospholipid syndrome: A retrospective cohort study and meta-analysis by Leyre Riancho-Zarrabeitia, Laura Lopez-Marin, Pedro Muñoz Cacho, Marcos López-Hoyos, Rafael del Barrio, Ana Haya and Víctor M Martínez-Taboada in Lupus</p
Operando pH measurements decipher H+/Zn2+intercalation chemistry in high-performance aqueous Zn/δ-V2O5batteries
No full textVanadium oxides have been recognized to be among the most promising positive electrode materials for aqueous zinc metal batteries (AZMBs). However, their underlying intercalation mechanisms are still vigorously debated. To shed light on the intercalation mechanisms, high-performance δ-V2O5 is investigated as a model compound. Its structural and electrochemical behaviors in the designed cells with three different electrolytes, i.e., 3 m Zn(CF3SO3)2/water, 0.01 M H2SO4/water, and 1 M Zn(CF3SO3)2/acetonitrile, demonstrate that the conventional structural and elemental characterization methods cannot adequately clarify the separate roles of H+ and Zn2+ intercalations in the Zn(CF3SO3)2/water electrolyte. Thus, an operando pH determination method is developed and used toward Zn/δ-V2O5 AZMBs. This method indicates the intercalation of both H+ and Zn2+ into δ-V2O5 and uncovers an unusual H+/Zn2+-exchange intercalation-deintercalation mechanism. Density functional theory calculations further reveal that the H+/Zn2+ intercalation chemistry is a consequence of the variation of the electrochemical potential of Zn2+ and H+ during the electrochemical intercalation/release
Cathode-Electrolyte Interphase in a LiTFSI/Tetraglyme Electrolyte Promoting the Cyclability of V2O5
No full textV2O5, one of the earliest intercalation-type cathode materials investigated as a Li+ host, is characterized by an extremely high theoretical capacity (441 mAh g-1). However, the fast capacity fading upon cycling in conventional carbonate-based electrolytes is an unresolved issue. Herein, we show that using a LiTFSI/tetraglyme (1:1 in mole ratio) electrolyte yields a highly enhanced cycling ability of V2O5 (from 20% capacity retention to 80% after 100 cycles at 50 mA g-1 within 1.5-4.0 V vs Li+/Li). The improved performance mostly originates from the V2O5 electrode itself, since refreshing the electrolyte and the lithium electrode of the cycled cells does not help in restoring the V2O5 electrode capacity. Electrochemical impedance spectroscopy (EIS), post-mortem scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the origin of the improved electrochemical behavior. The results demonstrate that the enhanced cyclability is a consequence of a thinner but more stable cathode-electrolyte interphase (CEI) layer formed in LiTFSI/tetraglyme with respect to the one occurring in 1 M LiPF6 in EC/DMC (1:1 in weight ratio, LP30). These results show that the cyclability of V2O5 can be effectively improved by simple electrolyte engineering. At the same time, the uncovered mechanism further reveals the vital role of the CEI on the cyclability of V2O5, which can be helpful for the performance optimization of vanadium-oxide-based batteries
sj-tif-1-lup-10.1177_09612033221091401.tif – Supplemental Material for Treatment with low-dose prednisone in refractory obstetric antiphospholipid syndrome: A retrospective cohort study and meta-analysis
No full textSupplemental Material, sj-tif-1-lup-10.1177_09612033221091401.tif for Treatment with low-dose prednisone in refractory obstetric antiphospholipid syndrome: A retrospective cohort study and meta-analysis by Leyre Riancho-Zarrabeitia, Laura Lopez-Marin, Pedro Muñoz Cacho, Marcos López-Hoyos, Rafael del Barrio, Ana Haya and Víctor M Martínez-Taboada in Lupus</p
Structure, Composition, Transport Properties, and Electrochemical Performance of the Electrode‐Electrolyte Interphase in Non‐Aqueous Na‐Ion Batteries
No full textRechargeable Li-ion battery technology has progressed due to the development of a suitable combination of electroactive materials, binders, electrolytes, additives, and electrochemical cycling protocols that resulted in the formation of a stable electrode-electrolyte interphase. It is expected that Na-ion technology will attain a position comparable to Li-ion batteries dependent on advancements in establishing a stable electrode-electrolyte interphase. However, Li and Na are both alkali metals with similar characteristics, yet the physicochemical properties of these systems differ. For this reason, a detailed study on the electrode-electrolyte interphase properties, composition, and structure is required to understand the factors that influence the battery\u27s behavior. Herein, the research that has been performed on the electrode-electrolyte interphase for both anode and cathode in the most important families of electrode materials, including carbonate ester-based and advanced electrolytes such as ether-based carbonates and ionic liquids is presented
Role of the voltage window on the capacity retention of P2-Na2/3[Fe1/2Mn1/2]O2 cathode material for rechargeable sodium-ion batteries
No full textP2-Na2/3[Fe1/2Mn1/2]O2 layered oxide is a promising high energy density cathode material for sodium-ion batteries. However, one of its drawbacks is the poor long-term stability in the operating voltage window of 1.5–4.25 V vs Na+/Na that prevents its commercialization. In this work, additional light is shed on the origin of capacity fading, which has been analyzed using a combination of experimental techniques and theoretical methods. Electrochemical impedance spectroscopy has been performed on P2-Na2/3[Fe1/2Mn1/2]O2 half-cells operating in two different working voltage windows, one allowing and one preventing the high voltage phase transition occurring in P2-Na2/3[Fe1/2Mn1/2]O2 above 4.0 V vs Na+/Na; so as to unveil the transport properties at different states of charge and correlate them with the existing phases in P2-Na2/3[Fe1/2Mn1/2]O2. Supporting X-ray photoelectron spectroscopy experiments to elucidate the surface properties along with theoretical calculations have concluded that the formed electrode-electrolyte interphase is very thin and stable, mainly composed by inorganic species, and reveal that the structural phase transition at high voltage from P2- to “Z”/OP4-oxygen stacking is associated with a drastic increased in the bulk electronic resistance of P2-Na2/3[Fe1/2Mn1/2]O2 electrodes which is one of the causes of the observed capacity fading
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
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