Role of the voltage window on the capacity retention of P2-Na2/3[Fe1/2Mn1/2]O2 cathode material for rechargeable sodium-ion batteries

[EN] P2-Na-2/3[Fe1/2Mn1/2]O-2 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-Na-2/3[Fe1/2Mn1/2]O-2 half-cells operating in two different working voltage windows, one allowing and one preventing the high voltage phase transition occurring in P2-Na-2/3[Fe1/2Mn1/2]O-2 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-Na-2/3[Fe1/2Mn1/2]O-2. 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-Na-2/3[Fe1/2Mn1/2]O-2 electrodes which is one of the causes of the observed capacity fading. P2-Na-2/3[Fe1/2Mn1/2]O-2 is a promising high energy density cathode material for rechargeable sodium-ion batteries, but its poor long-term stability in the operating voltage window of 1.5-4.25 V vs Na+/Na hinders its commercial application. Here, the authors use a combination of electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and DFT calculations to investigate the origin of the capacity fading, which is attributed to an increase in bulk electronic resistance at high voltage that, among other factors, is nested in a structural phase transition.M.Z. thanks the Government of the Basque Country for Ph.D. funding through a Predoctoral fellowship and her stage at the University of Camerino by "EGONLABUR" Fellowship. B. Acebedo and M. Jauregui are acknowledged for their technical support with material synthesis and powder XRD measurements. O.L. thanks J.X Lian for his insight into generating the DOS graphs. Financial support from the Basque Government (Elkartek20 CIC energiGUNE) and from the Ministerio de Economia y Competitividad of the Spanish Government (ENE2013-44330-R) is also acknowledged

Narrow in-gap states in doped

International audienceBased on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases

Narrow in-gap states in doped

International audienceBased on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases

Are Polymer‐Based Electrolytes Ready for High‐Voltage Lithium Battery Applications? An Overview of Degradation Mechanisms and Battery Performance

High-voltage lithium polymer cells are considered an attractive technology that could out-perform commercial lithium-ion batteries in terms of safety, processability, and energy density. Although significant progress has been achieved in the development of polymer electrolytes for high-voltage applications (> 4 V), the cell performance containing these materials still encounters certain challenges. One of the major limitations is posed by poor cyclability, which is affected by the low oxidative stability of standard polyether-based polymer electrolytes. In addition, the high reactivity and structural instability of certain common high-voltage cathode chemistries further aggravate the challenges. In this review, the oxidative stability of polymer electrolytes is comprehensively discussed, along with the key sources of cell degradation, and provides an overview of the fundamental strategies adopted for enhancing their cyclability. In this regard, a statistical analysis of the cell performance is provided by analyzing 186 publications reported in the last 17 years, to demonstrate the gap between the state-of-the-art and the requirements for high-energy density cells. Furthermore, the essential characterization techniques employed in prior research investigating the degradation of these systems are discussed to highlight their prospects and limitations. Based on the derived conclusions, new targets and guidelines are proposed for further research

Composition-Structure Relationships in the Li-Ion Battery Electrode Material LiNi_0.5Mn_1.5O₄

A study of the correlations between the stoichiometry, secondary phases, and transition metal ordering of LiNi_0.5Mn_1.5O₄ was undertaken by characterizing samples synthesized at different temperatures. Insight into the composition of the samples was obtained by electron microscopy, neutron diffraction, and X-ray absorption spectroscopy. In turn, analysis of cationic ordering was performed by combining neutron diffraction with Li MAS NMR spectroscopy. Under the conditions chosen for the synthesis, all samples systematically showed an excess of Mn, which was compensated by the formation of a secondary rock-salt phase and not via the creation of oxygen vacancies. Local deviations from the ideal 3:1 Mn:Ni ordering were found, even for samples that show the superlattice ordering by diffraction, with different disordered schemes also being possible. The magnetic behavior of the samples was correlated with the deviations from this ideal ordering arrangement. The in-depth crystal-chemical knowledge generated was employed to evaluate the influence of these parameters on the electrochemical behavior of the materials

The Significance of Accelerated Discovery of Advanced Materials to address Societal Challenges

Societal Challenges demand for Advanced Materials, which in turn promise economical potential. Material Acceleration Platforms (MAPs) will decrease their development time and cost. We comment on implications for science, industry and policy concluding with necessary steps towards establishment of MAPs.</p