Extracting the Redox Orbitals in Li Battery Materials with High-Resolution X-Ray Compton Scattering Spectroscopy
K. Suzuki, B. Barbiellini, Y. Orikasa, N. Go, H. Sakurai, S. Kaprzyk, M. Itou, K. Yamamoto, Y. Uchimoto, Yung Jui Wang, H. Hafiz, A. Bansil, Y. Sakurai
We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn2O4, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.
The overpotential, dissociation rate, electrode potential distributions and current density are suggested in this study to analyze the Nickel Vanadium Redox Flow Battery (NVRFB). Due to its large capacity and ecofriendly properties, NVRFB may be a viable option in the present state of energy constraint and environmental pollution. Due to their low cost and high energy density, nickel-based flow batteries have gained popularity. This study demonstrates that the Ni2+/Ni+ and V5+/V4+ ions have a higher rate of dissociation at the membrane and a lower rate at the inlet, where the electrolyte flow …
A simulation model and design of Titanium Manganese Redox Flow Battery (TMRFB) is proposed to study the distribution of dissociation rate, overpotential, current density, and electrode potential. TMRFB is one of the most promising new energy storages because of its high capacity and eco-friendly characteristics in the current condition of energy scarcity and environmental pollution. Moreover, Mn-based flow batteries are gaining popularity due to their inexpensive cost and high energy density in lieu of all vanadium redox flow batteries which are expensive. This research shows that the surface …
The search for an alternative high-voltage polyanionic cathode material for Li-ion batteries is vital to improve the energy densities beyond the state-of-the-art, where sulfate frameworks form an important class of high-voltage cathode materials due to the strong inductive effect of the S$^{6+}$ ion. Here, we have investigated the mechanism of cationic and/or anionic redox in Li$_x$M(SO$_4$)$_2$ frameworks (M = Mn, Fe, Co, and Ni and 0 $\leq$ x $\leq$ 2) using density functional calculations. Specifically, we have used a combination of Hubbard $U$ corrected strongly constrained and appropriate…
Direct Evidence of Metal-Ligand Redox in Li-ion Battery Positive Electrodes
WMG, University of Warwick（华威大学WMG学院）；The Faraday Institution（法拉第研究所）；School of Science and Engineering, University of Dundee（邓迪大学科学与工程学院）；School of Metallurgy and Materials, University of Birmingham（伯明翰大学冶金与材料学院）；University College Dublin（都柏林大学学院）；Max Planck Institute for Solid State Research（马克斯·普朗克固体研究所）
Realizing reversible reduction-oxidation (Redox) reactions of lattice oxygen in batteries is a promising way to improve the energy and power density. However, conventional oxygen absorption spectroscopy fails to distinguish the critical oxygen chemistry in oxide-based battery electrodes. Therefore, high-efficiency full-range mapping of resonant inelastic X-ray scattering (mRIXS) has been developed as a reliable probe of oxygen redox reactions. Here, based on mRIXS results collected from a series of Li1.17Ni0.21Co0.08Mn0.54O2 electrodes at different electrochemical states and its comparison wit…
Redox Chemistry of LiCoO$_2$, LiNiO$_2$, and LiNi$_{1/3}$Mn$_{1/3}$Co$_{1/3}$O$_2$ Cathodes: Deduced via XPS, DFT+DMFT, and Charge Transfer Multiplet Simulations
The reversibility and cyclability of anionic redox in battery electrodes hold the key to its practical employments. Here, through mapping of resonant inelastic X-ray scattering (mRIXS), we have independently quantified the evolving redox states of both cations and anions in Na2/3Mg1/3Mn2/3O2. The bulk-Mn redox emerges from initial discharge and is quantified by inverse-partial fluorescence yield (iPFY) from Mn-L mRIXS. Bulk and surface Mn activities likely lead to the voltage fade. O-K super-partial fluorescence yield (sPFY) analysis of mRIXS shows 79% lattice oxygen-redox reversibility during…
We present a refined Mn-Zn-H$_2$O Pourbaix diagram with the emphasis on parameters relevant for the Zn/MnO$_2$ rechargeable cells. It maps out boundaries of electrochemical stability for MnO$_2$, ZnMn$_2$O$_4$, ZnMn$_3$O$_7$, and MnOOH. The diagram helps to rationalize experimental observation on processes and phases occurring during charge/discharge, including the position of charge/discharge redox peaks and capacity fade observed in rechargeable aqueous Zn-ion batteries for stationary storage. The proposed Pourbaix diagram is validated by observing the pH-dependent transformation of electrol…
Potassium-ion ($\rm K$-ion) rechargeable batteries; considered to be lucrative low-cost battery options for large-scale and capacious energy storage systems, have been garnering tremendous attention in recent years. However, due to the scarcity of cathode materials that can condone the reversible re-insertion of the large $\rm K$-ions at feasible capacities, the viability of $\rm K$-ion batteries has been greatly undercut. In this paper, we explore a potential cathode material in the $\rm K_2O$-$\rm Fe_2O_3$-$\rm MnO_2$ ternary phase system, that not only demonstrates reversible $\rm K$-ion re…
Investigating the Electronic and Magnetic Properties of Na$_x$Fe$_{1/2}$Mn$_{1/2}$O$_2$ Cathode Materials with X-ray Compton Scattering
LUT University（拉彭兰塔理工大学）；Gunma University（群马大学）；Northeastern University（东北大学）；University of Helsinki（赫尔辛基大学）；University of Oulu（奥卢大学）；University of Jyväskylä（于韦斯屈莱大学）
Developing efficient anode materials with low electrode voltage, high specific capacity and superior rate capability is urgently required on the road to commercially viable sodium-ion batteries (SIBs). Aiming at finding a new SIB anode material, we investigate the electrochemical properties of NaxTiO2 compounds with unprecedented penta-oxygen-coordinated trigonal bipyramid (TB) structures by using the first-principles calculations. Identifying the four different TB phases, we perform the optimization of their crystal structures and calculate their energetics such as sodium binding energy, form…
In Li-ion batteries the electrochemical potential drives the redox reactions occurring at the interface between electrolyte and storage material, typically active particles for porous electrodes, allowing Li ions intercalation/extraction from electrodes. The limiting factor of the process is not solely related to the electrochemical affinity, but also to structural features as the morphology of the electrodes. In this note, the relevance of the electrodes architecture is investigated numerically, in terms of the electro-chemo-mechanical response of a battery cell with homogeneous electrodes an…
Recent debates on the oxygen redox behaviors in battery electrodes have triggered a pressing demand for the reliable detection and understanding of non-divalent oxygen states beyond conventional absorption spectroscopy. Here, enabled by high-efficiency mapping of resonant inelastic X-ray scattering (mRIXS) coupled with first-principles calculations, we report distinct mRIXS features of the oxygen states in Li2O, Li2CO3, and especially, Li2O2, which are successfully reproduced and interpreted theoretically. mRIXS signals are dominated by valence-band decays in Li2O and Li2CO3. However, the oxid…
Enhanced EV market penetration requires durability of the battery with high energy throughput. For long-term cycle stability of silicon-graphite anode capable of high energy density, the reversible redox reactions are crucial. Here, we unveil intriguing electrochemical phenomena such as crosstalk of lithium ion ($Li^{+}$) between silicon and graphite, $Li^{+}$ accumulation in silicon, and capacity depression of graphite under high pressure, which engender the irreversible redox reactions. Active material properties, i.e. the size of silicon and the hardness of graphite, silicon-graphite anode,…
Battery-like supercapacitors feature high power and energy densities as well as long-term capacitance retention. The utilized capacitor electrodes are thus better to have large surface areas, high conductivity, high stability, and importantly be of binder free. Herein, vertically aligned carbon nanofibers (CNFs) coated boron-doped diamonds (BDD) are employed as the capacitor electrodes to construct battery-like supercapacitors. Grown via a thermal chemical vapor deposition technique, these CNFs/BDD hybrid films are binder free and own porous structures, resulting in large surface areas. Meanwh…
A LiFe0.6Mn0.4PO4 (LFMP) cathode exploiting the olivine structure is herein synthesized and characterized in terms of structure, morphology, and electrochemical features in a lithium cell. The material shows reversibility of the electrochemical process which evolves at 3.5 and 4 V versus Li+/Li due to the Fe+2/Fe+3 and Mn+2/Mn+3 redox couples, respectively, as determined by cyclic voltammetry. The LFMP has a well-defined olivine structure revealed by X-ray diffraction, a morphology consisting of submicron particle aggregated into micrometric clusters as indicated by scanning and transmission e…
Na-ion batteries (NIBs), which are recognized as a next-generation alternative technology for energy storage, still suffer from commercialization constraints due to the lack of low-cost, high-performance cathode materials. Since our first discovery of Cu$^{3+}$/Cu$^{2+}$ electrochemistry in 2014, numerous Cu-substituted/doped materials have been designed for NIBs. However for almost ten years, the potential of Cu$^{3+}$/Cu$^{2+}$ electrochemistry has been grossly underappreciated and normally regarded as a semielectrochemically active redox. Here, we re-synthesized P2-Na$_{2/3}$[Cu$_{1/3}$Mn$_…
Spinel Li$_x$Mn$_2$O$_4$ is a key cathode material that is used extensively in commercial Li-ion batteries. A challenge with this material has been that the capacity of the battery fades with cycling, an effect that can be traced to the presence of an anti-ferromagnetic insulator phase in the fully lithiated LiMn$_2$O$_4$ (LMO) and the associated charge disproportionation that drives distortions of the MnO$_6$ octahedra. Here, by combining x-ray magnetic Compton scattering experiments with parallel first-principles computations, we show that the anti-ferromagnetic phase of LMO is surrounded by…
The world is at the cusp of a new era where pivotal importance is being attached to the development of sustainable and high-performance energy storage systems. Potassium-ion batteries are deemed not only as cheap battery candidates, but also as the penultimate high-voltage energy storage systems within the monovalent-cation chemistries. However, their performance and sustainability are undermined by the lack of suitable electrolytes for high-voltage operation particularly due to the limited availability of cathode materials. Here, the potential of ionic liquids based on potassium bis(trifluoro…
