elemental-sensitive-detection-chemistry-batteries-through-soft-x-ray

Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering

Energy storage has become more and more a limiting factor of today's sustainable energy applications, including electric vehicles and green electric grid ...

Lawrence Berkeley National Laboratory

Through soft X-ray absorption spectroscopy, hard X-ray Raman scattering, and theoretical simulations, we provide the most in-depth and systematic study of the phase transformation and (de)lithiation effect on electronic structure in Li(x)FePO(4) nanoparticles and single crystals. Soft X-ray reveals directly the valence states of Fe 3d electrons in the vicinity of Fermi level, which is sensitive to the local lattice distortion, but more importantly offers detailed information on the evolution of electronic states at different electrochemical stages. The soft X-ray spectra of Li(x)FePO(4) nanoparticles evolve vividly with the (de)lithiation level. The spectra fingerprint the (de)lithiation process with rich information on Li distribution, valency, spin states, and crystal field. The high-resolution spectra reveal a subtle but critical deviation from two-phase transformation in our electrochemically prepared samples. In addition, we performed both first-principles calculations and multiplet simulations of the spectra and quantitatively determined the 3d valence states that are completely redistributed through (de)lithiation. This electronic reconfiguration was further verified by the polarization-dependent spectra collected on LiFePO(4) single crystals, especially along the lithium diffusion direction. The evolution of the 3d states is overall consistent with the local lattice distortion and provides a fundamental picture of the (de)lithiation effects on electronic structure in the Li(x)FePO(4) system.

Phase transformation and lithiation effect on electronic structure of Li(x)FePO4: an in-depth study by soft X-ray and simulations.

Gr&acirc;ce &agrave; la spectroscopie d&#39;absorption des rayons x mou, la diffusion Raman des rayons x dure et simulations th&eacute;oriques, nous fournissons l&#39;&eacute;tude plus approfondie et syst&eacute;matique de la transformation de phase et l&#39;effet lithiation (de) sur la structure &eacute;lectronique de nanoparticules de Li(x)FePO(4) et de monocristaux. Rayons x mou r&eacute;v&egrave;lent directement les &Eacute;tats de valence de Fe &eacute;lectrons 3d &agrave; proximit&eacute; du niveau de Fermi, qui est sensible &agrave; la d&eacute;formation du r&eacute;seau local, mais plus offre surtout des informations d&eacute;taill&eacute;es sur l&#39;&eacute;volution des &Eacute;tats &eacute;lectroniques &agrave; diff&eacute;rents stades &eacute;lectrochimiques. Les spectres de rayons x mous de nanoparticules Li(x)FePO(4) &eacute;voluent avec &eacute;clat avec le niveau de lithiation (de). Les spectres d&#39;empreintes digitales le processus (de) de lithiation avec riches informations sur Li distribution, Valence, &Eacute;tats de spin et champ cristallin. Les spectres de haute r&eacute;solution r&eacute;v&egrave;lent une d&eacute;viation subtile mais critique de transformation en deux phases dans nos &eacute;chantillons pr&eacute;par&eacute;s par voie &eacute;lectrochimique. En outre, nous avons effectu&eacute; les calculs des premiers principes et des simulations de multiplet des spectres et d&eacute;termin&eacute; quantitativement les &Eacute;tats 3d de valence qui sont compl&egrave;tement redistribu&eacute;s par le biais de lithiation (de). Cette reconfiguration &eacute;lectronique a &eacute;galement v&eacute;rifi&eacute;e les spectres d&eacute;pendant de la polarisation recueillies sur monocristaux LiFePO(4), surtout le long de la direction de diffusion au lithium. L&#39;&eacute;volution des &Eacute;tats 3d est globalement conforme &agrave; la distorsion du r&eacute;seau local et fournit une image fondamentale de la (de) lithiation effets sur la structure &eacute;lectronique du syst&egrave;me Li(x)FePO(4).

La phase de transformation et la lithiation effet sur la structure &eacute;lectronique de Li (x) FePO4 : une &eacute;tude approfondie par les doux rayons x et les simulations.

Attraverso la spettroscopia di assorbimento di raggi x molle, scattering Raman di raggi x duri e simulazioni teoriche, forniamo lo studio pi&ugrave; approfondito e sistematico della trasformazione di fase e (de) lithiation effetto sulla struttura elettronica di nanoparticelle Li(x)FePO(4) e cristalli singoli. Raggi x molli rivela direttamente gli Stati di valenza del Fe elettroni 3d in prossimit&agrave; del livello di Fermi, che &egrave; sensibile alla distorsione reticolare locale, ma pi&ugrave; d&#39;importanza offre informazioni dettagliate sull&#39;evoluzione degli Stati elettronici nelle diverse fasi di elettrochimiche. Gli spettri dei raggi x molli di nanoparticelle Li(x)FePO(4) evolvono vivacemente con il livello di lithiation (de). Gli spettri di impronte digitali il processo di (de) lithiation con ricche informazioni sulla distribuzione, Valenza, Stati di spin e campo di cristallo Li. Gli spettri ad alta risoluzione rivelano una sottile ma fondamentale deviazione dalla trasformazione bifase nei nostri campioni elettrochimicamente preparati. Inoltre, abbiamo eseguito sia i principi primi calcoli e simulazioni multipletto degli spettri e quantitativamente determinato gli Stati di valenza 3d che sono completamente ridistribuiti attraverso lithiation (de). Questa riconfigurazione elettronica &egrave; stato ulteriormente verificato dallo spettro di polarizzazione-dipendente raccolto su singoli cristalli LiFePO(4), soprattutto lungo la direzione di diffusione del litio. L&#39;evoluzione degli Stati 3d &egrave; in generale coerente con la distorsione del reticolo locale e fornisce un quadro fondamentale di (de) lithiation effetti sulla struttura elettronica del sistema Li(x)FePO(4).

Fase di trasformazione e lithiation effetto sulla struttura elettronica di Li (x) FePO4: uno studio approfondito da morbido a raggi x e simulazioni.

Li(2)O(2), Li(2)CO(3), and Li(2)O are three critical compounds in lithium-air and lithium-ion energy storage systems. Extensive measurements have been carried out to study the chemical species and their evolutions at difference stages of the device operation. While x-ray spectroscopy has been demonstrated to be one of the most powerful tools for such purpose, no systematic study on the irradiation effects have been reported. Here we carry out extensive time, position, and irradiation dependent Li K-edge soft x-ray absorption spectroscopy on these compounds with so far the best energy resolution. The ultra-high resolution in the current study allows the features in the absorption spectra to be well-resolved. The spectral lineshape thus serves as the fingerprints of these compounds, enabling the tracking of their evolution under x-ray irradiation. We found that both Li(2)O(2) and Li(2)CO(3) evidently evolve towards Li(2)O under the soft x-ray irradiation with Li(2)CO(3) exhibiting a surprisingly higher sensitivity to x-rays than Li(2)O(2). On the other hand, Li(2)O remains the most stable compound despite experiencing substantial irradiation dose. We thus conclude that high resolution soft x-ray spectroscopy could unambiguously fingerprint different chemical species, but special cautions on irradiation effects would be needed in performing the experiments and interpreting the data properly.

Soft x-ray irradiation effects of Li₂O₂, Li₂CO₃ and Li₂O revealed by absorption spectroscopy.

Dense LLZO (Al-substituted Li7La3Zr2O12) pellets were processed in controlled atmospheres to investigate the relationships between the surface chemistry and interfacial behavior in lithium cells. Laser induced breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, synchrotron X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) studies revealed that Li2CO3 was formed on the surface when LLZO pellets were exposed to air. The distribution and thickness of the Li2CO3 layer were estimated by a combination of bulk and surface sensitive techniques with various probing depths. First-principles thermodynamic calculations confirmed that LLZO has an energetic preference to form Li2CO3 in air. Exposure to air and the subsequent formation of Li2CO3 at the LLZO surface is the source of the high interfacial impedances observed in cells with lithium electrodes. Surface polishing can effectively remove Li2CO3 and dramatically improve the interfacial properties. Polished samples in lithium cells had an area specific resistance (ASR) of only 109 Ω cm(2) for the LLZO/Li interface, the lowest reported value for Al-substituted LLZO. Galvanostatic cycling results obtained from lithium symmetrical cells also suggest that the quality of the LLZO/lithium interface has a significant impact on the device lifetime. 

The origin of high electrolyte-electrode interfacial resistances in lithium cells containing garnet type solid electrolytes.

The aqueous sodium-ion battery system is a safe and low-cost solution for large-scale energy storage, because of the abundance of sodium and inexpensive aqueous electrolytes. Although several positive electrode materials, for example, Na₀.₄₄MnO₂, were proposed, few negative electrode materials, for example, activated carbon and NaTi₂(PO₄)₃, are available. Here we show that Ti-substituted Na₀.₄₄MnO₂ (Na₀.₄₄[Mn₁-xTix]O₂) with tunnel structure can be used as a negative electrode material for aqueous sodium-ion batteries. This material exhibits superior cyclability even without the special treatment of oxygen removal from the aqueous solution. Atomic-scale characterizations based on spherical aberration-corrected electron microscopy and ab initio calculations are utilized to accurately identify the Ti substitution sites and sodium storage mechanism. Ti substitution tunes the charge ordering property and reaction pathway, significantly smoothing the discharge/charge profiles and lowering the storage voltage. Both the fundamental understanding and practical demonstrations suggest that Na₀.₄₄[Mn₁-xTix]O₂ is a promising negative electrode material for aqueous sodium-ion batteries.

Ti-substituted tunnel-type Na₀.₄₄MnO₂ oxide as a negative electrode for aqueous sodium-ion batteries.

LiFePO4 is a battery cathode material with high safety standards due to its unique electronic structure. We performed systematic experimental and theoretical studies based on soft X-ray emission, absorption, and hard X-ray Raman spectroscopy of LixFePO4 nanoparticles and single crystals. The results clearly show a non-rigid electron-state reconfiguration of both the occupied and unoccupied Fe-3d and O-2p states during the (de)lithiation process. We focus on the energy configurations of the occupied states of LiFePO4 and the unoccupied states of FePO4, which are the critical states where electrons are removed and injected during the charge and discharge process, respectively. In LiFePO4, the soft X-ray emission spectroscopy shows that, due to the Coulomb repulsion effect, the occupied Fe-3d states with the minority spin sit close to the Fermi level. In FePO4, the soft X-ray absorption and hard X-ray Raman spectroscopy show that the unoccupied Fe-3d states again sit close to the Fermi level. These critical 3d electron state configurations are consistent with the calculations based on modified Becke and Johnson potentials GGA+U (MBJGGA+U) framework, which improves the overall lineshape prediction compared with the conventionally used GGA+U method. The combined experimental and theoretical studies show that the non-rigid electron state reshuffling guarantees the stability of oxygen during the redox reaction throughout the charge and discharge process of LiFePO4 electrodes, leading to the intrinsic safe performance of the electrodes. 

Why LiFePO4 is a safe battery electrode: Coulomb repulsion induced electron-state reshuffling upon lithiation.

High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.

Conductive Polymer Binder for High-Tap-Density Nanosilicon Material for Lithium-Ion Battery Negative Electrode Application.

High quality single-crystal fcc-Co(x)(Mg(y)Zn(1-y))(1-x)O(1-v) epitaxial thin films with high Co concentration up to x = 0.5 have been fabricated by molecular beam epitaxy. Systematic magnetic property characterization and soft X-ray absorption spectroscopy analysis indicate that the coexistence of ferromagnetic regions, superparamagnetic clusters, and non-magnetic boundaries in the as-prepared Co(x)(Mg(y)Zn(1-y))(1-x)O(1-v) films is a consequence of the intrinsic inhomogeneous distribution of oxygen vacancies. Furthermore, the relative strength of multiple phases could be modulated by controlling the oxygen partial pressure during sample preparation. Armed with both controllable magnetic properties and tunable band-gap, Co(x)(Mg(y)Zn(1-y))(1-x)O(1-v) films may have promising applications in future spintronics.

Oxygen vacancies controlled multiple magnetic phases in epitaxial single crystal Co0.5(Mg0.55Zn0.45)0.5O(1-v) thin films.

The atomic-scale origin of the unusually high performance and long-term stability of wurtzite p-GaN oriented nanowire arrays is revealed. Nitrogen termination of both the polar (0001¯) top face and the nonpolar (101¯0) side faces of the nanowires is essential for long-term stability and high efficiency. Such a distinct atomic configuration ensures not only stability against (photo) oxidation in air and in water/electrolyte but, as importantly, also provides the necessary overall reverse crystal polarization needed for efficient hole extraction in p-GaN.

Atomic-Scale Origin of Long-Term Stability and High Performance of p-GaN Nanowire Arrays for Photocatalytic Overall Pure Water Splitting.

We present a picosecond time-resolved X-ray absorption spectroscopy (tr-XAS) setup designed for synchrotron-based studies of interfacial photochemical dynamics. The apparatus combines a high power, variable repetition rate picosecond laser system with a time-resolved X-ray fluorescence yield detection technique. Time-tagging of the detected fluorescence signals enables the parallel acquisition of X-ray absorption spectra at a variety of pump-probe delays employing the well-defined time structure of the X-ray pulse trains. The viability of the setup is demonstrated by resolving dynamic changes in the fine structure near the O1s X-ray absorption edge of cuprous oxide (CuO) after photo-excitation with a 355 nm laser pulse. Two distinct responses are detected. A pronounced, quasi-static, reversible change of the CuO O1s X-ray absorption spectrum by up to ∼30% compared to its static line shape corresponds to a redshift of the absorption edge by ∼1 eV. This value is small compared to the 2.2 eV band gap of CuO but in agreement with previously published results. The lifetime of this effect exceeds the laser pulse-to-pulse period of 8 μs, resulting in a quasi-static spectral change that persists as long as the sample is exposed to the laser light, and completely vanishes once the laser is blocked. Additionally, a short-lived response corresponding to a laser-induced shift of the main absorption line by ∼2 eV to lower energies appears within <200 ps and decays with a characteristic timescale of 43 ± 5 ns. Both the picosecond rise and nanosecond decay of this X-ray response are simultaneously captured by making use of a time-tagging approach - highlighting the prospects of the experimental setup for efficient probing of the electronic and structural dynamics in photocatalytic systems on multiple timescales.

Towards efficient time-resolved X-ray absorption studies of electron dynamics at photocatalytic interfaces.

Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (∼1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered MnO pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of MnO suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn/Mn redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of MnO.

Bivalence MnO with hydroxylated interphase for high-voltage aqueous sodium-ion storage.

Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionized the soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostly dedicated designs, which cannot be easily adopted for applications with diverging demands. Here we present a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme that uses modular mechanical components. The spectrometer's optics chamber can be used with gratings operated in either inside or outside orders, and the detector assembly can be reconfigured accordingly. The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolving power when using small source (∼1μm) and detector pixels (∼5μm) with high line density gratings (∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers with slightly different design goals and optical parameters in this paper. We show that the spectrometer with high throughput and large energy window is particularly useful for studying the sustainable energy materials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of battery cathode material LiNiCoMnO can be produced in few hours using such a spectrometer. Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across the elemental absorption edges to determine various spectral features like the localized dd excitations and non-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studying such RIXS maps could reveal novel transition metal redox in battery compounds that are sometimes hard to be unambiguously identified in X-ray absorption and emission spectra. We propose that this modular spectrometer design can serve as the platform for further customization to meet specific scientific demands.

Modular soft x-ray spectrometer for applications in energy sciences and quantum materials.

An endstation with two high-efficiency soft x-ray spectrographs was developed at Beamline 8.0.1 of the Advanced Light Source, Lawrence Berkeley National Laboratory. The endstation is capable of performing soft x-ray absorption spectroscopy, emission spectroscopy, and, in particular, resonant inelastic soft x-ray scattering (RIXS). Two slit-less variable line-spacing grating spectrographs are installed at different detection geometries. The endstation covers the photon energy range from 80 to 1500 eV. For studying transition-metal oxides, the large detection energy window allows a simultaneous collection of x-ray emission spectra with energies ranging from the O K-edge to the Ni L-edge without moving any mechanical components. The record-high efficiency enables the recording of comprehensive two-dimensional RIXS maps with good statistics within a short acquisition time. By virtue of the large energy window and high throughput of the spectrographs, partial fluorescence yield and inverse partial fluorescence yield signals could be obtained for all transition metal L-edges including Mn. Moreover, the different geometries of these two spectrographs (parallel and perpendicular to the horizontal polarization of the beamline) provide contrasts in RIXS features with two different momentum transfers.

High-efficiency in situ resonant inelastic x-ray scattering (iRIXS) endstation at the Advanced Light Source.

Materials can be transformed from one crystalline phase to another by using an electric field to control ion transfer, in a process that can be harnessed in applications such as batteries, smart windows and fuel cells. Increasing the number of transferrable ion species and of accessible crystalline phases could in principle greatly enrich material functionality. However, studies have so far focused mainly on the evolution and control of single ionic species (for example, oxygen, hydrogen or lithium ions). Here we describe the reversible and non-volatile electric-field control of dual-ion (oxygen and hydrogen) phase transformations, with associated electrochromic and magnetoelectric effects. We show that controlling the insertion and extraction of oxygen and hydrogen ions independently of each other can direct reversible phase transformations among three different material phases: the perovskite SrCoO (ref. 12), the brownmillerite SrCoO (ref. 13), and a hitherto-unexplored phase, HSrCoO. By analysing the distinct optical absorption properties of these phases, we demonstrate selective manipulation of spectral transparency in the visible-light and infrared regions, revealing a dual-band electrochromic effect that could see application in smart windows. Moreover, the starkly different magnetic and electric properties of the three phases-HSrCoO is a weakly ferromagnetic insulator, SrCoO is a ferromagnetic metal, and SrCoO is an antiferromagnetic insulator-enable an unusual form of magnetoelectric coupling, allowing electric-field control of three different magnetic ground states. These findings open up opportunities for the electric-field control of multistate phase transformations with rich functionalities.

Electric-field control of tri-state phase transformation with a selective dual-ion switch.

We describe a new experimental technique that allows for soft x-ray spectroscopy studies (∼100-1000 eV) of high pressure liquid (∼100 bars). We achieve this through a liquid cell with a 100 nm-thick SiN membrane window, which is sandwiched by two identical O-rings for vacuum sealing. The thin SiN membrane allows soft x-rays to penetrate, while separating the high-pressure liquid under investigation from the vacuum required for soft x-ray transmission and detection. The burst pressure of the SiN membrane increases with decreasing size and more specifically is inversely proportional to the side length of the square window. It also increases proportionally with the membrane thickness. Pressures > 60 bars could be achieved for 100 nm-thick square SiN windows that are smaller than 65 μm. However, above a certain pressure, the failure of the Si wafer becomes the limiting factor. The failure pressure of the Si wafer is sensitive to the wafer thickness. Moreover, the deformation of the SiN membrane is quantified using vertical scanning interferometry. As an example of the performance of the high-pressure liquid cell optimized for total-fluorescence detected soft x-ray absorption spectroscopy (sXAS), the sXAS spectra at the Ca L edge (∼350 eV) of a CaCl aqueous solution are collected under different pressures up to 41 bars.

Soft x-ray spectroscopy of high pressure liquid.

The demand of sustainable power supply requires high-performance cost-effective energy storage technologies. Here we report a high-rate long-life low-cost sodium-ion battery full-cell system by innovating both the anode and the electrolyte. The redox couple of manganese(I/II) in Prussian blue analogs enables a high-rate and stable anode. Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering provide direct evidence suggesting the existence of monovalent manganese in the charged anode. There is a strong hybridization between cyano ligands and manganese-3d states, which benefits the electronic property for improving rate performance. Additionally, we employ an organic-aqueous cosolvent electrolyte to solve the long-standing solubility issue of Prussian blue analogs. A full-cell sodium-ion battery with low-cost Prussian blue analogs in both electrodes and co-solvent electrolyte retains 95% of its initial discharge capacity after 1000 cycles at 1C and 95% depth of discharge. The revealed manganese(I/II) redox couple inspires conceptual innovations of batteries based on atypical oxidation states.

Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries.

Recent research has explored combining conventional transition-metal redox with anionic lattice oxygen redox as a new and exciting direction to search for high-capacity lithium-ion cathodes. Here, we probe the poorly understood electrochemical activity of anionic oxygen from a material perspective by elucidating the effect of the transition metal on oxygen redox activity. We study two lithium-rich layered oxides, specifically lithium nickel metal oxides where metal is either manganese or ruthenium, which possess a similar structure and discharge characteristics, but exhibit distinctly different charge profiles. By combining X-ray spectroscopy with operando differential electrochemical mass spectrometry, we reveal completely different oxygen redox activity in each material, likely resulting from the different interaction between the lattice oxygen and transition metals. This work provides additional insights into the complex mechanism of oxygen redox and development of advanced high-capacity lithium-ion cathodes.

Article	Year
Phase transformation and lithiation effect on electronic structure of Li(x)FePO4: an in-depth study by soft X-ray and simulations. Journal of the American Chemical Society\| PubMed ID: 22835006	2012
Soft x-ray irradiation effects of Li₂O₂, Li₂CO₃ and Li₂O revealed by absorption spectroscopy. PloS one\| PubMed ID: 23145116	2012
The origin of high electrolyte-electrode interfacial resistances in lithium cells containing garnet type solid electrolytes. Physical chemistry chemical physics : PCCP\| PubMed ID: 25057850	2014
Ti-substituted tunnel-type Na₀.₄₄MnO₂ oxide as a negative electrode for aqueous sodium-ion batteries. Nature communications\| PubMed ID: 25806965	2015
Why LiFePO4 is a safe battery electrode: Coulomb repulsion induced electron-state reshuffling upon lithiation. Physical chemistry chemical physics : PCCP\| PubMed ID: 26388021	2015
Conductive Polymer Binder for High-Tap-Density Nanosilicon Material for Lithium-Ion Battery Negative Electrode Application. Nano letters\| PubMed ID: 26599387	2015
Oxygen vacancies controlled multiple magnetic phases in epitaxial single crystal Co0.5(Mg0.55Zn0.45)0.5O(1-v) thin films. Scientific reports\| PubMed ID: 27062992	2016
Atomic-Scale Origin of Long-Term Stability and High Performance of p-GaN Nanowire Arrays for Photocatalytic Overall Pure Water Splitting. Advanced materials (Deerfield Beach, Fla.)\| PubMed ID: 27456856	2016
Towards efficient time-resolved X-ray absorption studies of electron dynamics at photocatalytic interfaces. Faraday discussions\| PubMed ID: 27711854	2016
Bivalence MnO with hydroxylated interphase for high-voltage aqueous sodium-ion storage. Nature communications\| PubMed ID: 27845345	2016
Modular soft x-ray spectrometer for applications in energy sciences and quantum materials. The Review of scientific instruments\| PubMed ID: 28147697	2017
High-efficiency in situ resonant inelastic x-ray scattering (iRIXS) endstation at the Advanced Light Source. The Review of scientific instruments\| PubMed ID: 28372380	2017
Electric-field control of tri-state phase transformation with a selective dual-ion switch. Nature\| PubMed ID: 28569818	2017
Soft x-ray spectroscopy of high pressure liquid. The Review of scientific instruments\| PubMed ID: 29390687	2018
Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries. Nature communications\| PubMed ID: 29491414	2018
Elucidating anionic oxygen activity in lithium-rich layered oxides. Nature communications\| PubMed ID: 29507369	2018

Ruimin Qiao

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