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For highly active electron transfer and ion diffusion, controlling the surface wettability of electrically and thermally conductive 3D graphene foams (3D GFs) is required. Here, we present ultrasimple and rapid superwettability switching of 3D GFs in a reversible and reproducible manner, mediated by solvent-exclusive microwave arcs. As the 3D GFs are prepared with vapors of nonpolar acetone or polar water exclusively, short microwave radiation (≤10 s) leads to plasma hotspot-mediated production of methyl and hydroxyl radicals, respectively. Upon immediate radical chemisorption, the 3D surfaces become either superhydrophobic (water contact angle = ∼170°) or superhydrophilic (∼0°), and interestingly, the wettability transition can be repeated many times due to the facile exchange between previously chemisorbed and newly introduced radicals via the formation of methanol-like intermediates. When 3D GFs of different surficial polarities are incorporated into electric double-layer capacitors with nonpolar ionic liquids or polar aqueous electrolytes, the polarity matching between graphene surfaces and electrolytes results in ≥548.0 times higher capacitance compared to its mismatching at ≥0.5 A g-1, demonstrating the significance of wettability-controlled 3D GFs.

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Out of practicality, ambient air rather than oxygen is preferred as a fuel in electrochemical systems, but CO2 and H2O present in air cause severe irreversible reactions, such as the formation of carbonates and hydroxides, which typically degrades performance. Herein, we report on a Na-air battery enabled by a reversible carbonate reaction (Na2CO3·xH2O, x = 0 or 1) in Nasicon solid electrolyte (Na3Zr2Si2PO12) that delivers a much higher discharge potential of 3.4 V than other metal-air batteries resulting in high energy density and achieves > 86 % energy efficiency at 0.1 mA cm-2 over 100 cycles. This cell design takes advantage of moisture in ambient air to form an in-situ catholyte via the deliquescent property of NaOH. As a result, not only reversible electrochemical reaction of Na2CO3·xH2O is activated but also its kinetics is facilitated. Our results demonstrate the reversible use of free ambient air as a fuel, enabled by the reversible electrochemical reaction of carbonates with a solid electrolyte.

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Multielectron semiconductor quantum dots (QDs) provide a novel platform to study the Coulomb interaction-driven, spatially localized electron states of Wigner molecules (WMs). Although Wigner-molecularization has been confirmed by real-space imaging and coherent spectroscopy, the open system dynamics of the strongly correlated states with the environment are not yet well understood. Here, we demonstrate efficient control of spin transfer between an artificial three-electron WM and the nuclear environment in a GaAs double QD. A Landau-Zener sweep-based polarization sequence and low-lying anticrossings of spin multiplet states enabled by Wigner-molecularization are utilized. Combined with coherent control of spin states, we achieve control of magnitude, polarity, and site dependence of the nuclear field. We demonstrate that the same level of control cannot be achieved in the non-interacting regime. Thus, we confirm the spin structure of a WM, paving the way for active control of correlated electron states for application in mesoscopic environment engineering.

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Low-cost Fe can be used for forming cation-disordered rocksalt Li-excess (DRX) materials instead of high-cost d0 -species and then the Fe-based DRX can be promising electrode materials because they can theoretically achieve high capacity, resulting from additional oxygen redox reaction and stable cation-disordered structure. However, Fe-based DRX materials suffer from large voltage hysteresis, low electrochemical activity, and poor cyclability, so it is highly challenging to utilize them as practical electrode materials for a cell. Here, novel high-capacity Li-Fe-Ti-Mo electrode materials (LFTMO) with high average discharge voltage and reasonable stability are reported. The effect of Ti/Mo on electrochemical reactions in Fe-based DRX materials (LFTMO) is studied by controlling its composition ratio and using techniques for analyzing the local environment to find the key factors that improve its activity. It is found out that the introduction of appropriate quantity of redox-active Mo4+/5+ to Fe-based DRX materials can help stabilize the oxygen redox reaction via changing a local structure and can suppress a Fe redox reaction, which can cause poor performance. The understandings will help develop high capacity and long cyclability Fe-based DRX electrode materials.

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SiO is a promising anode material for practical Li-ion batteries because it can achieve a much higher capacity than graphite and a better capacity retention than Si. However, SiO suffers from poor initial Coulombic efficiency (ICE). Here, we report on a fundamentally different approach to increase the low ICE of SiO while achieving high capacity and long-term cycle stability compared to previous approaches such as electrochemical/chemical pre-lithiation processes. To enhance the ICE, the long-range/short-range orders of amorphous SiO2 in SiO are increased by the chemical reaction of a small amount of LiOH·H2O even at a much lower temperature (900 °C) than the reported. The increased crystallization of SiO2 substantially reduces the irreversible electrochemical reaction of SiO. As a result, the Li-added SiO shows substantially increased ICE, ∼82.7%, which is one of the highest values. Furthermore, we demonstrate that controlling the crystallization of SiO can enable us to achieve high ICE, high reversible capacity, and superior capacity retention (∼100% at 1C rate for 100 cycles) in SiO simultaneously. The understanding and findings will pave the way to design high-capacity SiO with high ICE and long-term stability for practical high energy density Li batteries.

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Here, we, for the first time, report on the simultaneous enhancement in cubic phase stability and Li-ion conductivity of garnet-type solid electrolytes (SEs) by adding excess Li/Al. The excess Al/Li creates very large grains of up to 170 µm via the segregation of Al at the grain boundaries and enables preferential Al occupation at 96h sites over 24d sites, a behavior contrary to previous observations. The resulting SE shows improved Li-ion conductivity due to the large grain size and less blocking Li pathway caused by different preferential Al occupation. Surprisingly, it is observed that the cubic phase of the garnet-type SE is transformed to the tetragonal phase on the surface and in the bulk under the applied voltage, and the preferential Al occupation enables its cubic phase stability. Under battery operating conditions, the LLZO SE with excess Li/Al can maintain high ionic conductivity due to the cubic phase stability and large grain size. We clearly demonstrate that the cubic phase stability and ionic conductivity of LLZO can be simultaneously improved by excess Li/Al without any post-treatments. The findings and understanding will provide new insights into practical use of the garnet-type SEs for advanced all solid-state batteries.

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We report a single-shot-based projective readout of a semiconductor hybrid qubit formed by three electrons in a GaAs double quantum dot. Voltage-controlled adiabatic transitions between the qubit operations and readout conditions allow high-fidelity mapping of quantum states. We show that a large ratio both in relaxation time vs tunneling time (≈50) and singlet-triplet splitting vs thermal energy (≈20) allows energy-selective tunneling-based spin-to-charge conversion with a readout visibility of ≈92.6%. Combined with ac driving, we demonstrate high visibility coherent Rabi and Ramsey oscillations of a hybrid qubit in GaAs. Further, we discuss the generality of the method for use in other materials, including silicon.

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The electrochemical activity of LiNiO2 at the initial cycle and factors affecting its activity were understood. Even though LiNiO2 can achieve almost theoretical charge capacity, it cannot deliver the theoretical discharge capacity that would result in low 1st Coulombic efficiency (CE). For different upper cut-off voltages at 4.3 and 4.1 V, the 1st CE barely increases. Given that the H2-H3 phase transition occurs at ∼4.2 V, the low 1st CE is not caused by this phase transition but is a result of the additional 3.5 V discharge reaction, which is kinetically limited and thereby not activated even at a reasonable current density. We found out that the several phase transitions during charge/discharge in LiNiO2 barely affect the 3.5 V reaction. Under galvanostatic intermittent titration technique (GITT) conditions, LiNiO2 can achieve ∼250 mAh/g of discharge capacity and 100% CE even with the 4.3 V cut-off voltage by fully activating the 3.5 V reaction. Using neutron diffraction and 6Li nuclear magnetic resonance (NMR) measurements, the sluggish kinetics of the 3.5 V reaction can be ascribed to difficult insertion of Li at the end of the discharge because this reaction can be accompanied by the rearrangement of cations or local structure change in the structure. To achieve high discharge capacity in LiNiO2 with the 4.3 V cut-off voltage, this 3.5 V sluggish reaction should be improved. The finding and understanding underlying the mechanism of the electrochemical activity will stimulate further research on high-capacity Ni-rich layered materials for high-performance Li-ion batteries.

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To meet the growing demand for global electrical energy storage, high-energy-density electrode materials are required for Li-ion batteries. To overcome the limit of the theoretical energy density in conventional electrode materials based solely on the transition metal redox reaction, the oxygen redox reaction in electrode materials has become an essential component because it can further increase the energy density by providing additional available electrons. However, the increase in the contribution of the oxygen redox reaction in a material is still limited due to the lack of understanding its controlled parameters. Here, it is first proposed that Li-transition metals (TMs) inter-diffusion between the phases in Li-rich materials can be a key parameter for controlling the oxygen redox reaction in Li-rich materials. The resulting Li-rich materials can achieve fully exploited oxygen redox reaction and thereby can deliver the highest reversible capacity leading to the highest energy density, ≈1100 Wh kg-1 among Co-free Li-rich materials. The strategy of controlling Li/transition metals (TMs) inter-diffusion between the phases in Li-rich materials will provide feasible way for further achieving high-energy-density electrode materials via enhancing the oxygen redox reaction for high-performance Li-ion batteries.

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All-Solid-State Batteries (ASSBs) that use oxide-based solid electrolytes (SEs) have been considered as a promising energy-storage platform to meet an increasing demand for Li-ion batteries (LIBs) with improved energy density and superior safety. However, high interfacial resistance between particles in the composite electrode and between electrodes and the use of Li metal in the ASBS hinder their practical utilization. Here, we review recent research progress on oxide-based SEs for the ASSBs with respect to the use of Li metal. We especially focus on research progress on garnet-type solid electrolytes (Li7La3Zr2O12) because they have high ionic conductivity, good chemical stability with Li metal, and a wide electrochemical potential window. This review will also discuss Li dendritic behavior in the oxide-based SEs and its relationship with critical current density (CCD). We close with remarks on prospects of ASSB.

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A large number of strains in the Rhizobium radiobacter species complex (biovar 1 Agrobacterium) have been known as causative pathogens for crown gall and hairy root diseases. Strains within this complex were also found as endophytes in many plant species with no symptoms. The aim of this study was to reveal the endophyte variation of this complex and how these endophytic strains differ from pathogenic strains. In this study, we devised a simple but effective screening method by exploiting the high resolution power of mass spectrometry. We screened endophyte isolates from young wheat and barley plants, which are resistant to the diseases, and identified seven isolates from wheat as members of the R. radiobacter species complex. Through further analyses, we assigned five strains to the genomovar (genomic group) G1 and two strains to G7 in R. radiobacter Notably, these two genomovar groups harbor many known pathogenic strains. In fact, the two G7 endophyte strains showed pathogenicity on tobacco, as well as the virulence prerequisites, including a 200-kbp Ri plasmid. All five G1 strains possessed a 500-kbp plasmid, which is present in well-known crown gall pathogens. These data strongly suggest that healthy wheat plants are reservoirs for pathogenic strains of R. radiobacterIMPORTANCE Crown gall and hairy root diseases exhibit very wide host-plant ranges that cover gymnosperm and dicot plants. The Rhizobium radiobacter species complex harbors causative agents of the two diseases. Recently, endophyte isolates from many plant species have been assigned to this species complex. We isolated seven endophyte strains belonging to the species complex from wheat plants and revealed their genomovar affiliations and plasmid profile. The significance of this study is the finding of the genomovar correlation between the endophytes and the known pathogens, the presence of a virulence ability in two of the seven endophyte strains, and the high ratio of the pathogenic strains in the endophyte strains. This study therefore provides convincing evidence that could unravel the mechanism that maintains pathogenic agents of this species and sporadically delivers them to susceptible plants.

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Ni-rich layered electrode materials have attracted great attention as a promising cathode candidate for high-energy-density lithium-ion batteries because of their high capacity and relatively low cost. However, they have been suffering from severe capacity fading for cycles, which can originate from several factors such as the phase transition at the end of charge and disintegration of the particles. Herein, a simple and novel sublimation-induced gas-reacting (SIGR) process has been developed by using elemental sulfur to conformally coat Ni-rich layered materials. The sublimated gas-phase S can react with detrimental residual Li compounds on the surface of the particles. As a result, the reacted layer of LixSyOz phases forms on the outside of the secondary particles and simultaneously in the boundaries between primary particles inside the secondary particles. Compared to other reported surface modification processes, the SIGR-treated Ni-rich materials show substantially increased capacity retention and superior voltage retention by protecting the surface from the electrolyte and mitigating disintegration of the secondary particles. The SIGR process is a simple and scalable solid-state reaction at low temperature to improve the cycling stability of high-capacity Ni-rich electrode materials.

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We determined how Li doping affects the Ni/Mn ordering in high-voltage spinel LiNi0.5Mn1.5O4(LNMO) by using neutron diffraction, TEM image, electrochemical measurements, and NMR data. The doped Li occupies empty octahedral interstitials (16c site) before the ordering transition, and can move to normal octahedral sites (16d (4b) site) after the transition. This movement strongly affects the Ni/Mn ordering transition because Li at 16c sites blocks the ordering transition pathway and Li at 16d (4b) sites affects electrostatic interactions with transition metals. As a result, Li doping increases in the Ni/Mn disordering without the effect of Mn3+ ions even though the Li-doped LNMO undergoes order-disorder transition at 700 °C. Li doping can control the amount of Ni/Mn disordering in the spinel without the negative effect of Mn3+ ions on the electrochemical property.

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[This corrects the article DOI: 10.1002/advs.201500366.].

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FeF3 is a promising cathode material for lithium ion batteries but its poor electronic conductivity makes it non-practical. Here, we significantly improve the electrochemical activity of FeF3 by reducing the strong ionic character of Fe-F with the replacement of some F with N atoms. N-doped nanocrystalline FeF3/C achieves the best electrochemical performance among FeF3 compounds reported to date: ∼95 mA h g-1 at 21.1C discharge rate for 250 cycles. The results illustrate that the poor electronic conductivity of metal fluorides can be controlled by doping and this enables FeF3 or metal fluorides to be practically utilized in possible applications including energy conversion and storage.

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The Na superionic conductor (aka Nasicon, Na1+xZr2SixP3-xO12, where 0 ≤ x ≤ 3) is one of the promising solid electrolyte materials used in advanced molten Na-based secondary batteries that typically operate at high temperature (over ∼270 °C). Nasicon provides a 3D diffusion network allowing the transport of the active Na-ion species (i.e., ionic conductor) while blocking the conduction of electrons (i.e., electronic insulator) between the anode and cathode compartments of cells. In this work, the standard Nasicon (Na3Zr2Si2PO12, bare sample) and 10 at% Na-excess Nasicon (Na3.3Zr2Si2PO12, Na-excess sample) solid electrolytes were synthesized using a solid-state sintering technique to elucidate the Na diffusion mechanism (i.e., grain diffusion or grain boundary diffusion) and the impacts of adding excess Na at relatively low and high temperatures. The structural, thermal, and ionic transport characterizations were conducted using various experimental tools including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). In addition, an ab initio atomistic modeling study was carried out to computationally examine the detailed microstructures of Nasicon materials, as well as to support the experimental observations. Through this combination work comprising experimental and computational investigations, we show that the predominant mechanisms of Na-ion transport in the Nasicon structure are the grain boundary and the grain diffusion at low and high temperatures, respectively. Also, it was found that adding 10 at% excess Na could give rise to a substantial increase in the total conductivity (e.g., ∼1.2 × 10-1 S/cm at 300 °C) of Nasicon electrolytes resulting from the enlargement of the bottleneck areas in the Na diffusion channels of polycrystalline grains.

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Use of compounds that contain fluorine (F) as electrode materials in lithium ion batteries has been considered, but synthesizing single-phase samples of these compounds is a difficult task. Here, it is demonstrated that a simple scalable single-step solid-state process with additional fluorine source can obtain highly pure LiVPO4F. The resulting material with submicron particles achieves very high rate capability ≈100 mAh g-1 at 60 C-rate (1-min discharge) and even at 200 C-rate (18 s discharge). It retains superior capacity, ≈120 mAh g-1 at 10 C charge/10 C discharge rate (6-min) for 500 cycles with >95% retention efficiency. Furthermore, LiVPO4F shows low polarization even at high rates leading to higher operating potential >3.45 V (≈3.6 V at 60 C-rate), so it achieves high energy density. It is demonstrated for the first time that highly pure LiVPO4F can achieve high power capability comparable to LiFePO4 and much higher energy density (≈521 Wh g-1 at 20 C-rate) than LiFePO4 even without nanostructured particles. LiVPO4F can be a real substitute of LiFePO4.

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A scalable solid-state reaction is presented to synthesize an FeF3 cathode material by using PTFE as a source of both fluorine and carbon. The method yields nanocrystalline FeF3/C showing excellent electrochemical performance even without any conducting additive. This method can be utilized for engineering MFs' properties and developing other fluorine compounds.

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In this study, electrochemical behaviors of Li2S such as a large potential barrier at the beginning of the 1st charging process and a continuous increase in potential to ∼4 V during the rest of this process were understood through X-ray photoelectron spectroscopy measurements and electrochemical evaluations for a full utilization of Li2S. The large potential barrier to the 1st charge in Li2S can be caused by the presence of insulating oxidized products (Li2SO3 or Li2SO4-like structures) on the surface; simple surface etching can remove them and thereby reduce the potential barrier. Even though the potential barrier was substantially reduced, the electrochemical activity of Li2S might not be improved due to the continuous increase in potential. This increase in potential was related to the polarization caused by the Li2S-conversion reaction; the polarization can affect the utilization of Li2S in subsequent cycles. We speculate that the increase in potential is related to the decomposition of oxidized products such as Li2CO3-like or Li2O-like structures on the surface of the Li2S particles. These findings indicate that the full utilization of Li2S can be achieved by controlling their surface characteristics, especially the surface oxidation products.

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Surface carbon coating to improve the inherent poor electrical conductivity of lithium iron phosphate (LiFePO4, LFP) has been considered as most efficient strategy. Here, we also report one of the conventional methods for LFP but exhibiting a specific capacity beyond the theoretical value, ultrahigh rate performance, and excellent long-term cyclability: the specific capacity is 171.9 mAh/g (70 µm-thick electrode with ∼10 mg/cm(2) loading mass) at 0.1 C (17 mA/g) and retains 143.7 mAh/g at 10 C (1.7 A/g) and 95.8% of initial capacity at 10 C after 1000 cycles. It was found that the interior conformal N-C coating enhances the intrinsic conductivity of LFP nanorods (LFP NR) and the exterior reduced graphene oxide coating acts as an electrically conducting secondary network to electrically connect the entire electrode. The great electron transport mutually promoted with shorten Li diffusion length on (010) facet exposed LFP NR represents the highest specific capacity value recorded to date at 10 C and ultralong-term cyclability. This conformal carbon coating approach can be a promising strategy for the commercialization of LFP cathode in lithium ion batteries.