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Metal oxides as electrode materials are of great potential for rechargeable aqueous batteries. However, they suffer from inferior cycle stability and rate capability because of poor electronic and ionic conductivities. Herein, taking vertically orientated Bi 2 O 3 nanoflakes on Ti substrates as examples, we find that the δ-Bi 2 O 3 electrode with plenty of positively charged oxygen defects show remarkably higher specific capacity (264 mA h g −1 ) and far superior rate capability than that of α-Bi 2 O 3 with less oxygen vacancies. Through pinpointing the existence form and the role of oxygen vacancies within the electrochemical processes, we demonstrate that oxygen vacancies in δ-Bi 2 O 3 can not only promote electrical conductivity but also serve as central entrepots collecting OH − groups via electrostatic force effect, which has boosted the oxidation reaction and enhanced the electrochemical properties. Our work merits an excellent Bi 2 O 3 negative electrode material via giving full play to the role of oxygen vacancies in electrochemical energy storage.

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A high cycling stability of dual‐ion batteries is greatly challenging, as the size required for inserting anions matches only insufficiently with the interlayer spacing of graphite which is often used as positive electrode. Herein, an activated expanded graphite (AEG) electrode is successfully prepared via KOH treatment. The loose structure of AEG accommodates the volume expansion caused by anion intercalation, and the large specific surface area facilitates the immersion of electrolyte ions to afford more energy density. Thus, the cycling stability is largely enhanced without losing capacity. Matching with activated carbon as negative electrode and an ionic liquid electrolyte, the assembled dual‐ion battery achieves an energy density of 43 Wh kg−1 at the power density of 756 W kg−1 within a working window of 0–3.6 V. Specifically, the energy density retains 83 % after 50 cycles. Such effective and low‐cost electrode optimization opens up a new route toward full enhancement on the cycling performance of positive electrodes for dual‐ion batteries.

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in Li stripping state influence the succeeding Li plating state; if stress relaxes randomly in Li stripping, inhomogeneous SEI films are broken and disordered Li pits occur. [6] Therefore, more efforts have been made to Li homogeneous nucleation and homoepitaxial growth, e.g., a SEI film originated from ideal nucleation toward free dendrites (see the details in the Supporting Information). [7] To the best of our knowledge, an ideal SEI film enables minimized breaking with releasing of the overwhelming stress during Li stripping, and an effective protection of major sheet SEI film was thereof achieved; back to Li plating, these modified regions enable being self-healing ascribed to lower nucleation barriers ( Figure S1, Supporting Information). [7b,8] Thus, inspired by such principle of zippers, we designed net-like SEI films acting as "zippers" to promote homogeneous Li ion flux. Nucleation barriers are synergistically governed for zipper-like SEI film toward effective controlling of stress. As a result, it leads ultimately to a remarkable enhancement of the stability of Li metal anode.The array pattern on Li surface can be prepared by using mechanical rolling for lower-polarization anode (Figure 1a). [9] In addition, a uniformly distributed rough surface of Li metal may be useful for the suppression of dendrites ( Figure S2, Supporting Information). [10] Therefore, we utilize a simple route to design zipper-like SEI films; the net-like morphology of Li surface was thereof obtained (Figure 1b). After Li metal contacts tightly with Cu/glass, a separation leads to the change of Li surface, correlated with the particular contacting areas due to possible different lithiophilic, thereof yielding various nucleation barrier regions ( Figures S3 and S4 (Supporting Information) and the details: the variation of roughness induces different potentials, and a higher roughness may tailor potential if the Li ion flux is homogeneous enough). [6a,11] In theory, surface patterns cannot remain after the reversible homogeneous growth/ dissolution. For Li metal anode, however, there is always one coating of SEI films on the Li metal surface. Alternatively, SEI films enable being utilized to stabilize the surface pattern. Thus, the reducing polarization in Li plating can be offered during charge/discharge cycling. That is, surface pattern on Li anode should target at controlling SEI film to maintain the stable cycling performance.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aenm.201800650. Li Metal AnodesLi dendrite is responsible for a main failure of Li secondary anode, such as Li-S and Li-O 2 batteries with ultrahigh energy density. [1] Great attention has been paid to protect Li anode by suppressing breaking of ubiquitous solid electrolyte interphase (SEI) films (e.g., spontaneous SEI film contacting with the electrolyte, artificial film in Li metal via epitaxial growth, designed polymer electrolytes, some effective additives, and implanted SEI film). [1g,...

A mixed power-exponential-type potential is proposed for transition metals that overcomes two of the key problems associated with the extended Rydberg potential formalism of the Rose binding-energy relation and the Vinet equation of state. First, it includes naturally the hard-core repulsion at high pressures, and secondly it avoids the convergency problems associated with the series expansion of the Rydberg potential about equilibrium. This potential has been tested against an extensive first-principles database across the transitionmetal series. It should prove invaluable to experimentalists in the fitting of their high-pressure data and to theorists in the development of robust interatomic potentials for atomistic simulations.Both the analysis of experimental high-pressure data and the validity of theoretical atomistic simulations rely on models of the volume dependence of the energy. For example, shortcomings in the parametrization of the binding-energy relation ͑or energy versus volume curve͒ at high pressure render the molecular-dynamics simulations of collision cascades in radiation damage unreliable. 1 Similar problems would arise with the corresponding equation of state ͑or pressure versus volume curve͒. While today routine firstprinciples simulations may be used to gauge the robustness of the binding-energy relations or equations of state, physically based analytic representations are still lacking. In this Rapid Communication, therefore, we analyze two popular descriptions, based on the Rydberg potential, 2 namely the Rose binding-energy relation 3 and the Vinet equation of state, 4 and contrast these with the more physically motivated generalized Morse potential 5 for the case of elemental transition metals. This will allow us to pinpoint the failures of this wide class of equations of state, thereby leading to an improved analytic representation.The Rose binding-energy relation and the Vinet equation of state were published about 20 years ago and made claims of universality across a broad range of materials. 3,4 The expressions of Rose and Vinet turned out to be two different variants of the extended Rydberg potential, 6 namely E erwhere the explicit series expansion extended the original Rydberg potential. 2 E er * is the binding energy scaled by the cohesive energy at equilibrium E 0 , whereas x * = ͑V 1/3 − V 0 1/3 ͒ / l is a scaled distance measuring the difference in the cube root of the volume per atom V 1/3 from its equilibrium value V 0 1/3 . Rose et al. 3 fixed the scaling length l = l r of their bindingenergy relation by constraining Eq. ͑1͒ to satisfy the boundary conditions E * ͑0͒ = −1, E * Ј͑0͒ = 0, and E * Љ͑0͒ = 1, fitting the values of E 0 , V 0 , and K 0 , where K 0 is the equilibrium bulk modulus. The resultant Rose scaling length is found to be l r = V 0 1/3 / ͱ 9V 0 K 0 /E 0 , ͑2͒

Conspectus Syngas conversion is a key platform for efficient utilization of various carbon-containing resources including coal, natural gas, biomass, organic wastes, and even CO2. One of the most classic routes for syngas conversion is Fischer–Tropsch synthesis (FTS), which is already available for commercial application. However, it still remains a grand challenge to tune the product distribution from paraffins to value-added chemicals such as olefins and higher alcohols. Breaking the selectivity limitation of the Anderson–Schulz–Flory (ASF) distribution has been one of the hottest topics in syngas chemistry. Metallic Co0 is a well-known active phase for Co-catalyzed FTS, and the products are dominated by paraffins with a small amount of chemicals (i.e., olefins or alcohols). Specifically, a cobalt carbide (Co2C) phase is typically viewed as an undesirable compound that could lead to deactivation with low activity and high methane selectivity. Although iron carbide (Fe x C) can produce olefins with selectivity up to ∼60%, the fraction of methane is still rather high, and the required high reaction temperature (300–350 °C) typically causes coke deposition and fast deactivation. Recently, we discovered that Co2C nanoprisms with preferentially exposed facets of (020) and (101) can effectively produce olefins from syngas conversion under mild reaction conditions with high selectivity. The methane fraction was limited within 5%, and the product distribution deviated greatly from ASF statistic law. The catalytic performances of Co2C nanoprisms are completely different from that reported for the traditional FT process, exhibiting promising potential industrial application. This Account summarizes our progress in the development of Co2C nanoprisms for Fischer–Tropsch synthesis to olefins (FTO) with remarkable efficiencies and stability. The underlying mechanism for the observed unique catalytic behaviors was extensively explored by combining DFT calculation, kinetic measurements, and various spectroscopic and microscopic investigation. We also emphasize the following issues: particle size effect of Co2C, the promotional effect of alkali and Mn promoters, and the role of metal–support interaction (SMI) in fabricating supported Co2C nanoprisms. Specially, we briefly review the synthetic methods for different Co2C nanostructures. In addition, Co2C can also be applied as a nondissociative adsorption center for higher alcohol synthesis (HAS) via syngas conversion. We also discuss the construction of a Co0/Co2C interfacial catalyst for HAS and demonstrate how to tune the reaction network and strengthen CO nondissociative adsorption ability for efficient production of higher alcohols. We believe that the advances in the development of Co2C nanocatalysts described here present a critic step to produce chemicals through the FTS process.