Cost-Effective Scalable Synthesis of Mesoporous Germanium Particles <i>via</i> a Redox-Transmetalation Reaction for High-Performance Energy Storage Devices

Nanostructured germanium is a promising material for high-performance energy storage devices. However, synthesizing it in a cost-effective and simple manner on a large scale remains a significant challenge. Herein, we report a redox-transmetalation reaction-based route for the large-scale synthesis of mesoporous germanium particles from germanium oxide at temperatures of 420–600 °C. We could confirm that a unique redox-transmetalation reaction occurs between Zn⁰ and Ge⁴⁺ at approximately 420 °C using temperature-dependent <i>in situ</i> X-ray absorption fine structure analysis. This reaction has several advantages, which include (i) the successful synthesis of germanium particles at a low temperature (∼450 °C), (ii) the accommodation of large volume changes, owing to the mesoporous structure of the germanium particles, and (iii) the ability to synthesize the particles in a cost-effective and scalable manner, as inexpensive metal oxides are used as the starting materials. The optimized mesoporous germanium anode exhibits a reversible capacity of ∼1400 mA h g^–1 after 300 cycles at a rate of 0.5 C (corresponding to the capacity retention of 99.5%), as well as stable cycling in a full cell containing a LiCoO₂ cathode with a high energy density (charge capacity = 286.62 mA h cm^–3)

A New Coating Method for Alleviating Surface Degradation of LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Material: Nanoscale Surface Treatment of Primary Particles

Structural degradation of Ni-rich cathode materials (LiNi_<i>x</i>M_1–<i>x</i>O₂; M = Mn, Co, and Al; <i>x</i> > 0.5) during cycling at both high voltage (>4.3 V) and high temperature (>50 °C) led to the continuous generation of microcracks in a secondary particle that consisted of aggregated micrometer-sized primary particles. These microcracks caused deterioration of the electrochemical properties by disconnecting the electrical pathway between the primary particles and creating thermal instability owing to oxygen evolution during phase transformation. Here, we report a new concept to overcome those problems of the Ni-rich cathode material via nanoscale surface treatment of the primary particles. The resultant primary particles’ surfaces had a higher cobalt content and a cation-mixing phase (<i>Fm</i>3̅<i>m</i>) with nanoscale thickness in the LiNi_0.6Co_0.2Mn_0.2O₂ cathode, leading to mitigation of the microcracks by suppressing the structural change from a layered to rock-salt phase. Furthermore, the higher oxidation state of Mn⁴⁺ at the surface minimized the oxygen evolution at high temperatures. This approach resulted in improved structural and thermal stability in the severe cycling-test environment at 60 °C between 3.0 and 4.45 V and at elevated temperatures, showing a rate capability that was comparable to that of the pristine sample

Mesoporous Ge/GeO₂/Carbon Lithium-Ion Battery Anodes with High Capacity and High Reversibility

We report mesoporous composite materials (m-GeO₂, m-GeO₂/C, and m-Ge-GeO₂/C) with large pore size which are synthesized by a simple block copolymer directed self-assembly. m-Ge/GeO₂/C shows greatly enhanced Coulombic efficiency, high reversible capacity (1631 mA h g^–1), and stable cycle life compared with the other mesoporous and bulk GeO₂ electrodes. m-Ge/GeO₂/C exhibits one of the highest areal capacities (1.65 mA h cm^–2) among previously reported Ge- and GeO₂-based anodes. The superior electrochemical performance in m-Ge/GeO₂/C arises from the highly improved kinetics of conversion reaction due to the synergistic effects of the mesoporous structures and the conductive carbon and metallic Ge

Ferromagnetism of Single-Crystalline Cu₂O Induced through Poly(<i>N</i>‑vinyl-2-pyrrolidone) Interaction Triggering d‑Orbital Alteration

Ferromagnetic-like properties of cuprous oxide (Cu₂O) are induced through its interaction with chemisorbed surfactant poly­(<i>N</i>-vinyl-2-pyrrolidone) (PVP), which alters the intrinsic d¹⁰ configuration of Cu ions. Structural and magnetism-related properties of intact Cu₂O crystals (i-Cu₂O) and those capped with PVP (c-Cu₂O) were examined using various analytical instruments. SEM, TEM (corresponding selected area electron diffraction (SAED)), and XRD of i-Cu₂O and c-Cu₂O showed cubic and hexagonal shapes of single crystallinity with facets of {200} and {111}, respectively, resulting from the differential growth rates of the original identical crystals along the facets over time. Bulk magnetic susceptibility (χ) of i-Cu₂O and c-Cu₂O at room temperature in field-dependent magnetization and the difference in their magnetic moment in temperature-dependent magnetization showed diamagnetic and ferromagnetic properties, respectively. The difference in the fluorescence mode of X-ray absorption near edge structure (XANES) spectra between i-Cu₂O and c-Cu₂O, showing no quadruple pre-edge peak for the transition 1s → 3d in Cu­(II) ions with d⁹ electronic configuration, indicates an orbital alteration on the surface of c-Cu₂O caused by an interaction with PVP. Two peaks for c-Cu₂O at higher binding energies in O 1s X-ray photoelectron spectroscopy may be indicative of the ligand-to-metal charge transfer (LMCT) from O atoms of PVP to Cu ions of Cu₂O, generating a chemical interaction through coordination bonding. Large hyperfine splitting constants in electron paramagnetic resonance (EPR) spectra of c-Cu₂O support this interpretation, with septet hyperfine splitting suggestive of Cu–Cu interactions on the surface of c-Cu₂O via the interaction with O atoms of PVP. These results demonstrate that PVP capping of Cu₂O crystal (c-Cu₂O) induces ferromagnetism of Cu­(I) ions through coordination with O atoms of chemically adsorbed PVP. This may induce LMCT and Cu–Cu interactions that lead to changes in electronic configurations, deriving the ferromagnetic moments of c-Cu₂O

Transcriptomics and Comparative Analysis of Three Antarctic Notothenioid Fishes

<div><p>For the past 10 to 13 million years, Antarctic notothenioid fish have undergone extraordinary periods of evolution and have adapted to a cold and highly oxygenated Antarctic marine environment. While these species are considered an attractive model with which to study physiology and evolutionary adaptation, they are poorly characterized at the molecular level, and sequence information is lacking. The transcriptomes of the Antarctic fishes <em>Notothenia coriiceps</em>, <em>Chaenocephalus aceratus</em>, and <em>Pleuragramma antarcticum</em> were obtained by 454 FLX Titanium sequencing of a normalized cDNA library. More than 1,900,000 reads were assembled in a total of 71,539 contigs. Overall, 40% of the contigs were annotated based on similarity to known protein or nucleotide sequences, and more than 50% of the predicted transcripts were validated as full-length or putative full-length cDNAs. These three Antarctic fishes shared 663 genes expressed in the brain and 1,557 genes expressed in the liver. In addition, these cold-adapted fish expressed more Ub-conjugated proteins compared to temperate fish; Ub-conjugated proteins are involved in maintaining proteins in their native state in the cold and thermally stable Antarctic environments. Our transcriptome analysis of Antarctic notothenioid fish provides an archive for future studies in molecular mechanisms of fundamental genetic questions, and can be used in evolution studies comparing other fish.</p> </div

Cobalt Oxide Electrode Doped with Iridium Oxide as Highly Efficient Water Oxidation Electrode

Crystalline cobalt oxide nanoparticles (nc-CoO_<i>x</i>) supported on ITO glass or Ni foam doped with 5 mol % crystalline iridium oxide nanoparticles (nc-IrO_<i>x</i>) showed performances which are higher than those of nc-CoO_<i>x</i> on ITO or Ni foam and nc-IrO_<i>x</i> on a rotating glassy carbon disc electrode or Ni foam. The initial Co^III and Ir^IV become Co^IV and Ir^VI upon applying positive potentials. The nc-CoO_<i>x</i> particles intrinsically carry Co^IIIO₅ centers which become Co^IVO₆ centers upon application of positive potentials. The O vacancy in Co^IIIO₅ is transferred to Ir^VIO₆ upon application of positive potentials, giving rise to the formation of Ir^VIO₅ centers, which are proposed to be the highly active catalytic centers for water oxidation

Comparison of shared and unique genes identified in four notothenioid fishes.

<p>Numbers in parentheses represent the total number of enzymes in metabolic pathway analysis.</p

Functional annotation of proteins encoded in the transcriptomes of the three notothenioid fish based on gene ontology (GO).

<p>Functional annotation of proteins encoded in the transcriptomes of the three notothenioid fish based on gene ontology (GO).</p

Summary of full-length cDNA in the three notothenioids species.

<p>Summary of full-length cDNA in the three notothenioids species.</p

Conservation of three notothenioid fish genes with other species.

<p>Number of notothenioid fish homologous genes annotated in GO analysis.</p