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Edges of carbon materials have been known to work as active sites for various applications such as catalysts, adsorbent, and electrodes, but selecting precursors for carbon materials with controlled edges in the absence of metallic substrate is challenging. This work developed a method to select the superior precursors instantaneously using molecular dynamic simulation. This simulation predicted that hydrogen in precursors gasified and the hydrogen attacked the active sites in precursors upon carbonization, causing the decrement of active sites. Thus, it is essential to reduce the concentration of hydrogen in precursors and it is also necessary to introduce reactive functional groups near the active site to protect the active sites. We indeed synthesized the selected precursors such as diethynyl anthracene, diethynyl chrysene, divinyl naphthyridine, and divinyl phenanthroline and proved that edges in those precursors were maintained even after carbonization at 773 K using diffuse reflectance infrared Fourier transform and X-ray photoelectron spectroscopy with the aid of spectra simulated by density functional theory calculation. Especially, ca. 100% of edge structures of zigzag edges and armchair edges in diethynyl anthracene and diethynyl chrysene was maintained even after carbonization at 773 K.

Cu-doped Li2O, synthesized by mechanochemical reactions between Li2O and CuO, is demonstrated as a cathode material for lithium-ion batteries. The X-ray diffraction and absorption analyses suggest that in the Cu-doped Li2O, Cu2+ ions are located at 48g sites less symmetrical than 8c sites for Li+ ions, distorting the arrangement of surrounding O2− ions slightly from tetrahedral to square-planar, while the Cu2+ ions are doped in an antifluorite-type Li2O. The Cu-doped Li2O cathode has a charge capacity of 360 mAh g−1 without an irreversible O2 gas evolution reaction and exhibits a reversible capacity of 300 mAh g−1. Cu K-edge XANES spectroscopy and quantitative analysis of peroxide species reveal that redox of copper ions, formation/neutralization of O 2p electron holes, and generation/annihilation of peroxide species take place during charge/discharge.

Fe-doped Li2O (FDL) is synthesized mechanochemically and is demonstrated as a new Co-free cathode material for use in sealed Li2O2 batteries, which have been proposed as high energy density batteries. Fe3+ ions are substitutionally doped into the Li sites in an antifluorite-type Li2O structure to create FDL. The FDL consists of (Li0.82Fe0.06)2O (d-FDL) and high-temperature form of Li5FeO4 (o-FDL), in which Fe3+ ions disorderly and orderly arranged, respectively. According to the Mossbauer spectra and quantitative peroxide species analysis, the FDL cathode operates principally based on the redox reaction between O22− and O2−. X-ray diffraction study reveals that the reversible formation of O22− proceeds mainly in the d-FDL. An irreversible side reaction involving the evolution of oxygen gas occurs when the cathode is charged to more than 250 mAh g−1. The FDL (Fe/(Li + Fe) = 10 at%) cathode exhibits a reversible capacity of 200 mAh g−1 over 200 cycles at a current density of 22.5 mA g−1.

Increased strength of Al matrix composites (AMCs) with a high electrical conductivity are in demand to replace copper conductors. In this study, a high-performance Al4C3/Al composite was synthesized in situ via the high-energy densification of uniform graphene oxide (GO)/Al powder combination; GO was completely transformed to monocrystalline Al4C3 nanorod structures, robustly bridging across the Al grain boundary. The formation mechanism of interfacial Al4C3 was illustrated by high-resolution transmission electron microscope observations. The Al4C3 nanorods were homogeneously dispersed and possessed an intimate and faceted interface with the matrix, resulting in the enhanced tensile strength of Al. Moreover, the Al4C3/Al composite retained the required electrical conductivity similar to that of pure Al, in addition to the stable interface at elevated temperatures and long-term service reliability in moist environment. The findings of this study will be significant in providing the basis of designing novel heat-resistant AMCs in electrical applications.

We recently proposed a new battery system based on the redox of lithium peroxide (Li 2 O 2 )/lithium oxide (Li 2 O) at the cathode (lithium-peroxide battery system). In this system, the use of Li 2 O with cobalt ions partially substituted for lithium ions (Co-doped Li 2 O) is key to its realization. In this study, to further improve the cell performance, we prepare various Co-doped Li 2 O samples by a mechanochemical process using different cobalt source materials (e.g., LiCoO 2 , Co 3 O 4 , and CoO) and comparatively investigate them. Amongst the investigated cathode materials, the Co-doped Li 2 O sample prepared using LiCoO 2 with a Co/(Co + Li) ratio of 0.09 exhibits the best performance. Monitoring of the pressure in the cell reveals that this Co-doped Li 2 O cathode can be charged to 270 mAh g −1 without O 2 evolution involving its decomposition. Charge and discharge at 270 mAh g −1 is repeated more than 50 times. In addition, the rate-capability tests reveals that the redox reaction between peroxide and oxide ions is fast and that the cathode can be discharged at a high current density of 1000 mA g −1 .

Soft X-ray absorption spectroscopic studies are carried out to clarify the charge/discharge reaction mechanism of Co-doped Li 2 O (CDL, Co/Li = 0.1 molar ratio) as a cathode material for a new rechargeable lithium-peroxide battery. Upon charging CDL in an aprotic electrolyte, a drastic change can be seen in the O K-edge spectra, with a new, strong peak assignable to σ*(O–O) of peroxide at photon energy of 531.0 eV. This peak is reduced during subsequent discharging, causing the spectrum to essentially return to that of pristine CDL recorded in total fluorescence yield mode. The Co L 2,3 -edge spectra do not show a remarkable change during charging, with the exception of the disappearance of a Co 2+ shoulder peak. The spectrum of charged CDL is in reasonable agreement with the calculated spectrum, assuming that the fraction of Co 3+ – L (where L indicates a hole state in the oxygen 2 p band) is dominant in the electronic configuration of the ground state. This suggests that, to a certain extent, a redox reaction involving a ligand hole state (Co 3+ – L ) participates in generation of the capacity.