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Despite the extremely high energy density of the lithium metal, dendritic lithium growth caused by nonuniform lithium deposition can result in low Coulombic efficiency and safety hazards, thereby inhibiting its practical applications. Here, we report a new strategy for adopting a nanopatterned gold (Au) seed on a copper current collector for uniform lithium deposition. We find that Au nanopatterns enhance lithium metal battery performance, which is strongly affected by the feature dimensions of Au nanopatterns (diameter and height). Ex situscanning electron microscopy images confirm that this can be attributed to the perfectly selective lithium nucleation and uniform growth resulting from the spatial confinement effect. The spatial arrangement of Au dot seeds homogenizes the Li+flux and electric field, and the size-controlled Au seeds prevent both seed-/substrate-induced agglomeration and interseed-induced lithium growth, leading to uniform lithium deposition. This dendrite-free lithium deposition results in the improvement of electrochemical performance, and the system showed cyclic stability over 300 cycles at 0.5 mA cm–2and 200 cycles at 1.0 mA cm–2(1 mA h cm–2) and a high rate capability. This study provides in-depth insights into the more complicated and diverse seed geometry control of seed materials for the development of high-performance lithium metal batteries.

The development of highly efficient catalysts in the cathodes of rechargeable Li–O2batteries is a considerable challenge. Polyelemental catalysts consisting of two or more kinds of hybridized catalysts are particularly interesting because the combination of the electrochemical properties of each catalyst component can significantly facilitate oxygen evolution and oxygen reduction reactions. Despite the recent advances that have been made in this field, the number of elements in the catalysts has been largely limited to two metals. In this study, we demonstrate the electrochemical behavior of Li–O2batteries containing a wide range of catalytic element combinations. Fourteen different combinations with single, binary, ternary, and quaternary combinations of Pt, Pd, Au, and Ru were prepared on carbon nanofibers (CNFs) via a joule heating route. Importantly, the Li–O2battery performance could be significantly improved when using a polyelemental catalyst with four elements. The cathode containing quaternary nanoparticles (Pt–Pd–Au–Ru) exhibited a reduced overpotential (0.45 V) and a high discharge capacity based on total cathode weight at 9130 mAh g–1, which was ∼3 times higher than that of the pristine CNF electrode. This superior electrochemical performance is be attributed to an increased catalytic activity associated with an enhanced O2adsorbability by the quaternary nanoparticles.

Excessive overpotential during charging is a major hurdle in lithium–oxygen (Li–O2) battery technology. NO2–/NO2redox mediation is an efficient way to substantially reduce the overpotential and to enhance oxygen efficiency and cycle life by suppressing parasitic reactions. Considering that nitrogen dioxide (NO2) is a gas, it is quite surprising that NO2–/NO2redox reactions can be sustained for a long cycle life in Li–O2batteries with such an open structure. A detailed study with in situ differential electrochemical mass spectrometry (DEMS) elucidated that NO2could follow three reaction pathways during charging: (1) oxidation of Li2O2to evolve oxygen, (2) vaporization, and (3) conversion into NO3–. Among the pathways, Li2O2oxidation occurs exclusively in the presence of Li2O2, which suggests that NO2has high reactivity to Li2O2. At the end of the charging process, most of the volatile oxidized couple (NO2) is stored by conversion to a stable third species (NO3–), which is then reused for producing the reduced couple (NO2–) in the next cycle. The dominant reaction of Li2O2oxidation involves the temporary storage of NO2as a stable third species during charging, which is an innovative way for preserving the volatile redox couple, resulting in a sustainable redox mediation for a high-performance Li–O2battery.

The development of effective synthetic routes is important to manifest proper nature of specific materials. In-situelectrochemical functionalization possesses great advantages over conventional routes, especially facile way and leading to reaching elaborate sites of functional group. Here, we demonstrate the preparation of functionalized carbons by in-situelectrochemical reduction in an argon atmosphere for application in low-cost, environmentally benign, and high-performance oxygen-electrodes for non-aqueous Li–O2batteries. A Li–O2battery with functionalized carbon shows a high discharge capacity (100 times that of pristine carbon), high power and cycling stability. The outstanding performance is attributed to the high O2affinity of the functionalized carbon surface that facilitates the formation of soluble and diffusible superoxide intermediates by the reduction of the remaining O2competing with surface growth for Li2O2formation.

The rechargeable Li–CO2battery has attracted considerable attention in recent years because of its carbon dioxide (CO2) utilization and because it represents a practical Li–air battery. As with other battery systems such as the Li-ion, Li–O2, and Li–S battery systems, understanding the reaction pathway is the first step to achieving high battery performance because the performance is strongly affected by reaction intermediates. Despite intensive efforts in this area, the effect of material parameters (e.g., the electrolyte, the cathode, and the catalyst) on the reaction pathway in Li–CO2batteries is not yet fully understood. Here, we show for the first time that the discharge reaction pathway of a Li–CO2battery composed of graphene nanoplatelets/beta phase of molybdenum carbide (GNPs/β-Mo2C) is strongly influenced by the dielectric constant of its electrolyte. Calculations using the continuum solvents model show that the energy of adsorption of oxalate (C2O42–) onto Mo2C under the low-dielectric electrolyte tetraethylene glycol dimethyl ether is lower than that under the high-dielectric electrolyte N,N-dimethylacetamide (DMA), indicating that the electrolyte plays a critical role in determining the reaction pathway. The experimental results show that under the high-dielectric DMA electrolyte, the formation of lithium carbonate (Li2CO3) as a discharge product is favorable because of the instability of the oxalate species, confirming that the dielectric properties of the electrolyte play an important role in the formation of the discharge product. The resulting Li–CO2battery exhibits improved battery performance, including a reduced overpotential and a remarkable discharge capacity as high as 14,000 mA h g–1because of its lower internal resistance. We believe that this work provides insights for the design of Li–CO2batteries with enhanced performance for practical Li–air battery applications.

Graphene-based carbon nanostructures with nanometer dimensions have been of great interest due to the existence of a bandgap. So far, well-ordered edge structure and uniformly synthesized graphene quantum dots (GQDs) with a hexagonal single-crystalline structure have not been directly observed owing to the limited precision of current synthesis approaches. Herein, we report on a novel approach not just for the synthesis of the size-controlled single-crystalline GQDs with hexagonal shape but also for a new discovery on constructing 2D and 3D graphene single crystal structures from d-glucose via catalytic solution chemistry. With size-controlled single-crystalline GQDs, we elucidated the crucial role of edge states on luminescence from the correlation between their crystalline size and exciton lifetime. Furthermore, blue-emissive single-crystalline GQDs were used as an emitter on light-emitting diodes and exhibit stable deep-blue emission regardless of the voltage and doping level.

Tetrahexahedral (THH) gold nanocrystals bound to 24 high-index facets were synthesized through a facile colloidal chemistry by reducing HAuCl4in the mixture solution of N,N-dimethylformamide and poly(vinylpyrrolidone) at 80 °C. As-synthesized THH gold nanocrystals with Ohsymmetry were single-crystals, mainly bound to 24 high-index {210} facets. The controlled slow reaction condition made the rhombic dodecahedral gold nanocrystals transform to THH gold nanocrystals with high-index facets.

Aqueous electrolytes with wide electrochemical stability windows are crucial for developing high-energy and safe lithium-ion batteries, and molecular crowding electrolytes, which use polyethylene glycol as a molecular crowding agent to inhibit water decomposition by forming strong hydrogen bonds, are promising candidates. However, the polymer increases the viscosity of the electrolyte and decreases the ionic conductivity. In addition, the electrode–electrolyte interfacial layer is ineffective to protect the electrodes from water decomposition at a low salt concentration. Here, a molecular crowding electrolyte is prepared by dissolving lithium bis(trifluoromethanesulfonyl)imide in a mixture of a small-molecular crowding agent (tetraethylene glycol) and H2O. Succinonitrile (SN) is introduced to widen the electrochemical stability window of the aqueous electrolyte up to 4.3 V and improve the ionic conductivity. SN also promotes the formation of a stable and uniform electrode/electrolyte interfacial layer on LiNi0.8Mn0.1Co0.1O2(NMC811), which can then be used as a cathode material. The fabricated NMC811/Li4Ti5O12full cell delivers a maximum energy density of 148 W h/kg, a Coulombic efficiency of 99.2%, and retains 72% of its initial capacity after 150 cycles at 0.2C with a positive/negative capacity ratio of 1.11. This paper introduces a viable strategy for developing high-energy-density aqueous batteries.

A star in the making: Gold nano‐hexapods with controlled arm lengths were synthesized by selective growth on the vertices of octahedral Au seeds. Depending on the arm length, their surface plasmon resonance peaks shifted from the visible to the near‐infrared region (see picture), which could be readily controlled by varying the amount of HAuCl4, the reaction temperature, or both.

Ein Stern wird geboren: Gold‐Hexapoden mit kontrollierten Armlängen wurden durch selektives Wachstum an den Ecken oktaedrischer Au‐Keime gebildet. Abhängig von der Armlänge, die über die HAuCl4‐Menge und die Reaktionstemperatur eingestellt werden kann, verschiebt sich die Oberflächenplasmonenresonanz der Nanohexapoden vom sichtbaren in den nahinfraroten Bereich (siehe Bild).

Golden solar cells: Several positive effects arise from the addition of truncated octahedral Au nanoparticles (ca. 70 nm diameter) to bulk heterojunction (BHJ) photovoltaic cells fabricated from a variety of donor polymers and PC70BM as acceptor (see picture). At the optimized blend ratio of Au nanoparticles (5 wt %) in the active layer, the power conversion efficiency increased for all polymer/PC70BM systems under study.

Goldene Solarzellen: Mehrere positive Effekte resultieren, wenn man Heterokontaktsolarzellen verschiedener Donorpolymere mit PC70BM‐Akzeptor gekappte oktaedrische Au‐Nanopartikel (70 nm) zusetzt (siehe Bild). Beim optimalen Gehalt der Au‐Nanopartikel (5 Gew.‐%) in der aktiven Schicht waren bei allen untersuchten Polymer/PC70BM‐Systemen die Wirkungsgrade erhöht.

We report a facile method for the synthesis of uniform Au octahedra with well‐controlled sizes and optical properties by seed‐mediated growth. Starting from single‐crystal seeds of Au spheres with a uniform size, we could reproducibly obtain Au octahedra with a narrow size distribution (<7 % in standard deviation) and in high purity (>90 %). Moreover, the edge lengths of these Au octahedra could be readily tuned in a controllable fashion from 16 to 77 nm by varying the amount of seeds, the concentration of HAuCl4, or both. We have also investigated the effects of water and poly(vinyl pyrrolidone) (PVP) in the system, as well as the reaction temperature, on the evolution of octahedral shape.

Many facets: A simple synthetic route, which is based on reduction in aqueous solution, results in Pt concave nanocubes (see picture) enclosed by high‐index facets such as {510}, {720}, and {830}. The nanocrystals exhibit electrocatalytic activity (per unit surface area) that is 3.5 times higher than the commercial Pt/C catalyst in the oxygen reduction reaction.

Form und Funktion: Eine einfache Synthese führt über eine Reduktion in wässriger Lösung zu konkaven Pt‐Nanowürfeln (siehe Bild) mit hochindizierten Flächen wie {510}, {720} und {830}. Die elektrokatalytische Aktivität der Nanokristalle (bezogen auf die Oberfläche) in der Sauerstoffreduktion ist 3.5‐mal höher als die eines Pt/C‐Katalysators.

Despite much research focused on lithium (Li) metal batteries, an important issue concerning Li-dendrite growth on the anode remains unresolved. The intrinsic mechanism of this Li-dendrite formation is related to the non-uniform distribution of Li-ion flux on the anode in charge/discharge caused by irregular structure and energy of anode surface. Here we report upon dendrite-free Li-deposition in a carbonate-based electrolyte using a novel Cu anode structure with sharp wrinkles and a [100] crystal facet. This uniform Li-deposition resulted in long-term electrochemical cyclability in Li/Cu and LiFePO4/Li cell. Our observations revealed that the wrinkled Cu surface and the unifying [100] crystal facet play important roles in enhancing the uniformity of the Li-ion flux and the adsorption energy of the Li-ions on Cu, respectively. We expect that this study will permit the use of a wide range of wrinkled structures and crystal planes to obtain high-energy and long-term cycles of Li-metal batteries.

Solid-state lithium batteries have been intensively studied as part of research activities to develop energy storage systems with high safety and stability characteristics. Despite the advantages of solid-state lithium batteries, their application is currently limited by poor reversible capacity arising from their high resistance. In this study, we significantly improve the reversible capacity of solid-state lithium batteries by lowering the resistance through the introduction of a graphene and wrinkle structure on the surface of the copper (Cu) current collector. This is achieved through a process of chemical vapor deposition (CVD) facilitating graphene-growth synthesis. The modified graphene/wrinkled Cu current collector exhibits a periodic wrinkled pattern 420 nm in width and 22 nm in depth, and we apply it to a graphite composite electrode to obtain an improved areal loading average value of ∼2.5 mg cm–2. The surface-modified Cu current collector is associated with a significant increase in discharge capacity of 347 mAh g–1at 0.2 C when used with a solid polymer electrolyte. Peel test results show that the observed enhancement is due to the improved strength of adhesion occurring between the graphite composite anode and the Cu current collector, which is attributed to mechanical interlocking. The surface-modified Cu current collector structure effectively reduces resistance by improving adhesion, which subsequently improves the performance of the solid-state lithium batteries. Our study can provide perspective and emphasize the importance of electrode design in achieving enhancements in battery performance.

Controlling the pore structure of cathodes has a decisive effect on the performance of lithium (Li)-O2batteries. In this work, macroporous carbon nanofiber (MCNF) decorated with Pt nanoparticles (PtNPs) (PtNP-MCNF) are successfully fabricated. Their electrochemical performance as cathodes for a Li-O2battery is evaluated. The MCNF mats are fabricated through an electrospinning and templating method using cross-linked polystyrene particles. PtNPs are grown on the surface of the MCNF through a solvothermal reaction. As-prepared PtNP-MCNF has interconnected macropores along the MCNF interior and abundant surface openings. These macropores are also connected to larger pores between individual MCNFs through the orifices on the MCNF surface, rendering a hierarchical porous structure. Owing to the highly porous structure and catalytic activity of PtNPs, Li-O2cells using PtNP-MCNF cathodes exhibit considerably improved performance. In particular, with regard to cycle stability, the Li-O2cell using PtNP-MCNF attains over 470 cycles in total while discharging at a capacity of 1000 mAh gc−1with a current density of 500 mA gc−1. Such a high performance of the Li-O2cell can be attributed to a facilitated Li+and O2transportation through the highly porous structure, and highly reversible Li-O2operation over its life-cycle by means of catalytic activity of PtNPs.

The addition ofan optimized amount (5 wt %) of truncated octahedral nanoparticles with 70 nm diameter leads to an increase in power conversion efficiency in bulk heterojunction photovoltaic cells. In their Communication on page 5519 ff.,J. H. Park, O O. Park, A. J. Heeger, et al. describe the fabrication of such solar cells from a variety of donor polymers and PC70BM as acceptor.

Die Zugabe einer optimierten Menge(5 Gew.‐%) gekappt‐oktaedrischer Goldnanopartikel mit 70 nm Durchmesser führt zu einer Erhöhung der Wirkungsgrade von Heterokontaktsolarzellen. In ihrer Zuschrift auf S. 5633 ff.beschreiben J. H. Park, O. O. Park, A. J. Heeger et al. die Herstellung solcher Solarzellen anhand verschiedener Donorpolymere und PC70BM als Akzeptor.