Stringed “tube on cube” hybrid architecture is developed for high-energy-density lithium–sulfur batteries with high sulfur loading and lean electrolyte.

Developing highly active as well as durable oxygen reduction reaction (ORR) electrocatalysts are still imperative for clean and efficient energy conversion device, such as fuel cells and metal-air battery. For this purpose and maximize the utilization of noble Pt, we present here a facile, yet scalable strategy for the high-precise synthesis of 1-nm-thick Pt3Ni bimetallic alloy nanowires (Pt3Ni BANWs). The seed-mediated growth mechanism of Pt3Ni BANWs was identified subsequently. As expected, the Pt3Ni BANWs delivered enhanced mass activity (0.546 A mgPt –1, exceeding the 2020 target of DOE) in comparison to Pt nanowires assembly (Pt NWA, 0.098 A mgPt –1) and Pt/C (Pt, 0.135 A mgPt –1), because of the rational integration of multiple compositional and structural advantages. Moreover, the Pt3Ni BANWs displayed enhanced durability (37% MA retention) than Pt NWA and Pt after 50 000 potential cycles. All these results indicate that the ultrathin Pt3Ni BANWs are potential candidates for catalyzing ORR with acceptable activity and durability. The present work could not only provide a facile strategy but also a general guidance for the design of superb performance Pt-based nanowire catalysts for ORR.

No abstract

The formation of hollow-structured oxide nanoparticles is primarily governed by the Kirkendall effect. However, the degree of complexity of the oxidation process multiplies in the bimetallic system because of the incorporation of more than one element. Spatially dependent oxidation kinetics controls the final morphology of the hollow nanoparticles, and the process is highly dependent on the elemental composition. Currently, a theoretical framework that can predict how different metal elements result in different oxide morphologies remains elusive. In this work, utilizing a combination of state-of-the-art in situ environmental transmission electron microscopy and three-dimensional (3D) chemically sensitive electron tomography, we provide an in situ and 3D investigation of the oxidation mechanism of the Ni-Fe nanoparticles. The direct measurements allow us to correlate the 3D elemental segregation in the particles with the oxidation morphologies, that is, single-cavity or dual-cavity hollow structure, and multicavity porous structures. Our findings in conjunction with theoretical calculations show that metal concentration, diffusivity, and particle size are important parameters that dictate the mechanical and phase stabilities of the hollow oxide shell, which in turn determine its barrier properties and the final hollow oxide morphology. It sheds light on how to use multielemental oxidation to control morphology in nanomaterials and demonstrates the power of 3D chemical imaging.

Lithium metal anodes hold great potential for next‐generation high‐energy batteries. However, the low Coulombic efficiency (CE) and dendritic growth during lithium metal plating/stripping cause short cycle life and deter its practical application. Herein, nitrogen, oxygen‐codoped vertical carbon nanosheet arrays are constructed on Cu foil (NOCA@Cu) as the efficient host to improve CE and suppress Li dendrites through polymer interfacial self‐assembly and morphology‐preserved pyrolysis. Benefitting from numerous vertical porous channels with abundant lithiophilic heteroatom dopants, 3D structured NOCA@Cu host can guide Li nucleation and growth in a controlled manner, leading to dendrite‐free Li deposition with high CE and long life cycles in both carbonate electrolyte and ether electrolyte, surpassing horizontal carbon‐coated Cu and pure Cu hosts. Finite element simulation further reveals the structural function of vertical carbon arrays as not only directing Li plating in the nanoarray‐constructed confined space but also homogenizing the distribution of ion concentration and electrical field throughout the 3D electrode. To demonstrate the practical application of lithiated NOCA@Cu anode, it is coupled with a commercial LiFePO4 cathode, delivering high capacity and long‐cycle stability with nearly 100% CE. The cost‐effective, scalable, and efficient features render NOCA@Cu a promising Li host toward practical lithium metal batteries.