Antimony-Coated Carbon Nanocomposites as High-Performance Anode Materials for High-Temperature Sodium–Metal Batteries

Metallic sodium (Na) possesses several advantageous characteristics, including a high theoretical specific capacity, low electrode potential, and availability in abundance, making it an ideal anode material for sodium–metal batteries (SMBs). However, the practical use of Na metal anodes is severely impeded due to the uncontrolled formation of dendrites due to the slow electrochemical kinetics and chemical instability of the formed solid-electrolyte interphase (SEI) layer. This situation can worsen considerably under high-temperature (HT) conditions (>55 °C). To overcome this issue, we have fabricated a thermally stable antimony (Sb)-coated carbon (Sb@C) nanocomposite as a sodium host material, where Sb nanoparticles are encapsulated within the carbon layers. This unique nanostructure controls vaporization during the plating-stripping process and dendrite formation and provides acceptor sites for Na+ ions. The Sb@C electrode exhibits an extended life span of symmetrical cycles (2400 h at 1 mA cm–2) due to the abundant nucleation sites. It maintains a low nucleation overpotential (∼15 mV), enhancing its performance and long cycle stability. Moreover, the in situ formed Na–Sb synergistically offers durable ionic/electronic diffusion paths and chemically interacts with Na, forming abundant Na nucleation sites. Therefore, in this study, we emphasize the importance of the rational design of highly stable alloys and present an effective strategy for achieving high-performance sodium–metal anodes

Materials Engineering of High-Performance Anodes as Layered Composites with Self-Assembled Conductive Networks

The practical implementation of nanomaterials in high capacity batteries has been hindered by the large mechanical stresses during ion insertion/extraction processes that lead to the loss of physical integrity of the active layers. The challenge of combining the high ion storage capacity with resilience to deformations and efficient charge transport is common for nearly all battery technologies. Layer-by-layer (LBL/LbL) engineered nanocomposites are able to mitigate structural design challenges for materials requiring the combination of contrarian properties. Herein, we show that materials engineering capabilities of LBL augmented by self-organization of nanoparticles (NPs) can be exploited for constructing multiscale composites for high capacity lithium ion anodes that mitigate the contrarian nature of three central parameters most relevant for advanced batteries: large intercalation capacity, high conductance, and robust mechanics. The LBL multilayers were made from three function-determining components, namely polyurethane (PU), copper nanoscale particles, and silicon mesoscale particles responsible for the high nanoscale toughness, efficient electron transport, and high lithium storage capacity, respectively. The nanocomposite anodes optimized in respect to the layer sequence and composition exhibited capacities as high as 1284 and 687 mAh/g at the first and 300th cycle, respectively, with a fading rate of 0.15% per cycle. Average Coulombic efficiencies were as high as 99.099.4% for 300 cycles at 1.0 C rate (4000 mA/g). Self-organization of copper NPs into three-dimensional (3D) networks with lattice-to-lattice connectivity taking place during LBL assembly enabled high electron transport efficiency responsible for high battery performance of these Si-based anodes. This study paves the way to finding a method for resolution of the general property conflict for materials utilized in for energy technologies

Synergistic Resonances and Charge Transfer in Double-Shelled ZnO Hollow Microspheres for High-Performance Semiconductor-Based SERS Substrates

The main contribution of semiconductor nanomaterials to surface-enhanced Raman scattering (SERS) comes from charge transfer (CT) between the absorbing molecules and the semiconductor. However, it is still challenging to realize the combined effects of the electromagnetic mechanism (EM) and the chemical mechanism (CM) for semiconductor-based SERS substrates. Herein, we demonstrate and design double-shelled ZnO (ZnO-DS) hollow microspheres by a modified hydrothermal/solvothermal process. SERS experiments and theoretical simulations proved that the excellent SERS activity is mainly attributed to the combined effect of Mie resonances generated by the nanocavities in the unique hollow double-shell nanoparticles and the CT effect excited by special structure ZnO. Particularly, the produced ZnO-DS SERS substrates exhibited a low limit of detection (LOD, 1 × 10–7 M for 4-MPY), outstanding sensitivity (EF = 1.2 × 104), and high stability (RSD = 10.4%, over 30 days of storage at room temperature). Furthermore, benefiting from the matching of energy levels of the ZnO-DS substrate and probe molecules, the sulfhydryl molecules with similar structures could be selectively distinguished in complex environments. We visualize that this work will resolve the current dilemma between sensitivity and selective detection of SERS substrates and expect to enable the monitoring of target molecules in the environment containing complex mixtures such as food safety and environmental protection