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Colloidal semiconductor nanocrystals have attracted widespread attention due to their tremendous electrical and optical properties. Nanoparticles exhibit a strong tendency to aggregate and sinter in a short period of time during processing or use due to their large surface area-to-volume ratio, which may lead to significant changes in their required performance. Therefore, it is of great significance to conduct in-depth research on the sintering process and mechanism of nanoparticles to maintain their stability. Here, the sintering process of CdSe/CdS core/shell nanocrystals under continuous electron beam irradiation was studied using in situ transmission electron microscopy (TEM). In the early stages of sintering, CdSe/CdS nanocrystals approached each other at a distance of approximately 1–2 nm. As the exposure time to the electron beam increased, the movement of surface atoms on the nanocrystals led to contact between them. Subsequently, the atoms on the contact surfaces underwent rapid motion, resulting in the rapid formation of the neck between the particles. The neck formation between adjacent particles provides strong evidence of a sintering mechanism dominated by surface atom diffusion rather than Ostwald ripening. Further research in this area could lead to the development of improved methods to prevent sintering and enhance the stability of nanocrystals, ultimately contributing to the advancement of nanomaterial-based devices and materials with long-lasting performance. [ABSTRACT FROM AUTHOR]

Local thickening, resulting from displacive or diffusive mechanisms individually, is frequently observed in nanoscale metals during compression. However, it is not fully understood how a coupled displacive-diffusive mechanism would mediate the compressive deformation of metallic nanocrystal. Here, by conducting in situ atomic-scale compression tests, we find that, instead of local thickening commonly reported thus far, abnormal thinning events consecutively occur in silver nanocrystals, where preexisting dislocations and crystal slip serve as stimuli to activate surface atom diffusion. Below a critical width, tensile-fracture-like failure occurs in the silver nanocrystals. This work sheds light on atomic-scale diffusion-mediated compressive deformation of metallic nanocrystal.

Local thickening, resulting from displacive or diffusive mechanisms individually, is frequently observed in nanoscale metals during compression. However, it is not fully understood how a coupled displacive-diffusive mechanism would mediate the compressive deformation of metallic nanocrystal. Here, by conducting in situ atomic-scale compression tests, we find that, instead of local thickening commonly reported thus far, abnormal thinning events consecutively occur in silver nanocrystals, where preexisting dislocations and crystal slip serve as stimuli to activate surface atom diffusion. Below a critical width, tensile-fracture-like failure occurs in the silver nanocrystals. This work sheds light on atomic-scale diffusion-mediated compressive deformation of metallic nanocrystal. In situ atomic-scale compression tests reveal that surface atom diffusion mediates consecutive thinning events and ultimate compression fracture in silver nanocrystals. [ABSTRACT FROM AUTHOR]

Lithium metal anode possesses overwhelming capacity and low potential but suffers from dendrite growth and pulverization, causing short lifespan and low utilization. Here, a fundamental novel insight of using single-atomic catalyst (SAC) activators to boost lithium atom diffusion is proposed to realize delocalized deposition. By combining electronic microscopies, time-of-flight secondary ion mass spectrometry, theoretical simulations, and electrochemical analyses, we have unambiguously depicted that the SACs serve as kinetic activators in propelling the surface spreading and lateral redistribution of the lithium atoms for achieving dendrite-free plating morphology. Under the impressive capacity of 20 mA h cm -2 , the Li modified with SAC-activator exhibits a low overpotential of ∼50 mV at 5 mA cm -2 , a long lifespan of 900 h, and high Coulombic efficiencies during 150 cycles, much better than most literature reports. The so-coupled lithium-sulfur full battery delivers high cycling and rate performances, showing great promise toward the next-generation lithium metal batteries.

It is imperative to explore practical methods and materials to drive the development of high energy density lithium metal batteries. The constuciton of nanostructure electrodes and surface engineering on the current collectors are the two most effective strategies to regulate the homogeneous Li plating/stripping to relieve the Li dendrites and infinite volume change problems. Based on the low stacking fault energy of the Cu-Zn alloy, we present a novel chemical energy release induced surface atom diffusion strategy, which is achieved by the negative Gibbs free energy from the surface oxidation reaction and subsequent replacement reaction under thermal treatment in air, to realize a uniform upper ZnO nanoparticles coating. Furthermore, we apply the modified brass mesh as a lithiophilic current collector to decrease the Li deposition nucleation overpotential and effectively restrain the Li dendrite growth. The modified brass current collector achieves a long-term cycling stability of 500 cycles at 2.0 mA cm -2 . We have verified the effectiveness of our chemical energy release modification strategy on a 1 m 2 brass mesh and other Cu alloy (Tin bronze mesh), which demonstrates its great opportunities for scalable and safe lithium metal batteries.