The influence of compact and ordered carbon coating on solid-state behaviors of silicon during electrochemical processes

To address the issues of large volume change and low conductivity of silicon (Si) materials, carbon coatings have been widely employed as surface protection agent and conductive medium to encapsulate the Si materials, which can improve the electrochemical performance of Si-based electrodes. There has been a strong demand to gain a deeper understanding of the impact of efficient carbon coating over the lithiation and delithiation process of Si materials. Here, we report the first observation of the extended two-phase transformation of carbon-coated Si nanoparticles (Si/C) during electrochemical processes. The Si/C nanoparticles were prepared by sintering Si nanoparticles with polyvinylidene chloride precursor. The Si/C electrode underwent a two-phase transition during the first 20 cycles at 0.2 C, but started to engage in solid solution reaction when the ordered compact carbon coating began to crack. Under higher current density conditions, the electrode was also found to be involved in solid solution reaction, which, however, was due to the overwhelming demand of kinetic property rather than the breaking of the carbon coating. In comparison, the Si/C composites prepared with sucrose possessed more disordered and porous carbon structures, and presented solid solution reaction throughout the entire cycling process

Electron-photon scattering mediated by localized plasmons: A quantitative analysis by eigen-response theory

We show that the scattering interaction between a high energy electron and a photon can be strongly enhanced by different types of localized plasmons in a non-trivial way. The scattering interaction is predicted by an eigen-response theory, numerically verified by finite-difference-time-domain simulation, and experimentally verified by cathodoluminescence spectroscopy. We find that the scattering interaction associated with dark plasmons can be as strong as that of bright plasmons. Such a strong interaction may offer new opportunities to improve single-plasmon detection and high-resolution characterization techniques for high quality plasmonic materials.Comment: 4 pages, 4 figures (excluding Supporting Information

B→KB\to K Transition Form Factor with Tensor Current within the kTk_T Factorization Approach

In the paper, we apply the $k_T$ factorization approach to deal with the $B\to K$ transition form factor with tensor current in the large recoil regions. Main uncertainties for the estimation are discussed and we obtain $F_T^{B\to K}(0)=0.25\pm0.01\pm0.02$, where the first error is caused by the uncertainties from the pionic wave functions and the second is from that of the B-meson wave functions. This result is consistent with the light-cone sum rule results obtained in the literature.Comment: 8 pages, 4 figures, references adde