Direct Visualization of Distorted Twin Boundaries in Ce-Doped GdFeO3.

Utilizing advanced transmission electron microscopy (TEM), the structure at the (110)-type twin boundary (TB) of Ce-doped GdFeO3 (C-GFO) has been investigated with picometer precision. Such a TB is promising to generate local ferroelectricity within a paraelectric system, while precise knowledge about its structure is still largely missing. In this work, a direct measurement of the cation off-centering with respect to the neighboring oxygen is enabled by integrated differential phase contrast (iDPC) imaging, and up to 30 pm Gd off-centering is highly localized at the TB. Further electron energy loss spectroscopy (EELS) analysis demonstrates a slight accumulation of oxygen vacancies at the TB, a self-balanced behavior of Ce at the Gd sites, and a mixed occupation of Fe2+ and Fe3+ at the Fe sites. Our results provide an informative picture with atomic details at the TB of C-GFO, which is indispensable to further push the potential of grain boundary engineering.

Electrochemical Proton Intercalation in Vanadium Pentoxide Thin Films and its Electrochromic Behavior in the near-IR Region.

This work examines the proton intercalation in vanadium pentoxide (V2 O5 ) thin films and its optical properties in the near-infrared (near-IR) region. Samples were prepared via direct current magnetron sputter deposition and cyclic voltammetry was used to characterize the insertion and extraction behavior of protons in V2 O5 in a trifluoroacetic acid containing electrolyte. With the same setup chronopotentiometry was done to intercalate a well-defined number of protons in the Hx V2 O5 system in the range of x=0 and x=1. These films were characterized with optical reflectometry in the near-IR region (between 700 and 1700 nm wavelength) and the refractive index n and extinction coefficient k were determined using Cauchy's dispersion model. The results show a clear correlation between proton concentration and n and k.

Single-Ion-Conducting "Polymer-in-Ceramic" Hybrid Electrolyte with an Intertwined NASICON-Type Nanofiber Skeleton.

The fast Li+ transportation of "polymer-in-ceramic" electrolytes is highly dependent on the long-range Li+ migration pathways, which are determined by the structure and chemistry of the electrolytes. Besides, Li dendrite growth may be promoted in the soft polymer region due to the inhomogeneous electric field caused by the commonly low Li+ transference number of the polymer. Herein, a single-ion-conducting polymer electrolyte is infiltrated into intertwined Li1.3Al0.3Ti1.7(PO4)3 (LATP) nanofibers to construct free-standing electrolyte membranes. The composite electrolyte possesses a large electrochemical window exceeding 5 V, a high ionic conductivity of 0.31 mS cm-1 at ambient temperature, and an extraordinary Li+ transference number of 0.94. The hybrid electrolyte in the lithium symmetric cell shows stable Li plating/stripping up to 2000 h under 0.1 mA cm-2 without dendrite formation. The Li|hybrid electrolyte|LiFePO4 battery exhibits enhanced rate capability up to 1 C and a stable cycling performance with an initial discharge capacity of 131.8 mA h g-1 and a retention capacity of 122.7 mA h g-1 after 500 cycles at 0.5 C at ambient temperature. The improved electrochemical performance is attributed to the synergistic effects of the LATP nanofibers and the single-ion-conducting polymer. The fibrous fast ion conductors provide continuous ion transport channels, and the polymer improves the interfacial contact with the electrodes and helps to suppress the Li dendrites.