Time Release of Encapsulated Additives for Enhanced Performance of Lithium-Ion Batteries

Time release of encapsulated vinylene carbonate (VC) from microcapsules in Li-ion batteries is demonstrated to enhance the rate performance without sacrificing capacity retention. VC-filled microcapsules are successfully prepared by the solvent exchange method that allows VC to diffuse through the microcapsule shell wall at an elevated temperature. The concentration of VC added directly to the electrolyte in a pouch cell (2 wt %) significantly decreases after the first cycle at C/10-rate. In pouch cells that contain 5 wt % VC-filled microcapsules, the concentration of VC increases from 0 to 3 wt % over the first cycle because of the diffusion of microencapsulated VC in the electrolyte. Electrochemical impedance spectroscopy, rate capability, and long-term cycling tests are conducted for pouch cells with VC additives (0, 2, and 5 wt %) and VC microcapsules (5 wt %). Pouch cells with both 5 wt % VC additive and microencapsulated VC show improved capacity retention over 400 cycles at 1 C-rate compared to the cells without VC additive. When VC is added directly, the high initial concentration leads to increased interfacial resistance and decreased rate capability. By contrast, time release of microencapsulated VC by diffusion through microcapsules increases the discharge capacity 2.5 times at 5 C-rate compared to the direct VC addition to the electrolyte

Reconstructed images and profiles obtained using 200 MeV proton beam.

<p>These images were reconstructed by three different techniques. The RSP profiles were obtained using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156226#pone.0156226.e003" target="_blank">Eq 3</a> to compare with the ideal RSP profile for 200 MeV protons.</p

CNR results.

<p>CNR results.</p

Number of protons incident on 50^th detector.

<p>Number of protons incident on 50^th detector.</p

Flexible, Low-Power Thin-Film Transistors Made of Vapor-Phase Synthesized High‑<i>k</i>, Ultrathin Polymer Gate Dielectrics

A series of high-<i>k</i>, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di­(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (<i>k</i>) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10^–8 A/cm² in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-<i>k</i> dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-<i>k</i> organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics

Non-scattered proton counts versus detector thickness.

<p>This graph shows the non-scattered proton counts for various detector thicknesses.</p

Reconstructed images and profiles obtained using 250 MeV proton beam.

<p>These images were reconstructed by three different techniques. The RSP profiles were obtained using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156226#pone.0156226.e003" target="_blank">Eq 3</a> to compare with the ideal RSP profile for 250 MeV protons.</p

View of phantom.

<p>The phantom is composed of bone, adipose, and an air region in a cylinder filled with water.</p

Distributions of 200 MeV (left) and 250 MeV (right) protons for different detector thickness.

<p>These graphs depict the beam distributions according to the detector thickness for 200 MeV and 250 MeV protons. The detector thickness was varied from 0.01 mm to 1 mm in the GEANT4 simulation.</p

Comparison of GEANT4 results and PSTAR theory.

<p>The red line represents the theoretical results from PSTAR, and the black line corresponds to the values obtained from the GEANT4 simulation.</p