Fluorine-Doped Antiperovskite Electrolyte for All-Solid-State Lithium-Ion Batteries

A fluorine-doped antiperovskite Li-ion conductor Li2 (OH)X (X=Cl, Br) is shown to be a promising candidate for a solid electrolyte in an all-solid-state Li-ion rechargeable battery. Substitution of F(-) for OH(-) transforms orthorhombic Li2 OHCl to a room-temperature cubic phase, which shows electrochemical stability to 9 V versus Li(+) /Li and two orders of magnitude higher Li-ion conductivity than that of orthorhombic Li2 OHCl. An all-solid-state Li/LiFePO4 with F-doped Li2 OHCl as the solid electrolyte showed good cyclability and a high coulombic efficiency over 40 charge/discharge cycles.

Antiperovskite Li3OCl Superionic Conductor Films for Solid-State Li-Ion Batteries

Antiperovskite Li₃OCl superionic conductor films are prepared via pulsed laser deposition using a composite target. A significantly enhanced ionic conductivity of 2.0 × 10^-4 S cm^-1 at room temperature is achieved, and this value is more than two orders of magnitude higher than that of its bulk counterpart. The applicability of Li₃OCl as a solid electrolyte for Li-ion batteries is demonstrated.

Tailoring the photocatalytic activity of layered perovskites by opening the interlayer vacancy via ion-exchange reactions

The photocatalytic activity of the layered perovskite K₂La₂Ti₃O₁₀ was regulated by an ion-exchange reaction with a series of cations – Ca²⁺, Sr²⁺, and Ba²⁺. The underlying mechanism of the improved performance and an effective model for designing the photocatalyst were discussed.

CuIn(S,Se)(2) thin films prepared from a novel thioacetic acid-based solution and their photovoltaic application

Low-cost and high-yield preparation of CuInSe2 films is the bottleneck for promising CuInSe2-based thin film solar cells. Here, we developed a simple, safe and cost-effective method using thioacetic acid to fabricate the absorber films of CuIn(S,Se)2 (CISSe). Dissolution of Cu2O and In(OH)3 in thioacetic acid was attributed to the strong coordination ability of S. The adhesive precursor solution can be prepared without any heating, centrifugation and inert gas protection, superior to the previously reported methods. The precursor CISSe layer was easily deposited in air by spin coating to ensure low cost. Uniform and compact CISSe thin films with well-crystallized and pure-phased CISSe grains were obtained after one step annealing. The as-prepared CISSe thin films were successfully applied to solar cells and a energy conversion efficiency of 6.75% was achieved. This facile preparation provides a low-cost and easy method to fabricate Cu-based thin film solar cells.

In situ growth of a MoSe2/Mo counter electrode for high efficiency dye-sensitized solar cells

A facile and economical MoSe₂/Mo structure was in situ prepared to replace the currently preferred expensive Pt and FTO counter electrode (CE) in dye-sensitized solar cells.

Li-rich anti-perovskite Li3OCl films with enhanced ionic conductivity

Lithium-rich anti-perovskite Li₃OCl solid electrolyte films with significantly enhanced ionic conductivity were prepared by pulsed laser deposition.

Enhanced electron transport in Nb-doped TiO2 nanoparticles via pressure-induced phase transitions

Anatase TiO2 is one of the most important energy materials but suffers from poor electrical conductivity. Nb doping has been considered as an effective way to improve its performance in the applications of photocatalysis, solar cells, Li batteries, and transparent conducting oxide films. Here, we report the further enhancement of electron transport in Nb-doped TiO2 nanoparticles via pressure-induced phase transitions. The phase transition behavior and influence of Nb doping in anatase Nb-TiO2 have been systematically investigated by in situ synchrotron X-ray diffraction and Raman spectroscopy. The bulk moduli are determined to be 179.5, 163.3, 148.3, and 139.0 GPa for 0, 2.5, 5.0, and 10.0 mol % Nb-doped TiO2, respectively. The Nb-concentration-dependent stiffness variation has been demonstrated: samples with higher Nb concentrations have lower stiffness. In situ resistance measurements reveal an increase of 40% in conductivity of quenched Nb-TiO2 in comparison to the pristine anatase phase. The pressure-induced conductivity evolution is discussed in detail in terms of the packing factor model, which provides direct evidence for the rationality of the correlation of packing factors with electron transport in semiconductors. Pressure-treated Nb-doped TiO2 with unique properties surpassing those in the anatase phase holds great promise for energy-related applications.

Graphene/Fe2O3/SnO2 ternary nanocomposites as a high-performance anode for lithium ion batteries

We report an rGO/Fe2O3/SnO2 ternary nanocomposite synthesized via homogeneous precipitation of Fe2O3 nanoparticles onto graphene oxide (GO) followed by reduction of GO with SnCl2. The reduction mechanism of GO with SnCl2 and the effects of reduction temperature and time were examined. Accompanying the reduction of GO, particles of SnO2 were deposited on the GO surface. In the graphene nanocomposite, Fe2O3 nanoparticles with a size of ∼20 nm were uniformly dispersed surrounded by SnO2 nanoparticles, as demonstrated by transmission electron microscopy analysis. Due to the different lithium insertion/extraction potentials, the major role of SnO2 nanoparticles is to prevent aggregation of Fe2O3 during the cycling. Graphene can serve as a matrix for Li+ and electron transport and is capable of relieving the stress that would otherwise accumulate in the Fe2O3 nanoparticles during Li uptake/release. In turn, the dispersion of nanoparticles on graphene can mitigate the restacking of graphene sheets. As a result, the electrochemical performance of rGO/Fe2O3/SnO2 ternary nanocomposite as an anode in Li ion batteries is significantly improved, showing high initial discharge and charge capacities of 1179 and 746 mAhg(-1), respectively. Importantly, nearly 100% discharge-charge efficiency is maintained during the subsequent 100 cycles with a specific capacity above 700 mAhg(-1).

Phase-controlled synthesis of cobalt sulfides for lithium ion batteries

The polyhedral CoS(2) with a narrow size distribution was synthesized by a facile solid-state assembly process in a sealed silica tube. The flux of potassium halide (KX; X = Cl, Br, I) plays a crucial role in the formation of polyhedrons and the size distribution. The S(2)(2-) groups in CoS(2) can be controllably withdrawn during heat treatment in air. The obtained phases and microstructures of CoS(2), Co(3)S(4), CoS, Co(9)S(8), and CoO depended on heating temperature and time. These cobalt materials, successfully used as the electrodes of lithium ion batteries, possessed good cycling stability in lithium ion batteries. The discharge capacities of 929.1 and 835.2 mAh g(-1) were obtained for CoS(2) and CoS respectively, and 76% and 71% of the capacities remained after 10 cycles. High capacities and good cycle performance make them promising candidates for lithium ion batteries. The approach combining solid-state assembly and heat treatment provides a simple and versatile way to prepare various metal chalcogeides for energy storage applications.

Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers

We report on terahertz quantum-cascade lasers (THz QCLs) based on first-order lateral distributed-feedback (lDFB) gratings, which exhibit continuous-wave operation, high output powers (>8 mW), and single-mode emission at 3.3-3.4 THz. A general method is presented to determine the coupling coefficients of lateral gratings in terms of the coupled-mode theory, which demonstrates that large coupling strengths are obtained in the presence of corrugated metal layers. The experimental spectra are in agreement with simulations of the lDFB cavities, which take into account the reflective end facets.

One-step high-temperature solvothermal synthesis of TiO2/sulfide nanocomposite spheres and their solar visible-light applications

A one-step high-temperature hydrated-sulfate assisted solvothermal method has been developed to synthesize TiO(2)/sulfide nanocomposite spheres. Different hybrid spheres of TiO(2)/CdS, TiO(2)/Cu(2)S, TiO(2)/FeS, TiO(2)/Co(9)S(8), and TiO(2)/ZnS were readily prepared by exploiting different hydrated sulfate. The hydrated sulfate has been proved to play multifunctional roles during the synthetic process, such as spherical template, water supplier, and composition controller. Nanocrystal CdS can be reduced from CdSO(4) at a high solvothermal temperature of 350 °C, and the TiO(2)/CdS nanocomposite spheres prepared by this method exhibit superior visible-light-driven photocatalytic efficiency because of its effective heterointerface and high crystallinity.

Intelligent hydrated-sulfate template assisted preparation of nanoporous TiO(2) spheres and their visible-light application

Hydrated metal sulfates (MSO(4)·xH(2)O, M = Zn, Fe, Co, Mg, etc.) were proposed to be intelligent templates to solvothermally synthesize nanoporous TiO(2) spheres with tunable chamber structures from hollow to solid and hybrid compositions. During the reaction, hydrated sulfate serves simultaneously as spherical template, water supplier, and composition controller, and it can be easily removed by washing. The as-prepared anatase TiO(2) spheres were evidenced to contain highly crystallized TiO(2) nanocrystals hybridized with a small amount of metal oxide from the hydrated sulfate. The formation mechanism of the hollow spheres involves the self-conglobation of hydrated sulfate, the hydrolysis of tetrabutyl titanate on the spherical templates, and the subsequent process of solvothermal crystallization. The proposed hydrated-sulfate assisted solvothermal (HAS) strategy was demonstrated to be widely applicable to various systems. When applied to visible-light photocatalysis, the hybrid TiO(2) spheres exhibit excellent photocatalytic performance, benefiting from the reduced charge recombination rate contributed by the heterojunctions of TiO(2) and the hybridized metal oxides.