Rapid and Economic Synthesis of a Li7PS6 Solid Electrolyte from a Liquid Approach

Solid electrolytes are the key to realize future solid-state batteries that show the advantages of high energy density and intrinsic safety. However, most solid electrolytes require long time and energy-consuming synthesis conditions of either extended ball milling or high-temperature solid-state reactions, impeding practical applications of solid electrolytes for large-scale systems. Here, we report a new and rapid liquid-based synthetic method for preparing a high-purity Li₇PS₆ solid electrolyte through the stoichemical reaction of Li₃PS₄ and Li₂S. This method relies on facile and low-cost solution-based soft chemistry to complete chemical reaction in extensively short time (2 h). The prepared Li₇PS₆ solid electrolyte shows a high phase purity, an impressive ionic conductivity (0.11 mS cm^-1), and a reasonable electrochemical stability with a metallic lithium anode. Our results highlight the use of an economic and nontoxic solvent to quickly synthesize a Li₇PS₆ solid electrolyte, which would promote the development of solid-state batteries for next-generation energy storage systems.

CFx primary batteries based on fluorinated carbon nanocages

The material with the fluorination level of x = 0.98 reaches the specific capacity of 850 mA h g⁻¹, i.e., its theoretical value.

The Coupled Straintronic-Photothermic Effect

We describe the coupled straintronic-photothermic effect where coupling between bandgap of the 2D layered semiconductor under localized strains, optical absorption and the photo-thermal effect results in a large chromatic mechanical response in TMD-nanocomposites. Under the irradiation of visible light (405 nm to 808 nm), such locally strained atomic thin films based on 2H-MoS2 embedded in an elastomer such as poly (dimethyl) siloxane matrix exhibited a large amplitude of photo-thermal actuation compared to their unstrained counterparts. Moreover, the locally strain engineered nanocomposites showed tunable mechanical response giving rise to higher mechanical stress at lower photon energies. Scanning photoluminescence spectroscopy revealed a change in bandgap of 30 meV between regions encompassing highly strained compared to the unstrained few layers. For 1.6% change in the bandgap, the macroscopic photo-thermal response increased by a factor of two. Millimeter scale bending actuators based on the locally strained 2H-MoS2 resulted in significantly enhanced photo-thermal actuation displacements compared to their unstrained counterparts at lower photon energies and operated up to 30 Hz. Almost 1 mN photo-activated force was obtained at 50 mW and provided long-term stability. This study demonstrates a new mechanism in TMD-nanocomposites that would be useful for developing broad range of transducers.

Exfoliated WS2-Nafion Composite based Electromechanical Actuators

The ability to convert electrical energy into mechanical motion is of significant interest in many energy conversion technologies. Here, we demonstrate the first liquid phase exfoliated WS₂-Nafion nanocomposite based electro-mechanical actuators. Highly exfoliated layers of WS₂ mixed with Nafion solution, solution cast and doped with Li⁺ was studied as electromechanical actuators. Resonant Raman spectroscopy, X-ray photo-electron-spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and AC impedance spectroscopy were used to study the structure, photoluminescence, water uptake, mechanical and electromechanical actuation properties of the exfoliated nanocomposites. A 114% increase in elastic modulus (dry condition), 160% increase in proton conductivity, 300% increase in water uptake, cyclic strain amplitudes of ~0.15% for 0.1 Hz excitation frequency, tip displacements greater than nanotube-Nafion and graphene-Nafion actuators and continuous operation for more than 5 hours is observed for TMD-Nafion actuators. The mechanism behind the increase in water uptake is a result of oxygen atoms occupying the vacancies in the hydrophilic exfoliated flakes and subsequently bonding with water, not possible in Nafion composites based on carbon nanotube and graphene.