An important trend in electronics involves the development of materials, mechanical designs and manufacturing strategies that enable the use of unconventional substrates, such as polymer films, metal foils, paper sheets or rubber slabs. The last possibility is particularly challenging because the systems must accommodate not only bending but also stretching. Although several approaches are available for the electronics, a persistent difficulty is in power supplies that have similar mechanical properties, to allow their co-integration with the electronics. Here we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual 'self-similar' interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of B1.1 mAh cm À 2 . Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.

High-performance miniature power sources could enable new microelectronic systems. Here we report lithium ion microbatteries having power densities up to 7.4 mW cm À 2 mm À 1 , which equals or exceeds that of the best supercapacitors, and which is 2,000 times higher than that of other microbatteries. Our key insight is that the battery microarchitecture can concurrently optimize ion and electron transport for high-power delivery, realized here as a three-dimensional bicontinuous interdigitated microelectrodes. The battery microarchitecture affords trade-offs between power and energy density that result in a high-performance power source, and which is scalable to larger areas.

No abstract

Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO 2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO 2 cathode reversibly decreases from B5.4 to 3.7 W m À 1 K À 1 , and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li 1.0 CoO 2 to Li 0.6 CoO 2 . The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-statedependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices.

PtS2 is a newly developed group 10 2D layered material with high carrier mobility, wide band gap tunability, strongly bound excitons, symmetrical metallic and magnetic edge states, and ambient stability, making it attractive in nanoelectronic, optoelectronic, and spintronic fields. To the aim of application, a large-scale synthesis is necessary. For transition-metal dichalcogenide (TMD) compounds, a thermally assisted conversion method has been widely used to fabricate wafer-scale thin films. However, PtS2 cannot be easily synthesized using the method, as the tetragonal PtS phase is more stable. Here, we use a specified quartz part to locally increase the vapor pressure of sulfur in a chemical vapor deposition furnace and successfully extend this method for the synthesis of PtS2 thin films in a scalable and controllable manner. Moreover, the PtS and PtS2 phases can be interchangeably converted through a proposed strategy. Field-effect transistor characterization and photocurrent measurements suggest that PtS2 is an ambipolar semiconductor with a narrow band gap. Moreover, PtS2 also shows excellent gas-sensing performance with a detection limit of ∼0.4 ppb for NO2. Our work presents a relatively simple way of synthesizing PtS2 thin films and demonstrates their promise for high-performance ultrasensitive gas sensing, broadband optoelectronics, and nanoelectronics in a scalable manner. Furthermore, the proposed strategy is applicable for making other PtX2 compounds and TMDs which are compatible with modern silicon technologies.

No abstract

GaSe layers with thicknesses ranging from a monolayer to 100 nm are successfully mechanically exfoliated for use in gas sensing. In combination with density functional theory calculations, general guidelines to determine the number of layers using Raman spectra are presented. With decreasing layer numbers, quantum confinement induces a red-shift for out-of-plane modes and a blue-shift for in-plane modes. The relative Raman shifts of the out-of-plane vibrational modes A A ( (1 1 ) ′ ′ mode of monolayer GaSe (≈−1.99 × 10 −2 cm −1 K −1 ) being almost double that of 100 layer GaSe (≈−1.22 × 10 −2 cm −1 K −1 ). Finally, the exfoliated GaSe is used for gas sensing and shows high sensitivity, displaying a minimum detection limit of 4 ppm for NH 3 at room temperature, confirming the potential of mechanically exfoliated GaSe in high-sensitivity gas sensors.

A photon assisted SnS2-based gas sensor with an ultra-high sensitivity of 3 ppb NO2 has been achieved at room temperature.