Deciphering Interphase Instability of Lithium Metal Batteries with Localized High-Concentration Electrolytes at Elevated Temperatures

Lithium metal batteries (LMBs), when coupled with a localized high-concentration electrolyte and a high-voltage nickel-rich cathode, offer a solution to the increasing demand for high energy density and long cycle life. However, the aggressive electrode chemistry poses safety risks to LMBs at higher temperatures and cutoff voltages. Here, we decipher the interphase instability in LHCE-based LMBs with a Ni0.8Co0.1Mn0.1O2 cathode at elevated temperatures. Our findings reveal that the generation of fluorine radicals in the electrolyte induces the solvent decomposition and consequent chain reactions, thereby reconstructing the cathode electrolyte interphase (CEI) and degrading battery cyclability. As further evidenced, introducing an acid scavenger of dimethoxydimethylsilane (DODSi) significantly boosts CEI stability with suppressed microcracking. A Ni0.8Co0.1Mn0.1O2||Li cell with this DODSi-functionalized LHCE achieves an unprecedented capacity retention of 93.0% after 100 cycles at 80 {\deg}C. This research provides insights into electrolyte engineering for practical LMBs with high safety under extreme temperatures.Comment: 10 pages, 8 figure

Tuning electrochemical catalytic activity of defective 2D terrace MoSe2 heterogeneous catalyst via Co doping

This study presents successful growth of defective 2D terrace MoSe2/CoMoSe lateral heterostructures (LH), bilayer and multilayer MoSe2/CoMoSe LH, and vertical heterostructures (VH) nanolayers by doping metal Co (cobalt) element into MoSe2 atomic layers to form a CoMoSe alloy at the high temperature (~900 °C). After the successful introduction of metal Co heterogeneity in the MoSe2 thin layers, more active sites can be created to enhance hydrogen evolution reaction (HER) activities combining with metal Co catalysis, through the mechanisms including (1) atomic arrangement distortion in CoMoSe alloy nanolayers, (2) atomic level coarsening in LH interfaces and terrace edge layer architecture in VH, (3) formation of defective 2D terrace MoSe2 nanolayers heterogeneous catalyst via metal Co doping. The HER investigations indicated that the obtained products with LH and VH exhibited an improved HER activity in comparison with those from the pristine 2D MoSe2 electrocatalyst and LH type MoSe2/CoMoSe. The present work shows a facile yet reliable route to introduce metal ions into ultrathin 2D transition metal dichalcogenides (TMDCS) and produce defective 2D alloy atomic layers for exposing active sites, and thus eventually improve their electrocatalytic performance

Roll-to-Roll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials

Creating a robust superhydrophobic surface on the conventional engineering materials at mass production is of great importance for self–cleaning, anti–icing, non–wetting surface and low flow resistance in industrial applications. Herein, we report a roll–to–roll strategy to create durable and robust superhydrophobic surfaces with designed micro–/nano– scale hierarchical structures on many conventional engineering materials by combining electrical discharge machining, coating of carbon nanoparticles, and followed by oil penetration and drying. The treated surface shows good superhydrophobic properties with static water contact angle of 170±2o and slide angle of 3±1o. The treated surface also exhibits good resilience and maintains the performance after tested in various harsh conditions including water flushing for several days, sand abrasion, scratching with sandpapers and corrosive solution. Significantly, the superhydrophobic surfaces also shows a high efficiency of self–cleaning properties even after oil–contamination during applications

Strong enhancement of photoresponsivity with shrinking the electrodes spacing in few layer GaSe photodetectors

A critical challenge for the integration of the optoelectronics is that photodetectors have relatively poor sensitivities at the nanometer scale. It is generally believed that a large electrodes spacing in photodetectors is required to absorb sufficient light to maintain high photoresponsivity and reduce the dark current. However, this will limit the optoelectronic integration density. Through spatially resolved photocurrent investigation, we find that the photocurrent in metal-semiconductor-metal (MSM) photodetectors based on layered GaSe is mainly generated from the photoexcited carriers close to the metal-GaSe interface and the photocurrent active region is always close to the Schottky barrier with higher electrical potential. The photoresponsivity monotonically increases with shrinking the spacing distance before the direct tunneling happen, which was significantly enhanced up to 5,000 AW-1 for the bottom contacted device at bias voltage 8 V and wavelength of 410 nm. It is more than 1,700-fold improvement over the previously reported results. Besides the systematically experimental investigation of the dependence of the photoresponsivity on the spacing distance for both the bottom and top contacted MSM photodetectors, a theoretical model has also been developed to well explain the photoresponsivity for these two types of device configurations. Our findings realize shrinking the spacing distance and improving the performance of 2D semiconductor based MSM photodetectors simultaneously, which could pave the way for future high density integration of 2D semiconductor optoelectronics with high performances.Comment: 25 pages, 4 figure

Tunable electronic properties of graphene through controlling bonding configurations of doped nitrogen atoms

Single–layer and mono–component doped graphene is a crucial platform for a better understanding of the relationship between its intrinsic electronic properties and atomic bonding configurations. Large–scale doped graphene films dominated with graphitic nitrogen (GG) or pyrrolic nitrogen (PG) were synthesized on Cu foils via a free radical reaction at growth temperatures of 230–300 °C and 400–600 °C, respectively. The bonding configurations of N atoms in the graphene lattices were controlled through reaction temperature, and characterized using Raman spectroscopy, X–ray photoelectron spectroscopy and scanning tunneling microscope. The GG exhibited a strong n–type doping behavior, whereas the PG showed a weak n–type doping behavior. Electron mobilities of the GG and PG were in the range of 80.1–340 cm2 V−1·s−1 and 59.3–160.6 cm2 V−1·s−1, respectively. The enhanced doping effect caused by graphitic nitrogen in the GG produced an asymmetry electron–hole transport characteristic, indicating that the long–range scattering (ionized impurities) plays an important role in determining the carrier transport behavior. Analysis of temperature dependent conductance showed that the carrier transport mechanism in the GG was thermal excitation, whereas that in the PG, was a combination of thermal excitation and variable range hopping

Monolayer hydrophilic MoS2 with strong charge trapping for atomically thin neuromorphic vision systems

Effective control of electrical and optoelectronic properties of two-dimensional layered materials, one of the key requirements for applications in advanced optoelectronics with multiple functions, has been hindered by the difficulty of elemental doping, which is commonly utilized in Si technology. In this study, we proposed a new method to synthesize hydrophilic MoS2 monolayers through covalently introducing hydroxyl groups during their growth process. These hydroxyl groups exhibit a strong capability of charge trapping, and thus the hydrophilic MoS2 monolayers achieve excellent electrical, optical, and memory properties. Optical memory transistors, made from a single component of monolayer hydrophilic MoS2, exhibit not only excellent light-dependent and time-dependent photoelectric performance, but also good photo-responsive memory characteristics with over multi-bit storage and more than 104 switching ratios. Atomically thin neuromorphic vision systems (with a concept of proof of 10 × 10 neuromorphic visual image) are manufactured from arrays of hydrophilic MoS2 optical memory transistors, showing high quality image sensing and memory functions with a high color resolution. These results proved our new concepts to realize image memorization and simplify the pixel matrix preparation process, which is a significant step toward the development of future artificial visual systems

Fast, multicolor photodetection with graphene-contacted p-GaSe/n-InSe van der Waals heterostructures

The integration of different two-dimensional materials within a multilayer van der Waals (vdW) heterostructure offers a promising technology for high performance opto-electronic devices such as photodetectors and light sources. Here we report on the fabrication and electronic properties of vdW heterojunction diodes composed of the direct band gap layered semiconductors InSe and GaSe and transparent monolayer graphene electrodes. We show that the type II band alignment between the two layered materials and their distinctive spectral response, combined with the short channel length and low electrical resistance of graphene electrodes, enable efficient generation and extraction of photoexcited carriers from the heterostructure even when no external voltage is applied. Our devices are fast ( ~ 1 μs), self-driven photodetectors with multicolor photoresponse ranging from the ultraviolet to the near-infrared and offer new routes to miniaturized optoelectronics beyond present semiconductor materials and technologies

Ultrafast and Sensitive Self-Powered Photodetector Featuring Self-Limited Depletion Region and Fully Depleted Channel with van der Waals Contacts

Self-powered photodetectors with great potential for implanted medical diagnosis and smart communications have been severely hindered by the difficulty of simultaneously achieving high sensitivity and fast response speed. Here, we report an ultrafast and highly sensitive self-powered photodetector based on two-dimensional (2D) InSe, which is achieved by applying a device architecture design and generating ideal Schottky or ohmic contacts on 2D layered semiconductors, which are difficult to realize in the conventional semiconductors owing to their surface Fermi-level pinning. The as-fabricated InSe photodiode features a maximal lateral self-limited depletion region and a vertical fully depleted channel. It exhibits a high detectivity of 1.26 × 1013 Jones and an ultrafast response speed of ∼200 ns, which breaks the response speed limit of reported self-powered photodetectors based on 2D semiconductors. The high sensitivity is achieved by an ultralow dark current noise generated from the robust van der Waals (vdW) Schottky junction and a high photoresponsivity due to the formation of a maximal lateral self-limited depletion region. The ultrafast response time is dominated by the fast carrier drift driven by a strong built-in electric field in the vertical fully depleted channel. This device architecture can help us to design high-performance photodetectors utilizing vdW layered semiconductors

Carbon Nanostructure-Based Field-Effect Transistors for Label-Free Chemical/Biological Sensors

Over the past decade, electrical detection of chemical and biological species using novel nanostructure-based devices has attracted significant attention for chemical, genomics, biomedical diagnostics, and drug discovery applications. The use of nanostructured devices in chemical/biological sensors in place of conventional sensing technologies has advantages of high sensitivity, low decreased energy consumption and potentially highly miniaturized integration. Owing to their particular structure, excellent electrical properties and high chemical stability, carbon nanotube and graphene based electrical devices have been widely developed for high performance label-free chemical/biological sensors. Here, we review the latest developments of carbon nanostructure-based transistor sensors in ultrasensitive detection of chemical/biological entities, such as poisonous gases, nucleic acids, proteins and cells