Abstract: Rechargeable batteries can effectively mitigate the increasing crisis associated with clean energy storage technologies. The alkali metal-ion based rechargeable batteries require a low diffusion barrier, a low average open-circuit voltage (OCV), and a high storage capacity for their superior performance. Using comprehensive first-principle calculations, we demonstrate that calcium carbide monolayer (Ca2C-ML) MXene meets all the aforementioned criteria and is a superior anode material for lithium (Li), sodium (Na), and potassium (K) metal-ion batteries. By first-principles calculations, the structural and electronic properties of Ca2C-ML and its extensive ion battery applications are studied. The adsorption properties of Li, Na, and K alkali ions on the Ca2C-ML sheet confirm excellent charge transfer and electrical conductivity. The ultra-low diffusion barriers of 0.027, 0.059, and 0.028 eV for Li, Na, and K alkali ions, respectively, indicate the superior mobility and fast cycling caliber (metal adsorption and desorption) of the Ca2C-ML. The OCV of the Ca2C-ML is 0.10, 0.24, and 0.28 V for Li, Na, and K-ions, respectively, ensuring a better battery performance. The specific capacity of 582 mAh g−1 is achieved for all three cases, which is much higher than that of a traditional graphite anode with Li, Na, and K ions. The volume expansion during the intercalation is negligible for all three cases, indicating long term structural integrity of the anode using Ca2C-ML. Our investigations suggest that the newly designed 2D Ca2C-ML is a suitable anode candidate for use in the next-generation of high-performance Li, Na, and K-ion batteries.

Abstract: An oxidizable metal diffusion barrier inserted between the active metal electrode and the switching layer decreases the electroforming voltage and enhances the switching stability and synaptic performances in TaOx-based conducting bridge memristor devices. The TiW barrier layer avoids an excessive metal ion diffusion into the switching layer, while the TiWOx interfacial layer is formed between the barrier and the switching layer. It modulates the oxygen vacancy distribution at the top interface and contributes to the formation and rupture of the metal ion-oxygen vacancy hybrid conducting bridge. We observe that the device that relies upon non-hybrid (metal ions only) conducting bridge suffers from poor analogous performance. Meanwhile, the device made with the barrier layer is capable of providing 2-bit memory and robust 50 stable epochs. TaOx also acts as resistance for suppressing and a thermal enhancement layer, which helps to minimize overshooting current. The enhanced analog device with high linear weight update shows multilevel cell characteristics and stable 50 epochs. To validate the neuromorphic characteristic of the devices, a simulated neural network of 100 synapses is used to recognize 10 × 10 pixel images.

Abstract: To solve the issue of elemental interdiffusion between protective coating and superalloy substrate during high-temperature service, an AlCoCrNiMo high-entropy alloy (HEA) diffusion barrier was deposited by direct current magnetron sputtering between NiAlHf protective coating and Ni-based single crystal superalloy (Rene N5). The interdiffusion behavior and high-temperature oxidation resistance of the coating system were investigated via isothermal oxidation at 1373 K. After long-term oxidation at 1373 K, no interdiffusion zone (IDZ), secondary reaction zone (SRZ) and rod/needle-like topologically close-packed (TCP) precipitates were observed in the coating system with HEA diffusion barrier. Besides, the NiAlHf coating exhibited an improved oxidation resistance with the addition of HEA diffusion barrier. The results indicate that the HEA diffusion barrier can suppress the interdiffusion of alloying elements between substrate and coating effectively, which is attributed to the sluggish diffusion effect of HEA and the in-suit formed alumina layers at the substrate/HEA and HEA/NiAlHf interfaces during high-temperature oxidation. Moreover, it was found that the Co element in HEA layer also plays an important role in suppressing the formation of SRZ and TCP precipitates in the superalloy.

Abstract: The structural stability of carbon and the high theoretical capacity of silicon was the motivation for investigating the prospects of layered silicon carbide (SiC). The density functional theory (DFT) based computations and first-principles molecular dynamics (MD) simulations were performed to determine the likelihood of being able to use 2D SiC layers as a lithium intercalation compound. The calculations were performed using dispersion corrected exchange correlation and this revealed the stability of the layers, and the transfer of charge from Li to the host during intercalation was at a maximum storage capacity of 699 mA h g−1. The layers offered better flexibility, a higher rate capability and a three times larger capacity when compared to graphite bilayers. The diffusion barrier calculated here, with a small energy barrier of 0.40 eV, illustrated a good rate capability. The findings and comparison with graphite revealed that layered SiC is an appropriate anode material for used in lithium ion batteries (LIBs) because of its structural firmness, high electronic conductivity, low diffusion barrier and high storage capacity.

Abstract: After obtaining Ti 3C 2 MXene structures terminated with O, S, Se, F, Cl, and Br, we calculate the energy barrier for Li-ion diffusion on the surface of each MXene, being the first to report on the Li-ion diffusivity in Cl and Br terminated Ti 3C 2. We find that the Ti 3C 2Cl 2 MXene has the lowest diffusion barrier, substituting the Ti 3C 2S 2 reported in the literature so far. In addition, a study on the adsorption energies indicates that the top binding position is the most stable adsorption position for the Li-ion. Furthermore, it is shown that the adsorption energy depends on the electronegativity of the termination atoms, as well as the distance between the terminations, the Li, and the surface Ti-atoms. Finally, we show that the bond valence sum method provides an indication of the transition state of the Li-ion and can serve as a comparison tool for the diffusion barriers of different structures.

Abstract: Light- and elevated temperature-induced degradation (LeTID) is assumed to be triggered by the hydrogen content in the crystalline silicon bulk. This article investigates differently thick atomic layer-deposited aluminum oxide (AlOx) layers acting as diffusion barrier for hydrogen originating from a hydrogen-rich silicon nitride (SiN y :H) layer. We demonstrate that the extent of LeTID can be significantly reduced by adjusting the AlO x layer thickness up to 25 nm. To directly measure the diffusing species, a deuterium-rich SiN y :D layer is deposited and the deuterium content is measured in an amorphous Si layer at the back side of the wafer via secondary ion mass spectrometry. Thus, a diffusion length of deuterium in the AlO x layer of $({3.8 \pm 1.6}){\boldsymbol{\ }}\;{\text{nm}}$ is determined at a firing temperature of $({743 \pm 2})^\circ {\rm{C}}$ . These results are not only a contribution to determine the LeTID formation dynamics, but also can be used to control LeTID in silicon wafers and solar cells.

Abstract: The investigation of electrochemical properties of Molybdenum Nitride (Mo2N) 2D monolayer for its application as an anode material in Li-ion batteries have been carried out by using first-principles calculations. The ab-initio molecular dynamics (AIMD) and optimization calculations reveal that the Mo2N monolayer with and without Li-adsorption is structurally stable. The low diffusion barrier (∼0.035 eV) and the high specific charge capacity (∼520 mA hg−1) with Li-adsorption indicate easy diffusion and high cyclic ability of Mo2N monolayer. The low open circuit voltage (∼0.4 V) reaffirms that the proposed material may be an efficient candidate for anode material in Li-ion batteries.

Abstract: Stable operation at elevated temperature has significant importance for the commercialization of solid oxide fuel cells. In particular, interdiffusion at the interface between the cathode and the electrolyte during long-term operation leads to the formation of insulating phases, significantly reducing the cell performance. In this study, a simple wet chemical coating method was employed to fabricate a thin, dense Gd0.2Ce0.8O2−δ (GDC) diffusion barrier layer between the La0.6Sr0.4Co0.2Fe0.8-O3−δ (LSCF) cathode and yttria-stabilized zirconia (YSZ) electrolyte with a gelatin hydrogel-based precursor solution. The fabrication of thin dense film GDC using a simple spin coating method was enabled by the interfacial self-assembly of organic/inorganic composites between the precursor and hydrogel. The anode-supported single cell with a hydrogel-assisted GDC chemical diffusion barrier layer showed improved electrochemical performance due to fast ionic conduction via short and highly percolated diffusion pathways, maintaining the initial performance after the accelerated heat treatment at 900 °C for 100 h by preventing the cation interdiffusion at the interface.

Abstract: Vacuum hot-rolled bonding (VHRB) titanium (Ti)-steel clad composites have been increasingly serving in both severe corrosion and heavy load conditions, and their overall properties severely depend on the microstructure of interfacial reaction layer. Notably, introducing an appropriate interdiffusion barrier to minimize the brittle Fe–Ti intermetallics has still been a popular scheme for optimizing their interfacial properties. In this work, with two low-alloyed steels of 0.06 and 0.16 wt% carbon (C) contents employed, the pure Ti -steel composite samples were successfully prepared via vacuum hot-compressed bonding (VHCB) in Gleeble-3500 system under the identical temperature/reduction/rate condition of 850 °C/70 %/0.01s−1. The interfacial reaction, microstructure and tensile property in two Ti-steel composites were investigated to estimate the C content effect via various characterizations, and the mechanisms were clarified. Results indicated that the diffusion of Ti, Fe and C mainly occurred in the interfacial reaction layers of two composites, and accordingly the reaction products of TiFe, TiFe2 and TiC formed, together with the C-depleted α-Fe zone. The nanoscale TiC particles were mainly located at the steel side, and increased with the increasing C content. Correspondingly, the brittle TiFe layer and TiFe2 layer decreased due to the increased TiC layer acting as a diffusion barrier. This led to an evident decrease of percent cleavage fracture area (CA, %) from 77% to 52% and a significant increase of interfacial tensile strength from 182 to 344 MPa.

Abstract: Long-term stability of organic-inorganic hybrid perovskite solar cells (PSCs) is inhibited by ion diffusion Herein, we introduce a thermally stable and hydrophobic silicone resin layer with a network structure as an interfacial layer between the perovskite and the hole-transporting layer (HTL) Experimental and theoretical investigations confirm that the small Si-O-Si unit in the network forms both Si-I and Pb-O bonds with the perovskite surface, which physically and chemically inhibit the diffusion and self-release of iodine Besides, the silicone resin layer suppresses the thermal crystallization of spiro-OMeTAD and optimizes the interfacial energy level alignment for hole extraction The power conversion efficiency (PCE) of a perovskite solar cell with a silicone resin layer is improved to 2111% The device maintains more than 901% of its original PCE after 1200 h under 85 °C thermal stress, 996% after 2000 h under RH ∼55 ± 5%, and 83% of its original PCE after light soaking in air for 1037 h