Graphene-doped silicon-carbon materials with multi-interface structures for lithium-ion battery anodes.

The carbon nanomaterials are usually used to improve the electrical conductivity and stability of silicon (Si) anodes for lithium-ion batteries. However, the Si-based composites containing carbon nanomaterials generally show large specific surface area, leading to severe side reactions that generate large amounts of solid electrolyte interphase films. Herein, we embedded graphene oxide (GO) and silicon nanoparticles (Si NPs) uniformly in pitch matrix by solvent dispersion. The internally doped GO reduces the exposed surface and improves the electrical conductivity of the composite. Meanwhile, the multi-interface structures are constructed inside to limit the domains of Si NPs and improve the structural stability of the material. When evaluated as anodes, the Si/graphene/pitch-based carbon composite anode exhibits the outstanding electrochemical properties, delivering a reversible capacity of 820.8 mAh/g at 50 mA g-1, as well as a capacity retention of 93.6 % after 1000 cycles at 2 A/g. In addition, when assembled with the LiFePO4 cathode, the full cell exhibits an impressive capacity retention of 95 % after 100 cycles at 85 mA g-1. This work provides a valuable design concept for the development of Si/carbon anodes.

Atomic-Level Matching Metal-Ion Organic Hybrid Interface to Enhance Energy Storage of Polymer-Based Composite Dielectrics.

In this work, a distinctive "metal-ion organic hybrid interface" (MOHI) between polyimide (PI) and calcium niobate (CNO) nanosheets is designed. The metal ions in the MOHI can achieve atomic-level matching not only with the inorganic CNO, but also with the PI chains, forming uniform and strong chemical bonds. These results are demonstrated by experiment and theory calculations. Significantly, the MOHI reduces the free volume and introduces deep traps across the filler-matrix interfacial area, thus suppressing the electric field distortion in PI-based composite dielectrics. Consequently, PI-based dielectric containing the MOHI exhibits excellent energy storage performance. The energy storage densities (Ue) of the composite dielectric reach 9.42 J cm-3 and 4.75 J cm-3 with energy storage efficiency (η) of 90% at 25 °C and 150 °C respectively, which are 2.6 and 11.6 times higher than those of pure PI. This study provides new ideas for polymer-based composite dielectrics in high energy storage.

Engineering P-Fe2O3-CoP nanosheets for overall freshwater and seawater splitting.

Tailoring surface composition and coordinative environment of catalysts in a nano-meter region often influence their chemical performance. It is reported that CoP exhibits a low dissociation ability of H-OH, originating from the poor desorption of intermediate species. Herein, we provide a feasible method to construct P-Fe2O3-CoP nanosheets through a gas-phase phosphorization process. P doping induces the formation of interfacial structure between Fe2O3 and CoP and the generation of defective structures. The resulting P-Fe2O3-CoP nanosheets afford high freshwater/seawater oxidation activity (250/270 mV@10 mA/cm2) in 1 mol/L (M) KOH, which is even lower than commercial RuO2. Compared with CoP||CoP, P-Fe2O3||P-Fe2O3, and Co3O4||Co3O4, the assembled P-Fe2O3-CoP||P-Fe2O3-CoP exhibits the superior water/seawater electrolysis performance with 1.61/1.65 V@10 mA/cm2. The synergistic effect of P doping, defective structure, and heterojunction leads to high water oxidation efficiency and water splitting efficiency.

Interface Reconstruction from Ruddlesden-Popper Structures Impacts Stability in Lead Halide Perovskite Solar Cells.

The impact of the bulky-cation-modified interfaces on halide perovskite solar cell stability is underexplored. In this work, the thermal instability of the bulky-cation interface layers used in the state-of-the-art solar cells is demonstrated. X-ray photoelectron spectroscopy and synchrotron-based grazing-incidence X-ray scattering measurements reveal significant changes in the chemical composition and structure at the surface of these films that occur under thermal stress. The changes impact charge-carrier dynamics and device operation, as shown in transient photoluminescence, excitation correlation spectroscopy, and solar cells. The type of cation used for surface treatment affects the extent of these changes, where long carbon chains provide more stable interfaces. These results highlight that prolonged annealing of the treated interfaces is critical to enable reliable reporting of performances and to drive the selection of different bulky cations.

A Terahertz Identification Method for Internal Interface Structures of Polymers Based on the Long Short-Term Memory Classification Network.

Polymers are used widely in the power system as insulating materials and are essential to the power grid's security and stability. However, various insulation defects may occur in the polymer., which can lead to severe insulation accidents. Terahertz (THz) detection is a novel non-destructive testing (NDT) method that is able to detect the interface structures inside polymers. The large quantity of information in the THz waveform has potential for the identification of interface types, and the long short-term memory (LSTM) network is one of the most popular artificial intelligence methods for time series data like THz waveform. In this paper, the LSTM classification network was used to identify the internal interfaces of the polymer with the reflected THz pulses of the internal interfaces. The experiment verified that it is feasible to identify and image the void interfaces and impurity interfaces in the polymer using the proposed method.

Tailoring the Surface and Interface Structures of Copper-Based Catalysts for Electrochemical Reduction of CO2 to Ethylene and Ethanol.

Electrochemical CO2 reduction to valuable ethylene and ethanol offers a promising strategy to lower CO2 emissions while storing renewable electricity. Cu-based catalysts have shown the potential for CO2 -to-ethylene/ethanol conversion, but still suffer from low activity and selectivity. Herein, the effects of surface and interface structures in Cu-based catalysts for CO2 -to-ethylene/ethanol production are systematically discussed. Both reactions involve three crucial steps: formation of CO intermediate, CC coupling, and hydrodeoxygenation of C2 intermediates. For ethylene, the key step is CC coupling, which can be enhanced by tailoring the surface structures of catalyst such as step sites on facets, Cu0 /Cuδ+ species and nanopores, as well as the optimized molecule-catalyst and electrolyte-catalyst interfaces further promoting the higher ethylene production. While the controllable hydrodeoxygenation of C2 intermediate is important for ethanol, which can be achieved by tuning the stability of oxygenate intermediates through the metallic cluster induced special atomic configuration and bimetallic synergy induced the double active sites on catalyst surface. Additionally, constraining CO coverage by the complex-catalyst interface and stabilizing CO bond by N-doped carbon/Cu interface can also enhance the ethanol selectivity. The structure-performance relationships will provide the guidance for the design of Cu-based catalysts for highly efficient reduction of CO2 .

Mechanical Instability of Methane Hydrate-Mineral Interface Systems.

Massive methane hydrates occur on sediment matrices in nature. Therefore, sediment-based methane hydrate systems play an essential role in the society and hydrate community, including energy resources, global climate changes, and geohazards. However, a fundamental understanding of mechanical properties of methane hydrate-mineral interface systems is largely limited due to insufficient experimental techniques. Herein, by using large-scale molecular simulations, we show that the mechanical properties of methane hydrate-mineral (silica, kaolinite, and Wyoming-type montmorillonite) interface systems are strongly dictated by the chemical components of sedimentary minerals that determine interfacial microstructures between methane hydrates and minerals. The tensile strengths of hydrate-mineral systems are found to decrease following the order of Wyoming-type montmorillonite- > silica- > kaolinite-based methane hydrate systems, all of which show a brittle failure at the interface between methane hydrates and minerals under tension. In contrast, upon compression, methane hydrates decompose into water and methane molecules, resulting from a large strain-induced mechanical instability. In particular, the failure of Wyoming-type montmorillonite-based methane hydrate systems under compression is characterized by a sudden decrease in the compressive stress at a strain of around 0.23, distinguishing it from those of silica- and kaolinite-based methane hydrate systems under compression. Our findings thus provide a molecular insight into the potential mechanisms of mechanical instability of gas hydrate-bearing sediment systems on Earth.

Fluorophosphate-Based Nonflammable Concentrated Electrolytes with a Designed Lithium-Ion-Ordered Structure: Relationship between the Bulk Electrolyte and Electrode Interface Structures.

We propose a molecular design for lithium (Li)-ion-ordered complex structures in nonflammable concentrated electrolytes that facilitates the Li-ion battery (LIB) electrode reaction to produce safer LIBs. The concentrated electrolyte, composed of Li bis(fluorosulfonyl)amide (FSA) salt and a nonflammable tris(2,2,2-trifluoroethyl) phosphate (TFEP) solvent, showed no electrode reaction (i.e., no Li-ion intercalation into the negative graphite electrode); however, introducing a small molecular additive (acetonitrile [AN]) into concentrated TFEP-based electrolytes is shown to improve the battery electrode reaction, leading to reversible charge/discharge behavior. Combined high-energy X-ray total scattering experiments incorporating all-atom molecular dynamics simulations were used to visualize Li-ion complexes at the molecular level and revealed that (1) Li ions form mononuclear complexes in a concentrated LiFSA/TFEP (without additives) owing to solvation steric effects arising from the molecular size of TFEP and (2) adding a small-sized additive, AN, reduces the steric effect and triggers a change in Li-ion structures, i.e., the formation of a specific Li-ion-ordered structure linked via FSA anions. These Li-ion-ordered complexes stabilize the energy of the lowest unoccupied molecular orbital (LUMO) on FSA anions, which is key to producing an anion-derived solid electrolyte interphase (SEI) at the graphite electrode. We performed in situ surface-enhanced infrared absorption spectroscopy and discussed the electrode/electrolyte interface and SEI formation mechanisms in TFEP-based concentrated electrolyte systems.

Electron and Ion Transfer across Interfaces of the NASICON-Type LATP Solid Electrolyte with Electrodes in All-Solid-State Batteries: A Density Functional Theory Study via an Explicit Interface Model.

NASICON-type oxide Li1+xAlxTi2-x(PO4)3 (LATP) is expected to be a promising solid electrolyte (SE) for all-solid-state batteries (ASSBs) owing to its high ion conductivity and chemical stability. However, its interface properties with electrodes on the atomic scale remain unclear, but it is crucial for rational control of the ASSBs performance. Herein, we focused on the LATP SE with x = 0.17 and investigated the electron and ion transfer behaviors at the interfaces with the Li metal negative electrode and the LiCoO2 (LCO) positive electrode via explicit interface models and density functional theory calculations. Ti reduction was found at the LATP/Li interface. For the LATP/LCO interface, the results indicated the Li-ion transfer from LCO to LATP upon contact until a certain electric double layer is formed under equilibrium, in which LCO is partially reduced. Co-Ti exchange was also found to be favorable where the Li ion moves with Co3+ to LATP. We also explored the possible interfacial processes during annealing by simulating the oxygen removal effect and found that oxygen vacancy can be more easily formed in the LCO at the interface. It implies that partial Li ions move back to LCO for the local charge neutrality. We also demonstrated higher Li chemical potential around the LATP/LCO interfaces, leading to the dynamical Li-ion depletion upon charging. The calculation results and the deduced mechanisms well explain the experimental results so far and provide insights into the interfacial electron and ion transfer upon contact, during annealing, and charging.

Structural plasticity in root-fungal symbioses: diverse interactions lead to improved plant fitness.

Root-fungal symbioses such as mycorrhizas and endophytes are key components of terrestrial ecosystems. Diverse in trophy habits (obligate, facultative or hemi-biotrophs) and symbiotic relations (from mutualism to parasitism), these associations also show great variability in their root colonization and nutritional strategies. Specialized interface structures such as arbuscules and Hartig nets are formed by certain associations while others are restricted to non-specialized intercellular or intracellular hyphae in roots. In either case, there are documented examples of active nutrient exchange, reinforcing the fact that specialized structures used to define specific mycorrhizal associations are not essential for reciprocal exchange of nutrients and plant growth promotion. In feremycorrhiza (with Austroboletus occidentalis and eucalypts), the fungal partner markedly enhances plant growth and nutrient acquisition without colonizing roots, emphasizing that a conventional focus on structural form of associations may have resulted in important functional components of rhizospheres being overlooked. In support of this viewpoint, mycobiome studies using the state-of-the-art DNA sequencing technologies have unearthed much more complexity in root-fungal relationships than those discovered using the traditional morphology-based approaches. In this review, we explore the existing literature and most recent findings surrounding structure, functioning, and ecology of root-fungal symbiosis, which highlight the fact that plant fitness can be altered by taxonomically/ecologically diverse fungal symbionts regardless of root colonization and interface specialization. Furthermore, transition from saprotrophy to biotrophy seems to be a common event that occurs in diverse fungal lineages (consisting of root endophytes, soil saprotrophs, wood decayers etc.), and which may be accompanied by development of specialized interface structures and/or mycorrhiza-like effects on plant growth and nutrition.