China Spallation Neutron Source

Abstract Developing highly active and durable electrocatalysts for acidic oxygen evolution reaction remains a great challenge due to the sluggish kinetics of the four-electron transfer reaction and severe catalyst dissolution. Here we report an electrochemical lithium intercalation method to improve both the activity and stability of RuO 2 for acidic oxygen evolution reaction. The lithium intercalates into the lattice interstices of RuO 2 , donates electrons and distorts the local structure. Therefore, the Ru valence state is lowered with formation of stable Li-O-Ru local structure, and the Ru–O covalency is weakened, which suppresses the dissolution of Ru, resulting in greatly enhanced durability. Meanwhile, the inherent lattice strain results in the surface structural distortion of Li x RuO 2 and activates the dangling O atom near the Ru active site as a proton acceptor, which stabilizes the OOH* and dramatically enhances the activity. This work provides an effective strategy to develop highly efficient catalyst towards water splitting.

Sodium filling inside hard carbon pores demonstrates increasingly metallic character with increasing pore size.

Abstract Li-ion-conducting chloride solid electrolytes receive considerable attention due to their physicochemical characteristics such as high ionic conductivity, deformability and oxidative stability. However, the raw materials are expensive, and large-scale use of this class of inorganic superionic conductors seems unlikely. Here, a cost-effective chloride solid electrolyte, Li 2 ZrCl 6 , is reported. Its raw materials are several orders of magnitude cheaper than those for the state-of-the-art chloride solid electrolytes, but high ionic conductivity (0.81 mS cm –1 at room temperature), deformability, and compatibility with 4V-class cathodes are still simultaneously achieved in Li 2 ZrCl 6 . Moreover, Li 2 ZrCl 6 demonstrates a humidity tolerance with no sign of moisture uptake or conductivity degradation after exposure to an atmosphere with 5% relative humidity. By combining Li 2 ZrCl 6 with the Li-In anode and the single-crystal LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode, we report a room-temperature all-solid-state cell with a stable specific capacity of about 150 mAh g –1 for 200 cycles at 200 mA g –1 .

X-ray and neutron diffraction, Raman spectroscopy, complex impedance spectroscopy and electron microscopy were used to characterize the tetragonal <italic>vs.</italic> cubic phase stability in superionic conducting garnet-oxide electrolyte.

also enjoys facile solution synthesis with large scalability, excellent repeatability, and low cost.

Abstract Defect engineering is a strategy that is attracting widespread attention for the possibility of modifying battery active materials in order to improve the cycling stability of the electrodes. However, accurate investigation and quantification of the effect of the defects on the electrochemical energy storage performance of the cell are not trivial tasks. Herein, we report the quantification of vanadium-defective clusters (i.e., up to 5.7%) in the V 2 O 3 lattice via neutron and X-ray powder diffraction measurements, positron annihilation lifetime spectroscopy, and synchrotron-based X-ray analysis. When the vanadium-defective V 2 O 3 is employed as cathode active material in an aqueous Zn coin cell configuration, capacity retention of about 81% after 30,000 cycles at 5 A g −1 is achieved. Density functional theory calculations indicate that the vanadium-defective clusters can provide favorable sites for reversible Zn-ion storage. Moreover, the vanadium-defective clusters allow the storage of Zn ions in V 2 O 3 , which reduces the electrostatic interaction between the host material and the multivalent ions.

A fluorine-containing hydrophobic Lewis acid is employed as an effective dopant for PTAA to replace state-of-the-art Li-TFSI/<italic>t</italic>-BP in PSCs.

Research and processing development on satellite communications has strongly re-emerged in recent years. Following the prosperity of various wireless services provided by satellite communications, the security issue has raised growing concerns since the space information network is susceptible to be eavesdropped by illegal adversaries in such a large-scale wireless network. Recently, the physical-layer security (PLS) has emerged as an alternative security paradigm that explores the randomness of the wireless channel to achieve confidentiality and authentication. The success story of the PLS technique now spans a decade and thrives to provide a layer of defense in satellite communications. With this position, a comprehensive survey of satellite communications is conducted in this article with an emphasis on PLS. We first briefly introduce essential background and the view of the satellite Internet of Things (IoT), as well as discuss related research challenges faced by the emerging integrated network architecture. Then, we revisit the most popular satellite channel model influenced by many factors and list the commonly used secrecy performance metrics. Also, we provide an exhaustive review of state-of-the-art research activity on PLS in satellite communications, which we categorize by different architectures including land mobile satellite communication networks, hybrid satellite-terrestrial relay networks, and satellite-terrestrial integrated networks. In addition, a number of open research problems are identified as possible future research directions.

The elastic storage and release of mechanical energy has been key to many developments throughout the history of mankind. Resilience, absent hysteresis, has been an elusive goal to achieve, particularly at large deformations. Using a low-crosslink-density polyacrylamide hydrogel at 96% water content having hyperbranched silica nanoparticles (HBSPs) as the major junction points, a hysteresis-free material is realized. The fatigue-free characteristic of these composite hydrogels is evidenced by the invariance of the stress-strain curves at strain ratios of 4, even after 5000 cycles. At a strain ratio of 7, only a 1.3% hysteresis is observed. A markedly increased strain-ratio-at-break of 11.5 is observed. The unique attributes of these resilient hydrogels are manifested in the high-fidelity detection of dynamic deformations under cyclic loading over a broad range of frequencies, difficult to achieve with other materials.

Abstract Stretchable conductive hydrogels with simultaneous high mechanical strength/modulus, and ultrahigh, stable electrical conductivity are ideal for applications in soft robots, artificial skin, and bioelectronics, but to date, they are still very challenging to fabricate. Herein, sandwich‐structured hybrid hydrogels based on layers of aramid nanofibers (ANFs) reinforced polyvinyl alcohol (PVA) hydrogels and a layer of silver nanowires (AgNWs)/PVA are fabricated by electrospinning combined with vacuum‐assisted filtration. The hybrid ANF‐PVA hydrogels exhibit excellent mechanical properties with the tensile modulus of 10.7–15.4 MPa, tensile strength of 3.3–5.5 MPa, and fracture energy up to 5.7 kJ m −2 , primarily attributed to the strong hydrogen bonding interactions between PVA and ANFs and in‐plane alignment of the fibrous structure. Rational design of heterogeneous structure endows the hydrogels with ultrahigh apparent electrical conductivity of 1.66 × 10 4 S m −1 , among the highest electrical conductivities ever reported so far for conductive hydrogels. More importantly, this ultrahigh conductivity remains constant upon a broad range of applied strains from 0–90% and over 500 stretching cycles. Furthermore, the hydrogels exhibit excellent Joule heating and electromagnetic interference shielding performances due to the ultrahigh electrical conductivity. These mechanically strong, hybrid hydrogels with ultrahigh and strain‐invariant electrical conductivity represent great promises for many important applications such as flexible electronics.

Understanding the interfacial hydrogen evolution reaction (HER) is crucial to regulate the electrochemical behavior in aqueous zinc batteries. However, the mechanism of HER related to solvation chemistry remains elusive, especially the time-dependent dynamic evolution of the hydrogen bond (H-bond) under an electric field. Herein, we combine in situ spectroscopy with molecular dynamics simulation to unravel the dynamic evolution of the interfacial solvation structure. We find two critical change processes involving Zn-electroplating/stripping, including the initial electric double layer establishment to form an H2O-rich interface (abrupt change) and the subsequent dynamic evolution of an H-bond (gradual change). Moreover, the number of H-bonds increases, and their strength weakens in comparison with the bulk electrolyte under bias potential during Zn2+ desolvation, forming a diluted interface, resulting in massive hydrogen production. On the contrary, a concentrated interface (H-bond number decreases and strength enhances) is formed and produces a small amount of hydrogen during Zn2+ solvation. The insights on the above results contribute to deciphering the H-bond evolution with competition/corrosion HER during Zn-electroplating/stripping and clarifying the essence of electrochemical window widened and HER suppression by high concentration. This work presents a new strategy for aqueous electrolyte regulation by benchmarking the abrupt change of the interfacial state under an electric field as a zinc performance-enhancement criterion.

Air sensitivity remains a substantial barrier to the commercialization of sodium (Na)-layered oxides (NLOs). This problem has puzzled the community for decades because of the complexity of interactions between air components and their impact on both bulk and surfaces of NLOs. We show here that water vapor plays a pivotal role in initiating destructive acid and oxidative degradations of NLOs only when coupled with carbon dioxide or oxygen, respectively. Quantification analysis revealed that reducing the defined cation competition coefficient (η), which integrates the effects of ionic potential and sodium content, and increasing the particle size can enhance the resistance to acid attack, whereas using high-potential redox couples can eliminate oxidative degradation. These findings elucidate the underlying air deterioration mechanisms and rationalize the design of air-stable NLOs.

The high-voltage doped spinel oxides LiMn1.5Ni0.5–xMxO4 (M = Cr, Fe, and Ga; 0 ≤ x ≤ 0.08) synthesized at 900 °C have been investigated systematically before and after postannealing at 700 °C. Neutron diffraction studies reveal that the cation-ordered domain size tends to increase upon annealing at 700 °C. Time-of-flight secondary-ion mass spectroscopy data reveal that the dopant cations M = Cr, Fe, and Ga segregate preferentially to the surface, resulting in a more stable cathode–electrolyte interface and superior cyclability at both room temperature and 55 °C with conventional electrolytes. The doping with Cr and Fe stabilizes the structure with a significant disordering of the cations in the 16d sites even after postannealing at 700 °C, resulting in high rate capability due to low charge-transfer resistance and polarization loss. In contrast, the Ga-doped and undoped LiMn1.5Ni0.5O4 samples experience an increase in cation ordering upon postannealing at 700 °C, resulting in degradation in the rate capability due to an increase in the charge-transfer resistance and polarization loss.

Sodium-ion batteries have garnered unprecedented attention as an electrochemical energy storage technology, but it remains challenging to design high-energy-density cathode materials with low structural strain during the dynamic (de)sodiation processes. Herein, we report a P2-layered lithium dual-site-substituted Na0.7Li0.03[Mg0.15Li0.07Mn0.75]O2 (NMLMO) cathode material, in which Li ions occupy both transition-metal (TM) and alkali-metal (AM) sites. The combination of theoretical calculations and experimental characterizations reveals that LiTM creates Na–O–Li electronic configurations to boost the capacity derived from the oxygen anionic redox, while LiAM serves as LiO6 prismatic pillars to stabilize the layered structure through suppressing the detrimental phase transitions. As a result, NMLMO delivers a high specific capacity of 266 mAh g–1 and simultaneously exhibits the nearly zero-strain characteristic within a wide voltage range of 1.5–4.6 V. Our findings highlight the effective way of dual-site substitution to break the capacity–stability trade-off in cathode materials for advanced rechargeable batteries.

Defect engineering on electrode materials is considered an effective approach to improve the electrochemical performance of batteries since the presence of a variety of defects with different dimensions may promote ion diffusion and provide extra storage sites. However, manipulating defects and obtaining an in-depth understanding of their role in electrode materials remain challenging. Here, we deliberately introduce a considerable number of twin boundaries into spinel cathodes by adjusting the synthesis conditions. Through high-resolution scanning transmission electron microscopy and neutron diffraction, the detailed structures of the twin boundary defects are clarified, and the formation of twin boundary defects is attributed to agminated lithium atoms occupying the Mn sites around the twin boundary. In combination with electrochemical experiments and first-principles calculations, we demonstrate that the presence of twin boundaries in the spinel cathode enables fast lithium-ion diffusion, leading to excellent fast charging performance, namely, 75% and 58% capacity retention at 5 C and 10 C, respectively. These findings demonstrate a simple and effective approach for fabricating fast-charging cathodes through the use of defect engineering.

Abstract The rational design and control of electrocatalysts at single‐atomic sites could enable unprecedented atomic utilization and catalytic properties, yet it remains challenging in multimetallic alloys. Herein, the first example of isolated Rh atoms on ordered PtBi nanoplates (PtBi‐Rh 1 ) by atomic galvanic replacement, and their subsequent transformation into a tensile‐strained Pt–Rh single‐atom alloy (PtBi@PtRh 1 ) via electrochemical dealloying are presented. Benefiting from the Rh 1 ‐tailored Pt (110) surface with tensile strain, the PtBi@PtRh 1 nanoplates exhibit record‐high and all‐round superior electrocatalytic performance including activity, selectivity, stability, and anti‐poisoning ability toward ethanol oxidation in alkaline electrolytes. Density functional theory calculations reveal the synergism between effective Rh 1 and tensile strain in boosting the adsorption of ethanol and key surface intermediates and the CC bond cleavage of the intermediates. The facile synthesis of the tensile‐strained single‐atom alloy provides a novel strategy to construct model nanostructures, accelerating the development of highly efficient electrocatalysts.

High temperature electrochemical devices, such as solid oxide fuel cells (SOFCs), will play a vital role in the future green and sustainable energy industries due to direct utilization of carbon-based fuels and their ability to couple with renewable energies to convert by-products into valuable fuels using solid oxide electrolysis cells (SOECs).

Using neutron reflectivity, self-stratification in a model P3HT/PCBM blend is observed. The as-spun and solvent-annealed films show a depletion of PCBM near the top surface and enrichment of PCBM at the substrate (see figure). Depletion of PCBM at the cathode interface in a photovoltaic device could act as a barrier to efficient electron extraction. On thermal annealing, the PCBM depleted region is eliminated; an effect that partially explains the improvement of P3HT/PCBM devices on thermal annealing.

The practical implementation of Co-free, LiNiO2-derived cathodes has been prohibited by their poor cycle life and thermal stability, resulting from the structural instability, phase transformations, reactive surfaces, and chemomechanical breakdown. With the hierarchical distribution of Mg/Ti dual dopants in LiNiO2, we report a Co-free layered oxide that exhibits enhanced bulk and surface stability. Ti shows a gradient distribution and is enriched at the surface, whereas Mg distributes homogeneously throughout the primary particles. The resulting Mg/Ti codoped LiNiO2 delivers a material-level specific energy of ∼780 W h/kg at C/10 with 96% retention after 50 cycles. The specific energy reaches ∼680 W h/kg at 1C with 77% retention after 300 cycles. Furthermore, the Mg/Ti dual dopants improve the rate capability, thermal stability, and self-discharge resistance of LiNiO2. Our synchrotron X-ray, electron, and electrochemical diagnostics reveal that the Mg/Ti dual dopants mitigate phase transformations, reduce nickel dissolution, and stabilize the cathode–electrolyte interface, thus leading to the favorable battery performance in lithium metal and graphite cells. The present study suggests that engineering the dopant distribution in cathodes may provide an effective path toward lower cost, safer, and higher energy density Co-free lithium batteries.

Abstract Reversible solid-state hydrogen storage of magnesium hydride, traditionally driven by external heating, is constrained by massive energy input and low systematic energy density. Herein, a single phase of Mg 2 Ni(Cu) alloy is designed via atomic reconstruction to achieve the ideal integration of photothermal and catalytic effects for stable solar-driven hydrogen storage of MgH 2 . With the intra/inter-band transitions of Mg 2 Ni(Cu) and its hydrogenated state, over 85% absorption in the entire spectrum is achieved, resulting in the temperature up to 261.8 °C under 2.6 W cm −2 . Moreover, the hydrogen storage reaction of Mg 2 Ni(Cu) is thermodynamically and kinetically favored, and the imbalanced distribution of the light-induced hot electrons within CuNi and Mg 2 Ni(Cu) facilitates the weakening of Mg-H bonds of MgH 2 , enhancing the “hydrogen pump” effect of Mg 2 Ni(Cu)/Mg 2 Ni(Cu)H 4 . The reversible generation of Mg 2 Ni(Cu) upon repeated dehydrogenation process enables the continuous integration of photothermal and catalytic roles stably, ensuring the direct action of localized heat on the catalytic sites without any heat loss, thereby achieving a 6.1 wt.% H 2 reversible capacity with 95% retention under 3.5 W cm −2 .