Quasi-Solid-State Ion-Conducting Arrays Composite Electrolytes with Fast Ion Transport Vertical-Aligned Interfaces for All-Weather Practical Lithium-Metal Batteries

The rapid improvement in the gel polymer electrolytes (GPEs) with high ionic conductivity brought it closer to practical applications in solid-state Li-metal batteries. The combination of solvent and polymer enables quasi-liquid fast ion transport in the GPEs. However, different ion transport capacity between solvent and polymer will cause local nonuniform Li$^+$ distribution, leading to severe dendrite growth. In addition, the poor thermal stability of the solvent also limits the operating-temperature window of the electrolytes. Optimizing the ion transport environment and enhancing the thermal stability are two major challenges that hinder the application of GPEs. Here, a strategy by introducing ion-conducting arrays (ICA) is created by vertical-aligned montmorillonite into GPE. Rapid ion transport on the ICA was demonstrated by $^6$Li solid-state nuclear magnetic resonance and synchrotron X-ray diffraction, combined with computer simulations to visualize the transport process. Compared with conventional randomly dispersed fillers, ICA provides continuous interfaces to regulate the ion transport environment and enhances the tolerance of GPEs to extreme temperatures. Therefore, GPE/ICA exhibits high room-temperature ionic conductivity (1.08 mS cm$^{−1}$) and long-term stable Li deposition/stripping cycles (> 1000 h). As a final proof, Li||GPE/ICA||LiFePO$_4$ cells exhibit excellent cycle performance at wide temperature range (from 0 to 60 °C), which shows a promising path toward all-weather practical solid-state batteries

Phase boundary engineering of metal-organic-framework-derived carbonaceous nickel selenides for sodium-ion batteries

Abstract: Sodium-ion batteries (SIBs) are promising power sources due to the low cost and abundance of battery-grade sodium resources, while practical SIBs suffer from intrinsically sluggish diffusion kinetics and severe volume changes of electrode materials. Metal-organic framework (MOFs) derived carbonaceous metal compound offer promising applications in electrode materials due to their tailorable composition, nanostructure, chemical and physical properties. Here, we fabricated hierarchical MOF-derived carbonaceous nickel selenides with bi-phase composition for enhanced sodium storage capability. As MOF formation time increases, the pyrolyzed and selenized products gradually transform from a single-phase Ni3Se4 into bi-phase NiSex then single-phase NiSe2, with concomitant morphological evolution from solid spheres into hierarchical urchin-like yolk-shell structures. As SIBs anodes, bi-phase NiSex@C/CNT-10h (10 h of hydrothermal synthesis time) exhibits a high specific capacity of 387.1 mAh/g at 0.1 A/g, long cycling stability of 306.3 mAh/g at a moderately high current density of 1 A/g after 2,000 cycles. Computational simulation further proves the lattice mismatch at the phase boundary facilitates more interstitial space for sodium storage. Our understanding of the phase boundary engineering of transformed MOFs and their morphological evolution is conducive to fabricate novel composites/hybrids for applications in batteries, catalysis, sensors, and environmental remediation

Conversion mechanism of NiCo2Se4 nanotube sphere anodes for potassium-ion batteries

Given the abundance of potassium resources, potassium-ion batteries are considered a low-cost alternative to lithium-ion types. However, their electrochemical performance remains rather unsatisfactory because potassium ions have sluggish kinetics and large ionic radius. In this study, NiCo2Se4 nanotube spheres are synthesized as efficient potassium storage hosts via a facile two-step hydrothermal process. The rationally designed electrode has various ameliorating morphological and functional features, including the following: (i) A hollow structure allows for relief of the volume expansion while offering an excellent electrochemical reactivity to accelerate the conversion kinetics; (ii) a high electrical conductivity for enhanced electron transfer; and (iii) myriad vacancies to supply active sites for electrochemical reactions. As such, the electrode delivers an initial reversible capacity of 458.1 mAh g−1 and retains 346.6 mAh g−1 after 300 cycles at 0.03 A g−1. The electrode sustains a high capacity of 101.4 mAh g−1 even at a high current density of 5 A g−1 and outperforms the majority of state-of-the-art anodes in terms of both cyclic capacity and rate capability, especially at above 1.0 A g−1. This study not only proves bimetallic selenides are promising candidates for potassium storage devices but also offers new insight into the rational design of electrode materials for high-rate potassium-ion batteries

Changes in Environmental Awareness and its Connection to Local Environmental Management in Water Conservation Zones: The Case of Beijing, China

This paper aims at investigating the change over time in the environmental awareness in rural Chinese communities and its correlation with environmental management measures implemented at the local level. We identify three main components of awareness, namely: perception, behavior, and attitude toward environmental management measures. Data were collected from two surveys in three villages in northern China in 2006 and 2015 that interviewed 125 and 129 respondents, respectively, and were analyzed employing an Analytic Hierarchy Process (AHP) approach. The results discussed in the paper show that environmental awareness increased between 2006–2015, and was mainly manifested in better environmental behavior and understanding of environmental status due an improvement in rural infrastructure and a greater amount of information provided to rural residents about the environment. Place of residence had a considerable influence on respondents’ environmental awareness: residents in eco-villages had a higher environmental awareness than those living in common agricultural villages. This appears to indicate a positive nexus between the comprehensiveness of environmental management measures implemented locally, and environmental awareness. Also, the universality of environment issues reduced the importance of socioeconomic and demographic factors in determining the degree of environmental awareness. However, more attention should be paid to villagers’ external behavior and inner feelings, such as their attitude to governmental management policies. These findings yield important policy implications that are relevant to the promotion of environmental awareness in China’s rural communities, and the adoption of more effective environmental management measures

One-dimensional hierarchical structures composed of novel metal oxide nanosheets on a carbon nanotube backbone and their lithium-storage properties

Some facile solution methods are developed to directly grow anatase TiO2 nanosheets with exposed (001) facets and SnO2 nanosheets onto a carbon nanotube backbone for the first time. TiO2 nanosheets can also be grown on SnO2@CNT coaxial nanocables. An electrochemical investigation shows that these unique one-dimensional hierarchical nanostructures exhibit significantly enhanced lithium-storage properties under different testing conditions by comparison to the pure metal oxide counterparts, and evidently suggests that improved electrochemical properties of TiO2 and SnO2 can be achieved through proper design of the nanostructure and chemical composition

A DFT Study on the Activity Origin of Fe−N−C Sites for Oxygen Reduction Reaction

Iron-nitrogen-carbon materials have been known as the most promising non-noble metal catalyst for proton-exchange membrane fuel cells (PEMFCs), but the genuine active sites for oxygen reduction reaction (ORR) are still arguable. Herein, by the thorough density functional theory investigations, we unravel that the planar Fe2N6 site exhibits excellent ORR catalytic activity over both FeN3 and FeN4 sites, and the potential-determining step is determined to be the *OH hydrogenation step with an overpotential of 0.415 V. The ORR activity of Fe2N6 site originates from the low spin magnetic moment (1.11 μB), which leads to high antibonding states and low d-band center of the Fe center, further leads to weak binding strength of *OH species. The density of FeN4 sites only has little influence on the ORR activity owing to the similar interaction between active site and intermediates in ORR. Our research sheds light on the activity origin of iron-nitrogen-carbon materials for ORR

CNTs@SnO2@carbon coaxial nanocables with high mass fraction of SnO2 for improved lithium storage

The nanoCable Guy: Carbon nanotubes (CNTs)@SnO2@carbon have been fabricated using a simple procedure. The material exhibits greatly enhanced lithium-storage capacities and excellent cycling performance over extended cycles owing to their unique structural configuration and chemical composition

A Joint Estimation Method of the Channel Phase Error and Motion Error for Distributed SAR on a Single Airborne Platform Based on a Time-Domain Correlation Method

Distributed synthetic aperture radar (SAR) is a system in which transmitting or receiving arrays are distributed on multiple platforms or at different locations on one platform. Distributed SAR can be used for high-resolution wide-swath (HRWS) imaging. The typical platform used for distributed SAR is a satellite constellation, which has long baselines and an ideal trajectory. Instead of satellite constellations, this paper focuses on distributed SAR on a single airborne platform, for which the channel error and motion error are coupled. Furthermore, the traditional channel error estimation methods are invalid. Thus, based on the time-domain correlation method (TDCM), this article proposes a joint estimation method of the channel phase error and motion error for the distributed SAR on a single airborne platform. Firstly, a channel error and motion error coupled phase error model of the distributed SAR is constructed. A joint estimation method of the channel phase error and motion error is then proposed. Finally, a simulation and real data processing are provided to demonstrate the effectiveness of the proposed method

Glucose-assisted growth of MoS2 nanosheets on CNT backbone for improved lithium storage properties

Pour a little sugar on it: A simple glucose-assisted hydrothermal method to directly grow MoS2 nanosheets (NSs) on the CNT backbone is reported. Several features of these CNT@MoS2 structures, including high MoS2 content in the hybrid structure, large surface area provided by the nanosheet structure, and a conducting network of amorphous carbon and CNT backbone, lead to significantly improved lithium storage properties