Lithium–gas batteries (LGBs) have garnered significant attention due to their impressive high‐energy densities and unique gas conversion capability. Nevertheless, the practical application of LGBs faces substantial challenges, including sluggish gas conversion kinetics inducing in low‐rate performance and high overpotential, along with limited electrochemical reversibility leading to poor cycle life. The imperative task is to develop gas electrodes with remarkable catalytic activity, abundant active sites, and exceptional electrochemical stability. Electrospinning, a versatile and well‐established technique for fabricating fibrous nanomaterials, has been extensively explored in LGB applications. In this work, we emphasize the critical structure–property for ideal gas electrodes and summarize the advancement of employing electrospun nanofibers (NFs) for performance enhancement in LGBs. Beyond elucidating the fundamental principles of LGBs and the electrospinning technique, we focus on the systematic design of electrospun NF‐based gas electrodes regarding optimal structural fabrication, catalyst handling and activation, and catalytic site optimization, as well as considerations for large‐scale implementation. The demonstrated principles and regulations for electrode design are expected to inspire broad applications in catalyst‐based energy applications.

Functionalization by noble metal catalysts and the construction of heterojunctions are two effective methods to enhance the gas sensing performance of metal oxide-based sensors. In this work, we adopt the porous ZIF-8 as a catalyst substrate to encapsulate the ultra-small Pt nanoparticles. The Pt/ZnO-In2O3 hollow nanofibers derived from Pt/ZIF-8 were prepared by a facile electrospinning method. The 25PtZI HNFs sensor possessed a response value of 48.3 to 100 ppm HCHO, 2.7 times higher than the pristine In2O3, along with rapid response/recovery time (5/22 s), and lower theoretical detection limit (74.6 ppb). The improved sensing properties can be attributed to the synergistic effects of electron sensitization effects and catalytic effects of Pt nanoparticles, and the high surface O− absorbing capability of heterojunctions. The present study paves a new way to design high performance formaldehyde gas sensors in practical application.

A rapid and accurate monitoring of hazardous formaldehyde (HCHO) gas is extremely essential for health protection. However, the high-power consumption and humidity interference still hinder the application of HCHO gas sensors. Hence, zeolitic imidazolate framework-8 (ZIF-8)-loaded Pt-NiO/In2O3 hollow nanofibers (ZPNiIn HNFs) were designed via the electrospinning technique followed by hydrothermal treatment, aiming to enable a synergistic advantage of the surface modification and the construction of a p-n heterostructure to improve the sensing performance of the HCHO gas sensor. The ZPNiIn HNF sensor has a response value of 52.8 to 100 ppm HCHO, a nearly 4-fold enhancement over a pristine In2O3 sensor, at a moderately low temperature of 180 °C, along with rapid response/recovery speed (8/17 s) and excellent humidity tolerance. These enhanced sensing properties can be attributed to the Pt catalysts boosting the catalytic activity, the p-n heterojunctions facilitating the chemical reaction, and the appropriate ZIF-8 loading providing a hydrophobic surface. Our research presents an effective sensing material design strategy for inspiring the development of cost-effective sensors for the accurate detection of indoor HCHO hazardous gas.

Safety issues triggered by battery thermal runaway have become the most crucial obstacle to the future development of the high-energy-density energy storage systems. As hydrogen (H2) will be inevitably generated along with heat release caused by the side reactions in the early stages of battery thermal runaway, rapid monitoring of trace H2 is considered as an effective measure enabling the battery safety early warning. Herein, to develop highperformance H2 sensing materials to monitor of low-concentration H2 leakage, ZIF-8 loaded Ag/ZnO electrospun nanofibers (ZAZ NFs) were designed by electrospinning and self-sacrificial template methods. Benefiting from all the enrichment and sieving effects of ZIF-8 shell, the catalytic and sensitization effects of Ag and abundant active sites provided by Ag and ZIF-8 loading, the ZAZ sensor enables ppb-level limit of detection toward H2, fast response (9 s), high selectivity and excellent humidity resistance. Furthermore, this ZAZ sensor can also realize the safety early warning (67.79 s before battery bulge) for practical pouch lithium cells, highlighting its great application potential in future advanced battery safety management system.

Gas sensors based on semiconductor metal oxides are identified as a highly promising candidate for toxic gas detection, yet they still suffer from high operating temperature due to low surface activity at low temperature. To address this issue, we present an elaborate design for the homogeneous functionalization of ZIF-L(Co) derived cobalt (Co) catalysts into hollow In2O3 frameworks, aiming to highly activate the redox capacity and catalytic efficacy of the In2O3 sensor to HCHO gas. Benefiting from the Co catalysts doping boosts the catalytic activity and generates abundant oxygen vacancies, the optimized 1 wt% Co-doped In2O3 HNFs sensor exhibits a high response of 40.4 toward 100 ppm HCHO at a moderately low temperature of 180 ℃, which is 4 times higher than that of pristine In2O3 HNFs. Moreover, 1 wt% Co-doped In2O3 HNFs sensor has virtues of high selectivity and excellent long-term stability for HCHO sensing. This study highlights the important influence of Co catalyst on the modulation of surface active sites of metal oxides-based sensors, inspiring the development of cost-effective sensors for indoor hazardous gas monitoring.

Solid-state lithium batteries (SSLBs) have been broadly accepted as a promising candidate for the next generation lithium-ion batteries (LIBs) with high energy density, long duration, and high safety. The intrinsic non-flammable nature and electrochemical/thermal/mechanical stability of solid electrolytes are expected to fundamentally solve the safety problems of conventional LIBs. However, thermal degradation and thermal runaway could also happen in SSLBs. For example, the large interfacial resistance between solid electrolytes and electrodes could aggravate the joule heat generation; the anisotropic thermal diffusion could trigger the uneven temperature distribution and formation of hotspots further leading to lithium dendrite growth. Considerable research efforts have been devoted to exploring solid electrolytes with outstanding performance and harmonizing interfacial incompatibility in the past decades. There have been fewer comprehensive reports investigating the thermal reaction process, thermal degradation, and thermal runaway of SSLBs. This review seeks to highlight advanced thermal-related analysis techniques for SSLBs, by focusing particularly on multiscale and multidimensional thermal-related characterization, thermal monitoring techniques such as sensors, thermal experimental techniques imitating the abuse operating condition, and thermal-related advanced simulations. Insightful perspectives are proposed to bridge fundamental studies to technological relevance for better understanding and performance optimization of SSLBs.

As a potential zero-carbon fuel for internal combustion engine to mitigate the greenhouse gas emission, ammonia's unique flash boiling spray behaviors have not been well understood. In this study, the macroscopic and the microscopic characteristics of the liquid ammonia spray at the flare and transition flash boiling regions were experimentally investigated under different pressure ratios (RP, the ambient over the saturated pressure) and ambient temperatures. The spray macroscopic morphologies captured from the high-speed camera in the flare flash boiling region (RP = 0.47) show that the spray expands significantly in radial direction while that in the transition flash boiling region (0.47 < RP = 1.06) is more contracted in the penetration direction. Additionally, in flare flash boiling region, spray tip penetration and velocity increases generally with the increase of RP, while that in the transition flash boiling region in versus. Furthermore, the microscopic droplet statistics clearly demonstrate show that the most probable droplet diameter moves to a larger value with the increase of RP. The peak probability of droplet size and the droplet number density decreases at larger RP cases, resulting in a more uniformly distributed droplet sizes and an increased Sauter Mean Diameter. Finally, the ambient temperature show limited influence on the macroscopic spray penetration behaviors or the microscopic droplet size distribution, but evaporation is significantly enhanced since at highest ambient temperature, there are minimized droplet number density in some of the test locations.

Alkaline Ni-Zn batteries are gaining more and more attention because of their safety, environmental friendliness, low cost and excellent performance. However, the volume and structure of the cathode changes during the charging and discharging process, resulting in particle flaking and structural rupture during the cyclic charging and discharging process, thus reducing their cyclic stability and limiting wide application. Herein, NiCo Layered double hydroxides (LDHs)clay materials with a low crystallinity multilayer nanosheet structure are prepared by glucose intercalation as cathode materials for alkaline Ni-Zn batteries. Expanded NiCo LDH layer spacing through glucose intercalation reduces interlayer peeling and collapse, accelerates interlayer diffusion of ions, and thus improves electron transport performance. NiCo LDH-G1.5 electrode material provides a specific capacity of 224 mAh g-1 and a capacity retention rate of 76% at a current density of 40 A g-1, 2000 cycles to maintain 86% of maximum capacity. Alkaline NiCo LDH-G1.5//Zn battery, a specific capacity of 180 mAh g-1 can be achieved at a high current density of 20 A g-1 and still maintain 76% of their maximum capacity after 2000 cycles, a maximum energy density of 364 Wh kg-1 and a maximum power density of 54 kW kg-1. This work provides a viable cathode for the development of high specific capacity and stable alkaline Ni-Zn batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) would be a promising candidate for the next-generation bat-teries due to the utilization of energy-dense electrodes and the non-flammable oxide solid-state electrolytes (SSEs), but still face great challenges such as low ionic conductivity of SSEs, poor interfacial contact and lithium (Li) dendrite propagation. Herein, we regulated the crystallinity degrees of the large-scale-fabricated Li1.5Al0.5-Ge-1.5(PO4)(3) (LAGP) SSEs and explored the critical role of crystallinity optimization in reinforcing the basic properties of LAGP, developing a fundamental explanation for the inherent relation between the crystallinity and the performance of ASSLSBs. Benefiting from the optimized crystallinity (similar to 99.9 %), the large-scale-fabricated LAGP not only realizes the low surface roughness and high ionic conductivity (2.11 x 10(-4) S cm(-1)) to improve interfacial contact and reduce resistance in ASSLSBs, but also possesses the dense internal structure with low porosity (1.49 %) to physically resist dendritic propagation and penetration. Consequently, the ASSLSB with the optimized LAGP delivers a high reversible capacity of 647.9 mAh/g even after 150 cycles at 0.1 C. This work confirms the significance of crystallinity in understanding the working mechanisms of oxide SSEs and developing future high-performance ASSLSBs.

Development of high-loading and high-energy-density lithium-sulfur (Li-S) batteries has aroused increasing research interests recently. However, the performance of a conventional two-dimensional Al foil current collector is limited by its smooth/nonporous surface and poor flexibility, which is unfavorable for the achievement of high sulfur loading and sufficient polysulfide adsorption. Hence, a three-dimensional porous Fe-doped polypyrrole aerogel (FPA) is developed by a simple and scalable strategy combing the solution reaction with the freeze-drying technique, aiming at acting as the current collector of cathode to address these issues in Li-S batteries. This FPA possesses a conductive porous network structure with high elasticity and abundant Fe dopants, which can not only buffer the large volume change of sulfur and ensure fast ion/electron transfer, but also effectively anchor the polysulfides and lower the negative polarization effect during cycling. As a result, the FPA@S cathode delivers a high initial capacity of 1196.7 mAh g(-1) at 0.2 C and a retained capacity of 829.5 mAh g(-1) after 200 cycles, with stabilized Coulombic efficiency and excellent rate performance. This FPA@S cathode also achieves a high cell-level gravimetric energy density of 199.7 Wh kg(cell)(-1) even under a high sulfur-loading (8.57 mg cm(-2)) and low electrolyte/sulfur ratio (6 mL g(-1)), demonstrating its practical potential in future advanced high-energy battery systems. (C) 2021 Elsevier B.V. All rights reserved.

Resistive gas sensors are considered promising candidates for gas detection, benefiting from their small size, ease of fabrication and operation convenience. The development history, performance index, device type and common host materials (metal oxide semiconductors, conductive polymers, carbon-based materials and transition metal dichalcogenides) of resistive gas sensors are firstly reviewed. This review systematically summarizes the functions, functional mechanisms, features and applications of seven kinds of guest materials (noble metals, metal heteroatoms, metal oxides, metal-organic frameworks, transition metal dichalcogenides, polymers, and multiple guest materials) used for the modification and optimization of the host materials. The introduction of guest materials enables synergistic effects and complementary advantages, introduces catalytic sites, constructs heterojunctions, promotes charge transfer, improves carrier transport, or introduces protective/sieving/enrichment layers, thereby effectively improving the sensitivity, selectivity and stability of the gas sensors. The perspectives and challenges regarding the host-guest hybrid materials-based gas sensors are also discussed.

In this work, a facile strategy to improve the formaldehyde (HCHO) sensing performance via introducing A-site cation deficiency of LaFeO3 hollow oxides is reported. One-dimensional LaxFeO3 hollow nanofibers (LxFO HNFs, x = 1.0, 0.9, 0.8, 0.7, and 0.6) were prepared through electrospinning technique and subsequent calcination treatment. Benefiting from the hollow nanostructures and the existed A-site cation deficiency in LxFO HNFs, all the rapid charge transfer, abundant oxygen vacancies, and chemisorbed active sites could be achieved. Among all these LxFO HNFs sensors, the non-stoichiometric L0.7FO HNFs sensor delivered a high response value of 20.4 towards 100 ppm HCHO at 180 degrees C, which is over 3-fold higher than that of stoichiometric L1.0FO HNFs (6.3). Moreover, L0.7FO HNFs sensor has virtues of rapid response/recovery speed (23 /13 s), high selectivity, and good long-term stability toward HCHO. The smart HCHO detection device assembled with the L0.7FO HNFs gas sensor also enabled real-time and visible HCHO monitoring, highlighting its great potential application in the smart detection of hazardous gases.

Rapid detection of hazardous trace gas is critical to protect humans from health threats. The current gas sensors, however, suffer from insufficient sensitivity and selectivity, which limits their use in the application of real-time monitoring for low concentration gas. Herein, a versatile “in situ enrichment amplification” (IEA) strategy is proposed, aiming to integrate the in situ formed adsorption-functional material for target gas enrichment and the backbone sensor-functional material for gas response. The IEA-based gas sensors exhibit high sensitivity and selectivity toward the detection of HCHO gas. The calculated detection limit of the IEA sensor to HCHO gas is 63 ppb, much lower than that of the conventional HCHO sensor (183 ppb). Furthermore, a wireless cloud HCHO detection system is developed to achieve sustainable remote monitoring of the HCHO gas. Application of this IEA strategy to other metal oxide sensing materials generates similarly successful results.

With the increasing popularity of battery technology, the safety problems caused by the thermal runaway of batteries have been paid more attention. Detecting the gases released from battery thermal runaway by gas sensors is one of the effective strategies to realize the early safety warning of batteries. The inducing factors of battery thermal runaway as well as the types and mechanisms of the gases generated at each reaction stage are first reviewed. According to the amount and starting time of gas release, five gases suitable for early detection of battery thermal runaway are mainly introduced, including hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), ethylene (C2H4), and methane (CH4). The application prospects of various gas-sensing technologies in the detection and early warning of battery thermal runaway are further evaluated. Benefiting from the superiorities of small size, high sensitivity, and stable performance, the resistive gas sensors are considered as promising candidates in this field, and their sensing mechanisms are also described in this review. In addition, the applicability and optimization strategies of gas sensors for the detection and early warning of battery thermal runaway are further reviewed systematically, on the basis of various aspects including sensing material, material design, sensing performance, etc. Finally, the potential directions and key points for the future development of gas sensors in the detection and early warning of battery thermal runaway are proposed.

Using inorganic fibrous membranes as protective layers has yielded success in suppressing dendrite growth. However, conventional fibrous membranes usually have large voids and low affinity for Li, promoting inhomogeneous charge distribution and allowing some dendrites to grow. Herein, we introduce a highly aligned TiO2/ SiO2 (A-TS) electrospun nanofiber membrane as a protective layer for the Li metal anode. The A-TS membrane is fabricated by a custom-made electrospinning system with an automatic fiber alignment collector that allows control of the fibers' orientation. At the scale of the individual fibers, their high binding energies with Li can attract more "dead" Li by reacting with the SiO2 component of the composite, avoiding uncontrollable deposition on the metal anode. At the membrane scale, these highly ordered structures achieve homogeneous contact and charge distribution on the Li metal surface, leaving no vulnerable areas to nucleate dendrite formation. Additionally, the excellent mechanical and thermal stability properties of the A-TS membrane prevent any potential puncturing by dendrites or thermal runaway in a battery. Hence, an A-TS@Li anode exhibits stable cycling performance when used in both Li-S and Li-NCM811 batteries, highlighting significant reference values for the future design and development of high-energy-density metal-based battery systems.

Oxide solid-state electrolytes (SSEs) are appealing as the potential substitute for conventional liquid electrolyte/separator system in lithium-sulfur batteries (LSBs). However, the poor ionic conductivity severely limits the large-scale applications of oxide SSEs in LSBs. The crystallinity of oxide SSEs is closely related to their relative density, intrinsic defects and impurities in pellets, hence playing a vital role in the ionic conductivity as well as the internal impedance and reaction kinetics of batteries. To explore the influence of the crystallinity of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) oxide SSEs on the performance of all-solid-state LSBs (ASSLSBs), LAGP SSEs with four different crystallinity degrees are designed by regulating their preparation temperature. As a result, the LAGP with optimized crystallinity realizes the high ionic conductivity of 2.11 × 10 -4 S cm -1 , and enables the reduced internal impedance and enhanced reaction kinetics in ASSLSB, consequently delivering a high reversible capacity of 647.9 mAh g −1 even after 150 cycles at 0.1 C. The current work confirms that the crystallinity optimization is a feasible strategy to prepare better LAGP SSEs for developing future high-performance ASSLSBs.

With a series of widespread applications, resistive gas sensors are considered to be promising candidates for gas detection, benefiting from their small size, ease-of-fabrication, low power consumption and outstanding maintenance properties. One-dimensional (1-D) nanomaterials, which have large specific surface areas, abundant exposed active sites and high length-to-diameter ratios, enable fast charge transfers and gas-sensitive reactions. They can also significantly enhance the sensitivity and response speed of resistive gas sensors. The features and sensing mechanism of current resistive gas sensors and the potential advantages of 1-D nanomaterials in resistive gas sensors are firstly reviewed. This review systematically summarizes the design and optimization strategies of 1-D nanomaterials for high-performance resistive gas sensors, including doping, heterostructures and composites. Based on the monitoring requirements of various characteristic gases, the available applications of this type of gas sensors are also classified and reviewed in the three categories of environment, safety and health. The direction and priorities for the future development of resistive gas sensors are laid out.