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Li metal batteries (LMBs) have attracted widespread attention in recent years because of their high energy densities. But traditional LMBs using liquid electrolyte have potential safety hazards, such as: leakage and flammability. Replacing liquid electrolyte with solid polymer electrolyte (SPE) can not only significantly improve the safety, but also improve the energy density of LMBs. However, till now, there is only limited success in improving the various physical and chemical properties of SPE, especially in thickness, posing great obstacles to further promoting its fundamental and applied studies. In this review, the authors mainly focus on evaluating the merits of ultrathin SPE and summarizing its existing challenges as well as fundamental requirements for designing and manufacturing advanced ultrathin SPE in the future. Meanwhile, the authors outline existing cases related to this field as much as possible and summarize them from the perspective of synthetic chemistry, hoping to provide a comprehensive understanding and serve as a strategic guidance for designing and fabricating high‐performance ultrathin SPE. Challenges and opportunities regarding this burgeoning field are also critically evaluated at the end of this review. This study mainly focuses on the trend of applying established synthetic chemistries in manipulating the thickness of SPE to bridge its incorporations with practical electrochemical devices with high‐energy‐density LMBs. The advantages and existing challenges of ultrathin SPE are discussed, while the progress of ultrathin SPE based on synthetic chemistry are summarized and several typical fabrication methods are looked back upon.

Increasing concerns about air quality due to fossil fuel combustion, especially nitrogen oxides (NOx) from marine and diesel engines, necessitate advanced monitoring systems due to the significant health and environmental impacts of nitrogen dioxide (NO2). In this study, a gas detection system based on the principle of the non-dispersive infrared (NDIR) technique is proposed. Firstly, the pyroelectric detector was developed by employing an ultra-thin LiTaO3 (LT) layer as the sensitive element, integrated with nanoscale carbon material prepared by wafer-level graphics technology as the infrared absorption layer. Then, the sensor was hermetically sealed using inert gas through energy storage welding technology, exhibiting a high detectivity (D*) value of 4.19 × 108 cm·√Hz/W. Subsequently, a NO2 gas sensor was engineered based on the NDIR principle employing a Micro Electro Mechanical System (MEMS) infrared (IR) emitter, featuring a light path chamber length of 1.5 m, along with integrated signal processing and software calibration algorithms. This gas sensor was capable of detecting NO2 concentrations within the range of 0–500 ppm. Initial tests indicated that the gas sensor exhibited a full-scale relative error of less than 0.46%, a limit of 2.8 ppm, a linearity of −1.09%, a repeatability of 0.47% at a concentration of 500 ppm, and a stability of 2% at a concentration of 500 ppm. The developed gas sensor demonstrated significant potential for application in areas such as industrial monitoring and analytical instrumentation.

All‐solid‐state Li metal batteries (ASSLMBs) have been considered the most promising candidates for next‐generation energy storage devices owing to their high‐energy density and safety. However, some obstacles such as thick solid electrolyte (SSEs) and unstable interface between the solid‐state electrolytes (SSEs) and the electrodes have restricted the practical application of ASSLBs. Here, the scalable polyimide (PI) film reinforced asymmetric ultra‐thin (~20 μm) composite solid electrolyte (AU‐CSE) with a ceramic‐rich layer and polymer‐rich layer is fabricated by a both‐side casting method and rolling process. The ceramic‐rich layer not only acts as a “securer” to inhibit the lithium dendrite growth but also redistributes Li‐ions uniform deposition, while the polymer‐rich layer improves the compatibility with cathode materials. As a result, the obtained AU‐CSE demonstrates an ionic conductivity of 1.44 × 10−4 S cm−1 at 35°C. The PI‐reinforced AU‐CSE enables Li/Li symmetric cell stable cycling over 1200 h at 0.2 mA cm−2 and 0.2 mAh cm−2. Li/LiNi0.6Co0.2Mn0.2O2 and Li/LiFePO4 ASSLMBs achieve superior performances at 35°C. This study provides a new way of solving the interface problems between SSEs and electrodes and developing high‐energy‐density ASSLMBs for practical applications. An asymmetric ultra‐thin composite solid electrolyte with ceramic‐ and polymer‐rich layers was constructed to simultaneously overcome the lithium dendrite growth on the anode side and the large resistance on the cathode side.

Li metal batteries have been widely expected to break the energy‐density limits of current Li‐ion batteries, showing impressive prospects for the next‐generation electrochemical energy storage system. Although much progress has been achieved in stabilizing the Li metal anode, the current Li electrode still lacks efficiency and safety. Moreover, a practical Li metal battery requires a thickness‐controllable Li electrode to maximally balance the energy density and stability. However, due to the stickiness and fragile nature of Li metal, manufacturing Li ingot into thin electrodes from conventional approaches has historically remained challenging, limiting the sufficient utilization of energy density in Li metal batteries. Aiming at the practical application of Li metal anode, the current issues and their initiation mechanism are comprehensively summarized from the stability and processability perspectives. Recent advances in robust and ultra‐thin Li metal anode are outlined from methodology innovation to provide an overall insight. Finally, challenges and prospective developments regarding this burgeoning field are critically discussed to afford future outlooks. With the development of advanced processing and modification technology, we are optimistic that a truly great leap will be achieved in the foreseeable future toward the industrial application of Li metal batteries. A practical Li metal battery requires a stable and ultra‐thin Li electrode. In this review, the fundamental issues of a practical Li electrode are summarized from the stability and processability perspectives. Also, recent advances in methodologies toward robust and ultra‐thin Li metal anode are comprehensively summarized to provide overall insights. Furthermore, challenges as well as perspectives are presented for the future.

The interfacial engineering in solid‐state lithium batteries (SSLBs) is attracting escalating attention due to the profoundly enhanced safety, energy density, and charging capabilities of future power storage technologies. Nonetheless, polymer/ceramic interphase compatibility, serious agglomeration of ceramic particles, and discontinuous ionic conduction at the electrode/electrolyte interface seriously limit Li+ transport in SSLBs and block the application and large‐scale manufacturing. Hence, garnet Li7La3Zr2O12 (LLZO) nanoparticles are introduced into the polyacrylonitrile (PAN) nanofiber to fabricate a polymer‐ceramic nanofiber‐enhanced ultrathin SSE membrane (3D LLZO‐PAN), harnessing nanofiber confinement to aggregate LLZO nanoparticles to build the continuous conduction pathway of Li+. In addition, a novel integrated electrospinning process is deliberately designed to construct tight physical contact between positive electrode/electrolyte interphases. Importantly, the synergistic effect of the PAN, polyethylene oxide (PEO), and lithium bis((trifluoromethyl)sulfonyl)azanide (LiTFSI) benefits a stable solid electrolyte interphase (SEI) layer, resulting in superior cycling performance, achieving a remarkable 1500 h cycling at 0.2 mA cm−2 in the Li|3D LLZO‐PAN|Li battery. Consequently, the integrated polymer‐ceramic nanofiber‐enhanced SSEs simultaneously achieve the balance in ultrathin thickness (16 μm), fast ion transport (2.9 × 10−4 S cm−1), and superior excellent interface contact (15.6 Ω). The LiNi0.8Co0.1Mn0.1O2|3D LLZO‐PAN|Li batteries (2.7–4.3 V) can work over 200 cycles at 0.5 C. The pouch cells with practical LiNi0.8Co0.1Mn0.1O2||Li configuration achieve an ultrahigh energy density of 345.8 Wh kg−1 and safety performance. This work provides new strategies for the manufacturing and utilization of high‐energy‐density SSLBs. Electrospinning technology was utilized to interweave oxide solid electrolytes into electrode/electrolyte integrated ultra‐thin films with a continuous conductive network, high ion conductivity, and especially remarkable lithium metal stability. Benefiting from the design effect of high‐performance polymer‐ceramic nanoparticle‐reinforced fiber ultra‐thin films and the synergistic effect of the integrated spinning process on the cathode and lithium metal, the assembled symmetric cells displayed excellent cycling stability. The solid electrolyte film prepared by in‐situ spinning technology forms a stable, ultra‐thin, and tight interface, exhibits excellent electrochemical performance and a high‐level energy density, paving the way for the industrialization of high‐performance composite solid‐state batteries.

The ion‐sensitive field effect transistors (ISFETs), proposed little over 50 years ago, today make the most promising devices for lab‐on‐a‐chip, implantable, and point‐of‐care (POC) diagnostics. Their compatibility with CMOS (Complementary Metal Oxide Semiconductor) technology and the low cost through mass production have been the driving factors so far. Nowadays, they are also being developed in flexible form factors for new applications such as wearables and to improve the effective usage in existing applications such as implantable systems. In this regard, the CMOS ultra‐thin chip (UTC) technology and the bonding by printing are the noteworthy advances. This paper comprehensively reviews such new developments in the CMOS‐compatible ISFETs, along with their theory, readout circuitries, circuit‐based techniques for compensation of the ISFET's instabilities, such as the offset, flicker noise, and drift. The sensing mechanisms and the properties of interface between the electrolyte under test and the metal‐oxide based ion‐sensitive electrodes have been discussed along with a brief overview of the metal‐oxide based pH sensors. An overview of the reported mechanically flexible pH sensors, including ISFETs, is provided and the history of ISFET applications are also covered. Finally, established models that can be used to design flexible circuits are presented, and possible opportunities to use circuit techniques to compensate for mechanical deformation are discussed.

This work reports on changes in the properties of ultra-thin PECVD silicon oxynitride layers after high- temperature treatment. Possible changes in the structure, composition and electrophysical properties were investigated by means of spectroscopic ellipsometry, XPS, SIMS and electrical characterization methods (C-V, I-V and charge- pumping). The XPS measurements show that SiOxNy is the dominant phase in the ultra-thin layer and high-temperature annealing results in further increase of the oxynitride phase up to 70% of the whole layer. Despite comparable thickness, SIMS measurement indicates a densification of the annealed layer, because sputtering time is increased. It suggests complex changes of physical and chemical properties of the investigated layers taking place during high-temperature annealing. The C-V curves of annealed layers exhibit less frequency dispersion, their leakage and charge-pumping currents are lower when compared to those of as-deposited layers, proving improvement in the gate structure trapping properties due to the annealing process.

In this paper differences in chemical composition of ultra-thin silicon oxynitride layers fabricated in planar rf plasma reactor are studied. The ultra-thin dielectric layers were obtained in the same reactor by two different methods: ultrashallow nitrogen implantation followed by plasma oxidation and plasma enhanced chemical vapour deposition (PECVD). Chemical composition of silicon oxynitride layers was investigated by means of X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The spectroscopic ellipsometry was used to determine both the thickness and refractive index of the obtained layers. The XPS measurements show considerable differences between the composition of the fabricated layers using each of the above mentioned methods. The SIMS analysis confirms XPS results and indicates differences in nitrogen distribution.

Monitoring process parameters in the manufacture of composite structures is key to ensuring product quality and safety. Ideally, this can be done by sensors that are embedded during production and can remain as devices to monitor structural health. Extremely thin foil-based sensors weaken the finished workpiece very little. Under ideal conditions, the foil substrate bonds with the resin in the autoclaving process, as is the case when polyetherimide is used. Here, we present a temperature sensor as part of an 8 µm thick multi-sensor node foil for monitoring processing conditions during the production and structural health during the lifetime of a construction. A metallic thin film conductor was shaped in the form of a space-filling curve to suppress the influences of resistance changes due to strain, which could otherwise interfere with the measurement of the temperature. FEM simulations as well as experiments confirm that this type of sensor is completely insensitive to the direction of strain and sufficiently insensitive to the amount of strain, so that mechanical strains that can occur in the composite curing process practically do not interfere with the temperature measurement. The temperature sensor is combined with a capacitive sensor for curing monitoring based on impedance measurement and a half-bridge strain gauge sensor element. All three types are made of the same materials and are manufactured together in one process flow. This is the key to cost-effective distributed sensor arrays that can be embedded during production and remain in the workpiece, thus ensuring not only the quality of the initial product but also the operational reliability during the service life of light-weight composite constructions.

Carbonaceous materials have been regarded as highly promising anode candidates for potassium storage with their cost‐effectiveness and environmental benignity. However, low specific capacity and difficulty in large‐scale synthesis largely hinder their further development. Herein, a thermal‐induced potassium–carbon alloy phase (KxCy) with the expanded interlayer spacing strategy is first put forward. Through in situ high‐temperature X‐ray diffraction, a K2C2 phase is evoked by thermal energy during the in‐situ carbonization process of carbon quantum dots intermediate derived from potassium‐containing precursors, whereas no lithium or sodium–carbon alloy phase is observed from lithium/sodium‐containing precursors. The as‐obtained ultra‐thin carbon nanosheets achieve adjustable layer spacing, preparation in bulk, delivering reversible potassium storage of 403.4 mAh g−1 at 100 mA g−1 and 161.2 mAh g−1 even at 5.0 A g−1, which is one of the most impressive K‐storage performances reported so far with great potential application. Furthermore, the assembled potassium‐ion hybrid capacitor by combining the impressive CFMs‐900 anode with the three‐dimensional framework‐activated carbon delivers a high energy‐power density of 251.7 Wh kg−1 at 250 W kg−1 with long‐term stability. This study opens a scalable avenue to realize the expanded interlayer spacing, which can be extended to other multicarboxyl potassium salts and can provide approach for the design of high‐performance carbon anode materials for potassium storage. A thermal‐induced KxCy with an expanded interlayer spacing strategy is first proposed in this manuscript, which enables highly reversible potassium‐storage capability with superior long‐term cycling stability. In situ high‐temperature X‐ray diffraction and high‐resolution transmission electron microscopy techniques have been utilized to demonstrate the existence of the K2C2 phase and the evoked carbon expanded interlayer, which successfully validates the feasibility of the offered strategy.