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As an important medium of human-computer interaction, flexible tactile sensors have a vital influence on the intelligence and safety of a system by accurately identifying the contact position and force. For now, most of the existing flexible capacitive pressure sensors adopt an array structure, which still cannot meet the requirements including simple manufacturing, simple wiring, and low cost. This paper innovatively proposes a flexible array-less capacitive tactile sensor, a 30 mm × 30 mm sensor prototype, consisting of flexible electrodes and a dielectric layer of a polydimethylsiloxane (PDMS) and multiwalled carbon nanotube (MWCNT) composite. Under the action of a contact force, the contact area is deformed, resulting in a capacitance change in the flexible sensor. First, Poisson’s equation is used to determine the relationship between the electric potential and position. Then, elastic contact mechanics is adopted to describe the relationship between the electric charges and force. Finally, the contact position and force are recognized by measuring the change in capacitance in real time, based on the classical principle of capacitance. Simulation and experimental results verified the effectiveness of the proposed recognition method, showing that the recognition resolution of contact position can reach 500 μm × 100 μm, and the accuracy of contact force is 95.85%. Theoretically, the proposed flexible array-less sensor in this paper has infinite spatial resolution, and most importantly, it does not rely on complex manufacturing, redundant circuits, or sensor cell arrays. Therefore, it has broad application prospects in related fields such as electronic skin and wearable electronic devices.

Oxide thin-film transistors (TFTs) have attracted much attention because they can be applied to flexible and large-scaled switching devices. Especially, oxide semiconductors (OSs) have been developed as active layers of TFTs. Among them, indium-gallium-zinc oxide (IGZO) is actively used in the organic light-emitting diode display field. However, despite their superior off-state properties, IGZO TFTs are limited by low field-effect mobility, which critically affects display resolution and power consumption. Herein, we determine new working mechanisms in dual-stacked OS, and based on this, we develop a dual-stacked OS-based TFT with improved performance: high field-effect mobility (∼80 cm2/V·s), ideal threshold voltage near 0 V, high on-off current ratio (>109), and good stability at bias stress. Induced areas are formed at the interface by the band offset: band offset-induced area (BOIA) and BOIA-induced area (BIA). They connect the gate bias-induced area (GBIA) and electrode bias-induced area (EBIA), resulting in high current flow. Equivalent circuit modeling and the transmission line method are also introduced for more precise verification. By verifying current change with gate voltage in the single OS layer, the current flowing direction in the dual-stacked OS is calculated and estimated. This is powerful evidence to understand the conduction mechanism in a dual-stacked OS-based TFT, and it will provide new design rules for high-performance OS-based TFTs.

Halide perovskites have drawn considerable attention as a remarkable material in advanced optoelectronics. However, toxicity and poor stability of halide perovskites are major challenges hindering ...

The Li metal anode has high theoretical specific capacity and low redox potential, making it suitable as an anode material for next-generation Li ion-based batteries (LIBs); however, challenges remain due to its unstable solid electrolyte interphase (SEI). In this study, we applied graphene-coated aramid attached to an uncoated aramid separator fabricated using a simple painting method to a Li metal anode to address the issues caused by the unstable SEI via fluorinated metathesis on a conjugated carbon network (CCN). The graphene-coated surface was partially fluorinated in a specific solvent environment, and as the Li+ ions were plated, the fluorinated surface induced formation of LiF as a chemically stable SEI component. Additionally, we demonstrated the successful application of fluorinated metathesis using other CCN materials, such as carbon black and activated carbon. The experimental results indicated that the CCN materials induced LiF via fluorination, and that the negative functionalities and lattice structure of the CCN materials affected the fluorination. These results demonstrated the effectiveness of this novel method for stabilizing a Li metal surface using a graphite pencil.

Recently, organic compounds are considered as promising candidates for application in next-generation energy storage systems to overcome the disadvantages of conventional inorganic cathode materials, including their low specific capacity and poor disposal systems. In particular, pillar[5]quinone (P5Q) is very effective as it provides active sites that favor Li uptake and promote a high theoretical capacity. Herein, we propose P5Q-derived cathodes, which are enveloped in multi-walled carbon nanotubes and cellulose nanofibers (CNFs), fabricated by a simple vacuum-filtering method. The designed cathode solves the issues associated with organic materials, including their high solubilities in aprotic electrolytes and low conductivities. Furthermore, CNFs are introduced as alternatives to conventional polyolefin separators. CNF separators can effectively suppress the dissolution of active materials in liquid electrolytes. In addition, CNFs improve ionic conductivity (0.88 mS cm−1), electrolyte wettability (electrolyte uptake: 333.41%, porosity: 70 ± 5%), and thermal shrinkage in contrast to conventional polyolefin separators. The Li-ion battery, assembled with the suggested P5Q cathode and CNF separator, exhibits highly stable capacity retention (76.5% after 50 cycles at a 0.2 C rate) and good rate capability, although an organic electrolyte is used.

Recently, lithium–sulfur batteries (LSBs) have been highlighted as next-generation batteries due to the high theoretical capacity of the sulfur nonmetal and Li metal. However, LSBs are difficult to be commercialized because of the continuous capacity fading phenomenon derived from the shuttle effect of lithium polysulfide. Herein, a novel organic–inorganic composite separator composed of poly(vinylidene fluoride-co-hexafluoropropylene) and anodic aluminum oxide is proposed to overcome these limitations. The proposed separator strongly reduces the dissolution issue of lithium polysulfide and considerably limits the movement of polysulfide. Moreover, it improves the stability of the lithium metal anode by evenly distributing the flux of lithium ions. Also, it shows excellent thermal stability and good electrolyte wettability. Therefore, the ionic conductivity shows a high value of more than 1 mS cm−1, and the coulombic efficiency is over 99%. The LSBs assembled with the composite separator exhibit the maintained specific capacity over of 75% after 100 cycles at 0.5C.

Li metal is an ideal anode material for batteries based on Li ion because of its high theoretical specific capacity and low redox potential. However, the repeated formation and collapse of solid el...

Metal oxide semiconductors doped with additional inorganic cations have insufficient electron mobility for next-generation electronic devices so strategies to realize the semiconductors exhibiting stability and high performance are required. To overcome the limitations of conventional inorganic cation doping to improve the electrical characteristics and stability of metal oxide semiconductors, we propose solution-processed high-performance metal oxide thin-film transistors (TFTs) by incorporating polyaniline (PANI), a conductive polymer, in a metal oxide matrix. The chemical interaction between the metal oxide and PANI demonstrated that the defect sites and crystallinity of the semiconductor layer are controllable. In addition, the change in oxygen-related chemical bonding of PANI-doped indium oxide (InOx) TFTs induces superior electrical characteristics compared to pristine InOx TFTs, even though trace amounts of PANI are doped in the semiconductor. In particular, the average field-effect mobility remarkably enhanced from 15.02 to 26.58 cm2 V-1 s-1, the on/off current ratio improved from 108 to 109, and the threshold voltage became close to 0 V actually from -7.9 to -1.4 V.

Lithium metal is one of the most attractive anode materials, due to its high theoretical specific capacity and lowest electrochemical potential. However, low coulombic efficiency and serious safety hazards have still hindered the wide applications of next-generation batteries including Li–S and Li–air. Previous studies have suggested overcoming the problem by applying various structures of current collectors. These structures homogenize the Li ion flux or provide space for volume expansion. However, there are some limitations to solving problems occurring at the Li metal surface, because the current collector is underneath the structures of Li metal. In this work, we propose a facile and cost-effective strategy for stabilizing the lithium metal–electrolyte interface via a three-dimensional stainless steel mesh (SSM) interlayer. Its high specific surface area lowers the local current density and provides an electronic flow path for dead Li. Also, this structure leads to confinement of Li deposits and alleviates volume expansion. As a result, the Li anode with the SSM interlayer operated at current densities of 1 mA cm−2 (1C rate) and 5 mA cm−2, and it exhibited a longer cycle-life than planar structures in a symmetrical cell configuration.

Li metal is one of the best candidate anode materials for next-generation Li ion batteries (LIBs) and the most promising anode material that can replace the carbonaceous anode currently in use because of its high theoretical specific capacity and low redox potential (vs. SHE). Nevertheless, in order to apply Li metal to LIBs as an anode, issues such as those related to the cycle characteristics such as the life span and C-rate capability need to be resolved. These issues arise owing to the solid electrolyte interphase (SEI) formed on the surface of the Li metal anode (LMA). Unlike the conventional graphite anode, which exhibits a stable intercalation/de-intercalation mechanism, the Li metal anode, which utilizes a lithiation-delithiation mechanism known as hostless electrochemical plating/stripping to charge/discharge, undergoes repeated formation/collapse of an unstable SEI layer on its surface. Thus, the LMA is continuously exposed to undesirable interfacial reactions with the liquid electrolyte. The continuous occurrence of these side-reactions deteriorates the cycle characteristics of the LMA. In particular, this phenomenon gradually intensifies as the applied current increases, leaving the LMA operative within limited cycles at a high current density. Thus, the surface of the LMA needs to be subjected to additional treatments, based on studies of interfacial phenomena, for introducing it to LIBs, which many research groups attempted. Of the many approaches, studies that stabilization of the LMA surface by the introduction of a conductive interlayer between the LMA and separator or by applying a functional separator provided excellent results and the advantage using Li metal without structural modification. Similarly, a good interlayer or functional separator should be able to control undesirable interfacial reactions by the formation of the stable SEI layer, which prevents accumulation of an inactive layer and liquid electrolyte depletion, maintaining the cycle characteristics of LMA. In particular, when there is a conductive interlayer above the LMA, the conductive interlayer at the top structurally meets the Li+ ion flux first during the plating step. Therefore, the SEI layer formed is more stable on the conductive interlayer than on the LMA surface and could thus ensure surface stability of the LMA, preventing repeated SEI formation/collapse, dendritic growth, and liquid electrolyte depletion. In consideration of this point, in this work, we proposed non-woven type reduced graphene oxide fibers attached to aramid paper (rGOF-A) as an advanced separator to solve the aforementioned issues presented by an unstable SEI layer. When the rGOF side of rGOF-A contacts the Li metal anode, it functions effectively as a conductive frame, so the electrons can migrate from the underlying the LMA to the rGOF as the current is applied. Thus, the rGOF first meets the Li+ ion flux rather than the LMA, and the SEI layer, which has different chemical characteristics than those of the LMA surface, forms more stably mainly on rGOF in strong reductive conditions. In other words, rGOF can act a conductive layer and induces formation of the SEI layer in rGOF, not the LMA, helping toward stable operation of the LMA. In addition, this formed stable SEI layer can be effectively confined within the rGOF frame to have a high modulus. Moreover, as the electrolyte is consumed to form the SEI layer on the surface of rGOF, chemically reactive C–F bonds are generated at the surface of rGOF and the partially fluorinated rGOF surface induces the formation of LiF known as the component of the stable SEI during the Li+ ion plating process. LiF is a key component in a stable SEI layer on the LMA because it has a wide electrochemical stability window and improves the surface diffusion of ions, which can lead to smooth Li plating. Thus, LiF protects the LMA from further repeated SEI layer formation/collapse processes and helps the LMA to operate reliably. This passivation effect of rGOF on the LMA surface allows the LMA to maintain its cycle characteristics for a rapid charging/discharging condition (20 mA cm-2, 1 mAh cm-2) as well as at a higher areal capacity (20 mA cm-2,20 mAh cm-2) than practical application condition. Thus, the rGOF-A functional separator ensures cycling stability of the LMA without any deteriorating factor, which contributes to large Li source irreversibility, and this does not involve a structural change for the LMA or additional treatments such as those involving additives to maintain to the cycle characteristics or lifespan. Figure 1

Lithium-ion batteries (LIBs) have been widely used in many industries in recent years. In particular, the electrical vehicles (EVs) and energy storage system (ESS) markets are growing rapidly, and the requirements for LIBs are also growing. Under these circumstances, the active materials for LIBs that have been used are insufficient in various aspects. The most important characteristics of newly requested LIBs are economics and capacity. Until now, the industry sector where LIBs were mainly used was mainly devices with relatively small size and output, such as portable electronic devices. Therefore, if a certain level of capacity was secured in LIBs, there was no demand for an extremely large-capacity battery. However, due to changes in the industry, devices that require high power and long-term use, such as EVs and ESS, have emerged as new demands, and the requirements of LIBs have gradually changed to emphasize the capacity side. The cathode active materials used in commercially available LIBs are mostly metal oxides containing rare metals such as nickel and cobalt. These metal oxide-based cathode active materials have a relatively low theoretical capacity, unstable supply, and low production. So the price fluctuation is very high and the price is also very expensive. Anode has also been sideways for decades without significant changes in capacity since LIBs were commercialized, and new attempts at the active material level are needed. Research to introduce a new active material to secure these shortcomings has become more active in recent years. Lithium-sulfur batteries (LSBs), which use sulfur as the cathode material and lithium metal as the anode active material, are receiving great attention as next-generation LIBs in this respect. In the case of sulfur used as a cathode active material, charging and discharging proceeds through a conversion reaction between sulfur and lithium, and thus has a very high theoretical capacity. This shows the potential to be a positive electrode active material with a significantly higher capacity than materials having a layered structure of a metal oxide series used in the conventional LIBs. Also, as a by-product of the petrochemical industry, a very large amount of supply is made, but the demand is not so abundant, so it has a very low price. Lithium metal, which is used as an anode active material, also has a very large capacity, making it one of the most actively studied materials in the LIBs field. Lithium metal has a theoretical capacity of over 3800mAh g-1, so its potential is endless. However, despite these great advantages, LSBs have not been commercialized because there are big disadvantages to be solved. When considering the problems caused by the cathode and those caused by the anode, the problem with cathode active material is the lack of life characteristics. In particular, the biggest problem is that the capacity of the system continuously decreases due to the dissolution of lithium polysulfide. Lithium polysulfide, an intermediate produced during the charging and discharging process, dissolves very well in the organic liquid electrolyte, so it moves freely between the cathode and the anode. At this time, since it is continuously reduced in the anode region to form an inactive layer, as the cycle progresses, the amount of active material decreases, so that life characteristics are not secured. Another major problem is that caused by lithium metal used as an anode. Lithium metal shows low coulombic efficiency by repeatedly generating an SEI layer on the surface as charging and discharging progress. Furthermore, it reacts with the liquid electrolyte and continuously consumes electrolyte and active material, showing very poor life characteristics. In this study, we proposed a new type of organic-inorganic composite separator that can solve the above two problems at once. The proposed separator (PAAO) was fabricated by filling poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) on the surface and inside of anodic aluminum oxide (AAO). Since AAO has vertical pores with regular spacing, it provides stability at the interface of lithium metal to improve the life characteristics of the anode. Also, PVdF-HFP provided a passage for lithium ions inside the pores of AAO and effectively prevented the movement of lithium polysulfide. AAO showed an improved lifespan of over 50% compared to a separator made of a commercially available polyolefin-based polymer. As a result, PAAO showed an improved lifespan of more than 50% and high coulomb efficiency in all cycles compared to the separator made of commercially available polyolefin-based polymers. We believe that PAAO has shown potential as a new separator that can be applied to next-generation LSBs. Figure 1

The exact direction, of the surface energy characterized functional group of self-assembled monolayer (SAM), is proposed for achieving the enhanced electrical stability of indium gallium zinc oxide (IGZO) semiconductor thin film transistor (TFT). The SAM treatment, particularly at the SAM functional group having lower surface energy, makes oxygen molecules difficult to be adsorbed onto IGZO. And such an effect much improves positive bias stability (PBS) and clockwise hysteresis stability to the same tendency. For NH2 and CF3 functional group SAMs with surface energies of 49.4 mJ/m2 and 23.5 mJ/m2, respectively, the IGZO TFT PBS was improved from 2.47 V to 0.32 V after the SAM treatment and the IGZO TFT clockwise hysteresis was also enhanced from 0.23 V to 0.11 V without any deterioration of TFT characteristics. Employing lower surface energy functional group to the SAM, of same head group and body group, does passivate and protect the IGZO backchannel region from oxygen molecules in the atmosphere. Consequently, the enhanced electrical stability of IGZO TFT can be achieved by the simple and economic SAM treatment.