Search

Garnet-type Li7La3Zr2O12(LLZO) solid electrolytes are synthesized with interconnected and larger rounded particle morphologies using a cellulose template method and conventional solid-state reaction, respectively. The synthesized LLZOs are optimized and used as a solid electrolyte in a natural graphite (NG)-based composite anode in an all-solid-state lithium battery. For the LLZO with the interconnected particle morphology, the optimum heat-treatment temperature (900 °C) and LLZO content (30 wt%) are determined to result in higher ionic conductivity. That is, higher dispersion or good distribution of the interconnected LLZO (width of 1 μm or less) within the composite anode enables easier ionic conduction of the interconnected LLZO. The NG-based composite anode filled with interconnected LLZO shows effective improvement due to a well-controlled inner percolation structure, resulting in improved cycle stability and enhanced high-rate capability, compared with the composite anode embedded with conventional spherical-type LLZO particles.

An environmentally-friendly lead-free methylammonium tin iodide (MASnI3) perovskite is successfully synthesized using a facile approach of an antisolvent-assisted collision technique (ACT) under room ambient conditions, which results stability within 24 h under ambient room conditions. The phase transition of MASnI3from tetragonal to cubic is first observed at ~ 30 °C. Polycrystalline MASnI3films reveal a high dielectric constant of ~ 65 at 100 kHz, a low-leakage current density of 7 × 10−7A cm−2at 50 kV cm−1, well-developed P-E hysteresis loops, and a high piezoelectric coefficient (d33) of 20.8 pm V−1. The MASnI3piezoelectric nanogenerator (PENG) shows an output voltage of ~ 3.8 V and an output current density of 0.35 μA cm−2. To enhance the piezoelectric output performance, the MASnI3films are composited with an environmentally friendly PVDF polymer that had a porous structure. The PVDF-MASnI3composite based-PENG reveals a maximum output voltage of ~ 12.0 V and current density of ~ 4.0 μA cm−2. A green light-emitting diode (LED) using the PVDF-MASnI3PENGs is instantly lighted without need of a storage device, and long-term stability of the composite PENGs is validated for 90 days. This simple and cost-effective solution process is feasible for the fabrication of large-scale, high-performance, and environmental-friendly PENGs based on lead-free organic-inorganic perovskites to extensively implicate in medical and biomechanical applications.

As future generations of wearable electronics are expected to be directly worn, fiber-based electronics are expected to become increasingly more important in the coming years, as they can be weaved into textiles to provide higher comfort, durability, and integrated multi-functionalities. Herein, we demonstrate an intrinsically stretchable multi-functional hollow fiber capable of harvesting mechanical energy and detecting strain. For energy harvesting, we have utilized a stretchable ferroelectric layer composed of P(VDF-TrFE) in a matrix of elastomer, sandwiched between stretchable electrodes composed of multi-walled carbon nanotubes and PEDOT:PSS. We have demonstrated voltage and current generation under stretching and normal pressure, with output voltage and current as high as 1.2 V and 10 nA, respectively. Furthermore, the hollow architecture enabled the harvesting of pressure coming from internal liquid flow, adding another dimension of harvesting mechanical energy. The stretchable electrodes were used as strain sensors, which exhibited high gauge factor of 80–177 in the 0–50% strain range, along with low hysteresis and durability. These features render our multi-functional fiber highly suitable for wearable electronic applications in the near future.

Subalpine ecosystems at high altitudes and latitudes are particularly sensitive to climate change. In South Korea, the prediction of the species richness of subalpine plant species under future climate change is not well studied. Thus, this study aims to assess the potential impact of climate change on species richness of subalpine plant species (14 species) in the 17 mountain national parks (MNPs) of South Korea under climate change scenarios’ representative concentration pathways (RCP) 4.5 and RCP 8.5 using maximum entropy (MaxEnt) and Migclim for the years 2050 and 2070. Altogether, 723 species occurrence points of 14 species and six selected variables were used in modeling. The models developed for all species showed excellent performance (AUC > 0.89 and TSS > 0.70). The results predicted a significant loss of species richness in all MNPs. Under RCP 4.5, the range of reduction was predicted to be 15.38–94.02% by 2050 and 21.42–96.64% by 2070. Similarly, under RCP 8.5, it will decline 15.38–97.9% by 2050 and 23.07–100% by 2070. The reduction was relatively high in the MNPs located in the central regions (Songnisan and Gyeryongsan), eastern region (Juwangsan), and southern regions (Mudeungsan, Wolchulsan, Hallasan, and Jirisan) compared to the northern and northeastern regions (Odaesan, Seoraksan, Chiaksan, and Taebaeksan). This result indicates that the MNPs at low altitudes and latitudes have a large effect on the climate change in subalpine plant species. This study suggested that subalpine species are highly threatened due to climate change and that immediate actions are required to conserve subalpine species and to minimize the effect of climate change.

We report a high-performance flexible piezoelectric generator (PEG) that was based on organic-inorganic lead halide perovskite materials and is operated by controlling the dielectric constant via the partial substitution of Pb2+with Fe2+in MAPbI3. The partial replacement of Pb2+with Fe2+improved both the morphology and crystallinity of MAPb1-xFexI3(0.01 ≤ x ≤ 0.50) films that undergo a tetragonal-cubic phase transition above an incorporated concentration of Fe2+(x > 0.07). In addition, the phase transition temperatures of MAPb1-xFexI3(0.01 ≤ x ≤ 0.07) films linearly decreased as a function of incorporated concentration, which resulted in a transition temperature for MAPb1-xFexI3(x = 0.07) of ~ 45.5 ± 1.5 °C. The dielectric properties as a function of incorporated concentration at room temperature suggested that MAPb1-xFexI3(x = 0.07) exhibited a dielectric constant of ~107 and a dissipation factor of 0.02 at 100 kHz. The MAPb1-xFexI3(x = 0.07) films exhibited a low leakage current density of ~ 10−6at a high applied electric field of 40 kV/cm, and the resultant remanent polarization from saturated ferroelectric P-E hysteresis loops was ~ 1.6 µC/cm2. The MAPb1-xFexI3(x = 0.07) flexible PEG improved output performance by ~ 7.29 V and current density by ~ 0.88 µA/cm2after poling at 30 kV/cm. This was sufficient to instantly light a commercial light-emitting diode (LED) without a storage device. This approach provides a framework that enhances the output performance of organic-inorganic metal halide perovskite materials-based piezoelectric energy harvesters, which could help pave the road to viable, self-powered, wearable electronics.

Memristive devices are an emerging technology that enables both rich interdisciplinary science and novel device functionalities, such as nonvolatile memories and nanoionics-based synaptic electronics. Recent work has shown that the reproducibility and variability of the devices depend sensitively on the defect structures created during electroforming as well as their continued evolution under dynamic electric fields. However, a fundamental principle guiding the material design of defect structures is still lacking due to the difficulty in understanding dynamic defect behavior under different resistance states. Here, we unravel the existence of threshold behavior by studying model, single-crystal devices: resistive switching requires that the pristine oxygen vacancy concentration reside near a critical value. Theoretical calculations show that the threshold oxygen vacancy concentration lies at the boundary for both electronic and atomic phase transitions. Through operando, multimodal X-ray imaging, we show that field tuning of the local oxygen vacancy concentration below or above the threshold value is responsible for switching between different electrical states. These results provide a general strategy for designing functional defect structures around threshold concentrations to create dynamic, field-controlled phases for memristive devices.

Abstract

Many studies about climate-related range shift of plants have focused on understanding the relationship between climatic factors and plant distributions. However, consideration of adaptation factors, such as dispersal and plant physiological processes, is necessary for a more accurate prediction. This study predicted the future distribution of marlberry (Ardisia japonica), a warm-adapted evergreen broadleaved shrub, under climate change in relation to the dispersal ability that is determined by elapsed time for the first seed production. We introduced climate change data under four representative concentration pathway (RCP 2.6, 4.5, 6.0, and 8.5) scenarios from five different global circulation models (GCMs) to simulate the future distributions (2041~2060) of marlberry. Using these 20 different climate data, ensemble forecasts were produced by averaging the future distributions of marlberry in order to minimize the model uncertainties. Then, a dispersal-limited function was applied to the ensemble forecast in order to exam the impact of dispersal capacity on future marlberry distributions. In the dispersal-limited function, elapsed time for the first seed production and possible dispersal distances define the dispersal capacity. The results showed that the current suitable habitats of marlberry expanded toward central coast and southern inland area from the current southern and mid-eastern coast area in Korea. However, given the dispersal-limited function, this experiment showed lower expansions to the central coast area and southern inland area. This study well explains the importance of dispersal capacity in the prediction of future marlberry distribution and can be used as basic information in understanding the climate change effects on the future distributions of Ardisia japonica.