Thin-film lithium-ion microbatteries with a high energy density and long lifespan are exceedingly desired for developing self-powered integrated micro-nano devices and systems. However, exploring high-performance thin-film anodes still remains a challenge. Herein, a double-layer-structure diamond-like carbon-ZnS (DLC-ZnS) thin-film anode fabricated by radio frequency magnetron sputtering exhibits high specific capacity and good cycling stability up to 1000 cycles, superior to the pure ZnS thin-film anode. To understand the mechanism, the bimodal amplitude modulated-frequency modulated atomic force microscopy was used to explore the mechanical properties of the thin films, and the DLC layer shows significantly higher Young's modulus than the ZnS thin film. The DLC interface with a high Young's modulus can effectively buffer the mechanical stress originating from the huge volume changes of the ZnS layer during lithiation/delithiation processes; therefore, the DLC interface maintains the higher mechanical integrity of the DLC-ZnS thin film and improves the utilization of ZnS. In addition, the electrochemical kinetics of the DLC-ZnS and ZnS thin films were also investigated by electrochemical methods. Electrochemical impedance spectroscopy tests indicate the obstacle of the DLC interface to Li+ ion diffusion in the initial charge/discharge processes; however, the DLC-ZnS thin film exhibits lower total resistance than the ZnS thin film afterward. In particular, galvanostatic intermittent titration technique tests were performed to find out the differences between the two thin films during the galvanostatical charge/discharge processes. The results demonstrate the obviously enhanced conversion reaction reversibility and decreased alloy reaction polarization of the DLC-ZnS thin film; therefore, it delivers higher reversible capacity.
Carbon-coated nickel cobaltate on nickel foam (C@NCO@NF) with stable pseudocapacitive lithium storage capacity was prepared via a two-step strategy. NiCo hydroxide were initially grown on Ni foam via electrodeposition. Subsequent glucose soaking and annealing converted the intermediate into C@NCO@NF. Carbon coating could significantly improve cycling stability and rate performance of the binder-free anode. The C@NCO@NF electrode could stably deliver a reversible capacity of 513 mAh∙g-1 after 500 cycles at a current density of 500 mA∙g-1. It could even stably cycle at a high current density of 5000 mA∙g-1 for 3000 times, with a reversible capacity of 115 mAh∙g-1. Kinetic analysis revealed that surface-controlled pseudo-capacitance play a dominate role in the lithium ion storage. Improved electrochemical performance is attributed to the synergetic effect of pseudo-capacitance and carbon coating.
Lithium-sulfur (Li-S) batteries have attracted great attention owing to their excellent electrochemical properties, such as the high discharge voltage of 2.3 V, specific capacity of 1675 mA h g(-1) and energy density of 2600 Wh kg(-1). The widely used slurry made electrodes of Li-S batteries are plagued by the serious shuttle effect and insulating nature of sulfur. Herein, a reduced graphene oxide coated porous carbon nanofiber flexible paper (rGO@S-PCNP) was fabricated and directly used as an additive-free cathode for Li-S batteries. The results show that the rGO@S-PCNP is certified to be effective at relieving the shuttle effect and improving the conductivity, thus achieving high electrochemical performance. The rGO@S-PCNP composite with a sulfur content of 58.4 wt% delivers a high discharge capacity of 623.7 mA h g(-1) after 200 cycles at 0.1 C (1 C = 1675 mA g(-1)) with the average Coulombic efficiency of 97.1%. The excellent cyclability and high Coulombic efficiency indicate that the as-prepared rGO@S-PCNP composite paper can be a promising cathode for lithium-sulfur batteries, and is envisioned to have great potential in high energy density flexible power devices. This facile strategy brings great significance for large-scale industrial fabrication of flexible lithium-sulfur batteries.
Tin-based materials have been intensively studied as attractive candidates for high-capacity and long-cycle-life anodes in Li-ion batteries (LIBs) owing to their low cost and high energy density. However, they all suffer from severe structural decay during the lithium ion insertion/extraction process, which results in deterioration in the overall performance of the batteries. To mitigate this problem, we have synthesized a Mo-doped SnO2 nanostructure via a facile hydrothermal method, which then fragmented into ultrafine particles after dozens of cycles. The fracture-resistant size and ample contact with Super-P and Li2O greatly improved the electrochemical kinetics and cyclability to deliver a reversible capacity of 670 mA h g-1 after 700 cycles, which demonstrated the potential suitability of Mo-doped SnO2 nanoparticles as a long-cycle-life anode material. Then, the compounds were uniformly dispersed in carbon nanofibers and reduced in situ to prepare a free-standing anode via electrospinning and carbonization. When used directly as an anode in LIBs (without a polymeric binder or conductive agent, as well as a current collector), the nanofiber membrane anode delivered comparable cycling performance and capacity to that of a slurry-coated electrode.
Binder-free nickle cobaltite on carbon nanofiber (NiCo2O4@CNF) anode for lithium ion batteries was prepared via a two-step procedure of electrospinning and electrodeposition. The CNF was obtained by annealing the electrospun poly-acrylonitrile (PAN) in the nitrogen (N2). The NiCo2O4 nanostructures were then grown on the CNF by electrodeposition, followed by annealing in the air. Experimental results showed vertically aligned NiCo2O4 nanosheets were uniformly grown on the surface of CNF, forming an interconnected network. The NiCo2O4@CNF possessed considerable lithium storage capacity and cycling stability. It exhibited a high reversible capacity of 778 mAhg-1 after 300 cycles at a current density of 0.25 C (1 C = 890 mAg-1) with an average capacity loss rate of 0.05% per cycle. The NiCo2O4@CNF had considerable rate capacities, delivering a capacity of 350 mAhg-1 at a current density of 2.0 C. The outstanding electrochemical performance could be mainly attributed to these following reasons. (1) The nanoscale structure of NiCo2O4 could not only shorten the diffusion path of lithium ions and electrons but also increase the specific surface area, providing more active sites for electrochemical reactions. (2) The CNF with considerable mechanical strength and electrical conductivity could function as anchor the NiCo2O4 nanostructure and ensure an efficient electron transfer. (3) The porous structure resulted in high specific surface area and effective buffer the volume changes during the repeated charge-discharge processes. Compared with the conventional hydrothermal method, the electrodeposition could significantly simplify the preparation of NiCo2O4, with shorter preparation period and lower energy consumption. This work provided an alternative strategy to obtain high performance anode for the lithium ion batteries.
Chronic obstructive pulmonary disease (COPD) is a clinical syndrome encompassing a group of chronic, progressive, and debilitating respiratory conditions, that are characterized by incompletely reversible airflow limitation. Within the Asia-Pacific region, prevalence estimates have been derived using various protocols and study methods, and there is little data on the impact of COPD exacerbations. This study aimed to provide a comprehensive picture of the current prevalence and burden of COPD in this region.
Data on patient satisfaction with proton pump inhibitor (PPI) therapy for gastroesophageal reflux disease (GERD) are scarce in Asia. The perspectives of Asian patients with GERD and their satisfaction with PPI therapy were investigated.