Cross-Linked Sodium Alginate as A Multifunctional Binder to Achieve High-Rate and Long-Cycle Stability for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) hold great promise owing to the naturally abundant sodium resource and high safety. The research focus of SIBs is usually directed toward electrode materials, while the binder as an important component is rarely investigated. Herein, a cross-linked sodium alginate (SA)/graphene oxide (GO) binder is judiciously designed to serve as a robust artificial interphase on the surface of both anode and cathode of SIBs. Benefiting from the cross-linking continuous network structure as well as the highly hydrophilic nature, the SA-GO binder possesses a large tensile strength of 197.7 Mpa and a high ionic conductivity of 0.136 mS cm-1 , superior to pure SA (93.8 Mpa, 0.025 mS cm-1 ). Moreover, the structural design of SA-GO binder exhibits a strong binding ability to guarantee structural integrity during cycling. To demonstrate its effectiveness, polyanion-type phosphates (e.g., Na3 (VO)2 (PO4 )2 F) and chalcogenides (e.g., MoS2 , VS2 ) are adopted as cathode and anode materials of SIBs, respectively. As compared to traditional binders (e.g., PVDF, SA), electrodes with the SA-GO binder exhibits significantly increased rate capability and cycling stability, such as Na3 (VO)2 (PO4 )2 F (40 C fast-charge, 84% capacity retention after 1000 cycles). This work highlights the role of novel aqueous-based binders in developing next-generation sodium-storage devices.

Ultrastable Graphite-Potassium Anode through Binder Chemistry.

Graphite with abundant reserves has attracted enormous research interest as an anode of potassium-ion batteries (PIBs) owing to its high plateau capacity of 279 mAh g-1 at ≈0.2 V in conventional carbonate electrolytes. Unfortunately, it suffers from fast capacity decay during K+ storage. Herein, an ultrastable graphite-potassium anode is developed through binder chemistry. Polyvinyl alcohol (PVA) is utilized as a water-soluble binder to generate a uniform and robust KF-rich SEI film on the graphite surface, which can not only inhibit the electrolyte decomposition, but also withstand large volume expansion during K+ -insertion. Compared to the PVDF as binder, PVA-based graphite anode can operate for over 2000 cycles (running time of 406 days at C/3) with 97% capacity retention in KPF6 -based electrolytes. The initial Coulombic efficiency (ICE) of graphite anode is as high as 81.6% using PVA as the binder, higher than that of PVDF (40.1%). Benefiting from the strong adhesion ability of PVA, a graphite||fluorophosphate K-ion full battery is further built through 3D printing, which achieves a record-high areal energy of 8.9 mWh cm-2 at a total mass loading of 38 mg cm-2 . These results demonstrate the important role of binder in developing high-performance PIBs.

A Mechanically Flexible Necklace-Like Architecture for Achieving Fast Charging and High Capacity in Advanced Lithium-Ion Capacitors.

Integration of fast charging, high capacity, and mechanical flexibility into one electrode is highly desired for portable energy-storage devices. However, a high charging rate is always accompanied by capacity decay and cycling instability. Here, a necklace-structured composite membrane consisting of micron-sized FeSe2 cubes uniformly threaded by carbon nanofibers (CNF) is reported. This unique electrode configuration can not only accommodate the volumetric expansion of FeSe2 during the lithiation/delithiation processes for structural robustness but also guarantee ultrafast kinetics for Li+ entry. At a high mass loading of 6.2 mg cm-2 , the necklace-like FeSe2 @CNF electrode exhibits exceptional rate capability (80.7% capacity retention from 0.1 to 10 A g-1 ) and long-term cycling stability (no capacity decay after 1100 charge-discharge cycles at 2 A g-1 ). The flexible lithium-ion capacitor (LIC) fabricated by coupling a pre-lithiated FeSe2 @CNF anode with a porous carbon cathode delivers impressive volumetric energy//power densities (98.4 Wh L-1 at 157.1 W L-1 , and 58.9 Wh L-1 at 15714.3 W L-1 ). The top performance, long-term cycling stability, low self-discharge rate, and high mechanical flexibility make it among the best LICs ever reported.

Evolution of media frames about e-cigarettes from 2004 to 2019: a content analysis of newspapers in China.

This study conducted a content analysis of 639 news articles about e-cigarettes in China from 2004-2019 to examine longitudinal changes in media frames and media tones about e-cigarettes in Chinese newspapers. Results indicated that policy frame was the most frequently used frame, followed by human impact frame, information frame, and uncertainty frame. Dividing the time period of 2004-2019 into four phases (i.e., 2004-2006, 2007-2010, 2011-2017 and 2018-2019), the study found that the frequency of the information frame significantly decreased over time, while the policy frame and uncertainty frame significantly increased, with the policy frame being the dominant frame in recent years. In contrast, the use of the economic frame and morality frame fluctuated, both reaching peaks in the phase of 2007-2010 and decreasing in the most recent phase. Overall, the tone of the large majority of news articles was unfavorable, and the turning point occurred in the phase of 2007-2010 when the percentage of news articles with negative tone exceeded those with positive tone for the first time. Framing of e-cigarette news articles in China demonstrated the pivotal role of policy makers in defining the e-cigarette issue, and the influence of the international public health community, as an important and reliable information source, on defining the health risk of e-cigarettes, which has implication for not only e-cigarette control, but tobacco control in China in general.

Al2 O3 -Assisted Confinement Synthesis of Oxide/Carbon Hollow Composite Nanofibers and Application in Metal-Ion Capacitors.

Hollow micro-/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a "top-down" casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic-layer-deposition (ALD) Al2 O3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)-carbon composite hollow fibers after removal of Al2 O3 . Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni-based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as-obtained hollow V2 O3 -C fiber membrane is employed as a freestanding and flexible electrode for lithium-ion capacitor. The device shows an impressive energy density and a high power density.

Large-Area, Uniform, Aligned Arrays of Na3 (VO)2 (PO4 )2 F on Carbon Nanofiber for Quasi-Solid-State Sodium-Ion Hybrid Capacitors.

Sodium-vanadium fluorophosphate (Na3 V2 O2 x (PO4 )2 F3-2 x , NVPF, 0 ≤ x ≤ 1) is considered to be a promising Na-storage cathode material due to its high operation potentials (3.6-4 V) and minor volume variation (1.8%) during Na+ -intercalation. Research about NVPF is mainly focused on powder-type samples, while its ordered array architecture is rarely reported. In this work, large-area and uniform Na3 (VO)2 (PO4 )2 F cuboid arrays are vertically grown on carbon nanofiber (CNF) substrates for the first time. Owing to faster electron/ion transport and larger electrolyte-electrode contact area, the as-prepared NVPF array electrode exhibits much improved Na-storage properties compared to its powder counterpart. Importantly, a quasi-solid-state sodium-ion hybrid capacitor (SIHC) is constructed based on the NVPF array as an intercalative battery cathode and porous CNF as a capacitive supercapacitor anode together with the P(VDF-HFP)-based polymer electrolyte. This novel hybrid system delivers an attractive energy density of ≈227 W h kg-1 (based on total mass of two electrodes), and still remains as high as 107 Wh kg-1 at a high specific power of 4936 W kg-1 , which pushes the energy output of sodium hybrid capacitors toward a new limit. In addition, the growth mechanism of NVPF arrays is investigated in detail.

Mesopore-Induced Ultrafast Na+ -Storage in T-Nb2 O5 /Carbon Nanofiber Films toward Flexible High-Power Na-Ion Capacitors.

Hybrid Na-ion capacitors (NICs) are receiving considerable interest because they combine the merits of both batteries and supercapacitors and because of the low-cost of sodium resources. However, further large-scale deployment of NICs is impeded by the sluggish diffusion of Na+ in the anode. To achieve rapid redox kinetics, herein the controlled fabrication of mesoporous orthorhombic-Nb2 O5 (T-Nb2 O5 )/carbon nanofiber (CNF) networks is demonstrated via in situ SiO2 -etching. The as-obtained mesoporous T-Nb2 O5 (m-Nb2 O5 )/CNF membranes are mechanically flexible without using any additives, binders, or current collectors. The in situ formed mesopores can efficiently increase Na+ -storage performances of the m-Nb2 O5 /CNF electrode, such as excellent rate capability (up to 150 C) and outstanding cyclability (94% retention after 10 000 cycles at 100 C). A flexible NIC device based on the m-Nb2 O5 /CNF anode and the graphene framework (GF)/mesoporous carbon nanofiber (mCNF) cathode, is further constructed, and delivers an ultrahigh power density of 60 kW kg-1 at 55 Wh kg-1 (based on the total weight of m-Nb2 O5 /CNF and GF/mCNF). More importantly, owing to the free-standing flexible electrode configuration, the m-Nb2 O5 /CNF//GF/mCNF NIC exhibits high volumetric energy and power densities (11.2 mWh cm-3 , 5.4 W cm-3 ) based on the full device, which holds great promise in a wide variety of flexible electronics.

Integrating commercial graphite with network-like carbon fibers for high-rate and long-term cycling K+-storage.

K can reversibly intercalate into graphite by forming KC8 (279 mA h g-1, ≈0.2 V) in conventional carbonate electrolytes, but the large ionic radius of K+ (1.38 Å) easily results in structural degradation and rapid capacity decay. Here, commercial graphite particles are directly electrospun into network-like carbon fibers, thus forming a flexible Gr@CNF membrane. This hybrid electrode configuration can efficiently withstand the volume expansion during K+ insertion. K||Gr@CNF half-cells can stably operate for over 800 cycles (running time of 170 days at C/3) and achieve fast K+-intercalation kinetics at 5C. The fabricated Gr@CNF||AC K-ion hybrid capacitor delivers a high energy density of 119.3 W h kg-1 at 2717.82 W kg-1, corresponding to a fast-charge time of 3.2 min.

A Dual-Carbon Potassium-Ion Capacitor Enabled by Hollow Carbon Fibrous Electrodes with Reduced Graphitization.

The large size of K+ ions (1.38 Å) sets a challenge in achieving high kinetics and long lifespan of potassium storage devices. Here, a fibrous ZrO2 membrane is utilized as a reactive template to construct a dual-carbon K-ion capacitor. Unlike graphite, ZrO2-catalyzed graphitic carbon presents a relatively disordered layer arrangement with an expanded interlayer spacing of 0.378 nm to accommodate K+ insertion/extraction. Pyridine-derived nitrogen sites can locally store K-ions without disrupting the formation of stage-1 graphite intercalation compounds (GICs). Consequently, N-doped hollow graphitic carbon fiber achieves a K+-storage capacity (primarily below 1 V), which is 1.5 time that of commercial graphite. Potassium-ion hybrid capacitors are assembled using the hollow carbon fiber electrodes and the ZrO2 nanofiber membrane as the separator. The capacitor exhibits a high power of 40 000 W kg-1, full charge in 8.5 s, 93% capacity retention after 5000 cycles at 2 A g-1, and a low self-discharge rate of 8.6 mV h-1. The scalability and high performance of the lattice-expanded tubular carbon electrodes underscores may advance the practical potassium-ion capacitors.

Health belief model and social media engagement: A cross-national study of health promotion strategies against COVID-19 in 2020.

Background: Using the Health Belief Model (HBM), this study analyzed tweets related to COVID-19 published by national health departments of the United States, the South Korea, the United Kingdom, Japan, Germany, and India to explore their differences in (1) the health measures against COVID-19, (2) the health promotion strategies, (3) the social media engagements that those measures and strategies have triggered. Method: We conducted a content analysis with 1,200 randomly selected COVID-19-related tweets from six national health departments' Twitter accounts from 1 January 2020 to 31 December 2020. We coded the six HBM constructs and 21 sub-themes of the HBM constructs for each tweet. Results: Results showed that all six HBM constructs were used in the full sample. The most commonly used HBM construct was cues to action, followed by susceptibility, benefits, self-efficacy, severity, and barriers. All the HBM constructs were positively related to Twitter engagement variables except barriers. Further analysis illustrated that people from the six countries responded differently to the HBM constructs and the HBM sub-themes. Twitter users in Germany, India, the U.S., and Japan positively reacted to the clear directions of "what to do against COVID-19" (cues to action), while Twitter users in the U.S. and Japan were also eager to know the justifications for such directions (benefits); people in South Korea and the U.K. were mainly seeking a diagnosis of the severity and susceptibility of COVID-19, instead of health measures, of COVID-19 in the year 2020. Conclusions: This study showed the use of HBM constructs is generally effective in inducing Twitter engagement. The further comparison illustrated a homogenization in the promotion strategies that the health departments implemented and the health measures they promoted, yet responses to such promotions varied across nations. This study broadened the scope of HBM applications from predicting health behaviors in surveys to guiding the design of health promotion messages online.

A comparative study of public health and social measures of COVID-19 advocated in different countries.

Coronavirus 2019 (COVID-19) has had a significant impact on the world. Different countries introduced various public health and social measures (PHSMs) against the coronavirus. This paper aims to (a) examine how national policies on PHSMs were framed and which PHSMs were adopted; (b) compare the similarities and differences of PHSMs advocated by different countries; and (c) examine whether these measures have changed with time. We performed a content analysis of 160 COVID-19 policy documents on the websites of the WHO and ten countries' government websites on COVID-19 between December 1, 2019 and May 31, 2020. Results showed that although the initial responses to COVID-19 in different countries varied, there was a homogenization of PHSMs over time: by May 31, 2020, almost all the countries we studied implemented the major PHSMs that the WHO recommended, except Sweden, which applied only part of the major PHSMs recommended by the WHO. The differences among countries were in the speediness, strictness and resourcefulness of the PHSMs implementation. We suggest that a timely and effective utilization of the integrated package of health measures with the support of adequate resources may help the efficient implementation of PHSMs.