A honeycomb layered Na3Ni2SbO6 is synthesized as a cathode for sodium‐ion batteries. This new host material exhibits a high capacity of 117 mA h g−1, a remarkable cyclability with 70% capacity ...retention over 500 cycles at a 2C rate, and a superior rate capability with >75% capacity delivered even at a very high rate of 30 C (6000 mA g−1). These results open a new perspective to develop high‐capacity and high‐rate Na‐ion batteries for widespread electric‐energy‐storage applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Hard carbon is one of the most promising anode materials for sodium‐ion batteries, but the low Coulombic efficiency is still a key barrier. In this paper, a series of nanostructured hard carbon ...materials with controlled architectures is synthesized. Using a combination of in situ X‐ray diffraction mapping, ex situ nuclear magnetic resonance (NMR), electron paramagnetic resonance, electrochemical techniques, and simulations, an “adsorption–intercalation” mechanism is established for Na ion storage. During the initial stages of Na insertion, Na ions adsorb on the defect sites of hard carbon with a wide adsorption energy distribution, producing a sloping voltage profile. In the second stage, Na ions intercalate into graphitic layers with suitable spacing to form NaC
x
compounds similar to the Li ion intercalation process in graphite, producing a flat low voltage plateau. The cation intercalation with a flat voltage plateau should be enhanced and the sloping region should be avoided. Guided by this knowledge, nonporous hard carbon material has been developed which has achieved high reversible capacity and Coulombic efficiency to fulfill practical application.
An “adsorption–intercalation” (A–I) mechanism is established for Na ion storage by using a combination of in situ X‐ray diffraction mapping, ex situ electron paramagnetic resonance, electrochemical techniques, and simulations. The “A–I” mechanism means that Na ions adsorb on the defect sites of hard carbon producing a sloping voltage profile and subsequently intercalate into graphitic layers producing a flat low voltage plateau in the second stage.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A novel and facile method for surface acetylation of cellulose nanocrystals (CN) was developed by reaction with acetic anhydride and hydroxyl groups on the surface of CN. The resultant acetylated ...cellulose nanocrystals (ACN) exhibited improved dispersion in various organic solvents and reduced polarity as compared with unmodified CN. These ACN were subsequently introduced into a poly(lactic acid) (PLA) polymeric matrix to produce fully biodegradable nanocomposites, which showed superior mechanical performance and thermal stability. This improvement was primarily attributed to uniform dispersion of the ACN and to strong interfacial adhesion between filler and matrix. This high performance and eco-friendly nanocomposite will expand the utilization of cellulose nanocrystals from renewable bioresources and the practical application of PLA-based plastic.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Sodium superionic conductors are keys to develop high safety and low cost all-solid-state sodium batteries. Among developed sodium ionic conductors, antiperovskite-type ionic conductors have ...attracted vast interest due to their high structural tolerance and good formability. Herein, we successfully synthesize Na3OBH4 with cubic antiperovskite structure by solid-state reaction from Na2O and NaBH4. Na3OBH4 exhibits ionic conductivity of 4.4 × 10–3 S cm–1 at room temperature (1.1 × 10–2 S cm–1 at 328 K) and activation energy of 0.25 eV. The ionic conductivity is 4 orders of magnitude higher than the existing antiperovskite Na3OX (X = Cl, Br, I). It is shown that such enhancement is not only due to the specific cubic antiperovskite structure of Na3OBH4 but also because of the rotation of BH4 cluster anion. This work deepens the understanding of the antiperovskite structure and the role of cluster anions for superionic conduction.
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IJS, KILJ, NUK, PNG, UL, UM
1H MAS NMR spectroscopy has been applied to study the urea effect on phase transition of two similar thermosensitive polymer hydrogels: poly(N-isopropylacrylamide) (PNIPAM) and ...poly(N,N-diethylacrylamide) (PDEA). It is found that urea influences the phase transition of the hydrogels in opposite ways: lowering the lower critical solution temperature (LCST) of PNIPAM and hence stabilizing its globular structure, whereas raising the LCST of PDEA and destabilizing the globular structure. The self-diffusion coefficient and urea–polymer nuclear Overhauser effect (NOE) measurement reveal that urea has a stronger interaction with PNIPAM than with PDEA. Moreover, the enhanced positive water–PNIPAM NOE suggests that urea not only interacts directly with PNIPAM via hydrogen bond but also intensifies the hydrogen bonding interaction between water and PNIPAM. We suggest that different urea–polymer hydrogen bonding interaction due to the presence or absence of amide hydrogen is correlated with the distinct LCST variation of PNIPAM and PDEA.
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IJS, KILJ, NUK, PNG, UL, UM
Current battery systems have severe cost and resource restrictions, difficultly to meet the large scale electric storage applications. Herein, we report an all-organic Na-ion battery using p-dopable ...polytriphenylamine as cathode and n-type redox-active poly(anthraquinonyl sulphide) as anode, excluding the use of transition-metals as in conventional electrochemical batteries. Such a Na-ion battery can work well with a voltage output of 1.8 V and realize a considerable specific energy of 92 Wh kg(-1). Due to the structural flexibility and stability of the redox-active polymers, this battery has a superior rate capability with 60% capacity released at a very high rate of 16 C (3200 mA g(-1)) and also exhibit an excellent cycling stability with 85% capacity retention after 500 cycles at 8 C rate. Most significantly, this type of all-organic batteries could be made from renewable and earth-abundant materials, thus offering a new possibility for widespread energy storage applications.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Li10GeP2S12 (LGPS) is a new solid electrolyte of the highest Li ionic conductivity reported as of now. An anisotropic 3D Li ionic transport network consisting of an ultrafast Li 1D diffusion tunnel ...and fast in-plane 2D pathways was previously predicted by molecular dynamics simulations. In this paper, we have studied in detail the Li ion dynamics in LGPS by multiple solid-state NMR methods. Two different Li motion processes, characterized by apparently different activation energies of 0.16 eV and 0.26 eV, were unambiguously probed by both 7Li and 31P solid-state NMR and assigned to Li ion diffusions in the 1D tunnel and in the 2D plane, respectively. 31P spin-locking relaxation measurement further reveals that interstitial position Li(4) is active for in-plane Li migration.
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IJS, KILJ, NUK, PNG, UL, UM
β-1,3-glucans are a kind of natural polysaccharide with immunomodulatory, antitumor, and anti-inflammatory properties. Curdlan, as the simplest linear β-1,3-glucan, possesses a variety of biological ...activities and thermogelation properties. However, due to the complexity and variability of the conformations of curdlan, the exact structure-activity relationship remains unclear. We prepare a chemically crosslinked curdlan hydrogel with the unique single-helical skeleton (named S gel) in 0.4 wt% NaOH at 40 °C, confirmed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). X-ray diffractometry (XRD) data show that S gel maintains the single-helical crystal structure, and the degree of crystallinity of the S gel is ~24%, which is slightly lower than that of the raw powder (~31%). Scanning electron microscopy (SEM) reveals that S gel has a continuous network structure, with large pores measuring 50-200 μm, which is consistent with its high swelling property. Using the
C high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) method, we determine that most of the single-helical skeleton carbon signals in the swollen S gel are visible, suggesting that the single-helical skeleton of S gel exhibits fascinating mobility at room temperature. Finally, we reveal that the binding of S gel to coagulation Factor G from tachypleus amebocyte lysate increases and saturates at 20 μL tachypleus amebocyte lysate per mg of S gel. Our prepared S gel can avoid the transformation of curdlan conformations and retain the bioactivity of binding to coagulation Factor G, making it a valuable material for use in the food industry and the pharmaceutical field. This work deepens the understanding of the relationship between the single-helical structure and the activity of curdlan, promoting the development and application of β-1,3-glucans.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The phase separation of poly(N,N-diethylacrylamide) (PDEA) gel network in water/alcohol (methanol, ethanol, isopropanol, and n-propanol) mixtures has been systematically investigated by ...variable-temperature high-resolution 1H MAS NMR. The PDEA gel exhibits the cononsolvency effect and reentrant phase transition in water/isopropanol and water/n-propanol mixtures with larger alcohol hydrophobic groups but not in the water/methanol and water/ethanol bearing smaller alcohol hydrophobic groups, in contrast to the case of poly(N-isopropylacrylamide) where the cononsolvency effect was observed in all water/alcohol solutions. In the present PDEA gel, the phase separation is characterized by dehydration of the hydrophobic alkyl groups of PDEA, resulting in two distinct types of water/alcohol solutions above the lower critical solution temperature: confined binary solvents (3–5 solvent molecules per PDEA repeating unit) inside the gel network and free binary solvents outside the gel. The alcohol concentration in confined mixture solvents is markedly higher than that in free mixture solvents and increases with increasing hydrophobicity of the alcohol moiety. Interestingly, the alcohol enrichment inside the shrunk network does not cause additional dehydration of the PDEA network. Besides, the side chain mobility of shrunk PDEA gel network is enhanced by the appearance of alcohol and increases with the hydrophobicity of alcohol moiety. Our results reveal that there exists a strong interaction between alcohol and gel network.
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IJS, KILJ, NUK, PNG, UL, UM
Two novel indolo3,2-bcarbazole-based metal-free organic dyes (D1 and D2) have been synthesized. The substituted position on the second donor indolo3,2-bcarbazole plays the important roles in tuning ...the photoelectronic properties and controlling the self-aggregation of dyes on photoanode.
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•Two new indolo3,2-bcarbazole-based metal-free organic dyes were synthesized.•The best power conversion efficiency (PCE) of 6.34% is obtained by the dye D2.•The co-sensitization of D1 and D2 further improves the PCE up to 7.03%.
Two new indolo3,2-bcarbazole-based metal-free organic dyes (D1 and D2) were synthesized by utilizing triphenylamine as the first donor which were connected to the second donor indolo3,2-bcarbazole via 9-position and 8-position, respectively. The dyes were characterized by UV–visible absorption spectra and electrochemical analyses. The both two dyes showed intensive absorption spectra in the wavelength of 300–600 nm and narrow band gap of 2.29 eV for D1 and 2.16 eV for D2. The cyclic voltammetry indicated that the oxidative potentials and reductive potentials of the dyes were well matched with the energy levels of the I−/I3− redox couple and TiO2 conduction band, respectively. The substituted positions on the indolo3,2-bcarbazole played important roles in tuning the photoelectronic properties. The dye D2 with 2, 8-substituted indolo3,2-bcarbazole core shows wider absorption spectrum and lower dye aggregation than D1 with 3,9-substituted isomer. The best power conversion efficiency (PCE) of 6.34% is obtained by the dye D2 due to its wider absorption spectra and strong steric hindrance, which can effectively suppress the undesirable dye aggregation. The co-sensitization of D1 and D2 enhances IPCE response in the visible light region and further improves the PCE up to 7.03%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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