Sodium‐ion batteries (SIBs) have attracted tremendous interest and become a worldwide research hotpot owing to their low cost and abundant resources. To obtain suitable anode materials with excellent ...performance for SIBs, an effective and controllable strategy is presented to fabricate SnS2 nanosheets coating on nanohollow cubic CoS2/C (CoS2/C@SnS2) composites with a hollow structure using Co‐metal‐organic frameworks as the starting material. As anodes for SIBs, the CoS2/C@SnS2 electrode exhibits ultralong cycle life and excellent rate performance, which can maintain a high specific capacity of 400.1 mAh g−1 even after 3500 cycles at a current density of 10 A g−1. When used in a full‐cell, it also shows enhanced sodium storage properties and delivers a high reversible capacity of 567.3 mAh g−1 after 1000 cycles at 1 A g−1. This strategy can pave a way for preparing various metal sulfides with fascinating structure and excellent performance for the potential application in energy storage area.
The CoS2/C@SnS2 exhibits ultralong cycle life and high rate capability. The reversible capacity can maintain 854.5 mAh g−1 at a current density of 0.1 A g−1. Even at a high current density of 10 A g−1, the reversible capacity can maintain 400.1 mAh g−1 after 3500 cycles. As for CoS2/C@SnS2‐Na3V2(PO4)3 full‐cells, one full‐cell can light up 41 light‐emitting diodes bulbs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, ...dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields.
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IJS, KILJ, NUK, PNG, UL, UM
Gel electrolytes are promising candidates for fulfilling the performance and safety requirements of a new generation of lithium-ion battery technologies owing to their quasi-solid-state and ...ameliorated mechanical strength. However, there is a dilemma that requires the sacrifice of the ionic conductivity in exchange for mechanical strength. Here, a mechanically robust ionogel polymer electrolyte (IGPE) is explored to overcome this plight. The IGPE film is prepared by the nonsolvent induced phase separation method, and the obtained optimal flexible IGPE-5 sample exhibits robust mechanical strength with 178% elongation at break and 6.65 MPa breaking strength. In addition, the IGPE-5 presents a high ionic conductivity of 0.80 mS cm−1 at 25 °C, a wide electrochemical stability window of 4.7 V and high thermal stability up to 220 °C. The LiFePO4/IGPE-5/Li cell displays initial discharge capacity of 161.9 mAh g−1 and a capacity retention of 94.5% after 200 cycles at 0.5C at 55 °C. The IGPE-5-based flexible battery can withstand bending and cutting tests, indicating that the excellent flexibility and interface compatibility of IGPE-5.
•Mechanically robust ionogel polymer electrolyte was prepared by NIPS method.•Excellent flexibility and interface compatibility.•The battery shows excellent performance at both room and elevated temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
FeNC catalysts demonstrate remarkable activity and stability for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells and Zn–air batteries (ZABs). The local coordination ...of Fe single atoms in FeNC catalysts strongly impacts ORR activity. Herein, FeNC catalysts containing Fe single atoms sites with FeN3, FeN4, and FeN5 coordinations are synthesized by carbonization of Fe‐rich polypyrrole precursors. The FeN5 sites possess a higher Fe oxidation state (+2.62) than the FeN3 (+2.23) and FeN4 (+2.47) sites, and higher ORR activity. Density functional theory calculations verify that the FeN5 coordination optimizes the adsorption and desorption of ORR intermediates, dramatically lowering the energy barrier for OH− desorption in the rate‐limiting ORR step. A primary ZAB constructed using the FeNC catalyst with FeN5 sites demonstrates state‐of‐the‐art performance (an open circuit potential of 1.629 V, power density of 159 mW cm−2). Results confirm an intimate structure‐activity relationship between Fe coordination, Fe oxidation state, and ORR activity in FeNC catalysts.
FeNC catalysts with different Fe single‐atom coordination geometries (FeN3, FeN4, or FeN5) are synthesized by pyrolysis of Fe‐polypyrrole precursors. FeN5 sites offer the highest Fe oxidation state (+2.62), strongest Fe–N interaction, lowest energy barrier for OH− desorption, and highest intrinsic activity for oxygen reduction reaction in alkaline media.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To develop efficient and low-cost bifunctional electrocatalysts towards oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is vital for the progress of fuel cell, Zn-air battery ...and overall water splitting. Herein, a facial method to prepare Co nanoparticles-embedded N, S-codoped hierarchically micro/meso/macroporous graphene sheets (Co@NSCs) via pyrolysis of the mixture of urea, l-cysteine, polyethylene glycol and cobalt (II) nitrate is reported. By controlling the pyrolysis temperature, Co@NSC-1000 obtained at 1000 °C performs comparable electrochemical activity on ORR and HER, with commercial Pt/C. Additionally, Co@NSC-1000 also exhibits acceptable methanol resistance on ORR and admissible long-term durability on ORR and HER after 5000 potential cycles. Synergistically, hierarchically micro/meso/macroporous nanostructure, non-precious Co nanoparticles, and N, S-codoped graphene are greatly contributed to the high electrocatalytic activity and stability. The pyrolysis temperature is the key factor for tailoring element component, nanostructure and electrochemical activities. The competitive catalytic performances on ORR and HER indicate Co@NSC-1000 is a hopeful substitute for noble benchmark Pt catalysts. Furthermore, Zn-air battery assembled with Co@NSC-1000 shows higher specific capacity, larger energy density and stronger stability than Pt/C, holding great potential in practical applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•UHMWPE pre-stretched fibers were examined by in situ SAXS/WAXD during the ultra-high stretching process.•We reported the transition from shish-kebab to fibrillar morphology crystals ...of UHMWPE fibers.•There still exist chain conformation defects even in the majorly fibrillar morphology crystals.
The ultra-high hot stretching was conducted on four-times pre-stretched ultra-high molecular weight polyethylene (UHMWPE) fibers to the ratio of about 508% to achieve the total ultra-high stretching ratio of about 2000%. In situ small and wide-angle X-ray scattering (SAXS/WAXS) measurements using synchrotron radiation and Raman spectroscopy were applied to study the structural evolutions of ultra-high stretched fibers. SAXS images revealed the transition from shish-kebab to fibrillar crystals, which is believed to involve with the increasing trans-configuration ratio of C–C backbone. WAXS results demonstrate the further stretching could still be applied to the fibers to acquire the complete extended-chain crystals.
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The quality of polyacrylonitrile (PAN) precursor has a great influence on the properties of the resultant carbon fibers. In this paper, a novel comonomer containing the sulfonic group, ...2-acrtlamido-2-methylpropane acid (AMPS), was introduced to prepare P(AN-co-AMPS) copolymers using itaconic acid (IA) as the control. The nanofibers of PAN, P(AN-co-IA), and P(AN-co-AMPS) were prepared using the electrospinning method. The effect of AMPS comonomer on the carbon nanofibers was studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Raman spectrum. The structural evolutions of PAN-based nanofibers were quantitatively tracked by FTIR and XRD during the thermal oxidative stabilization (TOS) process. The results suggested that P(AN-co-AMPS) nanofibers had the lower heat release rate (Δ
Δ
= 26.9 J g
°C
), the less activation energy of cyclization (
= 26.6 kcal/mol and
= 27.5 kcal/mol), and the higher extent of stabilization (
and
) during TOS process, which demonstrated that the AMPS comonomer improved the efficiency of the TOS process. The P(AN-co-AMPS) nanofibers had the better thermal stable structures. Moreover, the carbon nanofibers derived from P(AN-co-AMPS) precursor nanofibers had the better graphite-like structures (
= 46.889). Therefore, the AMPS is a promising candidate comonomer to produce high performance carbon fibers.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Tassieri et al. have introduced a novel rheological tool called "i-Rheo
" that allows the evaluation of the frequency-dependent materials' linear viscoelastic properties from a direct Fourier ...transform of the time-dependent relaxation modulus
(
), without artifacts. They adopted i-Rheo
to exploit the information embedded in
(
) derived from molecular dynamics simulations of atomistic and quasi-atomistic models, and they estimated the polymers' entanglement characteristic time (τe) from the crossover point of the moduli at intermediate times, which had never been possible before because of the poor fitting performance, at short time scales, of the commonly used generalized Maxwell models. Here, we highlight that the values of τe reported by Tassieri et al. are significantly different (i.e., an order of magnitude smaller) from those reported in the literature, obtained from either experiments or molecular dynamics simulations of different observables. In this work, we demonstrate that consistent values of τe can be achieved if the initial values of
(
), i.e., those governed by the bond-oscillation dynamics, are discarded. These findings have been corroborated by adopting i-Rheo
to Fourier transform the outcomes of three different molecular dynamics simulations based on the following three models: a dissipative particle dynamics model, a Kremer-Grest model, and an atomistic polyethylene model. Moreover, we have investigated the variations of τe as function of (i) the 'cadence' at which
(
) is evaluated, (ii) the spring constant of the atomic bone, and (iii) the initial value of the shear relaxation modulus
(O). The ensemble of these results confirms the effectiveness of i-Rheo
and provide new insights into the interpretation of molecular dynamics simulations for a better understanding of polymer dynamics.
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Photosensitive precursors are developed for the printing of 2D and 3D conductive structures via blue laser projection printing. With the assistance of a photosensitizer, metal nanoparticles can be ...efficiently photosynthesized under laser irradiation of low light intensity (45–290 mW cm–2). By projecting well-defined laser patterns on the precursor, corresponding 2D metal structures with the finest line of about 50 μm can be formed on various substrates including flexible polymer thin films, curved substrates, and ground glass. Moreover, complex 3D objects with nanoparticles embedded in the polymeric matrix are constructed via 3D printing combining photoreduction of the metal precursor and photopolymerization of resin. The as-prepared structures exhibit promising conductivities after sintering (in the order of magnitude of 106 S m–1). A possible mechanism of photochemical synthesis of metal nanoparticles upon exposure to blue laser is proposed. The high efficiency and low cost of the technique, the complexity of the structures prepared, and the applicability to various substrates and metals (including silver, gold, and palladium) promise practical applications of this approach in the printed electronics industry.
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Developing highly efficient oxygen evolution reaction (OER) catalyst for the acidic corrosive operating conditions is a challenging task. Herein, we report the synthesis of uniform RuO
2
clusters ...with ∼ 2 nm in size via electrochemical leaching of Sr from SrRuO
3
ceramic in acid. The RuO
2
clusters exhibit ultrahigh OER activity with overpotential of ∼ 160 mV at 10 mA·cm
geo
−2
in 1.0 M HClO
4
solution for 30-h testing. The extended X-ray absorption fine structure measurement reveals enlarged Jahn-Teller distortion of RuO octahedra in the RuO
2
clusters compared to its bulk counterpart. Density function theory calculations show that the enhanced Jahn-Teller distortion can improve the intrinsic OER activity of RuO
2
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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