Search

Solid‐state lithium‐oxygen batteries (SSLOBs) offer high energy density with enhanced safety. However, the challenge of energy loss induced by the high polarization of the solid‐state air electrode has become a major bottleneck for its further development. Here, a homonuclear Fe‐Fe catalyst (Fe2‐N‐C) matched to reactants (Li2‐xO2, 0 ≤ x ≤ 2) size to alleviate the redox polarization in solid‐state electrodes is designed. Atomically resolved transmission electron microscopy reveals that the spatial size of Fe‐Fe clusters (1.5–2 Å) is commensurate with Li2‐xO2 (1.2–2.2 Å), which can overcome the challenges associated with catalyst/reactant size mismatch. In‐depth theoretical analyses show that orbital coupling and spin state jumping between Fe‐Fe sites allows the Fe centers to exhibit d‐orbital delocalization and high electronic spin states. These features enhance the activation of paramagnetic oxygen species, optimize the binding strength to LiO2 and reduce the charge/discharge voltage gap. Meanwhile, the size‐matching effect induces the ductile growth of the discharge product into a highly reversible film‐like morphology. The Fe2‐N‐C cathode with low overpotential exhibits significantly improved round‐trip efficiency (84.9%). The concept of this work opens up new opportunities for designing high‐performance SSLOBs. [ABSTRACT FROM AUTHOR]

Summary: Sodium‐ion hybrid capacitors are a prospective energy storage device candidate that couples the superiorities of battery‐type and capacitive storage mechanisms. In this study, we fabricate a composite of NiCo2O4 nanowires with carbon tubular bundles (CTBs) via a facile hydrothermal and annealing procedure. The density functional theory (DFT) calculations are performed to evaluate the bonding strength between the two components of the composite, the binding energy of the NiCo2O4 is calculated to be −0.952 J m−2, indicating that the NiCo2O4 nanowires can be stabilized on both sides of the carbon tubular bundles, which leads to a good cycling performance. Moreover, the composite in this work exhibits a metallic property because of the introduction of carbon material. As expected, when used for sodium storage, the NiCo2O4/CTBs shows a high capacity of 298 mA h g−1 at 1 A g−1 and high capacity retention of 92% after 500 cycles, which are superior than the bare NiCo2O4 electrode. Consequently, the sodium‐ion hybrid capacitor is also assembled with NiCo2O4/carbon tubular bundles and commercial activated carbon, which achieves high energy density of 99 Wh kg−1 in a wide potential range from 0.5 V to 4.0 V. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-intensity ultrasound (0.20 W·mL−1) enhanced partial nitrification stability. • Partial nitrification remained stable as the aeration rate gradually increased. • Nitrotoga activity recovery was inhibited under conditions of a high aeration rate. • The relative abundance of AOB (11.42 %) was much higher than that of NOB (0.85 %). • Ultrasonic treatment had an stripping effect on EPS, especially LB-EPS and PN. The fluctuation of dissolved oxygen is one of the primary cause of disruptions to the consistent operation of partial nitrification, and the level of dissolved oxygen is mainly controlled by the aeration rate. This study investigated the influence of ultrasonic treatment on the stability of partial nitrification of activated sludge under different aeration conditions. After being treated with ultrasound (energy density = 0.20 W·mL−1, treatment time = 10 min), partial nitrification process operated stably for 67 days, with the nitrite accumulation rate above 83.89 %. The effluent contained 42.50 mg·L−1 of nitrite, much higher than the control reactor (0.30 mg·L−1). The gap between the specific ammonia and nitrite oxidation rates widened continuously as the aeration rate increased, and nitrite-oxidizing bacteria activity did not recover even under conditions with a very high oxygen content. Further analysis showed that ultrasonic treatment had obvious stripping effect on excess extracellular polymeric substances (EPS), especially loosely bound EPS and protein. Additionally, long-term ultrasonic treatment promoted the enrichment of Nitrosomonas and strongly inhibited Nitrotoga. Based on these findings, it appears that under conditions of high aeration rate, ultrasound effectively suppress the recovery of Nitrotoga activity and improve the stability of partial nitrification. [ABSTRACT FROM AUTHOR]

Abstract: A micro-sized particle Li4Ti5−x La x O12 (0 ≤ x ≤ 0.2) material has been synthesized by a simple solid-state method at air. The obtained Li4Ti5−x La x O12 materials are Li3x La2/3−x TiO3 (LLTO)–Li4Ti5O12 (LTO) solid solution, and well crystallized with a particle size in the range of 1–2 μm. The electronic conductivity and lithium diffusion coefficient of La-modified LTO (Li4Ti4.95La0.05O12) are improved because LLTO exhibits a high ionic conductivity during Li+ extraction. Li4Ti4.95La0.05O12 material shows discharge capacities of more than 206 and 197 mAh g−1 after 100 cycles at 1 C and 3 C charge–discharge rates, respectively. Especially, in rate performance, the Li4Ti5−x La x O12 (x = 0.1, 0.2) samples maintain capacity of about 181 mAh g−1 until 5 C rates after 200 cycles, while the pure LTO sample shows a severe capacity decline at corresponding rate. These results suggest that La modifying is an effective way to improve the chemical stability of the electrode in contact with the electrolyte and improve their cyclability and rate capability during long term cycling. Since high rate performance is an important factor that needs to be considered in fabricating power batteries in industry, the La-modified LTO moves closer to real and large-scale applications. [Copyright &y& Elsevier]

Solid‐state lithium‐oxygen batteries (SSLOBs) offer high energy density with enhanced safety. However, the challenge of energy loss induced by the high polarization of the solid‐state air electrode has become a major bottleneck for its further development. Here, a homonuclear Fe‐Fe catalyst (Fe2‐N‐C) matched to reactants (Li2‐xO2, 0 ≤ x ≤ 2) size to alleviate the redox polarization in solid‐state electrodes is designed. Atomically resolved transmission electron microscopy reveals that the spatial size of Fe‐Fe clusters (1.5–2 Å) is commensurate with Li2‐xO2 (1.2–2.2 Å), which can overcome the challenges associated with catalyst/reactant size mismatch. In‐depth theoretical analyses show that orbital coupling and spin state jumping between Fe‐Fe sites allows the Fe centers to exhibit d‐orbital delocalization and high electronic spin states. These features enhance the activation of paramagnetic oxygen species, optimize the binding strength to LiO2 and reduce the charge/discharge voltage gap. Meanwhile, the size‐matching effect induces the ductile growth of the discharge product into a highly reversible film‐like morphology. The Fe2‐N‐C cathode with low overpotential exhibits significantly improved round‐trip efficiency (84.9%). The concept of this work opens up new opportunities for designing high‐performance SSLOBs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries appear to be one of the most promising energy-storage devices owing to the unparalleled theoretical specific energy, relatively inexpensive price and abundant resources. Despite these attractive features, the practical performances of sulfur cathode still remain a lot of challenges, such as the electrical insulating nature of S and Li 2 S, huge volume change during cycling, notorious shuttle effect of lithium polysulfide intermediates (LiPSs), sluggish redox kinetics and construction of thick electrodes with high sulfur loading. Here, CoFe 2 O 4 nanoparticles anchored on the carbon nanotube (CNT) paper is proposed as free-standing sulfur host to address the issues. The cross-linking CNT network can serve as conductive matrix and accommodate volume change upon cycling simultaneously. Meanwhile, the CoFe 2 O 4 nanoparticles are capable of effectively anchoring LiPSs to suppress the shuttle effect and accelerating LiPSs conversion to boost redox kinetics. Moreover, the free-standing paper electrode without any binder is conducive to constructing stable cathode with high sulfur loading. In consequence, the well-designed S/CoFe 2 O 4 /CNT paper cathodes deliver impressive electrochemical performance, demonstrating an initial discharge capacity of 755.3 mAh g−1 and remaining a high reversible capacity of 642.6 mAh g−1 after 400 cycles at 2 C with an inconspicuous decay of 0.04% per cycle. The bimetallic oxide CoFe 2 O 4 nanoparticles anchored on the carbon nanotube paper is proposed as free-standing sulfur host with enhanced polysulfide trapping and catalytic effects for advanced Li-S batteries. [Display omitted] • Binder-free host realizes high sulfur loading and energy density for Li-S battery. • CoFe 2 O 4 /CNT paper inhibits the polysulfide shuttling via strong chemical interaction. • CNT-anchored CoFe 2 O 4 catalytically promotes the polysulfide conversion kinetics. • The Li-S battery with S/CoFe 2 O 4 /CNT cathode exhibits enhanced capacity and stability. [ABSTRACT FROM AUTHOR]