Layered transition metal oxide (NaxTMO2), being one of the most promising cathode candidates for sodium‐ion batteries (SIBs), have attracted intensive interest because of their nontoxicity, high ...theoretical capacities, and easy manufacturability. However, their physical and electrochemical properties of water sensitivity, sluggish Na+ transport kinetics, and irreversible multiple‐phase translations hinder the practical application. Here, a concept of surface lattice‐matched engineering is proposed based on in situ spinel interfacial reconstruction to design a spinel coating P2/P3 heterostructure cathode material with enhanced air stability, rate, and cycle performance. The novel structure and its formation process are verified by transmission electron microscopy and in situ high‐temperature X‐ray diffraction. The electrode exhibits an excellent rate performance with the highly reversible phase transformation demonstrated by in situ charging/discharging X‐ray diffraction. Additionally, even after a rigorous water sensitivity test, the electrode materials still retain almost the same superior electrochemical performance as the fresh sample. The results show that the surface spinel phase can play a vital role in preventing the ingress of water molecules, improving transport kinetics, and enhancing structural integrity for NaxTMO2 cathodes. The concept of surface lattice‐matched engineering based on in situ spinel interfacial reconstruction will be helpful for designing new ultra‐stable cathode materials for high‐performance SIBs.
The formation process and function mechanism for inhibiting phase transformation and enhancing air stability of surface lattice‐matched engineering based on in situ spinel interfacial reconstruction are studied. This strategy of designing heterostructure with in situ interfacial reconstruction will inspire the exploitation of new chemistries and materials.
The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low ...sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g
with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g
at 100 mA g
after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g
at the high current density of 5 A g
. Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory.
Hard carbon (HC) anodes have shown extraordinary promise for sodium‐ion batteries, but are limited to their poor initial coulombic efficiency (ICE) and low practical specific capacity due to the ...large amount of defects. These defects with oxygen containing groups cause irreversible sites for Na+ ions. Highly graphited carbon decreases defects, while potentially blocking diffusion paths of Na+ ions. Therefore, molecular‐level control of graphitization of hard carbon with open accessible channels for Na+ ions is key to achieve high‐performance hard carbon. Moreover, it is challenging to design a conventional method to obtain HCs with both high ICE and capacity. Herein, a universal strategy is developed as manganese ions‐assisted catalytic carbonization to precisely tune graphitization degree, eliminate defects, and maintain effective Na+ ions paths. The as‐prepared hard carbon has a high ICE of 92.05% and excellent cycling performance. Simultaneously, a sodium storage mechanism of “adsorption‐intercalation‐pore filling‐sodium cluster formation” is proposed, and a clear description given of the boundaries of the pore structure and the specific dynamic process of pore filling.
Molecular‐level control of graphitization of hard carbon (HC) with open accessible channels for sodium ions by using manganese ions, is a novel strategy to obtain HC with both high capacity and high initial Coulombic efficiency (ICE). The as‐prepared hard carbon exhibits a high ICE of 92.05% and high reversible capacity (336.8 mAh g−1).
Room‐temperature sodium–sulfur (RT‐Na/S) batteries possess high potential for grid‐scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the ...low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur‐doped graphene frameworks supporting atomically dispersed 2H‐MoS2 and Mo1 (S@MoS2‐Mo1/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT‐Na/S batteries. Impressively, the as‐prepared S@MoS2‐Mo1/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g−1 at 0.1 A g−1 and a low‐capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X‐ray absorption spectroscopy, in situ synchrotron X‐ray diffraction and density‐functional theory calculations reveal that atomic‐level Mo in this integrated dual‐active‐site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high‐performance dual‐site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.
An integrated dual‐active‐site cathode is developed by wreathing monolayered MoS2 and Mo1 on sulfur‐doped graphene frameworks for high‐performance room‐temperature sodium–sulfur batteries. The constructed atomic level MoS2‐Mo1 with delocalized electron effects facilitates substantial charge transfer and a completely reversible reaction between S and Na, thus alleviating the shuttle effect.
Electrochemical production of H
2
O
2
from O
2
using simulated seawater provides a promising alternative to the energy-intensive industrial anthraquinone process. In this study, a flow cell system is ...built for electrocatalytic production of H
2
O
2
under an air atmosphere in simulated seawater using cobalt single-atom catalysts (Co SACs). The Co SACs can achieve a high H
2
O
2
production rate of 3.4 mol g
catalyst
−1
h
−1
under an air flow at a current density of 50 mA cm
geo
−2
and long-term stability over 24 h in 0.5 M NaCl. It is found that Co-N
5
rather than the Co-N
4
structure in Co SACs is the main active site for H
2
O
2
formation in the two-electron oxygen reduction reaction (ORR) pathway. It also shows high chloride-endurability without inhibition of the ORR process in simulated seawater. The fast production of H
2
O
2
on Co-N
5
sites in a flow cell provides a promising path of electrocatalytic oxygen reduction in simulated seawater, eventually converting ubiquitous air and seawater towards energy sustainability.
Sustainable production of H
2
O
2
is boosted by oxygen reduction reaction on Co-N
5
sites in a flow cell in simulated seawater.
Both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial to water splitting, but require alternative active sites. Now, a general π‐electron‐assisted strategy to ...anchor single‐atom sites (M=Ir, Pt, Ru, Pd, Fe, Ni) on a heterogeneous support is reported. The M atoms can simultaneously anchor on two distinct domains of the hybrid support, four‐fold N/C atoms (M@NC), and centers of Co octahedra (M@Co), which are expected to serve as bifunctional electrocatalysts towards the HER and the OER. The Ir catalyst exhibits the best water‐splitting performance, showing a low applied potential of 1.603 V to achieve 10 mA cm−2 in 1.0 m KOH solution with cycling over 5 h. DFT calculations indicate that the Ir@Co (Ir) sites can accelerate the OER, while the Ir@NC3 sites are responsible for the enhanced HER, clarifying the unprecedented performance of this bifunctional catalyst towards full water splitting.
HER and OER! The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial to water splitting, but require alternative active sites. Now, a general π‐electron‐assisted strategy to anchor single‐atom sites (M=Ir, Pt, Ru, Pd, Fe, Ni) on a heterogeneous support is reported. The M atoms can simultaneously anchor on two distinct domains of the hybrid support, four‐fold N/C atoms, and centers of Co octahedra.
Tumor complexity makes the development of highly sensitive tumor imaging probes an arduous task. Here, we construct a peptide‐based near‐infrared probe that is responsive to fibroblast activation ...protein‐α (FAP‐α), and specifically forms nanofibers on the surface of cancer‐associated fibroblasts (CAFs) in situ. The assembly/aggregation‐induced retention (AIR) effect results in enhanced accumulation and retention of the probe around the tumor, resulting in a 5.5‐fold signal enhancement in the tumor 48 h after administration compared to that of a control molecule that does not aggregate. The probe provides a prolonged detectable window of 48 h for tumor diagnosis. The selective assembly of the probe results in a signal intensity over four‐ and fivefold higher in tumor than in the liver and kidney, respectively. With enhanced tumor imaging capability, this probe can visualize small tumors around 2 mm in diameter.
Image of health: A peptide probe labeled with a near‐infrared dye has been developed that can be specifically tailored with a fibroblast activation protein‐α and then self‐assembled in situ into nanofibers on the surface of cancer‐associated fibroblasts. The selective assembly of the probe has resulted in tumor imaging with high sensitivity and specificity, with tumors as small as 2 mm in diameter visualized.
Recently LHCb declared a new structure
X
(6900) in the final state di-
J
/
ψ
which is popularly regarded as a
cc
-
c
¯
c
¯
tetraquark state. Within the Bethe–Salpeter (B–S) framework we study the ...possible
cc
-
c
¯
c
¯
bound states and the interaction between diquark (
cc
) and antidiquark (
c
¯
c
¯
). In this work
cc
(
c
¯
c
¯
) is treated as a color anti-triplet (triplet) axial-vector so the quantum numbers of
cc
-
c
¯
c
¯
bound state are
0
+
,
1
+
and
2
+
. Learning from the interaction in meson case and using the effective coupling we suggest the interaction kernel for the diquark and antidiquark system. Then we deduce the B–S equations for different quantum numbers. Solving these equations numerically we find the spectra of some excited states can be close to the mass of
X
(6900) when we assign appropriate values for parameter
κ
introduced in the interaction (kernel). We also briefly calculate the spectra of
bb
-
b
¯
b
¯
bound states. Future measurement of
bb
-
b
¯
b
¯
state will help us to determine the exact form of effective interaction.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Hard carbon (HC) is recognized as a promising anode material with outstanding electrochemical performance for alkali metal‐ion batteries including lithium‐ion batteries (LIBs), as well as their ...analogs sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs). Herein, a comprehensive review of the recent research is presented to interpret the challenges and opportunities for the applications of HC anodes. The ion storage mechanisms, materials design, and electrolyte optimizations for alkali metal‐ion batteries are illustrated in‐depth. HC is particularly promising as an anode material for SIBs. The solid‐electrolyte interphase, initial Coulombic efficiency, safety concerns, and all‐climate performances, which are vital for practical applications, are comprehensively discussed. Furthermore, commercial prototypes of SIBs based on HC anodes are extensively elaborated. The remaining challenges and research perspectives are provided, aiming to shed light on future research and early commercialization of HC‐based SIBs.
Hard carbon (HC) is recognized as a promising anode material for alkali‐metal ion batteries, especially for sodium‐ion batteries (SIBs) which are cost effective for grid‐scale energy storage. This review aims for a comprehensive understanding of alkali‐metal ion storage mechanisms in HC, and also rational approaches to enhance the performance of HC anodes for practical SIBs.
Hard carbon anodes with all-plateau capacities below 0.1 V are prerequisites to achieve high energy density sodium ion storages, which are holding promises for the future sustainable energy ...technologies. However, challenges in removing defects and improving the insertion of sodium ions heading off the development of hard carbon to achieve this goal. Herein, we reported a highly cross-linked topological graphitized carbon using biomass corn cobs through a two-step rapid thermal annealing strategy. The topological graphitized carbon constructed with long-range graphene nanoribbons and cavities/tunnels provides a multi-directional insertions of sodium ions whilst eliminating defects to absorb sodium ions at high voltage region. Evidences from advanced technique including in-situ XRD, in-situ Raman and in-situ/ex-situ TEM indicate that the sodium ions appear Na cluster formation between curved topological graphite layers and in the topological cavity of adjacent graphite band entanglements. The reported topological insertion mechanism enables outstanding battery performance with a single full low-voltage plateau capacity of 290 mAh g
, which is almost 97% of the total capacity. This article is protected by copyright. All rights reserved.
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