Although lithium–sulfur (Li–S) batteries are promising next‐generation energy‐storage systems, their practical applications are limited by the growth of Li dendrites and lithium polysulfide ...shuttling. These problems can be mitigated through the use of single‐atom catalysts (SACs), which exhibit the advantages of maximal atom utilization efficiency (≈100%) and unique catalytic properties, thus effectively enhancing the performance of electrode materials in energy‐storage devices. This review systematically summarizes the recent progress in SACs intended for use in Li‐metal anodes, S cathodes, and separators, briefly introducing the operating principles of Li–S batteries, the action mechanisms of the corresponding SACs, and the fundamentals of SACs activity, and then comprehensively describes the main strategies for SACs synthesis. Subsequently, the applications of SACs and the principles of SACs operation in reinforced Li–S batteries as well as other metal–S batteries are individually illustrated, and the major challenges of SACs usage in Li–S batteries as well as future development directions are presented.
The cycling stability and rate performance of Li–S batteries are adversely affected by the formation of Li dendrites and the polysulfide shuttle effect. Single‐atom catalysts (SACs) can effectively guide Li deposition and suppress polysulfide migration, thus holding great promise for Li–S batteries. The recent progress in the development of SACs for Li–S batteries is systematically summarized and analyzed.
Lithium–sulfur (Li–S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the “shuttle effect” of the sulfur ...cathode, resulting in poor cyclic performance, is a big barrier for the development of Li–S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal–organic framework (MOF)‐derived N‐doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm–2) and exhibit large specific capacities at different C‐rates. Specially, an outstanding long‐term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high‐energy‐density Li–S batteries.
A flexible sulfur cathode integrating sulfur, flexible carbon cloth, and N‐doped carbon nanoarrays with embedded CoP is successfully designed. Due to the artful structure and synergistic confinement for soluble lithium polysulfides, it displays an outstanding long‐term cycling performance and an ultralow decay of 0.016% per cycle during the whole 600 cycles at 2C.
This review elaborately summarized the recent progress of solid-state composite cathodes, including interface issues, material design, preparation methods and characterization techniques, which ...provides valuable experience for understanding and engineering composite cathode of all-solid-state lithium batteries.
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All-solid-state lithium battery (ASLB) based on sulfide-based electrolyte is considered to be a candidate for the next-generation high-energy storage system. Despite the high ionic conductivity of sulfide solid electrolyte, the poor interfacial stability (mechanically and chemically) between active materials and sulfide solid electrolytes in composite cathodes leads to inferior electrochemical performances, which impedes the practical application of sulfide electrolytes. In the past years, various of strategies have been carried out to achieve an interface with low impedance in the composite cathodes. Herein, a review of recent progress of composite cathodes for all-solid-state sulfide-based lithium batteries is summarized, including the interfacial issues, design strategies, fabrication methods, and characterization techniques. Finally, the main challenges and perspectives of composite cathodes for high-performance all-solid-state batteries are highlighted for future development.
Recently, Li‐ion batteries (LIBs) have attracted extensive attention owing to their wide applications in portable and flexible electronic devices. Such a huge market for LIBs has caused an ...ever‐increasing demand for excellent mechanical flexibility, outstanding cycling life, and electrodes with superior rate capability. Herein, an anode of self‐supported Fe3O4@C nanotubes grown on carbon fabric cloth (CFC) is designed rationally and fabricated through an in situ etching and deposition route combined with an annealing process. These carbon‐coated nanotube structured Fe3O4 arrays with large surface area and enough void space can not only moderate the volume variation during repeated Li+ insertion/extraction, but also facilitate Li+/electrons transportation and electrolyte penetration. This novel structure endows the Fe3O4@C nanotube arrays stable cycle performance (a large reversible capacity of 900 mA h g−1 up to 100 cycles at 0.5 A g−1) and outstanding rate capability (reversible capacities of 1030, 985, 908, and 755 mA h g−1 at 0.15, 0.3, 0.75, and 1.5 A g−1, respectively). Fe3O4@C nanotube arrays still achieve a capacity of 665 mA h g−1 after 50 cycles at 0.1 A g−1 in Fe3O4@C//LiCoO2 full cells.
Flexible batteries: Uniform Fe3O4@C nanotube arrays are fabricated successfully through a facile in situ etching and deposition route, combined with annealing treatment. Owing to the unique carbon‐encapsulated nanotube arrays design, this free‐standing Fe3O4@C anode can effectively palliate the volume variation, reduce the diffusion distance of Li+, and thus, promote the electrochemical reaction kinetics, thereby achieving a superior rate capability and stable cycling performance.
The pursuit of high-mileage models results in the recurrence of lithium metal batteries (LMBs) to researchers’ horizon. However, the lithium (Li) metal anode for LMBs undergoes the uncontrollable ...formation of Li dendrites and infinite volume change during cycling, impeding its practical application. To overcome these challenges, we developed a metal-organic framework (MOF)-derived pathway to construct lithiophilic three-dimensional (3D) skeleton using different substrates (e.g., carbon cloth (CC) and Cu mesh) for dendrite-free lithium metal anodes. As a typical example, the MOF-derived ZnO/nitrogen-doped carbon (NC) nanosheet-modified 3D CC was well-constructed as a lithiophilic hierarchical host (CC@ZnO/NC@Li) for molten Li infiltration. Benefiting from the lithiophilic N-functional groups and LiZn alloy, the synthesized CC@ZnO/NC@Li composite anode promoted the uniform distribution of Li, resulting in a dendrite-free morphology. Meanwhile, the 3D conductive carbon skeleton enhanced the reaction kinetics and buffered the volume change of the electrode. The CC@ZnO/NC@Li composite anode presented a prolonged lifespan of over 1000 cycles at 5 mA cm
−2
with a low overpotential of 19 mV. Coupled with a LiFePO
4
cathode, the CC@ZnO/NC@Li composite anode also exhibited superior electrochemical properties in the full-cell system. This versatile strategy may open up the channel of designing multi-functional lithiophilic 3D hosts for the Li metal anode.
Currently, the construction of amorphous/crystalline (A/C) heterophase has become an advanced strategy to modulate electronic and/or ionic behaviors and promote structural stability due to their ...concerted advantages. However, their different kinetics limit the synergistic effect. Further, their interaction functions and underlying mechanisms remain unclear. Here, a unique engineered defect‐rich V2O3 heterophase structure (donated as A/C‐V2O3−x@C‐HMCS) composed of mesoporous oxygen‐deficient amorphous − hollow core (A‐V2O3−x/HMC) and lattice‐distorted crystalline shell (C‐V2O3/S) encapsulated by carbon is rationally designed via a facile approach. Comprehensive density functional theory (DFT) calculations disclose that the lattice distortion enlarges the porous channels for Na+ diffusion in the crystalline phase, thereby optimizing its kinetics to be compatible with the oxygen‐vacancy‐rich amorphous phase. This significantly reduces the high contrast of the kinetic properties between the crystalline and amorphous phases in A/C‐V2O3−x@C‐HMCS and induces the formation of highly dense A/C interfaces with a strong synergistic effect. As a result, the dense heterointerface effectively optimizes the Na+ adsorption energy and lowers the diffusion barrier, thus accelerating the overall kinetics of A/C‐V2O3−x@C‐HMCS. In contrast, the perfect heterophase (defects‐free) A/C‐V2O3@C‐HCS demonstrates sparse A/C interfacial sites with limited synergistic effect and sluggish kinetics. As expected, the A/C‐V2O3−x@C‐HMCS achieves a high rate and ultrastable performance (192 mAh g−1 over 6000 cycles at 10 A g−1) when employed for the first time as a cathode for sodium‐ion batteries (SIBs). This work provides general guidance for realizing dense heterophase cathode design for high‐performance SIBs and beyond.
A defect‐rich heterophase structure A/C‐V2O3−x@C‐HMCS composed of oxygen‐deficient amorphous hollow core and lattice‐distorted crystalline shell encapsulated by carbon is synthesized via a novel strategy. The defects significantly reduce the high contrast of the kinetic properties between the crystalline and amorphous phases and induce the formation of dense A/C interfaces, lowering the energy barriers, and enabling fast and stable SIBs performance.
To improve the long cyclic stability and rate capability of Si-based anode, we demonstrate a core-shell structural Si@NC composite decorates with N-doped carbon network using a low-cost, a simple ...process of electrospinning and low-temperature pyrolysis. Si@PVP/Urea fabric composite spun on the copper foil was directly carbonized and then was cut into wafers used as the electrode plates without extra conductive agent and binder. The enhanced rate capability and cyclic stability of special structural Si@NC is mainly ascribable to N-doped carbon matrix providing numerous active sites, which attract Li to those points in an efficient way, and the core-shell structures supply high mechanical strength for Si@NC composite. Importantly, almost 3-fold improvement in the capacity retention rate of the Si@NC has been observed at high current densities of 1.6 and 3.2 A g
−1
. Meanwhile, DFT calculations confirm that Li will be easily adsorbed by N-active sites in N-doped carbon model to strengthen chemical absorption ability, which could have more chance to grab the quickly moving Li in a brief period. It is significant for theoretical guidance of subsequent studies. The findings should make an important contribution providing a great possibility for the mass production and application to the field of lithium-ion battery.
Nowadays, the rapid development of portable electronic products and low‐emission electric vehicles is putting forward higher requirements for energy‐storage systems. Lithium–sulfur (Li–S) batteries ...with an ultrahigh energy density (2500 Wh kg−1) are considered the most promising candidates for next‐generation rechargeable batteries. However, the low conductivity of sulfur, the shuttle effect of lithium polysulfide (LPS), and inadequate safety caused by lithium dendrite formation limit their practical applications. In the research of Li–S batteries, it is observed that the surface/interface structure and chemistry of sulfur host materials play significant roles in the performance of Li–S batteries. The reason is that the adsorption/conversion of LPS mainly occurs on the surface/interface of host materials. The functional hosts are used to prevent the polysulfide shuttle or catalyze Li–S conversion reactions (enhance the reaction kinetics), and density functional theory (DFT) is used to understand the mechanism of the interaction between host and polysulfides. Herein, the surface/interface structure and chemistry of sulfur host materials involving structural factors and adsorption/conversion mechanisms of LPS (based on DFT calculation) on the interface are demonstrated. Finally, the remaining challenges, such as the fundamental studies and commercialized applications, as well as the future research directions are discussed.
Herein, the recent progress of the surface/interface structure and chemistry of sulfur host materials involving structural factors and adsorption/conversion mechanisms of lithium polysulfides (based on density functional theory calculation) is reviewed. In addition, the remaining challenges, such as the fundamental studies and commercialized applications, as well as the future research directions are also discussed.
The cathode, a crucial constituent part of Li-ion batteries, determines the output voltage and integral energy density of batteries to a great extent. Among them, Ni-rich LiNi
Co
Mn
O
(x + y + z = 1, ...x ≥ 0.6) layered transition metal oxides possess a higher capacity and lower cost as compared to LiCoO
, which have stimulated widespread interests. However, the wide application of Ni-rich cathodes is seriously hampered by their poor diffusion dynamics and severe voltage drops. To moderate these problems, a nanobrick Ni-rich layered LiNi
Co
Mn
O
cathode with a preferred orientation (110) facet was designed and successfully synthesized via a modified co-precipitation route. The galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) analysis of LiNi
Co
Mn
O
reveal its superior kinetic performance endowing outstanding rate performance and long-term cycle stability, especially the voltage drop being as small as 67.7 mV at a current density of 0.5 C for 200 cycles. Due to its unique architecture, dramatically shortened ion/electron diffusion distance, and more unimpeded Li-ion transmission pathways, the current nanostructured LiNi
Co
Mn
O
cathode enhances the Li-ion diffusion dynamics and suppresses the voltage drop, thus resulting in superior electrochemical performance.
In this study, proppant pillar deformation and stability during the fracturing fluid flowback of channel fracturing was simulated with DEM-CFD- (discrete element method-computational fluid dynamics-) ...coupling method. Fibers were modeled by implementing the bonded particle model for contacts between particles. In the hydraulic fracture-closing period, the height of the proppant pillar decreases gradually and the diameter increases as the closing stress increases. In the fracturing fluid flowback period, proppant particles could be driven away from the pillar by the fluid flow and cause the instability of the proppant pillar. The proppant flowback could occur easily with large proppant pillar height or a large fluid pressure gradient. Both the pillar height and the pillar diameter to spacing ratio are key parameters for the design of channel fracturing. Increasing the fiber-bonding strength could enhance the stability of the proppant pillar.
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