A robust nano-Si/graphite nanocomposite with strong and durable interfacial adhesion was rationally designed. The abundant SiTi and TiC covalent bonds leads to greatly improved interfacial adhesion ...between nano-Si and graphite, and thus a highly stabilized electrode structure and good cycling stability.
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The nano-Si/graphite nanocomposites are the promising anodes candidates for high-energy lithium-ion batteries because of their high theoretical capacities and low volume variations. However, the nano-Si has a severe tendency to separate from the graphite substrate due to the inherently weak bonding between them, thus leading to the deteriorated cycling performance and low Coulombic efficiency. Herein, we design a robust nano-Si/graphite nanocomposite structure with strong interfacial adhesion caused by the SiTi and TiC covalent bonds. The abundant SiTi and TiC bonds formed between nano-Si and graphite greatly enhance the interfacial adhesion force, resulting in the highly stabilized and integrated electrode structure during battery cycling. Consequently, the as-obtained nano-Si/graphite anodes deliver a high capacity retention of 90.0% after 420 cycles at 0.5 C with an average Coulombic efficiency of 99.5%; moreover, a high initial Coulombic efficiency of 90.2% is achieved. Significantly, this work provides a novel strategy to address the poor interfacial adhesion between nano-Si and graphite, which can be applied to other nano-Si based composites anodes.
The morphology mediation of MoS2 nanosheets via a facile coagulation method is firstly reported.The abundant sheet crumples were induced, which greatly enhance their surface accessibility and thus ...benefit the Na-ion diffusion kinetics. Importantly, the special role of organic cations in the inter-sheet assembly configuration was demonstrated, in sharp contrast with that of alkali/alkaline-earth ones.
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Ion diffusion kinetics, depending on the size, tortuosity, connectivity of the channels, greatly affects the rate performance of the electrodes. Two-dimensional materials (2DMs) has emerged as promising electrode materials in the past decades. However, the applications of 2DMs electrodes are limited by the strong restacking problem, which leads to a poor rate capability. In this work, we for the first time mediated the morphology of molybdenum disulfide (MoS2) nanosheets via a facile coagulation method; abundant sheet crumples were induced, which greatly enhance their surface accessibility and thus benefit the ion diffusion kinetics. Consequently, the crumpled-MoS2 electrodes follow a capacitive Na-ion charge-storage mechanism to a large extent. Importantly, we demonstrate the special role of organic cations in the inter-sheet assembly configuration, in sharp contrast with that of alkali/alkaline-earth ones. We propose that organic cations cause edge/face contact of the sheets, instead of the face/face contact, thus affording a house-of-cards structure.
The freestanding particles/rGO membrane has been prepared by processing micrometer-sized particles in graphene network through freeze casting, which promises for application of electrode materials in ...energy storage field.
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Graphene oxide (GO) is widely used in the construction and application of various 2D membrane-based materials due to its unique colloidal structure. Herein, we demonstrate that micrometer-sized particles can make up freestanding membranes enabled by the extraordinary amphiphilic and polymer-like properties of graphene oxide through freeze casting. The 2D macromolecule, GO could well wrap the particles for better uniformity and stability in either dispersion or membrane. Importantly, freeze casting plays an important role in avoiding the severe aggregation of micrometer-sized particles in the solvent-removing process. After reduction, the membrane exhibits good electrical conductivity while maintaining its integral structure, which can be directly used as a freestanding binder-free electrode. This work provides a universal approach to fabricate freestanding membranes with various micrometer-sized materials for energy storage.
Fire-resistant materials that provide protection of lives and properties are highly desirable in many applications such as aerospace, electronics, construction building and power transmission. ...However, most of them are inorganic materials with inconvenient processing or high cost. Conventional polymers are generally consumed completely under fire condition so that they can't provide the char sufficient mechanical strength to resist falling away from the protected substrate. Ceramifiable polymers have fire-resistant property and good processability at the same time. This work studied the mechanical strength of different silicone rubber composites (SR-composites) before and after pyrolysis. Properties such as tensile strength, elongation at break, thermal stability, volume variation and residue strength were discussed. SR-composites with five different inorganic fillers exhibited improved mechanical properties after treatment of fillers than the SR-composites filled directly. The layered structure, high aspect ratio, small particle size and good surface organic modification are the reasons of tension strength and elongation at break increase. The thermal stability of the SR-composites decreased due to the incorporation of fillers. The effect of frits on properties of the residues was investigated. Volume variation, compression strength and scanning electron microscopy showed that the frits play a main role of physical bonding with other fillers and keep the shape of residual integrity in the pyrolysis process at 650 °C and assist the formation of ceramic at 950 °C, which lead to volume shrinkage and significant compression strength increase of the residues.
A prevailing perception on Mg metal anodes is that high ion-diffusion barriers in corresponding passivated interfaces can induce poor reversibility and high overpotential. However, the dynamic ...evolution and degradation of native solid/electrolyte interfaces (SEI) in the electrochemical process has not yet been established. To unravel the origin of unstable Mg anodes, this study comprehensively reveals the native SEI is dominated by organic components. A model system with controllable electronically insulating SEI is designed by increasing the inorganic component, to provide a new insight that the interfacial electronic property and composition is decisive to the degradation of Mg metal anodes. The initial organic-rich SEI with insufficient electrical insulation in turn hinders ion transport by undergoing continuous cracking/reformation and electronic leakage which induces continuous proliferation during operation process. By optimizing electronic insulation of the initial interface, a symmetric cell exhibits superior cycling performances of over 1150 h with low polarization.
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•The native interfacial composition plays the decisive role in the interfacial dynamic evolution.•The organic-rich SEI with insufficient electronic insulation leads to the interfacial degeneration.•A simple model is proposed to clarify the inorganic-rich SEI with electronic insulation is crucial for stabilizing Mg metal anodes.
Silicon-based materials are the desirable anodes for next-generation lithium-ion batteries; however, the large volume change of Si during the charging/discharging process causes electrode fracture ...and an unstable solid–electrolyte interphase (SEI) layer, which severely impair their stability and Coulombic efficiency. Herein, a bundle of silicon nanoparticles is encapsulated in robust micrometer-sized MXene frameworks, in which the MXene nanosheets are precrumpled by capillary compression force to effectively buffer the stress induced by the volume change, and the abundant covalent bonds (Ti–O–Ti) between adjacent nanosheets formed through a facile thermal self-cross-linking reaction further guarantee the robustness of the MXene architecture. Both factors stabilize the electrode structure. Moreover, the abundant fluorine terminations on MXene nanosheets contribute to an in situ formation of a highly compact, durable, and mechanically robust LiF-rich SEI layer outside the frameworks upon cycling, which not only shuts down the parasitic reaction between Si and an organic electrolyte but also enhances the structural stability of MXene frameworks. Benefiting from these merits, the as-prepared anodes deliver a high specific capacity of 1797 mA h g–1 at 0.2 A g–1 and a high capacity retention of 86.7% after 500 cycles at 2 A g–1 with an average Coulombic efficiency of 99.6%. Significantly, this work paves the way for other high-capacity electrode materials with a strong volume effect.
Nanostructured silicon-based materials are the promising anodes for next-generation lithium-ion batteries. However, as the result of the weak adhesion of solid-electrolyte interphase (SEI) to Si, the ...fracture, exfoliation and subsequent regrowth of SEI layer on the expanded Si remains unsolved, leading to low initial Coulombic efficiency (ICE) (50–80%). Herein, the Ti‒Si covalent bond between nano-Si and MXene-derived artificial SEI layer is elaborately introduced, to effectively strengthen the interfacial stability and suppress the excessive interfacial side reaction. Upon the three-times expansion during first cycling, the as-obtained anodes with the ultrathin SEI still deliver a high ICE of 91.4%. Due to the stable interfacial ionic conduction, remarkable capacity retention of 90.7% after 1000 cycles at 5 A g−1 with an average Coulombic efficiency of 99.8% could be maintained. This strategy provides new insight into designing durable alloy anodes from the point of the interfacial adhesion strength.
The low initial Coulombic efficiency (ICE) of nanostructured Si-based anodes remains unsolved. In this work, a covalently bonded SEI layer design is proposed for the first time to achieve high ICE. The high interfacial adhesion induced by the strong Ti‒Si covalent bond avoids the fracture and exfoliation of SEI layer, leading to the ultrathin SEI layer of 10 nm and high ICE of 91.4%. Our work provides a new insight into designing high ICE alloy anodes from the point of the interfacial adhesion strength. Display omitted
•A robust artificial SEI layer with abundant covalent bonds on Si anode is rationally designed.•An ultrathin SEI layer of 10 nm is obtained owing to the tremendously decreased interfacial side reaction upon cycling.•High initial Coulombic efficiency of 91.4% and robust cycling stability over 1000 cycles are achieved.
Magnesium–sulfur (Mg-S) batteries are emerging as a promising alternative to lithium-ion batteries, due to their high energy density and low cost. Unfortunately, current Mg-S batteries typically ...suffer from the shuttle effect that originates from the dissolution of magnesium polysulfide intermediates, leading to several issues such as rapid capacity fading, large overcharge, severe self-discharge, and potential safety concern. To address these issues, here we harness a copper phosphide (Cu3P) modified separator to realize the adsorption of magnesium polysulfides and catalyzation of the conversion reaction of S and Mg2+ toward stable cycling of Mg-S cells. The bifunctional layer with Cu3P confined in a carbon matrix is coated on a commercial polypropylene membrane to form a porous membrane with high electrolyte wettability and good thermal stability. Density functional theory (DFT) calculations, polysulfide permeability tests, and post-mortem analysis reveal that the catalytic layer can adsorb polysulfides, effectively restraining the shuttle effect and facilitating the reversibility of the Mg-S cells. As a result, the Mg-S cells can achieve a high specific capacity, fast rates (449 mAh g–1 at 0.1 C and 249 mAh g–1 at 1.0 C), and a long cycle life (up to 500 cycles at 0.5 C) and operate even at elevated temperatures.
The high-capacity silicon anode is regarded as a promising electrode material for next-generation lithium-ion batteries. Unfortunately, its practical application is still severely hindered by ...electrode fracture and unstable solid electrolyte interphase during cycling. Herein, we design a structure of encapsulating silicon in a robust “janus shell”, in which an internal graphene shell with sufficient void space is used to absorb the mechanical stress induced by volume expansion, and the conformal carbon outer shell is introduced to strongly bond the loosely stacked graphene shell and simultaneously seal the nanopores on the surface. With the ultrastable janus carbon shell, the excellent structural integrity of the electrode and stable solid electrolyte interphase layer could be effectively preserved, resulting in an impressive cycling behavior. Indeed, the as-synthesized anodes demonstrate superior cycle stability and excellent rate performance, delivering a high reversible capacity of 1416 mA h g–1 at a current density of 0.2 A g–1 and 852 mA h g–1 at a high current density of 5 A g–1. Remarkably, the superior capacity retention of 88.5% could be achieved even after 400 cycles at a high current density of 2 A g–1. More importantly, this work opens up a novel avenue to address high-capacity anodes with a large volume change.
Metallic sodium anodes are highly attractive due to the high specific capacity and natural abundance, but the uncontrollable Na dendrite issues impede its practical implementation. Nucleation, growth ...and dissolution of Na are an inseparable sequential process, so the variations in these reaction thermodynamics and kinetics could lead to dendrite proliferation and low utilization of Na anode. It appears to be particularly important to optimize the whole continuous process by introducing a super ionic conductor material, Na3V2(PO4)3 (NVP), as the modulation medium of continuous nucleation, growth and dissolution to suppress Na dendrite in this work. The initial intercalation reaction of Na+ into NVP thermodynamically improves the affinity of Na and NVP, leading to a low-barrier nucleation and homogenous Na-ion flux. Importantly, the super ionic conductor dynamically provides ultrafast migration channels to promote the interfacial Na-ion transport, contributing to a reduced electrochemical polarization and uniform Na-ion distribution. As a result, the cell displays superior rate performance and improved cycling stabilities in both half and full cells. This work proposes a new strategy for a thermodynamically and dynamically favorable nucleation and reversible plating/stripping of Na, which can be extended to other metal anodes.
Stable plating/stripping behaviors of sodium with dendrite-free morphology and improved cycling stabilities is realized by sodium super ionic conductor. Display omitted
•Natrium super ionic conductor is introduced to prepare dendrite-free Na metal anode.•3D NVP framework could thermodynamically guide the nucleation and dynamically accelerate interfacial ion transport.•The final obtained electrode delivers prolonged cycling stabilities and small overpotential.
