Rechargeable magnesium (Mg) batteries based on conventional electrolytes are seriously plagued by the formation of the ion‐blocking passivation layer on the Mg metal anode. By tracking the Mg2+ ...solvation sheath, this work links the passivation components to the Mg2+‐solvents (1,2‐dimethoxyethane, DME) coordination and the consequent thermodynamically unstable DME molecules. On this basis, we propose a methodology to tailor solvation coordination by introducing the additive solvent with extreme electron richness. Oxygen atoms in phosphorus‐oxygen groups compete with that in carbon‐oxygen groups of DME for the coordination with Mg2+, thus softening the solvation sheath deformation. Meanwhile, the organophosphorus molecules in the rearranged solvation sheath decompose on the Mg surface, increasing the Mg2+ transport and electrical resistance by three and one orders of magnitude, respectively. Consequently, the symmetric cells exhibit superior cycling performance of over 600 cycles with low polarization.
Solvation sheath rearrangement by tuning the Mg2+‐solvents coordination is effectively applied in the magnesium conventional electrolyte. The passivation problem due to solvent decomposition caused by the strong coordination is solved.
Magnesium ion batteries are a promising alternative of the lithium counterpart; however, the poorly ion-conductive passivation layer on Mg metal makes plating/stripping difficult. In addition to the ...generally recognized chemical passivation, the interphase is dynamically degraded by electrochemical side reactions. Especially under high current densities, the interphase thickens, exacerbating the electrode degradation. Herein, we adopt 3D Mg3Bi2 scaffolds for Mg metal, of which the high surface area reduces the effective current density to avoid continuous electrolyte decomposition and the good Mg affinity homogenizes nucleation. The greatly alleviated passivation layer could serve as a stable solid/electrolyte interface instead. The symmetric cell delivers a low overpotential of 0.21 and 0.50 V at a current density of 0.1 and 4 mA cm–2, respectively, and a superior cycling performance over 300 cycles at 0.5 mA cm–2 in a noncorrosive conventional electrolyte. This work proves that the control of dynamic passivation can enable high-power density Mg metal anodes.
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.
Sodium (Na) metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable. However, an uneven Na-ion migration in bulk Na anodes leads to localized ...deposition/dissolution of sodium during high-rate plating/stripping behaviors, followed by severe dendrite growth and loose stacking. Herein, we engineer the Na hybrid anode with sodiophilic Na3Bi-penetration to develop the abundant phase-boundary ionic transport channels. Compared to intrinsic Na, the reduced adsorption energy and ion-diffusion barrier on Na3Bi ensure even Na+ nucleation and rapid Na+ migration within the hybrid electrode, leading to uniform deposition and dissolution at high current densities. Furthermore, the bismuthide enables compact Na deposition within the sodiophilic framework during cycling, thus favoring a high volumetric capacity. Consequently, the obtained anode was endowed with a high current density (up to 5 mA∙cm−2), high areal capacity (up to 5 mA∙h∙cm−2), and long-term cycling stability (up to 2800 h at 2 mA∙cm−2).
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.
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Electrode materials with high capacitance and outstanding stability are critical for developing flexible supercapacitors (FSCs), which have recently received increasing attention. ...Herein, a hierarchical CuS/three dimensional graphene (3DG) composite was prepared, which possessed a decent specific capacitance of 249Fg−1 at a current density of 4Ag−1 and remarkable cycling stability with 95% retention after 5000 charge-discharge cycles. Moreover, a flexible solid-state supercapacitor was assembled with binder-free electrode materials and exhibited an energy density of 5Whkg−1 at a power density of 450Wkg−1. The peculiar hierarchical structure of CuS could provide abundant contact area between the active material and electrolyte, thus shortening diffusion distance. The high conductivity of 3DG could reduce overall resistance and improve the rate performance of the electrode materials. Therefore, the hierarchical CuS/3DG composite has promising application potential in flexible energy storage devices.
Metallic magnesium batteries are promising candidates beyond lithium‐ion batteries; however, a passive interfacial layer because of the electro‐reduction of solvents on Mg surfaces usually leads to ...ultrahigh overpotential for the reversible Mg chemistry. Inspired by the excellent separation effect of permselective metal–organic framework (MOF) at angstrom scale, a large‐area and defect‐free MOF membrane directly on Mg surfaces is here constructed. In this process, the electrochemical deprotonation of ligand can be facilitated to afford the self‐correcting of intercrystalline voids until a seamless membrane formed, which can eliminate nonselective intercrystalline diffusion of electrolyte and realize selective Mg2+ transport but precisely separate the solvent molecules from the MOF channels. Compared with the continuous solvent reduction on bare Mg anode, the as‐constructed MOF membrane is demonstrated to significantly stabilize the Mg electrode via suppressing the permeation of solvents, hence contributing to a low‐overpotential plating/stripping in conventional electrolytes. The concept is demonstrated that membrane separation can serve as solid‐electrolyte interphase, which would be widely applicable to other energy‐storage systems.
An artificial solid‐electrolyte interphase enabled by an intact metal–organic framework (MOF) membrane is constructed directly on Mg foils. Through precious solvent molecule/Mg ion sieve owing to the angstrom‐sized aperture window, the MOF membrane suppresses the solvent reduction and enables a low migration barrier for Mg2+ transportation within this MOF‐based solid‐electrolyte interphase.
•Robust SnO2 buffers the serious volume expansion of the active SnS2 during cycling.•DFT calculations indicate that the heterogeneous interface exists compressive strain.•New direction on building ...heterogeneous structures: focus on mechanical properties.
Transition-metal dichalcogenides are emerging as a class of attractive host materials for Na+ insertion, owing to its high theoretical specific capacity, whereas the intrinsic low conductivity and huge volume fluctuations during deep cycles severely restrict their practical applications. Heterostructure engineering can not only optimize ion transport kinetics to boost rate property but confine mechanical degradation by participation of the second phases. In order to cushion the internal stress and dramatic volume variations induced by the large radius of Na+, herein we introduced a more robust material (SnO2) to construct CC@SnS2/SnO2 heterostructure for sodium-ion batteries (SIBs). The experimental and density functional theory calculations indicate that compressive stress at the heterogeneous interface can effectively buffer the sodiation-induced internal strain by 10%, further maintain the structural stability and improve the cycling performances. Meanwhile, the involvement of inert SnO2 phase, which effectively alleviate the serious volume expansion caused by the active SnS2 upon an extensive sodiation/desodiation process. As expected, the CC@SnS2/SnO2 composite exhibits high reversible capacity (694.7 mAh g−1 at 0.2 A g−1) and long-term cycling retention (78.3% after 100 cycles). Our work inspire a pathway of the selection of heterogeneous materials toward a highly stable SIBs anode.
Rapid capacity decay is a crucial issue for conversion reaction anodes of sodium ion batteries (SIBs). Here, we introduced the concept of “high entropy” into the conventional transition metal oxides, ...successfully preparing spinel high-entropy oxide (FeCoNiMn)1-xNax3O4 (x = 0.05, 0.08, 0.12) (named after HEO 0.12, HEO 0.08, HEO 0.05) by spray pyrolysis. Due to the “entropy stabilization effect”, an electrode material exhibits respectable stability. Simultaneously, the precise adjustment of oxygen vacancy accomplished by ion substitution demonstrates that oxygen vacancy naturally in HEO not only provides additional active sites for Na+ accommodation and lowers the sodiation energy barrier enabling reversible Na+ intercalation, but also effectively propels charge transfer. As a result, the cooperation of the “entropy stabilization effect” and oxygen vacancy makes HEO 0.12 competitive in terms of cycling performance (average capacity decay of 0.069% cycle−1 at 1000 mA g−1), reversible specific capacity, coulombic efficiency and rate performance compared to those of counterparts. Significantly, the evolution of composition and structure during cycling suggests that the key inducing factors for the satisfactory cycling stability of HEO are the excellent reaction reversibility and structure durability, excavating the nature of the “entropy stabilization effect”. This work sheds novel insights into the development of anodes for SIBs.
Excellent mass transport capability is indispensable to building a high-power lithium-ion battery (LIB) system. Nanomaterials with enhanced electrochemical properties have been used for ...next-generation high-performance LIBs. However, due to the high surface free energy, nanomaterials tend to form agglomeration. The resulting insufficient mass transport channels limit the high rate performance of nanomaterials. Here, we increase the electrolyte accessibility of nanomaterials through a facile ionic liquid (IL) mediation method. The fluidity and affinity enable the IL to infiltrate into the interstitials of nanomaterial aggregations under capillary force, enhancing the electrochemically active contact area and ensuring rapid mass transport. As a proof of concept, IL-mediated LiFePO4 electrodes delivered extraordinary rate performance (112 and 95 mAh g–1 at 200 and 300 C, respectively). In terms of simplicity, the IL mediation can be used as a general strategy to achieve an ultrahigh rate for LIBs.
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