Sodium metal batteries are arousing extensive interest owing to their high energy density, low cost and wide resource. However, the practical development of sodium metal batteries is inherently ...plagued by the severe volume expansion and the dendrite growth of sodium metal anode during long cycles under high current density. Herein, a simple electrospinning method is applied to construct the uniformly nitrogen-doped porous carbon fiber skeleton and used as three-dimensional (3D) current collector for sodium metal anode, which has high specific surface area (1,098 m
2
/g) and strong binding to sodium metal. As a result, nitrogen-doped carbon fiber current collector shows a low sodium deposition overpotential and a highly stable cyclability for 3,500 h with a high coulombic effciency of 99.9% at 2 mA/cm
2
and 2 mAh/cm
2
. Moreover, the full cells using carbon coated sodium vanadium phosphate as cathode and sodium pre-plated nitrogen-doped carbon fiber skeleton as hybrid anode can stably cycle for 300 times. These results illustrate an effective strategy to construct a 3D uniformly nitrogen-doped carbon skeleton based sodium metal hybrid anode without the formation of dendrites, which provide a prospect for further development and research of high performance sodium metal batteries.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Li metal is an ideal anode material owing to its high theoretical specific capacity and low electrode potential. However, its high reactivity and dendritic growth in carbonate-based electrolytes ...limit its application. To address these issues, we propose a novel surface modification technique using heptafluorobutyric acid. In-situ spontaneous reaction between Li and the organic acid generates a lithiophilic interface of lithium heptafluorobutyrate for dendrite-free uniform Li deposition, which significantly improves the cycle stability (Li/Li symmetric cells >1200 h at 1.0 mA cm
) and Coulombic efficiency (>99.3%) in conventional carbonate-based electrolytes. This lithiophilic interface also enables full batteries to achieve 83.2% capacity retention over 300 cycles under realistic testing condition. Lithium heptafluorobutyrate interface acts as an electrical bridge for uniform lithium-ion flux between Li anode and plating Li, which minimizes the occurrence of tortuous lithium dendrites and lowers interface impedance.
Seeking candidate photocatalysts for photocatalytic water splitting, via visible light, is of great interest and importance. In this study, we have comprehensively explored the crystal structures, ...electronic properties, and optical absorbance of two-dimensional (2D) Sc2CT2 (T = F, Cl, Br) MXenes and their corresponding photocatalytic water splitting, under the visible-light region, by first-principles calculations. Herein, we have proposed that 2D Sc2CT2 MXenes can be fabricated from their layered bulk compounds, alternatively to the traditional chemical etching method. Creatively, we proposed Sc2CT2 (T = F, Br) as new materials; the band edge alignments of Sc2CF2 can be tuned to meet the water redox potentials at pH = 8.0. It is highlighted that Sc2CF2 shows outstanding optical spectra harvested under visible-light wavelength regions, and efficient separation of photo-induced electrons and holes in different zones. These present results provide eloquent evidence and open a new door on the photocatalysis applications of such novel semiconducting MXenes.
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•Current-induced solder evolution was comprehensively explored via in-situ experiments and simulations by considering of β-Sn anisotropy.•The spatial inconsistency between β-Sn ...distribution and bump geometry led to an accumulation of torsion forces and solder rigid rotation.•The electron-dislocation interaction promoted dislocation propagation and slip, leading to solder strengthening and lattice rotation.•The electric fields could accelerate the movement of twin boundaries and promote solder detwinning.
The miniaturization trend of three-dimensional integrated circuits poses great challenges to solder reliability under high current stressing since anisotropic issues tend to be enhanced in microscale solder bumps. To address these challenges, the solder evolution at the microscale and the corresponding mechanism should be addressed. In this study, by considering the anisotropy of β-Sn in the electrical, thermal, mechanical and diffusional characteristics, the current-induced solder evolution of a typical solder bump was comprehensively explored over time. The results confirmed that the anisotropy of β-Sn aggravated the nonuniform distribution of current-induced stresses, further causing multiple migration modes coupled in the solder bump. The spatial inconsistency between the distribution of β-Sn unit cells and the bump geometry led to accumulation of torsion forces, which became the direct reason for solder rigid rotation. The electron-dislocation interaction promoted dislocation slip, leading to lattice rotation and homogenization of intragranular deformation. In addition, current-induced grain merging via detwinning was observed, and its velocity was faster than imagined. Our study is conducive to thoroughly understanding anisotropic evolution and establishing accurate damage mechanisms for micro solder bump design under current stressing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Highlights
A bi-service host with lithiophilic/sulfiphilic Fe
2
CoSe
4
quantum dots embedded in three-dimensional ordered nitrogen-doped carbon skeleton is elaborately developed for both the sulfur ...cathode and Li anode synchronously.
The highly dispersed Fe
2
CoSe
4
quantum dots can not only act as a redox accelerator to promote the bidirectional conversion of LiPSs but also regulate the uniform Li plating/stripping to mitigate the growth of Li dendrite.
The assembled Li-S full batteries achieve excellent long-term cyclability and a remarkable areal capacity of 8.41 mAh cm
2
at high sulfur loading of 8.50 mg cm
2
, and the pouch full battery also displays high capacity and cycling-stability at lean electrolyte condition.
The commercial viability of lithium–sulfur batteries is still challenged by the notorious lithium polysulfides (LiPSs) shuttle effect on the sulfur cathode and uncontrollable Li dendrites growth on the Li anode. Herein, a bi-service host with Co-Fe binary-metal selenide quantum dots embedded in three-dimensional inverse opal structured nitrogen-doped carbon skeleton (3DIO FCSe-QDs@NC) is elaborately designed for both sulfur cathode and Li metal anode. The highly dispersed FCSe-QDs with superb adsorptive-catalytic properties can effectively immobilize the soluble LiPSs and improve diffusion-conversion kinetics to mitigate the polysulfide-shutting behaviors. Simultaneously, the 3D-ordered porous networks integrated with abundant lithophilic sites can accomplish uniform Li deposition and homogeneous Li-ion flux for suppressing the growth of dendrites. Taking advantage of these merits, the assembled Li–S full batteries with 3DIO FCSe-QDs@NC host exhibit excellent rate performance and stable cycling ability (a low decay rate of 0.014% over 2,000 cycles at 2C). Remarkably, a promising areal capacity of 8.41 mAh cm
−2
can be achieved at the sulfur loading up to 8.50 mg cm
−2
with an ultra-low electrolyte/sulfur ratio of 4.1 μL mg
−1
. This work paves the bi-serve host design from systematic experimental and theoretical analysis, which provides a viable avenue to solve the challenges of both sulfur and Li electrodes for practical Li–S full batteries.
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Designing the electronic structures of the van der Waals (vdW) heterostructures to obtain high-efficiency solar cells showed a fascinating prospect. In this work, we screened the potential of vdW ...heterostructures for solar cell application by combining the group III–VI MXA (M = Al, Ga, In and XA = S, Se, Te) and elementary group VI XB (XB = Se, Te) monolayers based on first-principle calculations. The results highlight that InSe/Te vdW heterostructure presents type-II electronic band structure feature with a band gap of 0.88 eV, where tellurene and InSe monolayer are as absorber and window layer, respectively. Interestingly, tellurene has a 1.14 eV direct band gap to produce the photoexcited electron easily. Furthermore, InSe/Te vdW heterostructure shows remarkably light absorption capacities and distinguished maximum power conversion efficiency (PCE) up to 13.39%. Our present study will inspire researchers to design vdW heterostructures for solar cell application in a purposeful way.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Two-dimensional van der Waals (vdW) heterostructures are potential candidates for clean energy conversion materials to address the global energy crisis and environmental issues. In this work, we have ...comprehensively studied the geometrical, electronic, and optical properties of M2CO2/MoX2 (M = Hf, Zr; X = S, Se, Te) vdW heterostructures, as well as their applications in the fields of photocatalytic and photovoltaic using density functional theory calculations. The lattice dynamic and thermal stabilities of designed M2CO2/MoX2 heterostructures are confirmed. Interestingly, all the M2CO2/MoX2 heterostructures exhibit intrinsic type-II band structure features, which effectively inhibit the electron-hole pair recombination and enhance the photocatalytic performance. Furthermore, the internal built-in electric field and high anisotropic carrier mobility can separate the photo-generated carriers efficiently. It is noted that M2CO2/MoX2 heterostructures exhibit suitable band gaps in comparison to the M2CO2 and MoX2 monolayers, which enhance the optical-harvesting abilities in the visible and ultraviolet light zones. Zr2CO2/MoSe2 and Hf2CO2/MoSe2 heterostructures possess suitable band edge positions to provide the competent driving force for water splitting as photocatalysts. In addition, Hf2CO2/MoS2 and Zr2CO2/MoS2 heterostructures deliver a power conversion efficiency of 19.75% and 17.13% for solar cell applications, respectively. These results pave the way for exploring efficient MXenes/TMDCs vdW heterostructures as photocatalytic and photovoltaic materials.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Developing Ohmic contact systems or achieving low contact resistance is significant for high‐performance semiconductor devices. This work comprehensively investigates the interfacial properties of ...CrX2N4 (X = C, Si) based field‐effect transistors (FETs) with different metal (Ag, Au, Cu, Ni, Pd, Pt, Ti, and graphene) electrodes by using electronic structure calculations and quantum transport simulations. It is highlighted that the stronger interlayer coupling allows CrC2N4 to form an n‐type Ohmic contact with Ti electrode in the vertical direction. Furthermore, the absence of tunneling barrier at the CrC2N4–Ti interface greatly improves the electron injection efficiency. On the other hand, the studied metals form Schottky contact with CrC2N4 at the lateral interface due to Fermi level pinning (FLP) effects. Surprisingly, the strong FLP effects restrict the Schottky barrier heights of CrSi2N4‐metal contacts to a narrow range. Where Ag, Au, Ni, Pd, Pt, Ti electrodes and Ag, Ti electrodes form ideal ohmic contact with CrSi2N4 in the vertical and lateral directions, respectively, while the other metals form quasi‐ohmic contact. Ti exhibits the highest contact performance as the electrode in both CrC2N4 and CrSi2N4 based FETs. The findings may provide fundamental understanding for designing high‐performance and energy‐efficient FETs based on CrX2N4.
Based on first‐principles calculations and nonequilibrium Green's function simulations of CrX2N4 based field‐effect transistors (FETs) with various electrodes, it is found that CrC2N4 forms an Ohmic contact with Ti electrode in the vertical direction. Furthermore, the strong Fermi level pinning effects restrict the Schottky barrier hights of CrSi2N4 based FETs to a narrow range, therefore, quasi‐Ohmic contact or Ohmic contacts are formed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Two-dimensional electride Ca2N has strong electron transfer ability and low work function, which is a potential candidate for hydrogen evolution reaction (HER) catalyst. In this work, based on ...density functional theory calculations, we adopt two strategies to improve the HER catalytic activity of Ca2N monolayer: introducing Ca or N vacancy and doping transition metal atoms (TM, refers to Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Ru, Hf, Ta and W). Interestingly, the Gibbs free energy ΔGH∗ of Ca2N monolayer after introducing N vacancy is reduced to -0.146 eV, showing good HER catalytic activity. It is highlighted that, the HER catalytic activity of Ca2N monolayer can be further enhanced with TM doping, the Gibbs free energy ΔGH∗ of single Mo and double Mn doped Ca2N are predicted to be 0.119 and 0.139 eV, respectively. The present results will provide good theoretical guidance for the HER catalysis applications of two-dimensional electride Ca2N monolayer.
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The HER catalytic activity of 2D electride Ca2N monolayer has been enhanced by introducing Ca or N vacancies and transition metal atoms (TM, refers to Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Ru, Hf, Ta and W) dopants, which expands its application prospect in the field of HER catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
By treating Al4C3 as the precursor and growth environment, graphene nanosheets (GNs) can efficiently be derived from coal-tar pitch, which has the advantages of simple preparation process, high ...product quality, green environmental protection, low equipment requirements and low preparation cost. However, the defects in the prepared GNs have not been well understood. In order to optimize the preparation process, based on density functional theory calculations, the influence mechanism of Al-O and Al-C clusters on defects in GNs derived from coal-tar pitch via Al4C3 precursor has been systematically investigated. With minute quantities of oxygen-containing defects, Al-O and Al-C clusters have been realized in the prepared GNs from X-ray photoelectron spectroscopy analysis. Therefore, the influences of Al-O and Al-C clusters on graphene with vacancy defects and oxygen-containing defects are systematically explored from theoretical energy, electron localization function and charge transfer analysis. It is noted that the remaining Al-O and Al-C clusters in GNs are inevitably from the thermodynamics point of view. On the other hand, the existence of defects is beneficial for the further adsorption of Al-O and Al-C clusters in GNs.
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