Showing papers by "Meng-Qiang Zhao published in 2017"
TL;DR: In this article, two-dimensional transition metal carbides exhibit high gravimetric, volumetric, and areal capacitance values at high charcoefficients at high temperature.
Abstract: Pseudocapacitors based on redox-active materials have relatively high energy density but suffer from low power capability. Here the authors report that two-dimensional transition metal carbides exhibit high gravimetric, volumetric and areal capacitance values at high char…
1,477 citations
TL;DR: The 3D macroporous MXene films are free-standing, flexible, and highly conductive due to good contacts between spheres and metallic conductivity of MXenes as discussed by the authors.
Abstract: 2D transition metal carbides and nitrides, named MXenes, are attracting increasing attentions and showing competitive performance in energy storage devices including electrochemical capacitors, lithium- and sodium-ion batteries, and lithium-sulfur batteries. However, similar to other 2D materials, MXene nanosheets are inclined to stack together, limiting the device performance. In order to fully utilize MXenes' electrochemical energy storage capability, here, processing of 2D MXene flakes into hollow spheres and 3D architectures via a template method is reported. The MXene hollow spheres are stable and can be easily dispersed in solvents such as water and ethanol, demonstrating their potential applications in environmental and biomedical fields as well. The 3D macroporous MXene films are free-standing, flexible, and highly conductive due to good contacts between spheres and metallic conductivity of MXenes. When used as anodes for sodium-ion storage, these 3D MXene films exhibit much improved performances compared to multilayer MXenes and MXene/carbon nanotube hybrid architectures in terms of capacity, rate capability, and cycling stability. This work demonstrates the importance of MXene electrode architecture on the electrochemical performance and can guide future work on designing high-performance MXene-based materials for energy storage, catalysis, environmental, and biomedical applications.
666 citations
TL;DR: The authors show that nanodiamonds serve as an electrolyte additive to co-deposit with lithium metal and suppress the formation of dendrites, affording a promising route to suppress lithium dendrite growth in lithium metal-based batteries.
Abstract: Lithium metal has been regarded as the future anode material for high-energy-density rechargeable batteries due to its favorable combination of negative electrochemical potential and high theoretical capacity. However, uncontrolled lithium deposition during lithium plating/stripping results in low Coulombic efficiency and severe safety hazards. Herein, we report that nanodiamonds work as an electrolyte additive to co-deposit with lithium ions and produce dendrite-free lithium deposits. First-principles calculations indicate that lithium prefers to adsorb onto nanodiamond surfaces with a low diffusion energy barrier, leading to uniformly deposited lithium arrays. The uniform lithium deposition morphology renders enhanced electrochemical cycling performance. The nanodiamond-modified electrolyte can lead to a stable cycling of lithium | lithium symmetrical cells up to 150 and 200 h at 2.0 and 1.0 mA cm–2, respectively. The nanodiamond co-deposition can significantly alter the lithium plating behavior, affording a promising route to suppress lithium dendrite growth in lithium metal-based batteries.
314 citations
TL;DR: This work reports on the use of two-dimensional titanium carbide, Ti3C2Tx (MXene), as a cathode in hybrid Mg2+/Li+ batteries, coupled with a Mg metal anode.
Abstract: As an alternative to pure lithium-ion, Li+, systems, a hybrid magnesium, Mg2+, and Li+ battery can potentially combine the high capacity, high voltage, and fast Li+ intercalation of Li-ion battery cathodes and the high capacity, low cost, and dendrite-free Mg metal anodes. Herein, we report on the use of two-dimensional titanium carbide, Ti3C2Tx (MXene), as a cathode in hybrid Mg2+/Li+ batteries, coupled with a Mg metal anode. Free-standing and flexible Ti3C2Tx/carbon nanotube composite “paper” delivered ∼100 mAh g–1 at 0.1 C and ∼50 mAh g–1 at 10 C. At 1 C the capacity was maintained for >500 cycles at 80 mAh g–1. The Mo2CTx MXene also demonstrated good performance as a cathode material in this hybrid battery. Considering the variety of available MXenes, this work opens the door for exploring a new large family of 2D materials with high electrical conductivity and large intercalation capacity as cathodes for hybrid Mg2+/Li+ batteries.
177 citations
TL;DR: In this paper, the interaction of synthetic conjugated polymers [polyfluorene derivatives (PFDs)] with layers of two-dimensional titanium carbide (Ti3C2Tx) was investigated using a range of microscopic and spectroscopic techniques.
Abstract: This article provides insight into the interaction of synthetic conjugated polymers [polyfluorene derivatives (PFDs)] with layers of two-dimensional titanium carbide (Ti3C2Tx). Three derivatives with nonpolar, polar, and charged nitrogen-containing functionalities were synthesized via the Suzuki polycondensation reaction. The organic–inorganic PFD/Ti3C2Tx hybrids were prepared and characterized using X-ray diffraction and a range of microscopic and spectroscopic techniques to elucidate the host–guest interaction mechanism. We show that polar polymers with charged nitrogen-containing ends have the strongest interaction with the Ti3C2Tx layers, yielding an increase in interlayer spacing and large shifts in spectroscopic peaks. Furthermore, the effect of polymer backbone juxtaposition between Ti3C2Tx layers on pseudocapacitance is discussed in detail. Our results suggest that new organic materials capable of intercalation between the layers of Ti3C2Tx and other MXenes may be used in the design of hybrid stru...
153 citations
TL;DR: In this article, a combined experimental and theoretical study revealed the mechanism of charge-transfer-induced polymerization of 3,4-ethylenedioxythiophene (EDOT), which can be extended to other similar polymers.
Abstract: In situ polymerization of 3,4-ethylenedioxythiophene (EDOT) is achieved on the surface of 2D Ti3C2Tx MXene without using any oxidant, resulting in improved lithium ion storage capability of Ti3C2Tx/poly-EDOT hybrids. A combined experimental and theoretical study revealed the mechanism of charge-transfer-induced polymerization of EDOT, which can be extended to other similar polymers.
134 citations
TL;DR: Direct chemical vapor deposition of in-plane monolayer heterostructures based on 1H-MoS2 and 1T'-MoTe2 shows the feasibility of dislocation-free stitching of two different atomic configurations and a pathway toward direct synthesis of monolayers TMD heterostructure of different phases.
Abstract: Heterostructures of transition metal dichalcogenides (TMDs) offer the attractive prospect of combining distinct physical properties derived from different TMD structures. Here, we report direct chemical vapor deposition of in-plane monolayer heterostructures based on 1H-MoS2 and 1T′-MoTe2. The large lattice mismatch between these materials led to intriguing phenomena at their interface. Atomic force microscopy indicated buckling in the 1H region. Tip-enhanced Raman spectroscopy showed mode structure consistent with Te substitution in the 1H region during 1T′-MoTe2 growth. This was confirmed by atomic resolution transmission electron microscopy, which also revealed an atomically stitched, dislocation-free 1H/1T′ interface. Theoretical modeling revealed that both the buckling and absence of interfacial misfit dislocations were explained by lateral gradients in Te substitution levels within the 1H region and elastic coupling between 1H and 1T′ domains. Phase field simulations predicted 1T′ morphologies with ...
44 citations
TL;DR: In this paper, the photoluminescence of van der Waals heterostructures of monolayer MoS2 and graphene at room temperature was studied and two peaks associated with trion emission were observed.
Abstract: The 2D geometry nature and low dielectric constant in transition-metal dichalcogenides lead to easily formed strongly bound excitons and trions. Here, we studied the photoluminescence of van der Waals heterostructures of monolayer MoS2 and graphene at room temperature and observed two photoluminescence peaks that are associated with trion emission. Further study of different heterostructure configurations confirms that these two peaks are intrinsic to MoS2 and originate from a bound state and Fermi level, respectively, of which both accept recoiled electrons from trion recombination. We demonstrate that the recoil effect allows us to electrically control the photon energy of trion emission by adjusting the gate voltage. In addition, significant thermal smearing at room temperature results in capture of recoil electrons by bound states, creating photoemission peak at low doping level whose photon energy is less sensitive to gate voltage tuning. This discovery reveals an unexpected role of bound states for ...
10 citations
01 Jan 2017
TL;DR: In this paper, a facile approach to synthesize micro-mesoporous zinc-manganese oxide/graphene (Zn-Mn-O/G) hybrids with the specific surface area of 2276 m2 g-1 in the mixed solvent of water-ethanol was reported.
Abstract: Hierarchy porous mixed metal oxides/graphene two-dimensional nanostructures, providing extra active position for lithium storage, have represented a hopeful platform for next-generation anode materials Here, we report a facile approach to synthesize micro-/mesoporous zinc-manganese oxide/graphene (Zn-Mn-O/G) hybrids with the specific surface area of 2276 m2 g-1 in the mixed solvent of water-ethanol Owing to the micro-/mesoporous structure and large specific area, as well as strongly coupled effects between Zn-Mn-O and graphene sheets, the hybrids deliver a high capacity of 1216 mAh g-1 at a current density of 500 mA g-1 after 100 cycles, superior rate performance of 558 mAh g-1 at 8000 mA g-1, as well as ultralong cycle life up to 900 cycles In addition, when performed in the temperature range of 5 to 45 oC, the Zn-Mn-O/G anode has demonstrated the specific capacities from 748 to 1245 mAh g-1 after 100 cycles
10 citations