9 research outputs found
Oxygen-Incorporated MoS<sub>2</sub> Nanosheets with Expanded Interlayers for Hydrogen Evolution Reaction and Pseudocapacitor Applications
Two-dimensional
transition-metal dichalcogenides (TMDs) nanosheets have attracted
tremendous research interest. Engineering the structure of MoS<sub>2</sub> may result in desirable performance for energy applications.
In this work, oxygen-incorporated MoS<sub>2</sub> nanosheets with
expanded interlayers have been synthesized by a solvothermal reaction.
The oxygen-incorporated MoS<sub>2</sub> nanosheets with rich defects
demonstrate excellent hydrogen evolution reaction activity with a
small Tafel slope of 42 mV decade<sup>–1</sup> as well as excellent
long-term stability. Interestingly, a large expanded ∼8.40
Ã… interlayer of (002) faces can be achieved by controlling the
reaction time. This material also shows excellent long-term cycling
stability (up to 20 000 cycles) as well as high specific capacitance
for pseudocapacitors. We believe that the structural modification
strategy can be applied for other TMDs to further optimize the performance
for various applications
Additional file 1: of Controllable Preparation of V2O5/Graphene Nanocomposites as Cathode Materials for Lithium-Ion Batteries
XRD patterns of vanadium precursors, CV curves, charge/discharge profiles of the V@GO-II composite. Discharge/charge voltage profiles of the V@GO-I composite. Raman peaks and their assignments of V2O5. Figure S1. XRD patterns of the nanosheet-assembled vanadium precursor/GO composite (blue line) and the nanoparticle-assembled vanadium precursor/GO composite (red line). Figure S2. CV curves of the V/GO-II composite at a scan rate of 0.1 mV s−1. Figure S3. Charge/discharge profiles of the V@GO-II composite at different densities. Figure S4. Discharge/charge voltage profiles of the V@GO-I composite (a) and the V@GO-I composite (b) at a current rate of 2C. (DOC 4760 kb
Ultrathin Na<sub>1.1</sub>V<sub>3</sub>O<sub>7.9</sub> Nanobelts with Superior Performance as Cathode Materials for Lithium-Ion Batteries
The Na<sub>1.1</sub>V<sub>3</sub>O<sub>7.9</sub> nanobelts have
been synthesized by a facile and scalable hydrothermal reaction with
subsequent calcinations. The morphologies and the crystallinity of
the nanobelts are largely determined by the calcination temperatures.
Ultrathin nanobelts with a thickness around 20 nm can be obtained,
and the TEM reveals that the nanobelts are composed of many stacked
thinner belts. When evaluated as a cathode material for lithium batteries,
the Na<sub>1.1</sub>V<sub>3</sub>O<sub>7.9</sub> nanobelts exhibit
high specific capacity, good rate capability, and superior long-term
cyclic stability. A high specific capacity of 204 mA h g<sup>–1</sup> can be delivered at the current density of 100 mA g<sup>–1</sup>. It shows excellent capacity retention of 95% after 200 cycles at
the current density of 1500 mA g<sup>–1</sup>. As demonstrated
by the ex situ XRD results, the Na<sub>1.1</sub>V<sub>3</sub>O<sub>7.9</sub> nanobelts have very good structural stability upon cycling.
The superior electrochemical performances can be attributed to the
ultra-thin nanobelts and the good structural stability of the Na<sub>1.1</sub>V<sub>3</sub>O<sub>7.9</sub> nanobelts
Uniform MnCo<sub>2</sub>O<sub>4</sub> Porous Dumbbells for Lithium-Ion Batteries and Oxygen Evolution Reactions
Three-dimensional
(3D) binary oxides with hierarchical porous nanostructures are attracting
increasing attentions as electrode materials in energy storage and
conversion systems because of their structural superiority which not
only create desired electronic and ion transport channels but also
possess better structural mechanical stability. Herein, unusual 3D
hierarchical MnCo<sub>2</sub>O<sub>4</sub> porous dumbbells have been
synthesized by a facile solvothermal method combined with a following
heat treatment in air. The as-obtained MnCo<sub>2</sub>O<sub>4</sub> dumbbells are composed of tightly stacked nanorods and show a large
specific surface area of 41.30 m<sup>2</sup> g<sup>–1</sup> with a pore size distribution of 2–10 nm. As an anode material
for lithium-ion batteries (LIBs), the MnCo<sub>2</sub>O<sub>4</sub> dumbbell electrode exhibits high reversible capacity and good rate
capability, where a stable reversible capacity of 955 mA h g<sup>–1</sup> can be maintained after 180 cycles at 200 mA g<sup>–1</sup>. Even at a high current density of 2000 mA g<sup>–1</sup>, the electrode can still deliver a specific capacity of 423.3 mA
h g<sup>–1</sup>, demonstrating superior electrochemical properties
for LIBs. In addition, the obtained 3D hierarchical MnCo<sub>2</sub>O<sub>4</sub> porous dumbbells also display good oxygen evolution
reaction activity with an overpotential of 426 mV at a current density
of 10 mA cm<sup>–2</sup> and a Tafel slope of 93 mV dec<sup>–1</sup>
Dodecahedron-Shaped Porous Vanadium Oxide and Carbon Composite for High-Rate Lithium Ion Batteries
Carbon-based
nanocomposites have been extensively studied in energy
storage and conversion systems because of their superior electrochemical
performance. However, the majority of metal oxides are grown on the
surface of carbonaceous material. Herein, we report a different strategy
of constructing V<sub>2</sub>O<sub>5</sub> within the metal organic
framework derived carbonaceous dodecahedrons. Vanadium precursor is
absorbed into the porous dodecahedron-shaped carbon framework first
and then <i>in situ</i> converted into V<sub>2</sub>O<sub>5</sub> within the carbonaceous framework in the annealing process
in air. As cathode materials for lithium ion batteries, the porous
V<sub>2</sub>O<sub>5</sub>@C composites exhibit enhanced electrochemical
performance, due to the synergistic effect of V<sub>2</sub>O<sub>5</sub> and carbon composite
Nanorod-Nanoflake Interconnected LiMnPO<sub>4</sub>·Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C Composite for High-Rate and Long-Life Lithium-Ion Batteries
Olivine-type
structured LiMnPO<sub>4</sub> has been extensively studied as a high-energy
density cathode material for lithium-ion batteries. However, preparation
of high-performance LiMnPO<sub>4</sub> is still a large obstacle due
to its intrinsically sluggish electrochemical kinetics. Recently,
making the composites from both active components has been proven
to be a good proposal to improve the electrochemical properties of
cathode materials. The composite materials can combine the advantages
of each phase and improve the comprehensive properties. Herein, a
LiMnPO<sub>4</sub>·Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C composite with interconnected nanorods and nanoflakes
has been synthesized via a one-pot, solid-state reaction in molten
hydrocarbon, where the oleic acid functions as a surfactant. With
a highly uniform hybrid architecture, conductive carbon coating, and
mutual cross-doping, the LiMnPO<sub>4</sub>·Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C composite manifests high capacity,
good rate capability, and excellent cyclic stability in lithium-ion
batteries. The composite electrodes deliver a high reversible capacity
of 101.3 mAh g<sup>–1</sup> at the rate up to 16 C. After 4000
long-term cycles, the electrodes can still retain 79.39% and 72.74%
of its maximum specific discharge capacities at the rates of 4C and
8C, respectively. The results demonstrate that the nanorod-nanoflake
interconnected LiMnPO<sub>4</sub>·Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C composite is a promising cathode material
for high-performance lithium ion batteries
Nitrogen-Doped Yolk–Shell-Structured CoSe/C Dodecahedra for High-Performance Sodium Ion Batteries
In this work, nitrogen-doped,
yolk–shell-structured CoSe/C mesoporous dodecahedra are successfully
prepared by using cobalt-based metal–organic frameworks (ZIF-67)
as sacrificial templates. The CoSe nanoparticles are in situ produced
by reacting the cobalt species in the metal–organic frameworks
with selenium (Se) powder, and the organic species are simultaneously
converted into nitrogen-doped carbon material in an inert atmosphere
at temperatures between 700 and 900 °C for 4 h. For the composite
synthesized at 800 °C, the carbon framework has a relatively
higher extent of graphitization, with high nitrogen content (17.65%).
Furthermore, the CoSe nanoparticles, with a size of around 15 nm,
are coherently confined in the mesoporous carbon framework. When evaluated
as novel anode materials for sodium ion batteries, the CoSe/C composites
exhibit high capacity and superior rate capability. The composite
electrode delivers the specific capacities of 597.2 and 361.9 mA h
g<sup>–1</sup> at 0.2 and 16 A g<sup>–1</sup>, respectively
Presentation_1_Electrospun Single Crystalline Fork-Like K2V8O21 as High-Performance Cathode Materials for Lithium-Ion Batteries.pdf
<p>Single crystalline fork-like potassium vanadate (K<sub>2</sub>V<sub>8</sub>O<sub>21</sub>) has been successfully prepared by electrospinning method with a subsequent annealing process. The as-obtained K<sub>2</sub>V<sub>8</sub>O<sub>21</sub> forks show a unique layer-by-layer stacked structure. When used as cathode materials for lithium-ion batteries, the as-prepared fork-like materials exhibit high specific discharge capacity and excellent cyclic stability. High specific discharge capacities of 200.2 and 131.5 mA h g<sup>−1</sup> can be delivered at the current densities of 50 and 500 mA g<sup>−1</sup>, respectively. Furthermore, the K<sub>2</sub>V<sub>8</sub>O<sub>21</sub> electrode exhibits excellent long-term cycling stability which maintains a capacity of 108.3 mA h g<sup>−1</sup> after 300 cycles at 500 mA g<sup>−1</sup> with a fading rate of only 0.043% per cycle. The results demonstrate their potential applications in next-generation high-performance lithium-ion batteries.</p
Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> Nanoarrays with Decorated C<sub>3</sub>N<sub>4</sub> Nanosheets as Efficient Electrode for Supercapacitors
Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub>-based composites grown on conductive
substrate can efficiently promote the electrical transport during
the electrochemical reactions in supercapacitors. However, Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> nanoarrays are easily peeled off
from the substrate upon repeated electrochemical reaction. Herein,
Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> nanoarrays grown on Ni foam
with surficially decorated C<sub>3</sub>N<sub>4</sub> thin nanosheets
are achieved by a hydrothermal and in situ calcination strategy. The
decorated C<sub>3</sub>N<sub>4</sub> nanosheet network on the surface
fully covers both Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> and Ni
foam and efficiently prevents Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> nanoarrays from peeling off during the charge and discharge cycles.
The optimized composites exhibit high pseudocapacitance and greatly
enhanced cycling stability. The assembled asymmetric supercapacitor
shows favorable specific capacitance and stability as energy storage
devices. Such a strategy for fabricating C<sub>3</sub>N<sub>4</sub>-modified Ni<sub>2</sub>P<sub>2</sub>O<sub>7</sub> nanoarrays is
feasible and efficient, and can be therefore extended for constructing
other electrodes with high capacitance and excellent stability