12 research outputs found
Iso-Oriented NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> Mesocrystals as Anode Material for High-Energy and Long-Durability Sodium-Ion Capacitor
Sodium-ion
capacitors (SIC) combine the merits of both high-energy batteries
and high-power electrochemical capacitors as well as the low cost
and high safety. However, they are also known to suffer from the severe
deficiency of suitable electrode materials with high initial Coulombic
efficiency (ICE) and kinetic balance between both electrodes. Herein,
we report a facile solvothermal synthesis of NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> nanocages constructed by iso-oriented tiny nanocrystals
with a mesoporous architecture. It is notable that the NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> mesocrystals exhibit a large ICE of
94%, outstanding rate capability (98 mA h g<sup>β1</sup> at
10 C), and long cycling life (over 77% capacity retention after 10β―000
cycles) in half cells, all of which are in favor to be utilized into
a full cell. When assembled with commercial activated carbon to an
SIC, the system delivers an energy density of 56 Wh kg<sup>β1</sup> at a power density of 39 W kg<sup>β1</sup>. Even at a high
current rate of 5 A g<sup>β1</sup> (corresponds to finish a
full charge/discharge process in 2 min), the SIC still works well
after 20β―000 cycles without obvious capacity degradation. With
the merits of impressive energy/power densities and longevity, the
obtained hybrid capacitor should be a promising device for highly
efficient energy storage systems
Amorphous ZnO Quantum Dot/Mesoporous Carbon Bubble Composites for a High-Performance Lithium-Ion Battery Anode
Due to its high theoretical
capacity (978 mA h g<sup>β1</sup>), natural abundance, environmental
friendliness, and low cost, zinc
oxide is regarded as one of the most promising anode materials for
lithium-ion batteries (LIBs). A lot of research has been done in the
past few years on this topic. However, hardly any research on amorphous
ZnO for LIB anodes has been reported despite the fact that the amorphous
type could have superior electrochemical performance due to its isotropic
nature, abundant active sites, better buffer effect, and different
electrochemical reaction details. In this work, we develop a simple
route to prepare an amorphous ZnO quantum dot (QDs)/mesoporous carbon
bubble composite. The composite consists of two parts: mesoporous
carbon bubbles as a flexible skeleton and monodisperse amorphous zinc
oxide QDs (smaller than 3 nm) encapsulated in an amorphous carbon
matrix as a continuous coating tightly anchored on the surface of
mesoporous carbon bubbles. With the benefits of abundant active sites,
amorphous nature, high specific surface area, buffer effect, hierarchical
pores, stable interconnected conductive network, and multidimensional
electron transport pathways, the amorphous ZnO QD/mesoporous carbon
bubble composite delivers a high reversible capacity of nearly 930
mA h g<sup>β1</sup> (at current density of 100 mA g<sup>β1</sup>) with almost 90% retention for 85 cycles and possesses a good rate
performance. This work opens the possibility to fabricate high-performance
electrode materials for LIBs, especially for amorphous metal oxide-based
materials
Hollow Ball-in-Ball Co<sub><i>x</i></sub>Fe<sub>3β<i>x</i></sub>O<sub>4</sub> Nanostructures: High-Performance Anode Materials for Lithium-Ion Battery
The intrinsic electronic conductivity
can be improved by doping efficiently. Co<sub><i>x</i></sub>Fe<sub>3β<i>x</i></sub>O<sub>4</sub> nanostructures
have been synthesized for the first time to improve the conductivity
of lithium battery electrode. The solid solution Co<sub><i>x</i></sub>Fe<sub>3β<i>β</i>x</sub>O<sub>4</sub> were characterized by X-ray diffraction pattern (XRD), Raman spectrum,
scanning electron microscopy (SEM), transmission electron microscope
(TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry
(CV). The results show that the doping enlarge the lattice spacing
but the structure of Co<sub>3</sub>O<sub>4</sub> is stable in the
Li-ion intercalation/deintercalation process. The AC impedance spectrum
reveals the conductivity is well improved. In addition, the solid
solution Co<sub><i>x</i></sub>Fe<sub>3β<i>x</i></sub>O<sub>4</sub> exhibit excellent electrochemical characteristics.
The electrodes with 20% molar ratio of Fe ions own a reversible capacity
of 650.2 mA h g<sup>β1</sup> at a current density of 1 A g<sup>β1</sup> after 100 cycles
Free-Standing and Transparent Graphene Membrane of Polyhedron Box-Shaped Basic Building Units Directly Grown Using a NaCl Template for Flexible Transparent and Stretchable Solid-State Supercapacitors
Transparency has never been integrated
into freestanding flexible graphene paper (FF-GP), although FF-GP
has been discussed extensively, because a thin transparent graphene
sheet will fracture easily when the template or substrate is removed
using traditional methods. Here, transparent FF-GP (FFT-GP) was developed
using NaCl as the template and was applied in transparent and stretchable
supercapacitors. The capacitance was improved by nearly 1000-fold
compared with that of the laminated or wrinkled chemical vapor deposition
graphene-film-based supercapacitors