4 research outputs found
Hierarchical Micron-Sized Mesoporous/Macroporous Graphene with Well-Tuned Surface Oxygen Chemistry for High Capacity and Cycling Stability Li–O<sub>2</sub> Battery
Nonaqueous Li–O<sub>2</sub> battery is recognized as one of the most promising energy storage
devices for electric vehicles due to its super-high energy density.
At present, carbon or catalyst-supporting carbon materials are widely
used for cathode materials of Li–O<sub>2</sub> battery. However,
the unique electrode reaction and complex side reactions lead to numerous
hurdles that have to be overcome. The pore blocking caused by the
solid products and the byproducts generated from the side reactions
severely limit the capacity performance and cycling stability. Thus,
there is a great need to develop carbon materials with optimized pore
structure and tunable surface chemistry to meet the special requirement
of Li–O<sub>2</sub> battery. Here, we propose a strategy of
vacuum-promoted thermal expansion to fabricate one micron-sized graphene
matrix with a hierarchical meso-/macroporous structure, combining
with a following deoxygenation treatment to adjust the surface chemistry
by reducing the amount of oxygen and selectively removing partial
unstable groups. The as-made graphene demonstrates dramatically tailored
pore characteristics and a well-tuned surface chemical environment.
When applied in Li–O<sub>2</sub> battery as cathode, it exhibits
an outstanding capacity up to 19 800 mA h g<sup>–1</sup> and
is capable of enduring over 50 cycles with a curtaining capacity of
1000 mA h g<sup>–1</sup> at a current density of 1000 mA g<sup>–1</sup>. This will provide a novel pathway for the design
of cathodes for Li–O<sub>2</sub> battery
Low-Cost Room-Temperature Synthesis of NaV<sub>3</sub>O<sub>8</sub>·1.69H<sub>2</sub>O Nanobelts for Mg Batteries
Potentially
safe and economically feasible magnesium batteries (MBs) have attracted
tremendous research attention as an alternative to high-cost and unsafe
lithium ion batteries. In the current work, for the first time, we
report a novel room-temperature approach to dope the atomic species
sodium between the vanadium oxide crystal lattice to obtain NaV<sub>3</sub>O<sub>8</sub>·1.69H<sub>2</sub>O (NVO) nanobelts. The
synthesized NVO nanobelts are used as electrode materials for MBs.
The MB cells demonstrate stable discharge specific capacity of 110
mA h g<sup>–1</sup> at a current density of 10 mA g<sup>–1</sup> and a high cyclic stability, that is 80% capacity retention after
100 cycles, at a current density of 50 mA g<sup>–1</sup>. Moreover,
the effects of cutoff voltages (ranging from 2 to 2.6 V) on their
electrochemical performance were investigated. The reason for the
limited specific capacity of MBs is attributed to the trapping of
Mg ions inside the NVO lattices. This work opens up a new pathway
to explore different electrode materials for MBs with improved electrochemical
performance
Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li–O<sub>2</sub> Batteries
Although
various kinds of catalysts have been developed for aprotic
Li–O<sub>2</sub> battery application, the carbon-based cathodes
are still vulnerable to attacks from the discharge intermediates or
products, as well as the accompanying electrolyte decomposition. To
ameliorate this problem, the free-standing and carbon-free CoO nanowire
array cathode was purposely designed for Li–O<sub>2</sub> batteries.
The single CoO nanowire formed as a special mesoporous structure,
owing even comparable specific surface area and pore volume to the
typical Super-P carbon particles. In addition to the highly selective
oxygen reduction/evolution reactions catalytic activity of CoO cathodes,
both excellent discharge specific capacity and cycling efficiency
of Li–O<sub>2</sub> batteries were obtained, with 4888 mAh
g<sub>CoO</sub><sup>–1</sup> and 50 cycles during 500 h period.
Owing to the synergistic effect between elaborate porous structure
and selective intermediate absorption on CoO crystal, a unique bimodal
growth phenomenon of discharge products was occasionally observed,
which further offers a novel mechanism to control the formation/decomposition
morphology of discharge products in nanoscale. This research work
is believed to shed light on the future development of high-performance
aprotic Li–O<sub>2</sub> batteries
Layer-by-Layer Assembled C/S Cathode with Trace Binder for Li–S Battery Application
The C/S cathode with only 0.5 wt
% binder, composed with Nafion and PVP, was assembled layer-by-layer
for lithium–sulfur battery (Li–S) application. It achieved
excellent binding strength and battery performance compared to the
cathode with 10 wt % PVDF, which is promising to further increase
the practical energy density of Li–S batteries