3 research outputs found
Porous Graphene Nanoarchitectures: An Efficient Catalyst for Low Charge-Overpotential, Long Life, and High Capacity Lithium–Oxygen Batteries
The electrochemical performance of
lithium–oxygen (Li–O<sub>2</sub>) batteries awaits dramatic
improvement in the design of porous
cathode electrodes with sufficient spaces to accommodate the discharge
products and discovery of effective cathode catalysts to promote both
oxygen reduction reactions and oxygen evolution reactions. Herein,
we report the synthesis of porous graphene with different pore size
architectures as cathode catalysts for Li–O<sub>2</sub> batteries.
Porous graphene materials exhibited significantly higher discharge
capacities than that of nonporous graphene. Furthermore, porous graphene
with pore diameter around 250 nm showed the highest discharge capacity
among the porous graphene with the small pores (about 60 nm) and large
pores (about 400 nm). Moreover, we discovered that addition of ruthenium
(Ru) nanocrystals to porous graphene promotes the oxygen evolution
reaction. The Ru nanocrystal-decorated porous graphene exhibited an
excellent catalytic activity as cathodes in Li–O<sub>2</sub> batteries with a high reversible capacity of 17 700 mA h
g<sup>–1</sup>, a low charge/discharge overpotential (about
0.355 V), and a long cycle life up to 200 cycles (under the curtaining
capacity of 1000 mAh g<sup>–1</sup>). The novel porous graphene
architecture inspires the development of high-performance Li–O<sub>2</sub> batteries
Microwave-assisted Synthesis of Mesoporous Co<sub>3</sub>O<sub>4</sub> Nanoflakes for Applications in Lithium Ion Batteries and Oxygen Evolution Reactions
Mesoporous Co<sub>3</sub>O<sub>4</sub> nanoflakes with an interconnected architecture
were successfully synthesized using a microwave-assisted hydrothermal
and low-temperature conversion method, which exhibited excellent electrochemical
performances as anode materials in lithium ion batteries and as catalysts
in the oxygen evolution reaction (OER). Field-emission scanning electron
microscopy (FESEM) and transmission electron microscopy (TEM) observations
showed the unique interconnected and mesoporous structure. When employed
as anode materials for lithium ion batteries, mesoporous Co<sub>3</sub>O<sub>4</sub> nanoflakes delivered a high specific capacity of 883
mAh/g at 0.1C current rate and stable cycling performances even at
higher current rates. Post-mortem analysis of <i>ex situ</i> FESEM images revealed that the mesoporous and interconnected structure
had been well maintained after long-term cycling. The mesoporous Co<sub>3</sub>O<sub>4</sub> nanoflakes also showed both OER active properties
and good catalytic stability. This could be attributed to both the
stability of unique mesoporous structure and highly reactive facets
Cross-Linking Hollow Carbon Sheet Encapsulated CuP<sub>2</sub> Nanocomposites for High Energy Density Sodium-Ion Batteries
Sodium-ion
batteries (SIB) are regarded as the most promising competitors
to lithium-ion batteries in spite of expected electrochemical disadvantages.
Here a “cross-linking” strategy is proposed to mitigate
the typical SIB problems. We present a SIB full battery that exhibits
a working potential of 3.3 V and an energy density of 180 Wh kg<sup>–1</sup> with good cycle life. The anode is composed of cross-linking
hollow carbon sheet encapsulated CuP<sub>2</sub> nanoparticles (CHCS-CuP<sub>2</sub>) and a cathode of carbon coated Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F<sub>3</sub> (C-NVPF). For the preparation
of the CHCS-CuP<sub>2</sub> nanocomposites, we develop an <i>in situ</i> phosphorization approach, which is superior to mechanical
mixing. Such CHCS-CuP<sub>2</sub> nanocomposites deliver a high reversible
capacity of 451 mAh g<sup>–1</sup> at 80 mA g<sup>–1</sup>, showing an excellent capacity retention ratio of 91% in 200 cycles
together with good rate capability and stable cycling performance. <i>Post mortem</i> analysis reveals that the cross-linking hollow
carbon sheet structure as well as the initially formed SEI layers
are well preserved. Moreover, the inner electrochemical resistances
do not significantly change. We believe that the presented battery
system provides significant progress regarding practical application
of SIB