Bismuth (Bi) has been demonstrated as a promising anode
for Na-ion
batteries (NIBs) because it has high gravimetry (386 mA h g–1) and volumetric capacity (3800 mA h cm–3). However,
Bi suffers from large volume expansion during sodiation, leading to
poor electrochemical performance. The construction of a nanostructure
with sufficient void space to accommodate the volume change has been
proven effective for achieving prolonged cycling stability. However
the excessive void space will definitely decrease the volumetric energy
density of the battery. Herein, we design optimized Bi@Void@C nanospheres
(Bi@Void@C-2) with yolk–shell structure that exhibit the best
cycling performance and enhanced volumetric energy density. The optimized
void space not only could buffer the volume change of the Bi nanosphere
but also could keep the high volumetric energy density of the battery.
The Bi@Void@C-2 shows an excellent rate capacity of 173 mA h g–1 at ultrahigh current density of 100 A g–1 and long-cycle life (198 mA h g–1 at 20 A g–1 over 10 000 cycles). The origin of the superior
performance is achieved through in-depth fundamental studies during
battery operation using in situ X-ray diffraction
(XRD) and in situ transmission electron microscope
(TEM), complemented by theoretical calculations and ex situ TEM observation. Our rational design provides insights for anode
materials with large volume variation, especially for conversion type
and alloying type mechanism materials for batteries (i.e., Li-ion
batteries, Na-ion batteries).
High-purity hydrogen production by electrocatalytic overall water splitting plays an important role in energy conversion and storage. The development of high-performance bifunctional electrocatalysts that could simultaneously catalyze the cathodic hydrogen...
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