Antimony (Sb) has been pursued as a promising anode material
for
sodium-ion batteries (SIBs). However, it suffers from severe volume
expansion during the sodiation–desodiation process. Encapsulating
Sb into a carbon matrix can effectively buffer the volume change of
Sb. However, the sluggish Na+ diffusion kinetics in traditional
carbon shells is still a bottleneck for achieving high-rate performance
in Sb/C composite materials. Here we design and synthesize a yolk–shell
Sb@Void@graphdiyne (GDY) nanobox (Sb@Void@GDY NB) anode for high-rate
and long cycle life SIBs. The intrinsic in-plane cavities in GDY shells
offer three-dimensional Na+ transporting channels, enabling
fast Na+ diffusion through the GDY shells. Electrochemical
kinetics analyses show that the Sb@Void@GDY NBs exhibit faster Na+ transport kinetics than traditional Sb@C NBs. In
situ transmission electron microscopy analysis reveals that
the hollow structure and the void space between Sb and GDY successfully
accommodate the volume change of Sb during cycling, and the plastic
GDY shell maintains the structural integrity of NBs. Benefiting from
the above structural merits, the Sb@Void@GDY NBs exhibit excellent
rate capability and extraordinary cycling stability.
Bismuth (Bi) has emerged as a promising anode material
for fast-charging
and long-cycling sodium-ion batteries (SIBs). However, its dramatically
volumetric variations during cycling will undesirably cause the pulverization
of active materials, severely limiting the electrochemical performance
of Bi-based electrodes. Constructing hollow nanostructures is recognized
as an effective way to resolve the volume expansion issues of alloy-type
anodes but remains a great challenge for metallic bismuth. Here, we
report a facile iodine-ion-assisted galvanic replacement approach
for the synthesis of Bi nanotubes (NTs) for high-rate, long-term and
high-capacity sodium storage. The hollow tubular structure effectively
alleviates the structural strain during sodiation/desodiation processes,
resulting in excellent structural stability; the thin wall and large
surface area enable ultrafast sodium ion transport. Benefiting from
the structural merits, the Bi NT electrode exhibits extraordinary
rate capability (84% capacity retention at 150 A g–1) and outstanding cycling stability (74% capacity retention for 65,000
cycles at 50 A g–1), which represent the best rate
performance and longest cycle life among all reported anodes for SIBs.
Moreover, when coupled with the Na3(VOPO4)2F cathode in full cells, this electrode also demonstrates
excellent cycling performance, showing the great promise of Bi NTs
for practical application. A combination of advanced research techniques
reveals that the excellent performance originates from the structural
robustness of the Bi NTs and the fast electrochemical kinetics during
cycling.
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