As a promising anode candidate for sodium storage, the
adhibition
of metallic Bi is limited by severe volume expansion and modest conductivity.
To solve the issues, optimizing and designing both structures and
compositions of Bi-based anodes are highly necessary. Herein, Bi nanoparticles
encapsulated in N-doped porous carbon frameworks (Bi@NPC) are synthesized via a facile but efficient chemical blowing method. The
size and dispersion of Bi NPs in the interconnected carbon frameworks
are accurately adjusted through the control of reaction temperatures
and nitrogen doping. Thanks to its attractive structural/componential
merits, the optimized Bi@NPC anode shows that an excellent high-rate
capability of 207.6 mA h g–1 is achieved at a high
rate of 50 A g–1. In addition, it can still present
a stable reversible capacity of 243.9 mA h g–1 over
2000 cycles at 10 A g–1. Furthermore, the assembled
sodium-ion hybrid capacitors with Bi@NPC as the anode and commercial
active carbon as the cathode realize an exceptional energy/power density
of 94.2 W h kg–1/200 W kg–1 and
a low capacity decay rate of 0.014% per cycle for 2400 cycles at 1
A g–1. The contribution here will guide future design
of alloy-type anode materials toward advanced sodium-ion hybrid capacitors.