Germanium has a high theoretical capacity as an anode
material
for sodium-ion batteries. However, germanium suffers from large capacity
losses during cycling because of the large volume change and loss
of electronic conductivity. A facile way to prepare germanium anodes
is critically needed for next-generation electrode materials. Herein,
centrifugally spun binder-free N, S-doped germanium@ porous carbon
nanofiber (N, S-doped Ge@ PCNFs) anodes first were synthesized using
a fast, safe, and scalable centrifugal spinning followed by heat treatment
and N, S doping. The morphology and structure of the resultant N,
S-doped Ge@ PCNFs were investigated by scanning electron microscopy,
transmission electron microscopy, energy-dispersive X-ray mapping,
Raman spectroscopy, and X-ray diffraction, while electrochemical performance
of N, S-doped Ge@ PCNFs was studied using galvanostatic charge–discharge
tests. The results demonstrate that a nanostructured Ge homogeneously
distributed on tubular structured porous carbon nanofibers. Moreover,
N, S doping via thiourea treatment is beneficial for lithium- and
sodium-ion kinetics. While interconnected PCNFs buffered volume change
and provided fast diffusion channels for Li ions and Na ions, N, S-doped
PCNFs further improved electronic conductivity and thus led to higher
reversible capacity with better cycling performance. When investigated
as an anode for lithium-ion and sodium-ion batteries, high reversible
capacities of 636 and 443 mAhg–1, respectively,
were obtained in 200 cycles with good cycling stability. Centrifugally
spun binder-free N, S-doped Ge@ PCNFs delivered a capacity of 300
mAhg–1at a high current density of 1 A g–1, indicating their great potential as an anode material for high-performance
sodium-ion batteries.