For most alloying- and conversion-type anode materials,
a huge
volume expansion and structure degradation of the electrodes always
hinder their applications. In this work, a novel core–shell–shell
Sb2S3/Sb@TiO2@C nanorod composite
has been designed layer by layer, which includes an inner Sb2S3/Sb heterostructure core protected by an oxygen-deficient
TiO2 shell and a conductive carbon shell. It is interesting
to observe that, during the carbothermic reduction process, the previous
Sb2S3 nanorod cores are partially reduced into
a metallic Sb phase and the reduced TiO2 also creates many
oxygen vacancies, which can greatly enhance the conductivity of the
semiconductor Sb2S3. Thanks to the double effects
of the TiO2 middle shell and carbon outer shell, the unique
double-shelled structure design creates an enhanced dual protection,
which can better accommodate the volume-expansive deformation and
preserve the structural integrity of the active Sb2S3/Sb core. Especially, the TiO2 middle layer is
self-assembled by numerous nanoparticles acting as a nanopillar backbone,
which supports between the nanorod core and outer carbon shell to
better buffer the volume changes. As a result, the core–shell–shell
Sb2S3/Sb@TiO2@C anode shows lithium
and sodium storage performances superior to those of the pristine
Sb2S3 and core–shell Sb2S3@TiO2 electrodes. For lithium-ion batteries, the
Sb2S3/Sb@TiO2@C nanorod composite
achieves an initial discharge/recharge capacity of 1244.9/1005.1 mAh
g–1 with an initial Coulombic efficiency of about
80.7%, an enhanced rate capability with a capacity of 593.2 mA h g–1 at 5.0 A g–1, and prolonged cycling
life for 500 cycles with a reversible capacity of 495.8 mAh g–1 at 0.5 A g–1. For sodium-ion batteries,
the nanorodalso exhibits an improved performance with an initial discharge/recharge
capacity of 781.4/574.0 mAh g–1 (initial Coulombic
efficiency of about 73.46%) and cycling for 400 cycles with a reversible
capacity of 422.6 mAh g–1 at 0.8 A g–1. This research sheds light upon double-shell structure designs with
an effective middle shell to enhance the energy storage performance
of electrode materials.