Transition
metal sulfides and oxides with high theoretical capacities
have been regarded as promising anode candidates for a sodium-ion
battery (SIB); however, they have critical issues including sluggish
electrochemical kinetics and poor long-term stability. Herein, a dual
carbon design strategy is proposed to integrate with highly active
heterojunctions to overcome the above issues. In this new design,
CoS2/CoO hollow dodecahedron heterojunctions are sandwiched
between open framework carbon-spheres (OFCs) and a reduced graphene
oxide (rGO) nanomembrane (OFC@CoS2/CoO@rGO). The CoS2/CoO heterojunctions effectively promote electron transfer
on their surface and provide more electrochemical active sites through
their hierarchical hollow structures assembled by nanodots. Meanwhile,
the dual-carbon framework forms a highly conductive network that enables
a better rate capability. More importantly, the dual carbon can greatly
buffer volume expansion and stable reaction interfaces of electrode
material during the charge/discharge process. Benefitting from their
synergistical effects, the OFC@CoS2/CoO@rGO electrode achieves
a high reversible capacity of 460 mAh g–1 at 0.05
A g–1 and still maintains 205.3 mAh g–1 even when current density is increased by 200 times when used as
an anode material for SIBs. Their cycling property is also remarkable
with a maintained capacity of 161 mAh g–1 after
3500 charging/discharging cycles at a high current density of 1 A
g–1. The dual-carbon strategy is demonstrated to
be effective for enhanced reaction kinetics and long-term cycling
property, providing siginificant guidance for preparing other high-performance
electrode materials.