Transition-metal
sulfides (TMSs) powered by conversion and/or alloying
reactions are considered to be promising anode materials for advanced
lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However,
the limited electronic conductivity and large volume expansion severely
hinder their practical application. Herein, we report a covalent coupling
strategy for TMS-based anode materials using amide linkages to bind
TMSs and carbon nanotubes (CNTs). In the synthesis, the thiourea acts
as not only the capping agent for morphology control but also the
linking agent for the covalent coupling. As a proof of concept, the
covalently coupled ZnS/CNT composite (CC-ZnS/CNT) has been prepared,
with ZnS nanoparticles (∼10 nm) tightly anchored on CNT bundles.
The compact ZnS-CNT heterojunctions are greatly beneficial to facilitating
the electron/ion transfer and ensuring structural stability. Due to
the strong coupling interaction between ZnS and CNTs, the composite
presents prominent pseudocapacitive behavior and highly reversible
electrochemical processes, thus leading to superior long-term stability
and excellent rate capability, delivering reversible capacities of
333 mAh g–1 at 2 A g–1 over 4000
cycles for LIBs and 314 mAh g–1 at 5 A g–1 after 500 cycles for SIBs. Consequently, CC-ZnS/CNT exhibits great
competence for applications in LIBs and SIBs, and the covalent coupling
strategy is proposed as a promising approach for designing high-performance
anode materials.
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