Synergistic effect from coaxially integrated CNTs@MoS2/MoO2 composite enables fast and stable lithium storage

Abstract

Molybdenum oxide/sulfide materials are extensively evaluated as high-capacity anode candidates for lithium ion batteries. However, they suffer from rapid capacity decay and poor kinetics. Herein, we report on synergistic effect from structurally integrated coaxial [email protected]2/MoO2 composite material on lithium storage, in which MoS2/MoO2 nanosheets are conformally decorated on carbon nanotubes (CNTs). In-situ synchrotron X-ray diffraction measurement is performed to elucidate synergistic effect among three MoS2, MoO2 and CNTs components for lithium storage. Reaction mechanism exploration reveals that the MoO2 component undergoes reversible Li+ intercalation via forming a stable Li0.98MoO2 phase over a voltage range of 3.0 to 0.01 V vs. Li+/Li, without experiencing the conversion reaction into metallic Mo, which contributes to long-term stability during charge/discharge cycles. Meanwhile, lithium storage of MoS2 is through lithium and sulfur reversible reaction after the initial conversion reaction of lithiated MoS2 forming Li2S and Mo. The CNTs component enhances electronic conductivity and structural stability by minimizing volume change and reaction strains in the [email protected]2/MoO2 composite anode. A desired 68.2% capacity retention upon 2000 cycles at 10 A/g has been demonstrated for the [email protected]2/MoO2 anode, revealing prominent reaction kinetics and structural stability for fast and stable lithium storage, superior to various Mo-based anode materials previously reported. The findings from this study, with the unique insight into the role of structural integrity in combining MoS2/MoO2 materials with the CNTs substrate, offers a strategy for designing composite anode materials for superior lithium storage performance.