A new anode material for high rate and long life lithium/sodium storage

It is imperative to design suitable anode materials for both lithium-ion (LIBs) and sodium-ion batteries (SIBs) with a high-rate performance and ultralong cycling life. We fabricated a MoO₂/MoS₂ heterostructure that was then homogeneously distributed in N,S-doped carbon nanofibers (MoO₂/MoS₂@NSC) by electrospinning and sulfurization. The one-dimensional carbon fiber skeleton serves as a conductive frame to decrease the diffusion pathway of Li⁺/Na⁺, while the N/S doping creates abundant active sites and significantly improves the ion diffusion kinetics. Moreover, the deposition of MoS₂ nanosheets on the MoO₂ bulk phase produces an interface that enables fast Li⁺/Na⁺ transport, which is crucial for achieving high efficiency energy storage. Consequently, as the anode for LIBs, MoO₂/MoS₂@NSC gives an excellent cycling stability of 640 mAh g⁻¹ for 2 000 cycles under 5.0 A g⁻¹ with an ultralow average capacity drop of 0.002% per cycle and an exceptional rate capability of 614 mAh g⁻¹ at 10.0 A g⁻¹. In SIBs, it also produces a significantly better electrochemical performance (reversible capacity of 242 mAh g⁻¹ under 2.0 A g⁻¹ for 2 000 cycles and 261 mAh g⁻¹ under 5.0 A g⁻¹). This work shows how introducing a novel interface in the anode can produce rapid Li⁺/Na⁺ storage kinetics and a long cycling performance.