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.