Design and synthesis of few-layer molybdenum oxide selenide encapsulated in a 3D interconnected nitrogen-doped carbon anode toward high-performance sodium storage.

The main challenge for sodium storage is to find suitable host materials to accommodate larger-sized Na+ and conquer sluggish chemical kinetics. Herein, by adjusting the heat treatment environment, a novel few-layered molybdenum oxide selenide encapsulated in a three-dimensional (3D) N-doped carbon skeleton (MoO3–MoSe2–NC) is rationally constructed to improve the rate performances and cycle life for sodium-ion batteries (SIBs). A small quantity of MoO3 is generated on the edge of MoSe2via in situ local phase transformation by treatment temperature in the air, which effectively regulates the electronic structure, enhances the intrinsic conductivity, and provides more active sites of MoSe2 species. The layered NC acts as a nanoreactor to encapsulate MoO3–MoSe2, which not only effectively improves the conductivity of MoO3–MoSe2, shortens the diffusion pathway of Na+, but also alleviates the volumetric expansion effect of MoO3–MoSe2, playing a key role in providing structural stability for the electrode. Utilizing the phase and interface engineering, the MoO3–MoSe2–NC anode delivers a high specific capacity of 551 mA h g−1 at 0.1 A g−1 upon 150 cycles for SIBs, and a reversible capacity of 368 mA h g−1 is maintained even under 1 A g−1 after 600 cycles. By pairing with commercial Na3V2(PO4)3, this MoO3–MoSe2–NC also exhibits excellent performances in full cells. This study develops a universal interface manipulation strategy for the synthesis of anode materials to boost fast sodium storage kinetics. [ABSTRACT FROM AUTHOR]