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

Abstract

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.