A "Biconcave-Alleviated" Strategy to Construct <i>Aspergillus niger</i>-Derived Carbon/MoS₂ for Ultrastable Sodium Ion Storage.

Abstract

Two-dimensional layered materials commonly face hindered electron transfer and poor structure stability, thus limiting their application in high-rate and long-term sodium ion batteries. In the current study, we adopt finite element simulation to guide the rational design of nanostructures. By calculating the von Mises stress distribution of a series of carbon materials, we find that the hollow biconcave structure could effectively alleviate the stress concentration resulting from expansion. Accordingly, we propose a biconcave-alleviated strategy based on the <i>Aspergillus niger</i>-derived carbon (ANDC) to construct ANDC/MoS₂ with a hollow biconcave structure. The ANDC/MoS₂ is endowed with an excellent long-term cyclability as an anode of sodium ion batteries, delivering a discharge capacity of 496 mAh g^-1 after 1000 cycles at 1 A g^-1. A capacity retention rate of 94.5% is achieved, an increase of almost seven times compared with the bare MoS₂ nanosheets. Even at a high current density of 5 A g^-1, a reversible discharge capacity around 400 mAh g^-1 is maintained after 300 cycles. ANDC/MoS₂ could also be used for efficient lithium storage. By using <i>in situ</i> TEM, we further reveal that the hollow biconcave structure of ANDC/MoS₂ has enabled stable and fast sodiation/desodiation.