Hierarchical Sb₂MoO₆ microspheres for high-performance sodium-ion battery anode

Antimony (Sb)-based materials have been extensively studied as anodes for sodium-ion batteries (SIBs) because of the high theoretical capacity of Sb (660 mA h/g). However, the poor electrochemical behaviors caused by the severe volume expansion of Sb during the sodiation/desodiation process constrains its practical applications. Herein we report a facile microwave-assisted hydrothermal method for the synthesis of hierarchical Sb₂MoO₆ microspheres assembled by one-dimensional nanobelts without the use of any surfactants. When used as an anode material for SIBs, it delivers large reversible capacities of 637.3 and 498.7 mA h/g at current densities of 200 and 1000 mA/g after 100 cycles, respectively, exceptional rate capability with 428.1 mA h/g retained at 5 A/g and long cycle life (460.6 mA h/g with capacity retention of 98.7% after 450 cycles at 2 A/g). Moreover, a sodium-ion full cell with Sb₂MoO₆ anode was assembled, presenting a large capacity and stable cyclability with a high output voltage. Based on extensive experimental analyses and first-principles calculations, we find that such superior electrochemical performances can be attributed to its distinctive capability of forming a self-constructing conductive Na-Mo-O buffer matrix during discharge/charge process, which not only efficiently buffers the volume expansion of the Na-Sb alloying/dealloying, but also provides good electronic conductivity to facilitate electron transfer. Notably, the novel hierarchical Sb₂MoO₆ microsphere anode exhibits excellent electrochemical performances without hybridizing with any special carbonaceous materials. Such high-performance novel anode material together with the new findings in electrochemical mechanism in this work may open a way for the design of future energy storage devices.