Heterostructure Design of Anode Materials for High-Performance Sodium-Ion Batteries

Abstract

The growing global demand for carbon neutrality has led to an increase in the use of electric vehicles and large-scale energy storage systems, which rely heavily on lithium-ion batteries. However, there are concerns about the limited availability of lithium resources, which may result in depletion and price increases in the near future. To solve this issue, researchers are actively exploring alternative next-generation secondary battery systems to replace current lithium-ion batteries. Sodium-ion batteries have received significant attention as one of promising candidates, as sodium is abundant in the earth's crust and economically viable compared to lithium.Although hard carbon has been considered a reversible anode material capable of sodium-ion insertion and extraction, high-capacity anode materials are required to increase the energy density of sodium-ion batteries. Among various candidates, conversion- and alloy-based materials are highly regarded due to their high theoretical capacity. However, challenges such as huge volume changes of active materials, sluggish reaction rates, and interfacial instability that occur during charging and discharging need to be overcome for these materials to be applied in high-performance sodium-ion batteries.To address these challenges, herein, we designed heterostructured anodes with a unique structure by combining conversion- or alloy-based materials with a porous silicon oxycarbide (SiOC) nanocoating layer, which possesses high surface capacitive reactivity and mechanical strength. We controlled the dispersion of the precursors in silicon oil and performed heat treatment to synthesize high-capacity heterostructured composites (MoS2@SiOC and Sn@SiOC). Subsequently, we conducted extensive physicochemical and electrochemical characterization as well as post-mortem analysis to investigate the properties of these composites, with a specific focus on the impact of the heterostructure on their battery performance. We anticipate that this heterostructure approach will pave the way for the development of novel, high-performance anode materials for sodium-ion batteries in the future.