Heterointerface-Induced Fast Na+ Transport of Sn Anode Using a Yolk-Shell Structure for Fast-Charging and Stable Sodium-Ion Batteries

Abstract

Sodium-ion battery (SIB) is a promising next-generation secondary battery system that uses inexpensive sodium resources, which can lower battery production costs. Moreover, based on similar chemical and electrochemical reaction mechanisms as conventional lithium-ion battery (LIB), it is expected that technology development can be rapidly achieved by utilizing existing battery manufacturing processes. However, because of the larger ionic radius (1.02 Å) and weight of sodium compared to those of lithium (0.76 Å), SIBs inevitably have lower energy and power densities compared to LIB. Therefore, to address these challenges, developing suitable host material with superior electrochemical performance (high capacity/high power density/long cyclability) is urgently required.In this regard, metallic Sn has attracted attention as a promising anode material with a high theoretical capacity of 870 mAh/g through the reversible electrochemical (de)alloying reaction with sodium, which could overcome the low energy density limit of hard carbon anode. Nevertheless, due to the interfacial instability of Sn particles upon cycling and the slow alloying reaction rate during the sodiation process, the Sn anode exhibits poor rate performance and insufficient long-term cycling stability. Additionally, the structural degradation caused by significant volume variations further limits its practical implementation in SIBs.Here, to solve the above issues, we propose a hierarchically designed composite anode consisting of Sn yolk and multifunctional C/SiOC shell (denoted as Sn@C/SiOC) via a simple pyrolysis method using the suspension of the Sn precursor in silicone oil. We conducted various physical, chemical, and electrochemical characterization, and we further carried out an in-depth investigation including post-mortem and in-situ EIS analyses to reveal the heterointerface-induced improved sodium-ion storage performance. We expect that the heterointerface modification strategy will contribute to the realization of advanced electrode materials in SIBs and other next-generation energy storage devices.