Preparation, Enhanced Na+ Storage Performance and Mechanism of Sb/C Nanobilayer Film as Anode for Sibs by Magnetron Sputtering

Abstract

Antimony (Sb) is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, it suffers from significant volume expansion during sodiation process, leading to self-pulverization and decay of Na+ storage capacity upon cycling. Herein, Sb/C nanobilayer film (Sb layer: ~ 100 nm, C layer: ~ 50 nm) was directly deposited on a Cu current collector via magnetron sputtering. This model provides an effective approach not only to revealing the relationship between the thickness of Sb nanofilm and its Na+ storage properties, but also to uncovering the impact of C layer on Na+ storage performance of Sb nanofilm. Through sputtering C layer on Sb nanofilm, the volume expansion of Sb nanofilm during sodiation process was effectively buffered. When this Sb/C nanobilayer film is used as anode for SIBs, it demonstrates high specific capacity (712.8 mAh/g for initial reversible discharge at 500 mA/g between 0.01-2.50 V vs. Na/Na+), excellent cycling stability with negligible capacity degradation (retained at 713.2 mAh/g for 100th discharge) and remarkable rate performance (658.3 mAh/g at 5 A/g). The characteristics and microstructural evolution of Sb/C nanobilayer film during Na+ storage process were studied without the influence of traditional conductive agents and binders. Additionally, the adsorption, insertion and migration characteristics of Na+ in Sb/C nanobilayer film under alloying state were elucidated through systematic electrochemical tests combined with density functional theory (DFT) calculations. This study clarifies the potential Na+ storage mechanism in nano-heterostructure of Sb/C film, providing insights for designing high-performance Sb-C nanocomposite anodes for SIBs.

Keywords: Sb/C nanobilayer film, magnetron sputtering, Na+ storage properties, Sodium-ion batteries