Exploring the sodium ion storage mechanism of gallium sulfide (Ga2S3): a combined experimental and theoretical approach

Abstract

Developing sodium ion battery (SIB) anode materials of a low-cost and high-capacity nature for future large-scale applications still involves challenges. Herein, we have reported gallium sulfide (Ga₂S₃) as a novel SIB anode material for the first time. Ga₂S₃ nanorods have been synthesized via the facile hydrothermal preparation of a GaOOH precursor with subsequent H₂S annealing. Mixed with graphene upon electrode preparation, this Ga₂S₃ electrode maintains a reversible specific capacity of 476 mA h g⁻¹ after 100 cycles at a current density of 0.4 A g⁻¹, with a coulombic efficiency of over 99%. Ex situ XRD analysis and theoretical calculations are employed to comprehensively elucidate the detailed sodium ion storage mechanism of Ga₂S₃, which is composed of initial Na⁺ intercalation, a subsequent multi-step conversion reaction between S and Na⁺, and an eventual alloying reaction between Ga and Na⁺ with the end product of Na₇Ga₁₃. Further kinetics analysis has demonstrated that the conversion reaction is the rate-limiting step due to a multi-step reaction with the intermediate phase of GaS. Moreover, the appearance of liquid metal Ga, as confirmed via TEM observations and theoretical calculations, can serve as a self-healing agent that repairs cracks in the electrode. Our findings shed light on the further design of Ga-based materials, and they also can be extended to solid-state-battery systems.