Exploring the sodium ion storage mechanism of gallium sulfide (Ga2S3): a combined experimental and theoretical approachElectronic supplementary information (ESI) available: XPS/EDS spectra and TEM images of Ga2S3, a comparison table of the characteristic parameters of different sulphide-based electrodes for SIB applications, a phase diagram of all the thermodynamically stable phases in the Ga-S-Na chemical system, and a few applications of K+ batteries. See DOI: 10.1039/c8nr09356c

• Main Authors: Wang, Pei, Liu, Miao, Mo, Fangjie, Long, Ziyao, Fang, Fang, Sun, Dalin, Zhou, Yong-ning, Song, Yun
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c8nr09356c

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 (Ga 2 S 3 ) as a novel SIB anode material for the first time. Ga 2 S 3 nanorods have been synthesized via the facile hydrothermal preparation of a GaOOH precursor with subsequent H 2 S annealing. Mixed with graphene upon electrode preparation, this Ga 2 S 3 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 Ga 2 S 3 , 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 Na 7 Ga 13 . 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. Developing sodium ion battery (SIB) anode materials of a low-cost and high-capacity nature for future large-scale applications still involves challenges.