Optimized Ga-based nanocomposite for superior Li-ion battery anodes

Abstract

Among the various liquid metals, Ga has unique properties, such as a low melting temperature, fluidity, and non-toxicity. In addition, Ga can alloy with Li to form a Li2Ga phase, which can be applied to high-capacity anodes for Li-ion batteries (LIBs). However, Ga-based materials readily melt and agglomerate during lithiation/delithiation owing to their low melting temperature and high surface energy, resulting in poor cycling stability. In this study, two structural types of Ga, crystalline and amorphous, were selected and electrochemically investigated as LIB anodes. Subsequently, to address the melting and agglomeration issues of the Ga anode, an optimized Ga-based nanocomposite was developed using a novel synthetic concept, namely a solid-state alloying–dealloying process. This process involves an alloying reaction of Ga and Ti to form various Ga–Ti compounds, such as Ga3Ti, Ga2Ti, and Ga3Ti2, and a dealloying reaction with amorphous C to form a nanocomposite comprising evenly dispersed amorphous Ga and Li-inactive TiC in the amorphous C matrix. The Li-inactive TiC and amorphous C matrix in the nanocomposite effectively confined amorphous Ga, thereby preventing the problems caused by its melting and agglomeration during cycling. In addition, an interesting transformation behavior of amorphous Ga into electrochemically stabilized Ga nanocrystallites (approximately 2–3 nm) was demonstrated during cycling, contributing to the high electrochemical performance. The Ga-based nanocomposite exhibited a superior electrochemical performance. This study proposes a better understanding of high-performance Ga-based anodes for LIBs as well as an effective fabrication method for high-performance nanocomposites by solid-state alloying–dealloying.