Gallium (III) sulfide as an active material in lithium secondary batteries

In an attempt to identify an active material for use in lithium secondary batteries with high energy density, we investigated the electrochemical properties of gallium (III) sulfide (Ga2S3) at 30 °C. Ga2S3 shows two sloping plateaus in the potential range between 0.01 V and 2.0 V vs. (Li/Li+). The specific capacity of the Ga2S3 electrode in the first delithiation is ca. 920 mAh g−1, which corresponds to 81% of the theoretical capacity (assuming a 10-electron reaction). The capacity in the 10th cycle is 63% of the initial capacity. Ex situ X-ray diffraction and X-ray absorption fine structure analyses revealed that the reaction of the Ga2S3 electrode proceeds in two steps: Ga2S3 + 6Li+ + 6e− ⇆ 2Ga + 3Li2S and Ga + xLi+ + xe− ⇆ LixGa.

Research highlights
► Ga2S3 is proposed as a novel anode active material in lithium secondary batteries.
► Lithiation/delithiation reactions of Ga2S3 occur during galvanostatic cycles.
► The reaction of Ga2S3 proceeds in two steps at 0.01–2.0 V vs. (Li/Li+).
► The specific capacity in the first delithiation is more than twice that of graphite.