Gallium Sulfide-Single-Walled Carbon Nanotube Composites: High-Performance Anodes for Lithium-Ion Batteries

Metal sulfides are an important class of functional materials possessing exceptional electrochemical performance and thus hold great promise for rechargeable secondary batteries. In this work, we deposited gallium sulfide (GaSx, x = 1.2) thin films by atomic layer deposition (ALD) onto single-walled carbon nanotube (SWCNT) powders. The ALD GaSx was performed at 150 degrees C, and produced uniform and conformal amorphous films. The resulting core-shell, nanostructured SWCNT-GaSx composite exhibited excellent electrochemical performance as an anode material for lithium-ion batteries (LIBs), yielding a stable capacity of approximate to 575 mA g(-1) at a current density of 120 mA g(-1) in the voltage window of 0.01-2 V, and an exceptional columbic efficiency of >99.7%. The GaSx component of the composite produced a specific capacity of 766 mA g(-1), a value two times that of conventional graphite anodes. We attribute the excellent electrochemical performance of the composite to four synergistic effects: 1) the uniform and conformal ALD GaSx coating offers short electronic and Li-ion pathways during cycling; 2) the amorphous structure of the ALD GaSx accommodates stress during lithiation-delithiation processes; 3) the mechanically robust SWCNT framework also accommodates stress from cycling; 4) the SWCNT matrix provides a continuous, high conductivity network.