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 (GaS_x, x = 1.2) thin films by atomic layer deposition (ALD) onto single-walled carbon nanotube (SWCNT) powders. The ALD GaS_x was performed at 150 °C, and produced uniform and conformal amorphous films. The resulting core-shell, nanostructured SWCNT-GaS_x composite exhibited excellent electrochemical performance as an anode material for lithium-ion batteries (LIBs), yielding a stable capacity of ≈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 GaS_x 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 GaS_x coating offers short electronic and Li-ion pathways during cycling; 2) the amorphous structure of the ALD GaS_x 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. Single-walled carbon nanotubes (SWCNTs) are uniformly infiltrated and coated with amorphous GaS_x using atomic layer deposition (ALD). The resulting SWCNT-GaS_x, core-shell nanocomposites exhibit reliable cycling and sustained high capacity as lithium-ion battery anodes compared to pure SWCNTs and commercial microsized Ga₂S₃. This work demonstrates a general strategy for the design and synthesis of functional nanomaterials.