Small PbS Nanocubes Embedded in Carbon Shells for Na Storage

Carbonaceous materials suffer from low capacity when applied as an anode in sodium-ion batteries. Constructing metal sulfides/carbon composites can address the above issue but leads to limited cycle stability and sluggish kinetics. In the current work, ultrasmall PbS nanocubes embedded in a carbon framework (named PbSnc@C) are synthesized by combining emulsion polymerization, electrostatic interaction promoted adsorption, and in situ carbothermal reduction. PbSnc@C has a uniform spherical morphology and well-developed pore structure, with 20 nm PbS cubes dispersed in the carbon framework. As such, it displays a fast Na+ transfer rate, shortened Na+ diffusion radius, and optimal structural merits to alleviate the volume change during the sodiation/desodiation process. When employed as a sodium-ion battery anode, PbSnc@C demonstrates a large capacity of 332 mAh g–1 at 0.1 A g–1, superior rate capability with a remarkable capacity of 145 mAh g–1 at 20 A g–1, and good electrochemical stability during a 2000-cycle repeated charge/discharge process. Moreover, the in-depth study indicates that the Na+ storage in PbSnc@C follows a two-step mechanism: (i) the conversion reaction between PbS and Na+, leading to the formation of Pb metal and Na2S, and (ii) an alloying of Pb and Na+.