Colloidal Nanocrystals of Lithiated Group 14 Elements

The synthesis of colloidal nanocrystals (NCs) of lithiated group 14 elements (Z=Si, Ge, and Sn) is reported, which are Li 4.4 Si, Li 3.75 Si, Li 4.4 Ge, and Li 4.4 Sn. Li x Z compounds are highly reactive and cannot be synthesized by existing methods. The success relied on separating the surface protection from the crystal formation and using a unique passivating ligand. Bare Li x Z crystals were first produced by milling elemental Li and Z in an argon‐filled jar. Then, under the assistance of additional milling, hexyllithium was added to passivate the freshly generated Li x Z NCs. This ball‐milling‐assisted surface protection method may be generalized to similar systems, such as Na x Z and K x Z. Moreover, Li 4.4 Si and Li 4.4 Ge NCs were conformally encapsulated in carbon fibers, providing great opportunities for studying the potential of using Li x Z to mitigate the volume‐fluctuation‐induced poor cyclability problem confronted by Z anodes in lithium‐ion batteries.