Multipod Bi(Cu 2-x S) n Nanocrystals formed by Dynamic Cation-Ligand Complexation and Their Use as Anodes for Potassium-Ion Batteries.

We report the formation of an intermediate lamellar Cu-thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu 2- x S) n heterostructures with a tunable number of Cu 2- x S stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu-thiolate complex. Increasing the stability of the Cu-thiolate results in single Cu 2- x S stem formation, and decreased stability of the Cu-thiolate complex increases the degree of heteronucleation to form multiple Cu 2- x S stems on the Bi core. Spatially separated multiple Cu 2- x S stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g -1 after 200 cycles compared to ∼111 mAh·g -1 for Bi-Cu 2- x S single-stem heterostructures.