Shape matters: SnP0.94 teardrop nanorods with boosted performance for potassium ion storage

Benefit from the unique structural characteristics of polymeric cross-linkage crystal with large interlayer spacing, SnP0.94 has been regarded as an appropriate dual conversion-alloying anode material, providing symmetric high-speed ion diffusion tunnels perpendicular to the c-axis of the hexagonal lattice. However, the critical issue of volume change stemming from fully alloying-dealloying reaction still need to be challenged. We report the first example of uniform SnP0.94 teardrop nanorods by utilizing bismuth (Bi) as a seed through the one-pot synthesis method in supercritical organic solvent. The Bi-seed SnP0.94 teardrop nanorod anode exhibited a high reversible capacity of 422.8 mA h g(-1) at 50 mA g(-1) and excellent rate performance (285.8 mA h g(-1) at 1000 mA g(-1)), which is superior to the other reported SnP0.94 nanomaterials. Based on the results of electrochemical impedance spectroscopy (EIS) assisted with ex-situ transmission electron microscope (TEM) and ex-situ X-ray photoelectron spectroscopy (XPS), teardrop-shaped nanostructures can more effectively relieve the surface tension, alleviate the expansion, and maintain structural stability during cycling than spherical particles with similar sizes, demonstrating strong evidence on its shape effects on electrochemical performance. Finally, the potassium ion batteries with SnP0.94 teardrop nanorods (designated as T-SnP) as an anode and perylenetetracarboxylic dianhydride (PTCDA) as a cathode to full cells delivered a long cycling life of up to 450 cycles at a current density of 1000 mA g(-1), moreover, a pouch-type battery is also fabricated for feasible demonstration for its practical application.

Automated summary

By utilizing bismuth as a seed, uniform SnP0.94 teardrop nanorods were successfully synthesized, exhibiting high reversible capacity and excellent rate performance as an anode material. The shape of the nanorods has a significant impact on their electrochemical performance, demonstrating the ability to effectively maintain structural stability during cycling.