Precise tuning of low-crystalline Sb@Sb2O3 confined in 3D porous carbon network for fast and stable potassium ion storage

Metal antimony (Sb) is a promising anode material of potassium-ion batteries (PIBs) for its high theoretical capacity but limited by its inferior cycle stability due to the serious volume expansion during cycling. Herein, we design and construct a kind of low-crystalline Sb nanoparticles coated with amorphous Sb2O3 and dispersed into three-dimensional porous carbon via a strategy involving NaCl template-assisted in-situ pyrolysis and subsequent low-temperature heat-treated in air. Significantly, the crystallinity and ratio of Sb/Sb2O3 have been precisely tuned and controlled, and the optimized sample of HTSb@Sb2O3@C-4 displays a high reversible specific capacity of 543.9 mAh g−1 at 0.1 A g−1, superior rate capability and excellent cycle stability (~273 mAh g−1 at 2 A g−1 after 2000 cycles) as an anode of PIBs. The outstanding potassium-ion storage performance can be ascribed to the appropriate crystallinity and the multiple-buffer-matrix structure comprising an interconnected porous conductive carbon to relieve the volume changes and suppress the aggregation of Sb, a Sb nanoparticle core to shorten the ion transport pathways and decrease the mechanical stress, and a low-crystalline Sb2O3 as the shell to consolidate the interface between Sb and carbon as well as facilitate the rapid electron transport. The dynamic analysis shows that the composite is mainly controlled by pseudocapacitance mechanism. This work provides a novel thought to design high-performance composite electrode in energy storage devices.