Fast and Long-Lasting Potassium-Ion Storage Enabled by Rationally Engineering Strain-Relaxation Bi/Bi2O3 Nanodots Embedded in Carbon Sheets

Abstract

Bismuth (Bi)-based materials merit high theoretical volumetric specific capacity (3800 mAh mL⁻1) but suffer from huge volume variations and sluggish reaction kinetics during cycling. Herein, the optimal framework of Bi/Bi2O3 nanodots enriched in suitable outer amorphous carbon sheets (Bi/Bi2O3 NDs@CSs) is first proposed to alleviate volume variations and accelerate stable charge transport to boost K+ storage performance. The introduction of proper Bi2O3 not only provides an efficient K+ adsorption path, but also effectively buffers volume changes via conversion reaction. Accordingly, the as-prepared anode exhibits a remarkable rate capability (149.3 mAh g−1 at 60 A g−1, 42% capacity retention with a 120-fold current-density increase) and extraordinary durability (1800 cycles at 5.0 A g−1, 95% capacity retention), among the best rate and cycling performance to date in potassium ion batteries (PIBs) anodes. Theoretical calculations reveal the feasible structures of Bi/Bi2O3 NDs@CSs with double protection of carbon sheets and Bi2O3 are conducive to enhance charge transfer and efficiency of electrochemical reaction. Substantial in situ/ex situ characterizations and finite element simulation further unveil high reversibility and robust mechanical behavior of Bi/Bi2O3 NDs@CSs, favorable for the reinforcement of structural stability. This study provides new insights into developing high-performance and durable Bi-based anodes for PIBs.