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/Bi 2 O 3 nanodots enriched in suitable outer amorphous carbon sheets (Bi/Bi 2 O 3 NDs@CSs) is first proposed to alleviate volume variations and accelerate stable charge transport to boost K + storage performance. The introduction of proper Bi 2 O 3 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/Bi 2 O 3 NDs@CSs with double protection of carbon sheets and Bi 2 O 3 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/Bi 2 O 3 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.