Ferroelectricity Enhanced Ion Migration in Hard Carbon Anode for High-performance Potassium Ion Batteries

Abstract

Hard carbon is a promising candidate for potassium ion batteries due to its large interlayer spacing and abundant closed pores. However, the slow migration and sluggish diffusion kinetics of potassium ions lead to inferior insertion and pore filling processes, causing severe ion channel blocking, continuous byproduct generation, and poor cycling stability. In this study, we coated hard carbon on top of tetragonal barium titanate particles forming a ferroelectricity-aided anode (t-BTO@C). The spontaneous electrical field generated by t-BTO particles accelerated potassium ion kinetics. The rapid ion kinetics resulted in smaller oxidation potential and higher insertion-pore filling capacity. In addition, the t-BTO@C anode also shows much less byproduct generation. After 100 cycles at 0.05 A/g, the t-BTO@C anode shows a specific capacity of 374.9 mAh/g, higher than the SiO2@Carbon (97.2 mAh/g) and Pure Carbon (240.1 mAh/g). Paired with Prussian white cathode, the full cell shows a specific capacity of 313.0 mAh/g at 0.1 A/g, with 88.9% capacity retention after 40 cycles, much higher than recent reports. Our strategy provides new path to improve the performance of hard carbon anode in potassium ion batteries.