Multiple templates fabrication of hierarchical porous carbon for enhanced rate capability in potassium-ion batteries

Abstract

Potassium-ion batteries (PIBs) are attracting more and more attention as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage owing to the abundance and low price of potassium. However, it is still challenging to achieve high capacity and rate capability for the current electrode materials in view of the sluggish potassiation kinetics. In this study, a simple multiple templates strategy is applied to obtain the hierarchical porous carbon (HPC) material as a novel anode for PIBs after the pyrolysis and washing of polyacrylate (PAA) composed of NaCl crystals and Zn nanoparticles. The resulting HPC possesses a hierarchical porous construction with a typical hard carbon feature, abundant structural defects, a high Brunauer-Emmett-Teller (BET) surface area (604.4 m2 g−1), and an enlarged interlayer distance (0.395 nm). These characteristics can augment potassium ion storage, exhibiting a moderate charge capacity of 211.5 mA h g−1 after 50 cycles at 50 mA g−1 with excellent rate capability of 76.7 mA h g−1 at 10 A g−1. To investigate the crucial effect of hierarchical porosity, cyclic voltammogram measurements are conducted to verify the contributions of surface-dominated K-storage and the apparent diffusion coefficient. The potassium storage mechanism during the intercalation process of potassium ions is also investigated by ex situ SEM, XRD and HRTEM characterizations. Regarding the cost-effectiveness and sustainability, this work shows a promising development of anode materials for PIBs.