Ultrafine TiO2 Nanoparticle Supported Nitrogen‐Rich Graphitic Porous Carbon as an Efficient Anode Material for Potassium‐Ion Batteries

Abstract

Potassium‐ion batteries (KIBs) have attracted enormous attention as a next‐generation energy storage system due to their low cost, fast ionic conductivity within electrolytes, and high operating voltage. However, developing suitable electrode materials to guarantee high‐energy output and structural stability to ensure long cycling performance remains a critical challenge. Herein, anatase TiO2 nanoparticles are encapsulated in nitrogen‐rich graphitic carbon (TiO2@NGC) with hierarchical pores and high surface area (250 m2 g−1) using the Ti‐based metal–organic framework NH2‐MIL‐125 (Ti8O8(OH)4(NH2‐bdc)6 with NH2‐bdc2− = 2‐amino‐1,4‐benzenedicarboxylate) as a sacrificial template. Serving as the anode material in a K‐ion half‐cell, TiO2@NGC delivers a high capacity of 228 mA h g−1 with remarkable cycling performance (negligible loss over 2000 cycles with more than 98% Coulombic efficiency). The charge‐storing mechanism is underpinned using ex situ characterization techniques such as ex situ X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. It is revealed that the original TiO2 phase gets transformed to the anorthic Ti7O13 and monoclinic K2Ti4O9 phase after the first charge/discharge cycle, which further initiates the charge storage process via the conversion reactions.