Pyrolysis fuel oil-derived hollow carbon nanocages as high-stability anode materials for potassium ion storage

Abstract

The use of graphite to make anode materials for potassium-ion batteries (KIBs) results in diminished electrochemical performance, largely due to significant interlayer expansion caused by potassation/depotassiation. To address this limitation, novel hollow carbon nanocages (HCNCs) are prepared from pyrolysis fuel oil (PFO), a cost-effective byproduct. The HCNCs heat-treated at 1500 °C has a graphitic structure with high porosities and numerous closed pores and exhibits a notable potassium-ion storage capacity of 307.2 mAh/g at a current density of 50 mA g−1. Moreover, structurally stable HCNCs withstand the substantial volume expansion associated with potassium-ion intercalation. The stability of the material is attributed to a hybrid adsorption/insertion mechanism, which results from synergistic interplay between the unique morphologies of the HCNCs and the developed carbon layers. This configuration delivers a specific capacity of 131.6 mAh/g and 98.9 % capacity retention over 1000 cycles at a high current density of 2000 mA g−1. Consequently, these proposed HCNCs present a significant advance in developing efficient carbon materials for KIBs, and addressing the critical challenges of graphite such as unstable cycling stability.