Liquid phase oxidation enables stable soft carbon anodes for potassium-ion batteries

Soft carbon has been recognized as a promising anode material for potassium-ion batteries (PIBs), due to low cost, high conductivity and low voltage platform. However, their practical application is hampered by slow storage kinetics and unsatisfactory cycle life. In this work, pitch-derived needle coke, a typical soft carbon, was incorporated with oxygenated functional groups through liquid phase oxidation by using H 2 O 2 oxidant. When used as anode materials for PIBs, the oxidized needle coke delivers a high reversible capacity of 322.7 mAh g −1 , significantly superior to that of the needle coke (237.9 mAh g −1 ). The enhanced electrochemical performance can be attributed to the abundant oxygenated functional groups and resultant defects on the surface of oxidized needle coke, which not only serve as extra active sites for potassium storage, but also provide sufficient pathways for K + migration across the adjacent carbon layers. Moreover, the expanded interlayer spacing derived from H 2 O 2 oxidation facilitates rapid K + intercalation and deintercalation. This work offers an effective modification strategy for the fabrication of high-performance pitch-based soft carbon anodes for PIBs. Graphical Abstract