Abstract: Potassium ion batteries (PIBs) present significant potential for large-scale energy storage applications due to their abundance and cost-effectiveness. However, the commercialization of PIBs is hindered by the limited availability of suitable carbon-based anode materials that combine high performance, cost efficiency, and scalability. Herein, coal-derived carbon anode material with outstanding potassium storage properties was synthesized using a microcrystalline hybridization strategy facilitated by starch. The highly cross-linked structure formed through molecular dehydration and polymerization during the pre-oxidation process can effectively suppress the rearrangement of carbon layers during subsequent carbonization. As a result, the obtained hybrid carbon material characterized by a large interlayer distance and locally short-ranged structures, achieves a reversible potassium storage capacity of 284.9 mAh g^-1 with excellent rate performance and long-term cycling stability with a capacity retention of 92.2 % after 500 cycles at 1 C. The underlying microcrystalline hybridization mechanism has been elucidated by in-situ FTIR analysis, and the K-storage process has also been intensively studied. This work offers a viable route for preparing coal-based carbon material with outstanding electrochemical K-storage capabilities, which is supposed to promote the development of cost-effective and sustainable carbonaceous materials for the practical application of PIBs.

Key words: Potassium ion battery, Carbon anode, Pre-oxidation, Starch, Lignite