Precise Anchoring of Pre-oxidation Sites via Zn-O-C Chemical Bonding for Enhanced Sodium Storage in Pitch-Derived Hard Carbon

Abstract

Against the backdrop of global carbon neutrality, sodium-ion batteries (SIBs) have emerged as a pivotal technology for large-scale energy storage, benefiting from the abundance and low cost of sodium. However, the development of low-cost, high-performance anode materials remains a critical bottleneck. Pitch, a byproduct of petroleum refining, is an ideal precursor for hard carbon anodes due to its high availability and carbon yield. Nevertheless, low-softening-point pitch tends to undergo severe melting and agglomeration during conventional pre-oxidation, leading to inhomogeneous oxidation and excessive ordered stacking of carbon layers, which significantly restricts its sodium storage performance. Herein, we develop a green and energy-efficient Zn–O–C chemical crosslinking-assisted pre-oxidation strategy. By incorporating low-toxicity zinc acetate via liquid-phase blending at the molecular level, Zn–O–C coordination bonds are formed, which precisely anchor the pre-oxidation sites and fundamentally suppress the melting of pitch. The resultant hard carbon features a highly disordered structure, expanded interlayer spacing, and A large number of ultramicropores. It achieves a reversible capacity of 322 mAh g-1 at 30 mA g-1, along with a significantly enhanced low-voltage plateau capacity, outstanding rate capability, and excellent cycling stability. Combined in situ characterizations and density functional theory calculations reveal an “adsorption-intercalation-pore filling” sodium storage mechanism. Notably, this strategy incurs no additional energy consumption compared to conventional processes while enabling high-value valorization of an industrial byproduct, offering a sustainable route for the preparation of hard carbon anodes.