Hierarchically Porous P₂O₅-Modified Soft Carbon From Petroleum Pitch: Preparation and Lithium Storage Properties

Petroleum pitch, a soft-carbon precursor rich in aromatics, facilitates the formation of graphitic microdomains, thereby enhancing lithium-ion (Li⁺) diffusion and structural stability. In this work, a P₂O₅-assisted method was developed to simultaneously cross-link the molecular chains of pitch and introduce phosphorus dopants, yielding a carbon material with an expanded interlayer spacing (0.361 nm), increased structural disorder, and a hierarchical porous texture. The P₂O₅-induced cross-linking disrupted the layer ordering, increased the specific surface area and porosity, and created additional Li⁺ migration pathways. Moreover, phosphorus doping increased the interlayer spacing via enhanced interlayer repulsion, thereby accelerating Li⁺ transport. Consequently, the material delivered an initial charge capacity of 578 mA h g¹ and retained 94% of its capacity after 1000 cycles at a current density of 0.5 A g^-1. In situ Fourier transform infrared (FTIR) and wettability measurements revealed a rough, pore-rich surface that improved electrode-electrolyte wettability and facilitated Li⁺ desolvation, thereby contributing to the enhanced cycling stability. Overall, phosphorus doping significantly enhances the lithium storage performance of pitch-derived soft carbon and provides a viable route for the resource utilization of petroleum pitch.