Direct synthesis of P/O-enriched pitch-based carbon microspheres from a coordinated emulsification and pre-oxidation towards high-rate potassium-ion batteries

Abstract

Pitch-based soft carbons, with tunable microstructure and low cost, hold great potential as anodes for potassium-ion batteries (PIBs). However, the sluggish storage kinetics and unsatisfying cycle life hinder their practical applications. In addition, low softening point pitch has been seldom used to fabricate carbon microspheres due to its thermoplasticity. Herein, P and O enriched pitch-based carbon microspheres were directly synthesized via coordinated emulsification and pre-oxidation, and followed carbonized with NaH2PO2. This template-free method can avoid the coalescence of the coal tar pitch without extra post-stabilization. And NaH2PO2 acts as a P doping source and generates modest mesopores. The prepared P and O enriched carbon microspheres manifest a high P content of 4.0 at%, expanded interlayer distance of 0.401 nm, and abundant reversible K+ storage sites. As a result, it delivers considerable discharge capacity of 352 mAh g−1, impressive rate capacity of 114 mAh g−1 at 5 A g−1, and long lifespan of 181 mAh g−1 at 1 A g−1 after 1000 cycles. The present work develops a new avenue for heteroatoms doped carbon microspheres to innovative potassium storage and beyond.