Plasma–Electromagnetic Coupling-Driven Efficient Microwave Solid-Phase Synthesis of N, P-Doped Graphene with Synergistic Effects on Li–S Redox Kinetics

Microwave synthesis is emerging as an efficient low-complexity route for energy-storage materials. However, current studies on microwave-treated graphene and related carbon largely emphasize end-state structures or performance, leaving the underlying energy-conversion mechanisms poorly understood. Here, we develop a mechanism-guided solid-phase microwave synthesis strategy, enabled by electromagnetic field–plasma coupling, for the efficient minute-scale preparation of N/P-doped graphene and demonstrate its synergistic role in enhancing Li–S redox kinetics. A novel microwave heating mechanism is supported by multiphysics simulations, which reveal that plasma–electromagnetic coupling progressively elevates effective conductivity and enhances ohmic dissipation. Among them, charged-particle transport enables plasma penetration into the graphene dielectric, inducing significant intraparticle heating that is inaccessible to conventional thermal heating. Applying this microwave synthesis technique, a graphene microreactor accelerates precursor decomposition and promotes efficient N/P incorporation into the carbon lattice, enabling controllable and scalable construction of NG, PG, and NP-G in 4 min. A Li–S cell employing NP-G as an interlayer delivers an excellent initial specific capacity of 1438.2 mAh g–1 at 0.2 C and enhanced cycle stability. Density functional theory calculations further suggest that N/P doping drives charge-density redistribution and strengthens lithium polysulfide binding, with P enhancing electron donation and pyridinic-N sites providing strong adsorption, thereby rationalizing the observed catalytic synergy in the Li–S cell. This work links microwave energy dissipation with heteroatom doping and interfacial redox kinetics, providing a mechanistic basis for ultrafast synthesis and application of functional graphene.