Investigation of N and S Co-doped Porous Carbon for Sodium-Ion Battery, Synthesized by Using Ammonium Sulphate for Simultaneous Activation and Heteroatom Doping

In the present work, nitrogen and sulphur co-doped porous carbon materials are obtained by using ammonium sulphate as a template. The multi-role of ammonium sulphate as an activating agent and as nitrogen and sulphur dopant is investigated. The resulting porous carbon material achieved high doping level (9.3 at% for nitrogen and 3.5 at% for sulphur) and increased interlayer spacing from 0.35 to 0.38 nm which improves the storage kinetics of Na+-ions inside the carbon lattice. The synthesized materials, when used as negative electrodes for sodium-ion battery, provide promising electrochemical performance with a reversible storage capacity of 439 mAh g−1 at a current density of 10 mA g−1. The storage capacity of ∼100 mAh g−1 with capacity retention of 62% retained after 200 cycles at 220 mA g−1. This work presents the multifunctional roles of ammonium sulphate in achieving the nitrogen and sulphur co-doped porous carbon materials.