Facile hydrothermal synthesis and electrochemical evaluation of nitrogen and phosphorous-co-doped reduced graphene oxide as an anode material for lithium-ion batteries

Nitrogen-phosphorus co-doped reduced graphene oxide (N-P-rGO) was synthesized as an anode material for lithium-ion batteries, through the hydrothermal method, using ammonium dihydrogen orthophosphate (NH 4 H 2 PO 4 ) as both the nitrogen and phosphorus source. FTIR and FESEM-EDS verified that nitrogen and phosphorus were incorporated into the graphene structure, resulting in wrinkled structure with heteroatoms distributed throughout the material. When evaluated as an anode material for LIB, the material exhibits significant improvements over as-received GO. N-P-rGO delivers about 650 mAhg −1 at 0.1Ag −1 , which is 62.5% higher than GO (400 mAhg −1 ). At current densities of 0.2, 0.5, 0.8, and 1.0 A g −1 , the material maintains reversible capacities of 580, 530, 496, and 460 mAhg −1 , respectively. Even at 5 A g −1 , N-P-rGO retains 133 mAhg −1 versus only 30 mAhg −1 for GO, and recovers to 595 mAhg −1 when tested again at 0.1 A g −1 . Cyclic stability tests at 5 Ag −1 reveal that N-P-rGO maintains 120–130 mAhg −1 for over 400 cycles, with over 95% capacity retention and nearly 100% Coulombic efficiency, substantially outperforming GO's 28–30 mAhg −1 with 80–85% retention after just 200 cycles. These results suggest that dual-doping with nitrogen and phosphorus is an effective way to enhance lithium-ion storage in graphene oxide, which increases charge storage capacity in LIBs.