Phosphorus‐Doped rGO/SiO x Composite Anodes With Enhanced Li + Diffusion and SEI Stability for High‐Performance Lithium‐Ion Batteries

ABSTRACT Silicon oxide (SiO x ) is a promising anode for lithium‐ion batteries due to its high theoretical capacity, but its poor conductivity and severe volume expansion limit cyclic stability. We investigate phosphorus (P) doping of reduced graphene oxide and its composite with SiO x (P‐rGO/SiO x ) as an effective strategy to enhance the overall electrochemical performance of SiO x . Preliminary analyses confirmed the formation of SiO x nanoparticles with distinct lattice planes and successful incorporation of P into the rGO matrix. P‐doping generated C─P and P─O bonds, expanded the rGO interlayer spacing, and created additional Li + diffusion pathways. Electrochemical studies revealed that 2% P‐doped rGO/SiO x exhibited the highest first‐cycle lithiation/delithiation capacities of 1001.2/563.0 mAh g − 1 with an initial coulombic efficiency of 56.2%. After 100 cycles, the 2% P‐doped composite maintained a capacity of 328.4 mAh g − 1 with 80.3% retention, outperforming undoped and higher‐doped samples. SEM analysis after 100 cycles revealed that the 2% P‐doped rGO/SiO x preserved its morphology, whereas 4% and 6% P‐doping caused severe cracking and delamination. The enhanced lithium‐ion storage, stability, and reversibility are attributed to an optimal P─O bonding ratio that increases active sites, promotes uniform SEI formation, and minimizes Li + diffusion resistance.