A novel phosphorus-doped Ge3N4 powder as high-capacity anode materials for lithium-ion batteries

Abstract

In this paper, the effect of doping with phosphorus atoms (P atoms) on the electrochemical performance of Ge₃N₄ as anode materials for lithium-ion batteries (LIBs) is investigated. P-doped Ge₃N₄ (P-Ge₃N₄) is synthesized by an in-situ nitridation and phosphorization method utilizing urea and NaH₂PO₂·H₂O as nitrogen and phosphorus sources. The P-Ge₃N₄ material is systematically characterized and the effect of phosphorus doping on the structure of Ge₃N₄ is studied. The electrochemical performance of the P-Ge₃N₄ anode materials in LIBs is also tested. The results indicate that the presence of P atoms enhances the overall electronic conductivity. The first discharge capacity of P-Ge₃N₄ material is 1548.53 mAh g⁻¹, which is much higher than that of pure Ge₃N₄ (850.26 mAh g⁻¹), and P-Ge₃N₄ still maintains a higher reversible discharge capacity than Ge₃N₄ after 100 cycles. P-Ge₃N₄ exhibits superior rate capability compared to Ge₃N₄, maintaining higher discharge capacities at various current densities. Based on density functional theory (DFT) simulation and calculation, it is found that the band gap width decreased from 1.76 eV to 0.27 eV, indicating that P doping improves the conductivity of Ge₃N₄. This study establishes an effective phosphorus atom doping strategy by combining experimental characterization and theoretical calculations, showing how the introduction of P changes the crystal structure, electronic properties and electrochemicl performance of Ge₃N₄. It provides a new theoretical and experimental basis for the design and optimization of high-performance anode materials for LIBs.