Harnessing Plasma‐Assisted Doping Engineering to Stabilize Metallic Phase MoSe2 for Fast and Durable Sodium‐Ion Storage

Metallic-phase selenide molybdenum (1T-MoSe₂ ) has become a rising star for sodium storage in comparison with its semiconductor phase (2H-MoSe₂ ) owing to the intrinsic metallic electronic conductivity and unimpeded Na⁺ diffusion structure. However, the thermodynamically unstable nature of 1T phase renders it an unprecedented challenge to realize its phase control and stabilization. Herein, a plasma-assisted P-doping-triggered phase-transition engineering is proposed to synthesize stabilized P-doped 1T phase MoSe₂ nanoflower composites (P-1T-MoSe₂ NFs). Mechanism analysis reveals significantly decreased phase-transition energy barriers of the plasma-induced Se-vacancy-rich MoSe₂ from 2H to 1T owing to its low crystallinity and reduced structure stability. The vacancy-rich structure promotes highly concentrated P doping, which manipulates the electronic structure of the MoSe₂ and urges its phase transition, acquiring a high transition efficiency of 91% accompanied with ultrahigh phase stability. As a result, the P-1T-MoSe₂ NFs deliver an exceptional high reversible capacity of 510.8 mAh g^-1 at 50 mA g^-1 with no capacity fading over 1000 cycles at 5000 mA g^-1 for sodium storage. The underlying mechanism of this phase-transition engineering verified by profound analysis provides informative guide for designing advanced materials for next-generation energy-storage systems.