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

Abstract 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.