Mg–B–O Coated P2-Type Hexagonal Na_0.5Mn_0.95Ni_0.05O₂ as a High-Performance Cathode for Sodium-Ion Batteries

P2-type Na 0.5 Mn 0.95 Ni 0.05 O 2 as the cathode for sodium-ion batteries, has a relatively high theoretical specific capacity, but its unstable crystal structure and undesirable phase transitions lead to rapid capacity decay. In this work, Mg–B–O coated Na 0.5 Mn 0.95 Ni 0.05 O 2 microspheres have been synthesized via a liquid-phase method based on solvothermal synthesized Na 0.5 Mn 0.95 Ni 0.05 O 2 . The Mg–B–O coating layer significantly improves the electrochemical performance, including specific capacity, rate capability, and cycle stability. Within the voltage window of 2.0–4.0 V, Mg–B–O coated Na 0.5 Mn 0.95 Ni 0.05 O 2 could exhibit an initial capacity of 93.2 mAh g –1 at a current density of 500 mA g –1, and maintains a capacity of 74.6 mAh g –1 after 500 cycles, with a capacity retention rate of 80.0%. The Mg–B–O coating effectively inhibits the formation of Na 2 CO 3 on the surface, enhancing air stability, reducing the Jahn–Teller effect induced by Mn 3+, as well as ensuring fast Na + diffusion kinetics. This work provides a new strategy for designing P2-type layered sodium-ion batteries with both high specific capacity and cycling stability.