Mg-B-O Coated P2-Type Hexagonal Na 0.5 Mn 0.95 Ni 0.05 O 2 as a High-Performance Cathode for Sodium-Ion Batteries

P2-type Na Mn Ni O 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 Mn Ni O microspheres have been synthesized via a liquid-phase method based on solvothermal synthesized Na Mn Ni O . 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 Mn Ni O could exhibit an initial capacity of 93.2 mAh g at a current density of 500 mA g , and maintains a capacity of 74.6 mAh g after 500 cycles, with a capacity retention rate of 80.0%. The Mg-B-O coating effectively inhibits the formation of Na CO on the surface, enhancing air stability, reducing the Jahn-Teller effect induced by Mn , 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.