Nb - doping induces crystallization of coprecipitation particles to achieve high performance sodium-ion batteries cathode materials

Sodium-ion batteries (SIBs) are considered as one of the most competitive candidates for energy storage systems . While O3-type NaNi 0.5 Mn 0.5 O 2 cathode materials offer high theoretical capacity and operating voltage, their practical application is hindered by irreversible phase transitions during Na + extraction/insertion that degrade structural stability and reaction kinetics. This study synthesizes Nb-doped O3-Na[Ni 0.5 Mn 0.5 ] 1- x Nb x O 2 ( x = 0,0.01,0.02,0.03) through ball milling assisted coprecipitation . Nb doping enhances lattice stability through two mechanisms: on one hand promoting optimization of coprecipitated particle crystallization , and on the other hand effectively suppressing manganese activity through the formation of mixed cation-oxygen bonds. Na[Ni 0.5 Mn 0.5 ] 0.99 Nb 0.01 O 2 exhibits 108.7 mAh g –1 capacity at 0.5C with 77.4 % retention after 200 cycles, demonstrating enhanced cycling stability compared to the undoped material. When paired with hard carbon in full cell, the system achieves >190 Wh kg –1 energy density . Theoretical calculations also elucidate the mechanism by which Nb doping affects the hybridization of Ni-O bonds, stabilizes the structure of the material, and exhibits enhancement in electrochemical properties . This study provides an effective strategy for suppressing the phase transition and advancing the study of the doping mechanism in sodium-ion batteries.