Sb-Doped O3-NaNi_0.3Fe_0.2Mn_0.5O₂ Cathode with Improved Cyclic Stability for Sodium-Ion Batteries

As a leading sodium-ion battery cathode material, O3-type layered oxides combine excellent theoretical specific capacity and cost-effectiveness, offering potential solutions for the large-scale energy storage industry. However, they still struggle with significant capacity degradation and inferior battery performance due to the narrow Na+ diffusion channels and complex phase. In this paper, we introduce Sb ions into the NaNi0.3Fe0.2Mn0.5O2 cathode material to improve its electrochemical performance. Our findings demonstrate that doping Sb results in an expansion of the Na layer spacing and cell volume, contributing to faster diffusion of Na+. Furthermore, the Na+/vacancy ordering and undesirable phase transition under high pressure are inhibited in the synthesized Na(Ni0.3Fe0.2Mn0.5)0.98Sb0.02O2 cathode material, which obtains a more boosting structure and advanced electrochemical performance. Within the voltage range of 2.0–4.2 V, the cathode material possesses an initial discharge specific capacity of 127.71 mAh g–1 and maintains a capacity retention of 82.34% (64.33% before doping) after 100 cycles. Moreover, at a 10 C current density, a high discharge specific capacity of 90.26 mAh g–1 is observed in the doped material. These results contribute essential insights for the design and advancement of cathode materials for sodium-ion batteries with outstanding properties.