Stabilization of P2-type cathode at 4.5 V by “La pillar” in Na layer with a La–O orbital hybridization for long-life and high-energy-density Na-ion batteries

Abstract

P2-type layered oxide cathodes suffer from poor capacity retention and detrimental phase transitions at high voltage due to the presence of Na vacancies. During deep desodiation, irreversible lattice oxygen release increases capacity but also accelerates lattice collapse. In this work, to address the capacity limitations of the P2-type layered oxide cathode and leverage its structural stability, we develop a high-voltage P2-type layered oxide cathode, Na0.84La0.01Li0.12Ni0.22Mn0.66O2 (P2-NLLNMO). The La-doped material exhibits less volume variation (1.8%) and more stable crystal structure over a wide voltage window of 2.0–4.5 V. P2-NLLNMO yields a high capacity of 136.6 mAh g–1 and excellent cycling stability (89.2% retention after 200 cycles at 0.5 C) with a cutoff voltage 4.5 V. In addition, we reveal that La–O orbital hybridization is important for the enhanced performance when La atoms are doped in Na layers of P2-NLLNMO. This discovery provides valuable insights and guidance for the design of P2-type cathodes in high-energy-density sodium-ion batteries.

Keywords

• Na-ion battery
• P2 type
• Cathode material
• La doping
• High voltage