Stablizing the oxygen redox and crystal structure of O3-type layered oxides for sodium-ion batteries under Harsh conditions

Abstract

O3-NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) layered oxides have shown promise as cost-effective cathode materials for sodium-ion batteries (SIBs). However, under harsh operational conditions such as high-voltage cycling (>4.2 V), elevated temperature, and humid environments, the practical application of NFM cathode is hindered by significant performance degradation caused by irreversible oxygen oxidation, detrimental phase transitions, and moisture-induced surface degradation. To address these issues, we propose a one-step Gd-doping strategy to address these challenges synergistically. The unique electronic configuration of Gd³⁺ can effectively regulate charge distribution, enhance oxygen redox reversibility and suppress irreversible oxygen release. Simultaneously, its appropriate ionic radius helps to reduce interlayer spacing and mitigate phase transition strain to stabilize the layered structure. The optimized Gd-doped NFM cathode delivers a high capacity of 180.47 mAh/g at 0.1 C (1 C = 150 mA/g), outstanding rate capability (130.10 mAh/g at 5 C), and exceptional cycling stability (87.5% retention after 200 cycles at 5 C). More importantly, it demonstrates remarkable resilience under high-temperature and humid conditions, offering a practical design strategy for high-performance SIBs operable under realistic harsh environments.