Tailoring the electronic structure of O3-type layered oxide cathodes to achieve long-cycle life and high-rate performance sodium-ion batteries

Abstract

Despite its great potential for practical application in sodium-ion batteries (SIBs), the O3-type layered oxide cathode is still hindered by rapid capacity decay and poor cycle life, which is primarily due to irreversible phase transitions caused by the Jahn–Teller effect of Mn³⁺ ions. Here, we design an O3-Na_0.98Li_0.03Co_0.05Ni_0.22Fe_0.2Mn_0.5O₂ (LCNFM) oxide cathode to effectively suppress the irreversible phase transition by tailoring its electronic structure. This approach activates more transition metal ions (Ni²⁺ and Fe³⁺) to participate in the redox reactions above 2.5 V, and suppresses the redox reactivity of Mn^3+/4+ below 2.5 V. Additionally, cobalt ions, with their excellent electronic conductivity, significantly improve the dynamic performance. Importantly, the fundamental mechanism is fully understood through systematic in situ/ex situ characterization techniques and density functional theory computations. Consequently, the as-prepared LCNFM electrode, with high structural stability, exhibits excellent cycling performance (87.2% capacity retention after 1000 cycles at 5C within 2.0–4.0 V) and high rate capacity (112.1 mA h g⁻¹ at 0.1C compared to 100 mA h g⁻¹ at 1C). This work provides a new perspective for designing high-performance O3-type layered cathodes and offers a practical strategy to boost the commercial application for SIBs.