Enhanced sodium storage performance of layered LiV3O8 cathodes via synergistic Zr4+ doping and ultrasonic treatment

Developing high-performance sodium-ion battery (SIB) cathodes is crucial for their practical deployment. Layered LiV₃O₈ (LVO) has emerged as a promising candidate due to the multivalence of vanadium, which facilitates multi-electron redox reactions and provides a high theoretical capacity. However, the electrochemical performance of LVO suffers from rapid capacity fading, multiple charge-discharge plateaus, and irreversible phase transitions during cycling. To mitigate these issues, we synthesized LiV_3-xZr_xO₈ with varying Zr⁴⁺ doping levels (x = 0.01, 0.02, 0.03). Among these, LiV_2.98Zr_0.02O₈ exhibited superior cycling stability and reversible sodium-ion intercalation. At a current density of 30 mA·g^-1 and within a voltage window of 1.8–4.0 V, it achieved an initial specific discharge capacity of 177.2 mAh·g^-1, retaining 97.1 mAh·g^-1 after 300 cycles, significantly outperforming the other doping levels. Further enhancements to LiV_2.98Zr_0.02O₈ were achieved through ultrasonic and thermal treatment, resulting in the sample designated LiV_2.98Zr_0.02O₈ Ut-300. This material demonstrated markedly improved sodium storage performance compared to its untreated form. Electrochemical impedance spectroscopy and galvanostatic intermittent titration technique analyses unveiled that LiV_2.98Zr_0.02O₈ Ut-300 possessed the lowest charge transfer resistance and the higher sodium ion diffusion coefficient, approximately 10^–12 cm²·s^-1. This study presents a strategy for high-performance layered metal oxide electrodes to significantly boost SIB energy storage.