Multi-Redox (V 5+ /V 4+ /V 3+ /V 2+ ) Driven Asymmetric Sodium (De)intercalation Reactions in NASICON-Na 3 VIn(PO 4 ) 3 Cathode

NASICON-Na 3 V 2−x M x (PO 4 ) 3 (M = Al 3+ , Cr 3+ , Fe 3+ & Ga 3+ ) cathodes are attractive for sodium-ion battery application due to their high voltage multi-redox (V 5+ /V 4+ /V 3+ ) couples and faster sodium-ion diffusivity. However, they suffer from rapid capacity decay due to irreversible structural changes occurring at high voltages. Herein, we present the structural and electrochemical sodium (de)intercalation properties of NASICON-Na 3 VIn(PO 4 ) 3 (NVIP) cathode. Although, this In 3+ -substituted cathode also undergoes similar high voltage structural degradation, but its structure is rejuvenated through the following low voltage deep-sodiation process, resulting in reversible capacities of ∼145 mA h g −1 (i.e., equivalent to ∼2.82 moles of Na per vanadium). Our combined electrochemical, in-operando X-ray diffraction and exsitu X-ray absorption spectroscopy analyses reveal asymmetric sodium (de)intercalation pathways of the NVIP cathode in the window of 4.2–1.2 V vs Na + /Na 0 that is driven by multi-redox (V 5+ /V 4+ /V 3+ /V 2+ ) couples.