KVOPO4 as Cathode for Battery

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we prepared a novel KVOPO4 cathode that delivers a very promising multielectron charge storage in a sodium ion battery. The V3+ ↔ V5+ redox couple in the vanadyl phosphates was for the first time activated, intercalating 1.66 sodium ions per formula unit intercalation reaction. Structural characterization including X‐ray absorption spectroscopy, ex situ XRD revealed the highly reversible evolution of the polyhedron framework with a small volume change upon multiple sodium intercalation/extraction. The multielectron reaction and the small volume change enabled the discharge capacity of over 200 mAh g−1 for this phosphate‐based compound with excellent capacity retention upon extended cycling. This capacity combined with an average voltage of 2.56 V delivers an energy density of over 600 Wh kg−1, which exceeds that of the current sodium ion battery intercalation cathodes. Moreover, both rate capabilities and DFT calculations indicate that the sodium diffusion kinetics within the unique wide‐open vanadyl phosphate framework are quite facile, which could yield a high power cathode.