Skip to main content
Open Access Publications from the University of California

A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F

  • Author(s): Kim, H
  • Seo, DH
  • Bianchini, M
  • Clément, RJ
  • Kim, H
  • Kim, JC
  • Tian, Y
  • Shi, T
  • Yoon, WS
  • Ceder, G
  • et al.

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The exploration of high-energy-density cathode materials is vital to the practical use of K-ion batteries. Layered K-metal oxides have too high a voltage slope due to their large K+–K+ interaction, resulting in low specific capacity and average voltage. In contrast, the 3D arrangement of K+, with polyanions separating them, reduces the strength of the effective K+-K+ repulsion, which in turn increases specific capacity and voltage. Here, stoichiometric KVPO4F for use as a high-energy-density K-ion cathode is developed. The KVPO4F cathode delivers a reversible capacity of ≈105 mAh g−1 with an average voltage of ≈4.3 V (vs K/K+), resulting in a gravimetric energy density of ≈450 Wh kg−1. During electrochemical cycling, the KxVPO4F cathode goes through various intermediate phases at x = 0.75, 0.625, and 0.5 upon K extraction and reinsertion, as determined by ex situ X-ray diffraction characterization and ab initio calculations. This work further explains the role of oxygen substitution in KVPO4+xF1−x: the oxygenation of KVPO4F leads to an anion-disordered structure which prevents the formation of K+/vacancy orderings without electrochemical plateaus and hence to a smoother voltage profile.

Many UC-authored scholarly publications are freely available on this site because of the UC Academic Senate's Open Access Policy. Let us know how this access is important for you.

Main Content
Current View