A Novel Low-Strain Phosphate Cathode for High-Rate and Ultralong Cycle-Life Potassium-Ion Batteries.

Most potassium-ion battery (PIB) cathode materials have deficient structural stability because of the huge radius of potassium ion, leading to inferior cycling performance. In this work, we report the controllable synthesis of a novel low-strain phosphate material K 3 (VO)(HV 2 O 3 )(PO 4 ) 2 (HPO 4 ) (denoted KVP) nanorulers as an efficient cathode for PIBs. The as-synthesized KVP nanoruler cathode can exhibit an initial reversible capacity of 80.6 mAh g -1 under 20 mA g -1 , with a large average working potential of 4.11 V. It can also manifest an excellent rate property of 54.4 mAh g -1 under 5 A g -1 , with an exceedingly high capacity preservation of 92.1% over 2500 cycles. The outstanding potassium storage capability of KVP nanoruler cathode originates from low-strain K + uptake/removal mechanism, inherent semiconductor characteristic, and small K + migration energy barrier. The high energy density and prolonged cyclic stability of KVP nanorulers//polyaniline-intercalated layered titanate full battery verifies the superiority of KVP nanoruler cathode in PIBs. Our results show that this high-voltage low-strain phosphate material is a competitive cathode for PIBs and will draw more attention and investigations in the future.