A Low‐Strain Potassium‐Rich Prussian Blue Analogue Cathode for High Power Potassium‐Ion Batteries

Most of the cathode materials for potassium ion batteries (PIBs) suffer from poor structural stability due to the large ionic radius of K+, resulting in poor cycling stability. Here we report a low‐strain potassium‐rich K1.84Ni[Fe(CN)6]0.88⋅0.49 H2O (KNiHCF) as a cathode material for PIBs. The as‐prepared KNiHCF cathode can deliver reversible discharge capacity of 62.8 mAh g−1 at 100 mA g−1, with a high discharge voltage of 3.82 V. It can also achieve a superior rate performance of 45.8 mAh g−1 at 5000 mA g−1, with a capacity retention of 88.6 % after 100 cycles. The superior performance of KNiHCF cathode results from low‐strain de‐/intercalation mechanism, intrinsic semiconductor property and low potassium diffusion energy barrier. The high power density and long‐term stability of KNiHCF//graphite full cell confirmed the feasibility of K‐rich KNiHCF cathode in PIBs. This work provides guidance to develop Prussian blue analogues as cathode materials for PIBs. A low‐strain potassium‐rich K1.84Ni[Fe(CN)6]0.88⋅0.49 H2O (KNiHCF) was prepared by a facile co‐precipitation method. The KNiHCF//graphite full cell exhibits high rate performance, superior cycling stability, and high power density. This work would offer an insight into design of the low‐strain cathode materials for PIBs.