Unveiling Microscopic Origin of Irreversible Capacity Fading in Prussian Blue Analogues for High-Performance Potassium-Ion Storage.

Abstract

Co₃[Co(CN)₆]₂ exhibits incomparable advantages over traditional inorganic anode materials of potassium-ion batteries. However, it often suffers from rapid irreversible capacity decay upon cycling, and the underlying mechanism still remains elusive because of the lack of an accurate understanding of microscopic behaviors. Herein, a high-entropy Prussian blue analogue (PBA) of hexyanocobaltate is synthesized to significantly improve the rate capability and cycling performances. It is revealed for the first time that the irreversible dissolution of transition metal species coordinated with nitrogen leads to remarkable capacity degradation of PBAs during cycling. The high-entropy strategy can not only improve the reaction kinetics of PBAs, but also significantly inhibit the dissolution of transition metals by strengthening the M─N bonds during cycling. Through high-entropy and carbon encapsulation, the resultant material exhibits outstanding potassium storage performances. This work could provide new insights into the capacity decay mechanism and rational design of high-performance PBA anodes for alkali-ion batteries.