Nano-Impact Electrochemistry Reveals Kinetics Information of Metal-Ion Battery Materials with Multiple Redox Centers.

Prussian blue (PB) has emerged as a promising cathode material in aqueous batteries. It possesses two distinct redox centers, and the potassium ions (K ) are unevenly distributed throughout the compound, adding complexity to the interpretation of the K insertion/de-insertion kinetic mechanism. Traditional ensemble-averaged measurements are limited in uncovering the precise kinetic information of the PB particles, as the results are influenced by the construction of the porous composite electrode and the redox behavior from different particles. In this study, the electrochemical processes of individual PB particles were investigated using nano-impact electrochemistry. By varying the potentials, different types of transient current signals were obtained that revealed the kinetic mechanism of each oxidation/reduction reaction in combination with theoretical simulation. Additionally, a partially contradictory conclusion between single-particle analysis and the ensemble-averaged measurement was discussed. These findings contribute to a better understanding of the electrochemical processes of cathode materials with multiple redox centers, which facilitates the development of effective strategies to optimize these materials.