Manipulating Phase Stability and Kinetics in Prussian Blue Cathode via Entropy Engineering and <i>d</i><sup>10</sup> Cation Incorporation for Potassium-Ion Batteries.

Huang, Honglin; Qiao, Shuangyan; Lv, Benhui; Liu, Hua Kun; Dou, Shi Xue; Chong, Shaokun · Nano Lett · 2025

basic_science · Level V

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Abstract

Phase transition and [Fe(CN)<sub>6</sub>]<sup>4-</sup> defects seriously limit electrochemical performance of Prussian blue analogue (PBA) cathodes for potassium-ion batteries (PIBs). Herein, entropy engineering and d<sup>10</sup> cation incorporation are utilized to construct a medium-entropy PBA, K<sub>1.23</sub>Fe<sub>0.42</sub>Mn<sub>0.45</sub>Sn<sub>0.13</sub>[Fe(CN)<sub>6</sub>]<sub>0.94</sub>·1.35H<sub>2</sub>O (KFMSHCF), as the cathode material for PIBs. Entropy-induced cation disorder markedly suppresses anion vacancies, while the entropy stabilization effect and Sn<sup>2+</sup> with a d<sup>10</sup> configuration stabilize local coordination environments. High configurational entropy boosts KFMSHCF to exhibit reduced band gap and low K-ion diffusion barrier, thereby ensuring excellent electrochemical kinetic. KFMSHCF undergoes a zero-strain solid-solution mechanism using Fe, Mn and Sn ions as redox centers for charge compensation. Therefore, KFMSHCF delivers a high initial energy density of 364.2 Wh·kg<sup>-1</sup>, remarkable cycling stability with a capacity retention of 82.1% after 100 cycles and long lifespan over 300 cycles, and significantly enhanced rate capability. The fabricated high-energy-density K-ion full batteries achieve ultralong lifespan over 2500 cycles with an ultralow capacity-decay-rate of 0.017% per cycle.