Succinonitrile-driven cathode-electrolyte interface modulation for stable and high-rate Prussian white cathode in potassium-ion batteries

Abstract

Iron-based Prussian white (PW) materials have attracted considerable attention as promising cathodes for potassium-ion batteries (PIBs) due to their high capacity, easy preparation, and economic merits. However, the intrinsic iron dissolution and uncontrollable cathode-electrolyte interface (CEI) formation in conventional organic electrolytes severely hinder their long-term cycling stability. Herein, we employ succinonitrile (SN), a bifunctional electrolyte additive, to suppress the iron dissolution and promote thin, uniform, and stable CEI formation of the PW cathode, thus improving its structural stability. Benefited from the coordination between the cyano groups in SN and iron atoms, this molecule can preferentially adsorb on the surface of PW to mitigate iron dissolution. SN also facilitates the decomposition of anions in potassium salt rather than organic solvents in electrolyte due to the attractive reaction between SN and anions.

Consequently, the PW cathode with SN additive provides better electrochemical reversibility, showing capacity retention of 93.6% after 3000 cycles at 5C. In comparison, without SN, the capacity retention is only 87.4% after 1000 cycles under the same conditions. Moreover, the full cells of PW matched with commercial graphite (Gr) achieve stable cycling for 3500 cycles at a high rate of 20C, with an exceptional capacity decay of only 0.005% per cycle, surpassing the majority of recently reported results in literature.