Electrolyte solvent composition regulating endows CoSe2 hollow nanocage anode with stable potassium ion storage

Abstract

Metal selenides are ideal anode materials for potassium-ion batteries (PIBs) due to their significant merits of favorable conductivity and ion transport property. However, the inevitable volume changes of metal selenides electrode during potassiation/depotassiation processes result in the fracture and reconstruction of the solid electrolyte interphase (SEI) layer, causing capacity decay and significantly limiting their practical applications. Reasonable morphology control accompanied by uniform and rigid SEI layer formation are key factors in improving the electrochemical cycling stability of metal selenides. In this paper, nano-hollow CoSe2 (CoSe2@CNC) anode materials are prepared using ZIF-67 as the precursor. The differences of electrochemical performances for CoSe2@CNC anode material in ester-based and ether-based electrolytes have been investigated in detail. Results demonstrate that the SEI layer formed in the ester-based electrolyte is loose and thick, leading to electrode pulverization and material detachment after several cycles, resulting in rapid degradation of cycle performance. In contrast, a thin and inorganic-rich SEI layer containing more inorganic components is formed in the ether-based electrolyte, effectively protecting the electrode from damage, facilitating electronic transfer at the electrode electrolyte interphase, and optimizing potassium ions storage performance.