In situ exsolution of Ag from AgBiS2 nanocrystal anode boosting high-performance potassium-ion batteries

Abstract

The irreversible formation of a solid electrolyte interface (SEI) film on semimetal/semiconductors impedes the electrochemical migration of K⁺ in potassium-ion batteries due to the inevitable volume expansion of the anode materials. Herein, we report the in situ exsolution of Ag in metastable nanostructured AgBiS₂ to spontaneously assist cycling for K⁺ intercalation. The in situ XRD and ex situ HRTEM techniques revealed unique phase transitions during the uptake of K⁺ on account of the mixed ion storage mechanism. During the initial reduction process, AgBiS₂ underwent K⁺/AgBiS₂ displacement, K⁺/BiS₂ conversion, and K⁺/Bi alloying reaction. The exsolution of Ag was electrochemically reduced in the process of K⁺ insertion and remained as an intermediate charge transmitter to sustain a high reversible capacity of 420 mA h g⁻¹ at 0.5 A g⁻¹, superior rate performance of 210 mA h g⁻¹ at 5 A g⁻¹ and long-term (over 300) cycle stability. This work presents a strategy to resolve the issues of single-element anodes in metal-ion batteries.