In situ exsolution of Ag from AgBiS₂nanocrystal anode boosting high-performance potassium-ion batteries

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.