Constructing ultrastable electrode/electrolyte interface for rapid potassium ion storage capability via salt chemistry and interfacial engineering

Conversion/alloying anode materials exhibiting high K storage capacities suffer from large volume variations and unstable electrode/electrolyte interfaces upon cycling. Herein, taking SnS/reduced graphene oxide (SnS/rGO) anodes as an example, the electrochemical performance of SnS/rGO could significantly be improved via employing potassium bis(fluorosulfonyl)imide (KFSI) salt in electrolytes and ultrathin TiO₂ coating. KF-rich inorganic layer was demonstrated to help form robust SEI layer, which could suppress the side reactions to increase the Coulombic efficiency. The formed potassiated K_xTiO₂ coating layer was constructed to boost charge transfer capability and K-ion diffusion kinetics. The as-prepared SnS/rGO@TiO₂-20 electrode in KFSI electrolyte delivers the high CE of 99.1% and 424 mAh·g⁻¹ after 200 cycles with an ultrahigh capacity retention of 98.5%.