In Situ Ions Induced Formation of K_xF‐Rich SEI Layers toward Ultrastable Life of Potassium‐Ion Batteries

Abstract Engineering F‐rich solid electrolyte interphase (SEI) layers is regarded as an effective strategy to enable the long‐term cycling stability of potassium‐ion batteries (KIBs). However, in the conventional KPF₆ carbonate electrolytes, it is challenging to form F‐containing SEI layers due to the inability of KPF₆ to decompose into K_xF. Herein, AlCl₃ is employed as a novel additive to change the chemical environment of the KPF₆ carbonate electrolyte. First, due to the large charge‐to‐radius ratio of Al³⁺, the Al‐containing groups in the electrolyte can easily capture F from PF₆⁻ and accelerate the formation of K_xF in SEI layer. In addition, AlCl₃ also reacts with trace H₂O or solvents in the electrolytes to form Al₂O₃, which can further act as a HF scavenger. Upon incorporating AlCl₃ into conventional KPF₆ carbonate electrolyte, the hard carbon (HC) anode exhibits an ultra‐long lifespan of 10000 cycles with a high coulombic efficiency of ≈100%. When coupled with perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA), the full cell exhibits a high capacity retention of 81% after 360 cycles‐significantly outperforming cells using conventional electrolytes. This research paves new avenues for advancing electrolyte engineering towards developing durable batteries tailored for large‐scale energy storage applications.