In‐situ ions Induced Formation of KxF‐rich SEI Layers towards Ultra‐Stable 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 KPF 6 carbonate electrolytes, it is challenging to form F‐containing SEI layers due to the inability of KPF 6 to decompose into K x F. Herein, AlCl 3 is employed as a novel additive to change the chemical environment of the KPF 6 carbonate electrolyte. First, due to the large charge‐to‐radius ratio of Al 3+ , the Al‐containing groups in the electrolyte can easily capture F from PF 6 − and accelerate the formation of K x F in SEI layer. In addition, AlCl 3 also reacts with trace H 2 O or solvents in the electrolytes to form Al 2 O 3 , which can further act as a HF scavenger. Upon incorporating AlCl 3 into conventional KPF 6 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.