In Situ Ions Induced Formation of K x F-Rich SEI Layers toward Ultrastable Life of Potassium-Ion Batteries.

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.