In-situ ions Induced Formation of K x F-rich SEI Layers towards Ultra-Stable life of Potassium Ion Batteries.

Engineering F-rich 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. Firstly, 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 an HF scavenger. The "self-induced formation" of F-rich SEI layers (K x F and AlF 3 ) and "self-elimination" of unexpected species (H 2 O and HF) guarantee the excellent long-term cycling stability of KIBs. 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 PTCDA, the full cell exhibits a high capacity retention of 81% after 360 cycles-significantly outperforming cells using conventional electrolytes. Moreover, PTCDA||HC pouch cell using AlCl 3 added KPF 6 electrolyte deliver a reversible capacity of 93 mAh g -1 with capacity retention of 86% after 80 cycles. This research paves new avenues for advancing electrolyte engineering towards developing durable batteries tailored for large-scale energy storage applications. This article is protected by copyright. All rights reserved.