In‐situ ions Induced Formation of K_xF‐rich SEI Layers towards Ultra‐Stable life of Potassium Ion Batteries

AbstractEngineering 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 KPF6 carbonate electrolytes, it is challenging to form F‐containing SEI layers due to the inability of KPF6 to decompose into KxF. Herein, AlCl3 is employed as a novel additive to change the chemical environment of the KPF6 carbonate electrolyte. Firstly, 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 KxF in SEI layer. In addition, AlCl3 also reacts with trace H2O or solvents in the electrolytes to form Al2O3, which can further act as an HF scavenger. The “self‐induced formation” of F‐rich SEI layers (KxF and AlF3) and “self‐elimination” of unexpected species (H2O and HF) guarantee the excellent long‐term cycling stability of KIBs. 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 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 AlCl3 added KPF6 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