Stable LCO Cathodes Charged at 4.6 V for High Energy Secondary Li‐ion Batteries by One‐Pot Dual Metal Fluorides Coating

Abstract LiCoO 2 (LCO) has been the cathode material of choice for three decades for durable, lightweight Li‐ion storage systems. Being charged up to 4.2 V versus Li/Li + , LCO provides excellent cycling stability with a specific capacity of ≈140 mAh g −1 . Raising the cut‐off voltage to 4.6 V improves capacity by up to 60% however, it leads to rapid degradation of the cathode structure. Here, a one‐pot dual coating of MgF 2 and AlF 3 with fluorinated electrolyte additives achieves 190 mAh g −1 at a 0.5 C rate after 400 cycles with a capacity retention of 93%. Various analytical tools are used to follow the structural and morphological changes during cycling. Synergistically, ion transport is improved, and detrimental interfacial side reactions with the electrolyte solutions are fully mitigated. Structural stability is thus improved by using this coating, with only a little loss of the active material. This work provides a brief guideline for designing dual metal‐ion‐based surface coatings in various electrolytes to develop high‐voltage cathode systems for Li and maybe also Na batteries.