Dissolution of cathode–electrolyte interphase deposited on LiNi0.5Mn1.5O4 for lithium-ion batteries

Adopting high-voltage positive electrodes is essential for realizing advanced lithium-ion batteries with high energy and power density. However, the operating potentials of electrodes are beyond the electrochemical stability window of commercial electrolytes, leading to a low coulombic efficiency and poor cycle life. Although the decomposition products of an electrolyte form a cathode–electrolyte interphase (CEI), which helps passivate the electrode surface and suppress further decomposition of the electrolyte in subsequent cycles, the CEI is associated with passivation failure, the mechanisms of which have rarely been investigated. This work demonstrates the local dissolution of CEI and the detrimental effects of dissolution on the electrochemical performance of a high-voltage spinel electrode. The corrosive acidic species, namely HF, is generated during electrolyte oxidation and damages the CEI by leaching inorganic components such as LiF and LixPOyFz. However, in the presence of Al2O3, which is an HF scavenger, the CEI is maintained relatively stable, and the coulombic efficiency is improved significantly. The results highlight the HF effect on the partial dissolution of the CEI and the additional role of Al2O3 in assisting CEI deposition.