Inhibition of Surface-Originated Degradations in Lithium-Rich Layered Cathode via a Pre-Constructed Carbon/Fluorine-Rich Artificial CEI Layer

In the ongoing pursuit of energy-dense lithium-ion batteries (LIBs), Li-rich layered oxide (LLO) cathodes provide an attractive path forward with extraordinary capacity delivery and low raw material cost. However, the surface-originated degradations and local structure rearrangement incur severe capacity and voltage fading, which fundamentally impedes the practical deployment of LLOs. Here, we report a pre-constructed multifunctional carbon/fluorine-rich artificial cathode electrolyte interface (CEI) layer via a facile thermal treatment. This surface integrated layer, with high-voltage tolerance and amorphous features, is designed to mitigate surface-originated parasitic reactions and phase transformations induced by electrochemistry. Multiscale characterizations reveal that the artificial CEI layer exhibits excellent interfacial compatibility with both the LLO cathode and the electrolyte system, ensuring highly reversible anionic redox and low activation barrier for Li + transport. Profiting from this architecture, remarkable cycling stability is achieved including 90.6% retention after 300 cycles in half cell, along with high energy efficiency and markedly alleviated voltage fading. More importantly, the artificial CEI layer demonstrates a distinct depolarization effect, which almost completely prevents the rise in charging voltage upon cycling. This work provides valuable insights into surficial/interfacial modulations and broadens research directions for designing high-voltage cathodes with more durable interphases for next-generation batteries.