Understanding the active formation of a cathode–electrolyte interphase (CEI) layer with energy level band bending for lithium-ion batteries

Abstract

The cathode-electrolyte interphase (CEI) formation between the cathode and the electrolyte is a critical factor that determines the stability of lithium-ion batteries (LiBs). The CEI layer consists of various by-products...

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“…This phenomenon could be ascribed to the formation of a cathode-electrolyte interface (CEI), resulting in smaller ohmic impedance and accelerated electron transfer rate. 46,47 After the next 15 cycles, the value of R ct was 37.4 Ω. The variation of R ct tends to level off, indicating that the polarization generated by the electrodes during the cycle was quite small, which was consistent with the stable cycling performance of ABPZ.…”

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“…[47][48][49] It is also necessary to mention here that a phenomenon that has not been taken into consideration is band bending. 50 Band bending is a significant phenomenon that occurs at the interface between materials with different band gaps, such as the cathode material and electrolyte in LIBs. During charging, lithium ions are inserted into the cathode, causing the Fermi level of the cathode to shift upward until it aligns with the conduction band minimum of the electrolyte, resulting in band bending.…”

“…Apart from the additive additions, the formation of an artificial CEI layer is an effective tool to promote enhanced electrochemical performances. 50 The artificial CEI offers a protective coating that helps adjust the interphase reaction and plays a dominant role in controlling lithium's charge transfer and diffusion. 103 Artificial CEI, like conventional CEI, isolates the direct contact of cathode from electrolyte, inhibits the side reactions, bestows crystal stability, and thus improves the overall electro-chemical performances.…”

A review of the degradation mechanisms of NCM cathodes and corresponding mitigation strategies

“…The effect of CEI growth on the capacity of the battery is thus detrimental. Surely, transition metal dissolution (related to LAM ageing mechanism) also contributes to the growth of CEI, as TM compounds (oxides and fluorides), can be a part of the CEI [124].…”