Porous Li4Ti5O12-induced cathode electrolyte interphases enable sustainable single-crystalline NCM cathodes

Abstract

The cathode electrolyte interphase (CEI) layer derived on the cathode surface has a great influence on the coulombic efficiency, energy efficiency, rate performance, self-discharge, and cycling life of the lithium-ion batteries (LIBs). For layered nickel-rich cathodes, the electrochemically-inert residual lithium (e.g., Li2CO3, LiHCO3) combined with the continuous growth of CEI under high voltage (≥4.5 V vs Li/Li+) further increases the difficulty of regulating the activity and stability of LIBs. In this work, single-crystalline LiNi0.5Co0.2Mn0.3O2 (NCM523) is modified with porous Li4Ti5O12 particles through a simple solid synthesis process between residual lithium and metal–organic framework MIL-125(Ti). Here, metal–organic frameworks (MOFs) play an important role to thoroughly derive porous Li4Ti5O12 with a decentralized but not fully covered situation on the NCM523 surface. Moreover, Ti4+-rich Li4−xTi5O12−y would arise when the Li+ and O2– are removed from Li4Ti5O12 under a high voltage, which can promote the growth of cathode electrolyte interphase (CEI) along with enhanced capacity and stability of the NCM523 single crystals. Based on the MOFs materials, a new method of modifying cathodes with promoted CEI film was designed, which could be a reference for the development of high voltage and nickel-rich cathodes.