Improvement of Reversibility and Cyclic Stability: A Monolithic Solid Electrolyte Interphase in SiOx-Based Anode for Lithium-Ion Batteries

SiOx is investigated as a promising anode material for lithium-ion batteries (LIBs) for replacing Si, which undergoes huge volume changes during lithiation/delithiation, even though its energy density is much higher than that of graphite. However, some critical issues such as cyclic instability and poor initial Coulombic efficiency (ICE) need to be resolved for practical applications. Various approaches have been explored to address these issues, such as the compositional modification of the conventional solid electrolyte interphase (SEI) formed on the outer surface of the electrode contacting the electrolyte; however, the improvement is limited to the initial several hundred cycles. In this work, we produced a monolithic SEI, which has highly favorable characteristics such as structural durability and diffusion efficiency of lithium ions, by in situ growth and interconnection of the passivation materials generated not only on the outer surface but also in the interstitial voids between the SiOx particles of the electrode. Compared with the electrode having the conventional SEI formed only on the outer surface of the electrode, the capacity retention improvement becomes more conspicuous with the cycles, with more than 27% improvement after 1500 cycles. In addition, the ICE significantly improved by more than two times.