Amorphous lithium carbonate as a superior lithium transport pathway in inorganic solid electrolyte interphases

Spatially uniform and facile lithium transport at the electrode-electrolyte interface is key to achieving cycle durability in lithium-ion batteries with high energy density. In this work, we investigate the lithium-ion transport properties and mechanisms within inorganic amorphous solid electrolyte interphase layers using a series of ab initio calculations. While amorphous Li₂O and Li₂CO₃ are found to exhibit excellent lithium transport properties compared to their defect-free crystalline counterparts, we find that the identified facile lithium transport in these amorphous phases stems from disordered oxygen environments around lithium, creating pervasive defect-like conditions that facilitate collective lithium transport. In particular, we demonstrate that amorphous Li₂CO₃ acts as a superior lithium transport material compared to amorphous Li₂O due to weaker Coulomb couplings between lithium and oxygen. We further demonstrate that lithium transport rates in amorphous Li₂CO₃ can be further enhanced, as lithium-rich compositions occur depending on battery operating conditions and oxygen coordination around lithium is reduced. Beyond confirming that amorphous inorganic solid electrolyte interphase materials facilitate lithium transport, our theoretical study demonstrates that amorphous Li₂CO₃ exhibits exceptionally high lithium transport properties. We elucidate the underlying scientific principles responsible for this superior performance in correlation with battery operating environments. The improved understanding offers valuable insights into how naturally formed or artificially generated passivation layers affect the performance of next-generation lithium-ion batteries.