Enhanced Performance of Lithium-Ion Batteries By Conductive ALD Thin Film Coating

Abstract

Surface modification has been widely considered as an effective strategy to boost cycle-life and enhance conductivity of electrode particles for lithium ion batteries (LIBs). Atomic layer deposition (ALD) is a layer-by-layer thin film coating technique. Through ALD, a conformal ultrathin coating with controllable thickness can provide initial protection for surface of active materials. Recently, we studied cerium dioxide (CeO2) and iron oxide as conductive coating materials for LIB application. Both CeO2 and iron oxide can significantly enhance the electrochemical performance of LIB electrode materials. For example, iron oxide films were coated on LiMn1.5Ni0.5O4 particles by ALD for the synergetic effect of performance enhancing by iron doping and conformal iron oxide film coating. With an optimal film thickness of ~0.6 nm, the initial capacity improved by 25% at room temperature and by ~26% at 55 °C at a 1C cycling rate. The synergy of doping of LiMn1.5Ni0.5O4 with Fe near surface combined with the conductive and protective nature of the optimal iron oxide film led to high capacity retention (~93% at room temperature and ~91% at 55 °C) even after 1,000 cycles at a 1C cycling rate.