Application of Atomic Layer Deposition to Lithium-Oxygen Batteries

Abstract

Rechargeable lithium-oxygen (or lithium-air) batteries have been recognized as next-generation batteries which can replace the prevailing lithium-ion batteries. The non-aqueous Li-O2 batteries involve carbon materials as cathode materials due to their natural abundance and high surface areas per weight. However, the exposure of carbon to air and Li2O2 deteriorates the stability of cathodes, in association with the subsequent electrolyte decomposition, leading to the low round-trip efficiency and poor cycle performance. The atomic layer deposition (ALD) of oxide materials possesses several unique features: self-limiting surface reactions and atomic-scale deposition, and conformal deposition. Such features can be applied to control artificially the deposition morphology on the underlying carbon cathodes, which affects the performance of Li-O2 batteries. In order to improve the well-known issue present in the Li-O2 (Li-air) batteries, the ALD of oxide materials was combined with the carbon materials with the aim to controlling the cathode degradation issues. The current work reports zinc oxide and aluminum oxide as coating materials deposited onto carbon cathode materials, i.e. carbon nanotubes (CNTs): zinc oxide (ZnO) shows a semiconducting property, while aluminum oxide (Al2O3) exhibits an insulating property. The ALD-coated ZnO and Al2O3 onto the carbon electrodes are characterized using analytical electron microscopy. The implications of ALD-based ZnO and Al2O3 are discussed in terms of the performance of Li-O2 secondary batteries in connection with the underlying microstructure and chemistry.