Atomic Layer Deposition on Alkali Transition Metal Oxides as Cathode Materials for Sodium Ion Batteries

The limited abundance of lithium drives research into an alternative battery to the commonly used lithium-ion batteries (LIBs). Sodium is highly available and inexpensive, while having an appropriate redox potential for application in a sodium ion battery (SIB). Layered transition metal oxides (LTMOs) are promising cathode materials for SIBs due to simple synthesis and high energy density. However, SIBs suffer from instability while cycling. A thin coating of aluminum oxide through atomic layer deposition (ALD) might improve the stability by suppressing the side reaction between the electrode and the electrolyte in the cell. Two LTMOs were coated with 0.5 nm of aluminum oxide. Electrochemical testing in sodium half-cells demonstrated improvement in capacity retention and coulombic efficiency as compared to the uncoated material, but with lower capacity and worse kinetics. ALD coated LTMO cathodes are an important area of future research to enable practical SIBs.