Atomic Layer Deposited MgO: A Lower Overpotential Coating for Li[Ni0.5Mn0.3Co0.2]O2 Cathode.

An ultrathin MgO coating was synthesized via atomic layer deposition (ALD) to improve the surface properties of the Li[Ni0.5Mn0.3Co0.2]O2 (NMC) cathode. An in-situ quartz crystal sensor was used to monitor the "self-limiting" surface reactions during ALD process and estimate the density of the deposited film. The electrochemical performance of the MgO-coated NMC cathode was evaluated in a half-cell assembly and compared to other ALD-based coatings, such as Al2O3 and ZrO2. Cyclic voltammetry studies suggested that ALD MgO has a higher Li-diffusion coefficient which resulted in lower overpotential on the NMC cathode surface and improved Li-ion battery rate performance. MgO-coated NMC also yielded improved capacity retention over uncoated NMC in a long-range cycling test.