Boosting the Electrochemical Performance of LiMnNiCoO by Atomic Layer-Deposited CeO Coating.

It has been demonstrated that atomic layer deposition (ALD) provides an initially safeguarding, uniform ultrathin film of controllable thickness for lithium-ion battery electrodes. In this work, CeO thin films were deposited to modify the surface of lithium-rich LiMnNiCoO (LRNMC) particles via ALD. The film thicknesses were measured by transmission electron microscopy. For electrochemical performance, ∼2.5 nm CeO film, deposited by 50 ALD cycles (50Ce), was found to have the optimal thickness. At a 1 C rate and 55 °C in a voltage range of 2.0-4.8 V, an initial capacity of 199 mAh/g was achieved, which was 8% higher than that of the uncoated (UC) LRNMC particles. Also, 60.2% of the initial capacity was retained after 400 cycles of charge-discharge, compared to 22% capacity retention of UC after only 180 cycles of charge-discharge. A robust kinetic of electrochemical reaction was found on the CeO-coated samples at 55 °C through electrochemical impedance spectroscopy. The conductivity of 50Ce was observed to be around 3 times higher than that of UC at 60-140 °C. The function of the CeO thin-film coating was interpreted as being to increase substrate conductivity and to block the dissolution of metal ions during the charge-discharge process.