Ultrathin Conductive CeO2 Coating for Significant Improvement in Electrochemical Performance of LiMn1.5Ni0.5O4 Cathode Materials

Abstract

LiMn1.5Ni0.5O4 (LMNO) has a huge potential for use as a cathode material in electric vehicular applications. However, it could face discharge capacity degradation with cycling at elevated temperatures due to attacks by hydrofluoric acid (HF) from the electrolyte, which could cause cationic dissolution. To overcome this barrier, we coated 3–5 micron sized LMNO particles with a ∼3 nm optimally thick and conductive CeO2 film prepared by atomic layer deposition (ALD). This provided optimal thickness for mass transfer resistance, species protection, and mitigation of cationic dissolution at elevated temperatures. After 1,000 cycles of charge-discharge between 3.5 V–5 V (vs. Li+/Li) at 55°C, the optimally coated sample, 50Ce (50 cycles of CeO2 ALD coated) had a capacity retention of ∼97.4%, when tested at a 1C rate, and a capacity retention of ∼83% at a 2C rate. This was compared to uncoated LMNO particles that had a capacity retention of only ∼82.7% at a 1C rate, and a capacity retention of ∼40.8% at a 2C rate.