Relationship between Particle Hardness of LiNi1/3Co1/3Mn1/3O2 and its Electrochemical Stability at High Temperature

Abstract

LiNi1/3Co1/3Mn1/3O2 was synthesized as a cathode material for lithium-ion batteries by coprecipitation and solid-state synthesis. The precursor prepared by coprecipitation was sintered at 950-1000 degrees C for 10-15 h under air. A cathode material annealed at 950 degrees C for 10 h (NMC950-10) has 81% capacity retention, whereas another cathode material at 1000 degrees C for 15 h (NMC1000-15) has 85% capacity retention at the 80th cycle at a 60 degrees C cycle test temperature. Cross-sectional images of pressed electrodes reveal that this difference results from different degrees of particle rupture. Image analysis shows that the percentages of particle rupture in NMC950-10 and NMC1000-15 were 44% and 20%, respectively. The measured particle hardness of the cathode material is quantitatively related to the number of ruptured particles in highly pressed electrodes. Therefore, the cathode material with higher particle hardness exhibits better cycle life performance in 60 degrees C cell tests.