What Is Important? Effect of Primary and Secondary Particle Size

Abstract

High nickel layered oxides are attractive cathode materials that can achieve high energy density in lithium-ion batteries (LIBs). Many researchers have strived to improve the cycling stability and energy density of LiNiO2 (LNO) through another metal mixing, dopping, or coating method. However, the particle size effect of pure LNO during the charging/discharging system has not been fully understood yet. Many computing research results revealed that smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance and good cycling stability than bulk counterparts. However, our study revealed that the different particle size of LNO has a very different trend in contrast to the computation results because they overlooked the influence of primary particles. In this study, we focus on the impact of the particle size distribution of spherical cathode material on positive electrodes in LIBs. We designed four different particle sizes of Ni(OH)2 by controlling pH, time, and agitation speed. When the other conditions were the same except for the particle size, we were able to explore how the grain size, Li off-stoichiometry (Li1-zNi1+zO2), and activation energy affect the battery performance. Through size comparison, a better understanding of the influence of particle size distribution was obtained, which would be an important basis to engineer electrodes for higher C-rate capability, higher performance, and better stability during battery cycling.