2019 年 87 巻 6 号 p. 357-364
It is known that the deterioration of LiNi0.5Co0.2Mn0.3O2 is suppressed by inhibiting direct contact between the cathodes and the electrolyte by surface coating. In order to evaluate the influence of the electrode/electrolyte interface degradation, it is necessary to eliminate the influence of particle cracking. In this study, LiNi0.5Co0.2Mn0.3O2 particles with a small size (500 nm to 1 µm) without crack formation after charge-discharge cycling were synthesized by a spray pyrolysis method. Hard X-ray photoelectron spectroscopy was used to investigate the structural changes of the cathode. It was revealed that the cathode coated with lithium boron oxide (LBO) by an antisolvent precipitation method had high durability against the surface structure changes by the reduction of transition metal ions. The formation and dissolution of NiO occurred in the uncoated sample during cycling, but the formation of NiO was suppressed in the LBO-coated sample. It was considered that the structural changes of the active material surface during cycling led to an increase in surface resistance of the uncoated sample, which is the main reason for the capacity fading of the spray pyrolyzed LiNi0.5Co0.2Mn0.3O2 cathode particles.