Effect of a ZrO2 Coating on the Structure and Electrochemistry of LixCoO2 When Cycled to 4.5 V

TLDR: In this article, the authors showed that the lattice of coated LiCoO 2 expands and contracts in exactly the same way as uncoated Li x CoO 2 during charge and discharge.

Abstract: Recently, Cho et al. studied the effects of a ZrO 2 coating on the electrochemical behavior of Li/Li x CoO 2 cells. They found that the capacity retention to 4.4 V was significantly improved for cells having electrodes incorporating coated material compared to those with uncoated LiCoO 2 . They suggested that the thin coating suppressed the lattice expansion of Li x CoO 2 during cycling, leading to improved behavior. Our results on LiCoO 2 coated with ZrO 2 , reported here, confirm the improved cycling behavior. X-ray diffraction (XRD) patterns collected with long counting times show that the coated material is nanocrystalline ZrO 2 . In situ XRD results indicate that the lattice of coated Li x CoO 2 expands and contracts in exactly the same way as uncoated Li x CoO 2 during charge and discharge. These results prove that the ZrO 2 coating does not affect the lattice expansion of LiCoO 2 , in contrast to the results reported by Cho et al. We believe that the improved cycling behavior is caused by a reduction in the contact area between LiCoO 2 and electrolyte.