Structural Studies on the Effects of ZrO[sub 2] Coating on LiCoO[sub 2] during Cycling Using In Situ X-Ray Diffraction Technique

The effects of -coating on the surface of have been studied using synchrotron-based in situ x-ray diffraction (XRD) technique. Although both -coated and uncoated showed capacity fading during high voltage cycling, the coated one showed better cycle performance. After observing capacity fade for both samples through 10 charge-discharge cycles, in situ XRD patterns were collected during the 11th charge with reduced current density. With reduced current density, both samples restored part of their lost capacity. However, in situ XRD data shows that the -coated sample has much better structural change behaviors than the uncoated . The partial restoration of the lost capacity and the recovered structural variations observed at reduced current density clearly indicates that the lost capacity is very closely related to the increased polarization, which is most likely due to the precipitation of the electrolyte decomposition products on the surface of cathode material. coating layer may provide some protection for the cathode surface and help to reduce the electrolyte decomposition at higher voltages.