Addition of yttrium oxide as an effective way to enhance the cycling stability of LiCoO2 cathode material for Li-ion batteries

Lithium‑cobalt oxide (LiCoO2) is the first and still popular cathode material (LCO) used in Li-ion batteries. Its high theoretical capacity is a driving force to improve its properties in order to fully use its significant potential. In this paper the attempts of a partial substitution of Co3+ ions with Y3+ ions to synthesize yttrium-doped LiCoO2 cathode (0–15 mol% of Y) were described. The physicochemical characterization were conducted by ICP, TGA-MS, N2 physisorption, X-ray diffraction (PXRD) and scanning electron microscopy (SEM-EDS). All the prepared cathode materials exhibit well-layered structure and high crystallinity. Unexpectedly, yttrium ions did not substituted the Co3+ sites and were present in the form of a separate oxide phase. Yttrium oxide act as a modifier adversely affecting the initial capacity of the LCO cathode material. However, the galvanostatic cycling revealed that the yttrium oxide addition has a beneficial effect on the cycling stability and capacity retention of the LCO material, especially for the small content of Y3+ (5 mol%). The cycling of this electrode (100 cycles at 1C between 3.0 and 4.4 V vs. Li/Li+) was stable and constant, the loss of capacity was steady and the smallest among all the tested materials.