Effect of the PrPO4 modification on the structure and electrochemical performance of LiCoO2

Increasing interest in LiCoO 2 as a cathode material for Li-ion batteries has recently arisen due to its high operating voltage, high energy density and long cycle life. However, irreversible structural damage and severe side reactions at high cut-off voltages severely deteriorate the electrochemical performance of LiCoO 2 materials, resulting in a series of safety issues when used in batteries. In this work, PrPO 4 , Li 2 CO 3 and Co 3 O 4 are mixed and then treated at a high temperature to obtain PrPO 4 -modified LiCoO 2 with improved electrochemical performance at 4.55 V. XRD and Rietveld refinement results confirm that the modified LiCoO 2 materials exhibit well-ordered structures with compact unit cells. PrPO 4 is not incorporated into the crystal lattice of LiCoO 2 but converted by Li 2 O and Co 3 O 4 into PrCoO 3 and Li 3 PO 4 phases during the reaction. Additionally, these two phases are well-incorporated into the LiCoO 2 particle. Electrochemical tests indicate that the irreversible capacity during cycling is significantly reduced by PrPO 4 modification. Benefiting from the enhanced interface stability induced by Li 3 PO 4 and PrCoO 3 , the 1 mol% PrPO 4 -modified LiCoO 2 sample exhibits an initial discharge capacity of 185 mAhg −1 at 0.5C with a capacity retention of 92.4% after 100 cycles, as well as an excellent rate capability with a capacity of 128 mAhg −1 even at 5C.