No abstract

The effect of bi-functional coatings consisting of Zr and phosphate (P) on the electrochemical performance of LiNiCoMnO (NCM) has been investigated. The presence of various types of Zr and P compounds such as oxides (ZrO and LiZrO) and phosphates (ZrPO, ZrPO and LiZr(PO)) in the coating was confirmed by experiments as well as density functional theory (DFT) calculations. When the NCM samples were coated with the Zr/P hybrid material, the cycle retention and the amount of removed Li residuals (LiOH, LiCO) were enhanced by the synergistic effect from Zr and P. The NCM sample coated with a Zr/P layer with a Zr/P ratio of 1 : 1 exhibited an increase in the initial capacity (209.3 mA h g) compared to the pristine sample (207.4 mA h g) at 0.1C, owing to the formation of the coating layer. The capacity retention of the Zr/P coated sample (92.4% at the 50th cycle) was also improved compared to that of the pristine NCM sample (90.6% at the 50th cycle). Moreover, the amount of Li residuals in the Zr/P coated NCM sample was greatly reduced from 3693 ppm (pristine NCM) to 2525 ppm (Zr/P = 5 : 5).

A water washing process can effectively reduce the presence of residual lithium with minimal effect on lithium‐ion battery cell performance. We investigated the effects of varying the amount of water used for washing and the temperature used to evaporate the water on Li1.00Ni0.80Co0.15Mn0.05O2. The residual lithium decreased and the cell performance deteriorated as the amount of water used for washing was increased from 0.7 to 5 times the amount of active material. The temperature at which the active material was dried after washing had a considerable effect on the reformation of the residual lithium layer after heat treatment. A ratio of water/active material of 1:1 and a drying temperature of 120 °C were selected as the optimal washing conditions, achieving a residual lithium content of less than 1000 ppm with minimum deterioration in cell performance; as a result of the treatment, the total volume of gas evolution was reduced by 25 %.