Aluminum and fluorine co-doping for promotion of stability and safety of lithium-rich layered cathode material

Abstract Lithium-rich layered compound cathode materials recently attract ever-growing attention in lithium ion batteries for electric vehicles and energy storage devices due to their high discharge capacities of over 250 mAh g −1 and low cost. However, they still suffer from capacity fade, voltage decay and poor rate capability and thermal stability. In this paper, the Al&F co-doped Li 1.2 Ni 0.13 Co 0.13- x Mn 0.54 Al x O 2(1- y ) F 2 y cathode material has been successfully prepared via a co-precipitation reaction and a subsequent solid phase calcination. The resulting material combines the advantages of both Al-doping and F-doping, which can effectively mitigate the intrinsic layered-to-spinel phase transformation, and as a consequence, inhibits the capacity fade and voltage decay: delivering a discharge capacity of 217 mAh g −1 with retention of 88.21% and an average discharge voltage decay of 0.4019 V upon 150 cycling at 0.5 C. On the other side, with an increased electronic and ionic conductivity, this co-doping practice enhances the rate capability by a considerable extent that it delivers a discharge capacity of 157 mAh g −1 at 10 C, thus facilitating its application for quick charging devices. In addition, the thermal stability related with battery safety is significantly meliorated. Specifically, the co-doped cathode material exhibits an initial exothermal peak at a higher temperature of 273 °C and a much less overall heat generation of 221 J g −1 compared to the 210 °C and 755 J g −1 for the pristine one. In conclusion, the anion/cation co-substitution strategy has been demonstrated to be of great promise for the improvement of lithium-rich layered cathode materials.