Capacity-controllable Li-rich cathode materials for lithium-ion batteries

In this study, we report a new type of Li-rich layered-spinel materials with a general composition formula of xLi(2)[Mn0.857Co0.143]O-3-(1 - x)Li[Mn1.714Co0.286]O-4 (x=0.95, 0.85, 0.75, and 0.65) for use as cathode materials in Li-ion batteries. These materials exhibit steadily increased specific capacities upon cycling for up to several dozen of cycles, depending on the charge-discharge potential windows. Various characterizations reveal that the specific capacity increase is due to the gradual activation of the initial Li-rich layered phase from the surface of the composite particles. Both experimental and computational results suggest that small amount of Co dopants plays a critical role in the continuous activation process of these materials and the structural evaluation mechanism is also discussed. Based on this unique feature, controllable discharge capacities of these cathode materials can be achieved in a broad range from 30 to 240 mA h g(-1) by deliberately activating the materials at a potential window of 2-4.8 V. (C) 2014 Elsevier Ltd. All rights reserved.