Unraveling the effect of exposed facets on voltage decay and capacity fading of Li-rich layered oxides

In this work, the effect of exposed facets on voltage decay and capacity fading of Li-rich layered oxides (LLOs) is unraveled via two nanoplates which are prepared by very similar co-precipitated-precursor method. The top-bottom surface of one nanoplate is (101) facet (S101 sample, active plane) and the other is exposed (001) facet (S001 sample, inactive plane). Although 5101 sample delivers an excellent rate capability (149 mA h g(-1) at 2000 mA g(-1)), both its voltage and capacity decrease faster than 5001 sample. TEM, HRTEM, XPS and XRD of cycled samples demonstrate: (1) Large area of active surface will accelerate electrochemical corrosion and phase transformation of LLOs and (2) electrochemical corrosion and phase transformation of LLOs with large area of inactive surface can be mitigated, leading to slow voltage decay and capacity fading. In addition, we discover Co and Ni are easier to react with electrolyte than Mn. Therefore, suitable facets and compositions may be more useful for improving the electrochemical performance of LLOs. (C) 2017 Published by Elsevier B.V.