Revealing the unconventional lithium storage mechanism of ordered mesoporous NiO for lithium-ion batteries

Transition metal oxides have been intensively developed for use as anode materials to overcome the capacity limitations of commercial graphite. In this study, a highly ordered mesoporous NiO electrode material is fabricated using a hard templating method, and exhibits a reversible capacity of approximately 940 mAh g(-1) that is much higher than the theoretical value based on the conversion reaction (717 mAh g(-1)). Combined analyses that include synchrotron-based X-ray techniques and controlled X-ray photoelectron spectroscopies attribute the lithium storage behaviors to both the conversion reaction of NiO framework and the reversible electrolyte derived surface layer. Interestingly, the contribution of the reversible electrolyte-derived surface layer (-440 mAh g(-1)) to the capacity is comparable to that of the conversion reaction with NiO (-500 mAh g(-1)). The results also demonstrate that incomplete conversion occurs due to the high bonding energy of Ni-O in the framework during the electrochemical reaction, and prove that the distinctive nano-structural characteristics of the mesoporous NiO surface cause the reversible behavior of the electrolyte-derived surface layer.

Automated summary

In this study, a highly ordered mesoporous NiO electrode material with high reversible capacity is fabricated. The reversible capacity is attributed to both the conversion reaction of NiO framework and the reversible electrolyte derived surface layer.