Li<sup>+</sup>/Na<sup>+</sup> Ion Exchange in Layered Na<sub>2/3</sub>(Ni<sub>0.25</sub>Mn<sub>0.75</sub>)O<sub>2</sub>: A Simple and Fast Way to Synthesize O3/O2-Type Layered Oxides
Weibo Hua, Suning Wang, Kai Wang, Alexander Missyul, Qiang Fu, Mariyam Susana Dewi Darma, Hang Li, Volodymyr Baran, Laijun Liu, Christian Kübel, Joachim R. Binder, Michael Knapp, Helmut Ehrenberg, Sylvio Indris
Abstract
Normally, high temperatures are required for solid-state reactions to overcome energy barriers in the formation of lithium insertion materials. Consequently, conventional high-temperature lithiation reactions are very time- and energy-consuming and often accompanied by undesirable side reactions. Thus, how to synthesize Li-containing cathode materials with a desired structure under a short reaction time and low temperature is of paramount significance. Herein, layered sodium-deficient Na2/3□1/3(Ni0.25Mn0.75)O2 (□ for vacancy) oxides with different oxygen stackings (P2 or P3 structure) were deployed in lithium ion batteries. An interesting Li+/Na+ ion-exchange reaction between the electrode material and LiPF6-based carbonate electrolyte was observed at room temperature for the first time. Such a reaction can produce the layered Li2/3□1/3(Ni0.25Mn0.75)O2 compounds having the O2 or O3 structure, which show the ability to reversibly accommodate lithium ions over a relatively wide voltage range. Our experiments may open up a pathway toward the development of novel electrode materials.