Article ID: 25-00085
Designing positive electrode materials for Li-ion and Na-ion batteries without using expensive metals is of critical importance for sustainable energy storage systems. One of the most promising candidates, P3-type layered sodium manganese oxide (P3-NaxMnO2) can be obtained via solid-state reaction. While there is no report on P3-LixMnO2 synthesis and electrochemistry because of its instability, lithium ion exchange with Na in P3-NaxMnO2 is a plausible strategy to test its Li insertion/extraction. In this study, we investigate the electrochemical activity of P3-NaxMnO2 electrode in both Li and Na cells. We found that high capacity of ca. 200 mAh/g is achieved in both cells, and P3-NaxMnO2 electrodes undergo spontaneous Na/Li ion exchange in the Li+-containing electrolyte, which can thereafter be reversibly cycled. To improve electrochemical performance, we demonstrated two approaches: partial Ti or other metal substitution for Mn in P3-NaxMnO2 and using a highly concentrated electrolyte of 5.5 mol dm−3 Li(N(SO2F)2) dimethyl carbonate solution. Particularly, the highly concentrated Li-electrolyte provides a significant enhancement on the cycle stability in the Li cell, demonstrating no apparent capacity loss up to 100 cycles.
