The Effect of Key Electronic States on Excess Lithium Intercalation in Li2RuyMn1-yO3

Excess reversible lithium storage is an alternative crucial strategy besides the expansion of redox centers to boost the capacity of layered cathodes. However, the mechanism of excess Li+ intercalation is far from being comprehended, indisputably hindering the development of layered cathodes. Herein, the comparative study of Li2RuyMn1-yO3 and Li2RuyTi1-yO3 by Xray absorption and photoemission spectroscopies attempts to illustrate the origin. The charge transfer from Ru to Mn through TM-O pi bonding interaction with the formation of O holes has been revealed in Li2RuyMn1-yO3, which originates from the inductive effect and the approaching energy level of Mn and Ru bands. The electronic state is thought to reduce the Coulomb repulsion of Li+ with the matrix, promoting excess Li+ intercalation. The results are instructive to the rational design of layered cathodes to achieve a larger reversible capacity in a wide voltage window.