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Soft X-Ray Absorption Spectroscopic Study of a LiNi0.5Mn0.5O2 Cathode During Charge



W S. Yoon, Mahalingam Balasubramanian, Xiao-Qing Yang, Ziwen Fu, Daniel A. Fischer, James McBreen


Soft X-ray (200 eV to 1000 eV) absorption spectroscopy (XAS) at the O K-edge and the metal LII, III-edges, in both the fluorescence yield (FY) and the partial electron yield (PEY) mode, has been used to probe the electronic structure of electrochemically deintercalated Lil-xNi0.5MnO.5O2. FY and PEY spectra of the transition metal LII, III-edges, indicated that Mn ions remain mostly unchanged in the Mn4+ state at all levels of charge. However, the Ni FY L-edge spectra show a continuous shift to higher energy during charge, but remain mostly unchanged in the PEY data. The results of the FY data show that the Ni ions in the bulk are oxidized from Ni2+ to Ni4+ during charge. The difference between the surface sensitive PEY data and the bulk sensitive FY data indicates that the surface of Lil-xNiO.5MnO.5O2 has a different electronic structure than the bulk. The shift in the O K-edge to lower energies and the development of a shoulder on the low energy side of the first pre-edge peak indicates that the holes compensating the lithium ion deintercalation are located in O 2p states as well as Ni 3d states. These results show that soft x-ray absorption is a powerful technique to study the electronic structure of new battery materials and it provides unique complementary information to that obtained from hard x-ray (above 1000 eV) absorption studies at the transition metal K-edges.
Journal of the Electrochemical Society
No. 2


batteries, cathodes, lithium, NEXAFS, soft x-ray


Yoon, W. , Balasubramanian, M. , Yang, X. , Fu, Z. , Fischer, D. and McBreen, J. (2004), Soft X-Ray Absorption Spectroscopic Study of a LiNi<sub>0.5</sub>Mn<sub>0.5</sub>O<sub>2</sub> Cathode During Charge, Journal of the Electrochemical Society (Accessed April 20, 2024)
Created January 31, 2004, Updated October 12, 2021