Interfacial Reactivity of a High Capacity Manganese Rich (HCMRTM) Li-Ion Positive Electrode
HCMR™ materials surface structural changes were investigated during electrochemical cycling by confocal Raman microscopy in a custom-designed spectro-electrochemical cell. A carbon- and binder-free cathode was prepared by pressing the active material onto Al foil, which is then loaded into the spectro-electrochemical cell. Figure 1 shows Raman spectra collected during a first charge-discharge cycle. Surface structural changes due to the delithiation of the HCMR™ material are observed by the change in position of the Raman peaks during cycling.
While the oxidation of Ni2+ to Ni4+ appears to be a fully reversible process, other surface structural changes manifest themselves during the prolonged cycling (Figure 2). A shift of the major peak Mn-O band from 595 cm-1 to higher frequency, as well as an increase in intensity for another Mn-O mode at 650 cm-1 was observed.
Shifting from the Raman spectra indicates significant structural deviation of the HCMR™ material during cycling. The correlation of the structural changes with the observed interfacial phenomena will be discussed in regards to their influence on the electrode and cell electrochemical performance and lifetime.
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, under the Applied Battery Research for Transportation (ABR) Program and Award Number DE-EE0006443.
1. M. M. Thackeray, S. H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek and S. A. Hackney, J Mater Chem, 17, 3112 (2007).
2. Y. Li, M. Bettge, B. Polzin, Y. Zhu, M. Balasubramanian and D. P. Abraham, J. Electrochem. Soc., 160, A3006 (2013).
3. K. J. Carroll, D. Qian, C. Fell, S. Calvin, G. M. Veith, M. F. Chi, L. Baggetto and Y. S. Meng, Phys Chem Chem Phys, 15, 11128 (2013).